page_title: Avro Canada VZ-9 Avrocar
section_title: Project Y-2: the "flat-riser"
hierarchical_section_title: Avro Canada VZ-9 Avrocar / Design and development / Project Y-2: the "flat-riser"
caption_attribution_description: English: 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. The image in question, was part of a film project that I was involved in as screenwriter, original author and technical consultant. In the research phase, I obtained the rights to the extant Avro Aircraft film archives and the image was a still from an original 16 mm print that was used in the forthcoming book and documentary film. At the conclusion of the project, I retained rights to the research material. Bzuk (talk) 17:15, 22 November 2009 (UTC).
context_page_description: The Avro Canada VZ-9 Avrocar was a VTOL aircraft developed by Avro Canada as part of a secret U.S. military project carried out in the early years of the Cold War. The Avrocar intended to exploit the Coandă effect to provide lift and thrust from a single "turborotor" blowing exhaust out the rim of the disk-shaped aircraft. In the air, it would have resembled a flying saucer.
  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 eventually abandoned it. Development was then taken up by the U.S. Army for a tactical combat aircraft requirement, a sort of high-performance helicopter. In flight testing, the Avrocar proved to have unresolved thrust and stability problems that limited it to a degraded, low-performance flight envelope; 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.
context_section_description: While Project Y continued, Frost had meanwhile become interested in the Coandă effect, 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 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.
caption: "Jack" Frost 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.
exif: {}