What happened
On March 3, 2021, a KLM Boeing 737-800, registration PH-BCD, was preparing for a commercial flight from Lisbon (LPPT) to Amsterdam (EHAM). During the pre-flight preparations, the flight crew utilized the LINTOP (Lido Integrated Takeoff Performance) tool to calculate takeoff data. The crew initially attempted to select the S1 intersection of runway 21; however, because this intersection is not a valid takeoff point, the system returned an error message.
In an attempt to rectify this, the crew re-entered the data but omitted the digit "1," effectively requesting data for intersection S. This error led the system to provide performance parameters for position S, which actually corresponds to intersection S4. The crew subsequently re-entered the data again to account for a change in the aircraft's takeoff mass, but they did not correct the takeoff point. Consequently, the flight management system (FMS) was programmed with takeoff speeds and temperatures corresponding to the full length of runway 21, despite the aircraft taxiing to intersection U5.
During the takeoff roll, the aircraft's main landing gear lifted off with only approximately 284 meters of runway remaining. The aircraft crossed the runway threshold at an altitude between 45ft and 70ft. The crew did not notice any performance anomalies or issues during the takeoff roll, and the flight proceeded to Amsterdam without further incident.
The investigation
The GPIAAF conducted an evaluation of the incident after being notified in April 2021. While the agency decided not to conduct a full formal investigation under Annex 13—given the actions already taken by the operator and the availability of data from similar previous events—it produced this report to disseminate safety-relevant information. The investigation focused on the discrepancy between the planned takeoff performance and the actual runway available, as well as the potential risks posed by the use of incorrect intersection nomenclature.
Findings
- The crew entered incorrect takeoff performance parameters by omitting a digit in the intersection designation, causing the system to use data for intersection S4 instead of the intended point.
- The takeoff was performed using the U5 intersection with parameters for S4, resulting in a Take-Off Run Available (TORA) that was 1,395 meters shorter than planned.
- This reduction in available runway meant that the aircraft's speed and altitude at the end of the runway might not have been sufficient for a safe engine failure (One Engine Inoperative) scenario.
- The use of the U5 intersection with S4 parameters created an unacceptable risk in the event of an engine failure during the critical takeoff phase.
- The crew did not realize the error during the flight, and the event was only identified six weeks later through flight data monitoring (FDM).
- The investigation noted a history of confusion regarding the nomenclature of taxiways and intersections (such as S1 and S4) at Lisbon Airport, which has been a factor in previous incidents involving other aircraft.
Safety action
Following the incident, the operator implemented several corrective measures, including:
- Issuing a company NOTAM to flight crews operating at Lisbon Airport to highlight relevant aerodrome data.
- Updating the LINTOP performance database for Lisbon to ensure that a request for position "S" no longer returns valid data.
- Introducing a new takeoff performance tool that includes a runway synopsis to clearly display the selected runway and intersection.
- Publishing an incident report via the Flight Operations Safety News application to raise crew awareness.