Friday, May 1, 2009
Rotorcraft Report: V-22 Osprey Update
The U.S. Marine Corps will bring a dozen MV-22B Ospreys that have been flown in Iraq for 18 months back to the United States this month, ending a long-awaited combat debut that marked a major milestone for the tiltrotor troop transport.
"Operationally it has probably exceeded all expectations we had," Marine Col. Mathew Mulhern, V-22 program manager for the Naval Air Systems Command, told Rotor & Wing. "Maintenance-wise, we’ve got some challenges we’ve got to work through, which is probably not unusual at this point in the life of an airplane."
The V-22 reached another milestone March 6, when the U.S. Air Force Special Operations Command declared its CV-22 had reached Initial Operational Capability (IOC), certifying that version of the Osprey ready for special operations combat missions. The 8th Special Operations Squadron, based at Hurlburt Field, Fla., had six CV-22s as of the IOC declaration. The Air Force plans to buy 50 CV-22s in all.
The Air Force declaration of IOC followed the CV-22’s first operational use last fall, in which the 8th SOS flew four Ospreys to Africa and back using aerial refueling, a test of the aircraft’s required "self-deployment" capability that went smoothly. During a month-long deployment to Bamako, Mali, the Air Force CV-22s carried Malian and Senagalese special operations troops in Flintlock ‘09, a 15-nation training exercise with U.S. allies in Africa.
The Marine Corps put the Osprey into service after 25 years of development in October 2007, when Marine Medium Tiltrotor Squadron 263 (VMM-263) took 10 MV-22Bs to Iraq. The Corps sent two more MV-22Bs to Iraq during VMM-263’s seven-month deployment at Al Asad Air Base. Two other Marine squadrons, VMM-162 and VMM-266, deployed to Al Asad in turn over the succeeding months, flying the same dozen MV-22Bs on supply, troop transport and "aeroscout" insurgent-hunting missions.
VMM-263 is to deploy this summer with another 10 MV-22Bs aboard the amphibious landing ship USS Bataan, serving as the Aviation Combat Element of the 22nd Marine Expeditionary Unit. The 22nd MEU will sail in the Middle East and Indian Ocean regions and be available for use by combatant commanders in the area. Marine Corps leaders have said they also want to send MV-22Bs to Afghanistan later this year, though no final decision has been made.
The Osprey’s speed, range and ability to cruise above small arms threats proved valuable in Iraq, where there were only sporadic reports of MV-22Bs coming under fire and none suffered combat damage. The tiltrotor’s complexity, however, has made it difficult to anticipate various maintenance and reliability issues, Mulhern acknowledged.
The Naval Air Systems Command grounded all V-22s on March 24 after VMM-266 mechanics in Iraq discovered loose bolts in components of a swashplate assembly, a flight-critical part, in the starboard nacelle of one of their aircraft. "The plane shut down and the flight line guys heard some banging up there around the rotor in the top of the nacelle, so they went up and looked and saw this," Mulhern said.
Inspections of all 84 Ospreys the services own found similar problems in four other MV-22s in Iraq and one that was in maintenance at a depot at Cherry Point Marine Corps Air Station, N.C., Mulhern said. The grounding was lifted after a new inspection that takes about an hour to complete was added to V-22 daily inspections. Bell Helicopter Textron Inc., which makes the V-22’s rotors and nacelles, is conducting an engineering investigation to determine the root cause of the bolt loosening problem, Mulhern said. Engineers from NAVAIR and Boeing Co., which makes the V-22 in a 50-50 partnership with Bell, were assisting in the analysis.
The Marines and the companies got some maintenance surprises during the V-22’s deployment to Iraq, though they had stockpiled parts, such as rotor blades, and taken other steps in advance to anticipate wear and tear from the country’s sandy environment, Mulhern said. Iraq’s sand turned out to be so fine that it didn’t damage the V-22’s rotors nearly as much as officials had expected, but the talcum-like grit seeped into the Osprey’s fly-by-wire wire bundles and chafed insulation, sometimes causing shorts and false component fault warnings. "We didn’t anticipate wire bundle problems," Mulhern noted.
The Osprey’s engine air particle separators (EAPS), hydraulic devices designed to suck sand away from the air intakes and increase the service life of the V-22’s Rolls-Royce AE1107C Liberty turbine engines, failed to operate reliably in Iraq and continue to be a concern for all V-22s. The V-22s sent to Iraq were modified before the deployment with software to quickly shut down their EAPS if a sensor detected a hydraulic leak within the device, a step taken because leaks of that sort had caused several engine nacelle fires at New River. The software, however, also tended to shut down the EAPS in response to air surges during vertical takeoffs.
"We’re putting some vanes in there to control the air flow," Mulhern said. "We’re potentially moving a valve. We’re going to eventually move to an electric EAPS, though. We’re really adamant that we’ve got to get rid of the hydraulic lines up in that hot section [of the engine]."
A bigger concern, given the possible use of V-22s in mountainous Afghanistan’s higher altitudes and colder climate, is the Osprey’s ice protection system, which has never worked as it should, Mulhern said. "As we move east with these airplanes, we’ve got to have an ice protection system that works," he said.
The system is designed only to detect and prevent icing so pilots can fly around icing conditions, not through them, but consists of roughly 200 components, such as heating elements on rotor blades. Failures have occurred for various reasons, such as shorts caused by water seeping into electrical parts or cracks in parts exposed to the centrifugal force of the Osprey’s dynamic components, Mulhern said.
"When it’s functional, the system works well, but the reliability of its individual components is not acceptable," Mulhern said. — By Richard Whittle