Accidents and incidents involving the V-22 Osprey

USAF CV-22 Osprey tiltrotor aircraft flies a test mission

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, 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 15 feet (4.6 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 2,000 ft/min (610 m/min)) from an unusually high altitude with a forward speed of under 45 miles per hour (72 km/h) when it suddenly stalled its right rotor at 245 feet (75 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 800 feet per minute (240 metres per minute) descent at lower than 40 knots (74 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 (2,000 ft (610 m) 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 1,600 feet (490 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 6 feet (1.8 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.

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. 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.

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.

March 2007

A V-22 experienced a hydraulic leak that led to an engine-compartment fire before takeoff on 29 March 2007. 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.

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.

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.

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. No fielded Marine MV-22s were affected, as they were Block-B aircraft already incorporating the modification.

June 2008

On 21 June 2008 a Marine V-22 crew experienced a serious engine problem which forced the crew to quickly find a place to land. An internal Marine memorandum described the problem as follows:

WHILE IN FLIGHT, PILOTS NOTICED THAT THE R/H ENGINE TORQUE WOULD NOT GO ABOVE 66 PERCENT. THE AIRCRAFT WAS UNABLE TO HOLD ALTITUDE, AND HAD TO MAKE AN EMERGENCY LANDING IN THE FIELD. AFTER REPLACEMENT OF THE ENGINE, A BOROSCOPE 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