X-18

Specifications

Company- Hiller Aircraft
Type- Testbed for large tilt-wing S/VTOL aircraft designs.
Goals- Explore large VTOL vehicles.
Primary Testing Facility Research- Edwards AFB
Dimensions- Span- 48 ft, 0 in; Length- 63 ft, 0 in; Height: 24 ft, 7 in
Max Speed- 253 MPH
Range- N/A
Max Altitude- 35,300 ft
Power Plant- One Westinghouse J34 turbojet engine with 3,400 lbf and two Allison YT40-A-14 turboprop engines with 5,500 hp each
Thrust- N/A
Weights- Empty: 26,786 lbs; Maximum: 33,000 lbs
Payload- N/A
Flights- 20
Number of Prototypes Built- 1
Project Tenure- 1959-1961
Project Status- Cancelled

Information

The X-18 was an experimental cargo transport aircraft designed to be the first testbed for tiltwing and STOVL (short take off and vertical landing) technology.

Design work started in 1955 by Stanley Hiller Jr and Hiller Aircraft Corporation received a manufacturing contract and funding from the U.S. Air Force to build the only X-18 ever produced.

To speed up construction and conserve money the plane was constructed from scavenged parts including a Chase C-122 Avitruc fuselage and the turboprops came from the Lockheed XFV-1 and Convair XFY-1 Pogo experimental airplanes program. The tri-bladed counter-rotating propellers were a giant 16 ft (4.8 m) across. The Westinghouse turbojet engine had its exhaust diverted upwards and downwards at the tail to give the plane pitch control at low speeds.

The first test flight was on November 24, 1959, ultimately recording 20 flights out of Edwards AFB. A number of problems plagued the X-18 including being susceptible to wind gusts when the wing rotated, acting like a sail. In addition the turboprop engines were not cross-linked, so the failure of one engine meant the airplane would crash.

On the 20th and final flight in July 1961, the X-18 had a propeller pitch control problem when attempting to hover at 10,000 ft and went into a spin. The crew regained control and landed, but the X-18 never flew again. However ground testing of the tiltwing concepts continued. Eventually a test stand that the plane was mounted on failed and the plane was severely damaged in the fall. The program was finally cancelled on January 18, 1964 and the X-18 was cut up for scrap.

** Information provided by Wikipedia **