The Australian Transport Safety Bureau (ATSB) released it’s preliminary report along with detailed images and simulations in the tail strike incident of the Emirates Airlines A340-500 A6-ERG at Melbourne on March 20, 2009.
The jet with 257 passengers, 14 cabin crew and 4 flight crew on-board narrowly avoided disaster as its pilots struggled to take off from the end of Melbourne runway after wrongly entering a crucial number in a computer. As per the report, the pilots wrongly under-estimated weight data by 100 tonnes, which caused all their take-off performance settings to be computed wrong. As per the report
“While reviewing the aircraft’s performance documentation in preparation for landing, the crew noticed that an incorrect weight had been inadvertently entered into the laptop when completing the take-off performance calculation prior to departure. The performance calculations were based on a take-off weight that was 100 tonnes below the actual take-off weight of the aircraft. The result of that incorrect take-off weight was to produce a thrust setting and take-off reference speeds that were lower than those required for the aircraft’s actual weight.”
Airlines routinely use less than full thrust take off throttle settings as a means to save engine wear and should not be taken as a contributing factor. ATSB aviation safety investigations director Julian Walsh says
“The reduced power take-off is standard international practice and almost all airlines doing these type of long-haul operations use these reduced power take-offs,”
“They’ve procedures developed by aircraft manufacturers and they’re procedures that are not unique to Emirates and they’re not unique to Airbus.”
The Airbus A340-541 (MSN0608) aircraft which joined Emirate’s fleet in November 2004, underwent an “A Check” only nine days prior to the accident on March 11, 2009.
The following photos are contained in the ATSB Transport Safety Report which can be downloaded here.
This image shows the aircraft attaining computed airspeed of 143 knots, ground speed 149 knots, corresponding to the ‘V1’ computed by the crew during take-off at 1,118 meters before the end of the runway. Observe the throttle position on the far right of the graphic at less than full.
The crew did not realise the error until they tried to lift the plane off the runway and it failed to respond because it was travelling too slowly. The captain calls “rotate” a second time and the first officer raises the pitch even more. The aircraft makes initial tail contact with runway. Pitch angle 9.8°, computer airspeed 156 knots ground speed 167 knots, 229 meters to end of runway. Captain then commands TOGA (Take-off and go-around thrust setting, the maximum the engines will supply).
Engines at TOGA, despite the plane’s geometrical shape allowing a maximum pitch of 9.5°, desperate to take-off crew increased pitch to 13.7°. Computer air speed 161 knots, ground speed 172 knots, plane finally establishes positive rate of climb 292 meters AFTER end of runway 16. The report released shows the plane’s tail hit the runway three times and the landing gear hit the localiser antenna array 300 meters beyond the end of runway 16.
Damage to the airplane extensive and is estimated in the millions of dollars. Due to the significant damage to the rear pressure bulkhead the aircraft cannot be pressurised and therefore cannot be flown out. One can safely assume repairs to be done at site in Melbourne where the aircraft is parked.
The two pilots have since resigned from the airline, and the ATSB is still continuing the investigation and will focus on
- human performance and organisational risk controls
- computer-based flight performance planning, including the effectiveness of the human
- interface of computer based planning tools.
- reduced power takeoffs, including the associated risks and how they are managed.