What happened
On 1 August 2001, a Boeing 737-4Y0, registration G-OBMM, arrived at London Heathrow Airport from Edinburgh on a scheduled passenger flight. After landing on Runway 09L, the aircraft taxied toward Stand D58L with the number one engine shut down, following standard company protocols.
As the aircraft approached the stand, the pilot observed a marshaller's vehicle positioned in the center of the parking area. The marshaller moved the vehicle to the top of the stand and took up a position at the centerline. The pilot signaled his awareness of the marshaller using the taxi light, and the marshaller subsequently used bat signals to direct the aircraft to proceed straight ahead.
As the cockpit passed the stand centerline, the pilot anticipated a signal to turn right into the stand; however, the marshaller continued to signal for the aircraft to maintain a straight course. Consequently, the pilot initiated a right turn without specific guidance. During this maneuver, the pilot noted two unattended catering vehicles parked to the left of the stand, one of which had its front wheels positioned outside the stand markings while the rear wheels encroached approximately six inches onto the stand area.
While attempting to navigate the turn, the pilot looked out of the left window to monitor the clearance between the port wingtip and the catering vehicle. The pilot found it difficult to accurately judge the distance due to visual distortion caused by the cockpit window. During the final stages of the taxi, the pilot felt a vibration and heard a noise suggesting the port wingtip had struck the side of the vehicle. The pilot immediately halted the aircraft, shut down the remaining engine, and instructed the 85 passengers to remain seated while the crew managed the situation.
The investigation
The investigation established that the contact occurred with a vehicle that was partially encroaching on the stand area. The crew and a company engineer present at the scene assisted in managing the disembarkation of passengers via the aircraft's integral stairs. The investigation focused on the interaction between the flight crew and the ground marshaller, as well as the visibility challenges faced by the pilot during the maneuver.
Findings
- The primary cause of the incident was the pilot's over-reliance on the marshaller's signals to maneuver the aircraft.
- The marshaller failed to provide the necessary signals to direct the aircraft into the stand.
- The pilot's attention was diverted by the difficulty of judging wingtip clearance through the distorting cockpit window.
- The pilot failed to properly monitor the track of the landing gear relative to the stand centerline.
- A catering vehicle was parked with its rear wheels encroaching onto the stand area.