Incident Overview
A pilot reported that during a turn-around maneuver, he extended full flaps (26 degrees) and the flaps remained fully extended, resulting in jamming of the flight controls. The pilot's statement indicates that the flap extension occurred during the turn and that the controls became unresponsive.
Manufacturer Input
According to manufacturer personnel, flaps settings of 5 to 8 degrees may be used as a turning aid. This suggests that the use of full flaps (26 degrees) in a turn was outside the recommended range for such maneuvers.
Component Examination
Post-incident examination confirmed flight control continuity. The wing flap actuator components and microswitches were found intact, without deformation, and tested functional as designed. The actuator jackscrew was measured to be extended 3.5 inches, corresponding to a flaps setting of 26 degrees.
Clearance and Malfunction Thresholds
The minimum push rod clearance at full flaps and full aileron is 0.257 inch. An actuator jackscrew extension of 4 1/16 inches is required before the actuator assembly malfunctions. An extension beyond 4 inches (equivalent to flaps 34.5 degrees) causes the flap push rod and aileron push rod to contact each other, but at that point the controls remain movable.
Analysis of Jamming Condition
The investigation determined that multiple flap actuator assembly malfunctions are required to jam the flight controls. Since the examined components showed no deformation or functional issues, and the jackscrew extension was within normal operating limits, no single component failure was identified that would explain the control jamming reported by the pilot.