S C Aerostar S A YAK 52 N624PT accident near St. Elmo, Alabama

Probable cause

The failure of the right main landing gear uplock actuator due to corrosion.

NTSB analysis

The private pilot of the experimental, imported military airplane, stated that, after takeoff and while retracting the landing gear, he noticed that the pneumatic pressure was low. He then attempted to extend the landing gear using normal and emergency procedures, but the right main landing gear (MLG) remained retracted. The pilot subsequently conducted an emergency landing with the right MLG retracted. During the landing roll, he was able to keep the right wing from contacting the runway for about 1,000 ft. Once the wing contacted the runway, the pilot was unable to maintain directional control, and the airplane exited the right side of the runway. The right aileron sustained substantial damage.

Examination of the airplane revealed that the pneumatic cylinder actuator that released the right MLG uplock was not functioning properly. Subsequent teardown examination of the right MLG uplock actuator revealed that moisture had entered the actuator over a period of time and corroded the internal components. The corrosion led to the failure of the actuator.

Text from the NTSB. Open the NTSB docket for ERA17LA105 for the full record.