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 with an accident history that has generated some controversy over its perceived safety. The aircraft was developed by Bell Helicopter and Boeing Helicopters; the companies partner in its manufacture.

The V-22 Osprey had 7 hull-loss accidents with a total of 36 fatalities. During testing from 1991 to 2000 there were four crashes resulting in 30 fatalities.^[1] Since becoming operational in 2007, the V-22 has had three crashes including one combat-zone crash,^[2] and several other accidents and incidents that resulted in nine fatalities.

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.^[1] The pilot, Grady Wilson, suspected that he may have accidentally set the throttle lever the opposite direction to that intended, exacerbating the crash if not causing it.^[3]

July 1992

On 20 July 1992, pre-production V-22 #4's right engine failed and caused the aircraft to drop into the Potomac River by Marine Corps Base Quantico with an audience of congressmen and other government officials. Flammable liquids collected in the right nacelle and led to an engine fire and subsequent failure. All seven on board were killed and the V-22 fleet was grounded for 11 months following the accident.^[1][4][5] A titanium firewall now protects the composite propshaft.^[6]

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 10 m/s) 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.^[7][8]

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.^[9] 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 or 610 m or more), VRS recovery is relatively easy.^[1]

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.^[1]

December 2000

On 11 December 2000, a V-22 had a flight control error and crashed near Jacksonville, North Carolina, killing all four aboard. A vibration-induced chafing from an adjacent wiring bundle caused a leak in the hydraulic line which fed the primary side of the swashplate actuators to the right side rotor blade controls. The 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) and crashed in a forest. The wiring harnesses and hydraulic line routing in the nacelles were subsequently modified. This caused the Marine Corps to ground its fleet of eight V-22s, the second grounding in 2000.^[1][10][11]

April 2010

On 8 April 2010, a USAF CV-22 crashed in southern Afghanistan.^[2] Three US service members and one civilian were killed and 16 injured in the crash.^[12] Initially it was unclear if the accident was caused by enemy fire.^[13][14] 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.^[12][15] 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.^[16]

Brig. Gen. Donald Harvel, board president of the first investigation into the crash, fingered the "unidentified contrails" during the last 17 seconds of flight as indications of engine troubles.^[17] Harvel has become a critic of the aircraft since his retirement and states that his retirement was placed on hold for two years in order to silence him from speaking publicly about his concerns about the aircraft's safety.^[18] The actual causes of the crash may never be known because US military aircraft destroyed the wreckage and black box recorder.^[19] Former USAF chief V-22 systems engineer Eric Braganca stated that the V-22's engines normally emit puffs of smoke and the data recorders showed that the engines were operating normally at that time.^[20]

April 2012

On 11 April 2012, an MV-22 from the VMM-261 on USS Iwo Jima (LHD-7) crashed near Tan Tan and Agadir, Morocco, during a joint training exercise, named "African Lion". Two Marines were killed and two others were seriously injured, and the aircraft was lost.^[21][22][23] U.S. investigators found no mechanical flaw with the aircraft,^[24] and human error was determined to be the cause.^[25]

June 2012

On 13 June 2012, a USAF CV-22 crashed at Eglin Air Force Base in Florida during training. All five aboard were injured;^[26] two were released from the hospital shortly after.^[27] The aircraft ended upside down and received major damage.^[28] The cause of the crash was determined to be pilot error, with the CV-22 flying through the propellor wash of another aircraft.^[29] The USAF has restarted formation flight training in response.^[30]

Other accidents and notable incidents

March 2006

A V-22 experienced an uncommanded engine acceleration while ground turning at Marine Corps Air Station New River, NC. 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^[31] (although initial reports suggested 30 feet), and then fell to the ground with enough force to damage one of its wings; the total amount of damage was approximately US$7 million.^[32] 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.^[33]

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.^[34] 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.^[35]

March 2007

A V-22 experienced a hydraulic leak that led to an engine-compartment fire before takeoff on 29 March 2007.^[36] 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.^[36][37]

November 2007

An MV-22 Osprey of VMMT-204 caught on 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 aircraft damage, but no injuries.^[38]

After an investigation, it was determined that a design flaw with the engine air particle separator (EAPS) caused it to jam in flight, causing a shock wave in the hydraulics system and subsequent leaks. 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.^[39]

2009

An Air Force CV-22 suffered a Class A mishap with more than a $1 million in damage during FY 2009. No details were released.^[40]

October 2014

In early October 2014, an MV-22 Osprey lost power shortly after takeoff from the USS Makin Island in the Middle East. The pilots regained control and landed safely, but one U.S. Marine drowned because of life preserver dysfunction when bailing out of the aircraft.^[41]

May 2015

One of three Osprey aircraft participating in a training exercise at Bellows Air Force Station (Waimanalo, Oahu, Hawaii) suffered from dust intake to the right engine,^[42] sustained a hard landing with fuselage damage^[43] and caught fire. The accident lead to the death of two U.S. Marines, and injuries to 20 others.^[44][45] The accident caused Marines to recommend improved air filters,^[42] and require reduced hover time in dust from 60 to 30 seconds, although most pilots rarely spend more than 10 seconds in dusty conditions.^[46]

References

• Norton, Bill. Bell Boeing V-22 Osprey, Tiltrotor Tactical Transport. Midland Publishing, 2004. ISBN 1-85780-165-2.
• Whittle, Richard. The Dream Machine: The Untold History of the Notorious V-22 Osprey. New York: Simon & Schuster, 2010. ISBN 1-4165-6295-8.

External links

• A video footage of the 1991 Osprey crash with commentary