Accidents and incidents involving the V-22 Osprey

The V-22 Osprey is an American military tiltrotor aircraft. The aircraft was developed by Bell Helicopter Textron, which manufactures it in partnership with Boeing Helicopters.

There have been four significant failures during testing,cite web|url=http://www.wired.com/wired/archive/13.07/osprey.html?pg=3&topic=osprey&topic_set=|title=Saving the Pentagon's Killer Chopper-Plane|work=Wired, July 2005] and a number of minor incidents.

Crashes

June 1991

A miswired flight control system led to two minor injuries when the left nacelle struck the ground while the aircraft was hovering convert|15|ft|m in the air, causing it to bounce and catch fire on 11 June 1991.

July 1992

On 20 July 1992, a leaking gearbox led to a fire in the right nacelle, causing the aircraft to drop into the Potomac River in front of an audience of Congressmen and other government officials at Quantico, killing all seven crewmen and grounding the aircraft for 11 months.

April 2000

A V-22 loaded with Marines to simulate a rescue, attempted to land at Marana Northwest Regional Airport in Arizona on 8 April 2000. It descended unusually quickly (over convert|2000|ft/min|disp=s|abbr=on) from an unusually high altitude with a forward speed of under convert|45|mph when it suddenly stalled its right rotor at convert|245|ft|m, rolled over, crashed, and exploded, killing all nineteen on board.

The official cause was determined to be vortex ring state (VRS), a fundamental limitation on vertical descent which is common to helicopters. At the time of the mishap, however, the V-22's flight operations rules restricted the Osprey to an convert|800|ft/min|abbr=off descent at lower than convert|40|kn|km/h airspeed (restrictions typical of helicopters, as well); the crew of the aircraft in question exceeded this operating restriction threefold.

Another factor that may have triggered VRS was their operating in close proximity, which is believed to be a risk factor for VRS in helicopters. Subsequent testing has shown that the V-22, and the tiltrotor in general, is less susceptible to VRS, the conditions are easily recognized by the pilots; recovery from VRS requires a more natural action by the pilot than recovery in helicopters, the altitude loss is significantly less than for helicopters, and, with sufficient altitude (convert|2000|ft|disp=s|abbr=on or more), VRS recovery is relatively easy.

As a result of testing, the V-22 will have a descent envelope as large as or larger than most helicopters, further enhancing its ability to enter and depart hostile landing zones quickly and safely. The project team also dealt with the problem by adding a simultaneous warning light and voice that says "Sink Rate" when the V-22 approaches just half of the VRS-vulnerable descent rate.

December 2000

On 11 December, vibration-induced chafing from an adjacent wiring bundle caused a leak from the hydraulic line which fed the primary side of the swashplate actuators to the right side rotor blade controls. This leak caused a Primary Flight Control System (PFCS) alert. A previously undiscovered error in the aircraft's control software caused it to decelerate in response to each of the pilot's eight attempts to reset the software as a result of the PFCS alert. The uncontrollable aircraft fell convert|1600|ft|m into a forest in Jacksonville, North Carolina, killing all four aboard. The wiring harnesses and hydraulic line routing in the nacelles were subsequently modified.

Incidents

Early 2006

A V-22 experienced an uncommanded engine acceleration while ground turning at Marine Corps Air Station New River. Since the aircraft regulates power turbine speed with blade pitch, the reaction caused the aircraft to go airborne with the Torque Control Lever (TCL, or throttle) at idle. The aircraft rose convert|6|ft|m into the air, and then fell to the ground with enough force to damage one of its wings; the total amount of damage was around US$ 1,000,000. It was later found that a miswired cannon plug to one of the engine's two Full Authority Digital Engine Controls (FADEC) was the cause. The FADEC software was also modified to decrease the amount of time needed for the switch between the redundant FADECs to eliminate the possibility of a similar mishap occurring in the future.cite web|author=Lance Cpl. Samuel D. White|year=2006|url=http://www.usmc.mil/marinelink/mcn2000.nsf/main5/217128503734FF2B8525712A004D67BC?opendocument|title=VMM-263 ready to write next chapter in Osprey program|work=Marine Corps News|publisher=United States Marine Corps|accessdate=2006-04-10]

July 2006

A V-22 experienced compressor stalls in its right engine in the middle of its first transatlantic flight to the United Kingdom for the Royal International Air Tattoo and Farnborough Airshow on 11 July 2006. [cite web|url=http://www.air-attack.com/news/news_article/1864/V-22-Osprey-Makes-Precautionary-Landing-En-Route-To-UK.html|title=V-22 Osprey Makes Precautionary Landing En Route To UK|publisher=Air-Attack.com|accessdate=2007-08-06] It had to be diverted to Iceland for maintenance. A week later it was announced that other V-22s had been having compressor surges and stalls, and the Navy had launched an investigation into it.cite web|url=http://www.military.com/features/0,15240,105828,00.html|title=Navy Probes Multiple V-22 Surges, Stalls|author=Christopher J. Castelli|work= [http://defense.iwpnewsstand.com/ NewsStand] |publisher= [http://www.insidedefense.com InsideDefense.com] |accessdate=2007-04-08]

