Bell Boeing V-22 Osprey - Design

Design

The Osprey is the world's first production tiltrotor aircraft, with one three-bladed proprotor, turboprop engine, and transmission nacelle mounted on each wingtip. It is classified as a powered lift aircraft by the Federal Aviation Administration. For takeoff and landing, it typically operates as a helicopter with the nacelles vertical and rotors horizontal. Once airborne, the nacelles rotate forward 90° in as little as 12 seconds for horizontal flight, converting the V-22 to a more fuel efficient, higher speed turboprop aircraft. STOL rolling-takeoff and landing capability is achieved by having the nacelles tilted forward up to 45°. Composite materials make up 43% of the V-22's airframe. The proprotors blades also use composites.

For compact storage and transport, partly on Marine launch ships, the V-22's rotors fold in 90 seconds and its wing rotates to align, front-to-back, with the fuselage. Due to the requirement of folding the rotors their 38 feet diameter is 5 feet less than optimal for vertical takeoff, resulting in high disk loading. Most Osprey missions use fixed wing flight 75 percent or more of the time, reducing wear and tear on the aircraft and reducing operational costs. This fixed wing flight is higher than typical helicopter missions allowing longer range line-of-sight communications for improved command and control.

The V-22's two Rolls-Royce AE 1107C engines are connected by drive shafts to a common center gearbox so that one engine can power both proprotors if an engine failure occurs. However, if a proprotor gearbox fails that proprotor cannot be feathered, and both engines must be stopped before an emergency landing. The aircraft's autorotation characteristics are poor partly because the rotors have low inertia. Boeing has stated the V-22 design loses 10% of its vertical lift over a Tiltwing design when operating in helicopter mode because of airflow resistance due to the wings, but that the Tiltrotor design has better short takeoff and landing performance. The rotorwash usually prevents usage of the starboard door in hover, and the rear ramp is used for rappelling and hoisting.

The V-22 is equipped with a glass cockpit, which incorporates four Multi-function displays (MFDs, compatible with night-vision goggles) and one shared Central Display Unit (CDU), allowing the pilots to display a variety of images including: digimaps centered or decentered on current position, FLIR imagery, primary flight instruments, navigation (TACAN, VOR, ILS, GPS, INS), and system status. The flight director panel of the Cockpit Management System (CMS) allows for fully coupled (autopilot) functions which will take the aircraft from forward flight into a 50 ft (15 m) hover with no pilot interaction other than programming the system. The glass cockpit of the canceled CH-46X was derived from the V-22. The fuselage is not pressurized, and personnel must wear on-board oxygen masks above 10,000 feet.

The V-22 has triple-redundant fly-by-wire flight control systems. With the nacelles pointing straight up in conversion mode at 90° the flight computers command the aircraft to fly like a helicopter, with cyclic forces being applied to a conventional swashplate at the rotor hub. With the nacelles in airplane mode (0°) the flaperons, rudder, and elevator fly the aircraft like an airplane. This is a gradual transition and occurs over the rotation range of the nacelles. The lower the nacelles, the greater effect of the airplane-mode control surfaces. The nacelles can rotate past vertical to 97.5° for rearward flight. The aircraft also has computerized damage control that automatically isolates damaged elements.

The Osprey can be armed with one 7.62x51mm NATO (.308 in caliber) M240 machine gun or .50 in caliber (12.7 mm) M2 machine gun on the loading ramp, that can be fired rearward when the ramp is lowered. A .50 in GAU-19 three-barrel gatling gun mounted below the V-22's nose was studied for future upgrade. BAE Systems developed a belly-mounted, remotely operated gun turret system for the V-22, named the Interim Defense Weapon System. This system is remotely operated by a gunner inside the aircraft, who acquires targets with a separate pod using color television and forward looking infrared imagery. The belly gun system was installed on half of the first V-22s deployed to Afghanistan in 2009, but found limited use due to its 800 lb (360 kg) weight and restrictive rules of engagement.