History of the Flight
On 21 August 2009 at 1430 UTC, a Cessna Citation Mustang (PH-TXI) was on a training flight at Cambridge Airport, conducting an approach to Runway 23. The co-pilot was flying, with flaps selected to takeoff/approach instead of landing. Weather conditions included wind from 220° at 12 kt, visibility over 10 km, few clouds at 4,000 ft, and temperature 18°C.
During the downwind leg, as the co-pilot reduced power and the aircraft decelerated through 130 kt, the landing gear aural warning was triggered because the thrust was below approximately 85% N2 and the landing gear was up. The commander cancelled the warning immediately. The co-pilot asked for the approach checklist; the commander executed it from memory rather than using the standard 'challenge and response' technique. This checklist does not prompt for landing gear extension.
On final approach, the co-pilot experienced difficulty reducing speed to VREF, attributing it to reduced drag from the flap setting. He recalled the landing gear warning sounding again during final approach and being cancelled, though the commander believed the system had not reset.
During the flare, the co-pilot heard a grinding sound from the rear of the aircraft. He applied power and raised the nose to remain airborne. The commander took control, lowered the landing gear while maintaining about 95 kt at an estimated height of 10 ft, and initiated a go-around. The aircraft then positioned for a visual inspection by the tower controller and landed without further incident.
Landing Gear Warning System
The aircraft's landing gear aural warning system triggers when the IAS falls below 130 kt with any gear not locked down and thrust below approximately 85% N2. Pressing the horn silence button on the landing gear control panel silences the warning but does not reset the system. The system resets when thrust levers are advanced above approximately 70% N2.
Witness Information
A witness in an airport building with a clear view of the touchdown point observed the aircraft flare with the landing gear retracted. The tail appeared to contact the runway, producing a puff of white smoke. The witness then saw the aircraft climb and the gear extend.
Engineering Inspection
Post-incident inspection confirmed the landing gear warning system was serviceable. The flaps were found stuck in the takeoff/approach position. The warning system operated correctly in achievable configurations.
Assessment
The landing gear was not selected down while the aircraft was on the downwind leg. The landing checklist was not completed in the usual 'challenge and response' manner, which meant opportunities were lost to highlight the omission. The commander stated he had expected the warning and cancelled it immediately on the downwind leg. It was not possible to determine with certainty whether the warning system had reset prior to the final approach.