What happened
On 5 February 2012, an Airbus A340-313, registration 4R-ADG, was preparing for a commercial passenger flight from London Heathrow Airport to Colombo, Sri Lanka. During the pre-flight phase, the flight crew was requested by Air Traffic Control to depart from the SB7 intersection rather than the full length of Runway 09R.
Because a specific regulated takeoff weight chart for the SB7 intersection was unavailable, the commander performed a performance calculation using a chart from a different runway of comparable length. This calculation did not account for specific obstacles present on the active runway. The crew opted to use a flexible thrust takeoff, entering the calculated speeds and flexible temperature directly into the Multi-function Control and Display Unit (M2CDU) without recording the specific values used.
As the aircraft became airborne, an aerodrome controller and an observer noted that the aircraft lifted off much closer to the end of the runway than anticipated and appeared lower than normal. The flight continued to Colombo without further incident, and there were no injuries to the 15 crew members or 245 passengers on board.
The investigation
The AAIB investigation focused on the validity of the takeoff performance data. The investigation was hampered by the fact that the takeoff data entered into the MCDU was not recorded by the flight data recorder or the quick access recorder. Furthermore, a delay in notifying the AAIB meant that the original flight data had been overwritten.
While the crew could not recall the exact speeds or flexible temperature used, the investigation utilized ground movement radar to determine that the aircraft lifted off at approximately 2,650 metres from the intersection. Analysis of the runway configuration and the aircraft's weight and configuration indicated that the required takeoff run was 2,268 metres, while the available distance was 2,854 metres.
Findings
- The aircraft departed from an intersection for which no specific performance data was available on board.
- The crew performed the performance calculation using a chart for a different runway, which failed to consider obstacles relevant to the runway in use.
- The takeoff was conducted using flexible thrust, and while the thrust was likely sufficient to meet performance requirements, the method of calculation was flawed.
- The airline's procedures at the time did not provide guidance for pilots when standard takeoff charts were unavailable.
Safety action
Following the incident, the operator issued new instructions stating that takeoffs must not proceed without relevant takeoff data. Pilots are now required to use a customized regulated takeoff weight chart from the dispatch centre or use quick reference tables if accurate obstacle data is available.