Leonardo to Inspect AW169s and 189s After Fatal Crash
Leonardo is to inspect its fleets of
AW169 and AW189 helicopters to ensure that tail rotor servo-actuators are
correctly installed as the result of an emergency
airworthiness directive issued by the European Aviation Safety
Agency Nov. 7.
The U.K. Air Accidents Investigation
Branch (AAIB) is investigating the first crash of an AW169 that occurred Oct.
27 outside the Leicester City football club — a crash that killed the team’s
owner, billionaire Vichai Srivaddhanaprabha; the pilot; and three others on
board.
The aircraft lifted off just after a
game and cleared the stadium before spinning out of control, plummeting to the
ground in a nearby industrial park and bursting into flames.
Witnesses told BBC that
an apparent malfunction in the aircraft tail rotor caused the uncontrollable
spinning descent, but AAIB has released no official cause. U.K. media reports
have said that large pieces of the tail rotor came off during flight.
"An accident occurred on an
AW169 helicopter, the root cause of which has not been identified and the
technical investigation is still ongoing," according to the EASA emergency
directive Nov. 7. "While the helicopter was on a takeoff phase at low
forward speed, a loss of yaw control has been observed. As a precautionary
measure, Leonardo issued ASB [alert service bulletin] 169-120 for AW169
helicopters to provide inspection instructions to check correct installation of
the tail rotor (TR) servo-actuator and, subsequently, ASB 189-213 with the
same instructions for AW189 helicopters, since these have a TR flight control
system of similar design to AW169 helicopters."
"The incorrect installation of
the TR servo-actuator, if not detected and corrected, depending on
the flight condition, could possibly result in loss of control of the
helicopter," the directive said. "For the reason described above,
this AD requires a one-time visual inspection of the TR servo-actuator
installation and, depending on findings, accomplishment of applicable
corrective action(s). This AD also requires reporting of inspection results to
Leonardo. This AD is considered to be an interim action and further AD action
may follow."
In the past few years, Leonardo has
employed simulators to train pilots how to recover from tail rotor failures.
In November 2016, Roberto Bianco-Mengotti,
an engineer with Leonardo, discussed the company's efforts in a keynote address
at the Rotorcraft Virtual Engineering (VE) Conference at the University of
Liverpool.
"The Leonardo keynote
(Bianco-Mengotti), The Advantages of Virtual Engineering in the
Rotorcraft Flight Mechanics Design Process, introduced the triangle of
advantages — safety, effectiveness and economy — that virtual engineering
offers the aviation community, particularly helicopter manufacturers,"
Gareth Padfield, a professor of aerospace engineering at the University of
Liverpool and the chairman of the conference, wrote earlier this year in a paper for
Aeronautical Journal. "A success story for the safety advantage
was described relating to tail rotor failure, considered in the design of the
AW169 helicopter, to ensure recovery was possible, and to provide guidance on
the recovery techniques for pilots."
Padfield told R&WI that
Bianco-Mengotti was waiting to comment until after the AAIB finishes its
investigation.
"I am not privy to the AW169
design features that impact tail rotor loss or indeed their recommended
training practices," Padfield told R&WI asking what
design features and training techniques Leonardo had employed to increase the
chances of recovery on an AW169 after a tail rotor failure. Padfield said that
from the video of the Oct. 27 crash, "it appears that the aircraft begins
to rotate clockwise (viewed from above) about 40 seconds after takeoff, which
would be consistent with a tail rotor drive failure or control failure with the
tail rotor pitch failing at a low value."
"We will have to await the AAIB
investigation and analysis to know the full story," Padfield said. "I
led a project on tail rotor failures many years ago in response to our Ministry
of Defense's concern that the frequency of tail rotor failures was unacceptably
high."
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