RANS S-7S Courier: Randy Schlitter and the Gang Continue to Push and Prod, Tweak and Improve This Utility Airplane; by Marc Cook

KITPLANES

An Inside Look at How Flight Reviews Are Done JULY 2012

RANS ® YOUR HOMEBUILT AIRCRAFT AUTHORITY S-7S Flight Review • Whirl Wind’s

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Trying Out Whirl Wind’s New Blade

July 2012 | Volume 29, Number 7 Flight Reports 8 RANS S-7S Courier: Randy Schlitter and the gang continue to push and prod, tweak and improve this utility airplane; by Marc Cook. Builder Spotlight 18 Switch Blade: There’s a lot to like about Whirl Wind’s new scimitar prop blade for the Rotax; by Tom Wilson. 24i F rewall Forward: Choosing a Prop for Your Project: In a discussion of aero engines, there’s always 56 time to talk prop; by Dave Prizio. 42 Unusual Attitude: Considerations when installing an alternative engine; by Patrick Panzera. 45 Build It Better: Where’s your margin? By Paul Dye. 48 Maintenance Matters: Cable classroom; by Steve Ells. 52 Completions: Builders share their successes. 53 w do n to Earth: Just about every kit aircraft is custom; by Amy Laboda. 65 Free Flight: Anatomy of a modification; by Paul Dye. 74 Ask the DAR: Part 103, LSA and flight-test areas; by Mel Asberry.

Shop Talk 78 aero ’lectricS: The LED strip club, part 2; by Jim Weir. Designer’s Notebook 75 Wind TunneL: A look at ducted fans; by Barnaby Wainfan. Exploring 2 editor’s Log: Show season; by Mary Bernard. 5 what’s NeW: MGL’s small V6 com radio and the HXr EFIS from Grand Rapids Technologies; edited by Suzanne B. Bopp. 6 viewfindeR: Clarity on airworthiness directives for homebuilts? By Marc Cook. 32 homebuilding Tools: A conceptual approach to 8 building looks beyond mere physical tools; by Terry Edwards. 36 iNSide KITPLANES®: Flight Review Procedures It’s a lot more than kick the tires and light the fires; by Marc Cook. 56 Alternative Energies: Solar-powered AC: big, slow and expensive; by Dean Sigler. 62 light Stuff: Leveraging your fun; by Roy Beisswenger. Kit Bits 4 Letters 68 list of Advertisers 69 Builders’ Marketplace 80 kit StufF: Drawing on experience; by cartoonist Robrucha. 18 On the cover: Richard VanderMeulen photographed the RANS S-7S in Lakeland, Florida.

KITPLANES July 2012 1 Editor’s log Show season. And so it begins. It’s been just a week with 8.4- (AF-5500) or 10.4-inch (AF-5600) though the hangars were bustling in the and a half since we returned from a visit high-resolution LCD displays. Knobs that afternoon. Some major players such as to Florida for the Sun ’n Fun fly-in, where function as buttons help eliminate the Cirrus were noticeably absent. The LSA the weather cooperated gloriously. need for menus used in other EFISes. and ultralight areas were sparsely popu- During the week we watched Dick • JP Instruments showed its new lated, and there was talk that the LSA VanGrunsven studying the cockpit of his EDM-900 engine analyzer, whose small Mall, ultralight and rotorcraft areas might first homebuilt, the RV-1, to determine size and VGA display make it a nice choice be combined next year. Aerotrek’s Rob whether he would fit into it decades for panel-space-challenged homebuilts. Rollison had a wonderful idea about a after the plane was originally built. By the The full-featured single-engine primary “panther path” that would wind through time Friday rolled around, the Friends of instrument has a rectangular face but fits the RV-1 team were pretty certain they’d in a 3-inch round hole. come up with a way to make this hap- • Corbi Air’s Alto LSA out of the Czech pen. But seeing VanGrunsven ponder Republic was on display at the LSA the problem each day was a testament to Mall. The company claims it is the first his sustained interest in even the earliest LSA with air conditioning, which adds of his designs. about 22 pounds to the weight without I’ll offer a few other tidbits from the an alternator and 35 pounds with one. show that we hope to learn more about The AC unit will also be sold separately. in coming months: The Alto can be built from a kit, and the • The Progressive Aerodyne group anticipated price is $45,000 to $50,000. had a folding-wing version of its kitbuilt • Marc Ausman of Vertical Power SeaRey amphibian that was being road- exhibited his remarkable new VP-400 tested to see if it would hold up well backup EFIS that can fly the airplane to under the pressures of trailering. If it the best runway in an emergency situa- Dick VanGrunsven inspects the restored does, this option may make an appealing tion. It is being included in the panels of RV-1 with great intensity. design even more so. some Lancair Evolutions, among others. • Garmin had announced its new • World Aircraft Company displayed the trees (providing shade) and link the navaid Pilot app for tablets and smart its new Vision/Sentinel aircraft, which main show grounds with the outlying phones just before the show, and offered are one and the same except the exhibits, offering a variety of vendor a demo of its crisp and straightforward Vision is intended for the kit market, wares and refreshments along the way. trip planning, weather and e-flight bag and the Sentinel will be outfitted for Still, it’s quality not quantity that ven- capabilities. Company reps said they are government/law enforcement work. dors heed, and we heard from more than working on a number of new things for WAC also plans to introduce a low- one kit manufacturer that they had sold Oshkosh, but would not elaborate. wing design at Oshkosh. airplanes at the show. The feeling among • Glasair Aviation’s Mikael Via said the • Velocity’s intriguing V-Twin was on some we spoke with was that despite the company is now using the Advanced hand, having accumulated a few hours competition in our arena, we’re all in this Flight Systems 5000-series EFIS in its before arriving. One of its more visible together, and the goal should be to grow Sportsman panels, and the new units features, beyond the twin engines, is a the homebuilt community so that the ris- were displayed at AFS’s booth. The design large and distinctive tail. ing tide will…well, you know. Sounds like combines high-speed microprocessing Overall, SNF seemed lightly attended, a good idea to me. J

The product of two parents with Lockheed Aerospace careers, Mary grew up with aviation, prompting her to pursue pilot training as an adult. Her father, a talented tool-and-die maker and planner, instilled in her an abiding interest in how things are built. For more than a decade, Mary Bernard she has been a contributing writer and Managing Editor for KITPLANES®.

2 KITPLANES July 2012 Photo: Mary Bernard It does more than you’d ever imagine, for less than you might expect.

Yes, there are other glass options out there. But the fact is, only Garmin G3X™ can give you this much capability, redundancy and cockpit integration for anything close to its new lower price. With single-display systems priced as low as $5,995, G3X now fits comfortably into even more experimental/ kitplane and light sport (LSA) avionics budgets. The package features Garmin’s SVX™ synthetic vision – now enhanced with standard 3-D “pathways” flight route guidance. Up to three of the 7-inch G3X glass displays can be combined to create a full reversionary PFD/MFD suite with built-in GPS receiver, ADAHRS reference, terrain/obstacles alerting, advanced autopilot integration1, and pre-loaded FliteCharts® and SafeTaxi® that come with built-in geo-referencing capability. There’s also support for optional TIS traffic alerting, engine instrument system (EIS) monitoring, and built-in XM WX™ satellite weather2 with NEXRAD. Compare and you’ll see: Anybody can put glass in your panel. But for the clearest view of the future, look to the Garmin G3X.

13870 G3X Dual Display Ad-Kitplanes.indd 1 4/11/12 12:59 PM EDITORIAL Editor Mary Bernard [email protected] Perils of PIO those of a single-seat aircraft, then it Associate Editor Suzanne B. Bopp is not surprising that a PIO can be set Editor at Large Marc Cook I must take exception to the statement, Senior Editor Paul Dye “The BD-5 suffered from a PIO prob- up, especially when he retracts the Art Direction Dan Maher landing gear for the first time. Again, Contributing Editors Chuck Berthe, Roy Beisswenger, lem, potentially worsened by sensitive Stein Bruch, Paul Dye, controls” in the March 2012 Wind not a design fault, but rather the pilot Steve Ells, Ed Kolano, Tunnel article “Failure to launch.” This not being aware that when he pulls the Amy Laboda, Rick Lindstrom Dave Martin, Paul Nafziger, is one of the myths and misconceptions landing-gear handle toward him, the Dave Prizio, Dick Starks, about the BD-5 and is simply not true. natural tendency is to counter the force Barnaby Wainfan, Jim Weir of the left hand by bracing and pushing Webmaster Omar Filipovic Dave Martin, past editor of Cartoonist Robrucha KITPLANES® magazine, said in the forward with the right hand on the article “The BD-5 Lives” in January control stick. ADVERTISING Sr. Advertising Manager Chuck Preston 1986, “Most of us who flew the BD-5 This will set up a PIO. We instruct 805/382-3363 (this writer included) recognized the any new BD-5 pilot about how to pre- [email protected] technical achievement of the airplane. vent this potential situation during our BUSINESS OFFICE The BD-5 was fast and highly maneu- preflight briefings. The videos of our Belvoir Media Group, LLC new FLS Microjet at www.bd-micro.com 800 Connecticut Avenue verable, surprisingly stable: light and Norwalk, CT 06854 extremely responsive without being and www.flsmicrojet.com show not a hint overly sensitive. That is a difficult -bal of PIO tendencies during takeoff. EDITORIAL OFFICE P.O. Box 315 ance to achieve. I liked the handling a Skeeter Karnes Ashland, OR 97520 lot.” Has Barnaby Wainfan ever flown BD-Micro Technologies, Inc. 619/677-6526 a BD-5? CIRCULATION There have been past instances of PIO Good Enough? Circulation Manager Laura McMann in the BD-5, but none attributed to a This article [April 2012, Free Flight] SUBSCRIPTION DEPARTMENT design feature. Like any aircraft design, reminded me very much of the late Colin 800/622-1065 as Ron Wanttaja points out in his articles Chapman, who started and ran Lotus www.kitplanes.com/cs P.O. Box 8535, Big Sandy, TX 75755-8535 about aircraft safety, if it is not properly cars and the racing team that was so For Canada: Box 7820 STN Main, London, ON N5Y5W1 built or flown by a qualified pilot, then successful and innovative in Formula 1 the potential for a crash increases. In our racing. His design precept was always, BACK ISSUES P.O. Box 22251 years of experience with the BD-5 some “Simplify and add lightness.” And he was Beachwood, OH 44122-2251 potential problems that could lead to known to comment that the perfect race 800/571-1555 www.kitplanes.com/backissues PIO are: CG not properly done (the first car design would fall apart 10 feet past fatality was due to a faulty CG), pitch the finish line of the race. REPRINTS FOR PUBLICATION controls not rigged properly, horizontal Anything else was over design and, AND WEB POSTING AVAILABLE Minimum Order: 500 stabilator not properly balanced, non- most likely, heavier than it needed to be, Contact Jennifer Jimolka, 203/857-3144 jig drilled wing with a poorly shaped and he knew that weight was the enemy leading edge (this can drastically alter of performance. His designs were some- the airflow characteristics of a laminar times fragile, but they were always fast! Change of address? Missing issue? airfoil wing and result in unpredict- And then there was the Lotus Subscription Question? able stall characteristics), overweight, mechanic I knew who made the com-

Visit www.kitplanes.com/cs. improper takeoff trim setting, etc. ment that, “If you can’t bend it with Or call 800/622-1065 The other major factor is the pilot. pump pliers, it is not a genuine Lotus from the U.S. and Canada. If the pilot is not properly briefed on part. It is too heavy!” Foreign 903/636-1112 or fax the handling characteristics, especially Steve Dorr J 203/857-3100.

Back Issues: Call 800/571-1555 Web site Information: General homebuilt aircraft information, back issue availability, online directories ordering info, plus a Kitplanes® article index and selected articles can be found at www.kitplanes.com. Unsolicited manuscripts: Are welcome on an exclusive basis, but none can be acknowledged or returned unless accompanied by a stamped, self-addressed envelope. No responsibility is assumed for loss or damage to unsolicited material. Kitplanes® (ISSN 0891-1851) is published monthly by Aviation Publishing Group, LLC, an affiliate of Belvoir Publications, 800 Connecticut Avenue, Norwalk, CT 06854-1631, Robert Englander, Chairman and CEO; Timothy H. Cole, Exec. Vice Pres./ Editorial Director; Philip L. Penny, COO; Greg King, Exec. Vice Pres./Marketing Dir.; Ron Goldberg, CFO; Tom Canfield, Vice Pres., Circulation. Periodicals postage paid at Norwalk, CT, and at additional mailing offices. Copyright ©2012 Aviation Publishing Group, LLC. All rights reserved. Reproduction in whole or in part is strictly prohibited. Printed in USA. Revenue Canada GST Account #128044658. Canada Publishing Agreement #40016479. Subscriptions: One year (12 issues) is $29.95 U.S. $41.95 in U.S. funds in Canada, includes GST. $41.95 in U.S. funds for Foreign Surface Mail or $57.95 in U.S. funds for Foreign Air Mail. Single copy price $4.99 U.S., $5.99 Canadian. POSTMASTER: Please send address changes and subscription inquiries to: Kitplanes®, P.O. Box 8535, Big Sandy, TX 75755-8535, or call 800/622-1065. Kitplanes® is a registered trademark of Aviation Publishing Group, LLC.

4 KITPLANES July 2012 www.kitplanes.com gain-adjusting device) settings for each mic in a four-place aircraft. • A weight of 8.8 ounces. MGL Avionics has announced avail- • Digital interface with which you can ability of its new V6 Com radio. The set the frequency on the radio from any V6 is a small 2.25-inch com radio (it MGL EFIS or any equipment capable of fits in a round instrument panel hole) setting frequency on an SL40 radio. for the Experimental and LSA mar- • Sunlight-readable LCD display. ket. It features 6-watt transmit power • 100 channels with alpha-numeric at low power consumption, full stereo frequency name and function (when the VOGAD intercom for up to a four- radio is operated in channel mode). place aircraft, Pilot Isolate modes, • Dual scan priority on active using and for the first time on an MGL com single transceiver. radio, standard rotary knobs for fre- • SL30 and SL40 communications quency and volume selection that Other features include: compatible with MGL extensions to allow tuning in big steps when the • Stereo intercom for stereo music lis- enable full remote control of entire knob is turned quickly or in 25-kHz tening when a music player is connect- transceiver with status feedback. steps when turned slowly. ed to the aux audio input. Music mutes • Digital audio subsystem for sound The V6 will operate on both 12- automatically on receive/transmit. Two quality. and 24-volt systems. And like its older mono inputs are for EFIS alarm anun- The price is $1095. For more informa- sibling, the V10 Com, the V6 can be ciators and phone connection. tion, call 877/835-9464, or visit www. remote controlled via an EFIS for fre- • Four microphone channels for inde- mglavionics.com. Find a direct link at quency selection. pendent level/VOGAD (voice-operated www.kitplanes.com.

Grand Rapids Technologies recently introduced its 10.4- inch HXr EFIS, which is designed to allow the use of an Android phone or tablet that can function as a second display. A moving map is standard and includes nearest weath- Strike Finder interface, five or eight serial ports (depend- er frequencies, range and bearing to a fix, etc. The 10.4-inch ing on the model) and one or two USB ports (depending screen brings a 60% wider field of view compared to previ- on the model). ous EFIS screens, allowing for greater awareness of terrain, There is no charge for standard Android interface and app. runways and nearby traffic. The Android phone or tablet must be purchased separately. Other features include dedicated serial channels for The limited-time introductory system price for the 10.4- AHRS (attitude/heading reference system) communica- inch HXr (includes four-cylinder engine monitoring, moving tion along with triple serial outputs from AHRS, synthetic map, AHRS, display unit and Android interface) is $6995. The approach that couples to the autopilot standard on all mod- introductory price for an additional 10.4-inch display unit is els, flight director that combines lateral and vertical steer- $3600, and a second AHRS is $1000. ing, demo recording to capture incoming data, XM weather For more information, call 616/245-7700, or visit www. radar, ADS-B weather and traffic, TIS traffic datalink, grtavionics.com. Find a direct link at www.kitplanes.com. J

To submit a press release on a homebuilt-related product, email a detailed description and high-resolution photograph to [email protected]. Mailing address is KITPLANES®, New Products, P.O. Box 315, Ashland, OR 97520. Your submission may be used in print or online at www.kitplanes.com.

KITPLANES July 2012 5 viewfinder Clarity on airworthiness directives for homebuilts? The FAA finally got around to pro- keyed to the make/model/serial number overall AD regardless of the lack of a TC viding guidance on airworthiness direc- of TC’d aircraft. for the aircraft. tive applicability to homebuilt aircraft, Such ambiguity has led to build- It’s a sticky situation both ways. First, updating a document last touched in ers facing difficult questions during some builders were convinced that ADs 1995. An updated advisory circular (39- the initial inspection for the airworthi- didn’t apply at all, leading them to ignore 7D) was published in March that suppos- ness certificate. Those taking a strict such things as the long-known AD on edly puts to rest a smoldering question interpretation of the rules claimed that Lycoming oil pumps or the troubles with among builders: Do airworthiness direc- even an AD-affected part was not an aftermarket cylinder assemblies. Second, tives published by the FAA have any issue because homebuilts have no TCs, when builders felt that an AD did apply bearing on homebuilt aircraft? and therefore the AD could not apply. to homebuilts, they sometimes faced an Previously at issue was language in Accordingly, local guidance from Flight uphill battle getting the part manufac- the ADs themselves that referred to parts Standards District Offices (FSDOs), Man- turer responsible for the problem to offer going into type-certificated aircraft. Such ufacturing Inspection District Offices redress. I’ve heard of those who experi- exclusionary verbiage led many, actually (MIDOs) and local Designated Airwor- enced a catch-22 regarding this issue: most, to assume that ADs simply didn’t thiness Representatives (DARs) grew The manufacturer of the part wants the apply to Experimental-registered air- like weeds. Some localities agreed with part out of circulation regardless of what craft. Because there is no Type Certificate the strict (and non-restrictive) interpre- kind of airplane it’s in, but won’t accom- (TC) involved with a homebuilt, there is tation, while others made up piecemeal modate the homebuilt crowd with the no way an AD can apply. This issue was exceptions. For example, some exam- same kind of warranty coverage because further muddied by the way ADs for iners wanted to know if specific com- homebuilts aren’t subject to ADs. In my parts on engines, as an example, were ponents in an engine were part of an view, that’s gaming the system.

So, What’s Changed? The FAA didn’t make sweeping altera- tions to the AC. Of note is this paragraph: “Unless stated otherwise (see subpara- graph 9b of this AC), ADs only apply to type-certificated (TC) aircraft, including ADs issued for an engine, propeller, and appliance,” says the new AC. Paragraph 9b says, in part, “Non-TC’d aircraft (e.g., amateur-built aircraft, experimental exhibition) are aircraft for which the FAA has not issued a TC under part 21. The AD applicability statement will identify if the AD applies to non-TC’d aircraft or engines, propellers, and appliances installed thereon.” Does this engine have any outstanding airworthiness directives against it? Even with new I asked our resident DAR, Mel Asberry, guidance from the FAA, your DAR may still care. about the new AC. “Remember that ACs

Former KITPLANES® Editor-in-Chief Marc Cook has been in aviation journalism for 22 years and in magazine work for more than 25. He is a 4500-hour instrument-rated, multi-engine pilot with experience in nearly 150 types. He’s completed two kit aircraft, an Aero Designs Pulsar XP Marc Cook and a GlaStar Sportsman 2+2.

6 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes aren’t rules,” he said. “They’re guidance, but not rules. They carry no power. So in that way, I don’t see this new AC making a lot of difference. The problem is that we had a lot of local FSDOs coming up with interpretations of the actual rule. I’m sorry, but just because a FSDO’s boss says something is one way, that doesn’t make it so. The rule makes it so.” Even with slightly clarified guidance, there will still be interpretations.

The Real World In a perfect world, we would never run engines or accessories that have untended ADs applied to them. After all, an AD is issued when there are signifi- A slow start for Sun ‘n Fun on Sunday morning. While the number of people on the cant problems found in the field—crack- grounds appeared to be fewer than last year, vendors were relatively happy. ing cylinders, defective manufacturing, poor assembly and other issues that As a matter of course, I would look corner. Work is harder to get and tougher could lead to significant damage or risk carefully at every AD that applied to than ever to keep. Management and of power loss. If an AD were to arrive on parts on my airplane. I would also make a other sectors where a guy could hope to a part I owned, I would comply with it. point to stay in close contact with manu- make a decent living—decent enough to “That [oil pump] doesn’t know if it’s in facturers of non-certified parts on the live modestly but even remotely consider a Cherokee or an RV,” Asberry said, and airplane. Just because an Experimental- building and owning an airplane—have he’s right. only parts maker doesn’t have to issue been hard hit. Outsourcing has made But it’s a bit murkier when you drill ADs, this doesn’t mean they aren’t war- so many of these jobs just go away, and down to the ways you can comply with ranted—watch notices such as service those that remain don’t pay what they the AD. Some have very specific reme- bulletins like a hawk. used to, as companies squeeze expenses dies—replace such-and-such part before from every corner of the empire. On top XX hours—while others can have AMOCs Where’s the Middleman? of that are rapidly increasing costs— applied; that would be alternate means of Walking Sun ’n Fun this year, I had a rare especially the one we see the most compliance. But what if, as the builder and salient thought. The vendors are saying prominently, fuel. In 2008, when fuel manufacturer of your airplane, you come that while overall foot traffic is down, prices skyrocketed and I was out at the up with an “alternate means” that’s not the sales of most things—big and small airport ever day, the decrease in flying covered or approved by the FAA? Does ticket alike—were doing just fine. (In traffic was plain to see and hear. What your solution carry the same weight? For fact, a couple of vendors told me that used to be a constant buzz of light traffic that matter, can the parts manufacturer they were having an excellent show and soon became the occasional Pilatus land- foist a different remedy on you because that overall, they were looking to have a ing or the poor, overworked Piper Semi- that part is going into a homebuilt? Tradi- good year.) They also said the number nole doing multi-engine training. For a tionally the answer has been yes. You, the of “tire kickers” was way down. Finally, it time, the average guy continued to come manufacturer, can determine the proper was clear that the bulk of the visitors on to the airport over the weekend, if only remedies, and once those have been the last two days of the show, Saturday to shine the airplane and contemplate a applied, you make the determination and Sunday, were casual at best—there short local flight. Then I stopped seeing that the airplane is airworthy. The new AC for the airshow attractions and not to him. He wasn’t in Lakeland, either. changes none of that. choose a new EFIS. What will bring him back is anyone’s What the new AC is likely to do is open So, where’s the guy in the middle? guess. I think his quality of life has to the possibility that ADs will be specifi- Not the wealthy enthusiast who can just improve—the job needs to seem more cally targeted at homebuilts. Now the write the check, but the potential builder secure, for example—but I also think language is there to call out, say, all who would love to be part of the sport, he has to see value in building and fly- Lycoming IO-360 engines in a certain the one who has to work hard to make ing. Fix one, and the other will follow. serial-number range or certain parts the investment. Where is he? It’s good to know that the survivors in regardless of where they are installed. I think he’s simply staying home. My aviation have trimmed and hunkered As I read the AC, such ADs would apply theory is this: Today’s middle class is down, seemingly ready to wait for this to your homebuilt. under increasing pressure from every customer’s return. J

