What happened
On 15 January 2006, a Boeing 737-33A, registration G-TOYE, was undergoing pushback from its parking stand at Birmingham Airport. During the maneuver, the aircraft was being moved forward by a tug to align with the taxiway. While the flight crew were in the middle of starting the number one engine and preparing to start the number two engine, a member of the ground crew used the intercom to request that the crew apply the parking brakes.
The commander responded to the request by instructing the ground crew to wait one minute while the engine start sequence continued. Shortly after this exchange, the commander realized the aircraft had begun moving without the brakes applied. The aircraft rolled forward and the radome struck the front of the tug, resulting in a dent to the aircraft structure. There were no injuries to the 5 crew members or 103 passengers on board.
The investigation
The investigation focused on the communication between the flight crew and the ground personnel. It was established that the aircraft moved because the tow bar had been disconnected before the parking brakes were engaged. The investigation examined the interaction via the intercom to determine why the aircraft was allowed to move without braking.
Findings
- The primary cause of the incident was the disconnection of the tow bar without the aircraft brakes being set to park.
- The commander's instruction to the ground crew to wait may have been misheard by the ground crewman, leading to the premature disconnection of the tow bar while the aircraft was in motion.