Doak VZ-4

Doak VZ-4
Državi	Zda
Vlogo	VTOL raziskovalni konvertiplan
Prvi let	25. februar 1958
Zgrajena	1

V Doak VZ-4 (ali Doak Model 16) je bil ameriški prototip Vertical Takeoff and Landing (VTOL) letalo, zgrajeno v 50. Zgrajen je bil le en prototip, 1963 pa ga je vojska ZDA umaknila iz aktivnih poskusov.

Vir: Doak VZ-4 na Wikipediji

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

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Doak 16 VZ-4DA 01

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Doak 16 VZ-4DA 09

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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)
Vlogo	Experimental VTOL Research Aircraft
National Origin	United States (U.S. Army)
proizvajalec	Doak Aircraft Company
First Flight	February 1958 (Conventional), February 1959 (Vertical)
Posadke	2 (Pilot and Observer)
Dolžina	9.75 m (32 ft 0 in)
Peruti	4.88 m (16 ft 0 in)
Višina	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.

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