Photos: Marc Cook KITPLANES July 2012 7 8 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes Randy Schlitter and the gang continue to push and prod, tweak and improve this utility airplane. By Marc Cook

Media relations in the homebuilt- with new surfaces. Ball bearings sup- aircraft industry is a funny thing. Some port the ailerons, and the surfaces companies would like you to know themselves now have a prominent bull when they’ve changed from AT&T to nose that helps reduce stick forces. The Verizon or that their new distributor in concept is simple. As the trailing edge East Nowhereistan can now take orders. rises, the extended leading edge drops And some—most, actually—just go below the wing’s lower surface and about their business, churning out kits, gains the benefit of an aerodynamic Previous S-7S panels have this forward steadily improving the product, making counterbalance. This force, ahead of tilt at the top, but RANS has introduced a less stretch into more where develop- the hinge line, helps drive the trailing new vertical panel. ment resources are concerned. It’s hard edge further up—or at least reduces to know when something is new. the effort required to hold it there. In it could be used as a trainer for RANS’s Like the time I walked under the flight, these new ailerons are transfor- single-seat models. Schlitter intention- wing of the RANS S-7S and almost mative—the S-7S has never handled ally built the cockpit to emulate the pranged my forehead on the aileron better—and, as good news for owners solo machines. In time, the S-7 created spades. It was a pleasant surprise, then, of already built 7s, the ailerons can be a niche of its own as a pert, clean utility to duck under the latest version of the retrofitted for around $1200. design that may share some of the vener- S-7S (actually an LS, more on that able Cub’s layout but tries to evoke none later) at this year’s Sebring LSA show A Long Line of Revisions of its nostalgia. and see the spades had been removed. Tweaking the ailerons is just another in Over time, the S-7 evolved. There Their exit indicates the biggest single a long line of development steps designer are short- and long-fuselage models in change in the 2012-model S-7S: a Randy Schlitter has provided in the S-7 its history, with the switch-over taking heavily revised aileron-control system Courier, an airplane originated so that place in the mid-1990s. The stretch is

Photos: Richard VanderMeulen KITPLANES July 2012 9 RANS S-7S Courier continued

21 inches aft of the cockpit, which helps with stability. “It added 11 pounds to the empty weight,” says Schlitter of the stretch, “but I wanted to do it for our certification program. I knew the longer fuselage would improve stability.” That certification program was to make the S-7 a Primary Category aircraft; the category, launched in the early 1990s, carried the hopes of a simplified certification process. That effort failed to gain traction, in part because the certification process was still cumbersome. By contrast, getting Two comfy chairs, one in front of the other, provide a comfortable perch for sightseeing. a design approved under the ASTM consensus standards is much easier, is with the current S-7S kit. And in this to RANS, this raised limit applies to the which explains all the new airframe case, we have the driving forces of Light S-7S, some S-7s and the Sport Wing S-6. manufacturers since 2004. Sport Aircraft rules pushing updates. Some of that newfound capacity can RANS also gradually phased in aero- One example: The S-7S can be built with go into fuel. With the latest version of dynamically balanced tail controls, first a carbon-fiber cowling, wingtips, spinner the S-7S, RANS has bumped total fuel the elevator and then the rudder. Finally, and boot cowl (that’s the rigid section capacity from 18 to 26 gallons in roto- in this much-abbreviated model history, behind the removable cowling that sur- molded plastic tanks. These tanks slip came the S models, which had a deeper, rounds the fuselage cage and supports into the wing from the root end. The dif- wider firewall, a new cowling, and a host of the windshield), saving about 15 pounds ference with the new tank is that it more other structural and convenience updates. in empty weight. Any pound you can closely follows the contour of the airfoil; An LS, in today’s terminology, is simply a save when the maximum weight is set by it doesn’t have to penetrate much farther S-7S built by the factory as an SLSA. decree benefits useful load. On that front, into the wingspan (from the root side) RANS has also bumped the maximum- to accommodate the extra fuel. Actually Continuous Improvement gross weight of the S-7S to 1320 pounds, lighter than the old tanks, the new high- As Schlitter says, “I like to keep improv- the LSA-legal maximum, a gain of 20 capacity models use the same sight gauges ing the designs. I have lots of ideas.” So it pounds from the old gross. According at the root and have the same fitting

You might miss the details on the S-7S’s constant-chord wing, but the absence of aileron spades tells you this is the latest version, a sweet-handling delight.

10 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes KITPLANES July 2012 11 RANS S-7S Courier continued locations as the smaller tanks. Schlitter, when asked why the airplane didn’t have the fuel capacity before if the space was available, said, “Heck, we thought 18 gallons was plenty of fuel! But the builders want more, and we were able to give it to them.” Also new with the greater tank- age are flush fuel caps. Even with the new tanks full, you still have 436 pounds for the cabin—based on the typical empty weight of 732 pounds. Structure, Systems, Synergy The S-7S carries classic RANS design features. Chrome-moly steel tubes make up the fuselage structure, while Optional carbon-fiber wingtips shod with simple LED strobe/navigation lights keep the the wings use tubular spars and (now) S-7S straightforward, light and modern. fully CNC-machined, one-piece ribs. These replace the multi-piece assembled airfoil, the wing has little twist or wash- the sides, but it complicates life in this ribs used before; they’re simpler, lighter out—the typical twisting of the wing so new world of all-glass panels. So now the and stronger. This structure supports that the outboard sections have a lower company will offer a vertical panel in all conventional fabric. That airfoil started angle of attack than the inboard sec- current S-7LS SLSA models and S-7S out as a NACA 2412 but was modified tions. This trick ensures that the roots kits. (The S-7LS photographed for this by Schlitter to have a slight bulge on the stall first, preserving roll control in stall story was built before the vertical panel bottom surface, only 3/8 inch tall, cen- and near-stall conditions. became standard.) tered at about mid-chord. You might RANS builders have become accus- In other respects, the S-7S is a fairly almost think it’s a Cub-style flat-bot- tomed to tweaking their instrument conventional tandem-seat taildragger. tom airfoil if you didn’t look carefully. panels and instrument placement to Curved sticks come up from the spine for Schlitter felt the cambered lower surface accommodate the forward tilt of the both front and rear pilots—solo is from gave better handling and reduced drag. traditional S-7 panel. The tilt exists to the front—and there are conventional As a result of the docile nature of the improve visibility over the nose and to toe brakes front and rear. Both seats slide

Over time, the S-7’s tail has seen updates—including being mounted on a longer tailboom—all in the name of improved stability and utility. Both rudder and elevator are mass and aerodynamically balanced. A full-width electric trimtab is on the other elevator.

12 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes Behind the cowl lives the ever-popular Rotax 912S. on tracks to make pilots of all sizes happy. These adjustments have to be done on the ground; they’re not in-flight acces- sible. The S-7S is meant to be flown right hand on the stick, so the throttle lever is on the left sidewall, the other engine controls on the left side of the panel and the flap handle down on the left-side cockpit floor, just below your knee. Taking Flight As mentioned, I caught up with the latest S-7S at Sebring in January. Demo pilot Jana Morenz walked me through the abbreviated start-up procedure. It’s typical Rotax 912: a bit of choke to get it started then a minute or two of watching the idle speed before the engine settled down. After bringing the avionics online, the centerpiece of which is the Dynon FlightDEK-D180 EFIS/engine monitor, we trundled out toward the runway. The first impres- sions were that the airplane sits nearly flat in the three-point stance, but that was mostly an illusion from the low cowling, high seating position and forward-canted instrument panel. In fact, visibility all the way around is excep- tional. We taxied out with both of the top-hinged doors open. The entire area above the pilot is a plexiglass pane, so it takes relatively little bank angle to be able to look into turns. Even though the cabin width of 30 inches doesn’t seem RANS S-7S Courier continued

Revised ailerons place the hinge line well behind the wing’s trailing Fuel gauges? Sure, always in sight, never need batteries. edge for reduced roll effort. huge, the impression is that the front of the excellent over-the-nose visibil- it up with IFR-ready gear, this is really office is as roomy as you’d want. ity. After an hour in the airplane, I’d a fun, see-the-scenery kind of airplane. Weather at Sebring was clear, light worked out what the picture needed to Continuing the climb, the rate winds, temperature in the high 70s. be and had no trouble nailing level-offs tapered to 850 fpm through 1500 feet With two of us aboard and half fuel, from a climb or descent. as I let the nose drop, but our climb our estimated gross weight was just Heading straight to the south of through 3000 feet MSL continued at under 1200 pounds. The initial takeoff Sebring at 65 mph indicated airspeed that pace or slightly better. Clear of the acceleration is quick, though certainly (IAS), the under-gross S-7S climbed at Sebring area, we started maneuvering. not startling. As soon as the throttle 1200 fpm on full throttle. At once you The first impression when making large is full forward, you can lift the tail. At notice the benefits of the new ailerons. or rapid turns is that the airplane wants about the time you’re wondering if the Where the previous S-7S felt light in a fair bit of lead rudder to keep the ball pitch attitude is right, the S-7S is flying. pitch and a tad ponderous in roll (actu- in the center. It’s not an annoying trait Centerline tracking was very good, with ally, that’s unfair; it was just the high as much as it is just something you must moderate rudder effort required and stick forces that made it feel less than learn to live with. Schlitter later told me little tendency to over-correct or other- sprightly), this new machine is well bal- that he had installed fairly stiff rudder- wise stymie the occasional taildragger anced. All the forces are on the light return springs to help with yaw stabil- pilot. In fact, the only odd thing you side, by design, says Schlitter, but they’re ity. The breakout force for the rudder is notice is the tendency to over-pitch appropriate for the intended mission of higher than in some airplanes, but not slightly for the climb, purely an artifact the airplane. Even though you can load out of the ordinary for taildraggers.

A dedicated, 10-cubic-foot baggage com- Dual Matco brakes respond to your toes on the small, U-shaped pedals. It’s easy to drag a partment carries up to 50 pounds. brake on landing until you get the hang of it.

14 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes Once this is understood, the S-7S flies wonderfully. As mentioned, those new ailerons bring roll forces more into line with pitch effort, so it’s much easier to peg a roll angle without inadvertently affecting pitch and, in general, the control harmony feels good. After the initial rudder input to begin the turn, you can release pressure and trim the slip angle with fairly small movements of your feet. Describing it is more work than doing it. Speed Trials We tried a couple of speed runs to see how this utility airplane performs. One test, at 5300 rpm, showed 104 mph TAS at just under 3000 feet density altitude. Another run at 4800 rpm yielded a true airspeed of 94 mph as calculated by the Dynon. We ran a back-and-forth run to compare TAS to an average groundspeed on the GPS and proved that the pitot- static calibration was right on. RANS claims a top cruise speed of 110 mph TAS, which seems perfectly reasonable at a more speed-friendly altitude. Bear in mind that the LS demonstrator had the 100-horsepower Rotax 912S and a three-blade, 72-inch Warp Drive prop; different props will have an impact on cruise and climb performance. The The latest design from RANS, the S-19, may not seem so related to the S-7S, but they S-7S’s speed is competitive with other share a simple design ethos. high-wing utility taildraggers—including the Kitfox Super Sport Model 7 and the Just Aircraft Highlander—and well ahead of the Cub-style airplanes with 100 hp. (The Cubs have about 178 square feet of wing, while the RANS has 147 and the Kitfox 132.) During the usual flight-test maneuvers, the S-7S proved to have excellent pitch stability and a healthy tendency to remain at trimmed airspeed. In the stick-free test, where you pitch up from a trimmed airspeed and let the airplane recover on its own, the S-7S returned to level flight after three long-period cycles. This means the airplane wants to return to trimmed airspeed but won’t snap right to it. Overall, the pitch and roll control systems felt like they had little friction, the forces built up naturally from on center, and it was simple to select and hold a Twin flip-up doors can remain open in The S-7S places the Rotax’s radiator at the bank or pitch angle at any airspeed from flight. cowling outlet to keep the front half slim.

KITPLANES July 2012 15 RANS S-7S Courier continued

approach to high-speed cruise. The controls stiffened slightly at high speed, but not uncomfortably so. Slow flight and stalls were, as the hack- neyed flight-test phrase goes, nonevents. In fact, the hardest aspect was finding the flap lever under your knee and wrestling the flaps into one of the two deployed

RANS S-7S COURIER Kit price...... $22,500 Estimated build time...... 800 hours Number flying...... 600 Powerplant...... Rotax 912S, 100 hp @ 5800 rpm Propeller...... Warp Drive, three-blade, fixed-pitch A “bush” tailwheel is an option on both The standard wheel fitting is a 6.00x6, but Powerplant options...... Rotax 912 kitbuilt and SLSA versions. these 8.00x6 tires are an option. Airframe Wingspan...... 29.3 ft settings. Pitch change with flap exten- the base leg, I found myself a bit high Wing loading...... 8.97 lb/sq ft Fuel capacity...... 26 gallons sion was moderate and the effect on speed and fast turning final. No problem. A Maximum gross weight (E/AB and LSA)...... 1320 lb quickly noticeable. With flaps fully out big, long slip shed the altitude quickly, Typical empty weight...... 732 lb and power off, the nose seemed relatively and I was surprised to find that the Typical useful load...... 588 lb Full-fuel payload...... 436 lb level. There was a mild shudder in the air- airplane snapped back to the desired Seating capacity...... 2 frame and the stick began to go soft just at 65-mph approach speed like it knew Cockpit width...... 30 in the stall. Despite having so little washout, what it was doing. With full flaps, the Baggage capacity...... 50 lb the airplane maintained good roll author- picture over the nose remained full of Performance ity into the pre-stall region. detail, and I had to remind myself to Cruise speed...... 110 mph (96 kt) TAS resist the temptation to fill the view ...... 8000 ft @ 75% of max-continuous, 5.6 gph Maximum rate of climb...... 850 fpm Rubber, Meet Road with cowling in the roundout. Stall speed, landing configuration...... 45 mph (39 kt) IAS Flying a new or revised model at a trade I needn’t have worried. The S-7S Stall speed (clean)...... 50 mph (43 kt) IAS show can be tricky because you might pitches smoothly into a three-point Takeoff distance...... 325 ft Landing distance...... 340 ft have to fit into a line of other demo ships attitude and loses speed in a predict- and arriving customers. That happened able way. The wheels touched down just Specifications are manufacturer’s estimates and about when I expected them to. The are based on the configuration of the demonstrator to us at Sebring; with a slightly rushed aircraft. downwind and a premature dive across only surprise was that I’d allowed my

16 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes right foot to slide up on the pedal, so we he’d like to make to the S-7S, about the All good things, because even in a time landed with a touch of brake applied. challenge of installing the new Rotax when many companies are pulling back (This even after Morenz had warned 912iS—a program the company has not on developments, it’s still true that if me to keep my big toes off the brakes!) yet begun but that Schlitter thinks is you aren’t moving ahead, you run the The tire protested momentarily before I inevitable—and about how seemingly risk of falling behind. J realized what was happening. A quick, minor changes can make an airplane. small tug on the stick to keep the nose “We want to keep things interesting,” For more information, contact RANS where it was and a small movement off he said. “There are always things we can Designs at 785/625-6346 or visit the brake pedal were all we needed. do better, ways to make the kit easier to www.rans.com. Find a direct link at The S-7S showed no tendency at that build or take weight out of the airplane.” www.kitplanes.com. moment to dart for the weeds. The Designer’s Mind After the flight, I spent a good half hour What’s in the Box with Schlitter in the RANS booth, dis- The S-7S kit comes in stages. The firewall-aft portion includes many standard items, cussing the design and how it compared such as two-place electric trim, pre-drilled aluminum lift struts, landing gear and fair- to other similar designs I’d flown. He ings, wheel and brakes, wing and fuselage covering supplies, and all fasteners—it runs was genuinely interested in how the new $22,500. The firewall-forward kit includes the cowlings, engine mount, exhaust system ailerons worked and if I thought they and prefabricated fuel lines—it costs $4500. There are several options, including the were an improvement. He peppered me carbon-fiber cowling, boot cowl and wingtips (all together, a $2700 option package), as with questions about other competi- well as quickbuild options ($9300 for the basic package) that give you powder-coated tive aircraft, and I could see his mind fuselage and tail tubes, wings assembled and covered, antennas mounted and gear legs working. Later, I ran into Schlitter at installed (among other things). In addition, RANS offers partial kits for those builders Sun ’n Fun, and he talked openly about envisioning a gradual, self-financed pace. the other changes and minor updates — M.C.

KITPLANES July 2012 17 There’s a lot to like about Whirl Wind’s new scimitar prop blade for the Rotax. By Tom Wilson

Conventional wisdom says word of remarkably clean RANS S-7. Perfor- Mark Alderson checks his pitch setting via mouth is the best advertising, and in the mance increased immediately by what the static rpm of his Rotax 912-powered case of Whirl Wind Propellers, it might looked like 10%, and so the jungle tele- RANS S-7 for the first time with Whirl Wind blades. Even without instrumented test- also be the fastest. The El Cajon, Cali- graph commenced to pounding. In fact, ing, it was clear the RANS gained mean- fornia, company released a new scimitar a visit by Attig to friend Mark Alderson ingful performance with the new blades. prop blade for Rotax 912/914 engines in nearby Fallbrook, California, con- last winter, and within a week I was vinced Alderson to fit the blades to his Hollow as a Chocolate Rabbit hearing great things about it. meticulously built S-7. When Alderson To get the straight scoop on the Whirl It started when Ron Attig—whose offered to run before-and-after testing, Wind blades, I visited with company hangar is just two rows down from I agreed to take a look at the new blade owner Jim Rust. He explained that the Whirl Wind’s Gillespie Field head- installation to see if there really would new blades are carbon fiber and glass quarters—fitted the new blades to his be an improvement. pre-pregs, built with a hollow center for

18 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes Laid side by side, the different design extreme lightness. Weight reduction is philosophies of the Warp blade (left) and highly sought after by the Light Sport Whirl Wind blade are apparent. The Whirl Aircraft crowd, which is busy counting Wind blades are $375 apiece, $1125 for a set of three, or $1550 for the complete grams to squeeze under the maximum propeller assembly—hub, hardware and 1320-pound limit, and at 1.6 pounds per blades. The Warp Drive blade pictured blade, Whirl Wind believes these are the runs $190, or $330 with optional cut-back lightest Rotax 912/914 blades available. tips, nickel leading edges and white tips. A Of course, after sweating blood for complete three-blade Warp prop assembly is just $865 with standard blades or reduced blade weight, Rust reports $1105 with the upgraded blades. Because that LSA owners overwhelmingly opt the Whirl Wind blades were a direct swap for three blades over Whirl Wind’s into his existing Warp Drive hub, Alderson two-blade Rotax offering because opted for three blades. This means he has the three-blade is a little quieter and three spare blades in case of a nose-over disaster or for use wherever maximum looks better. ground clearance is an issue. Also, mainly for noise reduction, Rust gave the new blades a scimitar sweep, but twisting is lessened, and the tip drag this also aligns with the main, er, thrust associated with less efficient designs is of Whirl Wind’s design philosophy, reduced. Given the long moment tip which is optimizing the load distribu- drag has on the blade root and crank- tion across the blades via the taper ratio shaft, it’s understandable how more “like the elliptical wing on a Spitfire,” efficient employment of the blade near Rust said. Furthermore, the thin, swept the critical outer third could mean tips increase the critical Mach number better performance. of the blade, reducing drag. Less drag Rust emphasized that it takes the means less load on both the prop and strength of carbon fiber to take advantage the engine, and thus increased perfor- of his blade’s design. Wood is not strong mance and reduced mechanical “pain” enough, and metal gets too thin and weak on the blade. at the tip, so composite is required. While the swept tips and higher critical Mach number are important, Testing Rust said it’s largely the more efficient To sample the new Whirl Wind load distribution generating the Whirl blades, I followed along as Alderson Wind prop’s efficiency. By spreading and Attig exchanged Alderson’s stock the thrust load more evenly, blade Warp Drive blades for the Whirl

There’s no confusing the angular Warp Drive blades with the organic sweep of the Whirl Winds, which lend unusual appeal to the S-7’s otherwise all-business looks. The Warp Drive is no anvil, but the new Whirl Winds are lightweight at approximately 11 pounds for the entire propeller assembly—hub and three blades. About 22.5° of pitch gives the standard 5800 rpm Rotax redline.

Photos: Tom Wilson KITPLANES July 2012 19 Switch Blade continued

Wind units. Alderson also performed a careful set of baseline and post- change test flights to document his S-7’s performance. Please note that while Whirl Wind makes a propeller assembly—hub and blades—for the Rotax engine, Alderson retained his Warp Drive hub, changing just the blades. There’s little more to say about changing the blades than is reported in the photos and captions. The basics are to remove the prop from the airframe, split the clamshell prop hub, lift out the old blades, drop in the new blades, reinstall the prop on the airframe, set After removing the upper cowl and spinner during the blade swap, Alderson simplified prop maintenance by marking his Warp Drive hub with the torque specs for both the the ground-adjustable blade pitch, and attachment and clamping bolts. that’s it. The ground-adjustable hub is dead simple—nothing more than a all ground-adjustable props, there’s a starting at a stabilized 5000-rpm carefully machined clamp, really—so good chance you’ll want to tweak the cruise at 2000 feet, then rolling in the the majority of the work is simple nut- blade angle once after putting a few elevator and full throttle to maintain and-bolt stuff. hours on the new prop assembly. 75 mph, which is the Warp Drive’s The only non-wrench work is set- best rate of climb speed. ting the blade angle, but a digital level Results Admittedly, this wasn’t calibrated and the gauge supplied by Whirl Wind Alderson used his onboard GPS, altim- NASA or CAFE testing, but wind and take the mystery out of that as well. In eter and stopwatch to run repeated temperature variables were minimized all, I’d plan on a day to swap blades, two-way passes at 3500 feet over an by running the tests within days of each which allows for setting blade angle 8-mile course to check cruise per- other during a benign period of calm and a quick verification flight. As with formance. Climb rate was measured Southern California winter weather,

With the prop unbolted from the Rotax, Alderson (left) and Attig quickly split the hub. It’s helpful to have a second pair of Assembling the new blades in the Warp Drive hub was just as easy as taking the original hands or a large bench, because once the blades out. The new blades simply lay into the lower hub half, and the upper hub half is upper hub half is removed, the blades are bolted to it. Whirl Wind says it isn’t necessary, but Attig preferred new hardware, so the free to fall out. assembly came out looking factory fresh.

20 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes Next, the blade being set is leveled laterally. A simple bubble level works fine for this.

When reattaching the prop, torque the six prop-to-flange bolts to 175 inch-pounds, but just snug the blade clamp bolts at first. Jim Rust at Whirl Wind points out that his blades use electroformed nickel leading Setting blade pitch requires finding level edges for the best possible abrasion resis- while the aircraft sits in a three-point tance. The nickel edge is not bent over Whirl Wind supplies this plywood gauge attitude, an easy task when Attig whipped a form, but built up via plating on a tool with every blade set. It features a fence set out his Craftsman Digital Torpedo Level. and then bonded to the blade. This is a at a precise 90° to the main body of the Of course, any sort of masonry or framing difficult, slow, high-end process, Rust said, gauge, which allows easy alignment of the tricks and tools can be used to find angles, the sort of thing more normally found on tool used to read out the blade angle—in but the programmable level makes short turboprop blades. this case, Attig’s digital level. work of the job.

