The Hiller X-18, begun in February 1957, used various components from existing aircraft. The fuselage was that of a Chase YC-122C transport. The two wing-mounted 7,100 eshp Allison T40-A-14 turboshafts came from the XFY-1/XFV-1 tailsitter (#23 and #24) program and could not be cross-linked. It had three engines, the two turboprops drove the 16 ft diameter counter-rotating three-bladed propellers and a 3,400 lb thrust Westinghouse J34 turbojet which produced pitch control thrust.

The 33,000 lb loaded X-18 underwent extensive ground tests beginning in December 1958, and made its first conventional flight on 24 November 1959. It made partial conversions with wing angles of up to 33° (relative to the fuselage) -- with a 17° nose-up attitude, the wings had an effective 50° degrees of tilt (relative to the flight path). The turboprop engines had electric pitch controls and were too slow to provide adequate response in hover. On the 20th flight it had a propeller pitch control problem at 10,000 ft and went into a spin. It was recovered before impact, but was grounded, having never achieved hover. It continued to test ground effects before it was damaged by a test stand failure.

 Source: AHS V/STOL Wheel


Data on design, manufacture and status

Design authority: Hiller Aircraft Corporation

Primary manufacturer: Hiller Aircraft Corporation

Parent type: No type defined

Aircraft status: No longer flying


Primary flight and mechanical characteristics

VTOL type: Convertiplane

Compound type: N/A

Lift configuration: Tilt wing (x4)

Dedicated control device: Thruster

Crew required: 2

Crew seating: Side-by-side

Landing gear: Wheels (non-retractable)

Layout and Dimensions

Data on aircraft size

Overall Dimensions
Overall Height:  
Overall Length:  
Overall Width:  
Airframe Dimensions
Airframe Length:  
Airframe Width:  
Airframe Height:  
Landing Gear Dimensions
Landing Gear Base:  
Landing Gear Track:  
Cabin Dimensions
Cabin Internal Height:  
Cabin Internal Length:  
Cabin Internal Width:  

Weights and Performance

Data on aircraft weight and flight characteristics

Max Gross Weight (ground): 14,969 kg 33,000 lb
Max Gross Weight (airborne):  
Max Take-off Weight: 14,969 kg 33,000 lb
Empty Weight:  
Useful Load:  
Empty Weight Fraction:  
Climb Performance
Max Rate of Climb:  
Hover Performance
Hover Ceiling IGE:  
Hover Ceiling OGE:  
Max Level Flight Speed:  
Never Exceed Speed:  
Service Ceiling:  
Range and Endurance
Max Range:  
Max Endurance:  

Engine Details

Aircraft powerplant (lift and/or propulsion)

Provided powerplant data is for uninstalled, sea level, static operations.

Number of engines: 3
Normal Ratings
Max continuous:  
Take-off / rated:  
OEI Ratings
OEI contingency:  
OEI continuous:  
OEI 30-second:  
OEI intermediate:  

Primary Lift Device

Data on primary lift devices such as main rotors

Main Rotor Characteristics
Direction of Rotation: Unknown
Hub Type:  
Main Rotor Blade Characteristics
Blade Construction:  
Blade Chord:  
Blade Tip Geometry:  
Blade Twist:  
Number of Blades:  
Main Rotor Derived Characteristics
Disc Area:  
Disc Loading:  
Main Rotor Blade Derived Characteristics
Blade area per blade:  
Tip Speed:  

Primary Control Device

Data on primary control devices such as tail rotors

Tail Rotor Characteristics
Configuration: Unknown
Direction of Rotation: Unknown
Tail Rotor Blade Characteristics
Number of Blades:  
Blade Construction: N/A
Blade Chord:  
Blade Twist:  
Tail Rotor Derived Characteristics
Disc Area:  
Tail Rotor Blade Derived Characteristics
Tip Speed:  
Blade Area (per blade):  

Related VFS Resources

Resources related to the X-18 , provided by the Vertical Flight Society.
Forum Proceedings
Vertiflite articles
Enter a search term in the box above.
Web files from
Enter a search term in the box above.
Webpages from
Enter a search term in the box above.

Related Public Resources

Resources related to the X-18 , provided by public sources across the internet.