The Avro Canada VZ-9 Avrocar was a
VTOL
A vertical take-off and landing (VTOL) aircraft is one that can take off and land vertically without relying on a runway. This classification can include a variety of types of aircraft including helicopters as well as thrust-vectoring fixed-win ...
aircraft developed by
Avro Canada
Avro Canada was a Canadian aircraft manufacturing company. It was founded in 1945 as an aircraft plant and within 13 years became the third-largest company in Canada, one of the largest 100 companies in the world, and directly employing over 5 ...
as part of a secret U.S. military project carried out in the early years of the
Cold War
The Cold War is a term commonly used to refer to a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc. The term '' cold war'' is used because the ...
. The Avrocar intended to exploit the
Coandă effect
The Coandă effect ( or ) is the tendency of a fluid jet to stay attached to a convex surface. ''Merriam-Webster'' describes it as "the tendency of a jet of fluid emerging from an orifice to follow an adjacent flat or curved surface and to ent ...
to provide lift and thrust from a single "turborotor" blowing exhaust out of the rim of the disk-shaped aircraft. In the air, it would have resembled a
flying saucer
A flying saucer (also referred to as "a flying disc") is a descriptive term for a type of flying craft having a disc or saucer-shaped body, commonly used generically to refer to an anomalous flying object. The term was coined in 1947 but has g ...
.
Originally designed as a
fighter-like aircraft capable of very high speeds and altitudes, the project was repeatedly scaled back over time and the
U.S. Air Force
The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal ...
eventually abandoned it. Development was then taken up by the
U.S. Army
The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, cla ...
for a tactical combat aircraft requirement, a sort of high-performance
helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...
.
[Milberry 1979, p. 137.] In flight testing, the Avrocar proved to have unresolved thrust and stability problems that limited it to a degraded, low-performance
flight envelope
In aerodynamics, the flight envelope, service envelope, or performance envelope of an aircraft or spacecraft refers to the capabilities of a design in terms of airspeed and load factor or atmospheric density, often simplified to altitude. The t ...
; subsequently, the project was cancelled in September 1961.
Through the history of the program, the project was referred to by a number of different names. Avro referred to the efforts as Project Y, with individual vehicles known as Spade and Omega. Project Y-2 was later funded by the U.S. Air Force, who referred to it as WS-606A, Project 1794 and Project Silver Bug. When the U.S. Army joined the efforts it took on its final name "Avrocar", and the designation "VZ-9", part of the U.S. Army's VTOL projects in the VZ series.
Design and development
Origins
The Avrocar was the ultimate result of a series of
blue skies research
Blue skies research (also called blue sky science) is scientific research in domains where "real-world" applications are not immediately apparent. It has been defined as "research without a clear goal"
and "curiosity-driven science". It is someti ...
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
The de Havilland Aircraft Company Limited () was a British aviation manufacturer established in late 1920 by Geoffrey de Havilland at Stag Lane Aerodrome Edgware on the outskirts of north London. Operations were later moved to Hatfield in H ...
from 1942 and had worked on the
de Havilland Hornet
The de Havilland DH.103 Hornet, developed by de Havilland, was a fighter aircraft driven by two piston engines. It further exploited the wooden construction techniques that had been pioneered by the de Havilland Mosquito. Development of the ...
,
de Havilland Vampire
The de Havilland Vampire is a British jet fighter which was developed and manufactured by the de Havilland, de Havilland Aircraft Company. It was the second jet fighter to be operated by the Royal Air Force, RAF, after the Gloster Meteor, and ...
jet fighter and the
de Havilland Swallow
The de Havilland DH 108 "Swallow" was a British experimental aircraft designed by John Carver Meadows Frost in October 1945. The DH 108 featured a tailless, swept wing with a single vertical stabilizer, similar to the layout of the wartime G ...
aircraft, where he had been the chief designer on the supersonic research project.
[Milberry 1981, p. 19.]
At Avro Canada, he had worked on the
Avro CF-100
The Avro Canada CF-100 Canuck (affectionately known as the "Clunk") is a Canadian twinjet interceptor/ fighter designed and produced by aircraft manufacturer Avro Canada. It has the distinction of being the only Canadian-designed fighter to e ...
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
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
-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
Air Commodore Sir Frank Whittle, (1 June 1907 – 8 August 1996) was an English engineer, inventor and Royal Air Force (RAF) air officer. He is credited with inventing the turbojet engine. A patent was submitted by Maxime Guillaume in 1921 for ...