Won’t fade. Won’t wash off. Won’t go away

Seen whenever a new RV flies.

Now occurring an average of eleven times a week at airports all over the world.

VAN’S AIRCRAFT, INC. 14401 Keil Rd NE, Aurora OR 97002 503-678-6545 www.vansaircraft.com

KITPLANES July 2012 21 Switch Blade continued with the altitude corrected for the local barometric reading. As it turned out, the barometer read- ings were 30.05/30.06 inHg for Warp testing and 30.06/30.07 inHg for the Whirl Wind. Winds were calm, the outside air temperature within 2° F during all tests, aircraft weight moni- tored and altitude held to within 50 feet over the 8 miles. Despite minor variables, the differences between the two sets of prop blades left little doubt about their relative efficiency. Cruise Speed

RPM Warp Whirl Wind % Gain

4500 87 96 10.3 5000 97 107 10.3 5200 101 111 9.9 WOT 111 120 8.1

Climb

2000-3000 ft. 68 sec. 61 sec. 10.3 Here Alderson is setting blade pitch using the digital level rubber-banded to the Whirl Wind plywood gauge. The digital level eliminates all guesswork, reading out the blade Note: Speeds are given in mph. WOT = wide open angle directly. It’s best to rotate the blade from the root because the blade tips are so thin throttle; WOT rpm is 5700 rpm for the Warp Drive and and flexible. It’s difficult to impossible to get all three blade angles exact to a tenth of a 5600 rpm for the Whirl Wind. degree, but a quarter-degree accuracy is good enough. Attig said his blades measured 22.4°, 22.5° and 22.6°, and the prop runs just fine. When the angle is set, torque the clamp bolts to 125 inch-pounds and recheck the angle; readjust if it moved. Blade Maintenance There is no preventative maintenance to speak of with Whirl Wind’s carbon-fiber blades. For its ground-adjustable props, the company suggests propeller disas- sembly at each annual inspection to allow eyeballing for chafing and cracks. There is no TBO, just the inspection requirement. If any cracks, bubbles or delaminating is found, the blade should be rejected. As with any propeller, over-speeding is a concern. If 10% over-sped (2750 rpm x 1.1 = 3025 rpm), then the blades must be inspected. If over-sped 20% (2750 rpm x 1.2 = 3300 rpm), then the blades must be removed from service. The speeds given are propeller, not engine rpm; the 912 ULS Rotax employs a 1:2.43 reduction Jim Rust holds one of the many blade designs built in his Southern California facility. ratio should you need to perform the Whirl Wind Propellers is the composite shop for both Whirl Wind Propellers and Whirl calculations. Wind Aviation in Ohio. If Rust looks familiar, it may be because his Wittman Tailwind was —T.W. featured on the January 2011 cover of this magazine.

22 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes Whirl Wind: Two Companies Interestingly, there are two Whirl Wind companies selling propellers. Whirl Wind Propel- lers—which makes the blades detailed in this article—is based in El Cajon, California, and specializes in fixed and ground-adjustable composite props for Continental, Lycoming, Jabiru and Rotax engines, plus airboats and M-14 radial engines. It is where LSA, Van’s RV, CubCrafters and other Experimental builders tend to flock. The other company is Whirl Wind Aviation, based in Austinburg, Ohio. It is a joint ven- ture with Whirl Wind Propellers and handles all constant-speed business. Hot aerobatic, go-fast, cross-country machines and some Van’s RV owners are among its customers. Both companies use the same blade design philosophy. —T.W.

Notable is the gain in both climb much in cruise speed, but that exam had and cruise; this is not a case of testing not been performed by our deadline. a climb prop versus a cruise prop. The Subjectively, Alderson and his wife Whirl Wind also went faster at WOT noted increased smoothness, less noise The Whirl Wind root section is a hair larger in diameter than the Warp Drive’s, so while turning 100 fewer rpm, another and greater thrust at idle while taxiing. minor relieving of the spinner blade open- sign of efficiency. Alderson’s home field has an uphill taxi- ings is necessary. Minor, meaning 1/16 inch. Alderson has continued to monitor his way to the runup area, and previously, It takes longer to measure and lay out the S-7’s performance through formal testing slightly increased rpm was needed to trim lines on the spinner than it does to and reports that the initial test results are power up to the runup area, but with buzz off the offending composite with a burr. Should you need a spinner, Whirl repeatable. His next step will be to flat- the new prop the RANS makes the trip Wind offers 9-inch, 9.75-inch and 11.3-inch ten the pitch slightly in hopes of gaining at idle. Whirl Wind may just be on to composite spinners with a “street price” climb performance without sacrificing something for the Rotax crowd. J of $335.

KITPLANES July 2012 23 In a discussion of aero engines, there’s always time to talk prop. By Dave Prizio

This Sensenich ground- adjustable prop is specially designed for Cub and Cub-like applications using the Conti- nental O-200 or the Lycoming O-233 engines. Shown here is a Legend Cub with a Conti- nental O-200 engine.

24 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes Fixed Versus Constant-Speed If you are on a tight budget, a fixed- pitch prop should get the bulk of your consideration. A wide variety of brands and styles is available to give you pretty good performance for a reasonable price. These range from wood propellers by small manufacturers to metal and composite models from industry lead- ers such as Sensenich. As a general rule, a fixed-pitch propeller will be lighter and less expensive than a constant-speed propeller for the same engine. On the downside, either takeoff or cruise performance must be compromised to some extent when the pitch of the propeller is The Whirl Wind Aviation G200 ground-adjustable prop on a Backcountry Mackey fixed, because the optimum pitch will SQ2. This is a high-performance prop optimized for off-airport work that costs $5500 vary depending on engine load and air- complete with spinner. Whirl Wind Propellers (a related company) also makes a less speed. The single pitch chosen by the expensive ground-adjustable GA200 prop. manufacturer is always a compromise. If you are looking at a smaller engine In the first three articlesof this to your airplane, including catastrophic such as the Lycoming O-235, a fixed- series, we’ve looked at choosing an failure, could be in store if you use the pitch prop is the default option because engine for your homebuilt project, wrong propeller. Some will work on cer- of the engine’s solid crankshaft. (So- with a brief departure dedicated to the tain engines only if specific rpm restric- called hollow-crank engines have an oil Lycoming Engine School. Now we’ll tions are heeded. If that is the case for passage through the center of the crank look at propellers. Engines get a lot of you, the appropriate warnings need to behind the prop flange used to feed attention from amateur airplane build- be on placards and on the tachometer. hydraulically controlled props.) There ers, but propellers need just as much Other propellers will work fine on some are some ground-adjustable props that attention as engines and at about the engine models of a certain size but not on allow you to change the pitch to fit the same time in the building process. others. Be sure to ask the manufacturer if particular mission, but they cannot be They go together like a horse and car- the propeller you want to use will work adjusted in flight. Also, there are some riage, as in the old song. There may be on your engine. options for variable-pitch props using as many propeller choices as there are with engines, but they boil down to two basic options: constant-speed or fixed- pitch. Constant-speed propellers give better performance, but at the added cost of price, complexity and weight. Fixed-pitch propellers are generally less expensive and lighter, but they can only be optimized for a portion of the airplane’s performance envelope. There are many factors to consider as you weigh the pros and cons of each. Not every propeller that will bolt up to your engine is a good choice for your airplane. The science of matching propellers to engines is complex and ultimately based on a lot of field testing. Each propeller manufacturer will have a list of propeller and engine combinations that it has tested and found to be good Catto supports pusher-type airplanes with a line of three-blade, fixed-pitch propellers matches. This information should be that has become quite popular with these builders. Shown here is a Long-EZ with a consulted and taken seriously. Damage Catto prop, which features a wood core covered with composite.

Photos: Courtesy the Manufacturers, Dave Prizio KITPLANES July 2012 25 Firewall Forward continued electric pitch-change motors; these tend to be expensive and somewhat rare. As a practical matter, most people using the O-320 series of engines do not go with constant-speed propellers, either. Many versions of the O-320 can be used with hydraulic constant-speed props, but if greater performance is needed, it would make more sense to upgrade to a 360-series engine. An O-360 with a fixed-pitch Nothing looks better than a wood prop on certain designs. This Zlin Savage Cub uses a prop will be less expensive and no Sensenich wood prop to pull it through the air. heavier than an O-320 with a constant-speed propeller, so why not go maximum available power on demand. or more for good reason. People like the that way and forgo the complexity of It also keeps engine speed constant even performance and stability they deliver, a constant-speed prop? when the airplane experiences pitch even at the higher price. changes that would increase or decrease Table 1 gives an example of the cost/ Benefits of Constant-Speed engine speed if a fixed-pitch prop were weight/price trade-offs involved. This For many builders, the superior per- used. This means maximum takeoff list is not meant to be comprehensive, formance of the constant-speed prop and climb performance and optimized but merely a sample of some possible outweighs the extra weight, complexity cruise performance can be achieved with choices. For the most current informa- and cost that come with it. The ability the same prop. Constant-speed propel- tion, you should consult with vendors to have the optimum pitch for every lers have come to dominate the airplane selling these products. The example in situation allows the engine to produce scene with engines of 180 horsepower Table 1 is for a Lycoming O-360 engine Print and Digital

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26 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes This Glasair Sportsman on amphibious floats relies on an 83-inch Felix Props makes low-cost wood propellers for planes such MT prop for that extra pull needed to get off the water quickly. as this GlaStar. Good performance and a great price make this Long props such as this one are de rigueur for float and bush planes, prop worth a look for builders who will be operating off of where cruise speed is gladly sacrificed for takeoff performance. paved runways in dry climates. like the -A1A that can be fitted with start as low as $1500 on up to $3000. Pitch and Diameter either type of propeller. Wood props are not sensitive to the When considering propellers, there are kinds of vibration problems that can two considerations that dominate deci- Propeller Materials bedevil aluminum props, but they are sion-making: pitch and diameter. Pitch Props are made of three basic types of sensitive to moisture and do not hold up is the bite the prop takes of the air as it material: wood, aluminum or compos- well in heavy rain or float operations. turns (or how far the prop tries to advance ite. The type you choose has implications Aluminum props are the most com- through the air for each turn). It is mea- for cost, performance and maintenance. mon and have proven to be durable while sured in inches. Greater pitch means Wood propellers typically cost the least, still reasonably priced. There is a wide greater aircraft speed, and as you might but are also the least durable and can variety in both fixed and constant-speed imagine, the greater the prop’s pitch, the require the most maintenance. Metal versions, and just about any combination more power it takes to turn it. Because propellers are more durable, but they are of engine and airframe has an aluminum power or thrust is opposed by drag, either also the heaviest. Composite propellers, propeller that will work for it. more power or less drag is needed to take both fixed and constant-speed, repre- Materials such as fiberglass, Kevlar advantage of greater pitch, and thus go sent the newest technology. They offer and carbon fiber make the new compos- faster. And because thrust and drag are good performance and light weight, but ite propellers lighter than aluminum, relatively fixed in any airplane, you must typically cost more than more tradi- just as strong and less prone to vibration tional alternatives. problems. A composite MT or Whirl Wood propellers are the lightest and Wind propeller will weigh 10 to 15 least expensive. A wood prop for a four- pounds less than a comparable Hartzell cylinder Lycoming will weigh about 15 metal prop. In response, Hartzell is now to 20 pounds, complete with a short producing composite propellers for four- extension and bolts. That is less than cylinder engines. A composite constant- half the weight of a typical fixed-pitch speed prop will cost $3000 to $5000 aluminum prop. Good wood props more than a similar aluminum prop.

Table 1

Manufacturer Type Prop Material Weight* Cost* Sensenich Fixed Metal 43 lb. $2602 Whirl Wind Ground-adjustable Composite 21 lb. $5500 Felix Fixed Wood 16 lb. $1400 Hartzell Constant-speed Metal 57 lb. $7483 The Hartzell blended airfoil prop has become popular with RV and Sportsman MT Constant-speed Composite 44 lb. $11,175 builders who want a constant-speed prop. This new design can yield an improve- *Included is the cost and weight of a governor (2 lb., $1300) for the Hartzell and MT props and ment in cruise speed of up to 5 knots the weight and cost of 2-inch extension and bolts for the other props. compared to older designs.

KITPLANES July 2012 27 Firewall Forward continued choose a pitch that gives the best compromise of takeoff performance (where less pitch is preferable) and cruise (where more pitch is preferable). All of this mainly applies to fixed-pitch propellers. Constant-speed propellers change pitch to provide near optimum performance in any situation. However, there are limits to the speed range best served by any model of constant-speed prop, so pitch is still something of a consideration. Large-diameter propellers produce more thrust, at least to a point. But This Sensenich composite ground-adjustable propeller is designed for the Lycoming O-320 diameter also ends up being a compro- engine and graces the nose of an RV-4. A similar prop for the O-360 engine is in the works. mise, because it is limited by things like ground clearance and tip speed. In a may come much too close to the ground Choosing the Right Pitch and trigear airplane, clearance between the for safe operation when installed on a Diameter tip of the prop and the ground is a major trigear aircraft with smaller tires. Unless you are among the first to concern. A prop with only 7 inches of Another limiting factor of diameter build a particular type of airplane, clearance (minimum clearance as per is tip speed. As a prop is turned at maxi- your best sources of information for FAR 23.925) must be landed and tax- mum rpm (usually 2700 to 2800), the pitch and diameter will be the airplane ied carefully to avoid striking the prop tips can approach supersonic speeds if designer and those who have built the on the ground. Nine inches of ground the diameter is too large. That means a same type of airplane. The propeller clearance is really better for trigear air- loss of efficiency and an increase in noise, manufacturers will also have recom- craft. Because of this problem, many both undesirable. Finally, certain engine mendations for the more popular kits trikes can only handle a prop of 70 to features may limit propeller diameter, and plans. Sensenich, for example, has 74 inches in diameter. An 80-inch prop mostly those related to the torsional some specific recommendations for that might work fine on a bush plane vibrations set up in the crankshaft as a many Experimental models with the with conventional gear and big tires result of size and shape of the prop. more popular engines.

Props are frequently damaged during Cutaway drawing of a Hartzell compact-hub, constant-speed propeller. A spring holds ground loops, especially on narrow, rough the blades in flat pitch (high rpm). Oil pressure from the governor via the crankshaft strips. Here you can clearly see the wood works against the spring to increase the pitch (lower rpm) of the propeller according to core that MT uses as a base for its compos- the demands of the pilot. ite constant-speed props.

28 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes In addition to serving the pusher market, Catto makes a number of models that work well on traditional front-engine airplanes such as this Van’s RV-6.

If you are building something that is a bit out of the mainstream, or if you just want to do the math for your own edi- fication, there is a formula that can get you close. P = V x 1056/R where P = pitch in inches V = cruise speed in mph R = engine speed in rpm The more your flying requires optimum takeoff and climb performance, the greater your prop diameter should be. Greater diameter produces more thrust, subject to limits, but the more you need to get off the ground (or water) quickly, the more you will be willing to push those limits. Bush planes and floatplanes both need big props to do their jobs well, which is why these planes typically have propellers of 80 inches diameter or more. However, it is still possible to have too much of a good thing. The tip speed of an effective prop needs to be kept to a maximum of 0.9 Mach (9/10 the speed of sound), and 0.85 Mach is better. To determine whether a prop is too long, you can easily compute the tip speed at maximum rpm. Here is the formula: Vt = D x R / 229.9 where D = diameter in inches R = engine rpm Vt = propeller tip speed in feet per second

KITPLANES July 2012 29 Firewall Forward continued

For an 80-inch prop turning 2700 rpm, the tip speed is: Vt = 80 x 2700 / 229.2 = 942 ft/sec. Using 1100 ft/sec as the speed of sound at sea level, we get 942/1100 = 0.86 Mach, which is within the 0.9 Mach limit. If the prop diameter is increased to 83 inches, the tip speed goes up to 0.89 Mach, which is about as far as you can push things before you start to get into trouble. Teamwork The engine and propeller are a team when The Sensenich fixed-pitch metal prop pulls this O-320-powered GlaStar through the air it comes to powering your airplane. As as it does with many other certified and amateur-built airplanes. Sensenich is an industry such they must work well together to pro- leader in both the metal and wood fixed-pitch markets. vide good performance. There are good engines and there are good propellers, but various propeller manufacturers. They tools you’ll need to install the firewall- not every good engine and good propel- definitely want to sell you a propeller, but forward components in your aircraft. ler mate well. Both components must be they also want to sell you the right one for Builders who have experience working matched to each other and to the mission your project. Use the resources available on cars or motorcycles will have most of of the airplane. Spend as much time and to you. That’s why they’re there. the basic shop tools that are required, effort looking for the best propeller as you but a number of specialty tools are do looking for the best engine. You will Up Next unlikely to be found in most builders’ be glad you did. Take advantage of the With an engine and propeller selected, toolboxes. We’ll take a look at these in technical support people available at the it’s probably time to think about the the next installment. J Previously Owned Props Used propellers can represent a good value for the amateur builder. tell you if any particular one can be saved. But once again, knowing the difference between used and used up is • Props that have noticeable corrosion, especially around the hub, vital. If a propeller has been overhauled by an FAA-certified repair sta- can be unserviceable if the corrosion is too bad. tion, it will have a yellow tag with it that identifies the prop and when • A prop with no yellow tag and no logbooks should be sent to a it was overhauled. That should be reasonable assurance that the prop prop shop for evaluation before purchase. Further investigation is is serviceable. A propeller without a yellow tag needs to be checked required before you know what you are getting. out by someone knowledgeable, which means a prop shop, not just • A prop with a gouge in the leading edge that is more than an 1/8 any mechanic. Propellers get cut down, reshaped and re-pitched over inch deep may be ready for the scrap heap. Gouges of more than 1/16 time, but without the proper information and careful measurements, inch deep on the face of a blade are also bad news. Each propeller it can be hard to tell if a prop is still within the limits of serviceability maker has guidelines for what can be repaired and what cannot. If set forth by the manufacturer. Corrosion is also a major concern. A there is any doubt, consult them. trained eye is best for spotting problems with that bargain prop you • If there are any signs of welding on any aluminum prop blade, are considering. move on. Welding is not permitted. Props have logbooks, too, or at least they should. You will want to • Wood propellers with signs of cracking or splitting should be know the propeller’s service history and, if applicable, that ADs have been avoided. They will not stand up to the rigors of flight for long. Also be complied with. Without logs you may have to pay for an overhaul to be careful if there are any signs that the metal leading edge protectors sure you are getting a good prop. As with engines, any significant lack of of a wood prop are not secure and in good condition. information should be reflected in the price you pay. Damaged composite props need to be checked out by someone Here are some things to consider when shopping for a used prop: with expertise in that type of prop. This is an extremely specialized • Props that have bent blades need to be viewed with some skepti- field, and only someone with expertise will be able to tell whether cism. It is possible to straighten some bent blades if they are not bent the damage can or cannot be easily repaired. too far and if the bend is near the tip, but you will need a prop shop to —D.P.

30 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes Got Wings? Here’s what you get in EVERY ISSUE of KITPLANES ® • Aircraft Flight Reviews • Construction Hints & Tips • Hands-On Projects • The Latest in Avionics • New Products for Experimentals • Real-World Builder Experience

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For fastest service, visit us at www.kitplanes.com/subscribe or call us toll free at 800/622-1065 A conceptual approach to building looks beyond mere physical tools. By Terry Edwards

When you think of tools for more detail. If this method of learning Usually a combination of methods, or homebuilders, you probably think of has worked well for you, you probably a multimodal approach, is best. Under- the physical tools: rivet guns, drills, haven’t thought much about its effective- stand what works for you and use it in squeezers, welders, drill presses, grind- ness. But it doesn’t work for everyone. your approach to building. ers and so on. But in the creation of an Next, consider the learning environ- airplane, there are many other tools just Learning Tools: Technology ment. Do you prefer a formal setting such as essential, such as learning tools, deci- You are probably already a pilot, and as a traditional classroom, or do you learn sion-making tools, organizational tools you’ve learned how to control and best in the comfort of your own home? and motivational tools. navigate an airplane. You also learned Are you a solitary person, or do you prefer Homebuilt or amateur-built aircraft a few basics about different types of learning in a group setting? If you are eas- are defined as those in which the major airplane construction, aerodynamics ily distracted by noise and interruptions, portion has been fabricated and assem- and engines. But building an airplane find a quiet environment. bled by persons who undertook the requires more detailed knowledge of Next, consider the learning commu- construction project solely for their own airplane technology, such as structures, nity; few people can build an airplane education or recreation. In short, this powerplants, materials, fasteners, elec- alone. Friends, fellow pilots, special- means you are learning the technology trical systems and fluid systems. ist craftsmen and component suppliers and craft of airplane building and are As an adult, you’ve probably fig- can be enlisted to help. Through the having fun doing it. ured out how you learn best, and if Internet, the learning community has So how do you learn? Your formal edu- you haven’t, think about it. Do visual expanded to include the entire world, cation was likely structured in much the presentations such as videos and slides not just your hometown. same way from kindergarten through capture your attention? Do you prefer Embarking on a major project such university. That is, a teacher stands at listening to audio books? Are you the as building an aircraft is a good incen- the front of the classroom and delivers type of person who goes to the library tive to learn new skills, but it can be the course material to the students. Each or buys books to study something overwhelming. Be assured that having subject has a textbook, and homework is new? Or do you learn best through a project will help you learn what you’ll assigned using the textbook to go into hands-on experience? need to know, even if it’s been years

32 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes since you sat in a classroom. Adults • Trade schools: The academic building will have its own special tools, tend to be problem-centered, results- requirements for an Aircraft and and each tool requires specific knowledge oriented, self-directed, discriminating Powerplant mechanic’s certificate are to use it, as well as the manual dexterity and relevance-driven, and they accept available as correspondence or online to use it well. responsibility for their own learning. courses from numerous trade schools It has been said that aircraft building All of these traits work in your favor. around the country. Embry-Riddle is just an excuse to buy tools, and while You’ll find a number of sources to Aeronautical University and, in Can- there may be some truth in that senti- help you learn the technology of aircraft: ada, the International Correspondence ment, there is no doubt that the right tool • Books: Textbooks and other ref- School’s Aircraft Mechanics course, are makes the job easier—or in some cases, erence books are readily available in two such sources. While you don’t need possible. By anticipating the type of work libraries and from general and specialist an A&P certificate to build an airplane, your aircraft will require, you can begin booksellers. At the least, you will need the these courses will give you a thorough gathering the tools you’ll need. Once you FAA publication AC 43.13 Acceptable grounding in aircraft technology. The have them, learn to use them. Methods, Techniques, and Practices—Air- FAA’s web site (http://avinfo.faa.gov/ Tools can pose a danger to you, as well craft Inspection and Repair (available for MaintenanceSchool.asp) has a list of all as the part you’re working on, if they are download at http://www.faa.gov). schools that offer accredited programs. used incorrectly. It is easy to irreparably • Magazine articles: Enthusiast pub- • Mentors: Seek out veteran aircraft damage an expensive part, so begin by lications such as the one you’re reading builders who have gone through the practicing on scrap material until you now are a good source of information. process. Most will be happy to share get a feel for the tool and its capability. Many have previous articles archived on their experience and expertise with Becoming a craftsman requires prac- a related web site. you. You can find them anywhere pilots tice, but it also requires the right atti- • Online courses: Many professional congregate: EAA chapter meetings, the tude. If you say to yourself, “I will be a associations have online courses that local airport or in flying clubs. craftsman in everything I make and be can address your needs, such as the Soci- prepared to remake it if it is not up to ety of Automotive Engineers and the Learning Tools: Craft acceptable standards,” you are well on American Institute of Aeronautics and Once you have a basic understanding of your way to becoming one. Even if you Astronautics. (Many even publish tech- aircraft technology, you can start devel- are just cutting 2x4s to make a stand to nical and historical books.) Colleges and oping your building and craft skills. To store your parts, take the time to mea- universities also offer online courses. quote Louis Nizer, an English lawyer sure accurately, cut using the right tools • Video courses: The Experimental and writer: “A man who works with his and drive the screws without stripping Aircraft Association (EAA) has numer- hands is a laborer; a man who works with the heads. This conscientious attitude ous short video courses on a variety of his hands and his brain is a craftsman; will give you a reverence for the tools topics, including aircraft technology. and a man who works with his hands, his and a feeling of great satisfaction in your • Forums: Online or onsite forums brain and his heart is an artist.” finished product. offered by some kit manufacturers and As a builder, you need to become that If you run into problems, help is suppliers may be a valuable resource. craftsman and aspire to be that artist. available from the kit manufacturer, Many additional forums are presented at Begin by familiarizing yourself with specialist builder assistance companies, major annual fly-ins around the country. the tools. Every operation in aircraft hands-on courses at forums at fly-ins

A forum setting allows learning aircraft-specific knowledge in a Mentors make it easier to learn the craft of aircraft building. small group.

