During a recent post crash investigation of a Walter 601 powered (not a Lancair) aircraft I was having difficulty understanding what caused a left roll just before the crash on short final. The roll had an average rate of 46 degrees per second and corresponded with a power increase.  Given the 745 available horsepower (near sea level) and the 2,067 RPM prop speed I calculated an engine reaction torque of 1,893 foot pounds, roughly the same as putting a 200 pound weight about mid span on the aileron. Factor in that the airspeed was only 120 KIAS and you get that queasy feeling in the pit of your stomach.

The data shows that plane was on short final when the pilot let the plane get a little low and slow. He drops the nose slightly but doesn't accelerate because of the drag of the prop and/or  he is behind the lift curve.  He punches the throttle and pulls the nose up.  The added load on the left wing due to the torque reaction either stalls that wing or overwhelms the aileron authority and the plane begins an uncontrolled  left roll. Five terrifying seconds later  the plane has rolled 260 degrees and the right wing is pointing straight down. This is the last data point and the plane crashes, with two fatalities, less than 5 seconds later.

To all you LIV Turbine guys out there, remember this well. The Walter is a LOT of motor for those little wings. Low and slow is not a place you want to be and putting in the power is not  always the solution.

I would be interested to know what happens (at 10,000 feet)  if you slow to ~120 KIAS and then apply full power.  Do you still have any aileron authority?

Regards
Brent Regan