'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 can
A flame (from Latin ''flamma'') is the visible, gaseous part of a fire. It is caused by a highly exothermic chemical reaction taking place in a thin zone. When flames are hot enough to have ionized gaseous components of sufficient density they a ...
s lying directly outside the outer rim of the
centrifugal compressor
Centrifugal compressors, sometimes called impeller compressors or radial compressors, are a sub-class of dynamic axisymmetric work-absorbing turbomachinery.
They achieve pressure rise by adding energy to the continuous flow of fluid through th ...
, 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
A centrifugal fan is a mechanical device for moving air or other gases in a direction at an angle to the incoming fluid. Centrifugal fans often contain a ducted housing to direct outgoing air in a specific direction or across a heat sink; such a ...
, 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."
[''Avrocar''... 2002] The jet thrust exited from around the entire rim of the engine, and this presented problems trying to adapt the design to a typical aircraft.
Project Y
![Project Y mockup colour](https://upload.wikimedia.org/wikipedia/commons/f/f2/Project_Y_mockup_colour.jpg)
At the same time, the aircraft industry as a whole was becoming increasingly interested in
VTOL
A vertical take-off and landing (VTOL) aircraft is one that can take off and land vertically without relying on a runway. This classification can include a variety of types of aircraft including helicopters as well as thrust-vectoring fixed-win ...
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
The zero-length launch system or zero-length take-off system (ZLL, ZLTO, ZEL, ZELL) was a method whereby jet fighters and attack aircraft could be near-vertically launched using rocket motors to rapidly gain speed and altitude. Such rocket boost ...
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
Power-to-weight ratio (PWR, also called specific power, or power-to-mass ratio) is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measuremen ...
. 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
A delta wing is a wing shaped in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta (Δ).
Although long studied, it did not find significant applications until the Jet Age, when it proved suitabl ...
. 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
A spade is a tool primarily for digging consisting of a long handle and blade, typically with the blade narrower and flatter than the common shovel. Early spades were made of riven wood or of animal bones (often shoulder blades). After the a ...
on a
playing card
A playing card is a piece of specially prepared card stock, heavy paper, thin cardboard, plastic-coated paper, cotton-paper blend, or thin plastic that is marked with distinguishing motifs. Often the front (face) and back of each card has a fi ...
.
The engine was disk shaped and its intake was positioned in the middle, which meant the engine air intakes had to be located near the middle of the wing. In the Ace design, these were located just to the front of the centre on the top and bottom of the aircraft. The cockpit was positioned over the main bearing, behind the intakes. A "spine" on the top and bottom ran from the cockpit area to the rear edge of the aircraft. Several other versions of the basic layout were also studied, including the "Omega" which was more disk-like as it cut away the rear portions of the delta wing as well.
For VTOL operations the aircraft was expected to sit pointed up, supported by long landing legs that extended out of the spine. Landing would be accomplished at a very high angle, making visibility during the approach very difficult. A number of other VTOL experiments of the era attempted various solutions to this problem, including rotating pilots seats and cockpits, but none proved very effective. Another problem with various VTOL experiments was that stability in a hover was difficult to arrange, although not entirely unexpected. A solution to this problem would require the thrust to be directed downward from a larger area, as it is in a helicopter, where the lift is supplied over the entire area of the rotor disk.
Most designers turned to bleeding off air from the engine's compressor, and directing that through pipes arranged around the aircraft. Frost's engine design used such a large number of nozzles that such an arrangement would not be to easy to build.
In 1952, the design was advanced enough that the Canadian
Defence Research Board
Defence Research and Development Canada (DRDC; french: Recherche et développement pour la défense Canada, ''RDDC'') is a special operating agency of the Department of National Defence (DND), whose purpose is to provide the Canadian Armed Forces ...
funded the effort with a CAN$400,000 contract. By 1953, a wooden mock-up of Project Y was completed, of which only images remain. It appears the project was considered too costly within the military establishment, which was at the time involved in several extremely expensive air defense projects. On 11 February 1953, a story on the project was leaked to the
Toronto Star
The ''Toronto Star'' is a Canadian English-language broadsheet daily newspaper. The newspaper is the country's largest daily newspaper by circulation. It is owned by Toronto Star Newspapers Limited, a subsidiary of Torstar Corporation and part ...
along with images of the Omega design, apparently in order to gain further funding. Five days later, the Minister for Defence Production informed the House of Commons that Avro was indeed working on a "mock-up model" of a flying saucer, capable of flying at and climbing vertically. Nevertheless, further funding was not forthcoming.
