Accident Overview
On March 8, 2019, at approximately 1000 eastern standard time, a Piper PA-31-325, registration N45MJ, was substantially damaged during a landing gear collapse while taxiing after landing near Leesburg, Florida. The pilot, who was the sole occupant, was not injured. The flight was conducted as a flight test under 14 Code of Federal Regulations Part 91.
Preceding Events
The pilot had delivered the airplane to a maintenance facility for its annual inspection. During the inspection, maintenance personnel suggested installing an inner landing gear door kit (STC SA00555DE). After installation, numerous test flights were performed to verify the landing gear operation. During these flights, the pilot observed that the green landing gear indicator light for the right main landing gear was very slow to illuminate, while the other two lights appeared normally. Adjustments were made after each flight to address the issue. On the final flight, during taxi back to the ramp after landing, the right main landing gear collapsed.
Post-Accident Examination
A Federal Aviation Administration inspector examined the airplane and found buckling of the right inboard wing. Subsequently, a post-accident landing gear extension and retraction test was conducted using a hydraulic test unit. Both normal and emergency (hand pump) extension and retraction were tested. During normal extension, the landing gear locking time was approximately 25 seconds, which exceeded the manufacturer's specified time limit. However, the test fixture used did not have flow control, which could have contributed to the longer time.
Actuator Rigging Findings
When checking the actuator rigging, it was discovered that both the left and right main landing gear actuators did not drive the main gears into a locked position. Applying slight hand pressure on the gear door in an inboard direction prevented the main landing gear from locking, as the actuator piston travel was fully bottomed out. When the pressure was removed, the weight of the gear allowed it to lock.