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HILLER
HELICOPTERS INC.
HILLER X-18 |
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Hiller
Aircraft fue uno de los pioneros en programas VTOL luego de finalizada
la Segunda Guerra Mundial. Sus investigaciones apuntaron a las ventajas
derivadas del concepto de la inclinación del ala. Esto generó
suficiente interés en la Navy de USA y recibió un contrato en 1957
para la construcción de una aeronave de transporte de 4 toneladas. También
atrajo el interés de la Fuerza Aérea en 1954. Tres años ,mas tarde,
esta Fuerza reclama la construcción de un prototipo y premia a la compañía
con un contrato por 4 millones. Aún cuando el aparato fue construido
desde el vamos como una plataforma de experimentación, el X-18 definitivamente
constaba con un perfil de transporte. También sería la aeronave VTOL
mas grande construida fuera de época. El contrato
especificaba que tendría dos motores y además de su capacidad de
despegar y aterrizar verticalmente debería tener una velocidad de
alrededor de los 640 Km/h. Otra consideración especificaba que donde se
pudiera utilizar como avión en el despegue y aterrizaje pudiese
aumentarse su carga paga. El primer y único prototipo fue finalizado en
1958 y fue construido utilizando las técnicas de fabricación lo mas
convencionales posibles. El primer
vuelo se llevo a cabo el 24 de noviembre de 1959. Llevándose a cabo 20
vuelos en el programa, finalizando estos en julio de 1961, cuando se
presenta un problema con una de los controles de cambio de paso de una
de las hélices, sirve como principal razón para la cancelación del
programa. El hecho de que los motores no trabajasen en forma cruzada
contribuyó también a la finalización del programa. Pero después de
que los vuelos terminaran, el X-18 sirvió como base
para la aeronave de transporte XC-142. Durante sus
últimos días, el X-18 fue dañado cuando uno de los soportes de
las pruebas de tierra falló. Luego, el X-18, al igual que muchas
de otras aeronaves experimentales, fue desarmado y cortado. Además del
par de turbinas Allison T40-A-14, cada montante constaba de un motor eléctrico
Curtiss-Wright y dos hélices de tres palas, con un total de 11000 SHP,
además de un turbojet Westinghouse J-34 de 1530 Kg. localizado en la
cola, para proveer control sobre el pitch. Este motor era el mismo que
equipaba el Convair XFY-1 "Pogo" . La potencia
del motor auxiliar era desviada a través de un conducto que se
proyectaba en la parte trasera de la aeronave y finalizaba con una válvula
desviadora. Al aplicarse el empuje hacia arriba o hacia abajo, se mantenía
el control de pitch de la aeronave. Las
turbinas T40 eran enormes – 4,8m de diámetro- con las hélices
contrarotatorias. Los motores proporcionaban bastante sustentación,
proporcionándole al X-18 una perfomance excelente en la transición
del vuelo vertical al horizontal. El fuselaje, con 19,8 metros de largo, era una modificación de un Chase YC-122C (Fairchild C-123 Provider) con otras partes de un transporte R3Y. Su construcción no requirió de técnicas especiales, lo cual ahorró mucho tiempo y esfuerzo. El aparato tenía un peso vacío de 12150 Kg. y de 14850 Kg. como peso total. |
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Hiller Aircraft was one of the pioneers in VTOL flight
and investigated the possibilities of the phenomena following World War
II. Its investigations pointed to the advantages to be derived from the
Tilt-Wing concept. It generated enough interest from the Navy, with its
expertise receiving a contract in 1957 for a four-ton payload, tilt-wing
transport. The company's potential also attracted the interest of
the Air Force in 1954. Three years later, the Air Force pushed for the
construction of a prototype and a flight test program, and awarded the
company a $4 million contract to accomplish the awesome task. Even
though the plane was built from scratch as a research-gaining testbed,
the X-18 definitely carried the look of an era transport. It
would also be the largest VTOL aircraft built to date at the time. The contract called for a twin-engine, Tilt-Wing
convertiplane. In addition to its vertical take-off and landing
capabilities, the X-18 was also required to have a significant
forward speed capability of about 640km/h. Another consideration of the flexibility of the plane
was that where landing strips were available, the X-18 could be
used in a conventional take-off mode, resulting in an increased payload
capability. The model was to also be constructed using as much
conventional fabrication techniques as possible. The task was aided
greatly during its early phases by a series of wind tunnel tests at NACA
Langley, Virginia. The first, and only, prototype was completed in 1958,
and quickly became involved in an extensive ground test program. The first actual flight test took place on November 24,
1959. There would be twenty flights in the program, with the program
