European safety agency EASA has approved Eurocopter's proposed
interim fixes for its troubled EC225 Super Puma, which has seen
large portions of the global fleet effectively grounded since October.
interim fixes for its troubled EC225 Super Puma, which has seen
large portions of the global fleet effectively grounded since October.
The Emergency Airworthiness Directive issued on 9 July should
pave the way for a relatively speedy return to service for affected
operators later this month.
pave the way for a relatively speedy return to service for affected
operators later this month.
Two ditchings in the North Sea in May and October 2012 - caused
by circumferential cracks in the type's bevel gear vertical shaft - led
to the ban on overwater flights by civil aviation regulators in the
UK, Norway and Denmark, impacting a large proportion of the fleet
used for offshore transportation for the oil and gas industry.
by circumferential cracks in the type's bevel gear vertical shaft - led
to the ban on overwater flights by civil aviation regulators in the
UK, Norway and Denmark, impacting a large proportion of the fleet
used for offshore transportation for the oil and gas industry.
Eurocopter's root cause investigation later determined that
corrosion, fatigue and residual manufacturing stresses were
responsible for the formation of the fractures in the shaft, which
originated in a hole drilled into the metal.
corrosion, fatigue and residual manufacturing stresses were
responsible for the formation of the fractures in the shaft, which
originated in a hole drilled into the metal.
The manufacturer's interim fixes include both preventative and
precautionary measures. Falling into the former camp are mandated
manual cleaning of the shaft - between 150 or 400 flight hours
depending on the serial number of the shaft and previous
maintenance regime - to prevent corrosion, a redesign of an oil jet
and a modification to a plug fitting into the weld hole on the shaft
that was found to trap moisture.
precautionary measures. Falling into the former camp are mandated
manual cleaning of the shaft - between 150 or 400 flight hours
depending on the serial number of the shaft and previous
maintenance regime - to prevent corrosion, a redesign of an oil jet
and a modification to a plug fitting into the weld hole on the shaft
that was found to trap moisture.
Precautionary measures include regular ultrasonic non-destructive
inspection - after every 11.5h of flight - to enable detection of the
initiation of a crack at an early stage. Allied to this is a modification
to the type's health monitoring system (HUMS) linked to an amber
warning lamp installed in the cockpit, which will alert the crew in
flight to a propagating crack.
inspection - after every 11.5h of flight - to enable detection of the
initiation of a crack at an early stage. Allied to this is a modification
to the type's health monitoring system (HUMS) linked to an amber
warning lamp installed in the cockpit, which will alert the crew in
flight to a propagating crack.
"In this situation, the helicopter will continue to safely operate for
a sufficient time to allow the crew to return to base or perform a
normal landing in a safe area," says Eurocopter.
a sufficient time to allow the crew to return to base or perform a
normal landing in a safe area," says Eurocopter.
It says HUMS data from the two ditched EC225s - G-REDW and
G-CHCN - indicated a rising trend of vibrations from the relevant
sensor.
G-CHCN - indicated a rising trend of vibrations from the relevant
sensor.
"During the crack propagation campaign, nine test bench and one
flight test, that all went up to the rupture, confirmed the previously
observed raising trend, and also confirmed the HUMS as a relevant
surveillance means able to provide an early warning."
flight test, that all went up to the rupture, confirmed the previously
observed raising trend, and also confirmed the HUMS as a relevant
surveillance means able to provide an early warning."
Approvals from national regulators will still be required to allow a
full return to service.
full return to service.
In the longer term, Eurocopter will introduce a redesigned shaft to
be retrofitted to the affected helicopters
be retrofitted to the affected helicopters
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