Accidents and incidents involving the V-22 Osprey

USAF CV-22 Osprey flies a test mission

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

There have been four significant failures during flight testing, one combat-zone crash, and a number of minor incidents.

Crashes

The V-22 has had 5 crashes with a total of 34 fatalities.

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 Congresspersons 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 faster than normal (over 2,000 ft/min or 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 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, the V-22's flight operations rules restricted the Osprey to a descent rate of 800 feet per minute (4.1 m/s) at airspeeds below 40 knots (74 km/h) (restrictions typical of helicopters); the crew of the V-22 in question exceeded this operating restriction with a rate more than 100% greater.

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 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.

April 2010

On 8 April 2010, a USAF CV-22 crashed in southern Afghanistan. Three US service members and one civilian were killed and 16 injured in the crash. It was unclear if the accident was the result of enemy fire. Taliban spokesmen have claimed responsibility, however previous claims for downing aircraft have often been false. The loaded CV-22B was at its hovering capability limit, landing at night near Qalat (altitude approx. 5,000 feet) in brownout conditions, in turbulence due to the location in a gully. The USAF investigation ruled out brownout conditions, enemy fire, and vortex ring state as causes. The investigation found several factors that significantly contributed to the crash; these include low visibility, a poorly executed approach, loss of situational awareness, and a high descent rate.

Brig. Gen. Donald Harvel has fingered the "unidentified contrails" during the last 17 seconds of flight as indications of engine troubles. The actual causes of the crash may never be known because US Military aircraft destroyed the wreckage and black box recorder.

Other accidents and notable incidents

November 2004

A USMC MV-22B, BuNo 165838, lost a substantial piece of a prop-rotor blade during test flight in Nova Scotia, Canada, on 26 November 2004, but was able to make safe precautionary landing at CFB Shearwater despite severe airframe vibration.

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 30 feet (9.1 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$ 7,068,028. 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 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 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 Lejeune 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 shock wave 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 those Block-B aircraft already incorporated the modification.

FY 2009

An Air Force CV-22 suffered a Class A mishap causing more than a million dollars in damage sometime during FY 2009. No details were released.

References

• Norton, Bill. Bell Boeing V-22 Osprey, Tiltrotor Tactical Transport. Midland Publishing, 2004. ISBN 1-85780-165-2.

External links

• A video footage of the 1991 Osprey crash with commentary
• CV-22B Accident Investigation Board