What happened
On 25 January 2002, a Boeing 737-5Q8, registration G-BVZH, was taxiing to Stand C28 at London Heathrow Airport following a revenue flight from Europe. The operation took place during night hours under severe weather conditions, characterized by heavy rain and strong southerly winds. Due to the driving rain, visibility was significantly obscured even with windscreen wipers in operation.
To reach the designated parking position, the aircraft was required to execute a turn of approximately 110 degrees off the taxiway. The pilot struggled to identify the stand centerline because the yellow pavement markings were difficult to discern in the dark, wet environment. While attempting to align the aircraft, the pilot became distracted by the difficulty of locating the line, leading to an error in determining the stopping point. Upon realizing the aircraft's position was incorrect, the pilot applied the brakes to stop the aircraft from a speed of 1 kt. However, the nosewheel had already overshot the correct position for a 737 and had instead stopped on the marking intended for a Boeing 757. This misalignment caused the upper portion of the left engine cowling to strike the underside of the air-bridge, resulting in damage to the left engine cowling. There were no injuries to the 6 crew members or 7 and 70 passengers on board.
The investigation
The investigation examined the visibility of the ground markings and the functionality of the Parallax Aircraft Parking Aid (PAPA) at the stand. While the AGNIS/PAPA system was found to be operating correctly, investigators noted that the illumination for the aircraft type identification labels was compromised. Green mould and dirt had accumulated on the light cover, reducing the clarity of the labels. Furthermore, the pilot noted that the white fluorescent alignment light was excessively bright, which, combined with the similarity between the B737 and B757 labels, increased the risk of error.
Additionally, the investigation reviewed the operator's aerodrome ramp charts. The charts indicated a 90-degree turn for nose-in parking, whereas the actual maneuver required a much sharper angle. The physical condition of the yellow taxiway markings was also found to be worn.
Findings
- The primary cause of the incident was the misidentification of the aircraft parking position due to the pilot's difficulty in locating the stand centerline in poor visibility.
- Severe weather, including heavy rain and darkness, significantly degraded the visibility of the yellow pavement markings.
- The lighting for the aircraft type identification labels on the PAPA system was obscured by green mould and dirt.
- The similarity between the B737 and B757 labels on the parking aid increased the likelihood of confusion under sub-optimal lighting.
- The aerodrome ramp charts provided an inaccurate representation of the required turn angle for the stand.
- The yellow markings on the taxiway were in a worn condition.