Airbus is aiming to perform a maximum-energy rejected take-off with the A350-900 over the next few days, one of the riskiest tests undertaken for a new aircraft type.
It will involve ballasting the aircraft and accelerating to around 160-170kt before aborting the take-off roll with brake power.
Prior to the test the aircraft’s brakes are worn down to the limit of their wear in order to ensure the “worst possible case” for the run, said Airbus head of flight and integration tests Fernando Alonso, speaking during a Farnborough air show briefing.
While Airbus has already performed a high-speed rejected take-off with the A350, in order to generate data for its manuals, this is a less intense intermediate event carried out at around 155kt – about 80% of maximum energy.
Several aspects need to be taken into account, including the air temperature, to configure the aircraft for the test.
A350 project pilot Frank Chapman says the aircraft must be heavily loaded, but uplifting too much fuel can be counter-productive because the fuel would need to be offloaded if the aircraft needs to be jacked.
He adds that the test must also avoid generating “too much lift” because the exercise is designed to maintain pressure on the wheels and brakes.
Such is the extreme nature of the test that there is considerable risk of inflicting damage to the aircraft, as the high energy is dissipated through the undercarriage. The brakes will absorb large quantities of heat and there is a likelihood of tyre deflation and even structural damage to the axles.
“By definition it’s a destructive test,” says Alonso. He adds that the test is left until the final weeks before certification in order to minimise the impact of withdrawing a damaged flight-test aircraft from the campaign.
The test will be carried out at Istres, near Marseille, which is equipped with a 3,750m runway.
Airbus will begin assessing the meteorological forecasts at Istres from 19 July. The weather conditions for the test must be dry, with no crosswind because this could then exceed the brake limits on one side of the aircraft.
Certification is planned for the third quarter of this year. Along with route-proving tests, says Alonso, the A350 will also undergo a cyber-security check over the course of a week. While details of this check are confidential, they involve tests to ensure that the electronic systems on the jet are protected from attack.