The Doak 16, which received the Army designation VZ-4, was built in 1957. It was 32 ft long, had a gross weight of 3,200 lb, a tandem two-seat cockpit, and a 16 ft wingspan. Each wing ended in eight-bladed 4 ft wide propellers within tilting ducts; they were powered by a single 860 bhp Lycoming YT53 engine.


The first flight was made on 25 February 1958. Transition from hover to 200 kt could be made in less than 20 seconds. Variable inlet guide vanes controlled roll in hover, and engine exhaust gases were deflected at the rear of the fuselage for pitch and yaw control. Deceleration and descent had to be carefully controlled in order to prevent the lip of the duct from stalling, as well as to manage a large upward pitching moment from the ducts acting as a wing at a high angle of attack. The Doak 16 suffered from a lack of control power, but completed over 50 hours of testing and proved the feasibility of the tilt duct concept.


The only example of the Type can be seen in the US Army Transportation Museum at Fort Eustis.


Source: AHS V/STOL Wheel


Data on design, manufacture and status

Design authority: Doak Aircraft Company, Inc.

Primary manufacturer: Doak Aircraft Company, Inc.

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 rotor/prop/duct (x2)

Dedicated control device: Other

Crew required: 1-2

Crew seating: Tandem

Landing gear: Wheels (non-retractable)

Overall Dimensions

Data on aircraft size

Engine Details

Aircraft powerplant (lift and/or propulsion)

Total number of engines: 1

Engine designation: Lycoming YT53 turbine

Engine manufacturer: Lycoming Engines

Weights and Performance

Data on aircraft weight and flight characteristics

Max Gross Weight (ground): 1452 kg (3200 lb)

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