Grass Runways: The Whisper of Wheels on Turf KITPLANES OCTOBER 2016 ® Merlin PSA • Grass Runways Merlin PSA • Maintenance Manuals • Weight

Savings The • Geared

Drives Personal • Pre-Buys Single Part 2 • Trick Stick • Dynamic Balancing • Torque

Plates Engine Theory OCTOBER 2016 BELVOIR Direct or Geared? In the Shop:

PUBLICATIONS One Trick Stick • Weir’s Workbenches Versatile Air Data Probe • Torque Plates • Vise Squad Weight Savings • Easy Rivet Holders

Do’s and Don’ts www.kitplanes.com SE

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The 7” SV-D600 display is priced at $1850, with the 10” SV-D900 at $3100. A complete 7” SkyView SE system with primary flight instruments starts at $3305 including harnesses. Add the SV-XPNDR-261 Mode S Transponder (with ADS-B Out) and SV-GPS-2020 GPS Receiver/Antenna for a low-cost integrated glass panel system that meets FAA 2020 ADS-B Out requirements. DynonAvionics.com [email protected] (425) 402-0433 October 2016 | Volume 33, Number 10 Flight Review 6 Merlin PSA: The personal single. By Paul Dye. Builder Spotlight 16 The Ins and Outs of Pre-buys: Don’t buy a used Experimental aircraft without one (Part 2). By Vic Syracuse. 24 Ge tting High OFF Grass: Flying organically with turf runways. By LeRoy Cook. 28 Custom Maintenance Manuals: They may not be required, but they’re essential for performing thorough inspections. 24 By Katie Bosman Krotje. 34 bAlancing Act: Troubleshooting vibration problems in homebuilt airplanes. By Matthew Dock. 40 One Trick Stick: Andrew Angellotti develops an air data probe for the masses. By Tom Wilson. 52 engine Theory: Direct vs. geared drive—one of aviation’s great debates. By Tom Wilson. 66 C ompletions: Builders share their successes. 72 A sk the DAR: Condition inspections, N-number problems, removing an electrical system and transponder. By Mel Asberry. Shop Talk 58 The New Guy: Documenting your build. By David Boeshaar. 60 Maintenance Matters: Torque plates. By Dave Prizio. 64 Home Shop Machinist: The vise squad. By Bob Hadley. 76 Aero ’Lectrics: Workbench. By Jim Weir. Shop Tips 51 A better rivet holder: By Eric Stewart. 63 Folding portable GPS mount: By Jim Fleischman. Designer’s Notebook 44 Stressing Structure: Places to save weight and places not to. By David Paule. 6 73 Wind Tunnel: Wing root junctions. By Barnaby Wainfan. Exploring 2 Editor’s Log: Early or late? By Paul Dye. 48 Checkpoints: The big picture and red herrings. By Vic Syracuse. Kit Bits 4 Letters 67 list of Advertisers 68 builders’ Marketplace 80 kit StufF: Drawing on experience. By cartoonist Robrucha. 40 On the cover: Chip Erwin puts the single-seat Merlin Personal Sport Aircraft through its paces. Photographed near South Lakeland, Florida, by Richard VanderMeulen. For subscription information, contact KITPLANES® at 800/622-1065 or visit www.kitplanes.com/cs. KITPLANES October 2016 1 Editor’s log Early or late? Long before I wrote for aviation publications, I was doing testing—of airframes, engines, avionics, and acces- sories. Flight test was my field, and I have always been given opportunities to evaluate and give feedback on vari- ous designs and products. It is reward- ing to see changes that you suggest implemented in a design, and you always hope that they are improve- ments and accepted by the pilots that will come after you. I have never really been an “edge-of-the-envelope” kind of guy however—more like someone who looks to minimize risk and look for incre- mental improvements—and that affects the kinds of evaluations that I will accept. I have often described myself as an early adopter of things that are not When you spend a lot of time testing avionics, your panel rapidly takes on a polyglot look of different brand names and labels. What’s important is that you maintain a minimum required to keep me in the air, and a instrument set needed to safely fly the airplane. (Photo: Paul Dye) late adopter of flight-critical equipment. Most avionics are a good example of and reliability is measured primarily by grasp when you’re young and looking the former. If an EFIS, GPS, or radio gives how many hours the particular design for excitement, but when you are old up the ghost in flight, it is pretty easy has accumulated. While I always try to and looking back on some of the excit- to bring the airplane back down in one have backup plans for every conceivable ing times you’ve had, you are sort of glad piece—assuming, of course, that the contingency when I fly, new essential that they are in your past—and thankful equipment doesn’t go up in a ball of fire, equipment causes me to have backups that you’re still alive to reminisce. and I wasn’t foolish enough to make it a to those backups—or sometimes to just But deciding to buy or try new equip- sole source of navigation in the clouds. pass the chance for potentially exciting ment isn’t just a matter of personal safety; Engines, powerplant accessories, and flight testing on to someone else. it can also have a large effect on your ignitions, on the other hand, are mighty The best test pilots I know are very pocketbook or bank account. Experimen- important pieces of gear, and while I am reserved people that go out of their way tal aviation is known for radical ideas and qualified in a number of gliders, I prefer to not to experience excitement, but to the people who think them up. There are do power-off work in airframes designed minimize it. Boring people actually. The countless designs that looked like the specifically for quiet flight. The same ones that have lived the longest usu- upcoming salvation of aviation itself—yet thing is true for any part of the power ally stop after one beer, and are often they quietly faded into the background train—from the fuel caps all the way to headed home early to study for the next when reality sank in, funding dried up, and the exhaust pipes. I want those reliable, day’s flight. I know that is a hard idea to problems cropped up with no solution.

Paul Dye retired as a Lead Flight Director for NASA’s Human Space Flight program, with 40 years of aerospace experience on everything from Cubs to the space shuttle. An avid homebuilder, he began flying and working on airplanes as a teen, and has experience with a wide range of construction techniques and materials. He flies an RV-8 that he built in 2005, and an RV-3 that he built with his pilot wife. Currently, they are building a Xenos Paul Dye motorglider. A commercially licensed pilot, Paul has logged over 4800 hours in many different types of aircraft and is an EAA tech counselor, flight advisor, and member of the Homebuilder’s Council. He consults and collaborates in aerospace operations and flight-testing projects across the country.

2 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes Unfortunately, the early adopters who souls? By applying some strict rules found a completely new law of physics, provided deposits, which the developer about where you will and will not finance, or of nature. In most cases, it’s used to pay for his hangar rent during spend your money, for starters. The highly unlikely. If someone presents you the design phase, never saw a product same rules apply as they do in non- with the product of your dreams, pinch in return for their cash. The frequency aviation endeavors. Learn the laws of yourself—you might just wake up to find with which this happens has always physics and know that they can’t be that yes, indeed, your dream was about astounded me, for again and again, we broken. You are not going to go 250 to turn into a nightmare. see companies both big and small give knots on 65 horsepower unless you are Being an early adopter is OK, so long as up on their seemingly foolproof ideas, be doing it pointed straight down from a you go into it willing to have the product they for airframes, engines, or avionics. great height. Electronics and software fail and to lose what you have invested, Coming up with the idea for a new development cost money—and while in both time and money. If you have to product is easy. Coming up with a design Apple can sometimes give away cell do a great deal of modification to your that promises to deliver on that vision is phones, they can do this because they airframe to install a new design, under- harder. Testing the prototype and solv- have amortized the development cost stand that you might have to do a lot of ing the inevitable problems that crop over millions of units. In aviation, unit modification to back out of the product up can drain the resources of the best development runs are numbered in the if it fails. We don’t get anywhere without capitalized company. And finally, bring- thousands, or sometimes the hundreds. someone taking the risk, but make sure ing the prototype all the way into pro- If a developer is going to pay back the that you can tolerate failure before you duction and actually shipping finished costs of putting a new EFIS on the mar- take the plunge. Many of us are used to items to customers is a hurdle that many ket, they are going to have to charge taking financial risks, but failures in avia- never achieve. The end result of this dif- what it cost to pay their salaries for the tion can take more than your money— ficult chain of development often leads years of development. they can cost you your life. to bankruptcy, disillusionment, and When a company makes promises Keep your eyes open, and remember unhappy customers. that just don’t seem right, they probably the old saying: If it looks too good to be How can you keep from becoming aren’t. Use your intuition, look at history, true, it’s probably time to look some- one of those unhappy and unfulfilled and see how likely it is that someone has where else. J

KITPLANES October 2016 3 EDITORIAL Editor in Chief paul Dye [email protected] Survey Results We are always happy to see these sort of sto- Managing Editor mark Schrimmer Earlier this year, we asked our read- ries as well, Todd. As much as we like to Art Direction Dan Maher ers to tell us what they thought about think that aviation is just about airplanes, Editorial Director paul Bertorelli KITPLANES® and how we cover the it doesn’t take much digging to understand Contributing Editors larry Anglisano, Marc Ausman, Experimental/Amateur-Built aircraft roy Beisswenger, Chuck Berthe, that it is as much about the special people David Boeshaar, LeRoy Cook, world. We were immensely pleased with that make up the aviation community as robert Hadley, Dan Horton, the size of the response and want to well.—Ed. louise Hose, Amy Laboda, Dave martin, Sid Mayeux, David Paule, thank those of you who took the time to Dave Prizio, Dean Sigler, Dick complete the survey. We know it took 10 Where are the Ultralights? starks, Eric Stewart, Vic Syracuse, barnaby Wainfan, Jim Weir, minutes of your valuable time, but we are I have been a KITPLANES® reader for tom Wilson. confident that it will help us maintain many years and have always enjoyed Web Editor Omar Filipovic our focus on the types of articles that the content I find in each issue. I have Cartoonist Robrucha you want to see. Don’t expect a major noticed in recent years that there hasn’t ADVERTISING overhaul or significant changes to hap- been any coverage of ultralight aircraft Sr. Advertising Manager Chuck Preston pen all at once—but expect to see small like we used to see in the past. Is there a 805/382-3363 and incremental improvements based on reason for ignoring this part of the avia- [email protected] your input. tion community? BUSINESS OFFICE Paul Dye Rob Kindrell Belvoir Media Group, LLC Editor in Chief 535 Connecticut Avenue Norwalk, CT 06854-1713 You’re right—we haven’t been covering EDITORIAL OFFICE the ultralight community like we used to, 535 Connecticut Avenue but it’s not because we think they are less Norwalk, CT 06854-1713 important than other parts of the aviation [email protected] community. Many pilots today got their CIRCULATION start in very light flying machines, mov- Circulation Manager Laura McMann ing on when they wanted more capability SUBSCRIPTION DEPARTMENT or performance—or had a bigger check- 800/622-1065 ing balance. The reason we aren’t covering www.kitplanes.com/cs P.O. Box 8535, Big Sandy, TX 75755-8535 them is because of the growth in the num- For Canada: Box 7820 STN Main, London, ON N5Y5W1 ber of available kits for E/A-B aircraft and the desire to present detailed, in-depth cov- REPRINTS FOR PUBLICATION AND WEB POSTING AVAILABLE erage for our readers within the limitation Minimum Order: 500 of our magazine’s size. It’s simply a matter Contact Jennifer Jimolka, 203/857-3144 Culver Props of adjusting the focus to a narrower range of I thoroughly enjoyed reading the arti- machines, rather than providing too shal- cle about the Culver prop family [The low of coverage over a wider field. There Change of address? Dawn Patrol, June 2016]. It’s people like are other fine publications and web sites Missing issue? this that have made America one of the Subscription Question? that cover the ultralights very well, and best places to fly around and meet won- we consider those to be excellent sources of Visit www.kitplanes.com/cs. derful, hard-working people in the avia- information. Our editorial staff loves all Or call 800/622-1065 from the U.S. and Canada. tion industry. More please, and keep up sorts of flying machines, but we simply keep the good work! KITPLANES® focused on being “Your Foreign 903/636-1112 or fax Todd Reifers 203/857-3100. Homebuilt Aircraft Authority.”—Ed. J

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, 535 Connecticut Avenue, Norwalk, CT 06854-1713, 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 ©2016 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 Canada Post: Return undeliverables to P.O. Box 2601, 6915​ Dixie Rd, Mississauga, ON L4T 0A9 or call 800/622-1065. Kitplanes® is a registered trademark of Aviation Publishing Group, LLC.

4 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes An opportunity like this only comes along once an airplane. (Unless you add a second as your HSI).

G5 Electronic Flight Instrument. Primary fl ight display with optional autopilot capability for your experimental or LSA. Or integrated backup to complete your G3X® or G3X® Touch system. Learn more at Garmin.com/G5.

©2016 Garmin Ltd. or its subsidiaries

31670 G5 Experimental Ad-Kitplanes.indd 1 7/6/16 11:24 AM Merlin PSA The personal single. By PAUL DYE

A little more bank and more opposite an elevator on a string. When the time pattern time. This airplane wasFun — rudder brought the touchdown point seemed right, all I had to do was kick with a capital “F,” and I hadn’t even left perfectly into view down by my left hip. the rudder out, level the wings, and the pattern yet! With the throttle all the way closed, the “thump”—a nice positive, but soft, view out the left side was almost heli- touchdown occurred, right on the spot A New Import copter like, with a steep but controlled I’d been aiming for. Rollout was a mat- The Merlin PSA grew out of a project by descent aimed right at a particular ter of maybe a hundred or so feet, and a few young CAD engineers in Czecho- spot of grass on the rapidly approach- that was without braking. slovakia back in the 2009 time frame. ing runway. With little forward speed, I added power and rolled for another Conceived as a single-seat sport aircraft, the effect was sort of like coming down takeoff, my fifth or sixth in 20 minutes of it was spotted by aviation entrepreneur

6 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes Chip Erwin, who had spent 20 years liv- ing in that country and has sold several different designs around the world over the years. Noting the ease of construc- tion and fun flying characteristics, he has now brought it to the United States as the Merlin Personal Sport Aircraft, and will be offering it as a basic kit or as a kit with a build-center option for those who would like to get it done quicker by coming to his facility. Erwin’s company, Aeromarine LSA (www.aeromarine-lsa. com) is based in South Lakeland, Flor- ida, and the grass strip is perfect for fly- ing the single-seater for fun. Chip Erwin is the importer of the Merlin kit and is based in South Lakeland, Florida. He is The airplane is instantly comfort- currently setting up a builder-assist center at the field. able and feels familiar, even though you might never have flown anything like is working on a mount for an HKS four- making this a fun airplane that can go it. It has been described as a single-seat, stroke engine with similar horsepower, almost anywhere! miniature Cessna 150, but this only which should run a little smoother and gets across the idea that it is a high- satisfy those who just aren’t comfortable The Cockpit wing, all-metal monoplane with easy flying behind a two-stroke engine. His The cockpit of the Merlin is one of and straightforward handling charac- ultimate goal is to offer the airplane with the most comfortable and finished teristics. A lot has been learned about an electric powerplant, one that only single-seat cockpits I have been in. The making good STOL airplanes since the needs to be recharged overnight, rather semi-reclined seating position is just early days of the Cessna empire, and than have the tanks refilled. He is cur- right, offering a relaxed seating posi- the Merlin’s wing sports a fairly high rently testing electric powerplants on tion within easy reach of all controls, aspect ratio, with generous Fowler flaps an ultralight motorglider and, at some while giving maximum visibility out of to make it spritely enough to challenge point, will transfer that knowledge and the high-wing airplane. The four-point most production planes in short takeoff the mature equipment to the Merlin. rotary-buckle harness is lightweight, and landing performance. Erwin’s other big goal is to mount yet clever, allowing the various belts to The Merlin is currently powered by the airplane on amphibious floats be snapped in place easily before being the Rotax 582 two-stroke engine with (the prototype will already be splash- locked. You do have to maneuver around dual ignition and water cooling. Erwin ing down by the time you read this), the short center stick while entering, but

The semi-reclined seat is quite comfortable and the compact rotary buckle for the harness is typical European quality (left). The cockpit of the Merlin is well equipped for a simple, single-place airplane (right).

Photos: Richard VanderMeulen and Paul Dye KITPLANES October 2016 7 holding it full back as you pass your left leg over the top is not hard. The stick features a foam grip and a single PTT switch on the top—more than enough complexity for this little bird. The throttle quadrant on the left feels like it came out of something much larger than the Merlin. The hefty throt- tle knobs at the top of the lever extend on both sides, giving a jet-engine feel. The brake lever sits low and is pulled back to apply stopping power to both brakes evenly. A clever arrangement of hydrau- lic cylinders also allows differential braking when the lever is pulled back, The beefy throttle quadrant fits the hand well, and the brake lever (on the front) is easy and the rudder pedals are deflected— to grab once you have the throttle all the way back. Note the elevator trim switch and the 9-volt battery used to power the trim. individual braking (of a sort) without individual brake pedals! There is a choke notches for takeoff and four for landing. The Merlin is equipped with a whole- lever (which I didn’t use) located on the This gave a solid feel to both operations. aircraft Ballistic Recovery System, the inboard edge of the quadrant, good for The instrument panel is nicely canister residing in the baggage area and the first start of the day in cold weather. equipped for an LSA, with an MGL deploying through a frangible upper This will obviously change with various Extreme EFIS providing airspeed, alti- rear window. The forward suspension engine configurations. tude, and attitude information, along straps are covered on the outside (above The pitch trim switch is located right with engine data. Next to that is a com- the wing roots) with tear-away alumi- behind the throttle on the side of the pact 2¼-inch com radio and a Mode S num covers and are hardly noticeable. quadrant and drives the Ray Allen servo transponder. Continuing to the right, The deployment handle is up on the with a 9-volt battery placed right next to you’ll find a clever little remote control inboard side of the left wing root, just the switch. It couldn’t be much simpler. head that will raise and lower retractable forward of the flap handle, an easy and The flap lever is located about the pilot’s landing gear on the optional amphibi- convenient pull for the pilot. left shoulder and is pulled down to add ous floats (more about that in a sidebar). Cockpit entry is through a swing-up flaps. A slight tug inboard allows it to Below the gear control is the head for a door on the right side. The door latches move between positions, and pushing it new TruTrak ECO autopilot, the two- on the bottom and forward edge, and back outboard inserts a pin in the appro- axis autopilot that controls with tiny was easy to secure. I rarely find a proto- priate position’s index hole. The lever is servos and flies the controls surfaces type aircraft with a cockpit as well fin- pulled into the index holes on the pro- themselves via trim tabs. Finishing off ished as what I found in the Merlin. It’s totype with a piece of bungee cord. I the panel is space for a Garmin aera neat and tidy, with excellent labeling all expect that Erwin will find a more ele- GPS as a moving map, and finally, the around. Erwin has even equipped it with gant solution in the future. I used two fuel selector. not one, but two cup holders—mildly

8 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes prop through an integral gearbox. It fea- tures dual carburetors using a common airbox, and it’s a rotary-valve engine, as is normal for the two-stroke Rotaxes. Flying the Merlin Getting into the Merlin, the first thing that you notice is that everything just fits. The seat is comfortable, the stick and throttle fall naturally to hand, and the flap lever is in a great spot. You can strap yourself in tight and still reach every control—an easier design goal in a single-seat airplane than in a larger one, The flap lever is easy to reach and feels very natural. Erwin is working on a spring to but one that still isn’t always accom- replace the bungee cord used on the demonstrator. The red handle is for the BRS. plished. Buckling the four-point har- ness, there is little more to do than turn eccentric for a single-seat airplane, but a crisp solid feel. The fairly narrow on the master, avionics, and hit the start some might want hot coffee and cold wings sport generous Fowler flaps with button; the little Rotax fires right up. water on the same trip. a noticeable airfoil and are quite effec- Seeing as how it is a two-stroke engine tive. The tricycle landing gear is solid, in an all-metal airplane, there is a little Conventional–Just Smaller with a U-shaped nosewheel spring rattling as it warms up, but it’s no worse The airframe is constructed entirely of absorbing any loads up front. While than the wet-dog shake you get when riveted aluminum (except for the com- there is currently some metric hardware shutting down a Lycoming. posite cowl) and is fastened together on the plane (things like fuel drain After the temperatures had warmed using pulled Avex rivets. The overall valves), Erwin is working to make the up, it was time to head to the runway, impression is one of ruggedness and aircraft to U.S. standard AN hardware and in this case, that meant a turf taxiway strength. No dimpling is required, for specs so that American pilots won’t find the rivets aren’t flush—nor do they need themselves stuck somewhere for want to be at the LSA speeds the aircraft is of a nut or bolt. Building Options capable of flying. The configuration is The current engine is the Rotax 582 Chip Erwin has been involved with a number quite conventional, just smaller than two-stroke that has been around for of interesting airplane designs in his career in what most pilots are used to. It is, for years. It features an oil injection tank aviation, but the Merlin is really special. With instance, unique to be able to check the and water-cooled radiator (plus cool- the option of having wheels or amphibious fuel cap on a high-wing airplane with- ant reservoir), dual carbs, and dual elec- floats, it is a versatile fun machine at a very out having to get on a ladder. tronic ignition (with two spark plugs per good price. For just shy of $40,000, you get All of the flight controls in the Mer- cylinder). It turns in the neighborhood the land plane version kit, with engine— lin are activated via pushrods, providing of 6000 rpm and drives a three-blade and that includes the builder-assist option. This is a factory-assisted build that can have you flying in a very short time. Erwin is very excited to offer this, as it will get Merlin PSAs in the air faster, and one can tell from the way he talks about it, he’d love for all customers to take advantage of it. But, what if the builder just wants a kit shipped to their house somewhere, so they can build it themselves? Well, builder assist is an option, so you can save money doing without it, of course. And if you use the money saved as part of the payment for the amphibious floats, you can have an amazing little airplane for a very attractive price—so The structure of the Merlin is simple long as you are happy flying alone. Remem- and reminds one of a ber, this is still a single-seat airplane. miniature Cessna 150. —P.D.

