|Bell/Boeing-Vertol V-22 "Osprey"|
The Bell company brought a long history of vertical-lift Tilt-Engine system development to this program when it combined with Boeing in the early 1980s.
The company had demonstrated such a system with the XV-3, proving that it was possible to turn wingtip rotors from a vertical position to horizontal, thus providing the thrust to lift the vehicle off the ground and then transition to horizontal flight. The XV-3 was followed by the XV-15, which would closely resemble the V-22, with the XV-15 initially serving as the test vehicle for the V-22.
During the early 1980s, the new Bell-Boeing competed for the lucrative Joint Services Advanced Vertical Lift Aircraft (JVX). Then, on April 26, 1983, the joint team was awarded the contract to begin the preliminary design stage.
Initially called the Bell/Boeing-Vertol JVX, the plane would later be given the V-22 Osprey designation, and later, special mission variations carrying the designations of MV-22, HV-22, and CV-22.
The then-ambitious 1983 plan called for 1086 of the tri-service VTOLs to be produced with a total procurement cost of $25 billion, with the funding to be shared by the three services. The Navy was to assume the bulk of the obligation with 50 percent contribution.
The initial requirement called for the craft to support all the services and be capable of carrying 24 troops. There were many other possible missions mentioned for the revolutionary new VTOL, such as electronic warfare, amphibious assault, and special operations.
Unlike a helicopter, the V-22 doesn't have to be disassembled and transported in a transport aircraft. With a single refueling it will be able to fly 3380km.
Power for the Osprey, which is about half the size of a C-130, comes from a pair of General Electric T64-GE-717 turboshaft engines, each rated at 6150hp. The power is definitely needed, since the V-22 weighs in at about 24800kg maximum take-off weight in a STOL configuration, and about 19840kg in a pure VTOL mode. Its empty weight is just over 14880kg.
The rotor diameter is a large 11.6m, with an overall fuselage length of about 17.4m. With the rotors in the take-off position, the height of the vehicle is just over 6m. The width of the vehicle, with the rotors turning, is almost 26m.
Those rotors, by the way, are capable of rotating through 97 degrees and are constructed of graphite/glass fiber. In fact, 33 percent of the weight of the Osprey is fabricated of that high-tech material.
The rotors also possess separate cyclic control swashplates for sideways flight and fore-and-aft control during hover. Lateral attitude is maintained by differential rotor thrust. Once the V-22 achieves horizontal flight, the engines have assumed a position parallel to the fuselage.
The V-22 can even fly backwards! This maneuver is accomplished by tilting the rotors back past the 90-degree vertical position. Such a capability might someday provide a useful combat tactic.
Initial performance requirements for the Osprey were a cruising speed of 480km/h with a range with a full payload of over 1450km. And even though the V-22 carries a cargo designation, it does carry a nose-mounted 12.7mm multi-barrel machine gun.
Since the V-22 will be operating in a combat environment at least a portion of the time, the plane's design has taken the situation into account. There are redundant systems, along with armor, in critical areas. The tough composite materials also provide protection. Also, one engine can power both rotors if required because of a cross-coupling capability.
The full-scale development program began in May 1986 with the order for six prototypes. Numbers 1, 3, and 6 were constructed by Bell at Arlington, Texas, and numbers 2, 4, and 5 by Boeing at Wilmington, Delaware. The first flights for the new vehicles occured between 1988 and 1991.
In 1995, the production of test vehicles resumed with numbers 7 through 10 for vibration, propulsion, USMC, and mating evaluations. Final assembly of the first production V-22 was completed in late 1998.
In 1998, Bell also began a two-year fatigue program to determine if the V-22 can accomplish a design life of 10000 hours, or about the same as 20 years of operation. The rigorous program would subject the C-22 test vehicle to 18 million different aircraft loads.
The testing planned to simulate 7000 hours in the normal aircraft role and 3000 in the VTOL mode. No structural damage at 4Gs at over 550km/h is allowed. It is probably the most rigorous test program ever carried out on a new aircraft.
In early 1998, the V-22 accomplished another milestone with its first night test flight. During the test, the V-22 flew with a neutral density filter which covered the cockpit displays. This allowed the pilots, which were using night vision goggles, to operate the displays in the day mode.
Also included in the flight test program was to investigate its capabilities for carry external loads. In one test, the number eight prototype carried a five-ton sling load through the transition phase with a top speed of 425km/h. The test pilot indicated that even though he could feel the load oscillating beneath him, it didn't affect the craft's performance.
The testing showed that certain loads caused dramatic shifts in the center of gravity of the V-22, which in turn required a change in the attitude of the aircraft. It was determined that that requirement could be accomplished by changing the angle of the engine nacelles.
Other tests planned at the time included a sling weight of 6765kg and a Humvee jeep, hopefully faster than could be accomplished by the MH-53E "Super Stallion" helicopter.
In 1997, 14 years since the long-forgotten JVX contract had been awarded for design and development, low-rate initial production was undertaken for 23 V-22s (called MV-22s) for the USMC. This event occurred after the Pentagon's Defense Acquisition Board (DAB) had earlier given the goahead for production of the V-22, The first delivery was scheduled for 1999, with IOC occurring in the 2001 time period.
The projected cost of these first operational V-22s had a unit cost of $32.2 million each, a figure that was down considerably than the $41.8 million projected during the full-scale development program. The plane has attracted international interest, with both Israel and Australia both showing interest in the unique VTOL. Up to 423 V-22s are desired by the Marines, but there will probably be up to 50 built for the USAF for special operations activities.
Bell is building the wing section, empennage, and powerplant nacelles, while Boeing has the responsibility for the fuselage and landing gear. Bell is also responsible for the final assembly and initial flight tests.
With cost always a huge consideration, serious consideration was given to faster Marine V-22 production for that very reason. It was assessed that cutting eight years off the production program, which was programmed to last through 2018, would save six billion dollars off the previously-estimated $42 billion.
Marine officials have indicated that they wanted to increase the production to 36 planes a year beyond 2004, up from the 30 now programmed. Whether that will occur remains to be seen in the late 1990s.
There is also a push for quicker acquisition of the V-22s for the U.S. Special Operations Command (AFSOC). The desire is to assume operational capability in 2004, with the first delivery in 2003. Even the Navy is looking at its own special version of the V-22 to bolster its capability to conduct covert operations.
The Osprey was also considered in the late 1990s for a search-and-rescue function. If approved, the Osprey could possibly replace the MH-60 helicopter, which now performs that function.
The projected capabilities of the V-22 over the helicopter point to its huge advantage. For example, the V-22 has a 7320m altitude capability with a speed of about 500km/h. In comparison, the CH-46E helicopter shows a 2745m altitude with a speed capability of about 230km/h.
It's for that performance advantage and its VTOL configuration that could allow the V-22 to replace a number of helicopter types in the future.
S.Markman & B.Holder "Straight Up: A History of Vertical Flight", 2000