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Statuts:Enquête Officielle
Date:samedi 28 juillet 2012
Type/Sous-type:Silhouette image of generic BE20 model; specific model in this crash may look slightly different
Beechcraft B200 Super King Air
Compagnie:ASL - Air Service Liege
Immatriculation: OO-LET
Numéro de série: BB-1473
Année de Fabrication: 1993
Moteurs: 2 Pratt & Whitney Canada PT6A-42
Equipage:victimes: 0 / à bord: 4
Passagers:victimes: 0 / à bord: 0
Total:victimes: 0 / à bord: 4
Dégats de l'appareil: Substantiels
Conséquences: Repaired
Lieu de l'accident:Cambridge Airport (CBG) (   Royaume Uni)
Phase de vol: A l'atterrissage (LDG)
Aéroport de départ:Cambridge Airport (CBG/EGSC), Royaume Uni
Aéroport de destination:Cambridge Airport (CBG/EGSC), Royaume Uni
A Beechcraft B200 Super King Air, OO-LET, was substantially damaged when its landing gear collapsed while landing at the Cambridge Airport (CBG), England. All four other crew members on board were not injured. Visual meteorological conditions prevailed for the local flight which departed Cambridge Airfield.

The airplane had been operating as a communications relay for the London Olympics and was returning to Cambridge. While descending to FL180 the pilots experienced a progressive failure of all of the electrical equipment, with the exception of the left instrument panel Electronic Flight Information System display. This remained powered by a backup power supply. However, as the display was giving erroneous information, the pilots decided to turn it off. The abnormal checklist did not contain a procedure for a total electrical failure, so the Pilot Flying turned off both generators and the battery switch before selecting them on again in an attempt to restore the electrical supply. He also selected the alternate inverter and the PNF recycled the cabin power supply switches. The PF stated that he did not attempt to select the generators to RESET. The left instrument panel had functioning ASI and vertical speed indicator (VSI) instruments; the right panel had a working attitude indicator (which was vacuum-driven), ASI and altimeter indications. The engine rpm gauges and standby compass remained operational.

Mindful of avoiding a security alert during the Olympic Games, the crew carried out the pre-briefed communications failure procedure and turned the aircraft onto a northerly heading to clear the London TMA, before proceeding towards a designated holding area. As the aircraft approached the Wisbech area, the commander recognised some land features. The aircraft descended to 5,000 ft from where the crew were able to identify additional landmarks and navigate visually towards Cambridge Airport. By this time the aircraft had been flying for some time without electrical power and therefore without operating fuel gauges, and the crew were concerned about the aircraft's remaining endurance.
When they arrived near the airport, they circled it to alert ATC to their presence and then carried out the Landing Gear Manual Extension procedure. When carrying out the procedure the pilots operated the landing gear control handle, but omitted to pull the landing gear relay circuit breaker. The PF operated the alternate extension handle to extend the landing gear. Initially, the handle was easy to operate and the pilots could see the main landing gear as it started to extend. The PF stated that he stopped operating the handle when heavy resistance was felt, in order not to damage the system. The PF also stated that the PNF had mentioned to him not to force the handle. The PF asked the PNF to check the resistance of the handle, which he did. The PF continued to operate the handle whilst they positioned the aircraft downwind and onto base leg, but stopped pumping each time he felt heavy resistance.
The PF carried out a flapless approach and the aircraft touched down gently at approximately 100 kt. Almost immediately after touchdown, the landing gear started to collapse. The PNF immediately operated the fuel condition levers which shut down the engines and feathered the propellers. The aircraft settled onto the centreline luggage pod and the main undercarriage doors. It came to rest after a total ground run of approximately 400 m, during which it yawed slightly to the right. The PF was able to counteract the yaw with rudder sufficiently to prevent the aircraft from leaving the paved surface.
After it had come to a halt, the commander ordered the technicians to evacuate. The pilots then completed the shutdown checklist before also vacating the aircraft. The flight time from the electrical failure until the landing was approximately 37 minutes.

Probable Cause:

CONCLUSIONS: "No cause for the electrical failure could be determined and no fault was found with the landing gear system. It is possible that the gear collapsed on landing because the crew ceased operating the alternate extension handle before the landing gear was fully extended. The electrical failure meant that the crew had no indication of the landing gear position and therefore could not confirm that the gear was down and locked prior to landing."

Accident investigation:
Investigating agency: AAIB
Status: Investigation completed
Duration: 257 days (9 months)
Accident number: AAIB Bulletin: 4/2013
Download report: Final report
Language: English



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