What happened
On 2 September 2003, a Boeing 737-73V, registration G-EZJN, was taxiing to a stand at Edinburgh Airport for a passenger flight. The aircraft was utilizing the AGNIS (Azimuth Guidance for Nose-In Stands) and PAPA (Parallax Aircraft Parking Aid) docking guidance systems, which are designed to assist the pilot in aligning and stopping the aircraft for airbridge connection.
As the aircraft approached the designated PAPA stop position, the first officer noted that a pushback tug parked ahead was encroaching on the aircraft's path. Although the commander performed an immediate stop, a scraping sound and a slight impact were felt. A subsequent inspection revealed that the lower portion of the aircraft's radome had struck the roof of the pushback tug. The docking guidance system confirmed that the aircraft had stopped before reaching its usual stopping point.
The investigation
The investigation established that the ground crew had not anticipated the aircraft would be using the airbridge for this specific arrival, and therefore expected the aircraft to stop at ground marks located short of the standard PAPA stop position. Crucially, the pushback tug had been parked within a zone that should have been cleared of all ground equipment before the docking guidance system was activated.
Findings
- The primary cause of the impact was the presence of a pushback tug within the aircraft's path during the use of the docking guidance system.
- The tug was positioned in an area that should have been kept clear of equipment prior to the activation of the AGNIS and PAPA systems.
- There was a discrepancy in expectations regarding the aircraft's stopping position, as the crew was following guidance for an airbridge arrival while ground staff expected a stop at different ground marks.
Safety action
Following the incident, Edinburgh Airport issued a directive to reinforce existing Stand Entry Guidance procedures. This new instruction explicitly prohibits the pre-positioning of tugs in the 'stand tug lane' before an aircraft arrives, regardless of which guidance system is being utilized. Additionally, the airline implemented a new procedure: flight crews must always follow AGNIS and PAPA indications when both are illuminated. If a stop short of the standard position is required, crews must only do so under the direction of a marshaller with the AGNIS system deactivated.