February 2007

The Air Force and Marine Corps commands temporarily grounded their entire fleet on 10 February 2007 after discovering a glitch in a computer chip that could cause the aircraft to lose control.cite web|url=http://www.washingtonpost.com/wp-dyn/content/article/2007/02/09/AR2007020901860.html|title=Marine Corps Grounds V-22 Osprey Aircraft|author=Renae Merle|publisher= [http://www.washingtonpost.com Washington Post] |date=2007-02-10|accessdate=2007-04-08]

March 2007

A V-22 experienced a hydraulic leak that led to an engine-compartment fire before takeoff on 29 March 2007.cite web|url=http://www.defencetalk.com/news/publish/airforce/Hydraulic_Problems_Vex_V-22100011256.php|title=Hydraulic Problems Vex V-22|author=Defensetalk.com|publisher= [http://www.Defensetalk.com] |date=2007-04-05|accessdate=2007-06-08] It was also reported at that time that a more serious nacelle fire occurred on a Marine MV-22 at New River in December of 2006.cite web|url=http://www.star-telegram.com/100/story/54055.html|title=Fire reported after leak of hydraulic fluid|author=Bob Cox|publisher= [http://www.star-telegram.com Star-Telegram.com] |date=2007-03-31|accessdate=2007-04-08]

October 2007

Upon delivery of the Osprey to a combat zone for the first time, one of the ten aircraft experienced an unidentified malfunction which required it to land in Jordan on 4 October 2007. It was repaired and took off again for Iraq but the malfunction returned, forcing it to turn back and land in Jordan for new repairs. [ [http://www.kansascity.com/news/world/story/308810.html Tilt-rotor aircraft deployed to Iraq] , McClatchy Newspapers, October 8, 2007.]

November 2007

An MV-22 Osprey of VMMT-204 caught fire during a training mission and was forced to make an emergency landing at Camp Lejuene on 6 November 2007. The fire, which started in one of the engine nacelles, caused significant damage to the aircraft. However, no injuries resulted from the incident. [ [http://www.havenews.com/news/helicopter_3438___article.html/fire_wednesday.html Osprey helicopter makes emergency landing] , Havelock News, November 7, 2007.]

After an investigation, it was determined that a design flaw with the EAPS (engine air particle separator) caused it to jam in flight, causing a shockwave in the hydraulics system and subsequent leaks. This hydraulic fluid leaked into the IR suppressors and was the cause of the nacelle fires. As a result, all Block-A V-22 aircraft were placed under flight restrictions until modification kits could be installed. [ [http://www.flightglobal.com/articles/2007/12/04/220038/v-22-mishap-probe-prompts-us-fleet-restrictions.html V-22 mishap probe prompts US fleet restrictions] , FlightGlobal, December 4, 2007.] No fielded Marine MV-22s were affected, as they were Block-B aircraft already incorporating the modification.

June 2008

According to the Fort Worth Star-Telegram, an internal Marine memo described a serious engine problem in an Osprey in Iraq that forced the crew to make an immediate unscheduled landing in a combat zone due to the engine breaking up. The memo read as follows: Quotation|"WHILE IN FLIGHT, PILOTS NOTICED THAT THE R/H ENGINE TORQUE WOULD NOTGO ABOVE 66 PERCENT. THE AIRCRAFT WAS UNABLE TO HOLD ALTITUDE, AND HAD TOMAKE AN EMERGENCY LANDING IN THE FIELD. AFTER REPLACEMENT OF THE ENGINE, ABOROSCOPE INSPECTION WAS CONDUCTED TO INSPECT THE ENGINE INTERNALLY. IT WAS DISCOVERED THAT COMPRESSOR BLADES WERE DAMAGED FROM POSSIBLE FOD INGESTION. A BOROSCOPE INSPECTION OF THE COMBUSTION CHAMBER SHOWED THAT THE LINER HAD BROKEN INTO PIECES. THESE PIECES ENTERED INTO THE GAS GENERATOR, CAUSING SIGNIFICANT DAMAGE.

INTERNAL FAILURE OF THE ENGINE CAUSED FOR A LOSS OF ALTITUDE CONTROL. THE AIRCRAFT WAS UNABLE TO STABILIZE OR HOLD AN ALTITUDE, AND WAS FORCED TO LAND. THIS COULD BE FATAL TO PERSONNEL ABOARD THE AIRCRAFT, AND CAUSE DETRIMENTAL DAMAGE TO THE AIRCRAFT. THE MISSION WAS ABORTED DUE TO THE FAILURE." -Internal Marine Memo [ [http://startelegram.typepad.com/sky_talk/2008/07/more-v-22-engin.html Fort-Worth Star Telegram: More V-22 engine problems] ]

When asked for comment the Marines called it a precautionary landing, that the cause of the mechanical problem is currently being investigated, the environment in Iraq is challenging for every aircraft, and it was the first incident of its kind involving the MV-22 Osprey in Iraq. Box Cox of the Star-Telegram noted that "The V-22 is supposed to be able to fly at least some distance and land on just one engine, but in this case it was unable to hold altitude while still getting significant power from the damaged engine." [ [http://startelegram.typepad.com/sky_talk/2008/07/more-v-22-engin.html Fort-Worth Star Telegram: More V-22 engine problems] ]

References