ending in July 1961. It was that final flight of the program that
actually spelled disaster. But after the flight testing was over, there was still
another important mission to be performed by the X-18. During
this phase, the plane would serve to generate a data base for the
four-engine XC-142 Tilt-Wing transport that would follow. During its final days, the X-18 would be damaged
when a ground test stand upon which it was mounted failed. Shortly
thereafter, the X-18 - like a number of the other X planes -
would be disassembled and cut up for scrap. Looking at the mechanicals of the X-18, it
quickly comes to light that this was an extremely complicated machine
and certainly was pushing the state-of-the-art for the time period. The propulsion system, although it wasn't immediately
evident when viewing the plane, carried three engines. Besides the
obvious pair of Allison T40-A-14 turboprops, each mounting a pair of
Curtiss-Wright turbo-electric three-bladed propellers and putting out a
total of just over 11000 horsepower, there was also a 1530-kg-thrust
Westinghouse J-34 turbojet located in the aft fuselage that provided the
greatly-needed pitch control. It was located in the aft fuselage. The
T40, by the way, was the same engine that was used in the Convair
XFY-1 "Pogo" Tail Sitter VTOL fighter. The thrust from this auxiliary engine was diverted
through a pipe that protruded out the rear of the aircraft and
terminated with an up-and-down diverter valve. By applying the thrust in
either an up-or-down direction, the devise was able to maintain the
craft's pitch control. The T-40 props were huge – 4.8m in diameter - with the
props geared to be counter-rotating. The engines provided significant
lift thrust, providing the X-18 with excellent performance
through transition from vertical to horizontal flight. Following
transition to its forward velocity mode, the X-18 acquired the
look of a conventional transport, and it was hard to even identify its
VTOL capability. The cockpit featured a standard cockpit layout, but
stability augmentation was built into the roll and pitch axes. Hydraulic
boost was used on the ailerons, and a jet diverter and a servo tab boost
on the rudder. The only additional control on the cockpit panel was a
lever to tilt the wing, which was mechanically locked in the full-down
position, but hydraulically locked when in the intermediate positions. The X-18 airframe certainly wasn't a from-scratch
project, but instead was derived from a montage of existing aircraft
parts and pieces. The main fuselage, which was 19.8m in length, was a
modified Chase XC-122C model with other parts coming from a R3Y
transport. Its construction did not require any unconventional
techniques or components, which resulted in a great time savings in the
overall project. The fuselage was actually cut in half during the
construction process and stretched to a length which was required to
meet the center of gravity and landing gear requirements. For simplicity
reasons, the tricycle landing gear was fixed in the deployed position.
During horizontal flight, the X-18 carried the look of a standard
transport, although the wings looked a bit stubby. The high-set 14.6m-span wing, though, was a new design,
with the engines nearly centered between the fuselage centerline and the
wingtips. Interestingly, there were no flaps, but ailerons, with the
actual tilting of the wing accomplished by a pair of hydraulic pistons.
The high-set wing was designed to rotate through a complete 90 degrees,
enabling a pure helicopter vertical transition. The X-18 weighed 12150kg empty and 14850kg
loaded. Compared to the other VTOL craft of the time period, the X-18
was a large aircraft and required each main Allison T-40 engine to lift
7430kg, as compared to the 5400 to 6300kg for each of the Tail-Sitter
VTOL projects. From the pilots' point-of-view, the X-18 was
rated as a fairly easy aircraft to learn. That came from the fact that
the cockpit controls were practically identical to any turboprop
transport of the period, the only addition being the wing-tilt lever. S.Markman & B.Holder
"Straight Up: A History of Vertical Flight", 2000
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Characteristics |
Information |
Characteristics |
Information |
First
Flight Primer Vuelo |
1959 |
Engine Motor |
2 Allison |
Seating
Capacity Plazas |
2 - ? |
Power Potencia |
11000 SHP |
Empty
Weight Peso Vacío |
12150 Kg |
Hover
Ceiling O.G.E. Estacionario O.G.E |
Ft |
Maximum
Weight Peso Máximo |
14850 Kg |
Hover
Ceiling I.G.E. Estacionario I.G.E |
Ft |
Vel.
Cruise Vel. crucero |
Kts |
Service
Ceiling Techo de Servicio |
Ft |
V.N.E. V.N.E |
225 Kts |
Maximum
Range (Std) Alcance (Std) |
400 NM |
Dimensions / Dimensiones |
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Total
Length Largo Total |
64,96 ft |
Propeller
Diameter Hélices Diámetro |
15,74 ft |
Envergadura Wing Span |
47,90 ft |
Tail
Rotor Diameter Diam. Rotor de Cola |
NA |
Copyright © 1999 / 2003