History of the Flight
The pilot, manager of a maintenance workshop, took off from Biarritz-Pays Basque airport bound for Biscarrosse-Parentis aerodrome, accompanied by a passenger. On approach south of the aerodrome, the pilot contacted the tower controller, who reported receiving him intermittently. Shortly thereafter, the aeroplane experienced a complete loss of electrical power.
Approximately ten minutes later, still south of the aerodrome, the pilot contacted the tower controller using a mobile phone. The controller informed him that there was no known traffic in the vicinity, the wind was calm, and the runway was free to be used at his discretion. The pilot stated he intended to use unpaved runway 09 and ended the call.
Before joining the downwind leg, the pilot set the landing gear selector to "down," but realized it would be ineffective due to the electrical failure. He then operated the emergency landing gear extension handcrank but was unable to completely extend the landing gear, while turning the long way round south of the aerodrome.
Before landing, approximately 50 m from the threshold, the pilot shut down the engine, cut off the magnetos, and just before touchdown retracted the flaps to avoid damage. The main landing gear touched the runway first. When the nose gear contacted the ground, the landing gear retracted. The propeller, windmilling, struck the ground, and the aeroplane came to a halt on the runway.
Additional Information
Aircraft Information
The aeroplane had been stored at the maintenance workshop at Biarritz-Pays Basque airport since June 2018, mostly parked outside under a tarpaulin. An annual inspection was performed in August 2018 followed by another in July 2019. At the end of 2019, the oil and oil filter were replaced, and the spark plugs were cleaned and adjusted. The workshop manager conducted a check flight on 10 January 2020, the first flight since June 2018, and flew the plane three more times before the accident flight.
The emergency landing gear extension system includes a handcrank forward and left of the pilot's seat. The flight manual procedure requires: (1) Pull the landing gear motor circuit breaker (OFF); (2) Set the landing gear selector to DOWN; (3) Push the handcrank forward to engage the drive mechanism; (4) Turn the handcrank clockwise about 50 times to fully extend the gear, indicated by a green light and aligned markings on a visual indicator.
Examination of the landing gear revealed that the nose gear extension control rods were deformed by compression, likely due to the collapse of the main landing gear on landing. It was possible to extend and lock the landing gear after about 60 turns of the handcrank, though compression deformation may have affected the turn count.
The electrical system includes an alternator switched on by the pilot using a switch and an ammeter indicating battery charge status. The pilot could not recall if he switched on the alternator after start-up and noted negative ammeter readings after take-off.
Pilot Information
The 45-year-old pilot held an LAPL(A) and had logged 575 flight hours, with 8 hours on F-HOSJ. In the preceding three months, he had logged 9 flight hours, including 5 hours on F-HOSJ. He had retractable landing gear training and 30 hours on such aircraft. He did not have the checklist or emergency procedures onboard and did not consult the flight manual.
During troubleshooting, the pilot performed 360° turns, checked circuit breakers (all pushed in), and noted the ammeter centered on zero. He switched off equipment and cycled the battery and alternator without effect. While attempting emergency gear extension, he turned the handcrank counterclockwise for three to four minutes (about twenty turns). The visual indicator showed gear extending but not reaching the locked position. He then tried turning clockwise but could not apply enough force. He resumed counterclockwise turns for about one minute (ten turns) with no change. Later, the pilot doubted whether he had correctly engaged the drive mechanism.
Several days after the accident, the pilot checked the alternator and found no anomaly. In November 2021, while repairing the aeroplane, he identified the electrical failure cause: a loose contact screw on the cable connecting the alternator to its circuit breaker on the battery charge line.
Conclusions
The scenario involved a problem on the battery charge line causing the battery to power equipment until fully discharged, leading to complete loss of electrical power. The pilot attempted manual gear extension but could not lock it, resulting in gear collapse during landing. The investigation noted contributing factors: a fault on the attachment of a cable on the electrical line, and the pilot not using the checklist or procedure during the flight.