Vertical Takeoff and Landing [VTOL] Aircraft
The Vertical Takeoff and Landing [VTOL] is thought of as a conventional type of aircraft with special features added to enable it to rise vertically during takeoff and to land from a vertical descent. The successful and imaginative employment by the military of the first VTOL type, the helicopter, is now part of aviation history. In the 1960s the military focus of attention was on a new VTOL type, the VTOL tactical fighter aircraft. Under the nomenclature V/STOL, it is necessary to arrange at the same time planes able to take off and land vertically (VTOL) or with the help of a short runway (STOL). The features of these two categories of aircraft are enough to différentiate them.
Progress in the development of a practical and capable VTOL fighter was exceedingly slow over the years, largely due to propulsion limitations and related problems. Among the first and most interesting of the VTOL fighter forerunners was the Chance Vought V-173 conceived in 1933 and first flown in 1942. Called the "Flying Pancake," the V-173 was a tail-sitter intended to rise vertically, then transition to normal flight attitude. Unfortunately, however, the airplane weighed 3000 pounds and had only 2000 pounds of propeller thrust. As a result, the Flying Pancake never made a vertical takeoff or landing, although it made some 210 successful flights in the conventional aircraft takeoff and landing mode. The project was canceled by the Navy in 1948 when its partial successes were overshadowed by conventional fighter aircraft powered by the newly developed turbojet engine. Interest waned, and efforts toward further development of this type of aircraft over the succeeding decade were sporadic.
On December 17, 1954, the North Atlantic Council approved MC 48, a key document in the evolution of NATO nuclear thought. MC 48 emphasized that NATO would have to use atomic weapons from the outset of a war with the Soviet Union whether or not the Soviets chose to use them first. War planners intended for fighter-bombers to destroy Soviet communication sites and airfields. By the same token, a Soviet nuclear attack could close NATO airfields and destroy its nuclear facilities and the high-performance aircraft, giving the Soviets air superiority from the outset of the war. This required NATO to develop aircraft that could take off from rough unprepared airstrips, and but obviously there must be some aircraft to take the necessary equipment, ammunition and petrol to these advanced fields.
V/STOL technology allows aircraft to disperse from fixed bases whenever a threat seems imminent, providing both a survival and a return strike capacity. Any attempt by the enemy to locate and destroy these dispersed forces (either close to or far from the main base) will compel him to dissipate a large proportion of his air power. This fact is emphasized when considering the type of operating surface that may be available to V/STOL aircraft - meadows, parts of active or disused airfields, roads, playing fields, light aircraft strips, railway stations, and woods. If the V/STOL aircraft is brought close to the area of operations, either on land or sea, there are possibilities for providing exceptionally rapid response to calls for ground support. There are other advantages to be gained from this. For example, rapid response can be provided whenever required without having to adopt an expensive airborne alert, and pilots can become very familiar with the operating area, thus reducing briefing times and navigation problems. Furthermore, in relative terms, more ordnance can be dropped per flying hour since so little time needs to be spent in transit.
Survivability is one of the aspects of operating flexibility that is derived from V/STOL, but it is of such fundamental importance that it should be amplified further. The ability to survive a pre-emptive attack and to operate during war are two essential prerequisites for any air force. V/STOL aircraft fulfill both these requirements; in the first instance dispersal greatly improves the chances of survival and, in the second, if they survive the initial attack on an airfield either by dispersal or by protection, it is unlikely that sufficient space could not be found for subsequent operations. Even in the worst case, where airfield logistics and runways were destroyed, whereas the conventional aircraft would be forced to wait for runway repairs, the V/STOL aircraft could depart in one of its various modes, fly to another source of fuel and weapons, and recommence operations. The flexibility that allows an aircraft not only to maneuver and fly to another airfield when its own is damaged but also to maneuver within its airfield perimeter to reach fuel and weapons is, without question, a unique capability.
