What happened
On January 19, 2019, a Piper PA-30 Twin Comanche, registration EC-BBX, departed from Requena airfield for a local VFR flight. During the initial climb, the pilot attempted to retract the landing gear, but the 30A circuit breaker tripped. After resetting the breaker and attempting the retraction again, the breaker tripped a second time, and the pilot noticed a burning smell.
During the return to the airfield, the aircraft experienced a total loss of electrical power. Although power briefly returned, the pilot attempted to extend the landing gear, which triggered another permanent electrical failure. Believing the gear was locked down based on a visual inspection of the manual extension linkage, the pilot proceeded to land on runway 30. Upon touchdown, the landing gear collapsed, causing the aircraft to slide on its fuselage. The aircraft veered left and came to a stop in the area between the runway and the parallel taxiway. The two occupants were uninjured, though the aircraft sustained significant damage.
The investigation
The investigation focused on the failure of the landing gear extension/retraction system and the electrical power interruption. Investigators examined the landing gear motor and found evidence of severe overheating, including a discolored rotor and melted metal traces. Tests conducted after the accident showed that the motor was drawing excessive current, causing the circuit breaker to trip.
Regarding the electrical failure, investigators determined that the aircraft's alternators were not providing power, forcing the aircraft to rely solely on the battery. The investigation noted that the installed battery had a lower capacity (23 Ah) than the required 35 Ah, which accelerated the depletion of power. Furthermore, the investigation analyzed the pilot's decision-making process regarding the gear position and the failure to utilize the manual extension mechanism.
Findings
- The primary cause of the accident was landing with the landing gear partially deployed.
- The landing gear motor was subject to excessive mechanical resistance, leading to high current draw and overheating.
- The pilot performed an inadequate situational assessment, which resulted in the failure to execute the manual landing gear extension procedure.
- The aircraft's alternators were either not connected or were inadvertently disconnected prior to takeoff, leading to the exhaustion of the battery.
- The installed battery was undersized for the aircraft's requirements, reducing the available emergency power duration.