Seven years after a Hapag-Lloyd Airbus A310-300 crashed at Vienna after suffering fuel exhaustion, the public release of the final report shows that Airbus strongly contested initial conclusions relating to the aircraft's flight-management system.

The crew of the A310, which had been operating from Chania in Crete to Hanover on 12 July 2000, had been unable to retract the undercarriage fully after take-off. Fuel reserves were "exclusively determined" using the flight-management system, which was unable to account for the increased drag of the landing gear, says the final report.

hapag 
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Flight HF3378 had been carrying 16.8t of fuel, but the increased drag caused by the lowered landing gear consumed fuel at around twice the rate of normal cruise

The report reveals that Airbus defended the FMS and expressed concern that draft conclusions would mislead regarding the design objectives and operation of the system.

In particular it said the draft report erroneously suggested the FMS failed to provide accurate fuel predictions with the A310's landing-gear down - whereas Airbus insists that the FMS was never designed to provide such predictions. It specifically states that the FMS "vertical mode", which provides fuel predictions, should not be used with the undercarriage deployed.

"There is a need to clarify...that the FMS operated as per design since it is not designed to predict fuel when flying with landing gear down," says Airbus in its comments.

Flight HF3378 had been carrying 16.8t of fuel, but the increased drag caused by the lowered landing gear consumed fuel at around twice the rate of normal cruise. The aircraft's fuel levels eventually ran critically low and the crew opted to attempt a landing at Vienna.

The A310 came down about 600m (1,970ft) short of Vienna's Runway 34, after just 2h 30min of flight, suffering damage as it slid to a halt. All 143 passengers and eight crew survived.

In its report into the accident the Austrian investigation board attributes the accident to the crew's decision to continue the flight with the undercarriage problem, stating that "extreme workload and stress" contributed to the pilots' disregarding appropriate fuel-reserve regulations.

Alternative strategies to contain the fuel-consumption issue, says the board, were overlooked and options such as a diversion to Zagreb airport, which was closer than Vienna, were not taken up. Better training and documentation on the limitations of the FMS are among the board's recommendations.

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Source: Flight International

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