What happened
On 3 October 2006, a British Aerospace Jetstream 3202, registration G-BUVC, was performing a scheduled flight from Aberdeen to Wick Airport in Scotland. During the final stages of the approach to Runway 31, the crew configured the aircraft for landing, selecting the landing gear to the 'down' position.
As the aircraft approached the runway, the commander, acting as the pilot flying, initiated a flare for touchdown. However, as the aircraft continued to descend, the pilot realized the landing gear had failed to extend. The pilot immediately executed a go-around. During this maneuver, the underside of the fuselage and the tips of the right propeller struck the runway surface. Following the incident, the crew cycled the landing gear, which appeared to function normally, and diverted the aircraft back to Aberdeen, where it landed safely.
The investigation
The AAIB investigation focused on why the landing gear failed to deploy despite the selector being set to 'down'. Investigators examined the landing gear selector switch and discovered that mechanical wear and electrical arcing had occurred within the switch. This process created a buildup of cupric oxide on one of the switch poles. This substance acted as an electrical insulator, preventing the current required to energize the gear extension circuit from flowing.
Crucially, the investigation found that while the gear failed to extend, the three green indicator lights—which operate on an independent circuit—remained functional. However, the crew did not visually verify these lights prior to touchdown. Furthermore, the investigation determined that the failure of the switch also inhibited the audible warning systems, including the warning horn and the Terrain Awareness Warning System (TAWS), meaning the crew received no auditory alert that the gear was retracted.
Findings
- The primary cause of the gear extension failure was mechanical wear and arcing in the gear selection switch, which left a layer of cupric oxide acting as an insulator.
- The flight crew failed to identify that the landing gear was not locked in the down position because they did not visually check the green indicator lights.
- The crew received no audible alerts due to the simultaneous failure of the warning systems caused by the faulty selector switch.
- The aircraft's standard operating procedures at the time did not require the pilot flying to cross-check the gear position, a deficiency that has since been addressed.