Photos: Terry Edwards KITPLANES July 2012 33 Tools for Homebuilders continued of plastic resins and the curing time, best alternative. While the process may temperature and pressure required. Kit seem objective and logical, the difficulty and, especially, mentors. There is noth- manufacturers explain most of this in lies in how you define “best.” In some ing like learning one-on-one from a their assembly instructions, but you’ll cases, best may be the lowest-cost solu- craftsman to help you become one. achieve better results if you understand tion, while in others it may be the most Beyond mastering tools, you’ll need these processes in greater depth. elegant solution, and in still others it may to know about the materials you’ll As with technology, craftsmanship be the most time-efficient. So going back be working with. The most common with tools, materials and processes to the problem-analysis stage, what is best include steel bars and tubing, various can be learned, and most of the same must be defined in the context of the deci- types of covering fabric, aluminum sources apply. Mastery of the craft, sion being made. extrusions and sheet, nature’s own however, demands the right attitude People employ many techniques in composite material (wood), man-made about developing the skill and, more everyday decision-making: composite materials such as epoxy and than anything, plenty of practice. • Prioritization: This involves weigh- polyester resin, fiberglass, Kevlar and ing the alternatives according to a scale or carbon-fiber cloth. Each of these has Decision-Making Tools matrix and then selecting the top choice. different properties and requires differ- Every day you make hundreds of deci- • Pros and cons: List the positive ent tools and techniques. For example, sions—what to eat for breakfast, what and negative aspects of each alternative most metallic materials are ductile to wear, what route to take to work, and choose the one with the most pros (which means they deform under ten- where to go on vacation. You probably and fewest cons. sile stress) and malleable (which means don’t give the process much thought. • Satisficing (combines satisfy and they deform under compressive stress). But building an airplane requires a high suffice): Select the alternative that meets The property of ductility means the degree of decision-making that starts a criterion of adequacy, rather than a cri- material can be formed through bend- even before you place your order, such as terion of optimum. ing, rolling or drawing. The property how you will use your airplane and what • Expertise: Rely on the judgment of of malleability means the material can kind of construction you prefer. an expert in the field. be formed by hammering, stamping or There is a difference between prob- • Gut feel: Use an emotional basis pressing. Brittle material such as plas- lem analysis and decision-making. where there is a high level of uncertainty tics must be molded into shape. Com- With problem analysis, you define the or if the facts are limited, ambiguous or posite materials combine fibers that are problem to be solved, gather informa- incongruent with events. strong in tension with a resin that is tion, explore alternative solutions, and • Random or coincidence: Use strong in compression. identify the principles to judge the chance—flipping a coin or cutting a To form and combine aircraft parts alternatives. Brainstorming at any stage deck of cards. into assemblies, you’ll need to master of this process will help you broaden • Divination: Use prayer, tarot cards, the processes appropriate to the mate- the scope of alternatives. revelation or something similar. rials. In some cases this means know- Decision-making involves evaluating Of course, the methods near the bot- ing the speeds and feeds for effective each solution in terms of its consequences, tom of this list may not lend themselves drilling or machining and, in other ranking the possible solutions using selec- to well-considered decision-making cases, understanding the mixture ratio tion criteria, and then determining the on your aircraft. Nevertheless, they are worth knowing about, if only as methods to be avoided. Notice that the lower down the list, the fewer facts are used. With a well-known quantity such as airplanes, the facts are almost always available, so it is simply a matter of how much effort you are willing to expend to find them. It comes down to education: Your learning skills and research abilities will allow you to gather the facts that are necessary to the decision-making process. People tend to accept expert judgment as a good basis for making a decision. But the difficulty lies in deciding whether someone is actually an “expert”—does he or she have the Exploring alternative solutions for an aircraft system. knowledge and experience to make a

34 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes sound judgment? This in itself involves a decision-making process. When an opinion is presented loudly enough, or logically enough, or often enough, it is easy to be fooled into thinking it is fact. So your first decision-making step should be to evaluate an expert’s qualifications, and then to evaluate the advice. Start screening experts by reviewing their professional qualifications in a relevant field such as engineering or aircraft maintenance: the books or papers they may have published and their repu- tation. The Internet, of course, is filled with opinion masquerading as fact, and Using organizational tools such as spreadsheets may help keep your project on track. it’s increasingly difficult to determine We’ll look more into organization in the next installment. an expert’s qualifications. Opinions expressed on specialist online forums then the case can be made for a project only flown low-powered aircraft on local are probably the most difficult to evalu- director. Ideally, this should be a trusted flights but plan to travel more, a faster ate unless you know the qualifications of mentor who understands an individual airplane may be all you think you need. the person posting and can cross-check builder’s abilities and needs. But with a faster airplane, you may find the information through other sources. Finding such a person may take that you need IFR capability to get the If you ask for advice in online forums, some effort. Keeping in mind my most out of it. Or you may think you be careful how you pose your question. comments on faulty consensus, your want a utility plane, only to discover that For example, if you ask for consensus on project director should not be “one of you really enjoy aerobatics and forma- how best to wire a panel, you may only the guys in the coffee shop.” They may tion flying. get feedback from those people who have some experience, and will surely Defining your end use is critical to have been wiring incorrectly. With no have opinions, but they may not have enjoying the aircraft that you build. As conflicting opinions, it is easy to con- your needs in mind when they make part of your education process, then, clude that their advice is valid. decisions for you. It also may not be sample as many types of flying as you The final step in your decision-mak- the guy with the flashiest plane on the think you might like to do. You can ing process is to evaluate the outcome of field. He has the advantage of having take lessons from an instructor, or even your decision as it relates to the overall gone through the building process, beg rides with pilots who do the kind of cost of your project, its timeline and its thus gaining the experience and exper- flying you are interested in. Either way, effect on, or interaction with, other parts tise, but he may validate his own proj- this is less expensive than building your of your project. This information will ect by spending your money to build airplane and finding out it doesn’t fit guide you in further decision-making an airplane exactly like his. your needs as you grow as a pilot. down the line. If you decide you need a project director, That’s it for Part 1. Next time we’ll take the time to make a list of your needs look at organizational tools, project Project Director and wants, along with your time and bud- management and ways to keep you If a group is building an airplane proj- get, and then search for a trusted mentor. motivated through your build. J

ect, it’s easy to understand the need for a Your list should include your plans EDWARDS TERRY project director. He or she is the person and ideas for your completed airplane. If Terry Edwards is a chosen to be responsible for the deci- you currently own an airplane, you may mechanical engineering sions and actions of the rest of the group. want your newly built aircraft to have a technologist, Private Pilot But with a more typical single builder, a higher top speed, a lower stall speed, a and aircraft owner. He is project director is probably unnecessary. better climb rate, a higher service ceil- currently After all, individual builders can make ing, IFR capability, to be equipped with building their own decisions and end up with floats or skis, or have additional or fewer a Van’s exactly the airplane they want, right? seats than your current airplane. The RV-9A. True, as long as those builders are able difficulty is that unless you have a lot to make those decisions. But if they are of experience with a variety of airplanes not interested in doing the research, operating in different environments, it checking facts, developing knowledge is hard to know just what capability you and skills and evaluating alternatives, will grow into. For example, if you have

KITPLANES July 2012 35 Inside KITPLANES® Flight-Review Procedures

It’s a lot more than kick the tires and light the fires. By Marc Cook

Taking a critical look at an airplane that didn’t meet claimed performance; Conducting the review at the factory you’re thinking of building isn’t much companies able to cash deposit checks also gives us a chance to see how the different for you than it is for us. In fact, but unable to deliver kit parts; and pro- company operates, and it’s one oppor- we at KITPLANES® consider many jects that, sadly, go unfinished. tunity you should not miss in your own of the same things you do, or should, research. Even better is attending an on- in terms of aircraft design and perfor- The Front Door premises workshop; you get to see how mance. We know you’re interested in Our intention is to provide valuable the company operates, and at the same how an airplane performs—does it meet information on the airplane and the time gain valuable experience with the stated performance goals and do so in a company, and that starts as soon as materials and processes involved in the reasonable way? (I’ll explain that com- we arrive at the factory. A quick aside: actual building. What could give you ment shortly.) But we’re also trying to Though we sometimes test-fly aircraft at better insight than spending time with view each airplane design as a whole, not major airshows, we generally prefer to the staff and the kit itself? just as a set of performance numbers and visit the factory to conduct the evalua- Unless you’re visiting on a Friday subjective handling qualities. tion. Why? Mainly because it allows us afternoon or Saturday morning, the kit Some builders get caught up in the the freedom of time. If the weather’s company’s shop should be busy. (One excitement of the project and put their marginal for a flight test, we can post- exception is when the company runs sensibilities on hold. They are able to pone until it looks better. We also don’t early shifts, as many do in the hotter ignore the subtle cues that suggest— have to share time with the company parts of the U.S. during the summer.) but don’t yet prove—that a company or personnel who are trying to actually That’s not to say full to the rafters with an airplane might not be as presented. sell kits. Their time at airshows is bet- parts and workers standing elbow-to- Homebuilt aircraft history is full to ter spent moving the merchandise than elbow. Today’s manufacturing technol- overflowing with sob stories of airplanes hanging with the rogue scribbler. ogies allow companies to do more with

36 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes fewer people. But you also want to see flights. (It explains our enthusiasm for However, we rely on some technology how much of the final kit is produced in- actually getting to go places in test air- to help us take notes. First is a digital house. Can the company form its own craft!) Remember, though, that the job voice recorder—the brand isn’t impor- parts from sheet metal? Are the molds here is not to learn what the airplane is tant—with an external-microphone for composite parts there? (The excep- like to live with but to verify a few per- input. We then put a small microphone tion is normally for companies that use formance points, make a top-line evalu- into the headphone ear cup to capture fiberglass only in cowlings and fairings; ation of handling qualities, and see if the cockpit chatter. It’s vitally important it’s often more efficient to have an -out airplane is comfortable to sit in and fly. to record the flight somehow. In your side contractor supply the ’glass.) Does demo flight—just as in ours—the work- the company making a tube-and-fabric Tools of the Trade load is simply too high to see what you utility airplane do its own welding? The Before electronic instruments were need to see and take physical notes at the goal of this “snooping around” isn’t to prevalent, we used to drag along a small same time. count inventory, but to get a sense of the gear kit to help ensure we were getting company’s health. the best in-flight data possible. With Who Are You Talking To? the aid of a portable GPS and a device To make the system work, we typically The Plane! such as the Proptach (an optical, elec- call out the major indications during Next on the list is to spend some tronic portable tachometer), it’s possible the flight and also make a point to call time looking at the airplane itself. At to nail down key performance specs by out the passage of altitude benchmarks KITPLANES® we have a blanket policy reducing (but not eliminating) the vari- during the initial climb phase. Digital to wait until all of the Phase I flight- ables. The GPS allows you to run a num- recordings have a time stamp, so it’s easy testing has been completed before we ber of “speed trials” and get an accurate to look back at the flight and calculate conduct a flight test. For starters, that’s groundspeed. (I recall doing the same rate of climb and descent. the best legal angle because, technically, test before GPS, where a DME station Lately, I’ve taken to the new GoPro the airplane isn’t supposed to carry pas- was handy; before that, test pilots would Hero2 compact digital video camera. sengers until Phase I is complete. You use ground-reference points a known The second-generation version includes are also not being compensated as a test distance apart.) an external-microphone input where pilot, so it pays to politely ask the status In today’s aircraft, the electronic the first didn’t. I take an inexpensive of the aircraft’s test flying and absolutely instrumentation is difficult (though not lavalier microphone, drop it into one of determine how many hours it has flown. impossible) to skew and generally quite the headset cups and connect it to the Before you fly, there are important accurate. As such, we typically bring camera. In most aircraft, you can suc- questions worth asking: How does the little in the way of investigative gear tion-cup-mount the Hero2 to the can- demo aircraft differ from the final kit? into the cockpit unless the demo plane opy so it’s within reach and has a clear, What factors might influence the differ- is minimally equipped. wide-angle view of the instrument panel ence in performance between the demo plane and stated performance? Typi- cally, kit companies derive their bro- chure numbers from the factory demo airplane, so the airplane you fly should be able to duplicate these performance figures. If it can’t, you need to know why. Either something has changed— it’s common for small companies to try different cowlings, landing-gear configurations, propellers and even whole engines on one airframe—or the numbers are suspect. In addition, it’s critically important to have at least a basic plan. This could be as simple as taking off, climbing to altitude in the general direction of the local “practice area,” performing a few basic maneuvers, doing speed checks, and then descending back to the airport for landings. Indeed, this outline The reviews are typically with a company test or “demo” pilot, usually for reasons of generally describes most of our review safety and insurance coverage.

Photos: Richard VanderMeulen, Kevin Wing, Marc Cook KITPLANES July 2012 37 Inside KP: Flight Reviews continued and primary flight controls. It’s amazing what you don’t remember doing during a flight that you can plainly see in a replay of the video. For purposes of having all of the data in one place, I’ll recite the aircraft, approximate loading, fuel state (how much and where it is among the various tanks) and local atmospheric conditions for the recording. Take a moment to get the local ATIS or AWOS information When you visit the factory—and you definitely should—evidence of raw materials to on the recording as well. That way, when build kits (above) and ongoing projects (below) should be visible. you’re back at home listening to your recording of the flight, you can normal- that as you bring the nose up (in a tri- shows all of the cylinders at once), as ize some of the observed performance cycle-gear design), no other pitch inputs well as oil temperature and pressure. against known atmospheric conditions. are required to hold the desired climb Beyond the hard values, you’re look- Did you think the takeoff roll seemed attitude. Some tend to pitch nose-up ing to see how the airplane handles at longer than the specified value? You can after the weight has come off the gear; relatively high power and low speed. check density altitude later and see that see if you can sense this tendency. It should be easy to put the nose at any the airplane thought it was at 3000 feet As the airplane leaves the ground, call point on the horizon and hold it there. MSL…ah, that makes sense. out for the recording so that the climb You should not have high control pres- The first takeoff is normally -con clock can start. Then make a note of sures in any axis, though it’s not unusual ducted as a standard departure. I’ll ask passing through the first 1000 feet and to have comparatively high rudder the demo pilot for recommended rota- each 1000 feet of altitude thereafter. It’s pressure in aircraft without adjustable tion and initial-climb airspeeds. I’ll easier to mark whole thousands rather rudder trim. If you do have to really then try to describe the takeoff for the than to refer to altitude as AGL (above mash on a pedal, make a note of it for recording, explaining how smoothly the ground level). During the initial climb the recording and try to remember to power comes up, how well the airplane to altitude, note the airspeed and indi- observe how it is during level flight. tracks the runway centerline, noting any cated climb rate, and then look at the Different aircraft will have different tendency for it to dart for the runway engine gauges to note things like mani- force gradients; a design you’re sure will lights and, especially, how it feels just fold pressure, rpm, fuel flow, the highest never have the ball centered based on coming off the ground. Some aircraft EGT and CHT values (along with any excessive climb-phase pressures might have their landing gear positioned so unusual spreads, if the instrumentation just surprise you.

38 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes A good portion of the flight review will focus on aircraft handling, but that’s not the only important variable.

Generally, we try to reduce the number of turns in the initial climb to get a better sense of the climb rate, but that’s not always possible for reasons of weather, navigation or terrain. Just make a note of the turns—or simply that you are turning—for the record. Cruise Performance Because our flight-review time is limited, we can’t take data points all over the performance map. Instead, we choose a few to spot-check, in part to see how the airplane performs on its own merits but also as a cross-check to the claimed figures. When it comes to conducting your own flight tests, you’ll be surprised to discover that collecting good cruise numbers—at various altitudes, weights and atmospheric conditions—takes an astounding amount of time and surgical care. I spent several days with my Sports- man trying different altitudes with various combinations of engine rpm, manifold pressure and fuel flow. For a non-turbocharged airplane, best cruise speed will typically be the highest altitude at which the engine produces maximum-recommended cruise power. Some aircraft have a fairly sharp drop- off in performance with altitude; that is, as the airplane climbs, it becomes sig- nificantly slower. Others, usually those with long, thin wings, can hang on to near-peak cruise numbers to a higher altitude. This is a design point you obviously can’t do much about. Determine ahead of time what the power settings will be for the cruise

KITPLANES July 2012 39 Inside KP: Flight Reviews continued employs an articulated pitot head that airplane handles in cruise. Are the con- follows the path of relative wind inde- trol forces acceptable—not too heavy or portion of the flight. It’s not important pendent of the aircraft’s AOA. light? How is the balance? A classically to verify that what the demo pilot says In cruise, we tend to use a two-way balanced aircraft has the lightest forces is, say, 75% right there and then, but GPS run to validate performance. There in roll, heavier in pitch and reasonably make a note to check the figures later. are more detailed methods using three- stiff in yaw. Designs that are very light Remember, too, that engine power is a and four-way runs, but we’ve found in pitch and yet require a lot of effort in combination of throttle opening (man- the upwind/downwind process to be roll tend to be hard to fly smoothly and ifold pressure), engine speed (rpm), reasonably accurate and quick enough accurately—not always, but mostly. and fuel flow (gph). On aircraft with a to implement easily. Before the flight, constant-speed propeller, your best bet check the winds aloft. Your job is to fly Stalls and Spins is to choose an altitude and power set- directly upwind at a given power set- Our policy is to avoid spins and aggres- ting that permits wide-open throttle, ting and indicated airspeed (IAS) and, sive stalls in virtually all designs. The which both maximizes power output after the value has stabilized, record exceptions might be those aircraft and also eliminates any instrumenta- groundspeed. (Be sure you have con- designed for aerobatic flight, and only tion variable. verted from the report’s true north to then do we break the rule if there’s a magnetic north.) Turn 180° and repeat. parachute available and the test pilot Verifying Speed And be sure the airplane’s IAS has feels like egress would be possible with- The pitot-static system is prone to errors, stabilized after the turn. GPS-derived out extensive ground training. We’re both from the location or design of the true airspeed (TAS) has the benefit not beyond a simple aileron roll or steep pitot head and/or static source, but also of needing no information from the turns with some G force sans parachute, from instrument errors. What’s more, onboard instruments beyond altitude but the risk/reward equation gets pretty you can’t expect a non-articulated pitot and outside-air temp. Generally, the lopsided much beyond that line. head to be accurate at cruise angles of altimeter is fairly accurate, and it’s pos- We work up to stalls progressively, attack and equally so at an AOA near sible to take the forecast temperature at starting with power-off, straight ahead stall. As a result, the stall speed is likely altitude as a rough check of the outside slow flight gently drawn toward the first to read quite low—the indicator might air temperature system. Remember that indication of a stall. If the airplane shows say 40 knots, but the airplane is actu- a higher-than-actual OAT reading will good manners, we’ll try other configura- ally traveling considerably faster. That’s skew TAS values upward. While you’re tions—full flaps if we started out clean, why professional flight testing, such checking numbers and reading them for example, but we’ll work through the as is done by the CAFE Foundation, aloud for the recording, see how the intermediate steps as necessary—and

40 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes Electronic instrumentation takes much of the guesswork out of flight testing. Still, you can’t just take every indication at face value. Is the true airspeed calculated by the Garmin G3X (left) accurate? Is the fuel flow shown by the TruTrak engine monitor correct? In-flight cross-checks will get you close, but be sure to apply common sense to performance claims. even some stalls in coordinated turns. a coordinated turn. Some aircraft hold the later—heck, we frequently do, as we are We’re looking for a strong announce- set bank angle and some want to return to sitting down to write the review—that ment before the stall and a gentle break wings level, while others want to tighten you didn’t even think to ask in the heat of with little to no tendency to drop a wing. up the turn. This is called neutral, positive the moment. You might get the answers Be wary of the excuse that the demo and negative roll stability, respectively. from your photos, and, after listening to plane has “a little rigging problem” as All aircraft are a little different, so we’re the recording of your flight, it’s certain an explanation for a serious wing drop. looking for the outliers—designs that do you’ll be a much better-educated cus- Don’t you think the company would something quickly, unexpectedly. tomer. That is the whole point, isn’t it?J want its demonstration aircraft to be the best it can be? Shouldn’t it be better built Back to the Barn than customer examples? Landing an unfamiliar airplane is always a crapshoot. I’ve had so-called easy air- Returning for Landings planes play rough, and I’ve flown some On the way back downhill, you can try theoretically difficult designs that were a few simple maneuvers to check basic forgiving enough that we could reuse stability. With the power reduced, trim the airplane after my flight. During your the airplane for a given speed, preferably demo flight, you might not get the chance near maneuvering speed. Pull on the to commit the landing, but it’s worth stick to reduce the IAS by 10 knots and watching a few things. First, how busy then release the stick. (You may have to is the demo pilot? A lot of stick move- “bracket” the stick to maintain wings ment—assuming you have reasonably level, but try not to impart any pitch smooth atmospheric conditions for the force.) See what the airplane does next. flight—can indicate low-speed instabil- A longitudinally stable aircraft will ity. Second, how fast is he flying it? A nor- pitch back in the direction it came from, mal baseline approach speed is 1.3 times overshoot slightly, stabilize slightly the landing-configuration stall speed. If more nose-low than before, and then your demo pilot is coming in with the tail move nose-up to recover. Most aircraft on fire, there could be a reason beyond his have this motion, called a phugoid, com- desire to use the bathroom. A demo pilot pletely damp out in three or four cycles. who refuses to use full flaps should make An airplane whose nose stays where you you wonder why all that flap was put into left it when you let go of the stick has the design in the first place. poor longitudinal stability and/or a lot After landing, before you move on to of control-system friction. other matters, take a moment to double- We also look for the airplane to be self- check that your recorder worked and correcting in yaw—the vast majority of whip out your digital camera. Grab detail them are—and we want to see how they shots of the airplane, especially the panel respond when the controls are released in and interior. You will have questions