Project Y-2: the "flat-riser"
![John Frost colour](https://upload.wikimedia.org/wikipedia/commons/f/fc/John_Frost_colour.jpg)
While Project Y continued, Frost had meanwhile become interested in the
Coandă effect
The Coandă effect ( or ) is the tendency of a fluid jet to stay attached to a convex surface. ''Merriam-Webster'' describes it as "the tendency of a jet of fluid emerging from an orifice to follow an adjacent flat or curved surface and to ent ...
, where fluid flows will follow strongly convex shapes, something that might be unexpected at first glance. Frost felt the effect could be used with his engine design to produce a more practical VTOL aircraft, the exhaust flowing outward over the upper surface of the aircraft and then being directed downward over a flap-like arrangement. This would produce a lift force around the entire edge of the aircraft, allowing it to land "flat". He produced a number of small experimental designs using compressed air in place of an engine in order to select a suitable airframe shape, and eventually decided that a disk was the best solution.
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
Supersonic speed is the speed of an object that exceeds the speed of sound ( Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...
speeds. Subsonic lift is created by the airflow around the wing following
streamline
Streamline may refer to:
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* Streamline Air, American regional airline
* Adobe Streamline, a discontinued line tracing program made by Adobe Systems
* Streamline Cars, the company responsible for making the Burney car
Engineering
...
s, but supersonic lift is generated by
shock wave
In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a med ...
s 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
![Models](https://upload.wikimedia.org/wikipedia/commons/b/bd/Models.jpg)
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,
all revolved around the disk shape, leading to the Project 1794 involving a supersonic large disk fighter aircraft. The concept proceeded to wind tunnel testing with a variety of scale models. It featured a raised section in the middle over the engine that contained the cockpit and a series of rectangular intakes that provided air to the engine during low-speed flight. For supersonic flight, the upper intakes were closed using
louver
A louver (American English) or louvre (British English
British English (BrE, en-GB, or BE) is, according to Lexico, Oxford Dictionaries, "English language, English as used in Great Britain, as distinct from that used elsewhere". Mor ...
s and air was instead provided from a separate supersonic intake along the front of the raised section. Frost's performance estimates for the concept were for a potential of
Mach 3.5 at altitudes.
As Project 1794 was developed,
Avro Canada
Avro Canada was a Canadian aircraft manufacturing company. It was founded in 1945 as an aircraft plant and within 13 years became the third-largest company in Canada, one of the largest 100 companies in the world, and directly employing over 5 ...
proposed a version of the "Project Y", the TS-140, to meet the
United States Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
's Specification TS-140 for a
VTOL
A vertical take-off and landing (VTOL) aircraft is one that can take off and land vertically without relying on a runway. This classification can include a variety of types of aircraft including helicopters as well as thrust-vectoring fixed-win ...
fighter aircraft in 1956; it was rejected by the Navy. The TS-140 was a canard type aircraft to be powered by four
Bristol Orpheus
The Bristol Siddeley Orpheus was a single-spool turbojet developed by Bristol Siddeley for various light fighter/trainer applications such as the Folland Gnat and the Fiat G.91. Later, the Orpheus formed the core of the first Bristol Pegasus ...
jet engines; the Navy instead selected
Bell Aircraft
The Bell Aircraft Corporation was an American aircraft manufacturer, a builder of several types of fighter aircraft for World War II but most famous for the Bell X-1, the first supersonic aircraft, and for the development and production of many ...
'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
The ''Toronto Star'' is a Canadian English-language broadsheet daily newspaper. The newspaper is the country's largest daily newspaper by circulation. It is owned by Toronto Star Newspapers Limited, a subsidiary of Torstar Corporation and part ...
'' release, in 1955 an extensive article appeared in
''Look'' magazine that, among other claims, speculated that current
UFO
An unidentified flying object (UFO), more recently renamed by US officials as a UAP (unidentified aerial phenomenon), is any perceived aerial phenomenon that cannot be immediately identified or explained. On investigation, most UFOs are id ...
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
The Armstrong Siddeley Viper is a British turbojet engine developed and produced by Armstrong Siddeley and then by its successor companies Bristol Siddeley and Rolls-Royce Limited. It entered service in 1953 and remained in use with the Royal ...
jet engines blowing across the outer rim of an
impeller
An impeller or impellor is a rotor used to increase the pressure and flow of a fluid. It is the opposite of a turbine, which extracts energy from, and reduces the pressure of, a flowing fluid.
In pumps
An impeller is a rotating component ...
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.
Frost pitched his smaller design both as a prototype of a vehicle suitable for the Army's needs, as well as an aerodynamic testbed for the WS-606. Initial performance requirements for the Avrocar were a ten-minute hover capability in ground effect and range with a payload.
