V-22 Osprey

© Photo: James Darcy, United States Navy
Osprey in action.

The V-22 Osprey is a tiltrotor aircraft that marries the function of a helicopter with an airplane. A tiltrotor craft takes off like a helicopter and then switches to flying like an airplane while in flight. The tiltrotor craft is able to do this thanks to “fly-by-wire” technology.

According to theUnited States Navy Fact File, the Osprey is a tiltrotor aircraft with a 38-foot rotor system and engine/transmission nacelle mounted on each wing tip. It can operate as a helicopter when taking off and landing vertically. Once airborne, the nacelles rotate forward 90 degrees for horizontal flight, converting the V-22 to a high-speed, fuel-efficient turboprop airplane. The wing rotates for compact storage aboard ship. The first flight occurred in March 1989. The V-22 is the world's first production tiltrotor aircraft. Planned purchases include 360 for the United States Marine Corps, 48 for the United States Navy and 50 for the United States Air Force.

The Osprey can carry 24 combat troops, up to 20,000 pounds internal cargo or 15,000 pounds external cargo, according to Boeing Defense, Space and Security.

Controversies

Considerable attention has come from Congress and its auditing arm, the General Accountability Office.A relatively recent GAO report asks for much more analysis before making further investments.

Development history

While the aircraft is now operational and preliminary reports are positive, the development history was long and troubled, and involved balancing costs and risks, and managing the integrity of the procurement process. The U.S. Army, generally considered the lead agency for air assault and tactical mobility, began the program in 1981, but transferred it to the Navy in 1982, questioning if the technology was affordable. Full-scale funding began in 1986, and the first flight was in 1989. One month later, the Secretary of Defense stopped asking for funding, again concerned with affordability, and in December, the Navy was directed to terminate the program as not affordable when compared to helicopter alternatives

"Congress disagreed with this decision, however, and continued to fund the project. In October of 1992 the Navy ordered development to continue and awarded a contract to a Bell Helicopter Textron and Boeing Helicopters joint venture to begin producing production-representative aircraft."

While the aircraft is now operational and preliminary reports are positive, the development history was long and troubled, and involved balancing costs and risks, and managing the integrity of the procurement process.

Technology issues

V-22 flight performance envelope during evaluation

During operational evaluation in 2000, there was a fatal crash caused by the vortex ring state (VRS) condition.

The side-by-side rotor configuration of V-22 is susceptible to asymmetric onset of Vortex Ring State (VRS), brought on by descending too quickly. The one-rotor-in/one-rotor-out conditions results in large rolling moments and departure from controlled flight. Such a characteristic is fundamental and cannot be remedied by minor design changes. The only near-term solution is to restrict operations to avoid proximity to VRS region. V-22 advocates say V-22 pilots can escape vortex ring state by tilting the rotors forward to get out of helicopter mode.

Deployment and variants

It was first deployed operationally in Iraq. Not surprisingly, since it is not a true helicopter and has different characteristics, field experience led to rethinking some of its roles. "or example, the introduction of the MV-22 into Iraq in combination with existing helicopters has led to some reconsideration of the appropriate role of each. Battlefield commanders and aircraft operators in Iraq identified a need to better understand the role the Osprey should play in fulfilling warfighter needs. They indicated, for example, that the MV-22 may not be best suited for the full range of missions requiring medium lift, because the aircraft’s speed cannot be exploited over shorter distances or in transporting external cargo. These concerns were also highlighted in a recent preliminary analysis of the MV-22 by the Center for Naval Analysis, which found that the MV-22 may not be the optimal platform for those missions."

Note that the "M" prefix, in U.S. aircraft naming, normally denotes a special operations variant, where "C" designates a transport aircraft. The Marines and Air Force appear to have, for unclear reasons, reversed this convention. "H", as used by the Navy, is a proper prefix for search missions.

Boeing is responsible for building the fuselage, empennage, and all subsystems, digital avionics, and fly-by-wire control systems. Bell Helicopter Textron, Inc. is responsible for the wing, transmissions, rotor systes, engine installation and finally assembly at their assembly plant located in Amarillo, Texas, USA.

The Osprey was approved for full-rate production by United States Department of Defense in September 2005. A multi-year contract was approved in March 2008 for 167 aircraft. Later approval was given for building 174 aircraft, according to Boeing.

The 2010 production schedule calls for making 29 deliveries of the Osprey.