KITPLANES July 2012 41 Considerations when installing an alternative engine. Editor’s note: We simply ran out of room to wiggle room as long as you don’t exceed to the engine’s crankshaft. A horizontally cover this topic in the May 2012 Alternative the designer’s maximum structural limit opposed engine such as a VW, Corvair Engine Buyer’s Guide, but it’s too good to for the firewall-forward installation. For or Subaru will have the crank located in leave on the cutting-room floor. example, if the specifications state that the same general location as a certified the maximum limit is 200 pounds and engine. Although the VW and Corvair Let’s say you’re looking for an engine the recommended engine is 165 pounds, don’t normally use a PSRU, the Subaru for your homebuilt. You are set on some- there should be no reason you can’t usually does. While belt drives will offset thing new and different, and you’re willing safely install a 200-pound FWF package, the crank centerline (typically above the to pioneer the installation. Good for you! but you will need to consider how you’ll crank), many geared drives are available Back in the May issue, when we cov- keep the empty center of gravity (CG) with zero offset. And many of the geared ered alternative engines, I warned that where it should be. If your FWF package redrives that have offset allow for install- it’s imperative to research the engine weighs more than what’s installed in the ing the gearbox in an up or down position. manufacturer. Far too many people prototype, you may have to add ballast Thrust line variation: Can it be moved? have been stung and received nothing aft of the CG or move something that’s Like the FWF weight, many designs have in return for their deposit except broken normally located in front of the CG (such some wiggle room for deviation. It’s promises. But let’s assume we’re past as a battery or radiator) to behind the CG. possible that your chosen airframe can that point, the manufacturer is trustwor- Can an engine be too light? Although not handle the thrust line being moved a bit thy, we have accurate information on usually a problem, in some instances the without negatively affecting the pitch- weight and power specifications, and the alternative engine may be lighter than the ing moment caused by throttle changes. engine seems a good match for the air- one the plane was designed to fly with. One way to take the guesswork out of frame. Now let’s consider the mechanical Again, CG is important. The easiest solu- the what-ifs is to model it in X-Plane, a issues of the physical installation. tion is to add weight in front of the CG. dynamic, affordable and accurate com- But if you are going through the time and puter flight simulator that allows you to Support expense of installing an alternative engine design virtually any shape and size of How receptive is the airframe designer to that has the benefit of being lighter than aircraft and test-fly it www.x-plane.com( ). making changes to the installation? OK, what’s specified, should you throw that There are physical concerns with moving this isn’t a mechanical consideration, but away by adding weight? Consider moving the thrust line as well (particularly when it’s important. Some plans providers or the engine forward. This will mean a new moved down), and a couple of these are kit manufacturers will essentially disown or modified cowl, and the appearance will prop clearance from the ground or the you for straying from the engine they be changed. Like everything else in avia- front tire, and the overall aesthetics. support. Still, there are many who will tion, it’s a compromise. work with you to see that you’re success- Engine Mount ful. Choose carefully. Thrust Line It’s all about the triangles. It’s not likely the Is your proposed engine shape similar to engine you’ve selected will have mount- Weight the prototype’s? Can it be easily installed ing points that match the mount supplied Is the weight a good match for the airframe? with the thrust line in the same location? with your kit or outlined in the plans. So If the weight of the proposed engine is Most auto conversions use a prop-speed before you order your engine, talk with the different from the one specified for your reduction unit (PSRU) that can affect the supplier. Many engine companies have project, all is not lost. There will be some location of the prop’s centerline as related scaled, measured drawings referencing

Pat is the editor of CONTACT! Magazine and EAA’s Experimenter eNewsletter. His passion for aviation began when he was 14 and he became a lineboy at El Mirage Soaring Center. This led him down the path to becoming an instrument-rated Private Pilot, homebuilder and supporter Patrick Panzera of alternative engines with a particular interest in Corvair conversions.

42 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes mounting points and prop station in three you have several issues, the most obvious axes. If you plan to build the mount your- being where to put the radiator. self, or at least make the parts and have an So I’m a plumber now? Once you’ve expert weld them, you will need to either considered the possible locations for the mock the engine in front of the firewall on radiator, and how to pass air through it your actual airframe or create a stand-in efficiently, the next consideration is rout- firewall mockup of the airframe. Then it’s ing water to and from it. But before that just a matter of connecting points. Take you really have to consider CG again, as cues from the specified mount design; the radiator full of coolant will have a sig- you want your bracing members to be in nificant weight contribution. The farther tension, not compression, if possible. Mind away from the water pump the radiator the prop rotation, and properly brace is located, the more issues can arise. If With the cowl off, you can see that the lightweight 2200cc Jabiru had to be against torque. Consider thrust-line offset the radiator is inside the cowl, traditional- pushed rather far forward for CG concerns. as related to the direction the engine oper- length radiator hoses might be used. ates. Your new engine may spin the prop The longer the run, however, the heavier opposite of the prototype, and where the installation becomes, and that’s why down and left are specified, you might many builders have opted to use alumi- have to cant it to the right. Pay attention to num tubing wherever possible. The light- the nosegear strut and maingear attach- ness of the aluminum and its ability to ments. Many engine mounts are compli- wick away heat is a benefit, but mounting cated with landing-gear attachments that points, bends and transitions (and attach- could become an issue. Any changes to ments) to flexible lines can become failure the geometry to accommodate the engine points and maintenance issues. may compromise the strength of the gear, Oil Cooling: Another radiator? While or in the case of a nosegear strut that’s not not all alternative engines have remote part of the engine mount, it may simply be oil coolers, a lot of builders add them. in the way of the engine mount tubes or Like the radiator, it’s all about location. an engine accessory or component. To work efficiently, the oil cooler needs This all-aluminum, direct-drive, small-block Ford stuffed into the rear of a Long-EZ is a Can the engine manufacturer help? a supply of cool air and a way to move it one-off design built by Gary and Char Spencer. Many engine manufacturers will assist through freely. This adds another layer with the design and fabrication of an of complexity and additional points of of the hottest and loudest exhaust of engine mount, especially for popular air- failure, but an oil cooler often makes the any powerplant and may damage some craft designs. Even though this has the difference in keeping operating tempera- exhaust systems. Turbocharged engines potential to be a symbiotic relationship, tures in check. Water-to-oil heat exchang- can be the easiest to provide an exhaust don’t expect any favors or preferential ers have been used to help control the system for and usually don’t need a treatment. There are countless projects oil temps in applications where ducting muffler, but the heat of the turbo itself in the homebuilt community that got cooling air to an oil cooler isn’t practical. must be managed, and getting cool air off to a good start and have yet to fly. through the intercooler can be an issue. An engine supplier can’t bank on your Exhausting Stuff enthusiasm while waiting for you to fin- Removing the spent air/fuel mixture. The Cowling ish, so be prepared to pay a reasonable exhaust system can be nearly as dif- Keeping it all under wraps. A properly fit- fee for your engine mount. ficult to create as the cooling system. ting and functioning cowl is essential. It There are many theories about how to protects the engine from the elements, Cooling manage exhaust, but most agree that directs the airflow around and through Now the real fun begins. How does your pro- straight exhaust, following the shortest the engine compartment and its acces- posed engine get cooled? If it’s air-cooled, path to the slipstream, is the most effi- sories, and provides for induction air you are 90% there (with 90% still to go). cient and cost effective. Talk with the (allowing for ram air and/or alternate air Considerations are updraft or downdraft, engine supplier, as there may be some and carb heat) and an exhaust system inlet size, shape and spacing (same for easily overlooked subtleties. The Viking outlet. It blends the spinner to the air- the outlet), baffles (size, shape, construc- 110, for example, has a single opening in frame, and it must be structurally robust tion materials, pressure plenum, seals, the bottom of the engine onto which the yet lightweight, resist harsh chemicals cylinder movement, cable and wire rout- exhaust system attaches. The exhaust and heat, offer easy access to preflight ing) and delta P, ensuring a good pressure runners are cast into the head itself. Will items—and look good. Plus, it has to drop from the inlet to the outlet across it be in the way of your nosegear strut do all this without adding drag or other the engine. If the engine is water-cooled, or bracing? The rotary engine has some airflow-related anomalies.J

Photos: Patrick Panzera KITPLANES July 2012 43

Where’s Your Margin? By Paul Dye

I am a strong believer in margin— Structured Learning factor of safety, he will shave more off that bit of extra space that you give Structural margin is usually represented structure if that margin is exceeded. yourself to make life a little more com- as a factor of safety above the expected Sometimes he will shave if the goal is to fortable. What do I mean by comfort- loads to be put on the structure. A very produce the lightest structure possible. If able? In an aviation context that means common design load factor is 1.4, mean- you are trying to build a world-record set- I am not sweating bullets or screaming ing that the structure is capable of with- ting airplane where ultimate performance silently because I am worried about the standing 40% more load than what it is important, then you will want to save outcome of whatever it is I am doing. is rated for before bending or breaking. weight wherever you can. In the aerospace Margin is not always mental. It can If the designer intends the airplane to world, weight is always detrimental when be designed into airframe structure, be routinely operated up to 3.0 G for trying to get a vehicle into orbit, so mar- systems, equipment and the way we instance, and he is using a factor of safety gins are carefully controlled, and when operate all of the above. Margin is the of 1.4, then the structure shouldn't break they tell you that you have 1.4, you should extra strength built into your spar, until a G-load of 4.2 is exceeded. never assume that you have 1.5. that handheld radio you have in your The truth is that most (but not all) There’s a great magazine ad from the flight bag or the extra fuel you keep in light airplanes are overbuilt in this regard. 1970s that shows a Mooney with a stag- the tanks in case the headwind gets a Because a designer’s goal is to have a 1.4 gering number of employees standing little stronger. When aircraft are designed and built, certain assumptions are made about the strength required, the capability of the systems, and the limits of endurance and range. Building and providing margin should be a goal of every aircraft designer and pilot because we never know when our assumptions about what the limits This is more than a creative way to take a group photo. It is also intended to convey that should be might just be wrong. there is a good deal of margin in the wing structure.

Photos: Marc Cook; Illustrations, Robrucha KITPLANES July 2012 45 Build It Better continued and sitting on the wing, from tip to tip. By actual count, there are 30 on that wing, which makes me wonder how high they pumped up the tires. The point of the advertisement, of course, was to illustrate the strength in that wing—far more than any reasonable pilot would ask of the airplane during normal operations. When you consider that the airplane is not certified as aerobatic, what the manufacturer is telling you is that there is a great deal of margin in that structure. All aircraft have a breaking point; some far exceed others. Generally, the Each pilot has a unique limit, and that limit may vary. Evaluating the aircraft condition, shorter the span, the stronger the struc- mission and weather determine how much margin is needed in a given situation. ture is likely to be, because you will have less bending moment where the wing maneuvering speed and avoid high-G sights probably doesn’t need to fly on attaches to the fuselage. Most wings pulls while rolling. The point we want any given day. If you go out to fly and are built with the capability to sustain to get across with this discussion is that something isn't working, you might be higher positive G than negative, fre- most aircraft have sufficient structural disappointed, but it wouldn’t be a disas- quently by a significant amount. But it margin as long as the pilot operates ter. At the other end of the spectrum, a is interesting to note that in most cases within the specified limits. medical airlift aircraft’s mission may be the wing is not going to be the first part extremely critical; if it doesn't flynow , of the airplane to fail. Backup to the Backup then someone might well die. More often than not, the tail fails Systems design is the next area in which Airliners are usually well enough under overload first, and once it breaks, we find margin, and it is closely tied to equipped that they can complete their the aircraft pitches violently forward, discussions of backup plans, redun- missions even with failed equipment. instantaneously develops a high nega- dancy and even operational margin. Down-checked (unavailable to fly) air- tive-G loading, and the spar fails. Struc- (This is a subject near and dear to me, craft can wreak havoc with a complex tural design is more complex than many which is why it’s woven into this series flight schedule, so redundancy is built people realize, and the loading at which at several points.) We can add margin to in, and minimum equipment lists are a wing may fail depends not just on the our aircraft systems during the design written to allow flight with known straight G pulled with a pitch maneuver, phase, or we can incorporate it later on defects under certain conditions. but rolling moments as well. Without by adding equipment. It’s important to General-aviation homebuilts fall into going into the details of V-G curves and know what you want your airplane to categories depending upon how their charts, suffice it to say that when things do, and also to know what it is honestly owners and pilots think about them, get bumpy you should slow down below capable of doing. It is as unreasonable to but a generalization would be that rarely use a short-range, two-place trainer for must a mission be completed or life and serious IFR cross-country work as it is limb will be at risk. While our upcom- to try and fly aerobatics in a four-place ing vacation in the Bahamas might be traveling machine. ruined if we can’t fly, the risk to life and Either one can probably be equipped limb when we fly without specific equip- to do those jobs, but that doesn’t make ment could be much greater. An honest them ideal (or necessarily safe) for that assessment of the aircraft’s suitability purpose. For want of a better word, for “all-weather” operation needs to be the “criticality” of the mission often made before spending tens of thousands drives the amount of margin built in of dollars to provide a capability that to the systems. By criticality, I mean might be an illusion—or worse, a temp- the importance of completing the par- tation to do something unwise. ticular mission on a given day. For Many Experimental airplanes today instance, a fun flier whose sole purpose are better equipped than the light jets is to run around the local area to see the of a few years ago, and even better than

46 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes above the stall, or below Vne. It might sure will stay that way. Because ceilings be the distance the pilot will stay away and visibilities frequently take a nose- from weather. It may be found in the dive at dusk, I generally won’t trust fore- amount of fuel the pilot insists on hav- casts that indicate marginal VFR at that ing in the tanks upon landing—or once time of day. Frankly, I won’t fly IFR in a the decision is made that the destination single at night because it just stacks one weather isn’t going to cooperate, and it is too many straws upon the camel’s back. time to head to the alternate. Operational As a general rule, if my destina- margin is usually the margin that has tion is going to require an instrument been exceeded when we read an accident approach, I want to always have two report that includes running out of fuel, methods of completing an approach— attempting to fly aerobatic maneuvers or have the ability to retreat to a field below ground level or continued VFR where I can reasonably be assured of into IFR conditions. completing a landing. I will file for a Every pilot has limits. They are dif- destination that is predicted to require a ferent for different people, and even dif- precision approach, but only if I have an some military and commercial aircraft. ferent for the same person at different ironclad alternate. Those who know me Highly integrated EFISes, WAAS times. It is important to always evaluate know that I cancel flights when I don’t GPSes, redundant power systems and current conditions of aircraft, pilot, mis- feel good about them. sophisticated autopilots all make today’s sion and weather to decide how much Margin, in all its forms, is a breath of airplanes much more capable for IFR margin one needs. fresh air in an activity that can sometimes flying. Note, however, that I did not I'll share a few examples—not be filled with tension. In fact, lack of mar- say all-weather flying. My own aircraft intended to be adopted by others, but gin is often directly related to that feeling is superbly equipped for IFR flying in merely to illustrate the concept—that I you get in the pit of your stomach when low-visibility situations thanks to preci- have used in the past. When I am flying you are out of options, and everything sion approach capability, highway in the IFR in a single-engine GA airplane, I needs to go exactly right. An aircraft that sky (HITS) guidance and fully coupled like to leave myself a great deal of opera- always operates on the razor’s edge can be approach technology. Yet the basic air- tional margin. In fact, I generally won’t exhausting to fly, and while at times that frame can’t carry ice, and it certainly fly IFR in a “sensitive” aircraft without can be a thrill, operating at that point won’t survive a thunderstorm. an operating autopilot. By sensitive I all the time is not the way to a long and We all used to fly IFR with steam mean those designs, including many enjoyable life. Look for ways to build mar- gauges and lots of needles that we had homebuilts, that have sprightly han- gin into your airplane, your equipment to mentally transpose into an image of dling. The autopilot is for redundancy and your operations, and know what where we were relative to the established and to ease pilot workload under nor- that margin is and how it can be grown. navigation aids and surrounding terrain. mal conditions. Then relax a little, knowing that you have Today’s systems give us a margin by draw- I am also extremely paranoid about a cushion to protect you if the next worst ing a map, complete with a little airplane fuel. I constantly keep an eye on weather thing happens. J following a purple line. In fact, many (using onboard satellite METARs, airplanes have two such maps, so there is TAFs and NEXRAD radar) to make Paul Dye is an aeronautical engineer and even more margin to help our saturated sure that at all times I have enough fuel multi-time builder. He currently flies gray matter. An extra com radio makes to reach someplace with at least 1000- a Van’s RV-8 and, along with his wife, the communication job easier, as does the foot ceilings or better—and that I am Louise, has just completed an RV-3. ability to monitor more than one active frequency. Fuel totalizers make the management of this important commodity easier and more reliable. The Margin Between Your Ears While the designer and/or builder of an aircraft may provide structural and systems margins, the pilot provides the operational margin, which is that little extra pilots leave to stay inside what they understand to be the limits of the airplane. This might be a margin in airspeed

KITPLANES July 2012 47 maintenance matters Cable classroom. Control cables are overbuilt parts. actuators, the friction drag at the axles of A Typical System They have to be. When a cable connects pulleys and fairleads used to change cable For those homebuilt designs—typically a stick grip or control wheel to a critical run directions, and the force required to high-wing aircraft where a pushrod roll flight control, the safety of the airplane overcome aerodynamic forces at the con- system isn’t quite feasible—a normal is at stake. Fortunately, aircraft-grade trol surfaces and tabs. aileron control system consists of three cables are more than up to the task. The forces are so slight that there cables. Two are called direct cables, and Cable-controlled systems aren’t as might have been a MacGyver episode these are routed from ears on the control common in homebuilt aircraft as they where the clever TV hero removed all stick, or from drums that are rotated by are in production-line machines for a of the primary control cables from his the control wheels, to the left and right variety of reasons. Designers like to keep crashed airplane, bolted them together bellcranks mounted in the wing struc- things simple, and cable designs tend to into one long line and used it to lasso a ture near the ailerons. The third cable is have a lot of extra parts compared to a busload of Third World orphans seconds called a carry-through (or balance) cable pushrod- or torque-tube-based system. before they toppled to certain death in Even so, the vast majority of the popu- a toxic waste dump filled with hungry lar homebuilt designs use control cables alligators and piranha. The cables would somewhere in the scheme, most often have been up to that task. for rudder control. How strong are those cables? Each On the Plus Side aircraft-quality 1/16-inch galvanized steel Aircraft cables are classified as non- cable is manufactured to a minimum flexible, flexible and extra flexible. As breaking strength of 480 pounds— far as I know, only extra-flexible cables strong enough to lift all but the most are used in light aircraft control sys- powerful aircraft-engine assembly. And tems; the others are too stiff for the that’s a size smaller than is normally used direction changes required during for the rudder. cable routing. The primary control cables are typi- Extra-flexible aircraft cable is tough cally 1/8-inch diameter 7x19 cables. These and strong, requires little periodic main- have a minimum breaking strength of tenance, is easy to cut, readily available, 2000 pounds if made of galvanized steel, can be terminated with a wide range of 1760 pounds if made of stainless steel. ends, can be worked on with field tools Stainless-steel cables are used in place of and is relatively stable with regard to the galvanized steel cables in hot, humid temperature. Cables are steel (or stain- parts of the world, where the potential for less), so they aren't as light as the wiring rust is elevated, and in airplanes that oper- in electrically controlled trim systems, 1 ate on floats and/or near salt water. but the weight penalty is offset by the The lower ⁄8-inch extra-flexible cable is Stresses on control and trim cables are fact that there hasn’t been a case of run- terminated with a ball (which is hidden) 1 and a fork end; the upper ⁄8-inch and the low because the resistance-to-movement away trim (an emergency checklist item 3 adjacent ⁄32-inch cables are terminated in forces are slight: the bearing or bushing in electric-trim equipped airplanes) in a cable loops that are swaged after passing drag at the wheels, the bellcranks and cable-controlled trim system. around a thimble.

is what you call a gen-u-ine mechanic, a bonafide A&P with an Inspection Authorization. For- mer West Coast editor for AOPA Pilot and tech guy for the Cessna Pilots Association, Ells has flown and wrenched on a wide range of aircraft. He owns and wrenches (a lot!) on a classic Steve Ells Piper Comanche. But don’t hold that against him.