![Army Avrocars 02](https://upload.wikimedia.org/wikipedia/commons/2/2f/Army_Avrocars_02.jpg)
The new plan appeared to make everybody happy, and a $2 million joint-services contract
[Harding 1999, p. 74.] 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 Huey, used as a given name, is a variant of Hughie. It may refer to:
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* Huey Lewis ...
would be the last helicopter the Army would buy since the helicopter would be replaced by the Avrocar.
[Lindenbaum, Bernard and William Blake. ''The VZ-9 Avrocar'']
THE VZ-9 AVROCAR
. Retrieved: 17 February 2007. Note: Much of the discussion of the control systems and stability problems are taken from this source.
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 .
Just as the first working test models were being manufactured, disaster struck. The Canadian government cancelled the Avro
CF-105 Arrow
The Avro Canada CF-105 Arrow was a delta-winged interceptor aircraft designed and built by Avro Canada. The CF-105 held the promise of Mach 2 speeds at altitudes exceeding and was intended to serve as the Royal Canadian Air Force's (RCAF) ...
program on "Black Friday," 20 February 1959. The ensuing result was the lay-off of almost all Avro Canada employees, including those with the Special Projects Group. However, three days following the announcement of the Arrow cancellation, many of the Special Projects employees were rehired. But it wasn't quite business as usual. The team now included people from the CF-100 and CF-105 teams and the Special Projects Group was moved into the main building, which was nearly empty. As well, company "brass" became more involved in the group's operations.
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
The Avrocar was a disk-shaped aircraft with the same basic shape as a
frisbee
A frisbee (pronounced ), also called a flying disc or simply a disc, is a gliding toy or sporting item that is generally made of injection-molded plastic and roughly in diameter with a pronounced lip. It is used recreationally and competitive ...
, the upper surface of the disk being fairly curved, and the bottom much less so. The disk was in diameter and thick.
The main structural truss was a large equilateral triangle, to which the various components were attached. The 124-blade "turborotor" sat in the center of the triangle, with most of the rotor's thrust directed straight down through an opening in the lower surface, but some was bled off to power the control system running along the outer rim of the disk.
[Rogers 1989, p. 84.]
![Avrocar schematic (high resolution)](https://upload.wikimedia.org/wikipedia/commons/e/e6/Avrocar_schematic_%28high_resolution%29.jpg)
Power for the rotor was provided by three
Continental J69-T-9
The Teledyne CAE J69 was a small turbojet engine originally produced by Teledyne Turbine Engines, Continental Aviation and Engineering (CAE) under license from Safran Helicopter Engines, Turbomeca. The J69 was a development of the Turbomeca Marbo ...
jet engines attached to the truss. Each engine had its own fuel and oil tanks and other support systems, although it was expected these would be interconnected in future models. The majority of the airframe was made of aluminum with an empty weight of .
[Campagna 1998, p. 68.] The undercarriage of the Avrocar was rudimentary with three small castoring wheels mounted on "stub" shafts; a set of skids was substituted later in testing although they were not normally fitted.
[Winchester 2005, p. 69.]
Pilot control was entirely through a single side-mounted control stick. Pitch and roll were controlled through conventional fore-aft and side-to-side motions, while yaw could be controlled by twisting the stick. No mechanical linkages were used, the stick instead controlled the flow of high pressure air around the craft, which either directly attached to various control surfaces, or indirectly through local cable linkages to replace controls that were intended to be cable-actuated (like throttle controls on the engines).
The attitude/thrust control system consisted of a large ring situated outside of the main disk, shaped roughly like a rounded triangle with the flat surface on the "inside." Viewing the craft from the side, the control flap is almost invisible, appearing in its neutral position to blend into the profile. The pilot's controls moved the ring in relation to the rest of the craft, affecting the airflow moving outward from the center of the craft. Vertical lift could be increased by moving the entire ring down, which would produce more airflow over its upper surface, which would then bend down over this surface toward the ground. Tilting the ring resulted in asymmetric thrust for directional control.
It was discovered that the craft was inherently unstable in forward flight, as the aerodynamic
center of pressure was well forward of the
center of gravity
In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weight function, weighted relative position (vector), position of the distributed mass sums to zero. Thi ...
