Flutter test beckons for A350

Toulouse
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Airbus is preparing to perform flutter testing on the first A350-900 prototype, MSN1, as the time logged by the certification fleet passes 400h.

MSN1 has clocked 378h in 77 flights while the second airframe, MSN3, had accumulated 25h in three flights since its first on 14 October.

The A350 programme has cleared multiple aerodynamic performance and configuration stages including the first autoland, on MSN1’s fourth flight, gravity-fall of the landing gear, completion of air-brake setting and in-flight extension of the ram-air turbine.

MSN1 also carried out minimum-unstick tests on 26 September, during flight 57.

Airbus vice-president of flight-test regulation Hugues van der Stichel says the test, at Paris Vatry, involved accelerating the A350 to around 80kt – as quickly as possible, to maximise the available remaining runway – before reducing power and applying maximum pitch up.

The take-off is performed offset from the runway centreline, to avoid striking lights as the rear fuselage makes contact, while the pitch is not altered until the aircraft has reached sufficient height, about 300ft, to clear ground effect.

“It’s a risky test that could easily damage the aircraft,” says A350 programme chief Didier Evrard. “Fortunately we have excellent pilots.”

While MSN1 conducted the minimum-unstick take-off, MSN3 was also equipped with a tail-skid mount, as a precaution, in case it was required to perform the same test.

“We were not sure how much time it would take to get to this [point],” says Evrard, adding that the test might have needed repeating.

Van der Stichel says the free flutter test is the next major aerodynamic check. “We know it [will meet expectations],” he says. “We have to demonstrate it.”

Airbus is yet to perform formal fuel-burn performance tests but Evrard is confident. “There’s no reason it won’t be in line with our forecasts,” he says.

Four of the five certification flight-test aircraft are in final assembly at Toulouse. MSN4 has been undergoing wing join and is scheduled to fly in February 2014 – the same month as MSN2, which is being fitted with a 252-seat cabin.

Evrard says MSN2 is “entering final step of preparation”. It has already had overhead bins, window panels, an aft galley and crew rest installed as part of the interior configuration.

MSN1 will perform some 800h, and MSN3 around 600h, of the overall 2,500h certification flight-test programme. MSN2 and MSN4 will each have 400h, and MSN5 about 300h.

MSN5, the second cabin-fitted aircraft and the certification standard airframe, is to be delivered to the final assembly line “soon”, says Airbus. It will fly in May 2014, a slight shift from the tentative April timetable indicated last June.

But Evrard says MSN6, the first production A350-900 destined for Qatar Airways, is still on track to enter assembly in December for service entry in the second half of next year. Indications from an A350 presentation by Airbus in Toulouse suggest a delivery date beyond August 2014.