On 21 August 2008, an Airbus A340-300 being operated by an undisclosed operator by a German-licensed flight crew on a scheduled passenger flight from Teheran to Frankfurt collided with a stationary bus with only the driver on board whilst approaching the allocated parking gate in normal daylight visibility. The No 4 engine impacted the bus roof as shown in the photograph below reproduced from the official report. None of the occupants of either the aircraft or the bus were injured.
The accident airplane and bus on the apron. Source: BFU Report 5X015-08
An investigation was carried out by the German BFU. It was found that neither the aircraft nor the passenger bus had any technical deficiencies and that the AGNIS (Azimuth Guidance for Nose-In Stand) and the associated stop device PAPA (Parallax Parking Aid) for the assigned gate, B26, was not operating at the time of the collision and that a marshaller was allocated to attend.
It was noted from the Cockpit Voice Recorder (CVR) that the flight crew had noticed the stationary bus on the road but had not assessed that the distance between it and the aircraft would be insufficient after turning into the parking gate. It was established that an abrupt braking manoeuvre initiated by the aircraft crew just before the collision had occurred as a result of the co-pilot seeing a follow-me car quickly approaching the aircraft from the front and was not because of any realisation of an impending collision with the bus. The crew had only become aware of the collision with the bus approximately one minute after the aircraft had stopped.
The applicable traffic regulations for the road involved were found to stipulate that vehicles should stop on the first stop marking when travelling east “whenever an aircraft was taxiing via taxiway G to parking position B26”. During the investigation, it became apparent that it might not be possible for a vehicle stopped at the first stop marking on the taxi area road to physically see an aircraft taxiing towards B26 due to oncoming traffic. It was therefore concluded that the bus driver in this case had no reason to stop at the first stop marking and thus provide the inbound aircraft with priority After noticing the aircraft when midway between the two stop markings, the driver brought his vehicle to a stop but it was then already in a position where a collision was inevitable, which the driver recognised.
The diagram below, taken from the official report, shows the relative positions of the aircraft and the bus at the collision and their previous tracks.
Reconstructed taxiing and driving paths. Source: BFU Report 5X015-08
It was noted that there was no airport procedure specifying the limit of aircraft movement when arriving at gate B26 and finding the AGNIS/PAPA deactivated and no marshaller in position at the head of the stand, whereas this circumstance would require an aircraft to wait off the gate.
The Investigation concluded that the immediate cause of the collision was “an insufficient distance between the passenger bus and the taxiway of the Airbus A340” and that the three “systemic causes” were as follows:
- The spatial separation between the taxi area road and the taxiway G towards parking position B26 was insufficient.
- Coming from the east, the position of the first stop line marking on the taxi area road did not allow for an unrestricted view of the parking position B26.
- The vehicle drivers coming from the east had to decide during the drive on the taxi area road whether to stop at the first or second stop line marking. They also had to take into consideration whether an aircraft was taxiing to parking position B26 or to the A-B area.
Two Safety Recommendations were made as a result if the investigation:
- The operator of the Frankfurt/Main Airport should ensure a spatial separation of the taxiing traffic and the vehicle traffic on the apron in the area of the crossing of taxiway G with the taxi guide line to position B26 by means of infrastructural measures (e. g. change of traffic routing). (No. 28/2009)
- The operator of the Frankfurt/Main airport should revise the procedure for the assignment of dispatch and parking positions published in the Aeronautical Information Publication (AIP) in chapter AD 2 EDDF 2.20, 3.3. Thereby making it clear that the AGNIS / PAPA system is a visual guidance system for taxiing and parking airplanes, and that its activation does not substitute the taxiing clearance into the parking position. (No. 29/2009)
The Investigation was completed on 5 June 2010 and the Final Report may be seen in full at SKYbrary bookshelf: BFU Report 5X015-08