Major features of the winning Republic Aviation design proposal for possible development of a V/STOL strike fighter are shown in model above. The design calls for a variable sweep wing and two podded, fuselage-housed lift engines on either side that swing out into the operating position during the vertical flight regimes. The lift engines. designated XV99-RA-1, are being developed jointly by the Allison Div. of General Motors Corp. and Britain's Rolls-Royce. Retractable panels for the proposed auxiliary inlets for the main cruise engine are located at the top and near the rear of the fuselage. Republic was selected as the American contractor to participate with Entwicklungsring-Sud, the West German participant. Initial versions of the lift engine would have a thrust-to-weight ratio of at least 18:1. Competition for the cruise engine is still under way, with both General Electric and Pratt & Whitney holding study contracts. Both U.S. and West German proponents of the V/STOL fighter project are seeking funds to build 12 prototypes for field evaluations.
Problems Cloud Future of V/STOL Fighter
By Cecil Brownlow
Washington—Future of the proposed U.S.-West German V/STOL tactical fighter is clouded by a myriad of political, military and financial questions, including top level
squabbles within the Pentagon. So far as an operational aircraft bearing U.S. markings is concerned, the project will have to do battle for the defense dollar with a number of other pet service projects, including the Air Force’s Mach 2.8 FX and the Navy’s VFAX advanced interceptor proposals. Defense Dept. and industry officials generally agree that, at the most, only one of these aircraft will be given the green light to go into production.
The U. S. and West German V/STOL aircraft, known popularly as the U.S.-F.R.G. (Federal Republic of Germany) fighter, also recently has run afoul of intradepartmental politics inside the Pentagon, finding itself competing against a visionary concept dubbed the “international fighter” (AW&ST Mar. 13, p. 16). The “international fighter” is the brain child of the Defense Dept.’s Office of International Security Affairs (I.S.A.), which has Defense Secretary Robert S. McNamara’s mandate to promote and sell U. S. military hardware on the export market as one means of easing this country‘s balance-of-payments problem.
As envisioned by its I.S.A. backers, the “international fighter" would be a multimission aircraft developed on a multi-lateral basis and capable of replacing the FX, VFAX, the U.S.-F.R.G. V/STOL aircraft and the planned Anglo-French variable-geometry fighter. The U. S. would profit, its proponents contend, by producing and selling major components and sub-components to the other nations participating in the “international fighter” program - hopefully Great Britain, France and West Germany. Backers of the project also realize that it is doomed if the U.S.-F.R.G. fighter receives a production go-ahead, and at least some of them have begun a sniping campaign within the halls and conference rooms of the Pentagon in an effort to block it. This is being countered by supporters of the V/STOL aircraft in the Air Force and the Directorate of Defense Research and Engineering, where it has strong support in some quarters.
While the “international fighter“ plan reportedly has received some encouragement from McNamara. it probably is doomed in any event. Neither the British nor the French have displayed any great enthusiasm over the project because of the future production requirements of their own aerospace industries. The thought of design teams from four countries sitting down to draft and agree upon the criteria for a single aircraft to satisfy the requirements and concepts of all also is painful to technicians on both sides of the Atlantic who have attempted to participate in such programs in the past. The North Atlantic Treaty Organization in its heyday promoted a number of similar projects.
None were spectacularly successful, either financially or from a design point of view, and most broke down completely along nationalistic lines during the early stages of design debate.
To further complicate the probable futures of the U.S.-F.R.G. V/STOL aircraft and the “international fighter.” the British are urging the West Germans to abandon thoughts of both and join with the United Kingdom and France in the development and production of the proposed Anglo-French Variable-Geometry fighter. With the infusion of West German technical talent and financial backing, the British argue, the variable geometry fighter would be a strong contender on the export market against any probable U.S. entrants in the same category.
British Proposal
Backers of the U.S.-F.R.G. proposal here contend that the acceptance of the British proposal by West Germany would be a technical. and probably a financial, reversal for that country. The Anglo-French design, they say, is based largely on 1960 technology similar to that employed in the USAF/General Dynamics F-111A variable-geometry
fighter now nearing the operational stage and will be obsolete well before the end of its service life. The V/STOL aircraft, they contend, is being designed around 1966-67 technology, has a built-in growth potential and, if finally approved and adopted, will be capable of holding its own in the inventory of a first-line air force for 20 years at least.
As currently envisioned, the variable geometry U. S.-West German V/STOL would be a two-man tandem aircraft with a maximum gross weight of 40,000-45,000lb, placing it in the medium-weight fighter class. It would be able to attain near-supersonic speeds in the so-called “low-low-level" flight regime and have a built-in capability for self defense. In the self-defense mode, the aircraft should be more than a match for any of the current series of Soviet interceptors at altitudes below 20,000 ft. Above that level, however, it would be at a distinct disadvantage. since its present design stresses the attack role. Under USAF planning, the second crewman would be a rated pilot with additional training as a bombardier-navigator.
