When I heard that Arnie Clarke had been doing some spin testing on his GlaStar I asked him to write about it for us. I know that many of you are interested in this topic but have been unable to find any reliable information on it. I asked Arnie a series of questions, and they are shown here along with his answers. This is not a recommendation by either myself or Arnie to go out a spin your GlaStar. Such flight testing should not be done without due consideration of the risks involved.
Clarke: Before I answer your questions, some background is needed. I don’t want to encourage others to take their test flying farther than Glasair or the FAA recommends. In my case I wanted my certificate to allow anything I might want to do in the future. If I only asked for the factory recommended weight, G limits and maneuver limits then anything I ever did beyond that would subject me to an FAA violation and possibly void my expensive insurance. I have been flying for 52 years, 21 of them as a fighter pilot in the USAF. I also have done some air shows and test flying in a wide variety of aircraft.
Prizio: How is your plane equipped and what was your weight and CG situation when you spun your plane?
Clarke: My GlaStar is conventional gear with foam and fiberglass gear leg fairings. I have a Lycoming O-360 engine with a Hartzell prop, dual Lightspeed ignitions, a Dynon and Garmin, light instrument panel. I have a dual electrical system with sealed batteries behind Bulkhead A. The empty weight is 1254 pounds including 5 pounds of lead just ahead of the aft bulkhead. The CG is near the aft factory limit.
Prizio: How did you induce the spin?
Clarke: During phase 1 testing I attempted to induce a spin several during flights including loadings aft of the factory limit. It would not do more than a 3/4 turn before recovering, even with full pro spin controls. None of these flights included tip tank fuel or a second pilot. On the flight where it unexpectedly spun, the tips were full of fuel and there were two of us flying. I had briefed to expect it to not stabilize in a spin – but it did go into a stable three turn spin and then recovered normally. I was surprised.
Prizio: Did you go both right and left? Were any differences noted?
Clarke: I do not remember for sure but think we did several more spins in both directions with the same result.
Prizio: Describe the recovery process you used and how it responded?
Clarke: Center the stick, opposite rudder. I was able to stop on the heading I wanted by leading the recovery 1/4 turn.
Prizio: How many turns did you attempt?
Clarke: Three turns; they were stable, and it appeared to me that it would continue for as many as desired.
Prizio: How much altitude did you lose?
Clarke: My memory is weak here, I think about 1,000 feet for the three turns and recovery.
Prizio: Any other comments?
Clarke: I think the weight of the tip fuel with its inertia was what allowed it to go stable. Without the GlaStar’s huge tail it could turn into a flat spin with the potential of being unrecoverable. I tested my GlaStar for its acrobatic ability in the following maneuvers: Spin, Chandelle, Lazy Eight, Split S, Barrel roll, Cuban Eight, Loop, Immelman, Clover Leaf, Diving Spiral turn to 4.2 G, Inverted flight to minus one G. Maximum airspeed was 200 KIAS. At 200 knots the windscreen deflexed in about 3-3/4 inches! The Maximum load carried was 385 pounds of sand bags and full fuel, and it was still climbing at 500 fpm at 14,000′ (winter). The weight at takeoff was over 2,100 pounds. I can maintain 135 KTAS up to 13,000 feet at mid weight.