U.S. Marine Corps

MV-22 is the Marine Corps version of the Osprey which promises serve as an expeditionary aircraft with assault capabilities. The Marine version of the Osprey is designed as an assault aircraft and for use in special operations.

The USMC currently has five Osprey combat squadrons. VMM-263, were sent to Iraq in October 2007. This was the maiden combat debut for the Osprey. The Marines also sent three squadrons toIraqi Freedom and returned to the US in 2009. Several MV-22's made the first inaugural voyage with the 22 Marine Expeditionary Unit in 2009.

The Osprey was sent toAfghanistan in November 2009.

U.S. Navy

HV-22A is the United States Navy version of the V­22. The USN version is designed to provide combat search and rescue, the delivery of special warfare teams and their removal from the theater, and fleet support.

U.S. Air Force

CV-22A is the Air Force version of the V-22. The Air Force version will provide long-range special operation missions. The US Air Force Special Operations Command received the Osprey in 2006. The Osprey was sent to Mali, Africa to support Exercise Flintock in November 2008. Currently, the Osprey is support the US Air Force's special operations mission worldwide.

Tactics

Like any aircraft, experience tends to be needed to learn the unique tactical advantages and disadvantages of the Osprey. Early World War II, for example, the Japanese A6M Zero fighter was a fearsome opponent, but U.S. pilots learned that while it was a death sentence to try to turn with it in a dogfight, heavier fighters could win by diving on the Zero and firing on its totally unprotected areas.

GAO said the "V-22 has maneuvering limits that restrict its ability to perform defensive maneuvers and it does not have a required integrated defensive weapon needed to suppress threats while approaching a landing zone, disembarking troops within the landing zone, or while leaving the landing zone. Currently, the Marine Corps intends to employ the aircraft in a manner that limits its exposure to threats mdash; a change from the original intent that the system would be able to operate in such environments.

Lieutenant Colonel Christopher ‘Mongo’ Seymour, who commanded the Marine VMM-266 Osprey squadron, spoke of some of the lessons learned. In mission planning, he said the Osprey had to be understood as more like an extremely agile version of the C-130 Hercules fixed wing transport, typically flying at medium altitude, than a helicopter that routinely skims the ground. Helicopter doctrine is "that you have to have two aircraft. So we wanted to carry out the task in some scenarios as a little brother to the C-130 – they don’t task a C-130 in sections and we are the same case." Seymour said that two Ospreys were often sent on missions that could easily have been handled by one.

He predicted that its characteristics would do well in the mountains of Afghanistan. "We can trade fuel for payload and altitude. The other beauty about the Osprey is that the CH-46 – well even the CH-53 (it could do this but they don’t like to) – if it was a hard hit mission, picking up somebody who’s been hit, troops in contact etc, I could go to a high zone at 9,000 or 10,000 ft, drop somebody off and pick them up. And if the mission has been long and maybe I do not have enough gas to get back to Kabul, I could meet a tanker pretty easily and refuel and make it – which is the difference. Once I am in aeroplane mode, hover performance is not an issue any more. I could go to 60,500 lb at 20,000 ft just like that."

Addressing the survivability concerns, Seymour observed that the Osprey, at its normal altitude of 8-12,000 feet, is much quieter than a lower-flying helicopter, and is harder to see from the ground. "So nobody knows to look up – and even if they did a grey V-22 on a blue background is virtually impossible to spot. We have several tactical approaches that we use. Let me just tell you this, when I was in the test world I did a one-for-one comparison between a V-22 and an AH-1. The set-up was an array of acoustic sensors in a target area. We had to fly over the sensors on the same path, type of day etc.

"So we fly the V-22 at 200 ft and 220 kts over these sensors at a five-mile range. Then the Cobra did it. The unclassified data showed that if you were at the target you would hear the Cobra two minutes before he reached you; with the V-22 it wasn’t heard until 10 seconds beforehand [the author experienced and can verify the quietness of the aircraft over several days at Al Asad with Ospreys, Sea Knights, CH-53s, Hueys and Cobras flying in and out during the period – the V-22 was the quietest of the lot]." In other words, accept that an Osprey is not a pure helicopter substitute.

Flying An Osprey

The pilot uses a single set of controls to fly the Osprey and can during flight switch from helicopter to fixed wing mode with ease by using automatic controls to switch from helicopter to fixed wing mode.

The nacelle angle is controlled by the pilot using the nacelle control. The pilot can also adjust for angle, acceleration for forward or aft and control aircraft pitch. The nacelle control complements the longitudinal cyclic stick and includes automatic conversion corridor protection control.

