Flight-recorder
information from the Airbus A340-600 involved in the Toulouse
ground-test accident last week shows that the aircraft's
engines were not retarded to idle until two seconds before
the jet struck its test-pen wall. The aircraft, which had
been performing an engine and brake test, was travelling
at around 30kt (55km/h) at the time of impact. French
investigators have determined that the A340-600, which was
undergoing pre-delivery checks, was being held at standstill
with the parking brake on and all four Rolls-Royce Trent
500 powerplants running with a relatively high engine pressure
ratio of 1.24-1.26.
Wheel
chocks were not inserted under the aircraft at the time
of the 15 November accident.
In
an information telex to operators Airbus states that high-thrust
engine ground runs are normally only performed on one powerplant
at a time, with the corresponding engine on the opposite
wing running at limited thrust to counterbalance. It adds
that wheel chocks should be installed during such tests.
While
the parking brake is set, the A340's alternate brake system
provides the brake pressure. This pressure was normal during
the Toulouse A340's engine run.
Investigation
agency Bureau d'Enquetes et d'Analyses states that the aircraft,
for as-yet undetermined reasons, began to move forward after
the engines had been running for about 3min.
The
Airbus communication says the crew applied brake-pedal input
within 1-2s of the initial movement and switched off the
parking brake; the regular braking system's pressure rose
to its normal level. But Airbus adds that all four engine
thrust levers were only retarded to their 'idle' setting
about 2s before the aircraft collided with the wall. By
that point the aircraft had been in motion for around 11s.
"There is no evidence of any aircraft system or engine
malfunction," says Airbus vice-president for flight
safety Yannick Malinge. "Airbus reminds all operators
to strictly adhere to aircraft maintenance manual procedures
when performing engine ground runs."
Investigations
are still continuing into the accident which destroyed the
aircraft and injured several of the nine personnel on board.
The jet had been scheduled for delivery to Etihad Airways
on 21 November.