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Aviation History
1964
1964 - 2594.PDF
fUGHT 595 International, I October 1964 Two XV-5A fan-in-wing aircraft have been built, and the first is seen here hovering at Edwards AFB, California. Gross weight is 12,5001b, maximum and cruising Mach numbers 0.78 and 0.70, and ferry range 1,100 n.m. with ten per cent reserve V/STOL BY VERTIFAN By William T. Immenschuh, Chief Engineer, Ryan V/STOL Aircraft FOR almost 20 years, the Ryan Aeronautical Company hasbeen the leading US designer and producer of fixed-wingjet-powered V/STOL aircraft. The first programme was an engineering study of turbojet thrust control for vertical flight initiated in 1947 (Fig 1). Subsequently, Ryan has built and demon- strated the X-13 Vertijet, the first pure-jet VTOL (Fig 2); the VZ-3RY Vertiplane, a deflected-slipstream vehicle (Fig 3); and the XV-5A, the current lift-fan research aircraft based on the company's Vertifan concept (Fig 4). Also, Ryan is participating with Vought and Hiller in the XC-142A tri-Service tilt-wing transport pro- gramme (Fig 5). As a result of the technical and operational deficiencies recognized in various V/STOL concepts, Ryan began a study of the Vertifan concept in the mid-1950s. General Electric initiated a similar lift- fan study, and obtained the first hardware contract from the US Army Transportation Research Command (TRECOM) in 1957. The first propulsion system was produced in 1959 (Ryan fabricated the fan scrolls) and, to date, over 600hr of actual running time has been accumulated. In 1957, the USAF awarded an engineering study contract to Ryan, with GE a major subcontractor, to in- vestigate the application of lift-fan propulsion to various aircraft designs. Transports with gross weights ranging from 30,000 to 115,0001b, and a supersonic fighter were investigated (Fig 6). Subsequent to the completion of the study, the USAF embarked on the TFX programme and shelved V/STOL until the present time. However, in November 1961 Ryan won the competition to design, fabricate, and test the US Army XV-5A lift-fan research aircraft, with GE acting as prime contractor under a TRECOM contract. Republic Aviation is associated with Ryan in the flight- test programme. The National Aeronautics and Space Administra- tion has contributed wind-tunnel investigations, and the USAF is supplying the J85 engines and diverter valves. The basic parts of the propulsion system (Fig 4) consist of the jet engine, diverter valve, tailpipe, scroll, fan, fan inlet doors and exit louvres. During hover, the diverter valve directs the engine exhaust to small turbine blades around the periphery of the fan. For hover, the fan inlet doors are open and the exit louvres are vertical. For transition, the exit louvres direct the fan efflux aft, producing not only lift but also forward thrust. After the aircraft stalling speed is Passed, the diverter valve is closed and the exhaust directed out of the tailpipe in a conventional manner. The wing fan doors close and the aircraft flies as a conventional jet aeroplane until landing, when the sequence is reversed. In considering V/STOL aircraft design in general, Fig 7 shows a spectrum on which all known V/STOL concepts can be located. Thrust or lift T is equal to the product of mass-flow and velocity (T = a>V), while power is afunction of velocity squared I p = I. Any vehicle producing aerodynamic thrust is governed by these principles. At one end of the spectrum, it may be seen that rotor craft are by far the most efficient hovering vehicles but are limited in their forward speed. At the other end of the spectrum, pure jet VTOL aircraft are shown to be the most inefficient hovering vehicles but, conversely, are not limited in forward speed. This is easily under- stood when it is considered that a helicopter accelerates an air mass Fig I One of the company's first jet-lift experiments was the tethered flight of this Allison )33 turbojet equipped with jet deflec- tion and bleed-air "puffer jets" for control purposes
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