. The Avrocar thus included a mechanical
stability augmentation system
An autopilot is a system used to control the path of an aircraft, marine craft or spacecraft without requiring constant manual control by a human operator. Autopilots do not replace human operators. Instead, the autopilot assists the operator' ...
that was independent of the pilot's controls. The turborotor had a fairly large
angular momentum
In physics, angular momentum (rarely, moment of momentum or rotational momentum) is the rotational analog of linear momentum. It is an important physical quantity because it is a conserved quantity—the total angular momentum of a closed syst ...
and was intended to act as a powerful
gyroscope
A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rota ...
, providing a "normal" direction of flight. Control cables attached to the base of the rotor would be pulled when the craft moved in relation to the rotor, actuating the control surfaces to counteract the motion.
The vehicle was manned by a crew of two, positioned in separate cockpits squeezed into empty areas in the airframe. In practice, only one pilot was usually on board during testing; a number of flights were made with an observer in the second cockpit. Until control problems were completely solved, the Avro test pilots acquired a "touch" for the extremely sensitive control inputs and Avro Aircraft Chief Development Test Pilot Potocki was eventually able to demonstrate a "hands-off" flight. Nonetheless, Avro test pilot Peter Cope, USAF project pilot Walter J. Hodgson and NASA's
Ames Research Center
The Ames Research Center (ARC), also known as NASA Ames, is a major NASA research center at Moffett Federal Airfield in California's Silicon Valley. It was founded in 1939 as the second National Advisory Committee for Aeronautics (NACA) laborat ...
Chief Test Pilot Fred J. Drinkwater III, who all flew the Avrocar, considered it still a tricky vehicle to fly. Drinkwater likened a flight in it to "balancing on a beach ball."
[Avrocar: Saucer Secrets from the Past, 2002. .]
Operational history
Testing
![Avrocar at factory](https://upload.wikimedia.org/wikipedia/commons/8/86/Avrocar_at_factory.jpg)
The first Avrocar, #''58-7055'', rolled out of the Avro Malton factory in May 1959. From 9 June to 7 October 1959, it was tested in a static hover rig. Unfortunately, hot gas from the exhaust was found to mix back into the intakes in hover, reducing engine thrust. In addition, the fan generated lift only from a small area of its surface, lowering overall thrust available. The ducts also proved to have higher losses than expected, and a series of modifications were not able to solve this problem to any large degree. These problems reduced maximum lift at higher altitudes out of the ground effect to , less than the empty weight of the aircraft at . This meant the aircraft would be incapable of hovering out of the ground effect. Following these tests, the vehicle was sent to
NASA Ames
The Ames Research Center (ARC), also known as NASA Ames, is a major NASA research center at Moffett Federal Airfield in California's Silicon Valley. It was founded in 1939 as the second National Advisory Committee for Aeronautics (NACA) laborat ...
for a wind tunnel testing.
The second, #''59-4975'', was completed August 1959. On 29 September, the first attempt to hover was made with the Avrocar tethered to the ground. After the vehicle became airborne, an uncontrollable roll and pitch-coupled oscillation started that forced each of the three wheels into the ground in turn. The pilot, W. D. "Spud" Potocki, immediately shut down all engines. Changes were made to the stability system to provide more control authority, while new tethers were investigated to improve the ability to control these sorts of problems.
As testing continued it became clear that the problem was inherent to the design, and the engineers started referring to the effect as "hubcapping," so-named as it appeared similar to a hubcap spun on the ground.
Investigations into the effect revealed what was causing the problem. While in the ground effect, the high-pressure air under the craft was trapped, filling the entire area and thus providing a stable base. When the craft rose out of the ground effect, the air formed itself into a single narrow column, described by Frost as "tree trunking". At intermediate altitudes the craft would momentarily transition from one regime to the other, during which time one side of the vehicle would be entirely supported while the support was disappearing under the other. This led to a strong pitching motion towards the unsupported side. As soon as this occurred that side would approach the ground and re-establish the supporting air, while the other side would then be raised above this limit. This process would repeat itself, with the craft rolling from side to side. Modifications were carried out in order to try to solve the problem. Eventually a series of 52 holes were drilled in the bottom of the vehicle, located radially three feet from the center. These were to provide a central jet to stabilize the ground cushion.
With these modifications complete and apparently working, the first completely free flight occurred on 12 November 1959. This test proved the nozzle control system unacceptable. The spoilers were intended to direct the air out over the top or bottom of the annular flap, out the bottom only during hover, but over the top and bottom during forward flight. The idea was that when the flap was positioned in order to provide control, the lift would be lowered on one side and raised on the other. Lift was indeed lowered on one side, but the lift did not improve on the other, so every control input resulted in a loss of altitude. After five flights, testing was temporarily halted on 5 December 1959, by which time the Avrocar had logged 18.5 hours of test time in total.