KITPLANES October 2016 9 through growing grass. While the small wheels and stiff gear make that a little bumpy, it was surprisingly controllable, and the nosewheel steering was positive. Braking is accomplished by pulling back on the handle at the forward end of the throttle quadrant, and I really didn’t feel the need for differential braking, although that is automatic with brake application during rudder deflection, so it’s hard to tell what it contributed. Vis- ibility was good—the seating position is such that your head isn’t so high in the cockpit that it is blanked by the wing. I was actually surprised by the amount of headroom, a consequence of the laid- back seating position. The prototype is flying with a two-stroke Rotax 582 with dual carbs and water cooling. Run-up before takeoff was simple—a CIGAR check will do—and lining up Flap retraction produced a little pitch The last time I spent much time with on the runway, I pulled on the recom- bobble, but after I experienced it once, a two-stroke Rotax was on a jet ski, mended 20° of takeoff flaps, and then it was easy to anticipate the next time. and it took a few minutes to get used poured the coal to the little Rotax. Unfortunately, the electric trim failed. to the wide rpm range and the sound There is a surprisingly large throttle I thought it was just very, very slow, but of the engine at 6000 rpm. I pulled the throw, and a wide rpm range, so with fortunately, the airplane is light enough power back a little after reaching a spot my normal steady application of throt- that it was easy to fly without adjust- outside of the traffic pattern, and the tle, it took a little longer to get to wide ment. It was not uncommon in the early airplane seemed comfortable at around open, and I was flying about the time days of aviation (and even general avia- 5500 or so. that it got there. The airplane acceler- tion) for small aircraft to have no trim The airplane behaves as you’d expect ates smartly and climbs amazingly well capability, so this was not a show-stop- a very light airframe to do in slightly for the small number of horses under per. In fact, I flew the entire speed range bumpy air. It moves around a little bit, the cowl. There is no doubt the airplane of the airplane without the trim and still but is very well behaved and not ill man- likes to fly! I observed about 1000 fpm wasn’t sure until after I landed that it nered at all. The controls are responsive in the climb with flaps retracted—quite was an anomaly. A little pressure was all and well harmonized, with equal force respectable for an LSA. it took to hold whatever speed I wanted. getting equal rates in roll and pitch. The Merlin on Floats Chip Erwin, the man behind the Merlin, is a floatplane pilot at heart, and has always seen this little airplane sitting proudly on the water, ready to have fun. It certainly has enough performance to do so, and Erwin just happens to have suppliers in Europe who can send all the metal floats he needs—and they’re amphibious! The self-contained hydraulic system to retract the gear was designed in Florida and is operated by either ship’s power or a separate battery. The clever part is that it operates wirelessly from a remote control (not unlike that for a garage door opener) attached to the instrument panel, so the only thing that has to pass from the aircraft to the floats is a brake line. The lightweight, but rugged, floats will be a $10,000 (approxi- mately) add-on, and can be bought completely ready to attach to the Amphibious floats for the Merlin feature retractable gear, oper- airframe and fly. It makes the most sense for a builder to license the ated by a self-contained hydraulic system with wireless controls. airplane on wheels, then add the floats later. This way, they are not subject to the 51% rule—a nice little loophole in the regulations that configuration, a task we are going to have to draw straws for among eliminates all that riveting and sealing. the writers. Almost everyone has their bathing suit ready and is The airplane had not yet flown on floats at the time of this anticipating a chance to fly to a remote beach for a little R&R. report, so we’ll update you when we have a chance to fly it in that —P.D.

10 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes

Merlin PSA

Kit Price (quickbuild kit) ...... $14,500 Estimated completed price with builder-assist program ...... $34,900 Estimated completed price without builder-assist program ...... $27,400 Estimated build time ...... 150 hours Number flying (at press time) ...... >10 Powerplant ...... Rotax 582, 65 hp @ 6500 rpm Propeller ...... Various options including DUC Swirl ...... 3-blade ground-adjustable Powerplant options . . . . .HKS 700E, 60 hp @ 6200 rpm

AIRFRAME Wingspan ...... 25 ft 7 in Wing loading ...... 9.4 lb/sq ft Erwin is definitely not hooked on a single powerplant choice. The planned options are Fuel capacity ...... 13 gal boldly listed on the current cowl, but not all of them have flown. Maximum gross weight ...... 715 lb Typical empty weight ...... 415 lb rudder is light and sensitive, and once try the other end of the scale, and that is Typical useful load ...... 300 lb you remember that it is normal to hold where the amazement really set in. Full-fuel payload ...... 222 lb left rudder when climbing (due to the Pulling the power back, I started with Seating capacity ...... 1 counter-clockwise prop rotation), you flaps up and slowed until I felt the first Cabin width ...... 27.5 in can settle the ball down a bit. The prop nibbles of a stall. The airplane was eas- Baggage capacity ...... 25 lb rpm varies considerably with minor pitch ily controllable in all axes at this point, adjustments, making for a little constant and the ASI showed just 38 mph! No PERFORMANCE footwork in maneuvering flight, but just matter how much I pulled, I couldn’t Cruise speed ...... 100 kt let your butt tell you what it needs. get a true stall break; the airplane sim- Maximum rate of climb ...... 1400 fpm As I leveled off about 2000 MSL ply began to sink—but not very fast— Stall speed (landing configuration) ...... 33 kt (and AGL—this was Florida after all), as with a canard in the same situation. Stall speed (clean) ...... 41 kt I left the power in and let the little yel- Next, I reached up and pulled in some Takeoff distance (to 50 ft agl) ...... 350 ft low screamer accelerate. It topped out at flaps, and the bobbles stopped immedi- Landing distance (from 50 ft agl) ...... 500 ft about 110 mph indicated, with the tem- ately. More flaps, more pull, and before Specifications are manufacturer’s estimates and are based on the perature about 15° above standard. After I knew it, the ASI was down in the 20s configuration of the demonstrator aircraft. maxing out the airspeed, it was time to and the plane was only beginning to

The side windows extend down to the pilot’s thighs, providing great visibility down and forward in a slip to landing.

KITPLANES October 2016 11 The Fowler flaps have a significant airfoil shape, helping to account for the low stall speed. The straps for the BRS are hidden by sim- The prototype is equipped with the new TruTrak ECO autopilot, the tab of which can be ple aluminum covers attached with soft seen here on the aileron. rivets that will rip away on deployment. complain with a little bit of nose bob- slowly dropped in an overshoot, then pulled into a nice lazy eight, followed by bing. At 28 mph and full flaps, I once recovered to approximately the same a chandelle. The constantly varying rpm again was unable to get a stall break, so I nose-high attitude, then sunk again— with speed made for a very challeng- added power and flew out of the condi- and so forth. I let it go three full cycles, ing exercise in ball centering, but then tion, easing up flaps as I went. The nose- and it was not diverging, but it wasn’t again, most pilots could use this drill high attitude with the flaps out was so damping out either. I’d have to say that once in a while. For those of us that reg- extreme that no pilot who is still con- the airplane is definitely stable, but it is ularly get lazy behind a constant-speed scious could expect to miss the impend- not going to return to its trimmed speed prop, the Merlin is a good workout, and ing stall in the pattern. immediately in an upset. The good news well worth the time it takes to tame it. Accelerating once again to a nice rea- is that it is not going to go into a scream- While certainly not aerobatic, the Mer- sonable cruise speed (about 5000 rpm ing dive—unless that is what the pilot lin presents its own training program to on the tach), I trimmed the airplane wants to do. keep the pilot sharp. out, let it settle, then pulled back to add I couldn’t resist a few advanced Re-entering the traffic pattern, the about 15 degrees of pitch, then let go of maneuvers to check out the handling airplane already felt very natural, much the stick to watch the phugoid. The nose before returning to the airport, so I like an old pair of gym shoes you put

The nosegear uses a U-shaped composite A typical spec from the plans for the airplane. We did not see a complete build manual, spring to absorb landing loads. but the drawings are done in a CAD system that should allow a high-quality document.

12 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes “The airplane is instantly comfortable and feels familiar, even though you might never have flown anything like it.”

KITPLANES October 2016 13 on for a quick workout. There was no traffic at South Lakeland Airport that morning—probably because of the low ceilings and approaching thunder- storms—so I had the opportunity to tailor each approach however I wanted: close, far, high, or low at low key. It made little difference in the end. Using two notches of flaps until final, then pulling on full flaps when lined up, it was easy to hit the spot exactly where I wanted every time. There is something about landing air- planes that I just love, and I can go ’round The fuselage substructure shown at the Czechoslovakian factory where the kit is manufactured. and ’round the pattern for hours in an airplane like this. It goes where you want I flew several different approaches, designs into the U.S. market, unfortu- it, glide path control is easy, and slips are from steep to shallow, and they all ended nately, with varying success. As anyone absolutely natural. In fact, I preferred up in the same place—a nice nose-high who has tried to make a living in avia- slipping the airplane simply because the touchdown, on spot, and at speed where tion knows, the vagaries of the market, visibility out the side is so good. stopping in a short distance was no the timing of multiple economic factors, The touchdown is easy to judge, with issue. And this was with about 30 min- and a wide variety of other variables good visibility out either side window utes total time in the airplane. That’s makes success a crapshoot, regardless of to see where the ground is, relative to a good omen for anyone checking out the goodness of the design you are try- the wheels. There was enough energy in this little scooter. The airplane per- ing to sell. at a 6o-mph approach speed to give a formed well on takeoff with 20° of flaps With the Merlin, Erwin has found good flare with just a little tug on the or no flaps when on the go. It jumped off a remarkable little airplane that most stick, and touching down on the mains quicker with the flaps, of course, but it pilots will probably enjoy—and it with the nosewheel safely in the air was was plenty quick without them. promises to be a relatively fast build. The very natural. There was no tendency questions, as always, are if the timing is for the nosewheel to slam down of its New Kit, New Company right, the customers there, and the sup- own accord. I give the Merlin very high Erwin has been involved with airplane ply chain reliable enough to make the marks for its ability to operate from kits for decades, and has been responsi- endeavor successful. Having a great air- short fields. ble for bringing several different foreign plane is just a small part of it. Depending Bluetooth Floats? It seems that just about anything you want to buy these days comes with Wi-Fi this or Bluetooth that—and old-fashioned aviators have been able to safely hide in their hangars to avoid the onslaught of wireless technology. Well, open the doors, guys, because here’s one more reason that you might want to go wireless! The amphibious floats available for the Merlin feature retractable maingear and nosegear, operated by a force-sensing, self-contained hydraulic system with wireless controls. The pump package is borrowed from a clever shallow-water anchoring system designed for fishermen, which lowers a pole into the bottom and senses when to stop push- ing to keep the boat in one place. In this application, it doesn’t need up or down locks to keep the wheels up or down; it senses the back-force in the hydraulics when the mechanisms go over center and shuts the motor off automatically. The advantage to this system in the float application is that the connection to the cockpit is wireless—essentially a key-fob type control that mounts to the instrument panel. The battery to power the system can reside in the float, or a 12-volt line can be run to the airframe battery if you want to keep it charged from the alternator. The Merlin is designed to be easily converted from floats to wheels, but since the floats have retractable gear, we’d expect that once you put it on floats for the summer season, it would probably stay that way until the snow flies. The wing structure is standard for an —P.D. aluminum aircraft—no surprises here.

14 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes planes out the door, another consider- ation for potential buyers. Overall, I love the airplane, but advise potential customers to make sure that they are comfortable with the maturity of the design and the company before they invest. That’s a caution we give with all new aircraft kits we review—even those from established kit companies. An Airplane for Fun The Merlin is what we think a Light Sport Aircraft should be—easy to main- The basic structure of the fuselage includes a center section for the wing. tain and fun to fly. With good handling qualities, it challenges the pilot to per- on foreign suppliers and still hunting Erwin’s plans to provide a builder-assist fect their short landing technique, but for the right engine, Erwin’s Merlin center and market this as the primary in a friendly way that is low risk. The is going to have to survive the unpre- method for customers to acquire and rugged construction should make it tol- dictable forces that have ended similar construct the kit is bold, but he assures erant to the occasional mistake, and the commercial enterprises and, as always, us that someone who simply wants a full cockpit layout is first-rate. we recommend that potential owners/ kit shipped to their workshop will be wel- While it is too early in the produc- builders do their homework and evalu- comed as well. Plans and build instruc- tion cycle to tell if it will be a commer- ate if they are comfortable with the risks tions were not available for us to review, so cial success or not, the airplane itself is of going with a new product. there might still be some bumps for early easy to recommend. To those builders This warning is no different with adopters, but the fact that the airplane willing to invest early, you could have the Merlin than we’d give to any new was designed as a pre-punched, matched- a fun flying machine that will garner airplane project, and the Merlin has a hole, CAD/CAM design should make excitement wherever you go. We plan to number of advantages that might help development of the instructions and keep an eye on this design and see how it tip the scales toward success. The plans relatively easy. the engine choices mature. We would mature airframe design is probably the Erwin’s work on a set of optional not be surprised to see a steady chain of biggest, while the ongoing search for amphibious floats for the airplane can be them coming into the Light Sport fleet powerplants is always something to seen as a plus, but it also can take the small as the word gets out about just how fun watch carefully. company’s eye off the ball for getting land they are to fly.J

KITPLANES October 2016 15 The Ins and Outs of

Pre-buysDon’t buy a used Experimental aircraft without one (Part 2). By Vic Syracuse

16 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes I know you have all been waiting for the second part of my pre-buy article so you can run out and perform your own inspections. Based on the example of a customer who brought his RV-10 to me for a panel upgrade, I hope you will still seek out experience to help you. In this case, the customer had paid for a pre- buy and was told the wiring was fine. I removed solid copper Romex house wir- ing with screw splices in multiple places and ended up rewiring the entire air- craft! So, hopefully you’ve been patient with your purchase since last month and we can continue our education. Don’t forget to take the time to either remove the wheelpants or use a bright flashlight to Finishing the Airframe Inspection look for cracks in the brackets. Continuing where we left off, the for- ward tank attach fittings on the Van’s Speaking of fuel tanks, many builders Firewall Forward series are another area that requires forget to label the caps with the type and Once I am satisfied we have a sound air- some attention, as they must be built amount of fuel. frame, it is time to move onto the engine to provide both some measure of safety The last things to closely inspect on compartment. This is the area where the in the event of an accident as well as the airframe are the landing gear attach builder usually receives the least guidance security from movement during nor- points. In the case of a retractable-gear from the kit provider. Many do not even mal operations. This is accomplished airplane, a retraction test on jacks is a know where to look for service bulletin by a slot in the physical attachment, definite requirement. or airworthiness directive applicability along with the use of drilled-head bolts Van’s has issued a number of service to their engine. A fair number of them do tightened into a nut plate and then bulletins pertinent to the landing gear not understand that there is an oil screen safety-wired. Depending on the vintage on various models, and it is wise to pay on the engine, along with a fuel inlet of the aircraft, some have slots cut by attention, especially if the aircraft has screen on carburetors and fuel servos, that the builder into fabricated aluminum been routinely operated off of grass and need to be checked and cleaned regularly. attachments, and the newer ones have at high gross weights, both of which can I like to understand the history of metal pre-stamped parts with the slot induce cracking on the engine mount the engine before I even start looking at already cut. One aircraft made a strong weldments. A bright flashlight is our anything, and also inquire as to whether “pop” right at takeoff (yes, very unnerv- friend here. or not it has been on an oil analysis ing) until we discovered the forward On aircraft with bungee-cord shocks, program, especially for an aircraft that attach fittings were loose. We were able pay attention to the age of them, as they is infrequently flown. The worst-case to duplicate it on the ground. are usually life-limited. installation I inspected had an engine

Deformed pitot tube. Surely we can do better than this for a Look closely and you will see a very common crack on the rear device that is so critical. baffling that is used to support this oil cooler.

Photos: Vic Syracuse KITPLANES October 2016 17 Many builders are surprised to learn that the rear spars actually The flap actuator seen here, and used on many varieties of aircraft have some movement on them due to flight loads and require a for flap and trim actuation, requires safety wire between the castellated nut and cotter key. housing and the bolt in case the locknut should come loose. that had been removed from another Looking for Clues since they were based at an airport with aircraft and had not been run in at least Sometimes it is fun to play Dick Tracy. an elevation of 6000 feet. Not unexpect- 20 years, and the hoses were approxi- On one RV-10 with a nicely painted edly, they were experiencing vapor lock mately the same vintage. This engine was engine, I noticed that one of the bot- unless the electric fuel pump was left on. installed on a high-performance Lancair tom spark plugs was a different manu- I showed them the likely cause and how aircraft, with the planned initial test facturer than the other five. By itself to rectify it. flight on a 3000-foot runway. I politely this shouldn’t be a problem. Someone A thorough inspection of the engine persuaded the builder that it was really a could have dropped a plug, and this was compartment can yield clues as to abnor- risky endeavor, and it might be wiser to the available replacement. But I had to mal operating temps. Hotter than nor- have the engine fully inspected or torn ask. The owner feigned ignorance, but mal temps can usually be noticed by down prior to the first flight. upon later inspection of the logbooks, I brittle hoses, especially the Lycoming By the way, some safety advice here: found an entry that reflected a cylinder intake hoses since they are so close to the Be sure to verify the ignition systems are replacement due to damage from a han- exhaust systems. Intake gaskets can also turned off and ask when the last ground- gar collapse! Interestingly enough, there become brittle and leak. Telltale signs ing check was performed. If unsure, weren’t any details as to cylinder break are usually a blue fuel stain at the top of assume the ignitions are hot and be very in. On the same aircraft I noticed the scat the intake tubes and high EGTs when careful around the propeller arc until tube to the firewall cabin heat box was the throttle is reduced for landing. The the spark plugs have been removed. Ask actually touching an unprotected area of gaskets are fairly easy to replace, and I’ve if the fuel system has been modified in the main fuel line. I asked if they noted had more luck with longevity using the any way and if it has been flow checked any anomalies of fuel pressure during red Superior gaskets as opposed to the to exceed 150% of takeoff power. flight or ground operations, especially original Lycoming black ones.

Never, ever use RTV around fuel or oil as it can dissolve and get High EGTs at idle and rough idling engines can be caused by into the system. leaky intake gaskets or, as in this case, a missing bolt.

18 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes The forward tank attach actually moves, much like the rear spar, and calls for a drilled-head bolt and safety wire. Engine Controls, Baffles, Seals, and Exhaust A surprising number of aircraft I have inspected have less than full move- ment of the engine controls, with the throttle and the mixture being the highest offenders. Most of the arms on the fuel servos and/or carburetors can be drilled with a new hole to allow complete movement from stop to stop. On one particular RV-8 the owner was telling us how fast it accelerated at takeoff, and how he “really had to hold on.” I showed him he had at best 2/3 of full throttle movement on the fuel servo. This was after flying 240 hours and four years, so it was missed on mul- tiple condition inspections. I couldn’t help but wonder if the cylinders were properly broken in, but I did tell him to expect even more acceleration on the next takeoff! The baffles and baffle seals need to be inspected with careful attention paid in a few areas. The baffles must be sealed to the engine (high temp RTV works well here), they must form a tight seal to the upper cowling, they should be free to move between the cylinders, and they must be inspected thoroughly for cracking if they are supporting any weight such as an oil cooler. Attaching an oil cooler to the rear of the last cyl- inder is a common practice, but I don’t like it. It invariably will lead to cracking of the baffling and oil cooler supports. You will find all kinds of information on various forums and boards on how to add cross-members to the engine in order to support the cooler, but if you’ve ever seen some high-speed photography

KITPLANES October 2016 19 Alternator wires should be adequate to supply the full load from the alternator. Normally an 8 AWG or 6 AWG wire will work—definitely not a 14 AWG as discovered here. This hot air duct is way too close to the unprotected part of the fuel line and, in Alternator and Engine Ground with an engine ground of the same fact, was causing vapor lock for the own- The alternator is another item that size or larger than the starter wire. On ers unless the electric fuel pump was left requires some attention. Just as the one very nicely equipped RV-10, there on. Better routing or fully covering the engine has a very big job to do, so does was a 14 AWG wire being used as the fuel line with firesleeve should help. the alternator. It must be capable of main feed from the alternator. It was of cylinder movement while the engine supplying ample power to recharge a not only improperly sized, but also a is running you will realize the futility. battery after starting the engine and potential fire hazard, as it was attached Besides, I don’t really think it is good to then continue to carry the full electri- to a 60-amp alternator breaker. Clearly, be tying the cooler to other parts of the cal load of the aircraft. Today’s all-glass the wire would have melted before the engine that are not moving, such as the cockpits can require steady state 25–30 breaker could have activated. crankcase. Picture a wet dog shaking amps during the daytime and rise to Also check the alternator belt for proper water off. Get the idea? On the other 40–50 amps at night with the pitot heat tension and any signs of wear, and the pul- hand, oil coolers mounted on firewalls activated and lights illuminated. It is ley for alignment with the flywheel. rarely have any cracking problems. important to have the proper size wire Many builders forget to attach a Don’t forget to inspect the upper and with very secure connections, along ground wire to the engine, assuming lower engine cowlings. Check the top cowling for signs of baffle rubbing. It will not only eventually rub through the cowling, but it is a good source of engine vibration transference to the air- frame. The lower cowling, if not prop- erly protected by heat shielding and some form of epoxy paint, will usually show signs of heat and oil damage. Exhaust systems need to be checked for proper mounting and to ensure there are no cracks, especially in welds or under heat muffs. Regular application of mouse milk on all exhaust joints is a really great preventative measure, and I apply it anytime I have the cowling off on my own aircraft. Be sure to check the exhaust nuts and gaskets at the cyl- inder attach points. Magnetos should be checked for proper timing and in the case of Slick magnetos, compliance with Here is a real example of a low compression test that resulted from a sticking valve. Lots the 500-hour service bulletin. of air could be heard coming out of the exhaust pipe.

20 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes safety wire. Speaking of safety wire, there are lots of places in the engine compartment that need safety wire, and often it is missing. On aircraft with Rotax engines there are some inspections required for the gearbox that should be checked and recorded, and there have been numerous service bulletins regarding carb floats and fuel pumps that require compliance. Avionics and Controls Now it’s time to look at the avionics. While current databases aren’t actu- ally required, it is another indicator as Ever wonder why some of those engine sensors are intermittent? Here’s a good example to whether the airplane really is flown of unsupported wiring that will eventually lead to failures. regularly. I like to take my Michel avionics tester to pre-buys. It enables that bolting the engine mount to the Don’t forget to check the propeller me to verify proper operation of any firewall takes care of that. Little do and spinner for proper mounting (regu- VOR/ILS, audio markers, com radios, they realize that the rubber engine lar seasonal torquing of wooden pro- and intercoms. In one case I discov- mounts, which help to isolate the air- pellers is especially important), leading ered very weak volume on the com 1 frame from engine vibrations, also edge damage, and proper lubrication audio, which was caused by a ground electrically isolate the engine. Alter- intervals for certain constant-speed short on the wire to the audio panel. nators will not work without a good propellers. If the assembly has been An improperly assembled back plate ground, and an improperly grounded dynamically balanced, make sure the connector on the rear of the unit was engine can also cause the instrument weights are still attached. The proper the culprit. senders to be very inaccurate. Bad or size and location of them should be Once in the cockpit, a thorough check, improper grounds are usually first found in the aircraft/propeller logbook. much like what is performed during a noticed by poor cranking during start- Constant-speed propellers also have a preflight runup, can highlight any prob- ing, the initial reaction being that recommended TBO, and it should be lems. A potential safety area I often see the battery must be bad. The engine checked. Sometimes it is necessary to in amateur-built airplanes pertains to should be grounded to the firewall via remove the spinner to check for proper control movement. Flight controls need one or more flexible cables. Spark Plugs and Prop Upon removing the spark plugs for a compression check, perform the usual inspection and look for worn, oily, or lead-fouled plugs. They can be indicators of improper operation such as ground leaning, and other problems such as poor sealing piston rings. I always per- form the first compression test on a cold engine, as engines that are flown regu- larly and properly cared for will usually have compressions in the 70s. Sticky or leaking valves and rings are easier to find on a cold engine. If anything is out of the ordinary, I will then run the engine to see if the problem clears itself. If not, further investigation is warranted, and in the case of a sticking valve or contin- ued low compression, follow-up might Removal of the spinner disclosed this disaster waiting to happen. The forward bulkhead be immediately required. was severely deformed due to over-torquing of the propeller bolts on a wooden prop.

