Une petite section dédiée au V22 Osprey, volontairement placé ici, car il parait que ce n'est pas un hélicoptère
More to come
Bonne journée à tous
Lawmaker Wants V-22 Production Halted
Jun 24, 2009
Bettina H. Chavanne
After three deployments in Iraq, the V-22 Osprey is facing heat from lawmakers again for reliability, maintainability and operational limitations, with the chairman of a House committee calling for a halt to production.
House Committee on Oversight and Reform Committee Chairman Edolphus Towns (D-N.Y.), issued a statement after a June 23 hearing on the tiltrotor aircraft, saying "It's time to put the Osprey out of its misery."
Marine Corps Deputy Commandant of Aviation Lt. Gen. George Trautman faced the committee to answer renewed questions about the Osprey in light of recent negative reports from the Government Accountability Office (GAO), Congressional Research Service (CRS) and the Center for Budgetary and Strategic Assessment (CSBA). Trautman did not contest the aircraft's dismal mission capable rates, which hovered at 62 percent in Iraq. However, fellow panelist Col. Karsten Heckl, commander of a tiltrotor squadron in Iraq, took issue with reports that the aircraft cannot perform in extreme conditions.
During the hearing, Towns cited the recent GAO report's findings that the V-22 "my not be operationally effective in combat" or extreme heat or cold. "I have strong reservations about the future of this aircraft," he said.
Arthur Rex Rivolo, a former V-22 analyst with the Institute for Defense Analysis, testified that the V-22 faces serious issues at high altitudes and temperatures. Heckl, whose unit deployed between March and October 2008, said what he was hearing "is disturbing, and some of it is blatantly inaccurate." He reported flying in dust storms and temperatures up to 120 degrees Fahrenheit during the summer.
Rivolo raised additional issues regarding the aircraft's lack of autorotation and combat maneuvering capabilities, which he said he has addressed in the past with government officials, to no avail.
The prevailing feeling among committee members seemed to point to a re-evaluation of the fleet mix to perhaps focus less on the V-22 Osprey, particularly in Afghanistan, due to its limitations. Trautman said he and the Marine Corps commandant perform an annual aviation review. "That's how we develop ideas that enable us to go forward," he said.
Bell Boeing looks at engine air particle separators as it bids to cut V-22 operating costs
By Stephen Trimble
V-22 Osprey engine air particle separators (EAPS) may get a fundamental redesign as Bell Boeing seeks to slash the tiltrotor's $11,000 per hour operating costs by about half.
Failures of the hydraulically powered EAPS system have caused catastrophic damage to three aircraft and are a leading source of wear and tear for the V-22's Rolls-Royce AE1107C engines.
After attempting to improve the design of the EAPS hydraulic blower, programme officials are now discussing a switch to an electric motor, says Lt Col Rob Freeland, the US Marine Corps director for medium-lift requirements.
The programme has struggled to deal with the dangers inherent in the original design of the separators, which channelled leaking hydraulic fluid into the infrared suppressor at the base of the engine nacelle and ignited damaging fires.
Bell Boeing's initial solution was to channel leaking fluid away from the IR suppressor and to speed the automatic shutdown of the EAPS suppressor when leaks are detected. But shutting off the EAPS increases wear on the engine and more recently Bell Boeing engineers have discovered the source of the hydraulic leaking causing the EAPS problems.
According to a recent USMC aviation detachment newsletter, debris from impeller shaft splines drifts into a journal bearing, which knocks the impeller into the housing for the EAPS blower. That causes vibrations that lead to hydraulic line ruptures.
For a permanent solution, Bell Boeing has considered rerouteing the hydraulic lines outside the nacelles, or shifting to an electrically powered EAPS system, with the latter judged the "technically most appealing option", the internal newsletter says.
The EAPS system is one of the main culprits for the V-22's poor reliability record in Iraq. A new report by the Government Accountability Office criticises the tilrotor for its cost per flight hour and continued operational limitations in certain combat situations.
In addition to an EAPS redesign, the USMC hopes to cut V-22 operating costs by installing improved ice protection systems and negotiating a new performance-based logistics contract with Bell Boeing that should encourage the contractors to meet part reliability and supply chain maturity goals, says Freeland.
The GAO report recommended that the Department of Defense consider buying more helicopters and fewer tiltrotors due to the V-22's operating costs.
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 fleet’s 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 of 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.