JVX / Tilt-Rotor

As a result of the cancellation of the replacement assault transport helicopter (HXM) program, the Deputy Secretary of Defense directed in December 1981 that a review of vertical/short takeoff and landing (V/STOL) technology be accomplished by the services, with the intent of establishing a joint rotary wing aircraft development program to satisfy service lift requirements for medium lift V/STOL aircraft in the 1990's and beyond. The directive indicated a need to consolidate limited development funds in the production of a single aircraft to meet the various service needs. It called upon the Services to take advantage of advanced, but mature, tilt-rotor technology which promised increased range, speed and reliability / maintainability. As a result of the favorable comments returned by the Services, the Deputy Secretary of Defense directed the Army, Navy and Air Force to contribute an initial ~4.5 million to jointly develop an advanced multi-purpose vertical lift aircraft. JVX was born.

The JVX/tilt-rotor program was NASA's second primary research effort involving rotorcraft. NASA contributed to the JVX program through the transfer of generic tilt-rotor technology. NASA also provided facilities and expertise to address technology issues specific to the JVX.

Tilt-rotor aircraft operated as helicopters at low speeds and as fixed-wing propeller-driven aircraft at higher speeds. This permitted vertical takeoff and landing, longer cruising range, and speeds up to 640 kilometers per hour (as compared to conventional helicopters, which were limited to less than 320 kilometers per hour).

Concepts for tilt-rotor VTOL aircraft had been first studied in the late 1940s, and related investigations continued into the 1970s. During the early 1970s, the joint NASA-Army XV-15 Tilt Rotor Research Aircraft (TRRA) program began. This aircraft, developed by Bell Helicopter Textron, was a third-generation tilt-rotor V/STOL aircraft. The 12.8-meter long, 5,900-kilogram craft was powered by two 1,120-kilowatt turbine engines located in the wing tip nacelles that rotate with the rotors. The XV-15 was the first research aircraft with rotors that were designed to be tilt rotors. The XV-3 that had been designed earlier had helicopter-designed rotors that could be tilted.

By the early 1980s, tests with the XV-3 and XV-15 research aircraft and other supporting research had proven that the critical design issues could be successfully addressed. The joint NASA-Army TRRA program provided the confidence level necessary for DOD to initiate full-scale development of the JVX. The V-22 Osprey was the designation for the military version of the JVX. It was based on the Bell XV-15 tilt-rotor demonstrator.

Scale-model wind tunnel testing was conducted at Langley Research Center to investigate JVX spin characteristics and to establish aero-elastic stability boundaries for the JVX preliminary design. The Vertical Motion Simulator at Ames Research Center was used in two design and development tests to validate the JVX math model and evaluate the flight control system characteristics. Critical performance testing completed at the Ames Outdoor Aerodynamic Research Facility provided new data on hover efficiency and wing download.

As initially envisioned, JVX would satisfy the Marine Corps' HXM requirements as well as provide a new special electronic mission aircraft (SEMA) for the Army, a combat search and rescue aircraft (SAR) for the Navy and Air Force, and an Air Force special operations aircraft. Additionally, it was anticipated that JVX would reduce or replace a number of aircraft and helicopters in the DoD inventory, given its multi-mission capability. The Army would replace its SEMA aircraft (OV-I, RU-21, RC-12, EM-I, etc.), the Air Force its HH-53 and HH-60 helos, the Navy its HH-3 helos and as previously stated, the Marine Corps its CH-46 and CH-53 A/D helicopters. The planned acquisition of 1,086 aircraft were to be used.

A Service Secretaries Memorandum of Understanding of 4 June 1982 established a funding share for the common development program of: 34 percent Army, 50 percent Navy and 16 percent Air Force. Each service was to fund and support its own unique operational testing as well as the cost of unique configuration packages and mission equipment. The Army's SEMA mission required the JVX to vertically lift a 4,600 pound electronic kit and cruise at 250 knots up to 30,000 feet for four hours. This lift requirement necessitated a larger aircraft (40,000 pound) and more powerful engine than the other services' mission needs.

The projected mission requirements of the Marine Corps for the early 1990's dictated that the initial production of Marine aircraft be equipped with T64 engines (as on their CH-53E helos), but that a Modern Technology Engine (MTE) be incorporated in follow-on Marine aircraft as well as for all production Army, Navy and Air Force derivatives. In June 1982, the estimated JVX unit flyaway cost, depending on service and mission-unique equipment, ranged from $12.4 million 5 to ~17.3 million in constant FY83 dollars.

In the Spring of 1983, the Army reviewed its overall aircraft mission requirements and decided to withdraw from the JVX development program. Concurrently, the Air Force reduced its requirement for the JVX from 200 to 80, those aircraft to 6 be used solely for special operations. JVX was in trouble.

The Defense Resources Board (DRB), at a special meeting in September 1983, reviewed the JVX initiative and agreed that the Army could pull out of JVX. The Board then consolidated all the FY84 JVX funding in the Navy's R&D account and designated the Navy as lead service. The resulting funding share thus became 84 percent Navy (as the Marine Corps contracting sponsor) and 16 percent Air Force. Subsequently, in December 1983, the Secretary of the Army agreed to purchase 231 JVX aircraft for transportation and logistic support. The Army was now back onboard, but only as a bystander in that JVX would not be designed for the SEMA mission. They would instead accept delivery of Marine Corps configured JVX's with minor Army-unique modifications. The total anticipated JVX buy now amounts to 913 aircraft.

Without the Army's SEMA (heavy lift) requirement as the driving factor, the Program Manager anticipated that the program would be easier to execute and conversely, it should make it a little cheaper.

Based on the advanced, but [apparently] mature tilt-rotor technology embodied in the Bell XV-15, JVX was to be "scaled up" in size and weight to perform a wide variety of missions. By flying both as a turbo-prop aircraft, at speeds up to 250 knots at 30,000 feet with a 2100 mile (unrefueled) self-deployment capability, and as a helicopter, JVX would give the Services far greater flexibility of tactical employment than the current mix of helicopters and utility aircraft. Central to the success or failure of the JVX acquisition program was industry's ability to design a hybrid, tilt-rotor aircraft that will satisfy joint service requirements.

The JVX program was given a low-to-medium technological risk assessment assigned to by NASA, industry and DoD. But significant problems would have to be overcome as engineering changes and enhanced capabilities were added during the development cycle. In addition to the especially critical shipboard compatabillty requirement for the Marine and Navy versions, a key factor was the need to provide JVX with an engine producing high horsepower per unit weight and low specific fuel consumption.