Incorrect data input led to Emirates A340 tailstrike reports ATSB

Human factors were to blame for a tail strike suffered by an Emirates A340 at Melbourne in March 2009, concluded a report by the Australian Transport Safety Bureau (ATSB)issued yesterday.

It also called for pilots to reconsider the old “rule of thumb” mental calculation to help spot potential errors in results from the flight management system.

In the case of the Emirates flight EK407 (aircraft reg: A6-ERG) on March 20, 2009 investigators found that a simple mis-keying of the aircraft’s correct weight was failed to be spotted due to activity in the flight deck prior to departure when the captain and first officer ran through the checks.

An incorrect weight of 100 tonnes difference led to the aircraft failing to accelerate correctly before over rotating close to the end of the runway and striking the tail several times before becoming airbourne and returning to land safely.  There were no injuries among the 257 passengers, 14 cabin crew and four flight crew.. There was damage to the aircraft and to infrastructure at the airport as the aircraft overrun.

Investigators also said that the variations experienced by the crew in flying mixed-fleet operations increased the difficulty for the pilots to spot suspect outputs from the electronic flight bag readings.

“Those erroneous parameters were themselves a result of an incorrect takeoff weight being inadvertently entered into the electronic flight bag during the pre-departure preparation. Due to a number of factors, the incorrect data entry passed through the subsequent checks without detection,” it continued.

“These sorts of errors have potentially serious safety consequences,” said ATSB Chief Commissioner Martin Dolan.

In its report the ATSB said: “"Previous investigations into similar data entry error and tail-strike occurrences have highlighted the inability of flight crew to conduct a 'rule of thumb' or reasonableness check of speeds when moving between aircraft types.

"An unintended consequence of mixed fleet flying appears to be a reduction in a flight crew's ability to build a model in long-term memory to facilitate recognition of 'orders of magnitude', or a 'rule of thumb', in respect of take-off performance data."

Airbus has said that it plans additional development to include functions checking that the aircraft has sufficient runway length to conduct a safe take-off, the ATSB added. The system was shown at last month's ACI event in Abu Dhabi. The European Aviation Safety Agency (EASA) is co-operating with the European aviation equipment organisation EUROCAE to examine whether common standards could be developed.

Emirates is also understood to be working with an avionics OEM to develop a tool to alert the crew if there in as anomoly in take-off speeds.

This contrasts with the US FAA view - sought by the ATSB - that such systems, given "all of their inherent complexity", would be "more problematical than reliance on adequate airmanship".