What happened
On 29 January 2020, a Mooney M20F, registration F-HOSJ, was performing a cross-country flight from Biarritz-Pays Basque airport to Biscarrosse-Parentis. During the approach to the destination, the aircraft experienced a complete loss of electrical power, which also caused the radio equipment to cease functioning.
Unable to communicate via the aircraft's radio, the pilot contacted the tower using a mobile phone. After receiving clearance to use the unpaved runway, the pilot attempted to extend the landing gear. Because the electrical system had failed, the electric selector was ineffective. The pilot attempted to use the emergency manual handcrank; however, the gear was only partially extended and did not reach the locked position.
Prior to touchdown, the pilot shut down the engine and retracted the flaps to prevent damage. While the main gear made initial contact with the runway, the nose gear collapsed upon impact. The aircraft's propeller struck the ground, and the aircraft came to a halt on the runway. The aircraft sustained substantial damage.
The investigation
The investigation focused on the cause of the electrical failure and the failure of the manual gear extension. Investigators examined the aircraft's electrical system, specifically the connection between the alternator, circuit breaker, busbar, and battery.
Regarding the landing gear, the investigation noted that the nose gear extension control rods had been deformed by compression, likely due to the collapse of the main gear. While the pilot attempted to use the handcrank, the investigation found that the manual procedure requires approximately 50 clockwise turns to fully extend and lock the gear. The pilot's use of the handcrank was insufficient to achieve a locked state.
Findings
- The primary cause of the electrical failure was a loose contact screw on the electrical line connecting the alternator to its circuit breaker, which caused the battery to discharge until power was lost.
- The landing gear was only partially extended because the pilot did not follow the full emergency procedure or use a checklist during the flight.
- The pilot's attempt to use the handcrank involved insufficient turns and an incorrect sequence of movements, preventing the gear from locking in the down position.