KITPLANES October 2016 21 All controls and switches should be appropriately labeled. Here’s an example of an unlabeled button potentially having Imagine your passenger pulling this knob back just as you start serious consequences—the green button on the stick grip was your takeoff climb—yes, it was connected to the throttle. the starter button. to move throughout their entire range managed to accidentally bump it twice the requirement for the operating limi- of motion without interference. I’ve myself while doing cockpit checks! tations to be in the aircraft, and others seen many control sticks, especially on claim they have never seen them or don’t RV-10s, that will activate switches when Paperwork remember where they are. I point out to moved to the full-forward position. I From the cockpit you can begin the them that the airworthiness certificate often wonder who performed the initial final stages of the inspection, and that is not valid without the operating limi- airworthiness inspection, as control stick is the paperwork. Just as in the certi- tations. Far too many new builders find interference should be disqualifying. fied world, the airworthiness certificate them in their original paperwork folder Another problem area pertains to should be visible, and the registration instead of in the airplane. A new set can controls, switches, and circuit break- card should be on board and current, as usually be acquired from the FAA in ers that aren’t labeled. The worst one well as the weight and balance. The word Oklahoma City if needed. Don’t forget had an unlabeled starter button on the “Experimental” should be visible at the the passenger warning label required in control stick. I did manage to convince entry to the cockpit, and the operating view of the passengers. the new owner to remove it before a pro- limitations should be on board as well. Next are the logbook inspections. I peller inadvertently struck someone. I Too many non-builders are unaware of want to see that Phase I was appropri- ately signed off (the proper wording is in the aircraft operating limitations), and I want to know who did the flight testing and what exactly was done. I inspected one aircraft that had been flying over seven years across three owners and never had Phase I been signed off! There have been times when I really question the thoroughness of the Phase I testing, especially including loading at different weights and CGs. Some builders have

figured out that it is easier to copy XV

and VY from other internet pilot oper- ating handbooks, rather than take the time to correctly determine them for their specific aircraft. While in the logbooks, other entries should include the required transponder and static checks, a check for comple- tion of any applicable service bulletins or ADs, and any notated repairs from dam- age. Also, check for any major changes The control sticks should never have interference with anything in the cockpit. This one that perhaps should have required the should never have received an airworthiness certificate in this condition. aircraft to go back into Phase I. As an

22 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes example, the requirement to notify the FSDO when changing from a fixed- pitch propeller to a constant-speed pro- peller is one that is often overlooked. Flight Test Once I’ve determined that the aircraft is in a safe, legal, and airworthy condi- tion, it is time for a flight test. I like to watch the owner operate it as it gives me real insight as to the owner’s confi- dence with the aircraft. I can also spend more time focusing on the engine and flight instrumentation to verify proper operation. Engines should run within normal operating temps as per the manufacturer of the engine, so it is a good idea to familiarize yourself with those specifications prior to the flight. Engines that reach maximum operating temps within a few thousand feet of the ground probably do not stand a good chance of reaching TBO. Flight con- trols and trim should be approximately neutral in cruise flight depending upon CG and loading, and there should be no required adverse control inputs required when flaps are deployed. One RV-10 that had flown for over 80 hours required so much right rudder pressure in cruise flight that my leg was actually cramping after 20 minutes. I eventually determined that the cap on the verti- cal stabilizer was offset 3/8 inch and was acting as a fixed trim tab. Removal and replacement with proper alignment fixed the problem. Listen for changing engine/prop vibrations at various rpm, and verify accuracy of the aircraft tachometer with an optical tachometer from the cockpit. This is especially important on aircraft equipped with propellers that have restricted rpm ranges. Don’t forget to ADS600-EXP check the radios for clarity and func- ADS-B Tra c tionality. I like to turn the radio squelch UAT OUT & IN off to check for any ignition noise. On & Weather well-equipped airplanes I will verify • FAR & TSO compliant a ordably priced that an autopilot-coupled approach • Internal WAAS GPS at only $1,399 really does work as expected. So there you have it. By following this • Keep your XPDR guide to purchasing an Amateur-Built • Wi-Fi to devices aircraft, you should feel confident that www.NavWorx.com there shouldn’t be any major surprises 1-888-628-9679 soon after you bring it home.J

KITPLANES October 2016 23 Getting High OFF Grass Flying organically with turf runways. By LeRoy Cook

When I started flying, runways were about launching from a grassy hum- These are the two biggest points to keep predominately unpaved; I recall being mock after a few bounds of takeoff run, in mind when contemplating the use of startled by my first landing on asphalt climbing away from a flying field that is, a grass runway: They aren’t all the same, when I heard the tires spinning against in fact, a field. Rolling one’s tires into and they are always in a state of change. an aggregate surface. Since most of my the brush of clipped turf is like being If you’re like the majority of today’s early experience was with turf airports, received by welcoming arms; you are pilots, you learned to fly from a paved I learned to deal with the peculiarities of forgiven for slight misalignment and strip, and you’ve flown mostly to other operating from grass. Nowadays, land- uncorrected crosswind drift, the turf’s paved runways. You can pretty much ing on sod is very much the exception, lubrication allowing a minor faux pas take it for granted that each one will rather than the rule. With pavement, we without squeal or screech. be relatively level, free of potholes, and are accustomed to coming and going at Now, having said all that, we have to about like it was the last time you used will, seldom giving a thought to runway understand the limitations that come it. The airplane’s stopping and accelera- condition unless it’s contaminated by with unpaved operation. The bliss I’ve tion performance will be much like you slick white stuff. described above applies to good grass run- expect at home. By comparison, when It is a fact that good grass runways ways…and they are rare. All too often, the you land on dirt, you must stay alert, are friendly, inviting places for aircraft, little open circle on your chart turns out proceed with caution, watch for danger especially those of the tailwheel per- to be a neglected piece of native sod, per- signs, and add safety margins to your suasion. There’s something elemental haps once cared for but no longer loved. normal distance requirements.

24 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes Why so? Because grass runways are living organisms. They absorb water, rather than just shed it. Critters can bur- row into and excavate the surface, both to find a meal and avoid becoming one. The sod covering grows, if conditions are right, and unless it’s given regular hair- cuts it will become dense and tall enough to entrap your landing aircraft. In cold weather, freezing and thawing cycles will turn the top layer into pie filling. Expect to encounter some unusable periods in the annual life cycle of a grass airport. Know Before You Go Private grass strips can range from perfectly manicured lawns to unmowed turf or recently mowed hay fields. They can look different from far away or up close—so always It’s best, then, to check with the locals be ready to go around if the surface isn’t to your liking. before you fly into a strange grass field or, better yet, visit it on the ground to verify Bear in mind that simply seeing a pri- invited to visit a private strip, make the its condition. Naturally, if it’s a private vate airport marked on a sectional chart first landing with someone who’s famil- restricted-use airport, you must contact carries no implication of its safety or suit- iar with it, riding shotgun to warn you of the owner to seek permission anyway. ability of use. When the FAA lists a land- hazards. If the grass strip is a supplemen- Such permission is almost always stated ing facility as private-use, not open to the tal crosswind runway at a paved airport, as “use it if you want to,” which you public, there are no standards applied, be sure to check for NOTAMs and watch should take as an invitation to operate at other than marking it as “objectionable” for X’s indicating that it’s out of service. your own risk. Make sure you ask about if there’s a possible conflict with prior use Is your airplane suitable for unpaved tribal-knowledge details; is one end of the airspace. Public-use airports are surfaces? Most tailwheel airplanes with rougher than the other, are there ditches checked for hazards and denied such sta- full-size (6.00x6) tires can negotiate to avoid, what kind of obstructions will tus if found unsuitable, but a private field well-maintained grass strips. If you have be encountered on approach or depar- can have power lines, a drainage culvert, a nosewheel, make sure it’s robust enough ture? Even determining the exact orien- a dog-leg bend in the runway, or mere to take the extra punishment of jouncing tation of the runway can require some hundreds of feet of usable length. Safety over uneven surfaces, and that you can guidance, unless it’s marked prominently is the owner’s prerogative. apply enough up-elevator to lighten its with edge indicators. Grass fields look load. Be sure you have plenty of propel- like what they are—grass fields. Don’t Should You Use It? ler clearance to avoid hitting the surface land across the fence in an adjoining pas- For the above reasons, it’s better to use when pitching over the hummocks. ture by mistake. only public-use grass runways. If you’re Many homebuilts have smaller tires and spindly nosegear struts, to enhance speed and simplify construction. These should be used only on the best-kept grass strips, not landed out in the rough. Likewise, tight wheel fairings won’t last long in the bush. Floatation is impor- tant when using soft surfaces, like rain- soaked turf or sand. Be aware that your paint and belly or flap skins can suffer damage from stones thrown back by the propeller and tires. Try to keep moving to minimize pro- peller blade nicks from pebbles drawn up under the prop disc. Stop only on grassy areas, not bare patches that might be rocky. If you feel the aircraft begin to bog down in a soft spot, hold the stick Most tailwheel airplanes intended for non-paved airport operations have 6.00x6 tires, or back and apply extra power to keep mov- better yet, 8.00x6. ing with the nose up, until you reach

Photos: LeRoy Cook KITPLANES October 2016 25 firmer ground. You’ll have to taxi slower than you would on pavement, to avoid excessive stress to the gear, and it’ll take more power than usual to drag the tires through heavy grass, leading to overheat- ing during a long taxi. Make sure the runway length is ade- quate, and by that I mean add at least 50% to the takeoff run you expect on a paved runway. Much depends on the soil condition, the height of the grass, the type of grass, and the roughness of the surface; the latter can cause enough bouncing to disrupt airflow over the Some grass runways have seen better days. Healthy turf interspersed with bare dry wing during takeoff. Naturally, use max- spots can create a very rough ride. imum-effort soft-field flap settings and technique during takeoff and landing. should correlate with any runway bound- heavy rains, another place you don’t want Expect braking to be less than optimum, ary markings you see, along with an out- to go. Don’t just land without looking; particularly on wet grass. line indicating regular mowing. In the make a pass over the field at traffic -pat The best asset for operating on an absence of any of these things, proceed tern height and, if not satisfied, “drag the unpaved runway is a slow takeoff and with utmost caution. field” at 200 feet for a closer look, keep- landing speed. If your airplane needs Water glinting in the sunlight signals a ing speed well above stall. 60 knots or more to fly, you’ll want to warning to stay away; if most of the strip Be ready to go around if you spot dan- stick to only the best grass strips. If you appears dry, roll out and taxi only where ger at the last second, even after you’ve have retractable gear, restrict your opera- there’s no visible water. You don’t want touched down and feel the tires dig- tions to just occasional visits to the very to harm the airstrip’s surface by cutting ging into soft mud. If you make ruts, best turf runways. Aircraft that were ruts, and you could damage the aircraft, keep the plane moving until you reach designed in the 1950s very likely had or even flip over if it’s very soft. firmer ground, then walk back to tamp grass airports in mind. If your aircraft If the grass is waving noticeably in down the edges of your ruts after you’ve originated in the 1970s, it probably was the wind, it’s probably too tall to use for parked. It’s the considerate thing to do, built primarily for pavement. landing or takeoff. Some owners like to so the next pilot won’t encounter your get a hay crop from their runway each hardened divots with his landing gear. What Are You Looking For? year before putting it to use. Similarly, avoid locking a brake to spin Your protection against grass field haz- Discolored, dark-shadow areas may around, which can tear up the turf. ards must be your eyeballs. As you fly indicate mole hills, gopher holes or old over, note the coloration of the surface, ruts from careless pilots. Avoid these, Rolling Your Own a lighter shade denoting where most of along with any rock outcrops you see, Interested in using your own property the traffic has worn down the grass. That and look for washed-out bare spots from for an airport? Not so fast; you can’t just

26 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes Introducing The B-Models

Make your first landing on a private grass strip with someone who is familiar with it riding shotgun to warn you of any hazards. More of What You Want mow off a piece of pasture and start land- Expect to wait awhile before begin- ing there. FAR Part 157, a relatively short ning to use the strip—like a full growing • More Room and Comfort • More Panel Space (for an FAR) piece of legal code, requires season, so the new grass can get estab- • More Fuel that you notify the FAA 90 days before lished after planting. A good lawn seed- • More Engine Choices starting work on your airport, filing the ing, worked in and kept watered, takes • More Standard Features • Less Build Time! appropriate paperwork for review. For time to cover bare soil. Keep the grass • Same Great private use, there isn’t likely to be any mowed short, so it’ll spread and grow Flight Characteristics! objection unless it interferes with other dense. You can’t use a common tractor- use of the airspace. You may even decline pulled brush-hog rotary mower that only www.SonexAircraft.com to have your strip designated on the chart. clips the tops; you’ll need a commercial 920.231.8297 The FAA’s airspace determination finishing mower that does a nicer fair- doesn’t obviate any local codes and ordi- way-style mowing. nances that your state or jurisdiction Most importantly, have access to a has on the books. Don’t do a lot of work roller and use it regularly, preferably only to find that you aren’t permitted to after a light rain has soaked up the top have an airport in your township, or that of the soil. Rolling packs the looser soil you’ll first have to hold public hearings and encourages the grass to spread; with independent SERVICE CENTRE on the matter. it, you have a billiard-table landing sur- Now to the practical matters; land face. Without it, you’ll get bone-jarring AIRCRAFT ENGINES in its natural state is rarely suitable for a clumps of grass and an uneven runway. landing facility. For good drainage, you Remember, driving over your turf run- OVERHAUL SERVICES need to move dirt to not just level the way with 17-inch automotive wheels has surface, but to build a crown with gentle nothing in common with six-inch air- TECHNICAL SUPPORT slopes that won’t hold rain or melt water. plane tires rolling at 60 mph. Even the Don’t skimp on width, as well as length. best grass runway imposes added stress ANNUAL INSPECTIONS You may find a 50-foot runway width on the airframe; a poorly-maintained adequate for a paved strip, but you should strip has the potential to damage the air- ROTAX PARTS note that there’s usually 100 feet or so of craft in only one landing. safety area on each side before encounter- Be prepared to restrict your use of the ROTAX CLASSES ing ditches or undergrowth, allowing for runway when it’s wet or thawed out, even inadvertent excursions. Plan on grading after taking a year or so to get the sod 24/7 ONLINE ORDERING 100 feet of width, for those crosswind established. Patience is needed when fly- days. As far as length goes, double what- ing from grass; if you have to be capable ever you think you need; obstructions of flying anytime you want, keep your in the approach paths will block much plane on a paved strip. of the runway’s length, even if only a tall There’s nothing nicer than having your fence. Light planes can get by with 2000 airplane at home, on a beautiful, inviting feet at low elevations; a half-mile is better, greensward. It does, however, take consid- CALL 1-800-247-9653 • WWW.Cps-pArts.Com 3000 feet is great. erable work and respect for limitations. J TECH SUPPORT HOTLINE: 951-317-8677

KITPLANES October 2016 27 A Custom Maintenance Manual for a Custom Aircraft It may not be required, but it’s essential for performing thorough inspections. By Katie Bosman Krotje

When my husband and I bought a wonder why more people don’t take the Experimental/Amateur-Built aircraft. beautiful flying RV-8 a few years ago, time to organize their paperwork into a But just because it’s not required doesn’t we were thrilled when the seller brought working maintenance manual for their mean it’s not a good idea. The FAA and out a large, musty cardboard box full of custom airplanes. Transport Canada recognize “lack of documentation. Inside was a marvel- I can hear the mutterings flowing knowledge,” mainly lack of current and ous jumble of important stuff—receipts from every T-hangar armchair and air- correct instructions for maintenance from the original kit components, the port bathroom. “Me? Write a mainte- tasks, as one of the “dirty dozen” pitfalls full set of plans, manuals for the pro- nance manual? Come on! I’m a builder, of human factors that cause maintenance- peller and engine, electrical diagrams not a writer.” Or…“I’m a pilot, not an related accidents. This situation has been for the professionally-wired panel, and engineer.” Or my personal favorite… listed by the NTSB as a contributing fac- more. It made us confident in the pur- “I’m an engineer, I can write anything.” tor in accidents of vintage aircraft, includ- chase because the collection was much Uhh… sure you can, friend. Honestly, ing Harrison Ford’s well-known forced more complete than other aircraft we’d to do this, you don’t have to “write” a landing in his Ryan PT-22. It is also a haz- looked at in our search, which often comprehensive paragraph. Any aircraft ard for maintainers of custom-built kit air- only had a set of logbooks and maybe owner can create useful maintenance craft, for which there is often no manual at the original plans. As far as a usable set documentation just by doing some all—and one reason many A&P mechan- of documentation, however, the mar- research and compiling their existing ics simply refuse to work on them. velous jumble was just that—a jumble. information in a meaningful way. In terms of safety, a detailed set of Looking up anything useful was akin I know it seems like a daunting task, inspection checklists is even more valu- to an archaeological dig. It made me and it’s not even required in the U.S. for able than the manual. By taking time to

28 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes think about the inspection and mainte- nance items that are important for the longevity of your particular airframe and engine, your condition inspec- tions will really take on a new level of quality—a level above and beyond the required “scope and detail of CFR Part 43, Appendix D,” the generic catch-all inspection list in your operating limita- tions. Just the act of compiling the man- ual will make you more aware of what needs to be done, and your checklists will serve as important future remind- ers. Your creation is a custom aircraft— so why trust it to a one-size-fits-all, government-issued checklist? If you need to hire out your condition inspections, a complete set of maintenance docu- mentation will save your mechanic’s time and your money. To Begin: Find a Good internet free of charge. For example, 4. Engine Example to Copy do a search for “Cessna maintenance 5. Fuel system The first step is to find an existing -out manual,” and you’ll come up with sev- 6. Propeller line and fill in your relevant informa- eral links. It might help you to cruise 7. Landing gear tion. You could get lucky and find a through a complete manual to see what 8. Utility systems (such as cabin nice manual that someone has already type of details were included. heat and ventilation) A Custom Maintenance Manual made public for your type of airplane. The following list is a typical general 9. Instruments If not, certificated and Light Sport Air- outline, with the majority of each sec- 10. Electrical system craft make good examples because their tion containing complete component 11. Paint and coatings for a Custom Aircraft manuals are subject to a strict set of descriptions, diagrams, and maintenance requirements. Some LSA manufacturers procedures. Remember, the beauty of Step 2: Build the Structure publish their manuals for free download Experimental aviation is that none of this Using the Obvious on their web sites. If your aircraft has a is required—you can pick and choose Once you have your outline laid out, it’s factory-built LSA counterpart, most of what’s important to you. time to organize what you already have. your work will already be done for you. 1. General information (such as tire You may want to compile your manual If you have a different engine or avion- inflation, required fuel and oil on the computer in the form of PDF ics package, you can substitute your own grades, ground handling, etc.) files. This is a great option because you relevant information. 2. Airframe components and can keep all the materials up to date You can also find old certificated structure without spending money on printing, aircraft maintenance manuals on the 3. Flight controls plus you can easily keep multiple copies. One meticulous builder-pilot I know keeps a copy of his entire maintenance manual on his iPad and carries it with him wherever he flies. He is one of those Boy Scout types. If you want to keep a paper copy, it will take more space and more money, but get a couple of sturdy three-ring binders at least 3 or 4 inches thick, some divider tabs, and start digging up your paper component instructions, plans, and engine and avionics manuals. If you’re like me, they’re scattered from your office to your T-hangar, your living room, and everywhere in between. Place each publication in its relevant section, You probably know the old adage, “When the weight of the paperwork equals the weight and soon you’re off to a great start. Min- of the aircraft, it will fly.” Maintenance documentation counts! iature-sized preview plans, such as those

Photos: Katie Bosman Krotje KITPLANES October 2016 29 RV-3B N9JX—50-Hour Inspection Checklist published by Van’s and Zenith, are per- fect for this type of situation. Date: From there, it’s time to do a little Aircraft total time: research. Go to the internet and see if Engine total time since major overhaul: you can find any required maintenance Engine total time since top overhaul: items, such as service bulletins or air- Magnetos total time since overhaul: L: R: worthiness directives, that apply to your Last oil change completed: aircraft, engine, and avionics. Compli- Before Inspection ance with airworthiness directives on ❑ Remove cowling, forward half of wheelpants, and spinner. certificated components are not required ❑ Wipe down the aircraft engine. for Experimental aircraft, but important to know and consider. Many mechanics Engine and Cowling will not sign off a condition inspection ❑ Check cowling for hinge security, cracking, oil stains on the inside (if found, investigate until all ADs are complied with, no mat- source of leak). ter what type of aircraft it is. ❑ Baffles—check condition and security. ❑ Run engine up to operational oil temperature. Check for rough running or abnormal Step 3: Complete the indications. Check all engine controls and instruments for normal operation. Custom Touches ❑ Drain old engine oil and remove filter. Cut open filter and check for metal particles or Go through each section and add your foreign matter on oil filter and sump drain plugs. Install new filter and new oil. own content to describe in detail your Oil type used: off-plans excursions. Proud of your hid- ❑ Engine section—check for visual evidence of excessive oil or fuel and sources of such leaks. den cowl pins or retractable steps? This is the place to use your catalog of bar- ❑ Engine mount—check for areas of chafing. Check for cracking around landing gear leg napkin concept drawings and build-log attach areas. photos. The more detail, the better. ❑ Engine controls—check for defects, improper travel, and improper safetying. Pay special attention to your electri- ❑ Lines, hoses, and clamps—check for leaks, deteriorating condition and looseness. cal system, which is probably the most ❑ Exhaust stacks—check for cracks, defects, and improper attachment. customized and least documented of ❑ Accessories—check for oil leaks, worn/rotten alternator belt, apparent defects in security all Experimental aircraft systems…even of mounting and wiring. though proper flow of electrons is essen- ❑ Overall —good look-over to check general condition. tial to modern flight instrumentation Landing Gear and even some engines. From the most ❑ Tires—check for proper inflation (40 psi), wear, cuts, abrasion due to possible wheelpant simplistic generator/battery/starter sys- tem to complex mazes of buses, batteries, clearance issues. and computers, this is the stuff that will ❑ Brakes—check for proper adjustment and condition of pads/rotors. most likely cause you to want to bash in ❑ Wheelpant attach brackets—check for condition, cracks, security, nutplate security. the cowl with your head when compo- ❑ Tailwheel—check for proper attachment and condition of chains, steering arm, and nents start to fail. If you had your panel tailwheel spring. built by a professional, you’ll have a ❑ Tailwheel tire—check for wear. beautiful wiring diagram to place in this Propeller and Spinner section. If not, then use whatever plan ❑ Propeller assembly—check for cracks, nicks, delamination, nickel leading edge security, you had when you wired the airplane. and general condition. Even a simple spreadsheet detailing pin ❑ Bolts—check for proper torque value and safety wire. and serial port assignments and wire col- ors for various components can be a big ❑ Aluminum spinner condition—Examine skin for dents. Examine all screw holes for help later on, after labels fade and you’ve fatigue cracks. forgotten which wires run where. Avionics ❑ EFIS software—Check date of current software. Update navigation database and EFIS Step 4: The Inspection Checklists software, if applicable. This is perhaps the most important section of them all, one that will Before Reassembly prove its usefulness every time you do ❑ Run engine up to temperature on the ground, then shut down and perform visual a preflight, oil change, and condition inspection for leaks. When satisfied that oil pressure is within limits and no leaks are inspection. This section can be as basic present, reinstall cowl and wheelpants. as the relevant parts of Appendix D of

30 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes found by other owners in the field, but not formally acknowledged by the kit manufacturer. Your inspection check- lists should grow over time as you learn about your airplane and its fleet. As the years go by, keep the completed check- lists as part of your ongoing mainte- nance records for the airplane. Think about how much more valuable this will be to future buyers than a series of simple logbook endorsements. It’ll be Fun—Really! Studying a wiring diagram before getting into this position is a good idea. So, yes, this project will take some time. But quality time spent now should save you Part 43, but ideally, it’s a custom-writ- gear, and avionics, along with special time, money, and frustration later. It could ten set of inspection and service items airframe requirements. Note due dates even head off an in-flight issue somewhere for your own airframe and engine— and hour limits on time-limited com- down the road because your inspections even periodic software updates for ponents, such as a 500-hour mag service will be more thorough and consistent. your avionics package. and 24-month transponder check, so I’ve created a sample set of checklists for Sometimes you can get a suggested they don’t go forgotten. Include special my Van’s RV-3B based on Appendix D to type-specific condition inspection check- inspection of custom features, like those Part 43 (see sidebars). Try editing them to list from the kit manufacturer or from retractable steps, to monitor their dura- fit your own airplane. I’ll bet you’ll find it experienced members of type-club bility in service. There will also likely be a easier than you ever imagined to create a groups. If not, start by copying the text list of vulnerabilities, such as hot spots for useful custom maintenance manual to go of Appendix D to a blank word process- fatigue cracks, that have been occasionally with your beautiful custom aircraft. ing document. Go through and delete everything that is not related to your aircraft, like envelopes, gas bags, and trailing antennas (unless you fly a Zep- pelin or a Super Constellation). Then, start adding things that are important to you. Include all the items that are spe- cific to your engine, propeller, landing Katie Bosman Krotje Katie Bosman Krotje is a commercial pilot, CFI, and holds a master’s degree in aerospace education. She is building a Van’s RV-3B, studying for her A&P test, and has written maintenance manuals for two Special Light Sport Aircraft models.

