What happened
On October 6, 2014, an Airbus A320-214, registration HB-IOP, was preparing for a flight from Basel-Mulhouse (LFSB) to Djerba, Tunisia. While the crew initially intended to depart from runway 33, they later decided to use runway 15 due to air traffic.
During the taxi phase, the crew made a rapid decision to perform an intersection takeoff from taxiway GOLF to save time. This change reduced the available runway length to 2370 meters. However, the crew proceeded to takeoff without stopping at the new position, utilizing engine thrust settings that had been calculated for the much longer full runway length of 3900 meters.
As the aircraft reached the end of the takeoff roll, the captain realized the engine thrust was insufficient. To prevent an overrun, the captain increased the thrust to the maximum available and rotated the aircraft at 150 knots. The aircraft successfully climbed and continued the flight to its destination without further incident or damage.
The investigation
SUST examined the crew's decision-making process and the technical performance of the aircraft. The investigation focused on why the discrepancy between the required thrust for the shorter runway and the applied thrust went undetected. Investigators reviewed the airline's standard operating procedures, specifically looking at the "silent" verification methods used during taxiing. The investigation also looked into the use of Electronic Flight Bags (EFBs) for performance calculations and the crew's awareness of recently implemented safety checks.
Findings
- The primary cause of the incident was that the aircraft did not achieve the required takeoff performance because the crew performed an intersection takeoff using thrust settings calculated for the full runway length.
- The decision to utilize the intersection takeoff was made within a very short timeframe.
- Existing company procedures required essential checks to be performed silently, which prevented a closed-loop verification process between the two pilots.
- A recently implemented safety feature, a "caution box" designed to verify Flight Management Guidance System (FMGS) data during lineup, was ineffective because the crew was unaware of its existence.