48 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes and connects the other side of both the left and right aileron bellcranks. These three cables form a closed loop. The loop configuration is easy to understand with a control stick, but it’s a little more difficult to see with control wheels. Here’s how one major light plane manufacturer did it. The left and right control wheels are synchronized by being tied together with a length of extra-flexible aircraft cable that is terminated at each end with an AN 664 single-shank ball end. The ball ends fit securely into little depressions in the left and right control wheel drums before Pulleys are used for control cable changes of direction. The cotter pin installed in the being wrapped for one and a half turns pulley bracket prevents the cable from moving out of position (out of the groove in the around each grooved drum. The left pulley). It’s called a cable guard. and right direct cables are wrapped around these same drums (in different One rigging check is to ensure that adjustments are always a balance of give grooves) and terminate at ball ends both aileron bellcranks hit the aileron up and take. If tension is increased in one that are locked into position in depres- and aileron down stops before the con- cable, it will have to be decreased in one sions on the drums. Each direct cable is trol wheel (or stick) reaches its limit of or both of the other cables to 1) get full wound around its respective drum for travel or control stop. Additionally, con- travel at the bellcranks, 2) have correct one and a half to two revolutions before trol surface (ailerons and elevators) bell- control stick or control wheel and bell- it's routed to the bellcranks. The drum cranks must be centered in travel when crank positioning and 3) maintain proper tie-together cable, along with the direct the control wheel or stick is in the neu- cable tensioning in that system. and the carry-through cables, close the tral position. Finally, the control-cable loop between the control wheels and tension must be adjusted in accordance Tools and Supplies the ailerons. Every cable-controlled with the manufacturer's specifications. You may see reference to a five-tuck flight-control system is made of loops. Bear in mind, too, that some kit designs Navy splice in an old aviation mainte- (And now, perhaps, you see why a push- may deviate from production-aircraft nance book or in a museum (the reddish rod system is so enticing to designers.) norms, so always follow the recommen- coloring is the dried blood of the splicer), dations of the kit manufacturer. but they haven't been used in aircraft Rigging, Tension and Travel As mentioned, each system is a loop, production for many decades. Cable systems are length adjustable so all adjustments on one cable affect Today’s control cables are formed by through the use of turnbuckles. At least all of the components in that system—a swaging the required fork ends, eye ends, one cable in each loop system has a turn- critical point to understand during con- stud ends, turnbuckle ends, eye and fork buckle between two lengths of cable. trol-surface system rigging adjustments. ends, and balls. Aircraft-quality cable The barrel (turnbarrel) of a turnbuckle Let’s look at an example: One day Joe assemblies are made to order from well- is a threaded bronze tube that serves Homebuilder determines that his aile- known suppliers such as Aircraft Spruce & as the length adjustment connection rons are too sloppy, and he decides to Specialty (www.aircraftspruce.com), McFar- between two threaded cable terminal tighten up the cables. He finds a turnbar- lane Aviation (www.mcfarlane-aviation. ends. One threaded terminal has left- rel in an aileron direct cable and turns it com) and independent cable manufactur- hand threads, and one has right-hand to tighten up the cables. As he turns, the ing companies. I found two such compa- threads so that when the turnbarrel is direct aileron is shortened. As a result, nies—California Swaging & Cable Products turned, both cables screw into or out of the aileron bellcrank will no longer be in Company (www.californiaswaging.com) it at the same time. the neutral position when the stick is in and Lexco Cable (www.lexcocable.com)— Cable length adjustments are required neutral. The cable tension numbers will during a quick Internet search. because control-surface systems need go up, but in addition to the bellcrank no Cables can be made locally using a to be fitted for full control-surface travel, longer being in neutral, it's likely that at Kearney M1-K roll-swaging tool, which neutral stick or control-wheel position- least one of the aileron bellcranks will no retails for more than $6000 (used tools ing when control surfaces are in the longer hit the stop in one direction. are available). To be safe, send the first neutral travel position, married control Any change or adjustment in one cable built with the Kearney machine to wheels, correct cable routing and correct cable affects all other cables (and bell- be strength tested before installing it. If control cable tension. crank positions) in that control system, so the cable meets or surpasses the cable

Photos: Courtesy Steve Ells, Marc Cook KITPLANES July 2012 49 maintenance matters continued minimum strength standards, it’s safe be simultaneously prevented from turn- to install. If it doesn’t, the Kearney tool ing. There are tools for this, but I’ve needs to be adjusted, or the swaging found that a piece of a wire coat hanger, dies need to be replaced. bent and inserted into the holes in the threaded terminals, works fine to pre- Nicopress and LocoLoc vent the cable ends from turning. Simple loop end cables and cable splices Earlier I mentioned that cables are are made using oval-shaped copper stable over a large temperature range. sleeves from Nicopress and LocoLoc. It’s common for this temperature effect Tools required to properly compress the to be accounted for in the cable ten- sleeves range from a simple two-part, sion limit table supplied by the airplane bolt-together tool that retails for less than manufacturer. For instance, the eleva- $20 to a compound leverage Nicopress tor cable tension Cessna specifies for its

tool that retails for just under $300. 4000-pound maximum takeoff weight 1 3 Nicopress sleeves for ⁄8- and ⁄32-inch 1 The one tool that must be purchased (MTOW) 210 is 30 pounds +/-10 pounds cables, two AN 100 thimbles (for ⁄8-inch to set the tension on cables is a tensiom- at the average temperature for the area cables) and a 64-CGMP Nicopress crimping 1 3 1 eter, which ranges in price from $200 to where the plane is flown. tool. The 64-CGMP crimps ⁄16-, ⁄32-, ⁄8- and 5 $750. I’ve been using the less expensive ⁄32-inch diameter cables. Burroughs cable gauge for years, and it’s Inspections been satisfactory for small aircraft work. Cables don’t get inspected as often actuation arms. But they must be When turning the turnbarrel (threaded as other control-system parts such as inspected for wear, especially the area of bronze center part) of a turnbuckle, the bellcranks, actuating rods and rod end the cable that is re-routed around a pul- two threaded cable end terminals must bearings, bushings and control-surface ley. The only way to inspect a cable at a Kitplanes subscriber alert! several of our Kitplanes subscribers have received what appear to be “renewal notices” or “automatic renewal notices” from a company known as preMier subscriptiOn serVice, 5star subscriptiOns, rapiD MaGaZine cOllectiOn, MaGaZine billinG serVices, publisHer’s billinG serVices, or other similar names. addresses for these firms include Dallas tX, lincoln, ne, Omaha, ne, san luis Obispo ca, salt lake city, ut and prescott Fl. These firms have nOt been authorized by us to sell subscriptions or renewals for Kitplanes and we cannOt Guarantee that any order or payment sent to them will be forwarded to us. Kitplanes does nOt offer a subscription term of more than 2 years, nor do we retain your bank account information. if you see an offer for 3 or more years or if you receive a notice that references your subscription anD your banking information, it is nOt an authorized offer. We urge you to report these notices to us, as well as to your state’s attorney General and better business bureau. any offer you receive that does not bear our company logo or corporate/customer service address or 800 numbers should not be considered approved by us. the only autHOriZeD inFOrMatiOn for Kitplanes is: toll free via telephone 1-800-622-1065, ebsco renewal telemarketing, or www.kitplanes.com/cs Our texas customer service center: 1-800-622-1065, pO box 8535, big sandy tX 75755 Or our corporate offices at: belvoir Media Group, llc. aviation publishing Group 800 connecticut ave norwalk ct 06854 should you have any questions at all about mail that you receive, please contact us at our website: www.kitplanes.com/cs or call us toll free to speak to customer service.

50 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes Kit ALERT halfpg.indd 1 10/1/11 5:35 PM pulley re-route is to disconnect one end of the cable and pull it clear of the pulley. The most common cable inspection technique is to wrap a shop towel around the cable and slide it over the length of the cable. Broken strands require replacement of the cable. These strands are hard to see when the cable is straight, so a common inspection technique involves bending the cables and using a magnifying glass for a close-up inspection. Hidden internal breaks can often be detected by the sound when the cable is flexed.

Turnbuckles and Safetying The turnbarrel is available in 2½- and These are the four methods of using The safety wire double wrap (top two illus- safety wire instead of spring clips to safety trations) and the locking clip methods (lower 4-inch lengths. Turnbuckles must be safe- turnbuckles. two illustrations) of safetying turnbuckles. tied to prevent loss of cable tension, and there are various methods. The modern the center hole in the turnbarrel before during the wrap sequence. Spiral wrap- method uses clip-locking turnbuckles threading the remaining wire through ping looks like it should be more secure, that are locked with snap-in spring clips. the cable terminal and securing each but it isn’t, so it’s not as commonly used Turnbuckles that aren’t manufac- end. To do a single wrap safety, adjust in the field. tured to accept the spring clips must be the length of the safety wire so it’s cen- wrapped with safety wire to prevent rota- tered in the center hole. Bend one end Tips tion. There are four accepted wrapping 90° at the barrel and thread the end When checking and/or adjusting the schemes—double wrap (spiral) or double through the cable terminal, and then elevator up cable and down cable ten- wrap, single wrap (spiral) or single wrap. bend it back toward the turnbarrel. Pull sions, support the trailing edge of the Each of these wrapping schemes the slack out of the wire before wrap- elevator on a ladder or bench so it’s in a prevents the turnbarrel from turning ping it around the turnbarrel/cable ter- neutral position. by threading one (in the single wrap minal junction area at least four wraps. Make sure you’re taking the system ten- method) or two (in the double wrap Do the same at the other cable terminal. sion reading on the correct cable. In Cessna method) lengths of safety wire through Double-wrap schemes use two wires, single-engine aileron cable systems, sys- but the procedure is otherwise the tem tension is taken on the carry-through same. The main difference is that each cable only; taking a tension off of either wire is captured under the other wire direct cable will yield a false reading. J

Cable-making in process for a GlaStar. Using the right tools is critical for safety. Smaller cables called bridle cables join autopilot servos to the main control cables.

KITPLANES July 2012 51 Don and Sharon Hall’s RANS S-19 Our RANS S-19 was completed in June 2011, after three years and more than 2000 hours of work. All of the interior surfaces were primed, and the rivets were installed wet. We built the project per print, with no aerodynamic, structural or propulsion changes. The aircraft performs per the RANS pilot operating handbook. The control forces and effectiveness of the ailerons, flaps, rudder and stabilizer are excellent. This was truly a joint effort as Sharon did the majority of the drilling, riveting and Dremel work. Special thanks to Definitive Avionics of Bellingham for wiring the avionics and Extreme Metal & Paint of Anacortes, Washington, for the paint job. Many thanks to our EAA chapter members for their help. Much to our surprise, our S-19 was awarded LSA Reserve Grand Champion at the Arlington Fly-In in Washington state. Anacortes, Washington [email protected]

Eric Kallio’s RV-10 After five years of building my Van’s RV-10, N518RV took to the air in February 2010. It was painted in August, after Phase I flight testing was completed. It is equipped with an Aerosport Power IO-540, Grand Rapids EFIS/EIS, Garmin avionics stack and the TruTrak autopilot. It has plenty of power and is a real dream to fly. I’m now coming up on 70 hours and have already made several wonderful trips with the plane. What a great kit! Baton Rouge, Louisiana [email protected]

Craig Walls’ Alaskan Rebel My wife, Debrya, and I recently finished our Murphy Rebel. We spent almost four years building our baby. The first flight took place on September 1, 2011, and it flew smoothly with no need for control adjustments. The panel consists of two Dynon SkyView panels along with an SL40, GTX 327, Sigtronics intercom and an Alpha Systems AOA gauge. Powering our Rebel is an Aerosport O-360 with 180 horsepower. The plane’s empty weight is 1050 pounds. Believe me, the performance is very good! We painted the exterior with Stewart Systems paint and were amazed at how easy it was to use. We also used Hoerner-style wingtips made by Dave Fife specifically for the Rebel. These are a performance mod that lowers the stall and increases top end speed. I get a thrill every time I go flying, knowing that we built the airplane ourselves. Factory support was helpful, but we could not have done this without the guys in the Rebel builders’ group and our friend, Si Smith. Next on the list is to get started on those amphib floats so we can really explore Alaska! Wasilla, Alaska [email protected] J

Submissions to “Completions” should include a typed, double-spaced description (a few paragraphs only—250 words maximum) of the project and the finished aircraft. Also include a good color photograph (prints or 35mm slides are acceptable) of the aircraft that we may keep. Please include a daytime phone number where we can contact you if necessary. Also indicate whether we may publish your address in case other builders would like to contact you. Send to: Completions, c/o KITPLANES® Magazine, P.O. Box 315, Ashland, OR 97520. Digital submissions are also acceptable. Send text and photos to [email protected] with a subject line of “Completions.” Photos must be high-resolution—300 dpi at a 3 x 5 print size is the minimum requirement. You may also submit electronically at www.kitplanes.com, just click on “Completions: Add Yours” in the upper right corner of the home page.

52 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes Just about every kit aircraft is custom. In the beginning, every kit is basi- This is the curse of the kit airplane cally a bunch of big crates full of parts. It builder. Due to sheer exposure, whether doesn’t matter whether you are building at events or via online forums such as an RV-12 or a Murphy Moose, your new- the Matronics listserv, (www.matronics. est project will arrive in your driveway in com/listbrowse) you may be left wanting a big, beautiful box. to make a few improvements. This is one Your first task will be to inventory of the ways kit aircraft rapidly differenti- everything in those boxes to make sure ate themselves from their original design that you have received all of the compo- and from others of the same type. nents necessary to construct your air- Builder/owners want their machines plane. Once you know you have it all (and to go faster, farther or higher, or just run trust me, you probably will put in a call more efficiently. Their passengers want to your kit manufacturer to request some to be more comfortable and suitably inane bolt or package of screws that was distracted on those long, high flights to left out in packing), it is time to organize faraway destinations. The big metal spinner and Sam James your workshop and get to building. Every kit builder has his favorite mods. cowl mods give the nose of the author’s Van’s RV-10 a distinctive look. That’s how it all starts. If you make Some of these correct issues with the it through the arduous process of con- original design, but most are add-ons, airplane to the runway after Sun ’n Fun struction, you should find yourself box- accoutrements and just generally good because it wouldn’t idle that long with- less but aircraft-happy at the end of the sense. A few aren’t smart at all. out overheating. A fine Sensenich wood project. One day you’ll be flying your air- I only have experience with the two two-blade propeller (76 inches) and all plane, and, probably after a bit of tweak- wildly different kits my husband brought the aforementioned mods have turned ing, you’ll love it. home: a two-place taildragger Kitfox IV the engine-airframe combination into Then comes that first or second fly-in, and a four-place trigear speedster, the one that works extremely well. where you’ll park your beloved aircraft on Van’s Aircraft RV-10. Both of these aircraft A few years later our daughter the line with maybe a half-dozen or more are fairly custom at this point. expressed an interest in learning to fly. variants of the same kit, and the compari- My husband and I are both flight instruc- sons and knowledge swapping will begin. Kitfox Mods tors, but we weren’t comfortable teach- You’ll notice the blue one has different It’s easy to point out my favorite mods. ing her in an airplane with bungee gear air intakes than yours, or a totally differ- The Kitfox got a new engine, the Jabiru that would not accept much of a side ent system for latching the cowling. The 2200, an 80-horsepower, direct-drive, load. Student pilots are notoriously green one over there might have sweet four-cylinder model, in 2000. I love it hard on landing gear, so we changed recessed door handles. And the orange now. But for the five years it took to out the Kitfox IV’s traditional landing one? It has air conditioning and dual LCD work out the kinks in the systems, find gear for Grove’s one-piece spring-alu- screens for gaming in the back seat. That’s the right cylinder heads and plenum minum landing gear. This was a mod when you may find yourself comparing for cooling, and reform the cowling to that just worked from day one. The gear notes and salivating over the latest mods work with it, I hated it. The engine-air- is designed to bolt right onto the hard that could make your airplane a bit finer frame combination was so bad in the points already on the airframe fuselage than all of the others. beginning that we routinely walked the and are rugged like Cessna 150 landing

has taught students how to fly in California, Texas, New York and Florida. She’s towed gliders, flown ultralights, wrestled with aerobatics and even dabbled in skydiving. She holds an Airline Transport Pilot rating, multi-engine and single-engine flight instructor ratings, as well as glider and rotorcraft Amy Laboda (gyroplane) ratings. She’s helped with the build up of her Kitfox IV and RV-10.

Photos: Amy Laboda KITPLANES July 2012 53 continued gear. About the only thing lost in the deal and replace than the stock wheelpants. of cowling mods for the RV-6/7/9, did not was an inch of ground clearance with the We dislike them because they are low to scale up well. James still sells plenums for propeller, but there’s still 17 inches. the ground and require custom chocks the IO-540. What is my fantasy mod for this air- (we carry our own) and are not good for While we were building, the issue of plane? A Rotec 110-horsepower radial flying off of grass. The nose wheelpant RV-10 doors popping open and depart- engine, but that’s not going to happen in is a little wider than stock, and just wide ing the airplane became quite real. The my lifetime. It sure is pretty, though, and enough that a “universal” tow bar doesn’t latching system was originally seen as makes a great sound. fit well, which means the airplane can- one of the primary culprits. The human not be towed easily into a parking space verification system, however, ultimately RV-10 Mods when we are on the road. I either do a lot seems to be the issue. Van’s Aircraft The RV-10, befitting its complexity, sports of pushing or demand that the FBO mar- has provided a service bulletin on the many more mods that take it away from shal me into my long-term parking spot. subject, so the original stock latching factory stock, and not all of them are The cowling is marvelous because system also remains suspect. Many favorites (though for the moment, all of it slopes down just a bit more than the different solutions for the problem them work). stock cowl, offering better visibility over were developed, from magnetic door Anyone following this column knows the nose. It also looks great with the “closed” sensors to three-point lock- that our RV-10 sports a Sam James cowl- round air intakes and the big metal spin- ing systems. Some, such as the Plane ing and wheelpants. We like these wheel- ner on the prop. The cam-lock latching Around kits, include longer pins plus the pants because they are easier to remove system is rugged and works better than third, bottom tongue-in-groove lever the stock “piano hinges.” That said, it and a 180° travel. took us five tries to get the plenum and We decided to change the nylon air-intake/air-outflow system to cool blocks that the door pins thread through properly—five tries over three years, or to aluminum ones, which are honed to maybe four. I’ve lost count. Sam James guide the pins into place. We also left has recently decided not to sell the mod our door-pin rods slightly longer so that for the RV-10 anymore. He provided they’d have a little more grip. We added excellent customer support to us, so we secondary rear handles for pulling the have no beef with him. I just think these doors closed, as well as simple straps cowlings, derived from his successful line to help snug the forward portion of the

The Motopod mod allows you to carry a The original design for the nosewheel installation on the RV-10 was flawed and failed on full-size motorcycle with you for transpor- the first flight, ruining the fork, axle and tire. tation everywhere you go.

54 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes door to the fuselage. Finally, addressing the human issue, we created a checklist that ensures the doors are latched. My verification system is my hand—I can touch each door pin after the door is latched because we’ve left those side panels off of the interior finish in the airplane as a nod toward function over form. There is nothing more reassuring than actually touching the door pin in its latched position. At least one other mod, the axle on the nosewheel, should have been completed before our airplane ever flew. The stock nosewheel configuration on early RV-10 kits had issues. We subscribed to TCW makes a backup battery to back up your backups. You can’t have too many in an the Matronics list, so this was not a state airplane that relies on critical electronics such as EFISes, autopilots and engine monitors. secret. Still, we didn’t change out our axle. Maybe it was because we were eager to back seat. Our passengers are welcome airplanes out there in the world. But is finish, and we were so close. But looking to bring along a tablet or iPad for that. customizing your aircraft the best way back now, it was just stupid. There was And I don’t anticipate installing eyeball to go? Our experience suggests both a known issue and we didn’t address it, vents back there, either. I guess we won’t yes and no. and the nosewheel bearings froze on the be winning any static display awards, but Almost every manufacturer you talk to first takeoff, meaning that the nosewheel that’s OK. I want to keep our airplane light at a fly-in will tell you the stock aircraft is did not spin on the first landing, ruining and simple, and all of the mods I mention perfect for your needs. But we know that’s the tire. Frankly that landing was a tes- add weight or complexity, or both. probably not true. Generally, the kind of tament to the strength of the nosegear, The more complex the airplane, person who will build an airplane wants even though the damage that ensued the more mods you can find for it. I it to be just a little different, just a little from the landing required replacement researched more than two dozen com- better than everyone else’s. That is their of the fork, axle, wheel and tire. We got mon mods for the RV-10, and another nature. Most of the mod-makers, by the the front axle mod from Matco. Since dozen uncommon ones. I bet if I’d had way, are kit builders who believe they’ve then, we’ve dealt with shimmy issues at more time I could have found a dozen found an improvement. Are they all truly certain taxi speeds. We recently relieved more—and all of them are flying on improvements? That’s for you to decide. J some of the material on the seal between the wheel and the bearing to combat that, and we’re testing that now. So far, so good. These aren’t the only customiza- tions we’ve made on our airplane that move it away from stock equipment. Other mods include Electroair electronic ignition and subtle changes to the cabin-heating system. We use TCW’s Safety-Trim system for both our elevator and rudder trim, and TCW’s backup battery system.

What We Won’t Do We probably won’t be seen with air conditioning, any fancy overhead panels or a permanent oxygen installation. We definitely aren’t interested in adding outboard fuel tanks, either. (The airplane’s range is about what we can tolerate.) There will be The author did not like the original trim system on the RV-10, so it was modified for both no built-in LCD panels for gaming in the rudder and elevator, with the TCW Safety-Trim system.

KITPLANES July 2012 55 Aeatilt rn ve enegs r ie Solar-powered AC: big, slow and expensive. Why would anyone want to fly a solar- met with only 26 square feet collecting and have batteries to store energy powered airplane? The challenge of tak- that sunlight. gathered over periods longer than their ing to the air in a solely solar-driven craft is That is, the requirements could be met actual flight times. Let’s start small and rarely overcome, and only with airplanes if the sun struck that surface straight on, as work up. that are tenuous in their abilities at best. if noon lasted all day. Most of us don’t live But you’d have to see the beautiful pic- on the equator, and sunlight hits us with The Sunseekers tures Eric Raymond took while crossing a glancing blow. Weather intervenes, and Eric Raymond was an early adopter of the Alps and overflying the Matterhorn, clouds cut down on available photons. solar technology, flying his incredibly or view the images of a crowd in thrall to Solar cells, at least commercially available light Sunseeker across the United States the giant Solar Impulse gracefully travel- ones, aren’t all that efficient, and even in 21 hops from San Diego, California, to ing the length of the main runway at the the best research models lose 60% of the Kitty Hawk, North Carolina, in 1990, an Paris Air Show, to understand the charm available energy. amazing story that I read about on pages of such machines. You may then be smit- A Light Sport Aircraft, for instance, A16 and A18 of the local paper over two ten with the desire to own one yourself, with 100 square feet of solar cells on its days of that flight, despite what Raymond despite their limits. wing, could collect 10,000 watts if the described as a “media circus” to EV World One limit is collecting what would sun were directly overhead. But the best about his experiences with the press. The otherwise be an illimitable power solar cells would use only 4000 of those two longest legs of his flight had covered source. Every day, all day, the sun pours watts, hardly enough to stretch the glide 100 watts of energy per square foot of the on the average small plane, let alone give earth’s area on us. That’s about 438 kilo- it the typical Rotax’s 100 horsepower watt hours per year for each square foot, necessary for takeoff. based on 12 hours of sunshine per day. All three currently flying solar aircraft The average American home consumes are very big (to give enough wing area to about 936 kilowatt hours each month, so gather sufficient sunlight), exceedingly the year’s energy requirements could be light (to allow flight on limited power),

Eric Raymond displays the World Air Games gold medal for Best Experimental Aircraft. He also won world altitude and Sunseeker II nears 20,387 feet for a world solar-powered record. duration records.

A technical writer for 30 years, Dean has a liberal arts background and a Master’s degree in education. He writes the CAFE Foundation blog and has spoken at the last two Electric Aircraft Symposia and at two Experimental Soaring Association workshops. Part of the Perlan Project, Dean Sigler he is a Private Pilot and hopes to get a sailplane rating soon.

56 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes Thin, smooth Duo solar cells will enable Raymond finds the only shade in Almeria, Spain. the first two-seat solar aircraft to soar. about 254 miles each—a record for over Not finding a great deal of financial medal. Subsequent flights have shown two decades—and his 16,000-foot alti- support in his native land (the U.S.), Ray- the soundness of the design and given tude remained unchallenged for years. mond went to Europe and found sup- him the impetus to develop Duo, a two- Structural weight for Sunseeker was port in Switzerland, Poland and Slovenia seat solar-powered airplane that might a feathery 100 pounds. NiCad batteries with Sunseeker II, a slightly larger, more reach series production. added 35 pounds. The ship totaled less powerful version of the basic design Its stats are a bit amazing. A 72.2-foot (22- than 200 pounds with amorphous, low- with more efficient monocrystalline solar meter) span, covered with 22%-efficient efficiency solar cells producing 1800 watts cells, a bigger motor and lithium batter- solar cells, powers and lifts a 594-pound air- and a 2.5-horsepower brushless motor ies in place of the original NiCads. plane, which, even with two large passen- torquing a folding propeller. He had He displayed Sunseeker II at the gers, still weighs only 1034 pounds. The low observed and learned much about keep- Friedrichshafen Aero Expo in 2009, wing and span loadings allow a 20-kilowatt ing it light from German solar pioneer winning well-deserved plaudits from motor to fly its lucky occupants on the rays Günter Rochelt (see sidebar, Page 59). the crowd and a Best of Show award. of the sun. We can look forward to seeing Sunseeker could take off using battery Leaving Germany, he flew over the more on this amazing creation, maybe in power, which in this instance was really Alps, crossing Switzerland and overfly- time for this year’s Aero Expo. stored sunlight. One of Raymond’s objec- ing the Matterhorn, one of his lifelong tives was to avoid using any grid-based ambitions. At the Experimental Soar- Icaré 2 power in his flight across the U.S., some- ing Association Western Workshop that Careful observers may be startled at the thing he achieved, maintaining altitude on year, he told about flying under some similarity of Stuttgart University’s Icaré 2’s solar power alone and recharging the small high clouds that limited his power wing to that of the Sunseeker Duo. Pro- battery packs from excess sun energy col- output and made crossing into Italy a fessor Rudolph Voit-Nitschmann allowed lected. In many instances, especially the dodgy business. Sunseeker was a big Eric Raymond to “borrow” the jig on which longer flights, he relied on thermals and hit at the World Air Games in Turin, Icaré’s wing was constructed (though soaring to make his day’s distance. where Raymond was awarded a gold Raymond has reduced the area since first

Sunseeker I, the airplane in which Raymond crossed the U.S. in 1990. Duo wing construction shows an ultralight approach.

