Doak VZ-4

Doak VZ-4
Country	USA
Role	VTOL research convertiplane
First flight	25 February 1958
Built	1

The Doak VZ-4 (or Doak Model 16) was an American prototype Vertical Takeoff and Landing (VTOL) aircraft built in the 1950s for service in the United States Army. Only a single prototype was built, and the U.S. Army withdrew it from active trials in 1963.

Source: Doak VZ-4 on Wikipedia

Doak 16 VZ-4DA Walk Around
Photographer	Vladimir Yakubov
Localisation	US Army Transportation Museum, Fort Eustis
Photos	39

[

Doak 16 VZ-4DA 01

Doak 16 VZ-4DA 02

Doak 16 VZ-4DA 03

Doak 16 VZ-4DA 04

Doak 16 VZ-4DA 05

Doak 16 VZ-4DA 06

Doak 16 VZ-4DA 07

Doak 16 VZ-4DA 08

Doak 16 VZ-4DA 09

Click on a photo and use the mouse scroll to view all photos

Wait, Searching Doak VZ-4 for you…

General Characteristics and Role

The Doak 16, designated VZ-4DA by the U.S. Army, was an experimental Vertical Takeoff and Landing (VTOL) aircraft developed in the late 1950s. It was designed to explore the concept of a “convertiplane” that could take off and land vertically like a helicopter, but transition to forward flight like a conventional fixed-wing aircraft for faster cruise speeds. The Doak 16 used a unique propulsion system: a single engine drove two large, tilting ducted fans located at the wingtips. The entire fan assemblies could be rotated 90 degrees, a configuration known as a ducted fan tilt-wing. This technology was highly experimental, part of a push by the U.S. military to find practical VTOL solutions for observation and utility roles.

Property	Typical Value (VZ-4DA)
Role	Experimental VTOL Research Aircraft
National Origin	United States (U.S. Army)
Manufacturer	Doak Aircraft Company
First Flight	February 1958 (Conventional), February 1959 (Vertical)
Crew	2 (Pilot and Observer)
Length	9.75 m (32 ft 0 in)
Wingspan	4.88 m (16 ft 0 in)
Height	3.05 m (10 ft 0 in)
Gross Weight	1,450 kg (3,200 lb)

Powerplant and Propulsion System

Engine: 1 x Lycoming T53-L-1 turboshaft engine (later used in the Bell UH-1 Huey).
Power Output: 825 shp (615 kW).
Propulsion: Two tilting ducted fans (impellers), each connected to the engine via a transmission system to ensure synchronous rotation and thrust.
Flight Control: In vertical mode, control was provided by vanes located in the ducted fan exhaust. In forward flight, conventional rudder, elevator, and ailerons were used.
Maximum Speed (Cruise): Approximately 370 km/h (230 mph).
Service Ceiling: 6,096 m (20,000 ft).

Program Outcome and Legacy

Test Program: The VZ-4DA successfully demonstrated the transition from vertical to horizontal flight and back, validating the ducted fan tilt-wing concept.
Performance: Although the tests were successful, the VZ-4DA suffered from complex mechanical systems required to articulate the fans and transfer power, and it had a limited payload capacity.
Conclusion: The U.S. Army concluded the program in 1960. While the ducted fan concept showed promise, the Army ultimately shifted focus to lighter turboshaft helicopters (like the Bell UH-1) and other VTOL concepts that were considered more mechanically simple and scalable.
Preservation: The single prototype built, tail number 56-6942, is preserved and on display at the U.S. Army Transportation Museum at Joint Base Langley-Eustis, Virginia.