Origins The Avrocar was the ultimate result of a series of
blue skies research projects by designer
"Jack" Frost, who had joined Avro Canada in June 1947 after working for several British firms. He had been with
de Havilland from 1942 and had worked on the
de Havilland Hornet,
de Havilland Vampire jet fighter and the
de Havilland Swallow aircraft, where he had been the chief designer on the supersonic research project. At Avro Canada, he had worked on the
Avro CF-100 before creating a research team known as the "Special Projects Group" (SPG). Frost first surrounded himself with a collection of like-minded "maverick" engineers, then arranged for a work site. Initially ensconced in the "Penthouse", a derisive nickname for the executive wing of the Administration Building, the SPG was subsequently relocated to a
Second World War-era structure across from the company headquarters, the Schaeffer Building, that was secured with security guards, locked doors and special pass cards. At times, the SPG also operated out of the Experimental Hangar where it shared space with other esoteric Avro project teams. At the time, Frost was particularly interested in jet engine design and ways to improve the efficiency of the compressor without sacrificing the simplicity of the turbine engine. He found
Frank Whittle's "reverse flow" design too complex and was interested in ways to clean up the layout. This led him to design a new type of engine layout with the
flame cans lying directly outside the outer rim of the
centrifugal compressor, pointed outwards like the spokes on a wheel. Power for the compressor was drawn from a new type of turbine similar to a
centrifugal fan, as opposed to the more typical pinwheel-like design of conventional engines. The turbine drove the compressor using gearing, rather than a shaft. The resulting engine was arranged in the form of a large disk, which he referred to as a "pancake engine".
Project Y At the same time, the aircraft industry as a whole was becoming increasingly interested in
VTOL aircraft. It was expected that any future European war would start with a nuclear exchange that would destroy most airbases, so aircraft would need to operate from limited airbases, roads or even unprepared fields. Considerable research effort was put into various solutions to securing a second-strike capability. Some of these solutions included rocket-launched aircraft like the
zero-length launch concept, while many companies started work on VTOL aircraft as a more appropriate long-term solution. Frost felt the excellent performance of his new engine would be a natural fit for a VTOL aircraft due to its high expected
power-to-weight ratio. The problem was how to use the annular thrust to drive the aircraft forward, as well as the problem of fitting the very large engine into a suitable airframe. Frost suggested using a series of ducts and vents to redirect the thrust flowing out of the front of the engine towards the rear. In order to keep the pipes as short as possible, the design ported the thrust out along the leading edge of what was essentially a thick
delta wing. As the engine was disk-shaped, the triangular delta shape was pushed out near the front where it met the engine disk, producing a shape roughly like a
spade on a
playing card. As he continued these experiments, he found that the same thrust-direction system he intended for VTOL operations worked just as well for forward flight. In this case the disk shape was not of itself a good lifting surface, as it was neutral in terms of lift direction – that is, it would fly sideways as readily as it would fly forward. However, by modifying the airflow with the application of a small amount of jet thrust, the overall airflow over the craft could be dramatically altered, creating a sort of "virtual airfoil" of any needed configuration. For instance, by directing even a small amount of jet thrust down, a large mass of air would be pulled over the upper surface of the wing and dramatically augment the flow over the wing, creating lift. This appeared to offer a solution to one of the most vexing problems of the era, designing an aircraft that was effective at subsonic and
supersonic speeds. Subsonic lift is created by the airflow around the wing following
streamlines, but supersonic lift is generated by
shock waves at points of critical curvature. No single design could offer high performance for both regimes. The blown disk could attack this problem by being laid out for supersonic performance only, and then using jet thrust to modify subsonic airflow into a semblance of a normal wing. The resulting design would be tuned for high supersonic performance, have reasonable subsonic performance, and would also offer VTOL, all in a single design.
U.S. Involvement: Project 1794/WS 606A In late 1953, a group of U.S. defence experts visited Avro Canada to view the new CF-100 fighter jet. Somewhere along the way, Frost co-opted the tour and rerouted it to the Special Projects area where he proceeded to show off the Project Y mock-up and models and drawings (some never before seen by senior company officials) for a completely circular disk-shaped aircraft known as "Project Y-2". The USAF agreed to take over funding for Frost's Special Projects Group, and a contract for US$750,000 followed in 1955. By 1956, Avro management was interested enough to commit $2.5 million to build a "private venture" prototype. In March 1957, the Air Force added additional funding, and the aircraft became
Weapons System 606A. A wide variety of designs were studied for a VTOL fighter aircraft, The TS-140 was a canard type aircraft to be powered by four
Bristol Orpheus jet engines; the Navy instead selected
Bell Aircraft's
D-188A for its requirement. There was some debate about the concept within the USAF, as many groups were attempting to gain funding for their own pet projects, like
nuclear powered bombers. In a repeat of the earlier
Toronto Star release, in 1955 an extensive article appeared in
Look magazine that, among other claims, speculated that current
UFO sightings were Soviet-built saucers. The article went on to describe such an aircraft with diagrams that were clearly influenced by the Avro design. For testing purposes, a new engine consisting of six
Armstrong Siddeley Viper jet engines blowing across the outer rim of an
impeller was designed under the name PV-704, PV stood for Private Venture. The PV-704 was a stop-gap design built into a bunker-like building behind the Avro Experimental Test facility. It was intended to test various Project 1794 concepts and provide the USAF with test data to show the viability of the concept. The original plan to initially test the Viper Engine Rig was to have continued into free flight testing. Unfortunately, testing was anything but smooth; the test model suffered from hazardous oil leaks, resulting in three fires. It eventually got to the point that staff were afraid of the machine, even when safely ensconced in a booth constructed of bullet-proof glass and quarter-inch-thick steel. A final, disastrous and nearly lethal engine test in 1956 which involved a Viper jet engine running wild, convinced Frost that a less dangerous test vehicle was necessary.
Genesis of the Avrocar To gather flight data on the basic concept while the engine development continued, in 1958 Frost proposed building a smaller "proof-of-concept" test vehicle he called the
Avrocar. By this point, the U.S. Army was involved in a wide variety of experiments on smaller VTOL aircraft that would act as a "flying Jeep", and they became interested in Avro's concept as well. managed by the Air Force was awarded to Avro to build and test two Avrocars, which the Army referred to as the
VZ-9-AV (with AV standing for "Avro", an unusual departure from normal U.S. Army nomenclature), the latest in a series of "VZ" aircraft. Army interest in the Avrocar program was apparently very high. Bernard Lindenbaum of the Air Force Flight Dynamics Laboratory recalls a trip to Washington in the late 1950s to request additional funding for a study on helicopter drag reduction. Although the funding was approved, he overheard an Army General remark that the
Huey would be the last helicopter the Army would buy since the helicopter would be replaced by the Avrocar. Additional Air Force funding of approximately $700,000 (unexpended from the 606A program) was also moved to the Avrocar project. In March 1959, an additional $1.77 million contract was received for a second prototype. At rollout, projected performance was far in excess of the requirement, with a maximum speed, ceiling, range with payload, and hover out of ground effect with payload. Maximum takeoff weight with transition to forward flight out of ground effect was calculated to be , maximum weight with a transition in ground effect (GETOL) was . The USAF Project Office devoted to the Avro projects, recommended that the WS-606A and all related work (including the Avrocar) be cancelled. A "stop/go" work order came down and Frost was forced once more to try to rescue the project. In an elaborate effort, Frost made a resounding case for continuation of U.S. military funding. Late in May 1959, the USAF authorized Avro to continue the "flying saucer" programs. ==Design==