Twin Topics Twin Topics is a monthly column devoted to the operation, maintenance, and ownership of Cessna 300- and 400- series piston twins. It is edited by Mike Busch, CPA’s staff twin expert and the lead instructor in CPA’s twin courses. Mike is a regular contributor to CPA Magazine, as well as editor-in-chief of AVweb, the Internet’s aviation magazine and news service (http://www.avweb.com). He also is the owner of a pristine 1979 Cessna T310R which he maintains almost entirely himself. Vortex Generators: Band-Aids or Magic? A recent visit to Boundary Layer Research revealed that there’s a lot more to those little wing and tail bumps than meets the eye, and that they’re not just for twins anymore! by Mike Busch <[email protected]> obody’s ever accused seemed like the only one on the engineers would routinely scoff me of being an early- road that didn’t have one! at the VGs on Boeing jets and Nadopter when it comes Even the most died-in-the- brag, “see, we don’t need those to aviation. I’m unabashedly wool skeptics were unanimous things because we got our aero- skeptical about aeronautical in- that vortex generators are a ma- dynamics right in the first novations until they’ve been jor advance in piston twin safety, place.” proven in the field for years. lowering Vmc by ten knots or so The idea of using VGs to When Mobil AV-1 was being to the point that it is no longer a improve the low-speed perform- touted as the greatest thing since factor (because it is below stall ance of general aviation aircraft sliced bread, I stuck with my speed). And as if that wasn’t came from an ex-Boeing engi- Aeroshell W100. When Cermi- enough, I learned that some of neer named Paul Robertson. crome cylinders were all the the VG kits offered substantial Robertson first tried out his VG rage, I stuck with nitrided steel gross weight increases and sig- idea on a Cessna 206, but while jugs. (Both of those proved to be nificantly slower approach and the VGs did lower the stall mighty good decisions, too.) takeoff speeds. speed, it degraded the plane’s Heck, I’ll probably be the last on It was time. previously docile stall charac- my block to replace my old teristics, so the project was panel-mount LORAN with a How It All Began shelved. GPS; I’m still holding off until Robertson’s next VG ex- they get WAAS figured out. The use of vortex genera- periment involved a D-55 Baron But the easily-visible fact tors is nothing new. First used in that belonged to his partner that my T310R still wasn’t VG England, VGs have been used Mike Anderson. The Baron was equipped was starting to get on transport jets for decades, famous for having a rather nasty downright embarrassing. The and on bizjets since Bill Lear stall characteristics on one en- lack of those little bumps on my invented them. But historically gine, but Robertson discovered wings and vertical tail were they were used as an aerody- that the VGs turned the airplane starting to make me feel as con- namic “band-aid” to deal with into a pussycat and lowered spicuous as I did a decade ago localized mach buffet problems Vmc a full ten knots to the point when Detroit introduced high- at the high end of the airspeed that it was below stall. mounted stop lights and my car envelope. MacDonnell Douglas would be better to keep the money in-house, RAM obtained its own VG STCs for the Cessna 340/340A, 402C, 414/414A, 421C and 425. About the same time, back at Anacortes, both Paul Robert- son and Bob Desroche decided to depart Micro Aerodynamics to start new aircraft modification companies. Robertson founded Aeronautical Testing Services and proceeded to obtain VG kit STCs for most of the Cessna 300/400 twins and the Piper Seneca, and also for the Cessna 120/140, 180/185 and deHavil- land Beaver. Meanwhile, Desro- che formed Boundary Layer Research and obtained VG STCs for the Beech Duke, the Figure 1 — Typical vortex generator installation on a wing. Piper Navajo, Chieftain and Panther, and also for the Super Convinced that VGs had cluding the Baron 55 and 58, Cub. Ultimately, in 1997, Rob- great promise to make piston Twin Bonanza, Cessna 310-320- ertson and Desroche decided to twins safer, Robertson started a 340 and 402-414-421, and Piper combine their VG businesses new company called Friday Aztec. More recently, the com- and Boundary Layer Research International (located in Friday pany has obtained STCs for VG acquired rights to all of Robert- Harbor, Washington) together kits