What happened
On the night of January 12, 2006, a runway incursion occurred at Frankfurt Airport involving a cargo Boeing 747-20 and an Airbus A320-214. The Boeing 747-200B, arriving from Beijing, had landed on runway 07R and was taxiing toward its parking position. During the taxi process, the crew received instructions from the Frankfurt Tower to taxi via taxiway Golf and hold short of runway 07L. During the readback, the crew mistakenly indicated they intended to cross runway 07L. The controller, interpreting the crew's response as a confirmation of the hold-short instruction, did not correct the error and subsequently cleared an arriving Airbus A320-214 from Dublin for landing on runway 07L.
As the Airbus A320-214 was rolling out on runway 07L, the crew observed the Boeing 747-200B crossing the active runway. Radar data indicated that the distance between the two aircraft was approximately 800 meters at the moment of the crossing. The crew of the Airbus responded by applying heavy braking, successfully reducing the aircraft to a very low speed and avoiding a collision. No injuries or damage to either aircraft were reported.
The investigation
The BFU investigation focused on the communication exchange between the tower controller and the Boeing crew, as well as the functionality of ground surveillance systems. The investigation examined the cockpit voice recordings and radio transcripts, noting that the communication was conducted in English. The BFU also reviewed the status of the airport's surface movement radar and its Runway Incursion Monitoring (RIM) function.
Findings
- Readback/Hear-back Error: The primary cause was a communication breakdown. The Boeing crew misinterpreted the controller's repetition of the hold-short instruction as permission to cross the runway. The controller, expecting a confirmation of the hold-short instruction, misperceived the crew's incorrect readback as a valid confirmation.
- Surveillance System Deactivation: The Runway Incursion Monitoring (RIM) function of the airport's radar was deactivated at the time of the event. This was due to a standing operational order intended to prevent frequent false alarms.
- Visibility and Positioning: While the weather was IMC (Instrument Meteorological Conditions), the visibility was sufficient for the aircraft to be seen. However, the position of the crossing Boeing 747 was difficult for the Airbus crew to see due to the angle of the taxiway intersection and the aircraft's orientation.
- Operational Factors: The heavy weight of the Boeing 747-200B compared to the Airbus A320-214 meant the larger aircraft had a longer required rollout, which contributed to the timing of the crossing in a critical area of the runway.
Safety action
- Recommendation 03/2007: The BFU issued a recommendation to Deutsche Flugsicherung GmbH (DFS) to ensure that airport surface monitoring systems equipped with conflict detection and alerting functions are maintained to provide reliable indications.