What happened
On 27 March 2008, an EADS Socata TBM 700C1, registration N700GY, was conducting a private flight from Biggin Hill to Alderney Airport. During the flight, the pilot selected the landing gear to the up position, but the green nose gear light failed to extinguish, and a red warning light remained illuminated on the control panel.
After several unsuccessful attempts to retract the gear, the pilot chose to continue the flight with the gear down, noting the airspeed limitations specified in the Pilot’s Operating Handbook (POPN). The pilot observed three green lights but noted the continuous red light. Upon landing at Alderney, the aircraft reached approximately 40 kt during the rollout when the nose gear leg suddenly collapsed. This caused the propeller and the nose of the aircraft to strike the paved runway, leading to major damage to the engine, propeller, and aircraft nose. The aircraft subsequently veered off the runway and came to a stop on a taxiway.
The investigation
The AAIB examined the nose gear actuator, which was removed and tested at the manufacturer's facility. During functional testing on a rig, investigators discovered an anomaly where the actuator provided indications that the nose gear was locked in both the up and down positions simultaneously. This dual indication could explain the continuous red warning light observed by the pilot. While faint witness marks were found inside the mechanism, no specific contamination was identified.
Findings
- The pilot interpreted the three green lights as an indication that all gear were locked down, failing to recognize that the red warning light takes precedence and signifies an unlocked gear.
- The red warning light remained illuminated because the nose gear was not properly locked.
- The nose gear actuator exhibited an anomaly during testing, sending simultaneous up and down lock signals to the control unit.
- The Pilot’s Operating Handbook lacked sufficient clarity regarding the significance of a red warning light when displayed alongside three green lights.
Safety action
- A safety recommendation was made to EADS Socata to amend the TBM 700 Pilot’s Operating Handbook to clearly state that manual extension of the landing gear is required if a continuous red light is displayed, even if the green lights are illuminated.