On 5 February 2012, an Airbus A340-300 (4R-ADG) being operated by SriLankan Airlines on a scheduled passenger flight from London Heathrow to Colombo, Sri Lanka and operated with an augmented flight crew was observed to become airborne much later than usual after accepting take off clearance from an intermediate point on the departure runway. The takeoff, carried out in daylight and with normal ground visibility, and the subsequent climb out were completed without actual incident but there was sufficient concern about operational safety to prompt an Investigation of the circumstances.
A Field Investigation was carried out by the UK AAIB. There was a delay in the reporting of the event and, as a result of this, Flight Data Recorder (FDR) data had been overwritten and when the relevant OQAR disk obtained from the Operator was examined, it was found to be faulty and contained no data. However, ground radar recordings showed that the aircraft had become airborne 2650 metres +/- 50 metres from the start of the take off roll compared to a Takeoff Run Available (TORA) from that position of 2854 metres. The Investigation also calculated that, based upon the conditions at the time, the required take off run for a reduced thrust take off was 2268 metres using the maximum assumed temperature available of 38º C.
It was found that upon taxiing out from Terminal 4, the crew had been expecting to use the full length of the departure runway 09R but had then been advised, due to temporary closure of part of the parallel taxiway leading to the full length holding point, that they could either accept departure from an intermediate intersection or cross to the opposite side of the runway to access the full length from the opposite parallel taxiway. The aircraft commander decided that an intersection take off would be acceptable and, in the absence of any information to allow the necessary performance calculations to be made for the chosen intersection, decided that reference could be made instead to a chart for a similar length of runway at another aerodrome. He then calculated the takeoff speeds and an assumed temperature to obtain the appropriate reduced thrust setting for the take off. The First Officer had suggested that a full thrust take off would be better, but after discussion amongst the three pilots present, this proposal had not been accepted.
The take off was observed from the TWR by the aerodrome controller and by a photographer just outside the airport perimeter at the upwind end of the runway. The controller “assessed that the aircraft lifted off significantly closer to the end of the runway than he would expect” and the photographer “thought that the aircraft was noticeably lower than normal during the initial climb”. Although the operating crew subsequently advised considering that takeoff had been “in line with their expectations and experience”, the Cruise Captain present advised the Investigation that he had considered at the time that “the acceleration was slightly slow and (had) suggested applying full power”. Neither of the operating crew recollected having heard this suggestion and the takeoff had been achieved using the reduced thrust calculated.
The Conclusion of the Investigation was that:
“The aircraft departed from an intersection for which no performance data was available in the aircraft. The performance calculation, using a chart for a different runway, did not consider obstacles relevant to the runway in use. The operator has provided additional guidance on the procedure its pilots should follow in these circumstances.”
Two Safety Recommendations were issued as a result of the Investigation as follows:
- that the European Aviation Safety Agency introduce a requirement for fixed wing operators holding an Air Operator Certificate to record takeoff speeds and, where they are variable, thrust and configuration settings used for takeoff and retain this information with the Operational flight plan. [2012-030]
- that the International Civil Aviation Organisation introduce a standard or recommended practice for fixed wing aeroplanes to record the flight management system takeoff performance data entries on the flight data recorder during the takeoff phase. The data should be retained in the operator’s flight data analysis programme. [2012-031]
The Final Report AAIB Bulletin: 12/2012 EW/C2012/02/02 was published on 13 December 2012