KITPLANES October 2016 31 RV-3B N9JX—Annual Condition Inspection Checklist Date: Aircraft total time: Engine total time since major overhaul: Engine total time since top overhaul: Magnetos total time since overhaul: L: R: Last oil change completed: Before Inspection ❑ Remove or open all inspection plates, access doors, forward fuselage top skin, empennage fairing, wing root fairings, wheelpants, gear leg fairings, and cowling. ❑ Thoroughly clean the aircraft and aircraft engine. Fuselage ❑ Skin—for corrosion, distortion, other evidence of failure, and defective or insecure attachment of fittings (rivets, screws, etc.). ❑ Systems and components—for proper installation, apparent defects, and satisfactory operation. Cabin and Cockpit ❑ Generally—for uncleanliness and loose equipment that might foul the controls. ❑ Seat and safety belts—for poor condition and apparent defects. ❑ Canopy—for deterioration and breakage, particularly around areas of anchor screws. Inspect canopy latch mechanism for proper attachment and operation. Inspect hinge and anchor cable for condition, signs of stress, or cracking. (Master/instrument/lighting switches on) ❑ Instruments— condition, mounting, marking, and (where practicable) proper operation. Check for accurate fuel quantity. ❑ External lighting—Check for proper operation of navigation lights, landing/taxi/wig-wag lighting. (All switches off) ❑ Flight control stick—for proper installation, fastener security, and proper operation. Check aileron trim springs for security and rigging. Special item (VAF, 12/2015): Sit in seat and listen carefully for sound of dragging pushrods through seats and formers. If sound is present, investigate for areas of rubbing and pushrod damage. ❑ Pitch servo—check servo mount bracket for deformity, security. Check rod end bearings, fastener security, overall servo condition. Check for control over-center condition at full elevator throws in each direction. Check for loose wiring that can foul the control arm. ❑ Elevator trim cable—for smoothness of operation and lack of slop or binding. ❑ Manual flaps—for smoothness of operation, crisp detents, lack of binding, proper operation. ❑ Battery—check overall condition, proper installation, proper charge. ❑ Brake master cylinders—check for leakage. ❑ Cabin vents—check for proper operation, security. ❑ Smoke system—check for leaky fittings, security of tank, pump, wiring. ❑ All other systems—for proper installation, general condition, apparent and obvious defects, and security of fastener attachment. Engine and Cowling ❑ Check cowling for hinge security, cracking, oil stains on the inside (if found, investigate source of leak). ❑ Baffles—Check condition and security. ❑ Run engine up to operational oil temperature. Check for rough running or abnormal indications. Check all engine controls and instruments for normal operation. While the engine is still hot: ❑ Check cylinder compression. If there is weak cylinder compression, check for improper internal condition and improper internal tolerances. Record of cylinder compressions (differential compression): #1: #2: #3: #4: Notes:

❑ (Skip if completed within previous 3 months or 35 hours) Drain old engine oil and remove filter. Cut open filter and check for metal particles or foreign matter on oil filter and sump drain plugs. Install new filter and new oil. Oil Type Used: ❑ Spark Plugs—Remove, inspect, clean, regap, reinstall or replace as necessary. Inspect all ignition leads for security, chafing, and condition. Spark plug torque: 35 foot-pounds. Gap: .016–.022 inch ❑ Engine section—for visual evidence of excessive oil or fuel and sources of such leaks. ❑ Studs and nuts—for improper torque and obvious defects.

32 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes ❑ Engine mount—for cracks, areas of chafing, looseness of mounting, and looseness of engine to mount. Check for cracking around landing gear leg attach areas. ❑ Flexible vibration dampers (Lord mounts)—for poor condition and deterioration. ❑ Engine controls—for defects, improper travel, and improper safetying. ❑ Lines, hoses, and clamps—for leaks, improper condition and looseness. ❑ Exhaust stacks—for cracks, defects, and improper attachment. ❑ Accessories—for apparent defects in security of mounting. ❑ All systems—for improper installation, poor general condition, defects, and insecure attachment. Landing Gear ❑ All units—for poor condition and security of attachment. ❑ Main gear legs—for undue or excessive wear, fatigue, corrosion, and distortion. ❑ Hydraulic brake lines—for leakage. ❑ Wood gear leg stiffeners—for condition, cracking, attachment and deterioration. ❑ Wheels—for cracks, defects, and condition of bearings. ❑ Tires—for wear, cuts, abrasion due to possible wheelpant clearance issues. ❑ Brakes—for proper adjustment and condition of pads/rotors. ❑ Wheelpant attach brackets—for condition, cracks, security, nutplate security. ❑ Tailwheel—check for proper attachment and condition of chains, steering arm, and tailwheel spring. ❑ Tailwheel tire—check for wear. Wing Assembly ❑ Spar box area—for poor general condition, distortion, evidence of failure, and insecurity of wing bolt attachment. ❑ Wingskins—for evidence of overstress, smoking rivets, etc. ❑ Wingtips—for condition, security, cracks, loose/missing screws. ❑ Wingtip lighting and landing lights—check condition and security of units and lenses. ❑ Fuel tanks—sump tanks for evidence of contamination. Inspect inside for evidence of Pro-Seal failure. Inspect bottom surfaces, patch (right tank), and tank ends for evidence of leaks. Check security of fuel caps and sump fittings. ❑ Flaps and ailerons—inspect condition of skins and security of attachment. Verify proper travel and engagement of control stops. ❑ Aft spar web—inspect for cracks per Van’s SB 16-03-28. ❑ Aileron bellcranks—check for lack of binding, security of bearings and pushrods. ❑ Roll servo—check servo mount bracket for deformity, security. Check rod end bearings, fastener security, overall servo condition. Check for control over-center condition at full aileron throws in each direction. Check for loose wiring that can foul the control arm. Empennage ❑ Inspect general area and aft deck for skin deterioration, distortion, evidence of failure, insecure attachment, improper component installation, and improper component operation. ❑ Horizontal stabilizer front and rear spars—inspect security of attach bolts. Visually inspect longerons under forward mount brackets for cracks, deformities, loose hardware. ❑ Inspect horizontal stabilizer forward spar web for cracking near flange (SB for other RV models). ❑ Inspect vertical stabilizer front and rear attach bolts for security. Inspect spar web for cracking near lower end of spar flange (NTSB, 2015). ❑ Inspect elevator spar webs for cracking near hinge bearing nutplates (Van’s service bulletin SB-14-02-05). Enter findings in aircraft logbook per SB. ❑ Inspect elevator trim tab for security, sloppiness, hinge condition, binding, control horn wear, and control cable security. ❑ Inspect rudder and elevator skins for signs of cracking near aft ends of stiffeners (VAF). ❑ Inspect rudder and elevator control horns and hinges for signs of control binding, bearing failure, pushrod attachment, proper travel, engagement and security of control stops. Propeller and Spinner ❑ Propeller assembly—for cracks, nicks, delamination, nickel leading edge security, and general condition. ❑ Bolts—for proper torque value and safety wire. ❑ Aluminum spinner condition—examine skin for dents. Examine all screw holes for fatigue cracks. Avionics Bay ❑ Open forward fuselage skin and inspect rear of instrument panel and LRU shelf. ❑ EFIS, radio, transponder, ADS-B receiver, engine analyzer, GPS antennas—check units and wiring harnesses for proper installation and secure mounting. ❑ Wiring and conduits—check for proper routing, secure mounting, bare wires, chafing, loose/broken connections. ❑ External antennas—check condition, security of mount, and operation. ❑ EFIS software—Check date of current software. Update navigation database and EFIS software, if applicable. J

KITPLANES October 2016 33 Balancing Act

Troubleshooting vibration problems in homebuilt airplanes. By Matthew Dock

34 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes You spent countless hours assem- bling your homebuilt airplane, paying great attention to detail. No detail is too small to merit your attention because you want everything to be perfect. Your hard work and effort is a remarkable example of precision craftsmanship, and you’re pleased with the finished result and proudly show it off. The plane is a joy to fly, but as you do, you can’t help but notice a vibration. The signs are unmis- takable: there’s a “rough” rpm range, the visors shake, the compass won’t settle, or maybe your feet get numb during a long cross-country. At first, you may try to rationalize Fatigue cracks, such as the one shown here, are symptoms of vibration. the existence of a vibration because, after all, piston engines do vibrate. But • There is an rpm range that is rough. is mounted. The reason is simple: Stati- the surprising truth is this: Vibrations • You experience a “shiver” in your cally balancing a prop doesn’t account are most often the result of an imbal- airplane as you reduce rpm prior for the entire rotating mass of the prop anced propeller assembly and not from to landing. assembly. Once a statically balanced combustion. Vibrations—even small • Rivets loosen. prop is mounted, dynamically balancing ones—can damage engines, airframes • Fatigue cracks appear or existing can detect an imbalance anywhere in the and instruments. ones grow. assembly and enable resolution. Evidence of this comes from a 1973 • Visors shake. Sometimes, owners dynamically bal- study* commissioned by the Army Air Surprisingly, many owners experience ance their props and still a vibration Mobility Research and Development some of these vibration symptoms, but problem persists. There are owners who Laboratory. The study looked at the don’t link them to a vibration problem have embarked on multi-year quests reliability and maintainability differ- that is damaging their airplane. They’ve to troubleshoot a hard-to-diagnose ences of two groups of helicopters with simply lived with the symptoms and vibration. You don’t have to do much distinctly different vibration character- assume they are normal, so the vibra- searching online to find forum posts istics: One group was fitted with vibra- tion doesn’t get their attention. It’s from owners pleading for ideas and tion-reducing rotor-mounted absorbers, not uncommon for servicing, often help. Many have removed, cleaned, and the other wasn’t. In the study, the failure prompted for reasons other than vibra- synced carbs; rebuilt engine mounts; dis- rate for the group fitted with the vibra- tion resolution, to identify vibration as assembled and re-shimmed gearboxes; tion absorbers was 48% lower and cor- the root cause of a problem. When it is rective maintenance was 38.5% lower. resolved, owners often feel as if they’re Fortunately, diagnostic technology flying a new airplane and are amazed at Vibration Survey exists that allows homebuilt owners how smooth flying becomes. to easily identify and resolve vibration Other owners are more sensitive Equipment problems. The end result is a smoother, to vibrations, and when they become Like many technology solutions, the safer flying experience. aware of one, they embark on a quest to systems for dynamic propeller balanc- find and vanquish it. When propeller ing and vibration analysis have become Looking for Trouble assembly imbalance is the culprit, relief more accessible to kit builders as they get The first step is to complete a baseline comes from dynamically balancing the cheaper and easier to use. The equip- vibration survey to see what vibrations prop, and most of the time, the prop is ment used in the case study mentioned exist. Since vibrations aren’t always obvi- the cause of vibration. It’s pretty easy to in this article was the DynaVibe GX2 from ous, pilots and owners must learn to rec- detect and resolve prop imbalance with RPX Technologies. Other analyzers are ognize symptoms such as these: the proper diagnostic equipment. available by searching online. Some, but • Your arms, legs, or feet get numb If there is a “gotcha” where prop bal- not all, dynamic balancers are capable of during a cross-country. ancing is concerned, it is the belief that full-spectrum vibration analysis. When • Your compass jiggles or won’t static balancing is all that is necessary. searching for solutions, make sure the one settle down. Statically balancing a prop is a great you choose can perform full-spectrum • Instrument needles vibrate. start, but a prop that is only balanced vibration analysis. • Avionics randomly fail. this way can still cause a vibration once it —M.D.

Photos: RPX Technologies KITPLANES October 2016 35 Mounting location for the first accelerometer on a Rotax 912 Mounting location for the second accelerometer on a Rotax 912 engine. engine. or even all of these—and much more— spectral analysis is the approach that will particular situation, some of the engines to no avail. pinpoint other vibration sources, such this manufacturer was using were exhib- The frustration of these owners is as: a weak cylinder, unbalanced carbu- iting vibration, and a significant amount understandable. But they’re right to retors, a loose or cracked intake hose, of time and expense had already been relentlessly pursue a solution because an alternator problem, belt resonance, spent searching for the source. the effects of aircraft vibration are all gearbox issues, an oil-canning spinner, The symptom was engine roughness negative. Vibration creates fatigue that propwash, and other causes. in the mid-rpm range that produced reduces the life of the airframe, engine, Spectral analysis, commonly referred noticeable vibration. The vibration was and instruments. Furthermore, when to as a vibration survey or vibration anal- diminished or unnoticeable at cruise a vibration exists, some of the energy ysis, measures the frequency of vibrations rpm. A series of trial-and-error main- meant for propulsion is directed toward coming from an airplane. Vibration tenance procedures were unsuccessful shaking the airplane, and a vibration frequencies are associated with known in resolving the vibration, and contin- can even steal enough energy to cause causes or sources, so once the frequency ued speculative service work was both a loss of horsepower. Identifying and is known, the list of potential causes nar- costly and unproductive. The manufac- resolving vibration not only results in rows to few or one, eliminating the need turer was eager to pinpoint the vibra- a smoother, safer flying experience, for speculative and potentially expensive tion source and hoped that vibration it extends the life of the aircraft and maintenance actions. analysis would identify what had so far enables peak performance. A case study of a kit aircraft manufac- been elusive. turer that contacted RPX Technologies, RPX Technologies visited the air- Troubleshooting Complex Vibrations a vibration analyzer solution provider, craft manufacturer that owned a When dynamic propeller balancing illustrates how spectral analysis identi- DynaVibe GX2 vibration analyzer. doesn’t resolve a vibration problem, fies complex vibration sources. In this The analysis process began by setting

Running up the engine to cruise rpm to collect vibration survey Collecting vibration survey data with the DynaVibe GX2. data.

36 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes Mounted photo tachometer (yellow) aimed at the reflective tape The full setup for vibration analysis on a Rotax 912 engine. applied to the spinner plate. up the engine with a photo tachometer magnitude of the detected vibrations in A 2.43-per spike is typical for these and two accelerometers. One acceler- Inches Per Second (IPS). engines, and it typically diminishes sig- ometer was mounted on the edge of the Each peak on the velocity mode graph nificantly as rpm is increased to stan- engine, and the second was mounted represents a vibration; the taller the dard cruise levels. If that is true, then the above the crankshaft near the front of peak, the greater the vibration magni- presence of a 2.43-per vibration on this the engine to measure propeller vibra- tude. The baseline reading was taken at engine is not a concern, but to confirm tion. A single accelerometer is all that an engine rpm of about 2500. Here, a this theory, a second vibration survey is necessary to dynamically balance 1.4 IPS peak is present at the 2-per-prop- was done at 5000 rpm. The results can a prop, but the second accelerometer rotation interval. A taller peak on the be seen in Figure 2. enables recording different kinds of graph, slightly more than 2 IPS, indi- As expected, the 2.43-per vibration vibrations: prop and torsional. The cates a vibration that occurs every 2.43 has almost disappeared at cruise rpm. photographs above show the stages times per prop rotation. For this reason, no remediation is rec- of setting up a Rotax 912 engine for ommended for this vibration. How- vibration analysis. Resolving the 2.43-Per Vibration ever, there is also a 2-per vibration that Once the engine was set up, a baseline This engine exhibited a severe vibration increases at cruise rpm. vibration analysis was completed. This at the 2.43-per interval, seen as the tallest involved running the engine up to cruise peak on Figure 1, just to the right of the Resolving the 2-Per Vibration rpm or the rpm range that exhibited 2-per vibration. This vibration is due to a The 2-per vibration of this particular the vibration symptoms, so the vibra- variation in the torque of the engine that engine measured at 1.4 IPS is significant, tion analyzer could collect data. In the occurs with every other cylinder firing, and it gets worse at higher rpm. Ideally, case of this aircraft, vibration data was i.e., a strong cylinder fires, then a weak an engine exhibits no vibration at all, but collected at various rpm levels. When cylinder, then a strong, then a weak, etc. a vibration of .2 IPS or less is considered data collection was complete, after just It is probably caused by the difference in acceptable. In the case of this engine, the a few seconds, the results revealed which intake lengths on the intake manifold of 1.4 IPS 2-per vibration, in combination vibrations existed. the Rotax 912 engine, with the front cyl- with the 2+ IPS vibration from the 2.43 Those vibrations are visible on the inder having a longer flow path than the velocity mode graph that the Dyna- back cylinder. This difference in front- Vibe system generates (see Figure 1). back airflow causes a torsional vibration Prop Balancing vs. The velocity mode graph displays the in the engine. Vibration Analysis While dynamic prop balancing is a specific type of vibration analysis, it is not the same thing as a vibration survey. A system that does dynamic prop balancing consid- ers just the 1-per vibration associated with prop rotation. Dynamic prop balancing is, therefore, a subset or application of vibra- Figure 1: Results from the initial vibration Figure 2: The 2.43-per vibration is almost tion analysis. A complete vibration survey analysis baseline runup reveal two signifi- gone at cruise rpm. must analyze the entire vibration spectra. cant vibrations. —M.D.

KITPLANES October 2016 37 This case study illustrates the value of vibration analysis in troubleshoot- ing vibrations whose source is some- thing other than the propeller assembly. Since the propeller accounts for vibra- tion problems in a majority of cases, the vibration remediation process should always begin with dynamically balanc- ing the prop. If that doesn’t resolve the vibration, the analysis will pinpoint the source: A half-per vibration indicates a combustion problem, a 1-per vibration is caused by prop assembly imbalance, and a 1.2-per vibration points to imbalanced carbs. Engine data provided by the man- ufacturer can help owners understand what these vibrations indicate, and the vendors of vibration analysis systems are also a great source of this information. With the information provided by The differing flow-path lengths of the intake manifold can cause a torsional vibration in vibration analysis, an owner or mechanic the engine. doesn’t have to go on a wild-goose chase per was so strong that it was shaking gas on their frequency. The prop on this to find and resolve vibration problems. out of the carburetor onto the exhaust aircraft was dynamically balanced prior The value of vibration analysis goes well manifold! In the mid-rpm range, the to the baseline vibration survey, and the beyond just locating vibration sources; it combined effect of the 2.43- and the data confirmed that the prop was not is an excellent preventative maintenance 2-per vibration was very destructive and the source of the vibration (a propeller approach. Performing regular vibra- potentially quite dangerous. assembly balance would have resulted tion surveys enables early identification The close proximity of these two in a 1-per vibration on the velocity mode of maintenance issues while they’re still peaks, one at 2-per (33 Hz) and one at chart). A 2-per vibration is related to relatively small, before the vibration does 2.43-per (40 Hz) causes a beat frequency, something that rotates with the prop, much damage, or most importantly, similar in sound to a twin-engine air- and since the Rotax 912 is a geared before it results in failure. J plane with the engines out of sync. engine, attention fell on the gearbox. Except in this case, the beat frequency The cause of this 2-per vibration was *Vibration Effects on Helicopter Reli- was around 7 Hz, making the airplane confirmed by measuring the friction ability and Maintenance, Angelo C. feel as if the engine was running at 430 torque of the gearbox, which registered Veca, April 1973. (http://www.dtic.mil/ rpm—a very low rumble, exactly what 66 foot-pounds, well over the manufac- dtic/tr/fulltext/u2/766307.pdf) the aircraft exhibited. turer’s maximum of 44 foot-pounds and Matthew Dock When the presence and frequency of considerably out of spec. This vibration Matthew Dock is a a vibration is known, its source is nar- data provided certainty about the source registered professional rowed to one or a short list of causes. of vibrations in the engine. The airplane mechanical engineer in How can one know what the various manufacturer was able to work directly Oklahoma. He is the co- vibrations point to as a cause? When with the engine manufacturer to iden- founder of RPX Technolo- diagnosing machinery faults using tify a permanent fix to the gearbox vibration analysis, there are known problem. No additional trial-and-error gies, a provider of dynamic industrial causes of vibrations based diagnosis was necessary. balancing and vibration analysis solutions for avia- tion and other industries. How to Get a Vibration Survey of Your Airplane Matt is a licensed private You don’t have to own a vibration analyzer to get a vibration survey on your airplane. Some pilot with over 1000 hours EAA chapters own dynamic prop balancers and vibration analyzers that are available for of time logged in Experi- chapter member use. If you don’t have access to a dynamic prop balancing and vibration mental aircraft. He owns analysis system, check with a service center or mechanic that provides dynamic prop balanc- a Long-EZ, Kitfox on ing services, as they are likely to own the equipment for conducting vibration surveys. floats, and a Cessna 172. —M.D.

