The ATSB carried out a safety deficiency investigation in accordance with powers under section 19CB (1) (d) of the Air Navigation Act 1920.
SAFETY DEFICIENCY
An allegation was made to the ATSB that Australian registered Boeing 747-300 aircraft operating from Bangkok airport in Thailand were failing to meet take-off performance requirements. A 'specified' flight was cited as demonstrating that the aircraft had not complied.
Comprehensive analysis of data from the 'specified' flight, as well as data from other flights departing Bangkok under similar conditions, was undertaken. Documentation provided by the crew of the 'specified' flight was also analysed. The data included brakes release to VR (take-off rotation speed); VR to VLOF (aircraft lift off speed); VLOF to 35 feet; total distance from brakes release to V2 (take-off safety speed) at 35 feet.
Appropriate sections of the Boeing and the operator's Flight Crew Training Manuals (FCTM) were reviewed and the ATSB concluded that the actual take-off data correlated with the Flight Crew Training Manual information.
For certification, the Boeing 747-300 aircraft is required to be able to sustain an engine failure at or after a specified speed (V1) at its maximum take-off weight and safely climb on the thrust of the remaining three engines. V1 is the decision speed at and below which take-off can be aborted and the aircraft stopped within the runway confines. It is also the speed at and above which the take-off can safely be continued should the critical engine become inoperative, where the critical engine is the engine that would most adversely affect the performance or handling qualities of the aircraft.
Analysis of the recorded data confirmed that the 'specified' take-off from Bangkok was with four engines operating. No evidence was found to suggest that the aircraft concerned did not meet the certified requirements for take-off performance.
Nothing in the cases examined suggested that the aircraft would not be able to safely climb from the runway on three engines if an engine had failed at or after reaching V1 speed. Had an engine failure occurred before V1, by definition the aircraft would have been able to stop within the runway confines.
Formulae from Boeing Jet Transport Methods were used to derive actual take-off distance of the 'specified' take-off. Digital Flight Data Recorder (DFDR) and Quick Access Recorder (QAR) data were used to establish time from brakes release to rotate, time from rotate to lift-off, time from lift-off to a height of 35 feet by radar altimeter, and to calculate take-off distance. Data from the flights analysed showed the aircraft met the certification requirements for take-off performance.
Calculations by Boeing and the operator were assessed by performance engineers from the Civil Aviation Safety Authority. Subsequent independent review of the data, including comparison with the ATSB's calculations, verified the accuracy of those calculations. Again, no evidence was found to suggest that the aircraft did not meet certified performance requirements.
The ATSB was not able to source any information to quantify any in-service experience with the worldwide Boeing 747-300 fleet to suggest that there has been any deviation from the aircraft performance levels indicated in the approved Aircraft Flight Manual.
There is also no evidence that a dangerous situation as described in the report of the alleged safety deficiency has occurred in the 12 month period to October 2000. The ATSB concluded that Boeing 747-300 aircraft are meeting scheduled performance requirements.
Occurrence Date: 14 NOVEMBER 1999
Registration No: VH-EBX
Model: B747-300
Manufacturer: Boeing Co