![Avrocar flying](https://upload.wikimedia.org/wikipedia/commons/2/2b/Avrocar_flying.jpg)
A completely new design was installed over the winter. The original spoilers were removed and replaced by a single ring below the annular flap. The ring shifted in relation to the craft under control input, "sealing off" the gap on one side while opening it on the other. Tests continued in January 1960, and appeared to work much better. However, while the new control system improved the hovering qualities, the craft now became unstable at higher speeds above . The first Avrocar at Ames was similarly modified, and, in April 1960, it was tested in their wind tunnel. The problem became clear; the ring blocked so much of the overall engine thrust that the overall power was greatly reduced. As the craft sped up, the airflow on the underside reduced the recirculation, reducing the lift due to airflow over the upper surface. This was somewhat unexpected; recirculation had been considered a "bad thing" due to the loss of engine thrust, and its positive effects on lift do not appear to have been appreciated. In the end, in order to maintain lift at higher forward speeds the craft had to be pitched to the end of its control capability.
Avro was convinced that the concept was still workable, and proposed a new program for major rework of the propulsion and control system. Instead of the single annular triangular flap and spoilers, or the later ring control, the new system included two separate control systems for hover and forward flight, combined into a single nozzle. For hover, a series of "transition doors" were opened into the nozzles, blocking them off and re-directing the flow downward under the aircraft. Control during this regime was provided by moving the outer portion of the flap to "focus" the flow. At higher speeds, the doors were closed, allowing the air to flow out from the edge of the aircraft, where a series of simple flap-like controls were located. The new control system covered the rear 3/4's of the aircraft's outer circumference; the front section featured the hovering controls only.
![Avrocar in operation](https://upload.wikimedia.org/wikipedia/commons/2/2e/Avrocar_in_operation.gif)
Modifications were completed on the Ames model and testing resumed in April 1961. The new design demonstrated much better control in hover and considerably improved lift. The vehicle was now able to travel at up to , a great improvement over the previously reached. However, it remained unstable in pitch, and exhibited a strong nose-up trim. NASA engineers attempted to modify this with a
T-tail
A T-tail is an empennage configuration in which the tailplane is mounted to the top of the fin. The arrangement looks like the capital letter T, hence the name. The T-tail differs from the standard configuration in which the tailplane is ...
, but this proved to sit within the airflow of the turborotor and did not help. Frost's team considered two new designs, one with a large vertical tail and one with a wing with tip mounted verticals —"winglets." Both designs used two thrust
General Electric J85
The General Electric J85 is a small single-shaft turbojet engine. Military versions produce up to of thrust dry; afterburning variants can reach up to . The engine, depending upon additional equipment and specific model, weighs from . It is one ...
turbojets and increased the turborotor diameter from five to six ft.
On 9 June 1961, a second USAF/NASA flight evaluation of the Avrocar was conducted on the similarly modified second prototype at the Avro facility. During these tests, the vehicle reached a maximum speed of and showed the ability to traverse a ditch six feet across and deep. Flight above the critical altitude proved dangerous if not nearly impossible due to inherent instability.
[Winchester 2005, p. 68.] The flight test report further identified a range of control problems.
Cancellation
Before modifications could be achieved, funding ran out in March 1961. Frost's proposals for a modified design were not accepted, and the Avrocar and related WS-606A supersonic VTOL programs were officially cancelled in December 1961 by the U.S. military. Avro company executives encouraged additional VTOL research projects, exploring new configurations married to a disk platform
and even a "lift jet" version, but no further interest resulted from Canadian or other sources, to cap the end of this Special Projects Group program. In 1961, a number of later proposals, including the Avro P470 VTOL fighter concept derived from the Special Projects Group, were submitted to fulfill a NATO competition for a tactical strike fighter. These needs were filled by the
Hawker Siddeley Harrier
The Hawker Siddeley Harrier is a British military aircraft. It was the first of the Harrier series of aircraft and was developed in the 1960s as the first operational ground attack and reconnaissance aircraft with vertical/short takeoff and ...
, but in more general terms, interest in VTOL faded as it became widely believed a nuclear first strike would not be used at the start of a European war.
![NASM Avro VZ9V-1](https://upload.wikimedia.org/wikipedia/commons/4/4b/NASM_Avro_VZ9V-1._%281984%29.jpg)
The second Avrocar had logged about 75 flight hours at the end of the flight testing. Judged by its performance, the Avrocar was an abject failure: it could not lift itself safely more than a few feet off the ground, and its bulbous design limiting high-speed performance accompanied by unbearable heat and screaming exhaust noise, made it impractical for the military. Although considered a technical failure, its design would be prophetic: it was a rubber skirt shy of being one of the world's first
hovercraft
A hovercraft, also known as an air-cushion vehicle or ACV, is an amphibious Craft (vehicle), craft capable of travelling over land, water, mud, ice, and other surfaces.
