PARIS: Airbus yet to explore A350 fuel-burn performance

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Airbus will shortly embark on performance-measurement testing to determine whether the A350 is meeting fuel-burn specifications.

Speaking during the Paris air show, Airbus flight-test division president Fernando Alonso - one of the six crew members on board prototype MSN1 during its maiden flight - said the first sortie was dedicated to envelope testing.

"There was no performance measurement," he says. "That'll come in the next weeks."

But he praised the aircraft's handling. "Overall it was a very successful first flight - a little bit boring, nothing happened."

Possibly the only surprise, he says, was an unexpected decrease in cabin pressure during a climb, which the crew traced to the aircraft's automatically preparing for the descent to Toulouse after being programmed with a premature arrival time.

"We thought something was wrong. But we'd made a mistake," admits Alonso. He says the crew simply fed a different destination, New York, into the aircraft's systems to extend the flight.

While Airbus had to ground the A350 afterwards for a thorough routine maintenance check, to ensure it remained structurally sound, Alonso says: "From a technical point of view, all the aircraft needed was more fuel and we could have taken off again.

"I think the way this [flight-test campaign] has started is tremendous."

The first departure on 14 June was conducted in direct law - a precaution to enable the pilots to sense the controls and ensure that the aircraft is responding properly - with the flaps in configuration 3, followed by an initial climb to 10,000ft over the first 8min.

"We're absolutely impressed by the wing," says Alonso. "If you think it looks beautiful on the ground you should see it flying."

While staying within a height block of 10,000-15,000ft, monitored by an Aerospatiale Corvette chase aircraft, the crew retracted the landing-gear and started opening the flight envelope in various high-lift configurations, from the lowest selectable speed (Vls) to maximum flap-extended speed (Vfe).

Alonso says the configuration checks were carried out in direct law to "get a very good feel for any aerodynamic discontinuities", but adds: "We didn't feel anything."

The crew also performed various handling manoeuvres, he says: "We used the flight controls of the aircraft to introduce stimulation, to see how the structure reacts."

After the configuration checks the flaps were retracted and, with the aircraft clean, the trailing cone was extended to allow measurement of static pressure behind the aircraft. "It's important to make sure that's stable," says Alonso.

The chase aircraft broke away, the crew accelerated the A350 to maximum operating limit speed and, 2h 48min into the flight, climbed in normal law to 25,000ft.

Alonso says the aircraft was taken to 340kt, the equivalent of M0.8 at this height, and adds that the crew engaged the autopilot for the last 5min of the cruise - something which they "hadn't expected" to do - before descending in autopilot mode.

Some 3h 30min after departure, following the initial descent and with the A350 in full configuration, the pilots extended the envelope further by reducing speed to the point at which the stall warning activated.

Alonso says the landing was performed at Vls plus 5kt, adding: "We took no margins on the landing speed because we felt absolutely comfortable with the way the aircraft was flying."

Having been rejoined by the chase aircraft the A350 conducted a fly-by above Toulouse airport, at 2,500ft and 160kt, before touching down after a 4h 5min flight.