for most of the rag-wing son’s VG STCs. with partners Mike Anderson strut-braced Piper singles (Cub, In case you lost count a and Chuck White. In 1987, the Super Cub, Super Cruiser, Pacer few paragraphs back (entirely company managed to secure the andTri-Pacer) and the Maules. understandable!), this leaves first STC for a VG kit on the Meantime, Friday Interna- four surviving players in the VG Beech Barons. They also put tional changed its name to VG kit business: Beryl D’Shannon, VGs on an A36 Bonanza but Systems and obtained additional Boundary Layer Research, never got far along enough with STCs for VG kits on the Cessna Micro Aerodynamics, and that project to get an STC. 340 and 421B. VG Systems was RAM Aircraft. D’Shannon acquired in 1993 by Beryl offers VGs only for Barons and Turbulent Flow D’Shannon (of Bonanza mod Bonanzas, while the other three fame), who moved the operation companies all offer a variety of Beginning around 1990, to Minnesota and completed the twin Cessna kits. (See Table 1 the story of the VG kit business work started by Friday Interna- for a summary of which firms started sounding like a passage tional to obtain STCs for VG currently offers VG STCs for from the Old Testament. Disa- kits for the Bonanza A36 and which models.) greements between the partners F33. caused Robertson and White to RAM Aircraft in Waco Which One to Pick? leave Friday International and, also decided to get into the act together with their engineering about the same time. Many cus- When it came time to de- test pilot Bob Desroche, form a tomers were asking RAM to cide which company to select to new firm called Micro Aerody- install Micro Aerodynamics VG put bumps on my T310R, the namics in Anacortes, Washing- kits on their Cessna 300 and 400 choice turned out to be pretty ton. This company went on to series twins while the airplanes easy. RAM’s VG kit price obtain STC approval for VG kits were in Waco being fitted with ($2,150) is the lowest of the for numerous piston twins in- RAM engines. Concluding it three companies, but RAM’s VG kits don’t offer any gross weight Beryl D’Shannon Boundary Layer Reserach Micro Aerodynamics RAM Aircraft Lakeville, MN Everett, WA Anacortes, WA Waco, TX 800-328-4629 800-257-4847 800-677-2370 254-752-8381 www.beryldshannon.com www.blrvgs.com www.microaero.com www.ramaircraft.com BEECH BEECH BEECH CESSNA Bonanza 33, 35, 36, 36TC Duke 60, A60, B60 Twin Bonanza 50 340, 340A Baron 55, 58, 58TC, 58P CESSNA Baron 55, 58 402C 120/140 CESSNA 414, 414A Skywagon 180, 185 310G-R,T310R, 320 414AW, 414AW-V 310, 310A–R, T310P–R 335, 340, 340A 421C, 421CW 320D–F 414, 414A 425 (Conquest I) 335, 340, 340A 402B, 402C 401, 401A, 401B 421C 402, 402A, 402B, 402C PIPER 414, 414A Aztec PA23 421, 421A, 421B, 421C Cub J-3, PA11 PIPER Super Cruiser PA12 Navajo PA31-310, 325C/R Super Cub PA18 Colemill Panther I & II Pacer PA20 Chieftan PA31-350, T1020 Tri-Pacer PA22 Seneca II/III/IV PA34 MAULE Super Cruiser PA12, PA14 M-4, M-5, M-7, MX-7 Super Cub PA18 AGPLANES deHAVILLAND Ayres Thrush Beaver Mk I AGPLANES Ayres Thrush, Air Tractor, Cessna 188 AgWagon, Piper PA36 Brave, Dromader, Weatherly Table 1 — Vortex generator STCs…who offers what? increase. Furthermore, RAM nating ZFW) while the MA STC Bob Desroche, who undoubtedly doesn’t presently have an STC offered no ZFW increase. I con- has more test-pilot time certify- for the 310 or T310. So RAM’s cluded that Boundary Layer Re- ing VGs on light twins than any kits were doubly out of the run- search’s STC for the T310R was man on earth. ning as far as I was concerned. both less expensive and better, I’d also been looking for That left Boundary Layer so I decided to go that route. an excuse to fly up to Everett’s Research and Micro Aerody- Rather than order the kit Paine Field (PAE) because that’s namics, both of whom offer VG and install it myself, I decided to where Boeing builds its wide- kits for the T310R (and for most fly the airplane up to Everett, bodies (747, 767, 777) and I’ve other twin Cessna models as Washington, and have BLR do long wanted to take a tour of that well). Both kits looked good, the installation. Although the facility. So I made an appoint- and both offered comparable VG installation is simple enough ment with BLR for the first week gross weight increases. But (one might even go so far as to in August (while everyone else BLR’s was priced $500 less call it idiot-proof) and can be was off at Oshkosh) and had a ($2,450 vs.