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Instantly knowing airspeed to better than 2-knot accuracy makes quick work of calibrating airspeed indicators, establishing stall speeds, and extrapolating other performance standards.

Andrew Angellotti develops an air data probe for the masses. By Tom Wilson

Every time we get depressed Mojave guys. Free thinking, restless for thinking Experimental aviation is the shop, and with a millennial’s native going gray and cookie cutter, we hop in facility with electronics, Andrew has the box kite and head to Mojave where developed an air data probe that is accu- the atmosphere is hot with innovation rate to a knot and half, portable as cash, and enthusiasm for everything flyable. user friendly in the extreme, and, should That’s because Scaled Composites, the he put it in production, affordable associated Stratolaunch Systems, Virgin enough that regular Joe’s can aspire to it. Galactic, Orbital ATK, Masten Space True to its modern provenance, Systems, and the National Test Pilot Andrew’s air data probe is the marriage School are on the field, so there’s always of 3D printing and a custom circuit a squad of young Turks on patrol. And board. So far he’s developed two versions. the young dudes always have something The first is a five-hole design yielding -air new in their backpacks. speed, altitude, angle of attack, and angle Andrew Angellotti holds his air data probe traveling kit on the Mojave ramp. So, we had barely unwrapped our of sideslip. Realizing not everyone needs Everything from the probe to mount- scarf when we were introduced to that much information and might just ing tape is here, ready to attach to any Andrew Angellotti, one of the newer want to calibrate the airspeed indicator conceivable airfoil.

40 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes One Trick Stick

Aluminum tape is the foundation behind the air probe’s mounting—beware flaky paint! Easily generated in a 3D printer, the mount- Two-sided tape under the pair of adjustable bracket mounts allows quick eyeball level- ing brackets are two-piece units: the main ing of the “stick” and more aluminum tape secures the mounts to the foundation tape. stand and a pinch block between the forks. Andrew gives each installation a 20G pull test with his digital fish scale and reports testing Stepping the stand’s base gives it flexibility to 245 knots with stick raps didn’t budge the installation on a Lancair. to easily conform to airfoil shapes.

in their new RV-8, Andrew developed a handy for an extended group of builders to a laptop-mounted receiver dongle. simplified 1-hole version that’s easier and and technicians. He also chose a robust 2.4-GHz mesh less expensive to build. Several concepts and technologies routing radio interface in lieu of finicky In either five- or one-hole version, enable this new data probe. If nothing WiFi or Bluetooth protocols. Andrew’s air data probe opens new doors else, inexpensive 3D printing sidesteps Andrew first sketched the probe’s to builders looking for fast, accurate air- machining or casting to lower costs. circuit board layout in an Oshkosh speed information. The probe replaces Whittling all this out of aluminum coffee shop last summer. “I had the tedious, narrowly focused flight tests would definitely be dear. time off work so I thought I would do with near instant information. And while Andrew also specifically avoided something useful,” he explained. And a typical builder may need the probe only wires—there isn’t a single wire in the to think we were simultaneously fully briefly during initial phase flight testing, entire system—making the probe engaged by pitching a tent. By August the probe mounts to almost any wing so a cinch to install or move from one the circuit board was printed, and the quickly that it’s easy to envision an EAA plane to the next because it radios device made its first flight last Septem- chapter or a local specialist keeping one data from a circuit board on the probe ber on a Piper Cub.

The five-hole probe (front) bundles five tubes with a carefully Andrew designed his circuit board to hold the battery, a power beveled leading edge; the 1-hole unit (rear) uses a simple single supply to regulate voltage, a 2.4-GHz transmitter, accelerometer, tube. Andrew has found hole diameter consistency is not critical local memory, a USB port (just because…), and one absolute and as variations are accounted for in his calibration of the assembly, three differential pressure transducers. Each board and probes but keeping the five-hole’s bevel symmetrical does matter. are calibrated by Andrew and are thus matched sets.

Photos: Tom Wilson KITPLANES October 2016 41 Open as a convenience store, Andrew’s air probe doesn’t bother The only other hardware is this USB dongle that attaches to the with a cover for the electronics or even an on-off switch. Press user’s laptop. There are no wires, and the receiving laptop can be the battery in place and it’s running; a zip tie provides security. as much as 500 feet from the probe. That makes testing cramped The clear tubes carrying air pressure to the transducers are easily single-seat aircraft easier as the pilot need only “fly the card” while seen here. the data technician could be in a second aircraft flying nearby. At first he was discouraged because “the numbers were bouncing around.” Coaching from test pilot Elliot Seguin soon had Andrew seeing the benefit of flying controlled, concentrated test flights to isolate issues, and then the data quickly started coming together as the few developmental issues were solved. More help came from Dustin Mosher who brought much-needed piloting skills to the project. “Now all calibration flights are done to cards,” says Andrew, who still needs to ini- tially calibrate each probe and its circuit Experience has taught Andrew that tiny Once a data file is logged in Andrew’s board as part of manufacturing. type fonts and information overload are software, it will open directly in Excel or So, what can an air data probe do for undesirable in flight, so this simple window other common PC spreadsheet programs. is all his proprietary software displays From left the columns are date, time, you? Pitot/static calibration is the first during data acquisition. It works well in KIAS, altitude MSL, Vraw, and Araw. builder’s conundrum this thing can direct sunlight and turbulence. solve. No more four-heading GPS cali- bration flights or tower fly-bys. For any- one routinely making first flights, this stick would save a ton of time. Level acceleration is also obtained with off-handed ease by the probe. From such data, best climb, best glide, and other numbers can be derived with a little math. This can be done on any airplane in 15 minutes of testing says Andrew, so if you didn’t have any data Of course, once in a spreadsheet any sort of graph can be generated. This simple airspeed collection, this is a big step forward. vs. angle of attack (Alpha in test pilot speak) graph was generated from data taken by a one-hole probe. Given the five-hole probe, a stall series with different deceleration rates probe itself. Andrew originally built boating units is the right ballpark for can capture the maximum G (there is the probe for his and his friend’s per- the five-hole probe. Given the growing an accelerometer on the probe), altitude sonal test piloting, but the interest the sophistication of amateur building, lost, and other useful data. probe has generated has him consider- plus the current push to increase E/A-B Unfortunately the bit we can’t report ing production. Pricing is thus in the safety, Andrew’s trick stick seems an on is if, when, or how much for the future, but we’d venture two standard idea whose time has come. J

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For fastest service, visit us at www.kitplanes.com/subscribe or call us toll free at 800/622-1065 Stressing Structure Places to Save Weight and Places Not To By David Paule

Dave Dooley flies his Xenos motorglider near the Colorado foothills. The minimal paint saves weight and is a good accent to the polished aluminum. (Photo: Nancy Clair)

I started writing this, thinking this the fittings don’t have a lot of areas Measuring Weight is going to be pretty simple. This is that don’t contribute to distributing I use grams. Each pound has 453.6 KITPLANES® magazine, and if it’s a the load. of them, and most common kitchen kit aircraft, well, don’t save weight on But if you’re the builder—and this is scales can read in either pounds and structure if the designer doesn’t tell you important, only if the designer agrees— ounces or grams. Set it to grams. I feel to. Of course, that still leaves a lot of don’t neglect buckling because buckling that, depending on the effort, it’s prob- options available to write about. is such an important part of airplane ably not worth spending much time If you’re the designer, for structural design. Remember, in some places, stiff- on something that’s under three grams parts, don’t try to save a lot of weight ness is very important and the parts for the whole plane unless it’s easy and in the fittings. They’ve got to trans- might be designed for that rather than inexpensive. Anything more than that fer some load, and they last longer if strength. If you’re the designer, make and I’ll probably at least consider it. they’re robust. The place to save weight sure that there’s still a positive margin Ten grams and I’ll take it seriously. One is in the continuous members, things of safety for all the load cases with the hundred grams and it’s definitely worth like spars or tail cones. The fittings lighter design. going after. It’s the cumulative effect on don’t have to be crude, though; keep in With that out of the way, here are the whole airplane that counts, not how mind the load paths and design so that some suggestions. much a single one weighs.

44 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes Webs Stressing Structure Sometimes a part is built like a spar, with caps and a web. Or it might even be a spar. Perhaps it’s some sort of rib or bulk- head or something. Generally speaking, the center third of the part pretty much can only carry axial or shear forces, and lightening holes might be appropriate. I say might, rather than saying to go ahead with them, because they might not. Often the kit plans will tell you where you can drill them out but sometimes they won’t. With these, it’s important to have an idea of the loads because holes make a web less resistant to buckling. You know the rule: ask first. If it’s your design, do the shear analysis and see. Replacing the larger AN365 nuts with smaller MS21042 nuts can save a pound or more. If there’s a stiffened bead around a center flat disk, the interior, that disk, Nuts Corners can almost always be drilled out—the The MS21042 all-metal locking nut Sometimes we need square corners, espe- bead itself provides the needed buck- supersedes AN363, AN364, AN365, cially on the external parts of the air- ling resistance. Even so, if it’s not in the MS20364, MS20365, MS21040, some plane like skins. But we usually don’t on plans, check. NAS679, and a few other less common the interior corners. Rounding the cor- nuts. How do we know that the MS21042 ners while maintaining appropriate edge Bolts and Screws nuts supersede the older AN nuts? The distance will save you a little weight. Mixing bolts or screws in a fastener pat- MS21042 specification says so. The older Probably not a lot, probably under a half tern along with driven rivets is a no-no AN365 fiber or nylon locknuts are very pound, depending on your airplane, but if the fasteners are in shear. What hap- common in general aviation, and the that’s certainly worth going after, and it’s pens is that the driven rivets fill the hole MS21042 nuts are lighter. It’s always a good habit to get into. and will start to fail before the bolt or worth checking the specification if you’re using hardware that’s new to you. Better yet, they’re smaller, and in some cases that’ll let you use a shorter bolt for additional weight savings. It’s a few grams here and there that really add up. I bought enough of the MS21042 to replace all the AN365 nuts on my RV-3B, and even though this is a small airplane, it’ll save me about one pound right there. Washers The washers we generally use come in two main thicknesses. If you can use the thinner one, that’ll save you a little weight. If it’ll let you get by with a shorter bolt or screw, especially using those lightweight nuts, even better. On my RV-3B, I try every bolted joint to see how light I can get it and still maintain the appropriate bolt grip. Remember The rib-to-spar joint uses both bolts and rivets, acceptable here. The nuts are the light- that the bolt grip length is often at least weight MS21042. On the bottom row of screws, I’ve already changed the ½-inch long screws as important as the threads and might that the plans call for to 3/8-inch long screws. On the top, I’ll do that after I move the wing prevent using a lighter bolt. and that side becomes accessible. Note that I’m using lacing instead of zip ties on the wire.

Photos: David Paule KITPLANES October 2016 45 screw gets properly loaded up. Then the hinge pin end, not two, and there don’t There might be canopy options that bolts or screws are left carrying the load need to be any rivets. You’d only save you are considering. Thinner is lighter. with the rivets having failed or partly four grams, but it’s a good example of It’s also more frangible if you need to failed. But this isn’t always the case: how to save weight in some details. break it apart to get out of the airplane. On my RV-3B, there are some wing Actually, you don’t need any hinge You’ll have to decide if that’s balanced by rib to spar joints where the shear load pieces or screws—drill two small holes lower resistance to a bird strike or some- is carried by the driven rivets and the in the sheet metal that’s in front of thing else. moment load from the flap is carried the assembly, and tie some safety wire into the spar by loading bolts in ten- through them around the two pins. Composite Parts sion. For that sort of situation, it works. There’s access through the lightening There are lots of nonstructural and semi- It works because the bolts are torqued holes to loop the wire back through the structural parts made of fiberglass on and that causes a preload, which acts in second small hole. That’ll probably let most of our airplanes, and we often get tension as effectively as a driven rivet you save up to six or eight grams. You’ll to make some more. Generally speaking, does in shear. eliminate the hidden nutplate, too. if you use carbon fiber instead of glass So if you see such a joint, be sure you The moral here is to ask yourself if a for the layup, you’ll increase the stiffness understand how it works. It’s probably not particular part is needed and how else and save about 20% of the weight, maybe a great place to try to save some weight. that function can be acquired. I like to more. But of course if you’re making a have at least three alternatives, all with composite airplane, don’t go indiscrimi- Small Details different concepts, before choosing any nately replacing glass with carbon in Pesky little details that are left to the of them. structural parts. You can only do this for builder can be good places to save weight. Speaking of small details, do you need things like fairings, wheel pants and so A friend made the nifty hinge pin retain- conduit or can plastic bushings suffice? on. Don’t modify the primary structure ing fitting shown in the photo below. The bushings are a bit more awkward, unless you’re the designer and know the While it doesn’t weigh much all by itself, but definitely lighter. engineering characteristics of the partic- it provides a handy example of places Are you using zip-ties or lacing? The lac- ular materials you’re working with. where you can save a little weight. They ing is slightly lighter and won’t snag your Even so, carbon has a much lower coef- add up. Here’s the weight-savings aspect hand later. The good old EA-AC 43.13-1A ficient of thermal expansion than fiber- of it: You only need one hinge loop per & 2A shows how to tie the knots. glass, so you need to account for that. It also reacts with adjacent metals, causing them to corrode, so that, too, needs your attention. That weight savings does add up, though. If you learn how to vacuum bag your composite parts, you’ll save some weight and get a better layup, too. Glue Perhaps it’s small potatoes, but with glue squeeze-out along edges of bonded parts, it’s generally much better struc- turally to make a smooth but small fil- let than keep a round bead. The fillet is usually lighter, too. This might come under the category of good workman- ship instead of weight savings, but as it does save weight, I’ll take it. Fabric If your airplane has fabric, you can check the various fabric vendors to see what the lightest fabric is for the type of airplane you’re building. The fabric might depend on the gross weight, the wing loading, the speed or something else. Perhaps a This neat little fitting doesn’t need to be there at all. (Photo: Larry Larson) new fabric like Oratex might be suitable

46 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes and lighter than the standard fabric. You safety aspects of them if you’re going to Approximate might need to call the vendor to get a use them. And bear in mind the effect good idea of how much a particular sys- that change will have on your center of Weight of Paint: tem weighs if their website doesn’t sup- gravity. Nonetheless, you might be able S = 156 ft2 Wing area ply it. Be sure to assess the weight of the to save more than 10 pounds there. m = 4.0 Multiplier between coating system as well as the fabric itself. 3 and 5 Paint d = .05 lbs/in3 Density of paint Ah, paint. There are so many different Electronics t = .006 in Thickness of the paint Some of the electronics we add are essen- paints that you can use! I don’t know Wt = S * m * d * t Total paint weight tially modular in nature, interconnected much about paint, and I’ve never painted with wire bundles. The best way to save an airplane. All I can suggest is that it’s Here we convert square feet to square inches: weight is not to install anything more possible to make the paint job either in2 Wt = 156 ft2 * 144 * 4 * .05 lbs/in3 * .006 in than the minimum that you need for lighter or heavier. I’ve seen paint weight ft2 the operations you intend to fly. Do you estimates vary from five pounds to 30 Wt = 27 lbs Total paint weight really need an autopilot? Or a second or pounds for a typical homebuilt. Some —D.P. third EFIS screen? If you can eliminate paint is discretionary. If you have an alu- an entire subsystem, you also remove the minum airplane and you polish it, that’ll “lightweight” starters are grossly mis- power and ground connections and the save some serious weight. named. Likewise, don’t install a larger circuit breaker and fuse. Maybe you’ll A lot of people use filler under their alternator than you need. get lucky and leave off a switch, too. paint jobs. That should be used sparingly Other things like oil filter mounts Sometimes you can locate some of if at all, and only the lightweight fillers come in a variety of forms and some of the modules quite close to each other at that. them even need hoses. Others don’t. and that reduces the length of the wire These days, wraps are becoming popu- Prop governors also vary in weight. bundle. Or if you read the installation lar. How does their weight compare? If you can avoid a constant-speed prop, manuals, you might find that a com- Since composite parts almost always you might save some serious weight petitor has more integration and fewer need some paint; you can polish the there, since that also eliminates the gov- pieces—count the cables. Occasionally metal and paint those parts like Dave ernor and its control, as well as a lot of we might have a choice between a panel- Dooley did on his pretty Xenos motor- prop weight. For Lycomings, that might mounted device and a similar device that glider on page 44. get rid of an external oil line, too. has a panel-mounted control head and a An airplane has a total surface area Some of the aftermarket suppliers remote box; remember that the version that’s something like three to five times offer some very lightweight equipment, that’s entirely mounted in the panel not the wing area. Since polymers weigh often things like sumps or intake mani- only doesn’t have that wire bundle, it something like .05 pounds per cubic folds. They might be worth considering. doesn’t have the connectors. But there’s inch, you can quickly make a very rough Some airplanes are sensitive to engine a trade-off you’ll need to assess between estimate of the weight of paint if you can installation weight for center of gravity that and the possibly longer antenna get an idea of how thick the total coating reasons. If you’re planning to save lots of cable, if there is one. buildup will be. For example, if there’s weight up front or wherever your engine On smaller details, if you can run a 600 square feet and the cured coating is, keep this in mind and plan to move continuous wire instead of using a con- thickness is .005 inches, the paint adds other equipment around to adjust the nector, you might be better off. It may roughly 21 or 22 pounds. Didn’t think center of gravity position if needed. J save some weight, even if you allow some I’d let you get this far without some Davi extra wire for a future connector to be math, did you? David Paule retired after 30 installed, and you’ll remove a possible Here’s a useful factoid: A “mil” is a years of structural analysis joint that can be intermittent. The time measure of thickness. One mil equals and is now building an alone that you could save would justify .001 inches. Some coating companies RV-3B to keep from getting

it, and in the future, if you need to, you use that in their manuals. d bored. The structural can usually still insert a connection. This engineering included a mix idea is for places where the pieces of air- Firewall Forward Paule of aircraft and spacecraft. He plane aren’t usually removed. An exam- This area offers some interesting options has been a private pilot since ple might be the wing-to-fuselage joint. for major weight savings. I’ve heard age 18 and Another might be the control stick. that the narrow-deck Lycomings might currently These days, there are some lighter be around 20 pounds lighter than the owns and batteries available that were prob- later models, for example, and acces- flies a Cessna 180. ably unavailable when the plane was sories like starters can vary from under designed. Be sure you understand the seven pounds to over 13, and some of the

KITPLANES October 2016 47 CHECKPOINTS The big picture and red herrings. I’ve often heard the phrase, “Don’t most critical being the nuts on the Lord has not recurred, so the autopilot itself miss the big picture.” Sometimes it’s engine mounts. That’s right—no cotter was not the culprit. even referred to as “target fixation,” and keys and the nuts came off in my hands! there are documented cases of pilots on The spiking on the EGTs and CHTs was Rudder Trim Problems bombing or strafing runs seemingly get- due to the sensor wiring bundled with Next, I installed an internal rudder trim ting so fixated on the target that they the spark plug wires, along with some system from M.L. Skunk Works, as per the fly right into it, with disastrous conse- intermittent connections due to poor owner’s request. Once I was finished with quences. I thought I would share some crimps. This was not the first or last time I the rest of the inspection, I buttoned up personal cases of big picture experiences have seen wires routed that way, causing the aircraft and took it for a test flight. I have had with a few airplanes, and one the same problems. To say the aircraft required right trim with a car. Another issue involved the autopi- in cruise for coordinated flight was the The first involved the second owner lot lurching intermittently while in alti- most dramatic understatement I think (non-builder) of a rather new RV-10. The tude hold mode. This turned out to be I have ever heard. My right leg actually aircraft had about 80 hours on it, and the an improperly installed static system, cramped after about 20 minutes of flight. owner contacted me and asked for some which was allowing water into the static I had adjusted the rudder trim so far to help solving a few nagging problems. plumbing. Rerouting the static system to the right that I thought the trim cable The worst was an annoying noise in the prevent water ingestion, as well as install- was going to snap, and eventually it did! I electrical system that could be heard ing a cockpit-controlled alternate static also noticed that the trim forces subsided in the intercom, and constantly spiking source (required for IFR), should ensure at lower airspeeds, but I needed to land EGTs and CHTs. He also casually men- no more problems in this area. Yes, there and figure this one out. tioned that he would like me to install was a substantial amount of water in the On most Amateur-Built aircraft there a rudder trim mechanism, as it needed system that I blew out, and the problem are many builder areas that require right rudder pressure in flight in order to maintain coordinated flight. As he taxied up to my hangar, I noticed that the wheels were tracking in an unusual manner, almost wobbling in fact. After he shut down, a more careful inspection showed that the axle nuts were missing the cotter keys, allowing the axle nut to back off to the point that the only thing keeping the wheels on the bearings were the brake calipers! Yikes. Luckily, that was an easy fix, but it gave me some pause about the rest of the build quality. Sure enough, a much more thorough inspection of the aircraft revealed miss- Bundling the CHT and EGT wiring with the spark plug wires can cause fluctuating readings ing cotter keys in a few other places, the on the temps. It is better to route them from behind and away from the plug wires.

Vic is a Commercial Pilot and CFII with ASMEL/ASES ratings, an A&P, DAR, and EAA Technical Advisor and Flight Counselor. Passionately involved in aviation for over 39 years, he has built 10 award-winning aircraft and has logged over 8000 hours in 70 different kinds of aircraft. Vic Vic Syracuse had a career in technology as a senior-level executive and volunteers as a Young Eagle pilot and Angel Flight pilot. He also has his own sport aviation business called Base Leg Aviation.

