HILLER  XC-142

 Los primeros conceptos de aeronaves VTOL fueron tres diseños “sentados de cola”, el Lockheed XFV-1, el Convair XFY-1, y el Ryan X-13 Vertijet. Los conceptos posteriores trataron de mantener el fuselaje en posición normal haciendo girar el ala y /o los motores de la posición vertical a la horizontal. El LTV-Hiller-Ryan XC-142A era uno de estos diseños.

En 1959, el Ejército, la Marina y la Fuerza Aérea de los EE.UU. comenzaron a trabajar sobre el desarrollo de un prototipo V/STOL que pudiese utilizarse como helicóptero en misiones de transporte. Como resultado de esta evaluación tripartita, se decidió contratar a Vought para el diseño de 5 aparatos. El acuerdo se firmó a principios de 1962 especificando que el primer vuelo sería en julio de 1964.

Construidos por una unión de empresas, la Ryan y la Hiller, el XC-142 A estaba potenciado por cuatro turbinas General Electric T-64 que movían cuatro hélices Hamilton Standard de 15,5 pies.

Para ese época esta máquina era una de los transportes VTOL mas grandes, alcanzando una velocidad de crucero de 400 millas por hora en uno de sus vuelos de prueba. La carga se transportaba en un compartimiento de carga de 30 pies de largo por 7,5 pies de ancho y 7 pies de alto. La tripulación era de dos pilotos y un encargado de la carga. Podía volar hacia los costados hasta una velocidad de 40 Kts y soportar vientos de cola de hasta 20 Kts. El rolido se controlaba cambiando el ángulo de las hélices y el pitch por un rotor de cola (ver foto) de tres palas de 8 pies. La guiñada se lograba por alerones que tenían efectividad gracias al chorro de aire de las hélices. El ala podía girar 100 grados, permitiéndole a la aeronave efectuar vuelos suspendidos hacia atrás. El rotor de cola se podía plegar para reducir el largo del modelo y protegerse de eventuales accidentes durante la carga. Esta aeronave de 58 pies de largo, tenía una envergadura de 67 pies y era capaz de transportar hasta 32 soldados equipados ó 8000 libras de carga. Tenía una compuerta trasera y su peso máximo era de 41000 libras para despegues verticales o de 45000 libras para despegues cortos.

Realizó su primer vuelo convencional el 29 de septiembre de 1964, el primer vuelo estacionario el 29 de diciembre de 1964 y la primera transición el 11 enero de 1965.  Tuvo un accidente, debido a una falla del eje del rotor de cola, causando la muerte de tres personas. El XC-142 sufrió de excesivas vibraciones y era muy ruidoso, resultando de un alto trabajo para la tripulación.

El primer XC-142A (No. 2) fue enviado para las pruebas en julio de 1965. Durante el programa de evaluación, se volaron un total de 420 horas en 488 vuelos. El quinto XC-142A fue volado por  39 pilotos diferentes tanto militares como civiles. En 1966, mientras se llevaban a cabo las pruebas, la Fuerza Aérea le solicitó a Vought una propuesta de producir el C-142B.  Se propuso también una mejora para eliminar el requerimiento de compatibilidad para el transporte de la Marina. Un XC-142A fue terminado y enviado a la NASA para pruebas desde mayo de 1966 a mayo de 1970. Las perfomances no fueron tan buenas como las esperadas. Una de las limitaciones encontradas en la aeronave era su inestabilidad entre los 35 y 85 grados a bajas altitudes.

 The first VTOL concepts to be tried were three "tail sitting" airplanes, the Lockheed XFV-1, the Convair XFY-1, and the Ryan X-13 Vertijet. The next concept tried was to keep the main body of the aircraft in a conventional sense but tilt the wing and engines from the vertical to the horizontal. The LTV-Hiller-Ryan XC-142A was such an aircraft.

In 1959 the Army, Navy and Air Force began work on the development of a prototype V/STOL airplane that could augment helicopters in transport-type missions. If this prototype program were successful, an airplane based on the prototype experience could be developed. As a result of the Tri-Service evaluation of all proposals, the design development contract for five airplanes was awarded to Vought. The contract was signed in early 1962 with first flight specified for July 1964.

Built by an industrial team of LTV, Ryan and Hiller, the XC-142A was powered by four T-64 turboshaft engines built by General Electric and driving four 15.5-foot Hamilton Standard fiberglass propellers. The US Air Force was the developing agency for the Department of Defense, with the joint sponsorship of the Navy and Army.

The XC-142A was the largest and fastest VTOL transport airplane flying at that time. It achieved more than 400 miles per hour at cruise altitude during flight testing. The payload was carried in a cargo compartment that was 30 feet long, 7.5 feet wide and 7 feet high. Two pilots and one crewman/load master made up the flight crew. To accommodate adverse winds, the wing tilted upward more than 90 degrees which allowed the airplane to fly backward at 20 knots. By banking left or right, the airplane could fly sideways at 40 knots. Roll was controlled by differential propeller pitch, and pitch by an 8 ft three-bladed variable pitch tail rotor. Yaw was provided by ailerons powered by propeller slipstream. The wing could tilt through 100° allowing the XC-142 to hover in a tailwind. The tail rotor folded to the port side to reduce the stowage length and to protect against accidental damage during loading. This cargo aircraft was 58 ft long, had a wingspan of 67 ft and was capable of transporting 32 troops and gear or 8,000 lb of cargo. It had a rear loading ramp and had a maximum gross weight of 41,000 lb for a vertical take-off, or 45,000 lb for a short take-off.

It made its first conventional flight on 29 September 1964, first hover on 29 December 1964, and first transition on 11 January 1965. One crash occurred as a result of a failure of the drive shaft to the tail rotor, causing three fatalities. The XC-142 suffered from excessive vibration and noise, resulting in a high pilot workload.

The first XC-142A (No. 2) was delivered to the test team in July 1965. During the XC-142A program, a total of 420 hours were flown in 488 flights. The five XC-142A’s were flown by 39 different military and civilian pilots. In 1966, while operational tests were being performed, the Air Force requested Vought to submit a proposal for a production C-142B. A major improvement was proposed to eliminate the Navy carrier compatibility requirement. After reviewing the C-142B proposal, the tri-services management team could not develop a requirement for a V/STOL transport. XC-142A testing was terminated and one flying airplane was turned over to the National Aeronautics and Space Administration (NASA) for research testing from May 1966 to May 1970.

Performance was not as good as had been hoped for, partly due to the USAF waiving its weight-improvement program, and partly due to the propellors not delivering the expected thrust. The program called for the building of five prototypes, but cross-shaft problems, along with operator errors, resulted in a number of hard landings causing damage. One of the limitations found in the plane was an instability between wing angles of 35 and 80 degrees, encountered at extremely low altitudes. There were also high side forces which resulted from yaw and weak propeller blade pitch angle controls.

Characteristics
Características

Information
Información

Characteristics
Características

Information
Información

1964

4 G.E
T-64-1

3 / 32

3080 SHP each

23000 Lb

Ft

41500 Lb

Ft

204 Kts

25000 Ft

348 Kts

820 NM

Dimensions / Dimensiones

58,0 ft
17,67 m

67,0 ft
20,42 m

NA

8,0 ft
2,43 m