What happened
On 17 September 2003, a Jetstream 31, registration G-EEST, was performing a scheduled passenger flight to Wick Airport, Scotland. During the landing on Runway 31, the aircraft crossed the threshold at approximately 130 kt, which was significantly higher than the recommended approach speed for the prevailing conditions.
As the aircraft approached the runway, the co-pilot reduced power, which triggered the beta warning horn, indicating the power levers had been moved below the flight idle position while the aircraft was still airborne. The aircraft floated above the surface before making an initial touchdown. This was followed by a series of bounces, the second of which was particularly violent, recording a vertical acceleration of 5.6g. This heavy impact caused the aircraft to strike the runway with its right propeller and resulted in substantial structural damage, including a cracked wing spar and buckling of the fuselage and wing skins. There were no fatalities and no injuries to the three crew members or four passengers on board.
The investigation
The AAIB investigation focused on the sequence of events during the landing flare and the mechanical state of the aircraft. Investigators analyzed the Cockpit Voice Recorder (CVR) and Flight Data Recorder (FDR), noting that while the FDR provided airspeed and altitude, it lacked critical parameters such as pitch and roll attitude.
Technical examinations of G-EEST revealed no evidence of mechanical failure or technical faults prior to the incident. The investigation looked into the power lever microswitches and the beta mode operation of the McCauley propellers. Simulator testing by the manufacturer suggested that the erratic flight path described by the crew would require significant and simultaneous control inputs. The investigation also examined the crew's control of the aircraft, noting that both the commander and co-pilot appeared to be making conflicting inputs on the flight controls during the bouncing sequence.
Findings
- The aircraft approached the threshold at a speed roughly 22 kt faster than the appropriate speed for the specific wind conditions.
- The primary cause of the erratic landing sequence was the combined, conflicting control inputs made by the commander and the co-pilot during the landing phase.
- One or both power levers were moved below the flight idle position prior to the first touchdown, triggering the beta warning.
- The aircraft entered a high-drag, low-lift configuration (beta mode) after the first bounce, which contributed to the severity of the subsequent impacts.
- The weather conditions, including wind and turbulence, were within the aircraft's operational limitations.