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Channel Wing aircraft CCW-5

The channel wing is an aircraft wing principle developed by Willard Ray Custer in the 1920s. The most important part of the wing consists of a half-tube with an engine placed in the middle, driving a propeller placed at the rear end of the channel formed by the half-tube.

Contents

Development

In 1925, Willard Custer had himself observed how very strong winds had managed to lift the roof of a barn. Custer realized it was the high velociy of the wind that created this suction, even when the barn itself was obviously not moving. He started studies into this phenomenon, and by 1928 he had made the first models of a wing with a half-tube-formed section instead of the usual wing profile. This was patented in 1929. Development of the half-tube channel wing was then refined further, and on November 12 1942 the CCW-1 (Custer Channel Wing 1) airplane was flying for the first time. Custer built additional experimental aircraft, the last one was CCW-5, of which a few were manufactured in 1964.

Functional principle

Sketch of channel wing (seen from front)

Custer's summary of his invention was that the key to the lift created by a wing is the velocity of the stream of air passing over the wing, not the velocity of the airplane itself: It's the speed of air, not the airspeed!.

A wing functions because the air over the wing has a lower pressure than the air under it. In a conventional fixed wing aircraft this happens because the stream of air over the wing has a somewhat longer passage, and thus will end up having a higher speed than the air below. The conventional aircraft must reach a significant minimum speed before this pressure differential become large enough that it generates sufficient lift to become airborne.

In Custers channel wing the rotating propeller will direct a stable stream of air backwards through the channel. A propeller will at the low pressure side normally be supplied by air from all directions. Since the half-tube prevents air from being drawn from below, the air will be sucked through the channel instead. This creates a strong low pressure area in the channel, which again generates a lift.

Applications and limitations

The concept was for a long time not successfully proven in an aircraft, even though Custer would theorethically and experimentally show the principle was capable of vertical flight. Since they were built with conventional rudders needing some minimum airspeed to be functional, none of the aircraft designed by Custer were capable off full vertical takeoff, but instead were characterized as STOL (short takeoff and landing). The required runway for takeoff was very short, however, 61 meters for the CCW-1, 20 meters for the CCW-2, with a take of speed of as low as 20 mph. Full vertical takeoff is theorethically feasible, but would require additional modifications and means of control.

Custer investigated both aircraft with pure channel wings as well as aircraft with additional conventional wings located outside of the channels. The construction functions very well at relatively low speeds. At higher speeds, at high propeller RPM, oscillations would occur in the areas around the propeller, causing increased noise as well as creating long term destructive vibrations in the structure.

Two of Custer's CCW aircraft survive. The CCW-1 is located at the Smithsonian´s National Air & Space Museum in Suitland, Maryland. The CCW-5, which was based on the Baumann Brigadier executive aircraft, is exhibited at the Mid-Atlantic Air Museum in Pennsylvania.

Later, research performed by NASA have come to the conclusion that the advantage in lift and field length performance achieved did not offset the concept's many deficiencies in climb and high speed capability, as well as problems meeting certification requirements for general aviation[1]. The main issue is that the semi-circular beam wing configuration incurs increased profile drag and weight penalties over a conventional wing of the same lifting planform, and a common straight wing could provide almost the equivalent lift enhancement when exposed to the same slipstream induced increased dynamic pressure.

Channelwing aircraft built

Model Designer Company approximate year
CCW-1 Willard Ray Custer Custer Channel Wing Corporation 1942
CCW-2 Willard Ray Custer Custer Channel Wing Corporation 1948
CCW-3 Willard Ray Custer Custer Channel Wing Corporation 1949-52
CCW-4 Willard Ray Custer Custer Channel Wing Corporation 1949-52
CCW-5 Willard Ray Custer Custer Channel Wing Corporation 1953-64
RFV-1 (uncertain) Hanno Fischer Rhein-Flugzeugbau, Mönchengladbach 1960
P-20 Raider Product Development Group 1985
P-50 Devastator Product Development Group 1986
Modified V-22 Osprey not finished Product Development Group 1988

References

  1. ^ The Channelwing Revisited, Harry Clements, SAE Document Number: 2006-01-2387
  • Donald Liska - Channelwing aircraft, The Wisconsin engineer Vol. 57, Nr. 6, pp 16 -19, October 1957, [1]
  • Kevin Brown - Cockpit-Testing the Legendary Channel-Wing, Popular Mechanics, September 1964
  • Robert Englar, Brian Campbell - Development of Pneumatic Channel Wing Powered-Lift Advanced Super-STOL Aircraft, 1st Flow Control Conference 24-26 June 2002, AIAA 2002-3275, St. Luis, Missouri, 2002
  • Walt Boyne - The Custer Channel Wing Story, Airpower Magazine, Volume 7 No.3 May, 1977
  • Unknown author - Custer's Production Model Takes Bow, Air Progress Magazine, October/November, 1964
  • Unknown author - Channel Wing Flown in Demonstration, Aviation Week, September 28, 1959

External links

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