Informal studies are being made on possibilities of the conversion of the basic aircraft design into an interceptor to fill the mission as an “interim" FX fighter, including the use of higher thrust cruise engines with better powerplant maneuverability. Advocates of this approach contend that the aircraft could be employed to fill the gap until
a truly-advanced interceptor could be designed and produced. So far as the present FX concept is concerned, one veteran designer says. “it’s ridiculous to build an aluminum [Mach] 2.8 interceptor that won‘t even be able to overtake an advanced SST [supersonic transport]. It should be a titanium design and able to do better than Mach 3."
For the moment. however. the primary push within the U.S.-F.R.G. program is directed toward the design of a competent V/STOL strike fighter. Planned lift engine, should the aircraft reach maturity in either the prototype or production form. will be the result of a joint development effort currently under way under terms of a government- to-government agreement by the Allison Div. of General Motors Corp. and Rolls-Royce. Inc. The British firm is the definite technological leader in the project, based upon its past design and production experience in this field. Designation of the lift engine is the XV99-RA-1. The podded, retractable, swing-out lift engines probably will be located along either side of the fuselage beneath the variable-sweep wings. Present thinking calls for two engines on either side. The initial versions of the lift engine are scheduled to have a thrust-to-weight ratio of between 18—20:1, with a growth potential of 22—24:1. Both General Electric and Pratt & Whitney have contracts to investigate possible cruise-engine configurations for the aircraft.
Engines Retract
The lift engines. which would be retracted into the body of the fuselage when not in use, also could be vectored and modulated to permit STOL-type operations, with overload payload takeoffs possible from runways with lengths of 2,000 ft. or less. “This could be a tremendous airplane with an overload.” says one USAF officer working on the project. “In the STOL mode. it could be a big truck. We're still conducting studies to see just how good it could be, but it looks as though it will be better [so far as its overload capability is concerned] than any of the conventional aircraft we’ve had experience with." As for its ability to use runways of 2,000 ft. or less in the STOL mode, he adds that there are “many, many strips of that length throughout the world. You could take it almost anywhere, and, if you got in a corner, you could always use ‘V.'"
The next hurdle for the U.S.-ERG. program is to win approval from the two countries to go into the prototype construction stage. Its backers would like to see a total of 12 prototypes built on a joint basis to permit an extensive and prolonged series of field evaluation trials. It appears doubtful, however, that the Defense Dept. will agree to such a quantity, even if it should approve a move into the prototype stage when the current contract definition phase comes to an end late this fall.
The two contractors engaged in the contract definition phase are the Republic Aviation Div. of Fairchild Hiller Corp. and West Germany’s Entwicklungsring-Sud industry consortium. The two firms. selected from four US. and two German contractors that had competed in the earlier design phase, have established a joint management company to supervise the program, EWRFairchild International.
Cost Sharing
With the US. and West Germany sharing the costs on a 50-50 basis, the contract definition studies are being conducted by the two companies in Munich. and approximately 80 Republic engineers. programmers and management experts have been dispatched there to aid in the work. The joint military systems project office has been established at Wright-Patterson AFB, Ohio. About 20 German technicians have been assigned there on a temporary basis to assist in this portion of the project. In addition to these formal channels, the engine and airframe contractors are working closely together to assure that compatibility is maintained in these areas. USAF officials say Republic and
Entwicklungsring-Sud were selected primarily because of the similarity of their original designs. The West German firm's proposal called for a somewhat smaller
airframe, but both companies envisioned the use of swing-out lift engines and a variable-sweep wing. Major difference between the two was in the positioning of the engine inlets. Republic's design placed the main inlets on either side of the fuselage beneath the wing. Entwicklungsring - Sud‘s proposal called for them to be located on the top of the fuselage.
lnlet Problems
In view of the inlet problems encountered in the U. S. with several recent-model aircraft, including the F-111 and the Ling-Temco-Vought A-7A attack aircraft, the decision as to just where the inlets should be placed probably represents the major task confronting the team working on the contract definition phase. according to officials
here. “We’ve done a thorough analysis on the compatibility of the airframe and propulsion systems." says one. "We want to know exactly where the inlets should be before we make a decision, and we’re working hard on this problem to try and be sure that were right.” The contract definition phase studies, when completed, also will include recommendations as to how the production effort of any prototypes should be divided between the two countries and where the formal flight testing should be conducted. Final assembly probably would be carried out in each country. Flight testing also probably would be conducted in each. but it is expected that any high-speed evaluation trials would he held in the U. S. because of the lack of real estate for such purposes in West Germany.
Under present planning, the bilateral aspects of the agreement would come to an end at the conclusion of the prototype phase. Production of operational models of the aircraft by either country would be conducted on a unilateral basis—and this is one area in which the supporters of the “international fighter" cite the superiority of their plan.
The decision as to whether to take the step into the prototype phase is expected to be made by the end of the year. There are no available funds for this in the Defense Dept.’s Fiscal 1968 budget requests, but little, if any, money would be required before Fiscal I969.
Side view of the two-place Republic V/STOL fighter design shows the proposed position for the main cruise engine on the side of the fuselage beneath the variable-sweep wing in model above. Closed panels for the lift engine and swing-out arm can be seen farther forward. German industry participant in the program, Entwicklungsring-Sud, proposed that the main inlets be located on top of the fuselage. Final inlet positioning currently is under study in both U.S. and West Germany.
