Witnesses reported seeing the private pilot begin the takeoff from the airport in Gasport, N.Y., in the Flight Design CT-SW light-sport airplane. During the rotation, the LSA appeared to pitch up higher than normal, followed by up-and-down pitch oscillations and left bank oscillations. It climbed no higher than about 75 feet.
The LSA began a slow left bank, which was not consistent with a normal takeoff procedure, before hitting trees south of the runway in a left-wing-low attitude.
The pilot told his son before he died that the airplane experienced flight control issues related to the autopilot.
Post-accident examination of the airplane revealed that the flaps were symmetrically extended 15°, and there was no evidence of preimpact failure or malfunction of the flight controls for roll, pitch, or yaw.
According to an airplane performance study, the pilot was operating the airplane about 4 knots above its stall speed during the left turn. However, the location of the main wreckage with respect to the airplane’s last GPS data point indicated that the bank angle likely increased and exceeded the airplane’s critical angle-of-attack, which resulted in an aerodynamic stall.
Data from the engine’s recording device indicated that, during the beginning portion of the takeoff sequence while the airplane was over the runway, the engine rpm decreased about 50 rpm and then increased nearly 900 rpm about the point and time when the airplane banked left and hit the trees.
Post-accident operational testing of the engine revealed that it produced full-rated power with no evidence of pre-impact failure or malfunction.
The reason for the reduced power setting at takeoff could not be determined.
Although the pilot reported that the pitch-and-roll oscillations during takeoff were related to the autopilot, it could not be determined during examination of the autopilot whether the autopilot was engaged during the accident flight.
Post-accident testing of the autopilot controller and roll servo revealed no evidence of preimpact failure or malfunction. The override torque value of the roll servo was within limits.
The autopilot controller minimum airspeed was found set to a value of 0, which would have disabled the minimum airspeed alert if the autopilot were engaged.
The pitch servo was found inoperative due to a failed voltage regulator, however this would not have caused any increased torque or servo runaway.
Following replacement of the failed component, the pitch servo tested satisfactorily, and the override value was within limits.
If the autopilot had been engaged and an autopilot malfunction had occurred, the pilot would have been able to override any pitch and yaw servo commands.
Further, if the autopilot had been engaged and the controller minimum airspeed had been set to an appropriate value, it is likely that a stall alert would have occurred that provided the pilot with adequate time to respond to and avert an aerodynamic stall.
The NTSB determined the probable cause as the pilot’s failure to maintain adequate airspeed following a left turn during takeoff, which led to the airplane exceeding its critical angle-of-attack and experiencing an aerodynamic stall.
NTSB Identification: ERA14LA329
This July 2014 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.