Photos: Courtesy Solar Impulse, Francis Demange & Stéphane Gros; Eric Raymond; Icaré 2, Mario Hytten, Planetaire KITPLANES July 2012 57 ALTEATI RN VE ENEGS R IE continued

Klaus Ohlmann with his record-setting mount, Icaré 2. A mechanic checks the health of Icaré 2’s solar cells. starting construction because more effi- Jochen Ewald, the pilot in Icaré’s early 40 minutes, so longer flights require cient solar cells became available). stages, described the big plane’s charac- bright, nearly cloudless days. That type of Other figures are similar. Icaré’s wing teristics, which are leisurely to be sure. weather helped Klaus Ohlmann, already area matches that of Sunseeker’s Duo at “The best glide angle is about 40:1 at the holder of 38 soaring records, establish 269 square feet (25 square meters), with 61 kilometers per hour (38 mph), which the first FAI-certified accomplishments 82% of that (221.7 square feet or 20.6 gives nice, but slow, progress if the wind for solar flight last year in the southern square meters) covered with solar cells. is not too strong. Stall speed is 45 kilome- French Alps. Two were for flights of more It weighs only 580.8 pounds (264 kilo- ters per hour (28 mph), with the big glider than 229 miles (370 kilometers), not quite grams), of which only 440 pounds (200 going into a stable, shaking stall. During as long as Eric Raymond’s 1990 unofficial kilograms) are structural. The remaining the flight tests, the big flying tailplane distances, but the first to be given official pounds come from the motor, propel- got a curved end to improve longitudi- recognition. His last attempt on Septem- ler, solar cells and four battery packs. Its nal stability. Without this, flying her must ber 10, 2011, was a clear record, though. sink rate of a little under 1.25 feet (0.39 have been quite exhausting,” he said. Traversing 272.4 miles (439.3 kilometers) meters) per second would leave it hang- “To compare the Icaré 2 with today’s around three pre-declared turn points, ing in the air on a warm day. still-flyable gliders, the Slingsby T-21 (a he reported being able to out-climb an Although it is powered by a 12-kW, pre-WW-II training glider) may be used: LS-4 and ASH-25, both high-performance 92%-efficient motor, it requires a mere At about 60 kph (37.2 mph) the Icaré 2 sailplanes, on his first “training day” in 1.8 kW to maintain level flight. The behaves like a T-21 flown close to mini- the plane, while also making a 234.4-mile 915-watt-hour batteries can manage to mum speed, but not so handy!” (378-kilometer) trip. fly the airplane 20.9 miles (33.6 kilome- Without solar help, the batteries Even Rudolf Voit-Nitschmann, heading ters) if the solar array is disabled. could keep the big aircraft up for about its development, had managed a grand

Ohlmann enjoys his record flight.

58 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes Icaré 2’s design team (l to r): Rudolf Voit-Nitschmann (project leader), Len Schumann and Steffen Geinitz. The same team worked on e-Genius, the second- place Green Flight Challenge finisher. flight in 2003. According to Deutsche Welle, “The Stuttgart University profes- sor steered his glider, the Icaré 2, north- wards. Five hours later, he landed at Jena, in the German state of Thuringia. He’d flown a distance of some 220 miles.” It has been honored before, garnering Icaré’s full complement of solar cells still falls short of the 12-kW motor’s demands. the 1996 Berblinger Prize, awarded for its reported ability to take off and sustain The power of a scooter: four 10-hp plastics maker; the Schindler Group, a flight on solar power alone without using engines. Swiss elevator and escalator manufac- its batteries. It picked up three big awards Visionary thinking… turer; Omega watches and Deutsche in 1997: a special achievement gold medal Visionary enough to conceive an Bank, the Solar Impulse group also at the Experimental Aircraft Association around-the-world flight in a solar-pow- reaches out to smaller contributors. I fly-in, the Gold Daidalos Medal from the ered airplane, flown in stages by project purchased solar cell 1776 near the left Braunschweig English Aero Club and the founders Bertrand Piccard and André wing aileron gap to honor my late wife, OSTIV (Organisation Scientifique et Tech- Borschberg, the team that designed, granddaughter and two high-school nique du Vol à Voile) Prize. constructed and has flown this dragon- buddies, and perhaps to symbolize Not incidentally, Eric Raymond and fly-like behemoth, and has applied large- our future independence from fossil Klaus Ohlmann flew the second-place ness in grand style. fuels. There are more cells, claimed and Green Flight Challenge e-Genius. With The project involves enthusiasm, unclaimed—10,748 on the wing and two experienced solar navigators in the innovation and audacity. Backed by 880 on the horizontal stabilizer—pro- same cockpit, the flight probably ben- groups such as Solvay, a chemical and viding ample opportunity for people efited from their knowledge of using low power to the greatest advantage. Ohlmann’s recent flights are not the last of solar records. A huge Swiss air- Günter Rochelt’s Accomplishments plane may soon sweep those away. Günter Rochelt designed, built and flew an amazing array of hang gliders and human- and solar-powered aircraft before his untimely death in 1998 at the age of 59. Eric Raymond says, Solar Impulse “Günter Rochelt contributed a vast amount of groundbreaking technology, still being used, to Their web site sums up the extremes of make solar powered flight possible. His 52-pound Musculair II showed what was possible for the Solar Impulse: low-powered flight.” It also became the inspiration for Raymond’s initial Sunseeker. Rochelt The wingspan of an Airbus A340: 208 was the first to fly a human-powered airplane with a passenger onboard. He was apparently not feet (63.40 meters). only a genius in aerodynamics, but a very fit person. There will be more on Rochelt’s achieve- The weight of a family car: 3520 ments in an upcoming article on the backstory of electric flight. pounds (1600 kilograms). —D.S.

KITPLANES July 2012 59 ALTEATI RN VE ENEGS R IE continued

Trusses resemble those for a really big homebuilt, but in carbon Workmen mount motor to mount, which also holds 70 batteries fiber. and the motor controller. to memorialize loved ones or to simply The nearly 2152 square feet (200 square This was followed by flights from home encourage this adventure. meters) of 12% efficient, 145-micron- base in Payerne to Zurich and Geneva, Bigger contributions can earn a thick solar cells provide each motor where the big plane mingled with the Air- guided tour of the airplane or even a about 6 kilowatts, or 8 horsepower, to buses and Boeings on a more than equal “Your Name Here” opportunity to have propel Solar Impulse. More efficient cells footing. In June 2011, it went to Brussels, your message emblazoned on the craft would weigh more and “penalize the Belgium, overflying four countries on the during future flights. airplane during night flight,” helping way. Staying in Brussels for nearly a month, Structurally, HB-SIA’s interior land- explain the necessary compromise. it was the centerpiece of meetings with scape resembles that of a large model Even the huge number of cells does European Union dignitaries before depart- or homebuilt aircraft, but everything is not provide power at night, and a major ing for the Paris Air Show. There, it was an gargantuan, and in place of steel tub- part of the mission is eventually to fly early-morning sensation as it cruised the ing or wood, carbon fiber abounds in night and day on long, slow cross-coun- length of le Bourget’s main runway. great trusses. tries; 880 pounds (400 kilograms) of The team’s blogger captured the 10 a.m. Its motors, Swiss industrial units, are batteries, or “more than a quarter of the flight. “Everyone held their breath. The geared to drive the 11.48-foot (3.5-meter) total mass of the plane,” carry the load propellers started turning and the plane propellers at a stately 400 rpm. Power during dark hours. This has already been was airborne in less than 10 seconds…The pods under the wings each house a demonstrated by a 26-hour, 10-minute, public was stunned. There was thunderous motor, controller and 70 “accumulators,” 19-second flight on July 7, 2010, with applause. After a week of enjoying fabu- or batteries. Borschberg at the controls. lous displays, sometimes spectacular, but

HB-SIA literally catches some Belgian rays.

60 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes Solar Impulse overflies the U.S. Air Force at the Paris Air Show. always noisy and polluting, Solar Impulse suddenly offered an astonishing alternative solution. HB-SIA soared above their heads slowly, majestically and silently.” Structurally, aerodynamically, electrically and almost spiritually, Solar Impulse has captivated its home country, and videos on the web site show proud citizens gazing skyward as the stately craft glides quietly overhead. Work is now under- way on a second, larger airplane that will be capable of that much-anticipated around-the-world flight. All of these aircraft show ingenuity and dedication to an almost quixotic cause, and all have the ability to inspire those who see them. These are not the first designs to explore the sun’s ability to carry one aloft, or to fly on electric power. A future article will review those who started all of this, some more years ago than you might believe. J

Bertrand Piccard, André Borschberg (Solar Impulse) www.solarimpulse.com Eric Raymond (Sunseekers) www.solar-flight.com

Günter Rochelt (Solair II) www.solair.de www.delago.com/solair/EHome. htm (a more detailed look)

Klaus Ohlmann (Icaré 2) http://icare2records.com Leveraging your fun. The Sport Pilot and Light Sport Aircraft certified in the standard category air- and less complex, the FAA introduced the (LSA) regulations are by no means a per- craft world is based on rules and sys- concept of the driver’s license medical. fect set of rules. But truth be known, the tems cobbled together shortly after The idea is that if the state believes you are rules could be a lot worse than they ended WW-II. The LSA manufacturing com- medically fit to drive a two-ton wheeled up being. In fact, some of the ideas are munity, along with the FAA, has shown vehicle at high speed, in close formation downright brilliant and are being consid- that there is in fact a more streamlined on interstate highways, and through highly ered for other areas of the FAA’s vast regu- way to do business that reduces costs congested cities while loaded with family, latory multiplex. Two areas getting a lot of and brings new products to market friends and strangers, then you are also press lately are consensus standards for safely, and more economically and OK to fly an LSA with one passenger. That aircraft and the driver’s license medical. quickly, than the old-school FAA way. seems reasonable. Manufacturers of larger general avia- By producing industry-accepted con- In fact it has turned out to be quite tion (GA) aircraft are interested in the sensus standards and making manufac- reasonable. Since the Sport Pilot rules consensus standards rules designed turers responsible for adhering to those became active in 2004 through 2011, for LSA because the rules reduce the standards, things are working out well. there have been no accidents in those cost of getting aircraft and associated As pilots get older, one of the dreaded aircraft attributable to a pilot medical products certified. The process for get- fears is losing their medical. In the Sport deficiency. That not only shows the wis- ting both simple and complex products Pilot world, where aircraft are slower, lighter dom of the driver’s license medical, it has also motivated the EAA and the Air- craft Owners and Pilots Association (who were in turn motivated by their members, I suspect) to submit a request for an exemption to the regulation requiring Private Pilots to hold a third-class medical in order to exercise their Private Pilot privileges (§61.23). But there is yet another great thing about the Sport Pilot rules that is head and shoulders above the Private Pilot rules, which is the ability to move from category to category of aircraft without having to recover unnecessary training ground.

Acknowledging the Sport in Sport Pilots One of the things I have observed in the ultralight and Light Sport world is that pilots of lighter aircraft seem far more There are so few examiners in the gyroplane world that many gyro pilots first become adventurous than their GA counterparts. fixed-wing pilots and then quickly transition to what they really want to fly. While many “real” pilots seem to balk at

is the technical editor for Powered Sport Flying magazine (www.psfmagazine.com) and host of the Powered Sport Flying Radio Show (www.psfradio.com). He is also a Light Sport repairman and gold seal flight instructor for Light Sport Aircraft as well as the United States delegate to Roy Beisswenger CIMA, the committee of the Fédération Aéronautique Internationale (FAI) pertaining to micro- light activity around the world.

62 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes the idea of flying anything other than a Pilot rule, which really has no additional relatively substantial airplane, ultralight regulatory minimums for transitioning to You Are Already An Elite and Sport Pilots often fly more than one other aircraft. Member of Society kind of aircraft. The opportunities for Instead, the Sport Pilot rules place the People in the U.S. (2010): 308,745,538 adventure include airplanes, trikes, sky- responsibility for determining how much diving, hang gliders, paragliders, pow- training is needed not on the pilot (who Certificated Pilots in the U.S. (2010): ered paragliders, powered parachutes, may not be objective) nor on the regula- 508,469 (1 out of 607 people) hot air balloons, gyroplanes and a vari- tions (which is a bit too one size fits all), Sport Pilots in the U.S. (2010): ety of other aircraft. Oftentimes a pilot but on the flight instructors who are pro- 3682 (1 out of 83,852 people) will start flying one kind of aircraft and viding the training. The way that it works migrate to another either for a change of is that there is a check and a double- Source: U.S. Census and FAA pace, a change of mission (transportation check because two flight instructors are versus low and slow) or just for the addi- involved in the process. The first provides have obtained a rating in any category tional challenge. the transition training. When the first of aircraft, your second aircraft rating will As it turns out, ultralight flying offers instructor is satisfied that the student is be much easier to get. Still, for the sake the greatest flexibility for lateral migra- competent in flying the new category of of time and money, it is best to learn to tion among different aircraft categories. aircraft and can pass a proficiency test, fly the kind of aircraft you know you will There aren’t any FAA training require- he recommends the student for that want to fly for a couple of years. That may ments at all for ultralights, so pilots test. The student then visits a second mean trying out a few different aircraft need only get the level of training that instructor to take the test and receive the and instructors, but it is well worth the they believe is appropriate. That doesn’t endorsement to fly the new aircraft. investment to go on a tasting tour before always work out because often pilots The system is elegant because it you commit to a specific aircraft or train- approach light aircraft with a lack of doesn’t require the student to take any ing program. understanding, either because they extra steps for bureaucracy’s sake. No If you have already invested a lot of already fly more complex aircraft or additional ground school, no knowledge time and money into a rating and are because they know nothing about avia- test and no minimum hours. Making it thinking about moving to another air- tion except that ultralights don’t require even better, the student doesn’t have to craft category, give serious consideration training. That lack of understanding visit a Designated Pilot Examiner (DPE) to first finishing the rating you are work- results in a lack of flight training, which to get the new endorsement. A properly ing on. While all flight training has appli- can ultimately lead to bad times, an rated (and easier to find) Certified Flight cability to other categories of aircraft, the ambulance ride and a price tag far higher Instructor (CFI) will do just fine. That FAA doesn’t value it much unless you than any flight training might have been. places some additional responsibility on complete the training and get the rating. The Sport Pilot rule struck a great the CFIs, but that is a good place for the So if you are close to finishing your air- balance between safety and required responsibility to be. plane Private Pilot rating and decide that training for people transitioning aircraft powered parachutes or gyroplanes are categories. For example, if you are a Pri- Assessing Where You Are really what you want to fly, your training vate Pilot transitioning from airplanes The first thing you want to do when expenses for your true love may be a lot to a Private rating in rotorcraft, you have considering a new challenge is to assess less if you follow through on your initial a lot of dual training and solo flying what you are already flying. This discus- training and get that airplane rating first. requirements to meet, which can make sion is geared toward transitions, but I If you are an accomplished ultralight the price of transitioning to a new aircraft would like to point out some strategies pilot, the advice is actually the opposite. expensive. Contrast that with the Sport for aspiring pilots as well as pure ultra- If you already fly trikes, powered para- light pilots. I get a lot of calls from both chutes, ultralight airplanes or whatever, groups. Sometimes the aspiring pilots realize that your time in those aircraft Night Flight Training have been student pilots in the past and really doesn’t apply to a rating anymore. have completed a large chunk of training That being the case, you will have to go If you are transitioning from Private and quit for one reason or another. through all of the requirements that a Pilot-Airplane to Private Pilot-Powered If you are brand spanking new to avia- non-pilot would to get the rating. That Parachute, Weight-Shift Control Trike or tion, you have a clean slate to work with. can be both frustrating and wasteful Gyroplane, realize that you are going to The strategy for you is to simply deter- if you are already a competent aircraft have to receive night dual training in your mine what it is you want to fly. What operator. Consider learning something new category to earn the rating. Yes, you you want to fly depends on a variety of completely different. may have tons of night-flying time already, factors that are beyond the scope of this If you are a powered parachute or but you are about to get some more. article, but which are important to con- powered paraglider pilot, learn to fly sider. The good news is that once you airplanes. Ultralight trike pilot? Take up

Photos: Roy Beisswenger KITPLANES July 2012 63 continued gyroplanes. The idea is to make that gyroplane instructors within 100 miles you want to transition to. Unlike single- FAA-mandated training time count of each other can be a challenge. engine airplane CFIs, other training spe- for something instead of going over cialties can be rare, with many of them ground you are already familiar with. Determining Your Kind of numbering less than 100 nationwide. After you have earned your first rating, Flying Combine that with conflicting work it will be easy to transition back to your It is important, though not critical, to think schedules (not just yours; most sport first love. The risk you take is that you about what kind of flying you want to do CFIs have a day job), seasons, weather may find a second love! in your new aircraft category. That’s where and equipment availability, and you may And what if you are already a Private the limitations of Sport Pilot may kick in. If have a challenge ahead of you. Pilot with a single-engine land rating? you enjoy flying at night, Sport Pilot is not That makes the tasting tour even more For you, the Sport Pilot world is your for you. If the only airplane rental at the important. Try to research your new air- oyster! First off, if you want to fly one of local airport is a Cessna 172, you can’t fly craft as carefully as you can before you the brand new LSAs, you don’t have to that with a Sport Pilot license either. That commit to training or—heaven forbid— do anything regulation-wise unless you doesn’t mean a Sport Pilot rating can’t be an aircraft purchase. Most CFIs offer intro- haven’t been flying for a while and need a steppingstone to a Private rating. How- ductory training flights and those can be your biennial flight review. Of course, it ever, you should make sure that your CFI very instructional indeed. You may learn also makes sense to get checked out in is authorized to train at the Private Pilot that the new aircraft is everything you your new airplane, even though your level. If the CFI is, then your training time ever wanted out of aviation, or you may insurance company may be more con- will count not just for your Sport Pilot rat- find that it really isn’t your cup of tea. cerned about that than the FAA is. ing, but also for your Private rating should Either way, the price is well worth it. Life is also good for those with any you choose to pursue it. The good news kind of rating who want to change to is that if you are already a pilot, you will Spread Another Set of Wings a new category of aircraft. Remember, already have a good idea about what Ultimately, taking on the challenge of all you have to do is get trained up to kind of flying you want to do. earning a rating in another category of checkride standards by one CFI and aircraft turns you from an elite, one out get the proficiency check from another Your Opportunities of 600 kind of person to something like CFI. The only common-sense caveat is The biggest decision to make is what to a one out of 80,000 kind of person in the that both of those CFIs need to be CFIs fly. The sport aircraft world actually offers U.S. You are already special (your mom for the aircraft you want to fly and are a wider variety than general aviation. The explained that to you years ago), but you training for. That is not always com- other side of that coin is that training can can become even more special by learn- mon. For example, finding two powered be a little more difficult to obtain. Be ing to fly something many people don’t parachute, weight-shift control trike, or ready to travel depending on what it is even know exists. J

Do you want to keep up with your friends on their cross-county trips? Transitioning to an LSA offers all of the modern con- veniences and a speed increase over the other categories.

64 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes Anatomy of a modification. The heart of homebuilding has while the perfect airplane has not yet pre-stamped, some skin panels are always been innovation. The Wright been invented, the plans or kit that we already curved (but not trimmed), and brothers from Ohio were innovators are building from probably has been most of the necessary welded parts when they built a motor light enough flown successfully at least once (cer- are supplied in raw form, ready for fin- for their fragile glider-based flying tainly the assumption for a kit; if you’re ishing. The design is successful and machine to lift, and their unique idea of building from drawings, you might be has many successors, with more than three-axis control allowed them to not building the prototype!). Therefore, the 7600 examples of RVs flying around the only take it aloft but return safely to the basic design should work. If we decide world. While the design of the wing was earth. Today’s homebuilders are no less that we can do better, it is important updated in the 1990s, the rest of the interested in innovation. The idea of to go through a process to determine kit has been left much as it has always trying out new ideas to make their new if a) our new design or idea will be an been, with few changes to the fuselage airplanes more efficient, faster or more improvement over what was provided or tail. The change I was contemplating maneuverable is almost irresistible when with the kit, and b) there are any nega- was to the fuel-tank vent system. you consider the “plain vanilla” airplanes tive aspects to the modification we Of all of the modifications you can make available from the certified manufactur- want to attempt. to a kit aircraft, fuel-system modifications ers. Plans and kits abound, but many like get my attention most quickly as a techni- to tweak and change them as they build Modifying the RV-3 cal counselor. More new airplanes come and, frankly, that is why many of us are As an example, I’ll describe the process I to grief due to fuel-system problems involved in this unusual pursuit: We want went through on a recent change to the on their first flight than almost all other to do our own thing. RV-3 that we completed not too long mechanical problems added together. But (you just knew there was a but, ago. The RV-3 was the first in a line of In my experience, fuel systems should didn’t you?) we need to make sure that kits to come out of Van’s Aircraft. The be as simple as possible to provide the when we modify an existing design, we kit was produced about 30 years ago minimum chances for failure; more parts do so with a bit of caution and a mea- and is, by today’s standards, somewhat equal greater chance for failure. The fuel sure of respect for that design we are primitive. It is better than building from system must be able to store, and then changing. We should acknowledge that plans, as the bulkheads and ribs are deliver, fuel from the tank to the engine reliably and in sufficient quantity, in all expected flight attitudes, or it is not only useless, but potentially dangerous. All of this meant that I wanted to approach any change to the original design with great care and a skeptical eye.

The Original The “as-designed” fuel system included a tank vent with a small line that ran inside the tank from its open end at the high, The F-1 Rocket has proved that the coiled fuel tank vent design works well with a very outboard end of the tank to the root rib. similar fuel-system design. From there, it runs into the fuselage, up

is an aeronautical engineer, Commercial Pilot and avid homebuilder with 30 years of leader- ship experience in aerospace operations and flight testing. He is also an EAA tech counselor and flight advisor who flies an RV-8 he built along with an RV-3 that he and his wife, Louise, Paul Dye recently completed.