After study of their needs, the military authorities of NATO defined three general types of V/STOL aircraft answering to the NBMR (NATO Basic Military Requirement) 3, 4 and 22. Work groups were created to examine the possibility of manufacture of joint prototypes. Work groups AC/169 and AC/170 were part of the groups formed by the Committee of Armaments the shortly after the recommendation of the Ministers for the defense of 31 March 1960 to draw up a list of approximately twenty projects lending themself to co-operation in production. There was created on June 24, 1960 (AC/74-R/89, note I) an Ad Hoc Mixed Working Group [AHMWG] on V/STOL Strike Reconnaissance aircraft (AC/169), centered on the NBMR-3, and an ad hoc mixed work group for V/STOL plane of transport of medium operating range (AC/170), centered on the NBMR-4. Moreover, an additional group of group AC/170, called AC/170 (STOL), was thereafter in charge of the study of the NBMR-22, for V/STOL plane of transport of short operating range.
During the period 1955-1970, more than 25 different VTOL and V/STOL non-rotary-wing configurations were test-flown by NATO countries. Although this numberof V/STOL concepts was probably significantly smaller than the number of new helicopters introduced in the same period, attention was focussed on them because of their novel operational capabilities and the diversity in the design of their propulsive, lift and flight control systems, not to mention their often notorious safety record. In response to the need for criteria which could more efficiently lead to a successful and capable V/STOL design, a succession of efforts was undertaken by NATO's AGARD (Advisory Group on Aeronautical Research and Development), NASA, and the US military.
By 1966 experimental application equipment for the preparation of remote landing and take-off sites for turbo-jet VTOL aircraft was designed, fabricated and demonstrated by LTV Aerospace Corp. Three full scale remote sites were prepared in England and the Federal Republic of Germany. Evaluation of these sites was accomplished with the P.1127 and the VJ101C-X2 aircraft respectively. These remote sites were prepared by spraying a modified chlorinated polyester resin and fiberglass roving over essentially unprepared ground. Modifications to the application equipment, further development of materials and fabrication techniques were made as a result of the experience gained in the preparation and evaluation of these remote sites. Preliminary remote site design criteria were developed for determining site thickness, site size and shape. Experimental pads were prepared over various soil types and tested using typical wheels and tires to obtain data for determining site strength requirements. A methodology for determining site size and shape was further refined by conducting downwash flow field studies using models of the P.1127, VJ101, XC-142 and DO-31 aircraft. Dynamic pressure data obtained during remote site evaluation were correlated with model test data. Logistics support tasks for VTOL site preparation and site operation were examined.
European leaders increasingly questioned whether American policy was indeed credible-would the United States, in fact, undertake a massive nuclear assault on the Soviet Union in the face of a European attack (as Charles de Gaulle famously said, "no U.S. President will exchange Chicago for Lyons"). After De Gaulle withdrew French military forces in March 1966 from NATO's defense structure in favor of pursuing his own small nuclear force, NATO planners within the Military Committee began calling for a fundamental reexamination of the massive retaliation strategy embodied in the decade-old MC 14/2. This led the issuance of MC 14/3 in January 1968, NATO's formal repudiation of massive retaliation and embraced Flexible Response. Under NATO's new strategy of "flexible response," its armies would try to hold the frontline close to the Inner-German Border, while its aircraft, which accounted for half of NATO's conventional fire-power, remorselessly pounded the attackers.
By 1968, resurgent interest in the VTOL fighter was in evidence. The aircraft industries of some six or more major countries are currently active in the testing, development, or production of VTOL aircraft. For example, West Germany and Italy were engaged in a joint venture in the development of a VTOL fighter. This project is now in its early stages and the prime contractors, Vereinigte Flugtechnische Werke (VFW) of Bremen, Germany, and Fiat Aircraft Company of Turin, Italy, established a development program that was intended to result in the initial construction and testing of six prototype V-191B tactical fighters by mid-1969. In France, a version of the well-known mach-2 strike fighter, the Mirage III, was converted for VTOL operations. In Great Britain, the Hawker Siddeley Company designed, developed, and placed into service the world's first production VTOL strike fighter, the P.1l27 Kestrel.
|Join the GlobalSecurity.org mailing list|