Crew Was Able to Land Tilt-Rotor Safely; Problem Has Appeared
Investigators have determined an in-flight fire that broke out
onboard a Bell-Boeing Marine Corps MV-22B Osprey during a training
flight last year was caused by hydraulic fluid leaking onto an
exhaust cooling component in the aircraft's left engine
According to the Judge Advocate General Manual Investigation
report -- obtained by Military.com through
a Freedom of Information Act request -- a leaking hydraulic line
spilled fluid onto the engine's infrared suppressor section,
sparking a blaze that nearly consumed the aircraft in the November
6, 2007 incident.
The fire occurred about halfway through a scheduled five-hour
training mission at Camp Lejeune, NC. Fortunately, the Osprey's
crew was able to land the stricken aircraft, and escape before
In a revelation that will do nothing to downplay intense criticism of the tilt-rotor
aircraft, the JAG report also notes a similar fire
broke out in the same section on another Osprey earlier that year.
In that case, a fire broke out just before takeoff.
The Marines described that incident as a "minor nacelle fire,"
and noted modifications were underway to alleviate the problem,
which stems from spikes in hydraulic pressure that may fracture the
"Engineering investigations have shown that EAPS blower failures
can cause pressure spikes of 7,000 [to] 8,000 psi ... into the EAPS
hydraulic system," the report said. "Combining these pressure
oscillations with any existing preload in the hydraulic tube
routing can cause a catastrophic failure of the pressure tube."
Those modifications -- essentially, thicker lines in the problem
areas -- have since been retrofitted to all new "Block B" Ospreys,
including aircraft sent to Iraq. The Corps is also looking at a
more effective fluid dumping system, to drain more fluid quickly in
the event of another rupture.
"All Ospreys in flight operation have the modifications,
including those that are deployed," wrote Marine Corps spokesman
Maj. Eric Dent. "The modifications have also been fully
incorporated into the V-22 production line so that new aircraft
will not require further modification after leaving the factory...
Since this incident, 100 percent of the V-22 fleet has had the mods
installed and there have been no additional occurrences of
incidents of this type."
In its report on the November 2007 fire, the JAG found fault
with the Training Squadron's maintenance division, saying
technicians should not have allowed the MV-22 to fly such a long
training mission before undergoing a 4.5-hour inspection of the
hydraulic lines in the engine air particle separator, where both
failures occurred. The report cited errors in tracking flight hours
on the accident aircraft.
The Osprey features a unique, lightweight hydraulic system...
designed to power the aircraft's landing gear, rear cargo door and
air inlet control. Military.com notes that system also contributed
to a fatal 2000 training crash, in which a wire bundle chafed
against the thin-walled titanium lines. Four Marines died in the
New River, NC crash.
Lastly, the JAG report also notes the Osprey's fire suppression
system failed to deploy in the November 2007 accident, despite
having been triggered by the MV-22's pilot as he bailed out of the
aircraft. Officials say they're looking into that problem, as