What happened
On May 14, 2008, at 15:56 local time, a serious runway incursion occurred at Zweibrücken aerodrome involving an Airbus A319-112 and a C-160 Transall. The Airbus A319, operating an IFR flight to Berlin-Schönefeld with 132 passengers and five crew members, was cleared to taxi via routes G and C to runway 03. During its backtrack on runway 03, the aircraft was prepared for takeoff.
Simultaneously, a C-160 Transall, performing VFR parachute jumps, requested departure from runway 21. Although the standard operating direction for the day was runway 03, the use of runway 21 had been previously arranged via telephone between the military operator and the tower. During taxiing, the air traffic controller issued a taxi clearance to the Transall that included a verbal slip, initially mentioning runway 03 before correcting to runway 21. The Transall crew interpreted this instruction as permission to line up on the runway.
As the Airbus A319 commenced its takeoff roll, the controller realized the Transall had entered runway 21, which was the opposite end of the active runway. The controller issued an immediate instruction to break up the movement. The Airbus pilot reported that because the aircraft was already above V1 speed, an aborted takeoff was no longer possible. The Airbus subsequently flew over the C-100 Transall at a vertical separation of approximately 400 ft. No injuries or damage to either aircraft were reported.
The investigation
The BFU investigation focused on why the error in taxi instructions occurred and why it was not detected earlier. The investigation examined radio communications, taxiway layouts, and the operational procedures in place at the time. The BFU noted that the investigation of human performance was limited because the Cockpit Voice Recorders were unavailable due to a delay in reporting the incident.
Findings
- The primary cause of the incursion was the C-160 Transall crew misinterpreting the taxi clearance, leading them to line up on runway 21 instead of holding at Alpha.
- The use of a non-standard departure direction (runway 21 instead of 03) contributed to the risk.
- The air traffic controller's use of non-standard phraseology and a verbal slip during the taxi clearance contributed to the confusion.
- The read-back/hear-back process failed to identify the errors in the taxi instructions.
- The physical layout of the airfield, specifically the elevation changes at the runway ends, prevented the crews and the controller from visually detecting the conflicting aircraft movements earlier.
- The C-160 Transall crew did not utilize Crew Resource Management (CRM) effectively to identify the error in the clearance.