During flight the nacelles will begin to rotate allowing the craft to swtich from helicopter mode to airplane mode. The process is called transition. During transition the piot can manually control the operation or opt for automatic transition using the flight control system. It takes approximately 16 seconds to complete the transition process. In the case of the Osprey, the nacelle is used to house or enclose the aircraft's engine.

Conversion is the opposite process. The Osprey will switch from aircraft mode to helicopter mode during the conversion process. Again, the nacelles are a key part of the conversion process.

Both the transition and conversion modes of flying can take place continuously, stopped as needed, or reversed. Airplane flight though needs to take place when the Osprey is flying between 40 to 80 knots and has a wide range of permissible air speeds (approximately 100 knots).

Logistics and support

Bell Boeing operates a logistics support center in New Bern, North Carolina. This is close to the Marine Corps Air Station at Cherry Point, the main location for Marine Osprey operational development.

On 15 June 2009, Bell Boeing Program Office received an $11 million dollar, Phase 1.5 of a two-phase Joint Performance Based Logistics (PBL) contract from the U.S. Department of Defense to support the V-22 Osprey tiltrotor aircraft for the Marine Corps (MV-22), and Air Force Special Operations Command (CV-22).

Engines Two Rolls-Royce Liberty AE1107C AEO VTOL Normal Power, shp (kW) : 6,150 (4,586) AEO VTOL Interim Power, shp (kW) : 6,830 (5,093) OEI VTOL, shp (kW) : 6,830 (5,093) Transmission AEO VTOL Max Cont., rhp (kW) : 4,570 (3,408) AEO VTOL Takeoff, rhp (kW) : 5,183 (3,865) Proprotor System Blades per hub : 3 Construction : Graphite/fiberglass Tip speed, fps (mps) : 661.90 (201.75) Diameter, ft (m) : 38.00 (11.58) Blade area, ft2 (m2) : 261.52 (24.30) Disc area, ft2 (m2) : 2,268.00 (210.70) Blade folding : Automatic, powered Performance Max Cruise speed (MCP), SL, kts (km/h) : 241-257 (446-476) Max R/C, A/P Mode, SL, fpm (m/m) : 3,200 (975) Service ceiling, ISA, ft (m) : 24,700 (7,529) OEI Service ceiling, ISA, ft (m) : 10,300 (3,139) HOGE ceiling, ISA, ft (m) : 5,400 (1,646) Mission radius with aft sponson tank Land-Assault Troop Mission (24 Troops), nm (km) : 242 (448) Pre-Assault Raid, nm (km) : 267 (495) Mission radius with wing tanks Land-Assault Troop Mission (24 Troops), nm (km) : 233 (432) Pre-Assault Raid, nm (km) : 306 (567) Accommodation Cockpit - crew seats : 2 MV / 3 CV Cabin - crew seat/troop seats/litters : 1/24/12 Dimensions (External) Length, fuselage, ft (m) : 57.3 (17.48) Width, rotors turning, ft (m) : 84.6 (25.55) Length, stowed, ft (m) : 63 (19.20) Width, stowed, ft (m) : 18.4 (5.61) Width, horizontal stabilizer, ft (m) : 18.4 (5.61) Height, nacelles fully vertical, ft (m) : 22.1 (6.73) Height, vertical stabilizer, ft (m) : 17.9 (5.46) Height, stowed, ft (m) : 18.3 (5.56) Dimensions (Internal) Length, max, ft (m) : 24.17 (7.37) Width, max, ft (m) : 5.92 (1.80) Height, max, ft (m) : 6.00 (1.83) Weights Empty, lbs (kg) : 33,459 (15,177) Takeoff, vertical, max, lbs (kg) : 52,600 (23,495) Takeoff, short running, max, lbs (kg) : 57,000 (25,909) Takeoff, self-deploy mission, lbs (kg) : 60,500 (27,443) Cargo hook, single, lbs (kg) : 10,000 (4,536) Cargo hook, dual, lbs (kg) : 15,000 (6,804) Fuel Capacity MV-22 (including aft sponson tank), gallons (liters) : 1,448 (5,481) CV-22 (including aft sponson tank), gallons (liters) : 2,040 (7,722) Fuel Capacity with wing tanks MV-22 (including wing tanks, no aft sponson tank), gallons (liters) : 1,724 (6,526) References