Doak Aircraft Company
Edmond R. Doak, Jr., a self-taught engineer, had been experimenting with disk shaped air-moving concepts, vertical takeoff and landing with ducted fans, since 1935 and work for Douglas Aircraft Company as Vice President.
In 1940, Edmond Doak founded the Doak Aircraft Company in Torrance, California. The company grew to 4,000 employees during World War II with subcontracts from every major American aircraft manufacturer. These included molded plywood fuselages for trainers such as the AT-6 and Vultee BT-13, aircraft doors, hatches and gun turrets for a multitude of aircraft.
The Doak Aircraft Company, known for its Doak VZ-4 (also known as the Model 16), was a company that designed and built experimental aircraft, specifically focusing on vertical takeoff and landing (VTOL) capabilities.
The three Doak disk models in the display case were experimental vertical takeoff and landing (VTOL) concept aircraft. Looking at the display case from left to right is the Doak G-3, Doak 11 and the Doak XF-1
The X-F1 project began in 1949 and construction was completed in 1950. Testing of the XF-1 disk was from 1950 to 1953 and was accomplished with a tether, typically a cable or wire, connecting the aircraft to a ground station. This tether can provide power to the aircraft. Tethered testing reduces the risk associated with full, free flight, especially during early development phases. The aircraft can be moved or hovered in a controlled manner allowing for testing of various parameters of thrust, handling, and performance characteristics. The tether can be used to vary the effective weight of the aircraft by varying the tension applied to the cable. The tether allows for precise control of the aircraft’s position and movement, facilitating data collection and experimentation of aircraft performance in ground effect and out-of-ground effect hover.
From 1950 to 1956, Doak Aircraft developed a flying disk Model 13 with tricycle landing gear, a two-seat cockpit, with Contra-Rotating Impellers and was powered via a gear box by a Wright 1820 Cyclone engine.
In 1954, after years of research with various disk-shaped air foil designs, Doak began work on the Model 15. This aircraft featured two ducted fans, one on each wing tip, which could rotate 90 degrees and allow the aircraft to climb or descend vertically and transition to horizontal flight. This change in design would lead to a U.S. Army research and proof of concept contract and resulted in the successful development of the Model 16 powered by a Lycoming turbine engine (Doak VZ-4). Flight testing began at Torrance Municipal Airport and Doak completed several tests by 1958. The Model 16 hovered for the first time on 25 February 1958 and the first transition from vertical to horizontal flight (and back again) took place on 5 May 1958. Although the prototype generally was successful, its short takeoff and landing performance was less than hoped for and it displayed a tendency to nose up while making the transition from vertical to horizontal flight.
Doak’s engineers believed that they could solve the prototype’s problems. After taxiing testing, 32 hours of flight testing in a test stand, and 18 hours of tethered hovering, the aircraft was transferred to Edwards Air Force Base, California in October 1958. It underwent another 50 hours of testing, in which it proved capable with the turbine engine of achieving a maximum speed of 230 mph and a cruise speed of 175 mph.
The U.S. Army accepted the prototype in September 1959, designated it the Doak VZ-4DA, and passed it to the NASA Langley Research Center in Hampton, Virginia, for further testing. When Doak laid off 90 percent of his employees late in 1960 due to a recession in the aircraft industry, Douglas Aircraft took over the project, purchased its patent rights and engineering files, and hired four engineers from Doak to continue work on the VZ-4DA.
Work continued on the VZ-4DA until 1963, when the U.S. Army decided that a helicopter would meet its VTOL requirements and shifted funding away from the design and testing of unconventional VTOL aircraft to the design and procurement of helicopters and discontinued trials of the VZ-4DA. The National Aeronautics and Space Administration (NASA), later acquired the aircraft and continued testing flights through 1972.
Only a single prototype VZ-4DA was built. In January 1973, the VZ-4DA was donated to the U.S. Army Transportation Museum at Fort Eustis, Virginia, where it was placed on public display with other aircraft in the museum’s outdoor Aviation Pavilion. In August 2024, the VZ-4DA was permanently transferred to the U.S. Army Aviation Museum.