Photos: Paul Dye KITPLANES July 2012 65 continued the inside of the forward cockpit to the eliminates the cockpit penetration and of the vent line is inside the high point of longeron, and then back down (after installation, and the coils act to trap the the tank, and this is true for either design, making a U-turn) to the bottom of the fuel so that it doesn’t create a siphon. The there is no real way that it can pull more cockpit and out through the floor. This more coils, the less chance of the siphon than the tip-top amount of fuel out of the up-and-down routing provides a “trap” effect. Simple and elegant. tank anyway. Once a small amount of fuel to keep fuel from flowing out of the tank is removed, the fuel is no longer up to the should heat expansion create a siphon Deliberations level of the open end of the vent line, so effect that could empty the tank. Of So we can see the benefits: less plumbing no additional fuel can flow into it, which course, the purpose of the vent is to allow and easier installation. What’s the down- is the same for either case. The amount of air back into the tank as fuel is removed, side? Well, two things that can go wrong fuel in the vent line itself is the only fuel and for this purpose, all it needs is a hole with a vent are that it dumps fuel over- at risk, and this will be limited by a finite at the high point. But in unusual attitudes board when we don’t want it to, or it fails amount of fuel line. Therefore, I would or loadings, this could lead to spillage. to vent the tank, and the tank collapses expect that even though it might burp a All of the two-place RV aircraft share before or after the engine quits due to little more fuel out through the coil sys- this same basic plumbing scheme, and lack of fuel. Identifying these two failures tem, it is still not going to be excessive. it has proven to be reliable. Occasionally, is the first step of our analysis. Looking at if you fill the tanks to the brim with cold the second issue first, is there any chance The Voices of Experience fuel and then place them in the sun, fuel that the new design is more likely to pre- With these two “failure cases” answered, will expand enough to burp over the trap vent the tank from venting properly? As I then move on to the next phase of my and out the vent, just as it is supposed long as the line isn’t crimped, fuel and/or analysis: looking for previous experi- to, without a flowing siphon developing. air should be just as free to move through ence. Has anyone done this before, and But building this system means running in either design. There is probably no dif- what were the results? In this case, sev- additional fuel lines into the cockpit, ference in the likelihood of a blockage eral hundred Rockets are flying around then out the floor, adding a few con- due to debris, as the part that sticks out with exactly this system. Are they good nections between the wingroot rib and of the belly of the airplane will be essen- representations of the system that I plan the fuselage (a tight place to work), and tially identical in either case. There’s little to use in the RV-3? Yes. The tank designs more construction in general. It turns out fear of a lack of venting. are almost (if not completely) identical, that the builders of the Harmon and F-1 Is this mod more or less likely to create Rockets (aircraft based on the RV to vari- a siphon to burp the fuel out? Well, the ous degrees) eliminated the loop of vent high point in the system is not going to line in the cockpit by simply running the be as high with the coil design, so it can tank vent out of the root end, through be argued that this would be more likely a couple of coils of aluminum fuel line, to burp fuel. Is it more likely to create a and then out the bottom of the wing/ continuous flow of fuel that would empty fuselage fairing. It is fairly simple to build, the tank? Well, because the outboard end

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TANK HIGH SEE TOP VIEW POINT WING TANK VENTING The “coiled vent” design used by the The RV-3 plans show a vent system that ties the two tanks together and includes a tall author is simple and keeps the entire vent “trap” against the firewall to prevent fuel from escaping. Of course, a single vent can be in the wingroot. It has been used on the plugged and prevent venting of both tanks—all later-model RVs have a separate vent Rocket designs quite successfully and is for each tank. easy to fabricate and install.

66 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes as the Harmon Rocket is built out of RV-4 easy to change back to the original design designer of a particular kit or airplane parts. It is important to make sure that if should I find a problem. I’d just install the designs something that won’t work (if it you are using other aircraft as examples to in-cockpit vent lines per the drawings (the doesn’t work, what does that say about validate your designs, you make sure they removable boot cowl skin on this design is your choice of kit?). By the same token, accurately represent what it is you are what would make this doable). it is rare when a design is perfect and going to try. In this case, we have lots of Making modifications to existing kit can’t stand a little improvement at some flying examples that match the proposed designs is certainly not extraordinary, point. Just be careful and cautious, use a change. Both in principle and in practice, and it is one reason many of us like to little engineering process, and let the evi- it works. (Flight experience, by the way, is build. But careful consideration of both dence lead you to a good decision. And best measured in thousands of hours. It the potential gains and the potential don’t be afraid to ask for help. There are can take that long for problems to show risks must be made before going beyond plenty of builders out there who will be up at the edges of flight envelopes. Hav- what the plans show. It is rare when the happy to offer. J ing one or two flying examples still puts things in the “initial flight test” phase.) The last step, and it’s an important one if we don’t want to do unnecessary experimentation, is to ask others about their experience with the idea. I asked Rocket builders how well the fuel vent worked, and their response was, “It works just fine.” Several of the Rocket EFIS builders/fliers I asked also had experi- Engine Monitor AOA ence with RVs, and I asked them if they Moving Map had noticed a difference between the Autopilot Approach Plates two vent designs. The answer was that the Rocket will burp a little more fuel, but it is a teeny amount, and it stops right away. It was just as I had suspected. There was no real problem there. Now there’s one final step, asking yourself, “If this idea is so great, why didn’t the original designer do it that way?” Often- www.Advanced-Flight-Systems.com times, this is simply a case of “If it ain’t Phone:(503) 263-0037 Patents 6,271,769 B1 & 6,940,425 broke, don’t fix it.” In truth, there is nothing wrong with the existing design for the RV-3. It works fine, and hundreds of people have built it. But there is also no reason not to implement a better idea, if you can be certain (or reasonably certain) that it is a better idea. The process I have described is one way to ascertain that it is, at least, not a worse idea. As part of my final, final analysis, I like to bounce my idea off of a few other builders, especially if they are engineers who understand trade studies and failure analysis. But even non-engineers might be able to point out flaws in the thought process. In the case of RVs, I have a number of experienced builders and engineers that I fly my ideas past as a reality check. This time, when presented with my thought process, none could see a safety issue. And one of the nice things about this modification is that it is reasonably

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KITPLANES July 2012 73 Part 103, LSA and flight-test areas. By Mel AsbeRry

Question: I've recently acquired an requirements, as it is no longer the Another possibility is the Experimen- Aerolights Falcon, a Part 103 canard machine as marketed? tal Exhibition category, but that in itself plane. It's been heavily damaged Answer: First it needs to be under- is a can of worms, and if you’ve read any from an aborted takeoff/turn. I stood that the conversion from ultra- of my columns, you’ll know that I’m not know the provision from Part 103 to light to Light Sport Aircraft is a little a fan of that option. If the completed Light Sport conversion has sunset- misleading. In reading the rules you aircraft meets all of the LSA rules, i.e., ted some time ago. And this model will find that a true Part 103 ultralight maximum gross weight, max cruise requires some structural modifi- was not eligible for conversion to Light speed, minimum clean stall speed, etc., cations in the interest of safety, Sport. The conversion was for “ultra- then it may be flown by a Sport Pilot, which will likely bring it over the light types” that did not meet Part 103. but it still would be classified as E/AB. weight threshold Part 103 encom- And, yes, that ship has sailed. Question: Your June 2011 col- passes, if only by a small margin. There are now two ways to license umn points out that a flight-test Among them is a heavier rear spar an Experimental Light Sport Aircraft: area will be designated by the DAR in the main wings and a bulkhead 21.191(i)(2), an aircraft constructed from that will keep the aircraft away to support the engine. You have a Light Sport kit, and 21.191(i)(3), where from congested airways or densely mentioned that destroying a part an aircraft that has previously been populated areas. How do I deter- and rebuilding from raw materials issued an airworthiness certificate in mine if I will be able to operate out applies to the major portion rule. the Light Sport category may be down- of the airport where my hangar is? Indeed, the destruction has been graded to the Experimental category. Can I move the aircraft there for taken care of. The major portion Obviously your aircraft doesn’t fit final assembly, or should I look for part is a foregone conclusion. either of these scenarios. Your only another location? While I would be perfectly happy option is to try for the Experimental/ Answer: This comes up around larger to fly this as a 103 machine, the Amateur-Built classification. To do this, cities where airports have become sur- safety modifications forgo any you must show that the major portion rounded by heavily populated areas. such notion. The obvious ques- (51%) of the aircraft was built for educa- You need to contact your DAR and/or tion is, are there any provisions in tion and recreation. You would need to the local FSDO. If flight testing is not the Light Sport Aircraft category use the form contained in AC 20-27G allowed at your airport, you will need that will allow a former 103, or Appendix 8. You really need to read and to relocate the aircraft before the air- does the major-portion rule, along comprehend the entire advisory circu- worthiness inspection. Otherwise, the with the required modifications, lar for a complete understanding of the inspector will be forced to deny the cer- arbitrarily qualify it for Light Sport amateur-built classification. tificate until the aircraft is relocated.J

74 KITPLANES July 2012 Photo: Mel Asberry A look at ducted fans. A ducted-fan propulsion system con- willing to accept a performance disad- at low speed. As the propeller draws air sists of a propeller or fan operating inside vantage simply because it looks like a jet. in from the front, there is a large inflow an enclosed duct system. Air is drawn in angle; air approaching the propeller at one end of the duct, accelerated by the Shrouded Propellers flows inward as well as aft. If the pro- fan, and exhausted out the other end of Unlike the buried “fake jet” system, the peller is operating inside a shroud, the the duct, producing thrust. short-duct shrouded propeller does incoming air is turned aft by the lead- Ducted-fan installations come in two have some aerodynamic advantages ing edge of the duct. This flow takes the forms. The first, known as a shrouded over a simple free-tip propeller. The inward component of the momentum of propeller, features a propeller (or fan) ideal efficiency of a propeller increases the air and turns it into additional rear- surrounded by a relatively short-chord, as diameter increases and disk power ward momentum. As the flow turns, it cylindrical duct. (The chord of the duct is loading decreases. This effect is more generates low pressure on the leading usually less than one propeller diameter.) pronounced at low airspeeds. In order to edge of the duct, causing a net forward Shrouded propellers have been tried in a achieve high thrust per unit horsepower force on the duct. variety of applications, and in a few cases while static or at low airspeed, a large- have made it into production. diameter propeller is required. While Effect of Airspeed on Ducted- In the second form of ducted-fan the same type of variation of thrust with Fan Performance installation, the fan is buried within the diameter holds for shrouded propellers, The large thrust advantage of a shrouded fuselage, with a flow path that looks like the shroud reduces the diameter needed propeller over a simple propeller at that of a jet fighter. There are relatively to get the same thrust. low airspeeds diminishes rapidly as air- long inlet ducts leading to the fan and a speed increases. While the ideal thrust similarly long exhaust duct. The only real Static Thrust predicted by momentum theory shows purpose of this type of installation is to According to ideal momentum theory, some improvement due to the duct, it simulate a turbojet. It is common in the the combination of shroud and rotor of becomes quite small as speed increases. world of radio-controlled models, and a ducted propeller generates a few homebuilders have built proto- more thrust per unit power than types of “fake jet” airplanes with buried a simple propeller of the same ducted-fan propulsion. diameter. The effect is most Attempts to use such a propulsion pronounced at zero airspeed, system on full-size airplanes have not where the ideal ducted system met with much success. A few machines produces 28% more static thrust have flown, but their performance is sig- than the simple propeller. For nificantly inferior to an airplane with the real-world systems, the static same power using an ordinary propeller. thrust increment can be even The combination of friction losses in the greater because the influence of long ducts and the high disk loading of the duct on the airflow helps the the fan hurt the inherent propulsive effi- individual propeller blades oper- ciency of the system to the point where it ate more efficiently. A ducted-fan powered parachute. A ducted fan is cannot compete with a simple propeller. The duct in a ducted system appropriate here because of the requirement for While the idea of a jet-like airplane generates a significant amount of high thrust at low airspeed, along with the need seems appealing at first, few pilots are thrust when operating statically or to keep parachute risers out of the prop. is a principal aerodynamics engineer for Northrop Grumman’s Advanced Design organization. A Private Pilot with single engine and glider ratings, Barnaby has been involved in the design of unconventional airplanes including canards, joined wings, flying wings and some too strange Barnaby Wainfan to fall into any known category.

Photo: Barnaby Wainfan KITPLANES July 2012 75 continued

In real flow, the skin-friction drag of the as good as the best point-designed duct duct opposes the thrust produced by at either low or high speed. The designer the duct. As airspeed increases, the drag must either sacrifice some of the static of the duct goes up and the ideal duct thrust advantage of the ducted system thrust goes down. At some point, the or accept some reduction in cruise per- two are equal. At airspeeds above this formance (or a little of each). point, the ducted system produces less One solution is to incorporate some net thrust than the simple propeller. form of variable geometry into the duct. The airspeed for this crossover An example is a ring leading-edge slat, depends on the details of the duct and which acts much like the leading-edge the power loading (or disk loading) of the slats on short takeoff and landing (STOL) system. Typical light airplane propeller airplanes. At low speeds the ring slat moves disk loadings range from about 4 pounds forward, giving the duct a slotted leading per square foot to 8 pounds per square edge and keeping the flow attached. At foot at full power. At such disk loadings, higher speeds the slat is retracted, giving the ducted-propeller system produces the duct a good high-speed shape. more thrust than a simple propeller only up to an airspeed of about 120 to 130 Tip Clearance knots. This assumes that the ducted sys- To make a ducted-fan system work well, tem has the same diameter rotor as the the gap between the tips of the fan simple propeller. blades and the inner skin of the duct If the diameter of the ducted system is must be as small as possible. If the gap less than that of the propeller it replaces, gets too large, much of the increase in the static thrust advantage decreases. thrust provided by the shroud is lost. None of this analysis takes into This makes it necessary to keep the account the weight of the duct or its mountings between the propeller shaft supporting structure. bearings and the duct extremely rigid. If the fan is attached directly to the crank- Duct Design shaft, the duct must be rigidly mounted The design of a good, efficient shrouded- to the engine. If shock mounting for propeller system is complicated by vibration isolation is needed, the entire several factors. At a low-airspeed, high- duct and engine assembly must be hung power condition, there is a large inflow together on the soft mounting system. angle in the oncoming air. To keep the airflow around the duct leading edge Noise attached, it must be cambered to turn As the population increases, the noise the flow aft, leading to a “bell mouth” generated by airplanes becomes more inlet shape. At higher speeds, the inflow and more of a community-relations and angle reduces dramatically. The airflow regulatory problem. Reduced airplane over the outer side of a bell-mouth inlet noise during surveillance and some will separate, causing a large amount of types of police work is also desirable in drag. A good cruise-speed inlet shape making the aircraft less noticeable to looks more like a fan jet engine nacelle those being observed. leading edge and has little camber. A significant portion of propeller noise Unfortunately, a cruise-optimized duct is generated by the blade tips and radiated inlet will have flow separation on the in the plane of the propeller. Theoretically, inner side at static and low-speed condi- shielding the tips with a duct can reduce tions, causing a large loss of thrust. or contain much of this noise. At least two The design of the inlet lip of the duct attempts have been made to put this into must be a compromise between low- practice on piston-engine airplanes. speed and higher-speed conditions. But In 1977, British company Dowty- this “best compromise” duct will not be Rotol flew an Islander with a pair of

76 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes ducted propulsors driven by piston airplanes used ducted propellers. VTOL engines in nacelles slung under the is a good application for ducted fans wings replacing the conventional pro- because static thrust per unit power is pellers and nacelles. It was claimed vitally important for vertical takeoff and that the ducted system had 20% better hover. The best of these was the Bell performance at takeoff and about the X-22. The X-22 had four ducted props at same performance at cruise. Although the tips of its canard and main wing. The the airplane was extensively demon- ducted system worked well for two rea- strated, the project never went beyond sons. First, the static thrust advantage the initial demonstrator. of ducted propellers made it possible to The Edgley Optica was a British obser- achieve good hover performance while vation airplane, designed by John Edg- keeping the diameter of the props down ley, intended to replace helicopters for to where they could be oriented aft some police work. It was a twin-boom for conventional takeoffs and landings machine with a bulbous, helicopter-like without hitting the ground. Second, the glazed nose and a single engine driv- ducts formed part of the wing in hori- ing a ducted fan at the back of the crew zontal flight and generated a significant pod. The Optica was not a sparkling per- proportion of the total lift. The four- former, but it was not intended to be fast. duct X-22 configuration was considered It did achieve certification and has been for the missions that were eventually produced in small numbers by three dif- filled by the tilt-rotor V-22 Osprey. The ferent companies: Edgley Aircraft, Brook- tilt-rotor was chosen primarily because lands Aerospace and FLS Aerospace. The the downwash environment under the Optica certainly sounds different than large-diameter rotors was more benign a propeller-driven airplane. It produces than the higher-velocity downwash a higher-frequency noise and lacks the generated by the fan system. sharp tones of a propeller at high rpm. Airships: Ducted fans have been used At takeoff, it sounds like an enraged vac- successfully on several recent airships. uum cleaner on steroids. Airship designers certainly do not have to concern themselves with anything Ducted-Fan Applications high speed. The ducted system protects Fixed wing: Shrouded propellers have the ground crew from the blades, and been tried on a variety of fixed-wing the ability to use smaller-diameter pro- airplanes with indifferent results. In addi- pellers makes the installation easier. Tilt- tion to the Optica and the Dowty-Rotol ing the ducts to vector thrust is used to experiments, there was another interest- aid takeoff and landing. ing prototype, the Fanliner built by RFB Hovercraft and ground-effect craft: in Germany. The Fanliner used the wings Shrouded propellers are the propulsion and tail of Grumman Cheetah, mated to system of choice for hovercraft and small a sleek fuselage incorporating a forward WIG (wing in ground effect) vehicles. pod housing two crew members, and a These craft operate at relatively low air- ducted propeller at its aft end. The tail speeds. Because the propulsion system was carried on a cruciform boom extend- must be mounted above the hull of the ing aft from the duct. The Fanliner was vehicle, keeping the diameter down is initially powered by a Wankel engine, highly desirable. Also, particularly for hov- which delivered 150 horsepower. It is ercraft, crew and ground personnel are interesting to compare the Fanliner and often close to the fans while operating or the Cheetah. Both airplanes had about loading and unloading the machine. All the same power and shared the same of these factors combine to make ducted flying surfaces. The performance of the propellers attractive, because the ducted two was similar, except for one thing: The system has advantages in most of these Cheetah carried four people, while the areas. An additional advantage is that Fanliner could carry only two. the thrust produced by ducted props can VTOL: Several relatively successful be vectored by vanes in the duct exit to vertical takeoff and landing research steer the aircraft. J

KITPLANES July 2012 77 The LED strip club, part 2. As promised last month, this time tle paint canvas at the back of your eye) What I’ll give you is a circuit that allows we’ll look at a way of creating different sees objects much like a pinhole cam- you to adjust each of the three colors of colors from your LED strip of three-color era does—everything painted on that the LED strip to any value you want, from lights. To briefly recap, you can make retina is upside-down. Your brain goes full dark to full bright. The parts are avail- any color of the rainbow, plus black and through an algorithm to turn it right-side able at any good electronics store, and it white, by using a suitable brightness of up again. If it didn’t, we’d see ourselves will be 100% efficient—for less than $10 the light strip’s three primary colors: red, walking on the ceiling. worth of parts. blue and green. Turn them all off and you end up with black; turn them all on, with Color Combinations Frequency Control the correct amount of light from each In 1931, the International Commission We need just a little more discussion of color, and you get white. on Illumination created the chromatic- the human eye to determine what fre- ity diagram called CIE 1931. It also came quency to use for the dimmer. If the eye Eye Exam up with the formula to create white: receives more than 24 individual “pic- The human eye is a nearly perfect inte- 60% green, 30% red and 10% blue tures” per second, it integrates them into grator. In this context, an integrator light. Changing these percentages will something that appears to be in motion. merely averages a light source over time. change your eye’s perception of color Keep in mind that the refresh rate of your It does not matter if a light is bright for in accordance with the CIE-1931 chart computer monitor is north of 60 frames a while and then off for a while, the eye (http://en.wikipedia.org/wiki/CIE_ 1931_ per second; your television’s refresh rate will simply see that as a continuous light color_space). For example, if you turn is 30 frames per second with what is averaged over time. For example, when off the blue and go with a 60/40 mix of called interlacing, with which you actu- a camera’s flash goes off near your face, green and red, respectively, you get yel- ally get 60 different frames per second you still see that flashbulb when you low tinged with orange. If you turn off but only half of the picture each time. close your eyes. This is your eye trying to the green entirely and go with a 70/30 While it may look like Kermit the Frog average out that brilliant flash over time. mix of red and blue, you get magenta. is in continuous motion, the camera is Your brain plays a major role in vision. And so on through the entire range of actually catching 60 individual shots of In another example, your retina (that lit- colors that the human eye can see. him per second.

Turning the red and green lamps on makes The blue and green lamps together create The red and blue lamps together give a a pretty orange color. a nice aquamarine. magenta glow.

began acquiring Aero’Lectrics expertise in 1959, fixing Narco Superhomers in exchange for flight hours. A Commercial Pilot, CFI and A&P/IA, he has owned and restored four single-engine Cessnas. He is chief avioniker at RST Engineering and teaches electronics at Sierra College. He’ll Jim Weir answer questions at www.pilotsofamerica.com. Check out www.rst-engr.com/kitplanes for previous articles and supplements. Gail Allinson is technical advisor.

78 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes So let’s run our dimmer with a frame rate of around 120 hertz (Hz), which is 120 pulses per second. If the radios cause any interference with the dimmer, you’ll want the dimmer well separated from the VOR (30 Hz) and localizer (90 and 150 Hz), and far below anything that would get into the VHF COM, NAV or GPS range. If you hear the dimmer as a low-pitched hum, you have a particularly poor ground loop in your electrical system. We start off with my favorite op-amp, the popcorn-cheap LM324 (four individ- If the waveform at the output of U101C Adjusting R101 to the other end of its ual op-amps in a single 14-pin package). looks like this, the red lamp will appear range makes the red lamp bright; it will Here is how it works: very dim. allow you to set the brightness anywhere between the two. A U101D is a relaxation oscillator with the output (the pointy end of the ampli- fier) being a square wave that is very near dollar, and you won’t see any difference try using them both on a single color; the power supply half of the time and between the two. The Q102 IRF device pick one or the other. Also, in an attempt very near ground, or zero volts, the other (part number IRFZ34N) is about a dollar to keep the drawing size to a mini- half of the time. However, at the left end at Jameco Electronics (www.jameco.com), mum, I did not repeat the lamp-driver of R111, the charge-discharge cycle of and the Q101 TIP device (part number transistor(s) for the green and blue LEDs. C101 makes a nice sawtooth waveform TIP120) is 40 cents. They are really overkill, Just make all three-color lamp-driver cir- going between one-third and two-thirds as the IRF field-effect transistor is rated for cuits identical. of the power supply voltage 120 times drain currents of 20+ amperes, and the TIP There are literally hundreds of sources per second—nice and linear, from about bipolar Darlington transistor can handle 5 for datasheets with pin identification 4 to 8 volts, back and forth. amps without much trouble. We are down (pinout) for the op-amp and the tran- Now let’s look at the lamp driver for in the half-ampere range with a full string sistors. Even if you buy your parts else- the red LED, U101C. Depending on the of lamps, and driving the transistors either where, you can still use Jameco as a setting of R101, the output of U101C full on or full off, so they will be dissipating source of datasheets for the op-amp and can be varied from a needle-wide pulse only a few milliwatts of power. But they both varieties of driver transistor. width (very dim) to full on all the time are both stable as rocks and among the That’s about it for the LED strip lights. (very bright). By adjusting R101 from one cheapest parts on the market. Next month I’ll try the “turn the hangar end of its range to the other, the red LED However, you only need one of these heater on with your cell phone” trick can be full dim or full bright or any value transistors per color. I have shown them that one of you asked me to design. in between. both to illustrate the circuit. Please don’t Stay tuned. J Now we need to concern ourselves with the actual lamp-driver transistors. I have shown two ways of doing things, both of which will cost you less than a

Both the IRF (left) and the TIP will do a The schematic. good job of lighting up the LED strip.

Photos: Jim Weir KITPLANES July 2012 79 By Robrucha

80 KITPLANES July 2012 www.kitplanes.com & www.facebook.com/kitplanes