48 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes attention to detail in order to have a properly trimmed aircraft. Specifically on the RVs, misalignment of the gear leg fairings and wheelpants can have a real adverse impact on drag and yaw. Set- ting them correctly requires jacking the aircraft so that all of the weight is off of the wheels and the gear legs are in the “flight” position. During the build- ing process I usually accomplish this task prior to installing the wings, as it is much easier to jack the lighter fuselage than a completely built aircraft. And I am always nervous around aircraft that are sitting completely on jacks. All it takes is one thoughtless moment of walking to get a tool and bumping into a wingtip to cause some serious damage. So, I set about leveling the RV-10 on jacks and did discover that the left and right leg fairings were slightly out of trail. Great. I ...and leave your engine adjusted them, fixed the broken rudder monitoring to EIS. trim cable and felt confident the problem Trusted with everything from 2-strokes was solved. to turbines for over two decades. So much for that line of thinking. I wasn’t even close! On the next flight the rudder trim forces were just as high, and the airplane actually flew so crooked that FLY IT my son who is not even a pilot, but lives like you stole it... on the end of the runway and witnesses a lot of takeoffs, mentioned that it was the most crooked-flying airplane he had ever www.grtavionics.com • (616) 245-7700 seen! By the way, when I engaged the Proud sponsor of Tiger Airshows and airplane “thief” extraordinaire, Hotwire Harry! autopilot, it would track a heading with one wing substantially lower than the other, verifying it was not an AHRS align- ment problem. And my own view out the window, along with the feel of my seat, told me it was still substantially yawed. So, back on the ground I thoroughly inspected every other thing I could think of, carefully measuring the vertical fin offset, along with horizontal and vertical stabilizer alignment. I even went to the detail of dropping plumb bobs to verify the wings and tail feathers were properly aligned to each other and the fuselage. I didn’t find any smoking gun, and seeing as the RV-10 is pre-punched in these criti- cal alignment areas, I really didn’t expect to find anything. I even checked the engine mount for alignment, using my own RV-10 as a guide. Still nothing. It was only after I backed away from the airplane a good 30 feet to look at the

Photos: Vic Syracuse KITPLANES October 2016 49 was on his way. Let’s call this Red Herring #1. Once here, it wouldn’t start again, and upon inquiry, he stated the alternator showed 13.6 volts for the entire 2-hour flight. Hmm. So, the alternator is work- ing, but we all know the Odyssey brand of batteries likes a higher charging volt- age, something like 14.3 volts, and if not charged at that voltage, they will die an early death. Clearly the regulator needed adjusting. Let’s call this Red Herring #2. I checked the battery with a battery load tester, and surprisingly it tested really well, twice in fact, and showed an open circuit voltage of 12.8, which is just right for an Odyssey battery. Hmm. I then This fairing was installed crooked and protruded about 3/8-inch off to one side, which put a voltmeter on the battery and at the caused it to act as a fixed trim tab (left). The resultant forces were almost impossible to starter while I engaged the starter. The trim off, and the airplane flew quite crooked. A new fairing fixed the problem (right). starter did not engage, but there was a big picture, that I saw something amiss. Red Herrings substantial voltage drop. Must be the The fairing at the top of the vertical fin The most recent big-picture fiasco aircraft wiring or the starter solenoid, so was installed somewhat crooked, and occurred on another RV-10 as well. The I checked both of them and couldn’t find protruded about 3/8-inch out on the left customer was coming to see me for any reason for the voltage drop. Bypass- side of the aircraft. Hmm? Could that be some upgrades and called to inform me ing the starter cable from the solenoid acting as a fixed trim tab on the vertical the aircraft wouldn’t start. Luckily, we to the starter showed the same voltage fin? The more I looked at it, the more I were able to use FaceTime, and I had him drop, but I also noticed the cables got convinced myself that it was the prob- show me the volts reading while engag- hot, as did the starter. So, off came the lem. I had a quick discussion with Paul ing the starter. The reading dropped off starter to be bench tested. Of course, Dye, our editor in chief, and he agreed. enough that it looked like a weak battery, it bench tested fine with a battery and The problem now was convincing the even though the aircraft was only about cables on the bench. But after 25 or so owner I needed to cut off the fairing and eight months old, with 90 hours on it and attempts, it finally failed. I found a poor install a new one, which could mess up an Odyssey PC925 battery. He charged crimp on the jumper wire at the starter, his really nice paint job, as the fairing was it, and it started, but then wouldn’t fixed it, and could not make it fail again, blended into the paint and not remov- start again after taxiing over to the fuel so I reinstalled it on the aircraft. Red Her- able. As I thought, he was not real open pumps. Well, we all know such a short ring #3! After the fifth start, it actually to cutting it off. However, I was not com- taxi probably wouldn’t charge a weak/ failed again, so I removed it and, sure fortable with this airplane continuing to dead battery enough for a start, so let’s enough, I could make it fail on the bench fly with that much constant force on the charge it again. Yep, that worked and he only after many attempts. The solenoid vertical fin, and I politely stated I would not sign off the condition inspection without fixing the problem. After all, it is supposed to be in a condition for safe operation, right? So, I did order a new fairing from Van’s and very carefully removed the original fairing, trying to disturb as lit- tle of the paint as possible. I made the new fairing removable with nutplates, so when completed it looked original, and the vertical fin required no paint except for the new fairing. On the sub- I find a battery tester that puts a load on What good is a voltmeter without range sequent flight I was rewarded with a the battery to be an invaluable tool for markings? When the alternator failed, the troubleshooting electrical problems. Here owner wasn’t sure as to what it normally wonderfully flying RV-10, along with a is a reading after a 12-second load on the read, and the failed alternator put the car rudder trim system that works as well. battery, clearly indicating that the battery in “limp-home” mode, which acted like a Lesson learned! was not the source of the starter problems. failed transmission.

50 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes on the starter was intermittently hang- ing up. Discussions with “TJ” Jenkins at A Better B&C Specialty Products confirmed the diagnosis, and they fixed it the same day Mousetrap under warranty. Of course, I did adjust the regulator to improve the life of the SHOP B&C battery, but I didn’t expect such an Rivet Holder early failure of the B&C starter, as they TIPS By Eric Stewart are so reliable.

Car Trouble Rivet holders seem to be like mousetraps—someone’s always got an idea for The last big picture experience actually a better one. Well, I guess I’ll contribute to the genre. happened with my daughter-in-law’s car. I’ve always liked the concept of the DIY organizer made by nailing baby food My son was out of town, so she called me jar lids to the underside of a shelf, and then screwing the jar in as your holder. It’s to say her car wouldn’t shift out of low a great space saver (how else are you going to use the underside of a shelf?), and gear after she stopped at the mailbox on the glass jar lets you see what’s inside. On the downside, they’re a bit fiddly to the way home. Must be the transmission, screw in and out, and let’s face it, if your shop has a concrete floor, a glass jar is a right? I got in the car, and after starting disaster waiting to happen. the engine I looked at the instrument So here’s a variation on the theme. This rivet (or whatever) holder uses 8-ounce panel for what few gauges are there polyethylene jars that you can buy in bulk from companies like Uline or Grainger. anymore, and the voltmeter didn’t look The jars mount lid out, so you can label the lid with the contents. Change con- right. No range marks, of course, but it tents? Just rub clean with alcohol and re-label. Being plastic, no worries if you was reading about 12 volts as best I could drop one. Use a slightly undersize hole saw and the jars will stay securely in place. tell, and I know most new cars run about I wrapped some adhesive sandpaper around the hole saw to get just the right 14.5 volts. I was guessing she thought I diameter and a smooth hole. J didn’t know the difference between the transmission and the alternator when I asked her if the volts always read that low! Unfortunately, she couldn’t remem- ber what it normally read. A quick drive up the street confirmed the transmission wouldn’t shift, but I couldn’t get past the voltmeter reading. I checked the battery, and it was quite low, and there wasn’t any change with the engine running. I was convinced the alternator was bad, so I charged the battery. Lo and behold, the Mark a 2-inch thick piece of blue foam with a grid pattern for your bottle spacing and transmission shifted with a fully charged drill pilot holes at the intersections (left). Use a hole cutter to cut the foam. I used a battery. A quick call to the auto shop con- drill press for the perimeter holes, but had to use a hand drill for the interior holes. The band of white around the hole cutter is adhesive-backed sandpaper (right). firmed a bad alternator would put the car into “limp-home” mode, not allow- ing the transmission to shift. This time, paying attention to the big picture really worked, and sooner rather than later! By the way, this limp-home mode is not something I would want in an aircraft with an auto conversion! Something to think about for those of you experiment- ing with auto conversions. I am aware of at least one RV-10 with an auto conversion that had a hard landing due to a tempera- ture parameter exceeding the limits in the Use epoxy or a foam-friendly contact adhesive to mount the foam to a baseboard. Extend the baseboard a couple of inches beyond the foam for mounting, or you can ECU, causing a reduction in power. also screw in through a hole to ensure lining up with a wall stud (left). The finished I bet some of you have some similar rivet holder mounted to the wall. Not bad! About $30 for the jars and foam, and an stories. J hour of time to build (right).

KITPLANES October 2016 51 ENGINE THEORY

Direct vs Geared Drive

One of aviation’s great debates. By Tom Wilson

Great debates are born when both unit. Either way the mechanicals are Now there’s a gearbox. Imposingly large, sides of an argument have at least one fairly pre-determined. the planetary reduction on the front of this gear leg to stand on, such as if a 180- That said, there is much to know R-2800 is the result of painstaking develop- ment by Pratt & Whitney. Input from vibra- mph homebuilt should use a fixed-pitch regarding slowing the propeller down, tion specialist Den Hartog of Harvard (and or constant-speed propeller. And right much of which may directly involve later MIT) plus endless rounds of crankshaft there with that classic is propeller speed your corpus or wallet’s well-being in failures in the dyno cell eventually resulted reduction—it has drawn as many of the rather dramatic fashion. The stakes in a reliable engine-gearbox-propeller self-anointed into computer-aided han rarely get higher, or the technical dev combination at well over 2000 hp. Don’t - - forget the metal propellers weigh hundreds gar flying sessions as anything. ils seemingly more elusive than dealing of pounds, and the whole lot was reliable Ironically, as amateur builders gear with anything other than the most pro- through combat aerobatics. reduction is not much of a practical con- fessionally developed PSRUs. cern. You either fit a big Continental or efficiency with reduced rpm, as the Lycoming without a gearbox or you’re To Slow Or Not To Slow learned Mr. Wainfan has recently set on a smaller Rotax, auto engine con- The whole point of a PSRU is to slow the detailed in his Wind Tunnel column version, or compact ultralight engine propeller relative to the engine. This is [KITPLANES®, June 2016]. Piston that does use a propeller speed reduction because propellers gain aerodynamic engines, on the other hand, gain

52 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes gear down the propeller, and even then many such props are still on the fast, noisy end of things. Likewise, automotive engines are bred to loaf at surprisingly low power at low or medium rpm and make rare bursts of meaningful power at high rpm. When converting them to constant high out- put, there’s typically no choice but to turn up the rpm to make power and fit a gearbox to reduce propeller rpm to more efficient levels. You may have noticed Continental and Lycoming aviation engines are some- where in between our example engines in size and rpm. That’s no accident; the 2500- to 2700-rpm direct-drive aviation engine turn is a compromise fast enough Small-displacement engines naturally run at relatively high rpm to make power and to make some power and slow enough for therefore require propeller speed reduction gearing. Luckily, the modest power involved efficient propeller diameters. can be handled by simple belt-drive reduction units. A wide, ribbed belt and good belt wrap around the pulleys mean no belt tensioner is used. It’s certainly not because the engines don’t appreciate being turned faster. horsepower and sometimes efficiency propeller diameters posed real issues for Nearly all traditional general aviation with a bit of rpm. This is especially true designers when it came to landing gear; engines are tuned to run at their torque if the engine’s displacement, overall size, witness the inverted gull-winged Cor- peak (point of best fuel economy) during and weight are being kept in check as sair or towering Constellation airliner. cruise, which is only a couple hundred they are in aircraft, as compared to a loco- Similarly, ultralight powertrains use rpm less than their maximum power rat- motive or ship engine, let’s say. tiny engines dependent on high rpm ing at takeoff. From a tuning perspective, In short, within limits, a fast engine to make power. The only way to get reaching their native maximum horse- and a slow prop makes everyone happy. workable thrust from such engines is to power output would require an extra Of course, turning the propeller more slowly than the engine requires some sort of mechanical ratio between Isolating Bad Vibes the two. This is either a gearbox or Multiple methods have been employed in the tough fight of isolating a piston engine’s belt drive, both of which introduce throbbing crankshaft from the reduction unit and propeller. Pendulum weights on the increased cost, weight and, above all, crankshaft are one method, along with (occasionally) centrifugal or other one-way clutches. complexity and a surprisingly large Commonly suggested shortcuts are fluid couplings such as a torque converter (too inef- number of not immediately apparent ficient and heat-soaked at continuous high power inputs), electric damping via out-of-phase but significant mechanical consider- motor/generator inputs (requires far too much energy), crankshaft harmonic dampers ations. Bluntly put, PSRUs are trouble (helps the crankshaft but not so much the prop), and so on. and need be designed and developed Like everything else with PSRUs, the effectiveness of these efforts hinges on how well with care by people who know what the engine/PSRU/propeller combination is vibration tested—not a job for amateurs. they’re doing and have the resources to Without the sophisticated (read: critically expensive) test gear to identify what vibration fully vet their creations. is present—along with testing every permutation of engine/PSRU/propeller combination Naturally, prop speed reduction is a manufacturer offers—it’s just shooting in the dark to specify what counterweights or sometimes a necessity, trouble or not. dampers to fit. It’s also not understanding the scale of the vibration issue in high-con- Back when Pratt & Whitney, Allison, tinuous-output propulsion systems to suggest adapting what are light-duty automotive and the rest of them were making 2000 automatic-transmission parts. hp with pistons, there was no question Of course, in this age of seemingly exponential improvement in the industrial arts, devel- such engines would incorporate a gear- oping a safe, reliable PSRU is not black magic. Heck, smart guys with slide rules figured this box. Trying to harness that much horse- stuff out before WW-II. It’s just that the engineering firms in the power transmission field see power to the atmosphere demanded poor return on investment in developing a PSRU for the diminutive piston-aviation market. huge props, which absolutely had to Exceptions will come with some of the clean-sheet, piston-engine designs finding their way turn slowly to avoid excessive tip speed. onto military UAVs, then trickling down to civilian use. Even with geared engines the still large —T.W.

Photos: Tom Wilson KITPLANES October 2016 53 1000 rpm or more. Furthermore, there are no piston speed or other mechanical reasons most of these engines couldn’t safely turn another 1000 rpm. But in direct-drive guise they don’t, only because propeller efficiency and (espe- cially from a safety standpoint) propeller mechanical integrity don’t allow it. In fact, when Continental and Lycoming did add gear reduction units to a few of their engines in the 1950s and ’60s, the engines needed no major changes to turn significantly higher rpm. For example, the GO-480 Lycomings found in light twins turn 3600 rpm at takeoff while the props are Most powered parachute, ultralight, and other micro-aviation engines use belt drive at just 2300 rpm. At typical cruise set- reduction, but as such engines grow in size, cylinders, and power, they can sprout geared tings the engines might turn 2500 rpm drives. The Hirth 80-hp 3002 and 100-hp 3003 4-cylinder, 2-stroke opposed family seen here is a good example. and the props just 1600 rpm, thanks to a 0.642:1 gear reduction ratio. extrapolate a hypothetical non-geared tricks. The supercharged GSO-480s are That extra engine rpm really helps “O-480” would have made just 225 rated at a healthy 340 hp, for example. make power, too. The GO-480 in a hp. That’s 60 missing horsepower, a 30 Let’s not forget the power these geared Twin Bonanza is rated at 285 hp. Con- percent loss, due to the rpm limitation! engines generate is more efficiently turned sidering a GO-480 uses six cylinders Furthermore, the higher-rpm engine is into thrust by slower-turning props. from the 4-cylinder O-320, we can easily receptive to the usual power-building PSRUs may be trouble, but they perform. “Just Don’t Do It!” Designing and developing a gearbox for hero-class performance cages—and a two-hour lifespan. Three times the gearbox failed before requires hero-class engineering. For proof, just ask Andy Chiavetta, Reno and then again at Reno. Each time the engine case had to be split fabricator and crew chief to the gods at Reno and elsewhere in perfor- to access the carnage… mance Experimental aviation. Harmonics were the culprit. Vibrations would crack the planetary cage, Teamed with racing great Darryl Greenamyer on “Race 33,” a storied allowing the gears to cock sideways with predictable mayhem. Eventually Lancair Legacy, Chiavetta was handed a lifetime’s worth of sleepless the engine case and gearbox were re-machined to allow separate access, nights and trashed machinery attempting to build a superior gear- but the gearbox never lived more than two flight hours. driven Reno mousetrap. Tiring of that, Greenamyer and Chiavetta next opted for a Continental Two designs were attempted. The first was a custom planetary unit GIO-520 with its integral spur gear drive. “But it’s designed for a specific welded right to the front of the TSIO-550 Continental’s case. It was prop and weight. We put an MT prop on it…so you’re experimenting a sexy looking thing full of macho gears and their stout supporting again. It would tear the accessories up in the back of the engine. It was just one trouble after another,” Chiavetta said. After years of gearbox issues, the team had nothing to show for it. Greenamyer retired from racing—with seven Unlimited class wins let’s not forget—and Race 33 is poised to return with a new owner and conventional direct-drive Continental this year. Even after the endless work, giving up on the geared engine wasn’t easy for Chiavetta. “It was hard to pull the plug on it because there is potential there. It makes sense, but takes a lot of engineering to make it work.” Eventually Chiavetta researched the issues Lycoming and Conti- nental had developing their geared engines decades ago and came to the same conclusion we heard repeatedly from those with gearbox development experience: geared performance is real, but geared drive development demands deep resources by pros. Chiavetta’s final advice Having destroyed itself for the umpteenth time, the original, to fellow amateurs considering a gearbox program was direct and firm: planetary gearbox version of Darryl Greenamyer’s 550 Continental “Just don’t do it.” sits broken in a Reno hangar. —T.W.

54 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes Polini, an Italian motorbike and ultralight engine builder, uses a helical-gear PSRU with centrifugal clutch on their THOR 250 Dual Spark engine. The single-cylinder 2-stroke looks a lot like a Honda CR bike engine sitting side-saddle in the Belite’s engine compartment (carburetor to left and exhaust to the right) and is rated at 36.5 hp at 7500 rpm. A 2.8:1 gear reduction turns the 54-inch Powerfin 3-blade just under a familiar 2700 rpm at takeoff and about 2300 rpm at a 6500 rpm cruise. The centrifugal clutch means the Powerfin gets a freewheeling pass at what must be a somewhat jerky idle; the gear drive also provides convenient water pump and starter motor real estate.

PSRU Designs drive is losing its appeal. If anything, Looking at the backside of a small-plane There are two basic categories of prop the latest trend is toward gear drives on belt drive shows how the modest forces speed reducers: belt and gear. Belt- smaller and smaller engines. at play in diminutive engine and prop driven reduction units are simple, rela- It’s possible to use a linked metal belt, combinations allow basic engineering tively lightweight, and don’t pose many but this often results in greater weight, to get by. Physical strength to withstand design difficulties. Gear-drive units not that much more strength, and com- thrust loads is supplied by mass and not triangulation here; harmonic issues are no are either straightforward spur gear plications of the inertial weight of the doubt similarly handled. The tiny engine arrangements where one gear drives belt trying to stand off from the sprock- and wood prop have enough mass and another, or more involved planetary ets at higher rpm. native damping to live a reasonable life, arrangements where many gears are It’s worth noting the one supposed given the small torsionals generated. Also, arranged in a sun-and-planet layout to advantage for belts—isolating the pro- this open-air drive clearly illustrates how belt drives aren’t conducive to hydrauli- drive the propeller. peller from destructive engine vibra- cally operated constant-speed props; if Belt drives typically consist of a tion—is of little utility. That’s because a twisty prop is needed, electricity is the grooved or toothed composite belt and the high-strength fibers in belts— usual solution. a pair of sprockets, one on the crank- strands of Kevlar, steel, and so on—are shaft and another at the propeller, and sufficiently inelastic they transmit exci- as well. Certain engine speeds result perhaps a belt tensioning pulley. They tations with little damping. in the torsional forces harmoniz- are refreshingly simple, typically reli- We’ll also note belt drives keep the ing with the propeller to destructive able, and easy to design units. They tend engine and propeller rotating in the amplitudes. Metal props are especially to be quiet—though not always—and same direction, so reverse rotation props susceptible, as they can vibrate like a while they offset the engine’s crankshaft are not needed. tuning fork. centerline from the propeller’s, this And then there are gear-drive reduc- It is therefore necessary for the pro- isn’t much of an issue, or can even be an tion units. The big deal with metal-to- peller, gearbox, and engine to be tested advantage, with the small engines belt metal gears between the engine and as an assembly to identify and null drives are typically fitted to. propeller is engine torsional vibrations these vibrations with dampers, differ- are not only amplified by the gear ratio ent crankshaft construction, or at least Speed Reduction but are energetically transferred to the avoid operation at those engine speeds. Conditions and Concerns prop. These vibrations originate with This testing requires expensive equip- Major downside to the belt drive is the crankshaft, which does not rotate ment and time, more than all but the its limited torque capacity. Higher- smoothly and is jerked back and forth largest companies can afford. Further- powered engines literally strip belt and by the cylinder’s power strokes; bal- more, change one thing in the prop, sprockets, so by V-8 power levels a belt ance characteristics play a part in this gearbox, or engine and it’s necessary to

KITPLANES October 2016 55 Bob Hume was kind enough to break out for the camera his spare gearbox for the GO-480 Lycomings on his Twin Bonanza. In the outside view the prop flange at left and governor drive on top are readily visible, along with the overall beefy construction (it’s heavy as sin). Peer- ing inside in the second photo, the shiny cover over the planetary carrier is mainly what’s visible. A close look shows two of the six planet gears just poking their teeth out. Also, the gearbox is obviously open to the engine crankcase and shares its oil supply. These gearboxes are reliable, as long as they aren’t coasted or driven by the prop; they rattle like castanets during engine start and shut-down. retest the combination. These vibrations and hardness just some of the players in combination are unloaded relative to are below the limit of human percep- arriving at a transmission that doesn’t each other: the engine isn’t driving tion, by the way, so no one can feel them. eat itself as it’s caught between the the prop, and the prop isn’t wind- Another consideration with a gearbox chattering engine and heavily loaded milling the engine. This coasting can is the design of the gears. It’s a complex propeller. Especially vulnerable are hammer a gearbox like an impact gun thing with gear shape, surface finish, those periods when the engine/prop and results in must-avoid rpm and Rotax: The Factory Gearbox Today there’s just one major aviation piston engine builder making PSRUs standard equipment: Rotax. Champion of the small, efficient 4-cylinder, Rotax offers several variations of a spur gear drive, differ- ing in narrow and wide gear widths, and reduction ratios. Besides the spur reduction, Rotax’s drive also uses a simple dog clutch engagement between the short prop shaft and the spur gear, and may also feature a multi-disc overload clutch. The latter looks just like a motorcycle or automatic transmission clutch pack with alternating “steels and discs.” It’s there strictly to limit impact dam- age back into the engine in case of a prop strike. The dog clutch is where Rotax handles torsional vibration by allow- ing minor decoupling of the engine and prop. The dog clutch has been offered with 15 degree (early) and 30 degree (late) angled ramps. Upgrading to the later angle is part of a TBO extension offered in a service bulletin, the other major TBO increase requirement is fitting composite props are also frangible in a prop strike; while inspec- a late-model propeller shaft with an extra lubrication hole. Generally tions are still required, internal engine damage is very rare with a speaking, the late-model Rotaxes feature TBOs in the 1200- to 1500- composite prop strike. hour range; the 912 ULS is rated to 2000 hours. Again, the Rotax engines are compact with relatively short, There is a gearbox inspection at 600 hours or a littler earlier if stiff crankshafts and are coupled to lighter-weight propellers. This avgas is used. That’s because the lead in avgas sludges in the tight somewhat limits torsional forces, and coupled with the dog clutch clearances of the overload clutch. and extensive testing by this well-funded corporation means Rotax makes recommendations on propeller selection, with the Rotax gearbox issues are unusual, as long as their recommenda- main idea of avoiding too heavy a prop. This is not difficult as the tions are followed. composite props generally used are within the weight limits. Such —T.W.

