September 19, 2008: The Rolls
Royce AE1107C jet engines (that drive the propellers) in the U.S. Marine Corps
new tilt rotor V-22 aircraft, are wearing out ahead of schedule. That is
endangering a unique maintenance program. Overall, V-22 engines last nearly 500
hours (and some have gone over 600 hours), but in Iraq, the average is not
quite 400 hours. This is particularly bad news for Rolls Royce, which sold the
Department of Defense a "power by the hour" maintenance agreement.
The deal is what the name implies. The user pays Rolls Royce a variable amount
for repairs and replacement of the engines, depending on how many hours the
engine is used. This approach has become quite popular, and successful, for
commercial, and now military, engines (and other equipment as well). This
system gives the maintenance supplier (often the manufacturer) a financial
incentive to build the gear to last, and to keep running without untimely
failures. This works fine for equipment that is used in known conditions. The
peculiar sand and dust in Iraq, in addition to the high temperatures, proved to
be so extreme, that they wore down the AE1107C engines faster than Rolls Royce
had anticipated. The maintenance deal is being renegotiated. If the "power
by the hour" deal for the V-22 does not work, the V-22 will be more
expensive to operate, and will be down for maintenance more often.
The MV-22s used by the marines can carry 24 troops 700 kilometers
(vertical take-off on a ship, level flight, landing, and return) at 390
kilometers an hour. The V-22 is replacing the CH-46E helicopter, which can
carry 12 troops 350 kilometers at a speed of 135 kilometers an hour. The V-22
can carry a 10,000-pound external sling load 135 kilometers, while the CH-46E
can carry 3,000 pounds only 90 kilometers.
The marines began using the MV-22 in Iraq late last year, and have been
satisfied with the results. However, it was expected that there might be
problems with engine durability. Every other vehicle that uses a gas turbine
engine in Iraq (from M-1 tanks to C-17 jet transports) have reported increased
wear on their engines because of the copious and continuous dust and sand in
Iraq.
For the V-22, another problem is that even frequent inspections won't
always catch an engine that's about to die from too much dust and sand. Several
MV-22s in western Iraq (Anbar province, where marine MV-22s were operating)
have experienced engine failures. There have been no crashes, but there have
been emergency landings (followed by quick engine changes so the $70 million,
20 ton aircraft could get home under its own power). The Rolls Royce T-406
engines weigh about a ton each, and put out 6,000 horsepower. Marine
maintenance crews are trained to put a spare engine inside a V-22, along with
needed tools, fly out to where another V-22 has made an emergency landing, do
the engine change quickly, and get back to base in one piece.
