"V-22 Mishap Probe Prompts US Fleet Restrictions"

FlightGlobal.com
December 4, 2007

V-22 Mishap Probe Prompts US Fleet Restrictions

By Stephen Trimble

Believing a design defect aboard the Bell-Boeing V-22 is likely to
blame for a second in-flight engine fire, the US Navy has placed a
flight restriction on the US domestic Osprey fleet and ordered the
contractor to rush deliveries of a modification kit.

The flaw, however, will eventually require a permanent design fix,
which will heap additional cost on the V-22 programme.

Investigators of a 6 November MV-22 mishap in North Carolina believe a
nacelle fire that forced the crew to make an emergency landing was
caused by known problems with the engine air particle separator
(EAPS).
"There was enough initial indication that this incident may have been
caused by EAPS," says a US Naval Air Systems Command (NAVAIR)
spokesman.

The preliminary finding means the domestic V-22 fleet will not be
allowed to operate with the EAPS installed, he adds. BellBoeing must
deliver and install an EAPS modification kit before each aircraft can
be cleared for normal flight status.

The restriction does not affect the 10 US Marine Corps MV-22s deployed
to Iraq, as each of the aircraft is already equipped with the
modification.

Without the EAPS on board, the domestic fleet¹s stock of engines will
suffer greater wear than normal while operating under the flight
restriction.

The EAPS is a blower that keeps out dust, sand and other potentially
damaging particles. But a defect in the blower sometimes causes it to
jam.
The sudden stop sends a jolt through the number-three hydraulics line
that powers the blower. Eventually, the jolts weaken the hydraulics
tube and cause it to leak.

The super-heated fluid is channeled out of the nacelle, but its course
runs directly into the infrared suppressor, which is the source the
engine fires.

A BellBoeing spokesman says it has no estimate on the timing for
completing deliveries of the modification kit. However,
FlightGlobal.com understands that the navy expects the repairs to be
finished by the end of February.