Hovercraft use blowers to produce a large volume of air below the hull ...
, the
Saunders Roe SR.N1
The Saunders-Roe SR.N1 (Saunders-Roe Nautical 1) was the first practical hovercraft. The concept has its origins in the work of British engineer and inventor Christopher Cockerell, who succeeded in convincing figures within the services and in ...
also taking off in 1959. Nevertheless, company designer John Frost applied for a number of patents in Canada, the UK and the U.S. that established the pivotal role that the Avrocar and related Avro experimental vehicles made in the VTOL world.
Latest developments
![U](https://upload.wikimedia.org/wikipedia/commons/b/b2/U.S._Air_Force_Museum_C_%2834%29.jpg)
The Avro VZ-9 Avrocar was a "dead end" in VTOL design, according to Russell Lee, curator at the
National Air and Space Museum
The National Air and Space Museum of the Smithsonian Institution, also called the Air and Space Museum, is a museum in Washington, D.C., in the United States.
Established in 1946 as the National Air Museum, it opened its main building on the Nat ...
, yet its technological innovations have intrigued other designers. One of the design elements it embodied, the use of ducted fans, led to other experimental programs. Dr. Paul Moller, a Canadian expatriate who had worked at Avro Canada as a young engineer, based an initial series of experimental VTOL vehicles on "saucer" technology utilizing the buried ducted fan à la-Avrocar. The XM-2, the first of the series looked remarkably like a miniature flying saucer. After successful tether tests,
[Relly Victoria Petrescu and Florian Ion Petrescu. ''The Aviation History (New Aircraft I)'']
The Aviation History (New Aircraft I)
Retrieved: 25 March 2018. Note: The reference to successful tethered test appears on pg 19. the saucer designs also at one time publicized as "discojet" were abandoned and their latest project, the
Moller Skycar
The Moller Skycar is a flying car with VTOL (vertical take-off and landing) capability which has been under development by Paul Moller for over forty years. As of 2022, the M400 has not achieved free flight.
Due to the project's failure to del ...
, has a flying-car appearance.
[Zuk 2001, pp. 92, 93.]
The Avrocar story did not end with the termination of the program. Only two Avrocars were ever produced and because the U.S. military had paid for the work, they reverted to U.S. ownership at the end of the program. The second example, S/N ''59-4975'', utilized for "flight" testing, returned to Canada briefly for display in Montreal at the ''Man and His World Exhibition'' (1968); after a lengthy period of outdoor display, it is now under restoration at the
U.S. Army Transportation Museum
The U.S. Army Transportation Museum is a United States Army museum of vehicles and other transportation-related equipment and memorabilia. It is located on the grounds of Fort Eustis, Virginia, in Newport News, on the Virginia Peninsula.
History ...
in Fort Eustis, Virginia.
![AVRO CANADA VZ-9AV AVROCAR at Wright Patterson AFB](https://upload.wikimedia.org/wikipedia/commons/6/63/AVRO_CANADA_VZ-9AV_AVROCAR_at_Wright_Patterson_AFB.jpg)
The first Avrocar, S/N ''58-7055'' (marked ''AV-7055''), after tethered testing, became the "wind tunnel" test model at NASA Ames, where it remained in storage from 1961 until 1966, when it was donated to the
National Air and Space Museum
The National Air and Space Museum of the Smithsonian Institution, also called the Air and Space Museum, is a museum in Washington, D.C., in the United States.
Established in 1946 as the National Air Museum, it opened its main building on the Nat ...
, in
Suitland, Maryland
Suitland is an unincorporated community and census designated place (CDP) in Prince George's County, Maryland, United States, approximately one mile (1.6 km) southeast of Washington, D.C. As of the 2020 census, its population was 25,839. Prio ...
. There it continued gathering dust for the next forty years. The Museum finally scheduled it for restoration and display at their newly constructed
Steven F. Udvar-Hazy Center
The Steven F. Udvar-Hazy Center, also called the Udvar-Hazy Center, is the Smithsonian National Air and Space Museum (NASM)'s annex at Washington Dulles International Airport in the Chantilly area of Fairfax County, Virginia. It holds numerous e ...