56 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes manifold pressure ranges the pilot need simply rotates, thus racing the series work around. Our Lycoming GO-480 of smaller gears around the inside of example is so restricted; basically the the large outer gear (other rotational pilot must keep the engine driving the arrangements are possible, but this is propeller at all times. a common layout). Planetary systems Getting back to the gearbox itself, are quiet, keeping the propeller and the simple spur gear design has been a crankshaft on the same centerline and successful layout. Basically put, this is rotating in the same direction. Plan- a small gear on the crankshaft engag- etary systems can also be very strong, ing a larger gear driving the propeller. but they are a bit complex, and tend The gears typically use noisy, straight- toward weight. Planetaries were nearly cut teeth because they are stronger universal on big radials because they and do not introduce thrust loads packaged well and easily accommo- as quiet, angled-teeth helical gears dated a torquemeter—a small hydrau- would. The propeller is offset from lic system that told the flight engineer the crankshaft, which can be useful how much power the engine was mak- if the airframe is designed around ing. That was important for setting it. This was the nearly universal lay- power, checking fuel consumption, out for big WW-II inlines and vees. and analyzing engine health. With the proper development it was strong, simple, and helped streamline Direct Drive: The Practical Choice One Experimental gearbox that’s done the fuselage, plus allowed firing a gun Getting back to the general aviation well is the spur gear on the Thunder through the hollow prop shaft. mainstream, direct-drive engines bolt Mustang. Mounted to the Falconer V-12 and rated to 1200 hp in racing trim, the There’s not much call for cannon- the propeller directly to the crankshaft, unit continues to see detail improve- firing homebuilts, however, and the so the engine and propeller always ments from Thunder Mustang, who designer may not want the expense of rotate at the same speed. It doesn’t mat- offers it at a cool $25,000 for any small- reversing either the propeller or engine ter if a fixed-pitch or constant-speed or big-block Chevy application (the Fal- rotation. In that case, the introduction prop is used, direct-drive means the coner V-12 uses 90-degree small-block Chevy architecture). Oswald Webb, chief of an idler gear between the crankshaft engine and prop are bolted together in design engineer for GKN is credited with and prop gears will keep the prop and lock step. the design. Interestingly, Webb worked engine turning in the same direction. If this isn’t the most engine- or on the Rolls-Royce Merlin reduction The idler gear is very heavily loaded propeller-efficient method, it does gearbox in his younger years. Clearly the because its teeth are alternately forced in boast one of the greatest advantages: design employs extensive lubrication and cooling, judging from the forest of both directions, so it must be very care- simplicity. There is no gearbox weight, external oil lines running over it. John fully constructed, however. no budget-busting cost of carefully Parker at Thunder Mustang says oil pres- Rarely seen, it is possible to use two designed and manufactured gears, no sure/volume was reduced and scrapers idler gears locked to the same shaft gearbox lubrication to consider, no added to avoid flooding the gearbox and to separate half (one direction) of gearbox to overhaul at TBO, no offset improve drain back; overall reliability is excellent. Reduction is 2.8:1 and a quill the gear loads from each idler gear. thrust line, and the engine is physi- shaft is fitted between the crankshaft Such an arrangement also allows for cally more compact. and drive gear to absorb torsionals. two different gear ratios between the Perhaps of greatest concern to a crankshaft and propeller for large gear pilot, direct drive means no operational reduction ratios. limitations due to gearbox longevity Quill Shaft Still using gears but a totally dif- concerns, namely keeping the engine Research any form of power transmission, ferent design, planetary gearboxes are driving the propellers, even during be it in a PSRU, accessory drives, or even commonly used in automotive auto- descent and landing rollout. electric train transmissions, and you’ll come matic transmissions, and are the design Like so many things, direct-drive across a “quill shaft.” This is simply a shaft Lycoming employed on the GO-480 engine/prop combinations may not be that transmits power, but is designed via (Continental favored spur gear drives). the engineering or physics ideal, but its diameter, wall thickness, material, or a Planetary systems use a gear with exter- they are to a surprising degree the prac- combination of such things to slightly twist nal teeth on the crankshaft, a large tical winner. And we’ll close by noting and untwist torsionally. In other words, gear with internal teeth surrounding that direct drive favors large-displace- it’s a bit flexible, a property used to absorb the crank gear, and a series of smaller, ment, low-rpm engines to make useful pulsations in power being transmitted and external-teeth gears in between, mesh- power—another reason such engines therefore protect the gear train. ing everyone together. The crank gear are the general aviation norm. J —T.W.

KITPLANES October 2016 57 Documenting Your Build By David Boeshaar

According to the FAA web site, one of builder’s log, receipts, and photos in to keep track of it. Spreadsheets will the things you need in order to receive the box. have two columns, and a word pro- an Experimental special airworthiness 3. A picture really is worth a thousand cessing document will have a table certificate is an aircraft builder’s log. words, so save yourself a lot of spell with two columns: date and descrip- The aircraft builder’s log documents checking and take plenty of photos. tion. Remember, keep it simple. your build from start to finish, with a A smartphone or simple digital cam- 5. If you are using a computer, tablet, collection of notes and photos on what era with a resolution of two megapix- smartphone, or web site, be sure to you did and when you did it. If it is also els or better will work just fine. Print back up your files and photos often. evidence that you built more than 51% and date your pictures. Save your work to a thumb drive and of your project, you get a repairman’s 4. If you want a little more flexibility save it in your file folder box. certificate, too. There are no strict rules with your builder’s log, use a word 6. Print out your log as you go and store about what a log needs to contain, but processing or spreadsheet program the pages in your portable file box. in the end, it will be a document that you hand over to the FAA with all your other documents for getting your air- worthiness certificate. Here are my 10 tips for creating and maintaining an aircraft builder’s log: 1. Keep it simple. The simplest log is a three-ring binder or spiral-bound notebook. Each entry should include a date and a description of what was accomplished. Include photographs and be sure they are dated. 2. Get a portable hanging file box and some hanging file folders. Keep your Aircraft builder’s log. My RV-9A is in here.

58 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes Word processor table with two columns: date and desciption.

Pictures can be printed in color or black and white. Three-ring binders work great for this. 7. If you want to share your journey with others, consider blogging. A blog is short for “web log” that you write and share with the entire world. Check out sites like WordPress.com or Blogger.com for a free host for your blog. 8. If you do blog, print out your blogs often and save them in your file folder box. 9. Keep all your receipts as a part of your builder’s log, especially for items you bought used. One of these days, the tax man is going to come calling, and you will have all your costs docu- mented and be able to show what taxes you already paid. 10. If you do blog, be sure to document Print and the good, the bad, and the ugly. Remember, others can learn from your mistakes. Your builder’s log is evidence that you really built your plane, and it docu- Digital ments your journey. A simple handwrit- ten notebook will work for you, but by sharing with others in a blog, you will promote industry growth and maybe prevent others from making your mis- takes. Finally, be sure your face is in at least some of the photos. J Davi David Boeshaar is a systems analyst for corporate Disney. A former mechanic,

d teacher, and computer

Boeshaar help desk guru at a major university, he is now build- ing a Van’s RV-9A for fun with his brother-in-law. As the new guy in aviation, Dave has learned lots, both good and expensive, Either Format– and hopes to pass along a little help to the builders Great Savings! coming up behind him. Subscribe Now at www.kitplanes.com/subscribe

Photos: David Boeshaar KITPLANES October 2016 59 maintenance matters Torque plates. Despite the admonitions of master mechanics such as Mike Busch, many people are all too eager to pull a cylinder off to have it repaired, rebuilt, or replaced. To say the least, this is not something that should be done without some very careful investigation and consideration. And it is not something that should be done casually by someone with no expe- rience doing it. However, if this needs to be done and you are determined to do it, you really need to take the neces- sary precaution to protect the engine’s internal parts by installing a torque plate immediately after removing a cylinder. Many people will tell you that you Torque plates are installed before any cylinders go on at the Lycoming engine school. don’t need the torque plate; you can Then they are removed one at a time just before installing each cylinder. (Photo: Paul Dye) just use oversized fender washers under regular nuts to keep torque on the crankcase with the cylinder(s) removed. The problem with this is that the steel washers will spin with the nut as you tighten it, galling or scoring the alumi- num crankcase. Torque plates can’t spin, preventing this damage. It’s also pretty easy to rationalize leav- ing torque plates off because, unless you often work on Lycoming engines, you likely do not have any, and purchasing them from Lycoming is a pretty expen- sive proposition. Aircraft Spruce has them listed at $972 each, but with a little inge- nuity and machining work, you can make your own for much less and provide your Two different finished torque plate possibilities. The copy of the Lycoming torque plate engine with the protection it needs. (left) will work with wide or narrow deck engines, but this particular cutoff cylinder base When you remove a cylinder and flange (right) will only work with wide deck engines. Both of these options will do the job relieve the tension on the case studs, well and save big bucks in the process.

Dave Prizio has been plying the skies of the L.A. basin and beyond since 1973. Born into a family of builders, it was only natural that he would make his living as a contractor and spend his leisure time building airplanes. He has so far completed three—a GlaStar, a Glasair Sports- man, and a Texas Sport Cub—and is helping a friend build an RV-8. When he isn’t building Dave Prizio something, he shares his love of aviation with others by flying Young Eagles or volunteering as an EAA Technical Counselor. He is also an A&P mechanic, Designated Airworthiness Repre- sentative (DAR), and a member of the EAA Homebuilt Aircraft Council.

60 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes Our local metal supplier sold us some pre- We drilled the center hole with a 1-inch bit A milling machine makes easy work of cut- cut steel squares that were 6x6 inches. On and then used a boring head to go the rest ting slots in steel and finishing off the torque these we laid out the location of all the of the way to 2.5 inches. plate to exact dimensions. You can use a drill holes, slots and external dimension cuts. press if you just want to drill holes, but the drill press will not really work for cutting slots. you create a situation in which any Make Your Own engine case studs. An extra 1/64 inch movement of the crankshaft could To make your own torque plate you added to the nominal slot dimensions cause the crankshaft bearings to shift. will need some 3/8-inch thick material. should be enough. This shift could easily lead to a major Lycoming uses steel, but aluminum will The connecting rod for that cylinder engine failure the next time the engine work and is easier to machine. The over- will stick out of the hole in the plate. To is run. Even if you are careful, it is easy to all dimensions are about 5½ inches by 5 protect it, you should install a rubber bump the propeller and turn the crank- 7/8 inches (see drawing for exact dimen- grommet that has an inside diameter of shaft. There is even greater risk if you sions). You will need to bore a 2.5-inch 2.25 inches sized to fit your 2.5-inch hole. leave the airplane unattended while diameter hole in the exact center of the I found the appropriately-sized grommets a cylinder is off. Because of this risk, plate and machine a slot that is a little Lycoming strongly recommends that over ½ inch wide by ¾ inch long in each any time a cylinder is serviced, unless it corner as per the drawing. You can do is immediately replaced, a torque plate this with a ½-inch end mill and just work be installed at each location where a the hole out a little bit oversized to cre- cylinder has been removed. ate a little extra room for the ½-inch

Here is a drawing to make your own torque plate. This was made by measuring dimensions on a Lycoming engine school tracing and a wide deck cylinder base flange. The dimensions may not be precisely accurate, but they should be pretty close. (CAD drawing: Ed Zaleski)

Photos: Dave Prizio KITPLANES October 2016 61 A grinder works well for putting a radius on the outside corners. Use a metal-cutting band saw to remove the cylinder base flange This could be done with a mill, but it is a lot of work unless you from a discarded cylinder. Be sure to slow the blade down enough have a CNC machine. to cut steel without burning it up. A torch or plasma cutter would also do the job. at Del City (www.delcity.net). They cost second set of slots or holes should be Wide Deck vs. $21.06 for 10 including shipping. 4.79 inches center-to-center from the Start by cutting 3/8-inch thick stock to first set. Then relieve the long sides by Narrow Deck the overall dimensions of 57/8 inches by 5/16 inch each as shown in the drawing, so From time to time you may hear the terms 5½ inches. With the plate cut slightly the plates will clear the smaller cylinder “wide deck” and “narrow deck.” Early oversized, you can mill the edges studs. Lastly, install the grommet and Lycoming engines up through the late smooth to precise dimensions. Next drill you are finished. 1960s to the early 1970s came in what or bore a 2.5-inch hole in the exact cen- After removing a cylinder, install the was then the standard configuration. This ter of the plate. You can use a hole saw torque plate with the ½-inch nuts used included case studs that screwed into the if you take your time or bore the hole to hold the cylinder down and torque engine case, as opposed to the current out with a milling machine, depending them to 25 foot-pounds. Let the con- pressed-in through-studs, and cylinder on what equipment you have available. necting rod protrude through the rub- retainer nuts that needed a hex key type You then need to make four slots, one in ber grommet where it will be protected wrench to tighten or remove them. There each corner, that are ½ inch by ¾ inch. If from damage. Remove each torque were some other internal differences you are only going to work on wide deck plate just prior to installing a new cyl- between these and later model engines, engines, you can just drill four ½-inch inder and re-torque the nuts as per too. With different models changing at holes. The slots should be aligned so Lycoming Service Instruction SI 1029D. different times, by the early 1970s all their length is parallel to the short side of By doing this you will ensure the sta- Lycoming engines switched over to the the plate at 4.20 inches on center. If you bility of the crankshaft bearings and wide deck configuration, thus leaving the just want wide deck holes, the ½-inch greatly reduce the possibility of bearing older standard layout to inherit the name holes should be 4.46 inches apart. The problems later. If you cut slots in each “narrow deck.” Wide deck engines use more normal looking nuts on the studs to hold the cylinders in place (except for the IO-390 and IO-580, which use the hex key type nuts). And the spacing between the studs has been spread out or widened, thus the name “wide deck.” One way to tell if an engine is a wide deck or narrow deck model is to look at the serial number. Wide deck engines have serial numbers that end in ‘A,’ but narrow deck engine serial numbers end in a number. The new roller-tappet engines, all of which are also wide deck engines, have serial numbers The remainder of the cutoff barrel can be A finished wide deck torque plate made turned down with a lathe or ground down from an old cylinder flange. The portion of that end in “E.” to remove sharp edges, depending on the barrel that protrudes into the engine —D.P. what equipment you have available. case has been left in place.

62 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes Folding Portable

SHOP GPS Mount TIPS By Jim Fleischman

I upgraded my portable Garmin GPSMAP 396 to a GPSMAP 696 to get out from under XM satellite fees and to take advantage of free ADS-B. Although the 696 is about the same size as an iPad mini, it’s still roughly three times larger than my 396. This was a bit of a problem. Because my RV-4 does not have a lot It is really nice to use a lathe to finish off of available real estate, almost any fixed holder would complicate getting in or the rough edge left from removing the out of the aircraft. flange from the barrel. Of course, if you The solution was to build a universal mount that easily folds out of the way. I don’t have a lathe a grinder will do. used some scrap 3/32-inch aluminum, scrap piano hinge, and a folding lid brace corner as per plan, your torque plates that is available from most hardware stores for under $5. The mount bolts to the will work for any Lycoming four-, six-, or underside of the cockpit rails, and the fabricated brace end attaches with some eight-cylinder engine. spray adhesive. The display just mounts with Velcro strips. J It is a shame how much Lycoming charges for these plates, considering how important they are. The good news is that with some effort and less than $70 worth of material, you can make a set of four or six for yourself.

Another Way to Make a Torque Plate An alternative method of making a torque plate is to simply cut the flange off a discarded cylinder. Any engine shop should have some of these avail- able for next to nothing. For example, the good people at Corona Aircraft The portable GPS mount bolts to the The mount folds against the cockpit Engines gave me an old cylinder with underside of the cockpit rails in the sidewall, making it easy to get in and a cracked head for free. The downside author’s RV-4. out of the aircraft. to using a cylinder flange is that you do not have the rubber grommet to protect the connecting rod. You will also be lim- ited to wide deck or narrow deck only, depending on the cylinder you get to work with. Be sure to get the cylinder that matches your engine before con- verting it to a torque plate. However you make your torque plates, the most important thing is to use them. A shifted crankshaft bearing could bring about a real catastrophe. Best practices dictate that the engine manufacturer’s recommendations be followed when it comes to working on their engines. Be When in use, the mount is supported The Garmin GPSMAP 696 attaches to sure to follow best practices when work- by a folding brace that extends from the mount with Velcro strips. ing on yours. J the tray to the cockpit sidewall.

KITPLANES October 2016 63 Home Shop Machinist The vise squad. The vise is one of the simplest machines Expect to pay a lot for a good bench solid foundation becomes obvious the ever invented. Yet, a Google patent search vise: over $500 is typical, even for a used minute you start sawing, filing, or bend- for “vise” returns more than 3 million hits. one. The reason is a good vise will last ing large or heavy workpieces. You don’t Included in those hits are vises for ortho- forever and, despite all the patents out need a more demonstrable example of pedic surgery (called “bone-bending” there, the best designs, such as the clas- Newton’s Third Law than a wobbly bench. vises—ouch!), ski maintenance vises, var- sic Wilton “bullet” style, haven’t changed ious pin vises and, naturally, scores and much in 60+ years. Milling Vise scores of vise designs for holding and You don’t have to bolt a bench vise to a The key feature of the modern milling machining odd shapes and sizes. bench. But that’s the usual way to anchor vise is the clamping wedge that forces a vise. The importance of having a heavy, the movable jaw onto the saddle of the Bench Vises Bench vises come in small, medium, and large varieties, and there’s a wide range of quality available. To save cost, low- priced tradesman-style vises sometimes combine cast iron parts with tubular steel. High-end vises are either all forged steel or cast iron. Regardless of construc- tion, a good vise is one where the mov- able jaw is not wobbly, where both jaws Inexpensive tradesman-style vises like line up square and flush, and, if it has a this are part cast iron, part steel tube con- swivel base, the swivel mechanism and struction. Note how the ram is exposed hold-downs work smoothly. aft of the anvil.

My friend Bryan Wood bought this mas- sive vise on eBay for his racecar shop. He This 1950’s “baby” vise is reserved for This is a classic example of a swivel base, wanted it both portable and rock solid. The light-duty tasks on small parts (the jaws bullet-style machinist’s bench vise. The vise itself weights a whopping 135 pounds. are only 21/2 inches wide). Note how jaws are four inches wide. This might also The base is made of ¼-inch thick, four-inch it’s lagged to a hardwood T-base. This be called a “combo” vise for the pipe- square tubing and is TIG welded. Bryan left allows the vise to be stored away and clamping, serrated V-jaws visible in the an opening to fill the base with lead shot if then clamped, as needed, to the wood- throat. Note also the vise is bolted to a it needed it (it didn’t). If taking two people working bench. solid three-inch-thick benchtop. to move it counts as portable, it’s portable.

Bob Hadley is the R&D manager for a California-based consumer products company. He holds a Sport Pilot certificate and a Light-Sport Repairman certificate with inspection authorization Bob Hadley for his Jabiru J250-SP.

64 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes Typical mill vise with fixed base. In this case A large, six-inch mill vise with a swivel base A typical CNC-style vise, mounted on a the vise is attached to a hold-down plate and speed handle. It is fixed to the mill table Tormach Personal CNC machine. The vise to allow positioning independent of the with T-slot hardware. is bolted to a fixture plate, which is fixed to T-slots on the mill table. This vise has 4-inch the mill table with T-slot hardware. wide jaws. The “speed” handle slides on and off the hex end of the clamping screw. vise. Prior to the introduction of this fea- ture, the movable jaw, and with it the part being clamped, would have a ten- dency to ride up and off the saddle as the vise is tightened. This made it more or less impossible to maintain a reliable Z-axis (up and down) reference for pro- Milling vises have a wedge that drives the movable jaw into the saddle. duction work. Mill vises are typically attached to the vises can be ganged closely together for sine vise is used most often as a conve- mill with T-slot hardware. The base can more efficiency. nient angle-adjustable welding vise. It be fixed or swivelled. The swivel feature may be overkill for welding, but it sure is usually engraved with degree marks Sine Vise is nice. to facilitate angle settings. Mill vises, like The sine vise is a specialty vise used pri- To set the vise to a particular angle, bench vises, are typically sized according marily for tool grinding or other work you can either use a calculator with trig to the width of the clamping jaws and that requires a precise angle setting. The functions, or an online sine angle calcu- how wide the jaws open. concept is simple: two precision bars (aka lator (find one at http://tinyurl.com/ Vises for CNC milling machines repre- sine bars) are positioned at a fixed dis- z33udhf). The output number represents sent the best precision. Typically a CNC tance in the base. The vise pivots around the distance from the sine-bar tangent to vise will not have a flange or any protrud- one sine bar while the other provides a the base. The most precise angle settings ing bosses for fixing the vise with T-slots. tangent reference surface. require using gauge blocks, but if using The presumption is most CNC work is Sine vises used to be expensive, tool- it for welding or other makeshift jobs (as production oriented, so the vises are room only items, but low-cost imports in not super precision), the sine vise can designed to be bolted directly to a fixture from China have made owning one be set with a caliper, protractor, or digital plate. By eliminating the flange, several downright affordable. In my shop the angle gauge. J

Using the center-to-center distance to An example of an inexpensive (about $150) sine vise. This one sees more use on the welding calculate the spacing required to precision table than anywhere else in the shop. set any desired angle.

