Tuesday, March 24, 2009
To retract or not to retract? That is the question.
GEAR UP OR DOWN? A senior project engineer with Cessna, Tom Bowen weighs the costs and benefits of flying above fixed gear versus retractable gear (as with the Globe Swift above).
It was a purely stock 1946 Globe Swift GC1B, and while the main wheels would retract— eventually—there often seemed to be little effect on performance. Though the airplane was a cute little devil and a fairly primo example of its kind, its performance was a country mile behind the “book.” Globe’s manual bragged of a 1,000 fpm climb at gross and a 120-knot cruise speed, but that was an ad writer’s dream. The reality was more like 500 fpm and 110 knots, all on a perfect day with optimum biorhythms and a full moon. On a hot day, the tiny electric motor that drove the gear would work its heart out trying to levitate the wheels into the wells, sometimes without success. Occasionally, the gear would get stuck about halfway up and refuse to retract the rest of the way. Other times, it would require 30 seconds to two minutes to lever the wheels into the wells. Fortunately, with help from gravity, the wheels always came back down.
As a result, I received a new pilot’s involuntary education into the difference between retractable and fixed-gear airplanes. The half-dozen airplanes I’ve owned since that first Swift have all been retractables, but over the years, I’ve had reason to question my choice.
Roy LoPresti’s Grumman American Tiger and Cheetah from the late ’70s were startling examples of efficient airplanes with fixed gear, but discounting homebuilts, they were pretty much alone until the ’90s. Today, there are a variety of production airplanes that offer near-retractable cruise speeds with fixed gear. The Cessna 350/400, Cirrus SR20/22, Diamond DA20/40 and Liberty XL2 all deliver excellent performance with the wheels down and welded.
I have a list of sources on all things aviation, and one of the best on aerodynamics and aircraft design is Tom Bowen with the Bend division of Cessna Aircraft. I first met Bowen when he was chief engineer at Mooney, then worked with him after he moved to Columbia Aircraft in Oregon and now deal with him as senior project engineer at Cessna Bend. Bowen has worked for major manufacturers of pistons and jets, retractable and fixed-gear airplanes, so he’s conversant with both sides of the argument. These days, his opinion favors fixed-gear designs.
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