Avro Canada VZ-9 Avrocar

La "soucoupe" VZ 9 d'Avro Canada vu sur Wikipedia.en

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The Avro Canada VZ-9 Avrocar was a [Vous devez être inscrit et connecté pour voir ce lien] aircraft developed by [Vous devez être inscrit et connecté pour voir ce lien] as part of a secret U.S. military project carried out in the early years of the [Vous devez être inscrit et connecté pour voir ce lien].

The Avrocar intended to exploit the [Vous devez être inscrit et connecté pour voir ce lien] to provide lift and thrust from a single "turborotor" blowing exhaust
out the rim of the disk-shaped aircraft to provide anticipated [Vous devez être inscrit et connecté pour voir ce lien]-like performance.

In the air, it would have resembled a [Vous devez être inscrit et connecté pour voir ce lien].

Two prototypes were built as "proof-of-concept" test vehicles for a more advanced USAF fighter and also for a U.S. Army tactical combat aircraft requirement.

In flight testing, the Avrocar proved to have unresolved thrust and stability problems that limited it to a degraded, low-performance [Vous devez être inscrit et connecté pour voir ce lien]; 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 [Vous devez être inscrit et connecté pour voir ce lien], who referred to it as WS-606A, Project 1794 and Project Silver Bug. When the [Vous devez être inscrit et connecté pour voir ce lien] joined the efforts it took on its final name "Avrocar", and the designation "VZ-9", part of the US Army's VTOL projects in the VZ series.

Design and development


The Avrocar was the ultimate result of a series of [Vous devez être inscrit et connecté pour voir ce lien] projects by designer [Vous devez être inscrit et connecté pour voir ce lien], who had joined Avro Canada in June 1947 after working for several British firms.

He had been with [Vous devez être inscrit et connecté pour voir ce lien] from 1942 and had worked on the [Vous devez être inscrit et connecté pour voir ce lien], [Vous devez être inscrit et connecté pour voir ce lien] jet fighter and the [Vous devez être inscrit et connecté pour voir ce lien] aircraft, where he had been the chief designer on the supersonic research project.

At Avro Canada, he had worked on the [Vous devez être inscrit et connecté pour voir ce lien] before creating a research team known as the "Special Projects Group" (more commonly known as SPG). Frost first surrounded himself with a collection of like-minded "maverick" engineers, then arranged for a work site.

Initially ensconced in the "Penthouse" (the derisive company nickname for the executive wing) of the Administration Building, the SPG was subsequently relocated to a [Vous devez être inscrit et connecté pour voir ce lien]-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 [Vous devez être inscrit et connecté pour voir ce lien]'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 [Vous devez être inscrit et connecté pour voir ce lien] lying directly outside the outer rim of the [Vous devez être inscrit et connecté pour voir ce lien], pointed outwards like the spokes on a wheel.

Power for the compressor was drawn from a new type of turbine similar to a [Vous devez être inscrit et connecté pour voir ce lien], as opposed to the more typical propeller-like turbine, driving the compressor using gearing rather than a shaft.

The resulting engine had no conventional thrust axis, and was arranged in the form of a large disk, which he referred to as a "pancake engine."

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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

At the same time, the aircraft industry as a whole was becoming increasingly interested in [Vous devez être inscrit et connecté pour voir ce lien] 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 [Vous devez être inscrit et connecté pour voir ce lien] 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 [Vous devez être inscrit et connecté pour voir ce lien].

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 vents to redirect the thrust flowing out of the "front" of the engine towards the rear,
although it was well known that long channeling leads to a loss of thrust.

In order to keep the "piping" as short as possible, the design ported the thrust out along the leading edge of what was essentially a very large [Vous devez être inscrit et connecté pour voir ce lien].

As the engine was disk-shaped, the triangular shape was "pushed out" near the front, producing a [Vous devez être inscrit et connecté pour voir ce lien] shaped roughly like a [Vous devez être inscrit et connecté pour voir ce lien].For this reason the design was also referred to as the "Avro Ace," a likely reference to the Ace of Spades.

The compressor inlet was located at the middle of the engine, so the engine air intakes 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 [Vous devez être inscrit et connecté pour voir ce lien] funded the effort with a $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 [Vous devez être inscrit et connecté pour voir ce lien] along with images of the Omega design, apparently in order to gain further funding (a strategy widely employed in the U.S. at the time, known as [Vous devez être inscrit et connecté pour voir ce lien]).

Five days later, the Minister for Defense Production informed the House of Commons that Avro was indeed working on a "mock-up model" of a flying saucer, capable of flying at 1,500 miles per hour (2,400 km/h) and climbing vertically.

Nevertheless, further funding was not forthcoming.

Project Y-2: the "flat-riser"

While Project Y continued, Frost had meanwhile become interested in the [Vous devez être inscrit et connecté pour voir ce lien], 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 [Vous devez être inscrit et connecté pour voir ce lien] shape, and eventually decided that a disk was the best solution.

Photograph of "Jack" Frost (John Carver Meadows Frost) at work in his Avro Canada laboratory (photo: 1952).

He demonstrates the Coandă effect.
Pressurized air flows out of the end of the red tube, and then over the top of the metal disk. The Coandă effect makes the air "stick" to the disk, bending down at the edges to flow vertically.

This airflow supports the disk in the air.

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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 [Vous devez être inscrit et connecté pour voir ce lien] speeds.

Subsonic lift is created by the airflow around the wing following [Vous devez être inscrit et connecté pour voir ce lien], but supersonic lift is generated by [Vous devez être inscrit et connecté pour voir ce lien] 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.