What happened
On 30 March 2008, a Cessna Citation 500, registration VP-BGE, departed Biggin Hill for a private flight to Pau, France. Shortly after takeoff, the flightcrew experienced significant engine vibration and initiated an immediate return to the departure airfield. During the downwind leg for Runway 21, the aircraft began a rapid descent. The crew reported a major power loss just before the aircraft struck the side of a residential building. The impact resulted in an intense fire. While the flightcrew and three passengers survived the initial impact, the accident was ultimately not survivable.
The investigation
The AAIB examined the wreckage and the mechanical condition of both engines. Investigators found that the aircraft was structurally intact at the moment of impact, with the landing gear retracted and flaps set near the takeoff/approach position. The investigation focused on the source of the reported vibration and the possibility of an engine shutdown. Because the aircraft was not equipped with a flight data recorder or a cockpit voice recorder, certain critical details regarding the sequence of cockpit actions were unavailable. The investigation also looked into the integrity of the engine fuel shut-off levers and the condition of the air cycle machine.
Findings
- The investigation identified that a bearing failure within the air cycle machine was the primary source of the vibration that prompted the crew to return to the airport.
- A missing rivet head on the left engine fuel shut-off lever may have caused the engine to shut down inadvertently.
- Approximately 70 seconds before the aircraft hit the house, neither engine was producing thrust.
- The crew attempted to relight the engines, but the attempt to restart the second engine before the first had reached idle speed likely prevented sufficient thrust from developing to stop the descent.
- There was no evidence of compressor stalling or surging prior to the event.
- The aircraft's rudder trim was positioned in the full nose-right position at the time of impact.
Safety action
Following the investigation, three safety recommendations were issued:
- A recommendation for the FAA to require Cessna Aircraft Inc to implement scheduled inspections of the throttle quadrant assembly to check the integrity of the riveted joints on the fuel shut-off levers.
- A recommendation for the FAA to amend the two-engine emergency restart checklist to emphasize restarting engines one at a time.
- A recommendation for the ICAO Flight Recorder Panel to adopt requirements for installing flight recorders on turbine-engine aircraft with a maximum takeoff mass of 5,700 kg or less.