What happened
On 2 December 2005, a Bombardier DHC8-402 Dash 8, registration G-JEDW, was performing a scheduled passenger flight at Birmingham International Airport. The flight was the fourth sector of the day, carrying 47 passengers and 4 crew members. Because the aircraft's auxiliary power unit was unserviceable, one engine had to be started while the aircraft was still on the stand.
Following an uneventful engine start and pushback, the flight crew began their pre-taxi checks. During this process, the co-pilot noticed an ice detection warning and another unidentified warning on the Master Warning Panel. The commander, distracted by these warnings, signaled for the co-pilot to remain quiet and did not immediately address the ground crew's communications.
After the pushback was completed, the commander signaled that the ground crew was "clear to disconnect." However, the parking brake had not been applied. As the crew moved the propeller condition levers to the MAX position, residual thrust from the engines caused the aircraft to move forward. The aircraft subsequently struck the disconnected tow bar, resulting in damage to the tow bar and the aircraft's nose wheels.
The investigation
The AAIB investigation examined the sequence of events, the ground crew's actions, and the cockpit communications. The investigation noted that the tug driver had left a small gap between the wheel chock and the nose wheel to facilitate easier removal. Once the chocks were removed and the engines were accelerated, the residual thrust was sufficient to propel the aircraft into the tow bar.
Because the Cockpit Voice Recorder (CVR) was not electrically isolated immediately following the event, the investigators were unable to review the specific dialogue between the pilots and the ground coordinator during the pushback. This prevented a definitive determination of whether the commander's instruction was misinterpreted by the ground crew.
Findings
- The primary cause of the collision was the failure to apply the parking brake during the pushback sequence.
- A breakdown in Crew Resource Management (CRM) occurred when the commander was distracted by warning lights and failed to properly communicate with the co-pilot or the ground crew.
- There was a potential misinterpretation of the "clear to disconnect" instruction by the ground coordinator, who may have believed the parking brake was set.
- The aircraft sustained damage to both nose tyres and the wheel rims, necessitating the replacement of both nose wheels.