Photos: Bob Hadley KITPLANES October 2016 65 Jeff Auen’s Lockwood AirCam (The GuitarCam) It’s the oldest/newest AirCam. Serial number 26, purchased in 1996, was moved in crates and boxes six times over 11 years to five states. It had about 2500 miles on it prior to construction. I called it the Ground- Cam for a long time. The build began in earnest on April Fools’ day 2014. When the kit was purchased, fuel-injected Rotax 912 IS Sport engines did not exist, nor did Dynon Avionics’ SkyView system. I guess that’s a good argu- ment for an abundance of patience. The plane has been modified to easily attach floats and the new full enclosure. Each individual piece of aluminum has been Alodined, primed, and painted prior to assembly to prevent corrosion. With lots of help and encouragement from the wonderful pilots at Essex Skypark in Maryland, it flies hands off with no control tweaks or adjustments. Thanks to Phil Lockwood for a magical design and for supporting even the early kits. Thanks to my pilot consultants and teachers, Carlo, Claudius, and Joseph. Extra-special thanks to my wife and kids for allowing me to have my “part-time job” for 17 months. I’ll be exploring every tributary of the Chesapeake Bay. Essex, MarylanD [email protected]

Jon Croke’s Zenith CH750 Cruzer My new Zenith CH750 Cruzer is powered by a rebuilt Continental O-200 engine driving a WhirlWind propeller. From start to finish the kit took just a year to complete—you could not ask for an easier kit to build! The panel includes a pair of MGL XTreme displays that interface nicely with the O-200. I get about 100 mph cruise speed. Closest thing to building your own C-150 you can have! Brussels, Wisconsin [email protected]

Tim Binder’s Rebuilt Long-EZ I recently rebuilt this Long-EZ. It took 13 months working on it most days and nights. The fiberglass, paint, interior, avionics, and some wir- ing was redone. A Lycoming O-320 is now pumping out 180-185 hp. A cruise prop is needed, but it’s still doing 190 mph. The first test flight was October 10, 2015. This Long-EZ also has a smoke system for safety reasons—can you see me now? More speed mods are planned and heated seats for the cold Iowa winters. This EZ is our fourth canard either built from scratch or a rebuild; the first one was used by Scaled Composites to test a pulse engine and is in the Dayton Air Force Museum. Burlington, Iowa [email protected] J

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KITPLANES October 2016 71 Condition inspections, N-number problems, removing an electrical system and transponder. By Mel Asberry Question: My Mustang II received requirements for Amateur-Built aircraft Can an Experimental aircraft owner its airworthiness certificate almost under 14 CFR 21.191(g). remove the electrical system and a year ago. Now I find that I’m Question: I am trying to acquire transponder and still be legal? Can nowhere near completing the 40- a special N-number from a recently a wind generator powered or air- hour Phase I test period, and I’m de-registered Experimental aircraft. craft battery only transponder be going to need the annual condition The aircraft was de-registered by removed? Many aircraft like Cubys, inspection very soon. Can I do it the FAA because the owner/builder Baby Aces, and other simple air- myself, or must I hire an A&P? did not request renewal and let the planes sometimes have full electri- Answer: If you have obtained the registration lapse voluntarily. I have cal systems, but a new owner would repairman certificate for your aircraft, the correspondence from the FAA like to convert it back to simple. then you can perform the condition regarding this proceeding, and in Answer: Part 91.215 pertains to all inspection yourself. If not, you will need it the aircraft registration branch U.S. registered civil aircraft operating to hire an A&P to do it. manager states that “If no request under part 91 rules. There are no differ- Question: I recently bought a is made (prior to cancellation), the ences noted for Experimental/Amateur- Hollmann two-seat gyroplane sans N-number will be cancelled and Built aircraft. The requirements are the engine, circa 1980. It spent a lot designated as unavailable for the same regardless of the classification. of time outdoors and needs a lot next five years.” Is there any way A transponder is required for all air- of work. I also refurbed an ’87 13b to get this N-number out of its five craft operating within the listed airspace Mazda engine to put in it. I con- year exile? unless the aircraft wasoriginally certifi- tacted the local FSDO, and they say I Answer: I’m afraid that this is a ques- cated without an engine driven electrical can’t get a tail number because I will tion for the FAA Registration Branch system and one has not been subsequently be repairing it, as opposed to build- in Oklahoma City. I would call up added. In other words, if the aircraft has ing it. Is there any possibility of suc- there and ask to speak to a supervisor. ever had an engine-driven electrical sys- cessfully getting a tail number? My guess is that the five-year holding is tem, the exemption does not apply. Answer: Unfortunately I’m going to to accommodate the original owner if Just like the LSA regulations, an air- have to give you the same answer that he changes his mind. If you know this craft cannot be “backed into” the tran- the FSDO office did. The aircraft has person, maybe you can have him send a sponder exemption. J already been fabricated and assembled. letter stating that a renewal will not be The work that you have done would be requested. It never hurts to try. Please send your questions for DAR considered a repair or rebuild, neither Question: Can you explain FAR Asberry to [email protected] with of which meets the “major portion” 91.215 as it applies to homebuilts? “Ask the DAR” in the subject line.

72 KITPLANES October 2016 Photo: Mel Asberry Wing root junctions. Aerodynamically, an airplane is more The drag caused by the interactions of than on the bottom. The flow over the than the sum of its parts. As the air flows the component airflows is called inter- upper surface of the wing is much more over a component of the airplane, the air- ference drag, and it can be a substantial sensitive to interference that might flow is altered. This affects the flow over portion of the drag of an airplane. cause premature separation or stall than other parts of the airplane. These effects the flow over the lower surface. vary in importance. For some configura- A Critical Junction Better wing-to-fuselage junctions tions, the effect is small, and for others it One of the most important areas of aero- are an argument in favor of high-wing is very large. dynamic interference on an airplane is airplanes. On most high-wing configu- The importance of interference effects the junction between the root of the rations, the upper surface of the wing was first noticed as designers attempted wing and the side of the fuselage. A flows smoothly into the upper skin of to predict the drag of their creations. In poorly designed junction can cause a the fuselage. The fuselage side does the world before computational fluid large increase in drag and a reduction not cut the upper surface of the wing, dynamics, aerodynamic predictions in maximum lift, which increases stall and hence does not interfere with the were made with a combination of first- speed. The drag effect can be particu- flow over it. principles theory and experimental data. larly severe in climb and economy cruise, The wing/fuselage intersection on NACA and similar research organizations where the lift coefficient is high. most high-wing airplanes affects only developed large bodies of experimental In general, junctions on the upper sur- the less-critical lower surface of the wing, data on airfoils, wings, fuselages, etc. face of the wing are more critical than provided the windshield and aft fuselage For many years designers believed that lower-surface junctions. The local airflow are properly shaped to guide the flow they could predict the total drag of an is moving faster on the top of the wing onto and off of the top of the wing. airplane by simply measuring (or calculat- ing) the drag of each one of its compo- nents (wing, fuselage, tail, landing gear, etc.) separately and then adding up the drag of the components. Unfortunately, it turned out that this method was not par- ticularly accurate. Sometimes the drag it predicted was close to the actual drag of the airplane and sometimes it was not. The reason for this is that the “summa- tion” method of drag estimation ignores the aerodynamic interaction between the various parts of the airplane. When the wings, fuselage, tail, landing gear, and other components are assem- bled to form an airplane, the airflow over each component is altered somewhat by the presence of the other components in the airstream. Usually these interactions have undesirable effects on drag. Figure 1: Flow separation at the wing root causes a vortex that increases induced drag.

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 Barnaby Wainfan unconventional airplanes including canards, joined wings, flying wings, and some too strange to fall into any known category.

Illustrations: Barnaby Wainfan KITPLANES October 2016 73 Although it is more difficult to achieve, with proper design of the fuselage and wing-to-fuselage junction fairing, low- wing airplanes can have interference drag that is no higher than that of high- wing airplanes. Because the airflow over the upper sur- face of the wing is so sensitive, the design of the wing-to-fuselage junction area requires careful attention. One popular myth, which appears over and over in the popular aviation press, is that if the angle between the wing surface and the fuse- lage side, in the front view, is 90 degrees or more, the junction does not require a fillet or any form of fairing. This is most Figure 2: The position of the widest point of the fuselage greatly affects flow separation at definitely not true. There are many air- the wing-root junction. planes with 90-degree or near-90-degree wing junctions that could benefit signifi- has its widest point at or near the trailing is an example of a low interference drag cantly from the addition of a root fairing. edge of the wing, then premature flow design. The upper surface of the wing A rule of thumb that is useful is that separation at the wing root is much less is uninterrupted and the lower surface if the junction occurs at an angle of less likely. The Thorp T-18 and the Questair joins the fuselage at a large angle, thus than 90 degrees then a fairing is usually Venture both use this type of fuselage minimizing the undesirable corner necessary. However, this does not mean shaping to minimize separation at the effects on the airflow. that a fairing is unnecessary if the junc- wing-root junction. tion angle is greater than 90 degrees. Even in a situation where major sepa- Reducing Drag ration is not expected, some filleting is Here are a few general rules for design- View from the Top still a good idea. Air flowing in a corner ing wing root junctions with low interfer- The plan (top) view shape of the fuselage between two surfaces is slowed down ence drag: in the area of the wing root has a large by skin friction with both surfaces. This 1. Keep the included angle between effect on the flow over the wing root. On causes the boundary layer to thicken and the wing surfaces and the fuselage as many light airplanes the fuselage sides generate more drag. It also may produce large as possible. This is particularly begin to pull inward rapidly immediately early separation. Radiusing the corner important on the wing upper surface. aft of the cabin. Unfortunately, this occurs with a fillet accomplishes two things. First, 2. The sides of the fuselage should not ahead of the trailing edge of the wing in the wetted area in the area of the corner pull in sharply in the top view in the an area where the surface of the wing is is reduced. Second, the air will not have area of the wing-to-fuselage junction. sloping downward and also pulling away to rub against both surfaces forming the This is illustrated in Figure 1. from the direction of the airflow. The air corner and will accordingly produce less Without the fillet, the junction may not be able to follow the changing skin friction drag. Fillets are particularly is likely to exhibit separation in the slopes of both the wing and fuselage at effective in areas where surfaces meet at shaded areas at relatively low angles the same time in the area of the junction. angles significantly less than 90 degrees. of attack. The airflow may be sepa- The flow may separate and cause drag One common example of this situ- rated during climb and slow cruise. and a premature stall. ation is at the wing root of a low-wing This early separation will hurt rate of Since most wings stall from the root airplane with a rounded fuselage cross- climb and increase stall speed. If other first, a poor root junction design can section and/or dihedral in the wing. With design considerations force the fuse- cause a portion of the wing root to stall no fillet, the air must flow through a nar- lage to have this type of shape, then a at climb angle of attack. This premature row channel where it is rubbed on by the large fillet should be used to eliminate root stall will hurt the rate of climb and skin on both sides. Adding the fillet will the root flow separation. increase the stall speed of the airplane. clean up the flow in the corner area and If the fuselage has a constant or This situation is illustrated Figure 1. The reduce drag. slightly increasing width in the area separated zone can be eliminated by the Proper design of the fuselage can of the wing, the chances of early flow use of a proper root fillet, unless the con- minimize the interference drag caused separation at the root are reduced. A tour of the aft fuselage is too extreme. by the wing root junction and reduce the fillet may still be required, but it can be Another solution to the junction prob- size of the root fairing required. A high- smaller and the penalty for not filleting lem is shown in Figure 2. If the fuselage wing configuration with some dihedral this type of wing-root configuration

74 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes will be much lower than it would be for 4. Avoid gaps between the wing and junction is likely to be severely con- a configuration where the fuselage is fuselage: Any gap between the root of fused and will likely separate or form a pulling in sharply over the wing. the wing and the fuselage should be vortex. This will cause additional drag. 3. The fuselage should have no corners well sealed. Air leaking through such Proper design of the wing-to-fuselage or areas of large curvature in the plan a gap if it is left unsealed can markedly junction is particularly important if the view in the area of the wing. A corner increase the drag of the airplane. Leak- designer chooses to use one of the new or sudden change of direction in the age can produce flow separation on generation of aft-cambered airfoils. shape of the fuselage can induce sepa- both the wing and fuselage where they Because of their camber distributions, ration, even if the wing isn’t there. The join. It can also increase the induced these aft loaded sections are likely to addition of the wing makes the airflow drag of the airplane. The gap acts be quite sensitive to the perturbation of more sensitive and easy to separate, somewhat like an additional wingtip. the airflow produced by the fuselage. A particularly in the region just above This effect decreases the effective good wing-root junction is essential to the wing. If the airflow does separate aspect ratio of the wing by reducing prevent separation. at the corner, it will cause separation the span efficiency factor and increases Wing junction design seems to be over the upper surface of the wing in the induced drag of the wing. one of the most neglected areas in light addition to the fuselage side. 5. Avoid situations where the wing is airplane design. Many production and If other considerations cause the pushing air one way and the fuselage homebuilt airplanes lack any form of root fuselage to have a break, the break is pushing it the other way. An exam- fairing at all, and many others have root point should be aft of the wing to ple of this is an aft-cambered wing treatments that are inadequate to mini- reduce the chances of separation and mounted low on a fuselage that pulls mize interference drag. What is true of interference drag. Corners are never up sharply just aft of the wing. The air wing-to-fuselage junctions is also true good from the drag point of view but leaving the wing is being deflected of tail-surface-to-fuselage and wing- if they are going to be used to reduce down. The air flowing over the bot- to-nacelle junctions on multi-engined construction cost or time then they tom of the fuselage, just inboard of airplanes. Cleaning this up provides an should be placed where they do the the wing, is being deflected up by the opportunity for significant drag reduc- least harm. fuselage. Clearly, the air right at the tion on many types. J 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, circulatiOn billinG center or other similar names. Addresses for these firms include Dallas, tX; lincoln, ne; Omaha, ne; san luis Obispo, ca; salt lake city, ut; White city, Or 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, Dial america 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 535 connecticut ave norwalk ct 06854 should you have any questions at all about mail that you receive, please contact us at our web site: www.kitplanes.com/cs or call us toll free to speak to customer service.

KITPLANES October 2016 75 Workbench. Every now and again, I go off on a last time for nearly 40 years…sorta. I work on. Mostly they’ve been 2x4 frames wild hair and do something completely decided with reader Dave (“Dr. Dave,” flies with wood doors for tops. This one is different than what you are used to. I’ve an Aeronca Sedan on floats out of Anchor- an absolute blessing to work on that I made the most complex project I’ve ever age) Mulholland’s prodding, I was going to should have had a long time ago. attempted in a KITPLANES® article—a make the electronics bench of a lifetime. full-house VOR/ILS/Marker test genera- Here you go: nothing but half-inch Building Materials tor. I’ve done some really simple things plywood, a door, and a little bit of lami- • Three sheets of half-inch plywood (CDX like a headphone tester out of a single nate flooring to the project, and it is the or shop grade), about $20 per sheet AA battery. Last April, we did some fool- electronics workbench. For another Weir • Five 8-foot-long 1x2-inch furring strips ishness about the bread-cat emergency two-fer I’ll share the equipment and (hemlock fir), about $1.50 per strip generator. This month you get the ply- parts shelf designs for your shop. • Five 8-foot-long 2x2-inch furring wood workbench. I must admit to being just a little bit strips, about $2 per strip I’ve been wanting to design my own ashamed. I’ve been in this business for • One package of laminate flooring ultimate electronics work bench for nearly 60 years now, all the way from a 12 year (enough to cover at least 17 square 60 years. I’ve always cobbled something old sweeping out the TV shop and then a feet), about $25 together out of an old door and some professional engineer designing avionics • One gallon of boiled linseed oil, scrap 2x4s with a light dangling from a for the last 50 years. In all this time, I’ve about $15 string attached to the ceiling. That worked never had a really good workbench to • One very long power strip, about $20 • One solid-core door, 6 feet 8 inches x 30 inches, about $50 (Hollow-core door about $25) • Miscellaneous glue and nails Start out by having the lumber shop do one major cut lengthwise on each sheet of the plywood. Sure, if you’ve got a table saw and competent help, you can make the cuts yourself. At a buck a slice, it is worth it to me to have the young kids in the saw shop schlep the plywood around. In the airplane world, we are used to building our aircraft from the “top down.” That is, the tail feathers or wings generally get done first, then the fuselage, and only then do we do the landing gear. We build benches exactly the opposite way: first the foundation, then the walls, and then the working Construction details of the electronic test bench. top surface.

is the chief avioniker at RST Engineering. He answers avionics questions in the internet news- group www.pilotsofamerica.com–Maintenance. His technical advisor, Cyndi Weir, got her Masters degree in English and Journalism and keeps Jim on the straight and narrow. Check Jim Weir out their web site at www.rst-engr.com/kitplanes for previous articles and supplements.

76 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes Beginning the assembly of the bench. The bench bottom is just The bench shelving all done and braced for the attachment of about ready for the first of the shelf sides to be attached. Note the door. Note that the lab flooring bears a strong resemblance in the background all the rest of the bench parts cut and ready to the laminate used on the benchtop surface. It’s exactly the to assemble. same stuff.

I wanted more storage than the law (you can use a hollow core door for half flooring (it is held on by four screws in should allow. Each of my pieces has more the price, but it doesn’t feel as solid), the corners) and replace it. No hassle, storage than I’ve ever had, and I think I’ll then lock-together laminate flooring on no mess. I highly recommend this lami- just about have enough for all my stuff. top of that. I tested the laminate before nate for anything you want to have as a Each bench, then, needed to have room I used it. I couldn’t scratch it with a sharp benchtop, whether it be electronics or underneath to store all the stuff that I center punch. I couldn’t burn it with hot engine work. Tough stuff. need to keep for all my projects. You can solder splashes or a hot soldering iron never have enough storage. for a few seconds. Yes, after two minutes More Furniture I’ve always in the past had a bench- of the hottest soldering iron I had and The bench turned out so well, I built all top that wasn’t exactly great to work continuous contact with the laminate, it the rest of my lab furniture the same way: on. In general it was a hollow-core door discolored. It didn’t burn. It didn’t scorch. plywood structure reinforced with hem with a door skin as my working surface. It simply discolored and then only after fir furring strips. For the heavy stuff (like I wanted something better. I decided to a couple of minutes of torture. Good the power supply and oscilloscope on use the belt and suspenders approach. benchtop material. the test bench) I’ll put a vertical support The underlayment for the top was a Now, if at some future time I really on the shelves. On one of the assembly solid-core door with cheap lauan skin abuse the bench, I simply remove the benches, I don’t have the luxury of a

The soldering iron gets its own little mini- bench with sides on it to keep solder rolls, desoldering tools, and the ubiquitous toothbrush board cleaner from rolling all How to slice the plywood for minimum scrap. over the bench.

Photos and diagrams: Jim Weir KITPLANES October 2016 77 The engineering bench ready for the laminate top and top shelf. The finished electronics bench itself. The test equipment on the Note that the bottom is one single long sheet of plywood, and top shelf is angled down with a combination of wood blocks under the top is a standard solid-core door 30 inches wide. the back of the equipment, rather than having the top shelf angled. Much safer this way. vertical support, and I had to resort to a Each of these pieces of equipment chance of the equipment sliding off of a piece of 2x2 angle iron to keep the ply- needs to be read face-on direct (some- slanted surface; if it slips off of the furring wood shelf straight. thing about parallax readings being strip it simply plops down onto a flat sur- Yes indeedy, I’ve got a thousand dol- inaccurate). The problem is that build- face and that is the end of that. lars in materials to make 14 complete ing the shelf on the slant does not take I’m an RF cat; I work in the black magic lab shelves (two workbenches, two into account the different angles needed world of Megahertz and Gigahertz, so parts shelves, three equipment shelves, for each piece of test gear—and once a the instrument on the far left in the a computer desk, and six bookshelves piece of gear starts to slide, it just keeps bench photo is a “service monitor,” a that would cost well over five grand if on sliding. The answer is that I built $15K piece of 10 Hz to 1 GHz equipment I were to go out and buy them on the the shelf itself square, and then for the that is a precision signal generator, commercial market. Take that extra instruments that needed to face down spectrum analyzer, modulation meter, four grand and go buy some decent a bit, I used a combination of the afore- power meter, frequency counter, and test equipment. mentioned 1x2 and 2x2 furring strips, communications receiver all in one Speaking of which, note my four cut for each instrument, to prop the package. There’s also a garden variety pieces of test equipment on the equip- back end of each individual instrument (Heathkit) power supply for 12/24-volt ment shelf above the lab test bench. up and therefore slant the face down. No work, an inexpensive sine/square wave

The “engineering parts” shelving stuck over in the corner next to It rarely gets below 20°F, but an electric forced-air heater with a the workbench. Each of the parts boxes has 60 little drawers for “dummy” woodburning lamp makes the place warm and cheery little electronic parts. There are 540 little drawers, each of which during the non-fly months of winter. The card rack above with the can be divided into half for really small parts. There’s room on little kids kissing is my wife’s reminder that we were about this age the bottom for plastic boxes with larger parts that wouldn’t fit when we shared our first kiss nearly 60 years ago. Note that the engi- in the drawers, and room on top for more plastic boxes with the neering toolbox is on a stand just to the right of the fireplace and is remains of old projects (including some KITPLANES® projects made from solid 2x12-inch Doug fir to support the weight of the tool- more than 15 years old). box. Note also that on top of the toolbox are the plastic “deli” boxes I mentioned using for small parts in the October 2015 KITPLANES®.

78 KITPLANES October 2016 www.kitplanes.com & www.facebook.com/kitplanes This is the downstairs general purpose workbench. The top is a double sheet of plywood covered with cardboard moving boxes opened up and taped together. So far this one has seen a lawnmower carburetor overhaul, a garden tractor generator repair, a Cessna carbu- retor heat box repair, and a weed whacker cutter head installation. The only thing I would redo if I had it to do over again would be to make the bottom a solid piece of plywood.

1Hz to 1MHz audio generator, a 60 MHz nails. If and when that benchtop gets oscilloscope, and my antique Heathkit trashed, I’ll simply pull off the top ply- transistorized voltmeter, milliammeter, wood sheet and replace it with a new and ohmmeter that has been my right sheet, or if I’m strapped for cash I’ll sim- hand for 40 years. ply turn the plywood over and use the second surface. Note that the top of the Other Workbenches workbench is covered with cardboard Just a word or two about the three cut from cheap shipping boxes. If you workbenches in the downstairs shop/ build the benches exactly 6 feet (72 garage: one for woodwork, one for met- inches) long these shipping boxes will alwork, and one for engine work. Same just fit onto the top. basic construction as the ones upstairs, Now that I’ve got decent benches to but I only used a double plywood layer work on and equipment shelves to put for the benchtop with no laminate. parts on, it is back to the multimeter However, the top plywood layer is not series. Voltage Ahoy! Have fun, see you glued into place, just held with a dozen next month, stay tuned. J

The production parts shelving, nearly like the engineering parts shelving, but a bit taller, with room for all the heavy stuff (like rolls of wire) on the bottom to give the unsupported shelving stability. Rows of plastic boxes on the top are for bulky stuff like shrink sleeving and completed production assemblies.

KITPLANES October 2016 79 By Robrucha

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