. Instead the Avrocar has been loaned to the
National Museum of the United States Air Force
The National Museum of the United States Air Force (formerly the United States Air Force Museum) is the official museum of the United States Air Force located at Wright-Patterson Air Force Base, northeast of Dayton, Ohio. The NMUSAF is the ...
in
Dayton, Ohio
Dayton () is the sixth-largest city in the U.S. state of Ohio and the county seat of Montgomery County. A small part of the city extends into Greene County. The 2020 U.S. census estimate put the city population at 137,644, while Greater Day ...
, arriving in November 2007. After a full restoration, which included fabrication of both missing plexiglass bubbles, it was put on display in June 2008 in the Museum's Cold War Gallery. It has since been moved to the Presidential Aircraft Gallery. In 2016, the Avrocar was moved to the museum's Research and Development Gallery in its new fourth hangar.
A full-scale replica of the Avrocar was prepared for the 2002 production, ''Avrocar: Saucer Secrets from the Past.'' It now resides as an exhibit at the
Western Canada Aviation Museum
The Royal Aviation Museum of Western Canada (formerly the Western Canada Aviation Museum) is a museum in Winnipeg, Manitoba, Canada. The museum opened to the public in its new location on 21 May 2022.
History
The Western Canada Aviation Museum w ...
,
Winnipeg
Winnipeg () is the capital and largest city of the province of Manitoba in Canada. It is centred on the confluence of the Red and Assiniboine rivers, near the longitudinal centre of North America. , Winnipeg had a city population of 749,6 ...
,
Manitoba
Manitoba ( ) is a Provinces and territories of Canada, province of Canada at the Centre of Canada, longitudinal centre of the country. It is Canada's Population of Canada by province and territory, fifth-most populous province, with a population o ...
, Canada.
Specifications (VZ-9-AV)
See also
*
Nemeth Parasol
Nemeth Parasol was a prototype of a taildragger tractor configuration airplane with circular wing set in a parasol configuration. It was designed by Steven Nemeth from Dayton, Ohio and made its first flight in 1934. The goal was to have a plane th ...
Notes
References
Bibliography
*
* Campagna, Palmiro. ''The UFO Files: The Canadian Connection Exposed''. Toronto: Stoddart Publishing, 1998. .
*
*
Milberry, Larry. ''Aviation in Canada''. Toronto: McGraw-Hill Ryerson Limited, 1979. .
* Milberry, Larry. ''The Avro CF-100''. Toronto: CANAV Books, 1981. .
* Rogers, Mike. ''VTOL: Military Research Aircraft''. New York: Orion Books, 1989. .
* Rose, Bill and Tony Buttler. ''Flying Saucer Aircraft (Secret Projects)''. Leicester, UK: Midland Publishing, 2006. .
* Taylor, Michael. ''The World's Strangest Aircraft''. London: Grange Books plc, 1999. .
* Winchester, Jim. ''The World's Worst Aircraft: From Pioneering Failures to Multimillion Dollar Disasters''. London: Amber Books Ltd., 2005. .
* Whitcomb, Randall. ''Avro Aircraft and Cold War Aviation''. St. Catharine's, Ontario: Vanwell, 2002. .
* Yenne, William. "From Focke-Wulf to Avrocar." ''Secret Weapons of World War II: The Techno-Military Breakthroughs That Changed History''. New York: Berkley Books, 2003. .
* Zuk, Bill. ''Avrocar, Canada's Flying Saucer: The Story Of Avro Canada's Secret Projects''. Erin, Ontario: Boston Mills Press, 2001. .
* Zuk, Bill. ''The Avrocar Story.'' Winnipeg: MidCanada Entertainment, 2002
Avrocar Story
* Zuuring, Peter. ''The Arrow Scrapbook''. Kingston, Ontario: Arrow Alliance Press, 1999. .
External links
Avrocar Continuation Test Program Footage (1961)Aero Sys Div, 1969 (RG 342 UD-UP 138; NND 63253; Boxes 35 and 58)National Museum of the USAF fact sheet for the Avrocarofficial Project Silverbug report at CufonProject 1794 Final Development Summary Report, 06/1956 ARC Identifier 6920770 / MLR Number UD-UP 138"Wankel Rotary Powered Flying Car", TV episode covering the Moller Aircraft has several clips demonstrating the "hubcapping" problem.
{{Good article
1950s Canadian experimental aircraft
1950s United States experimental aircraft
Aircraft first flown in 1959
Aviation history of Canada
VZ-9
Cancelled military aircraft projects of the United States
Ducted fan-powered aircraft
Flying saucers
Henri Coandă
Lift fan
Trijets