What happened
On 14 December 2007, an AS332L2 Super Puma, registration G-REDN, was performing a ground taxi at Aberdeen Airport, Scotland. Following the landing of a commercial passenger flight, the crew taxied the aircraft from Runway 23 to Spot 5 to disembark passengers. After passengers had left, the commander took control of the aircraft to taxi to a nearby location, Spot 3, for shutdown.
While taxiing, the aircraft initially turned to the right without issue. However, when the crew attempted a left-hand turn, the helicopter failed to respond to steering inputs. The crew discovered that the nosewheel locking pin had become engaged. In an attempt to release the pin by reducing the weight on the nosewheel, the commander increased the collective pitch. This action caused the aircraft to become unstable, resulting in the helicopter lifting into a hover with a significant roll and pitch. The aircraft eventually stabilized and was able to hover-taxi to Spot 3, where it landed safely without any injuries to the crew or damage to the aircraft.
The investigation
Investigators examined flight data from the aircraft’s monitoring programs and analyzed CCTV footage of the apron. The investigation established that the nosewheel locking pin engages when the lever is raised and rotated, and it prevents the nosewheel from rotating.
Analysis of the flight data showed that during the left turn, the pilot applied approximately 50% right yaw pedal before reversing to almost full left pedal. The CCTV footage confirmed that the aircraft skidded to the right while the collective power was applied. The investigation also looked into the possibility of the pin engaging due to the nosewheel being offset; it was determined that if the nosewheel had been offset, the pin would not have been able to enter the hole. The investigation also considered the crew's duty patterns, noting that both pilots were on consecutive early duty starts.
Findings
- The most likely cause of the incident was that the nosewheel locking pin lever was accidentally placed in the locked position instead of the parking brake position after parking at Spot 5.
- The application of left yaw pedal while the nosewheel was locked, combined with the increase in collective pitch, created a rolling moment that caused the aircraft to lift.
- The error in setting the lever may have gone unnoticed because the pilot flying changed during the taxi, potentially leading to a lapse in checklist discipline.
- Fatigue may have been a contributing factor due to the crew's recent pattern of early duty starts.