Canal wing
The channel wing ( channel wing , tubular wing) is a wing configuration developed by Willard Ray Custer in the 1920s. The most important part of the wing consists of an upwardly open tube half in which the engine is suspended in the middle. The thrust propeller (pressure screw) is located at the rear of the channel and thus the wing.
development
In 1925, Willard Custer, interested in flying, observed how a complete barn roof was raised by a storm and carried through the air. Since the wind had not been able to reach under the construction, Custer concluded that the high wind speed over the ridge had caused a strong upward suction. His preoccupation with this phenomenon finally led from 1928 to the first models of a new type of wing construction in the form of semi-tubular canal wings instead of the usual wings. Custer patented this design in 1929. He further developed the semi-tubular channel wings and so the CCW-1 ( Custer Channel Wing 1 ) could launch for the first time on November 12, 1942 . Custer built other aircraft, most recently the CCW-5, which was produced in small series from 1964.
Working principle
Custer was the first to summarize that the lift of an aircraft wing is not due to the speed at which the wing is moved through the air, but the speed of the air that sweeps over the wing: “It's the speed of air, not the airspeed ! ”(“ It's the speed of the air, not the speed in the air ”).
To put it simply, a wing works because the air above the wing has a lower pressure than the air below the wing. As a result, the aircraft is “sucked” upwards, so to speak. With conventional wings, the pressure difference arises from the curvature of the wing and the angle of attack (inclination of the wing towards the airflow). This results in a downward deflection of the air, which generates lift according to the principle of conservation of momentum.
Conventional aircraft first have to reach a certain speed before the air flows sufficiently quickly and the wings can generate sufficient lift for a flight.
The air accelerated by the rotating propeller is directed backwards in a stable jet over the wings of the Custers Channel Wing. According to the potential theory, a propeller tries to suck in air evenly from all sides on the suction side . Since this is not possible with a channel wing due to the wing underneath, a strong negative pressure and thus lift is generated in the channel above the wing. The speed of the aircraft is of secondary importance here. The aircraft is thus STOL ( short takeoff and landing ) capable .
Outlook: applications and limits
So far, the concept has not had a major breakthrough, although Channelwing aircraft should theoretically be capable of vertical flight. Custer was able to demonstrate the enormous lift experimentally. Since the rudders did not respond when the vehicle was stationary, all aircraft built needed a short run-up distance before the rudders worked (example: 61 meters for the CCW-1, 20 meters for the CCW-2). None of the aircraft was designed for pure vertical flight, the lowest take-off speed was 20 miles / hour (32 km / h). A use as a bush flyer would be conceivable. A vertical flight would also be possible with a few changes.
Custer examined the flight characteristics of both pure channel wings and channel wings with additional, external, short surfaces, as shown in the graphic above. The construction worked well at low speeds. At higher speeds, however, at high speeds of the propeller the wings vibrated, which was also transmitted to the airframe and led to a high level of noise pollution. Under long-term stress there was also the risk of structural fatigue fractures.
Another serious disadvantage of the channel swing is that the lift depends directly on the propeller power. That means u. a. that the lift on the landing approach (with reduced engine power) decreases very strongly. Therefore, with this concept, good short take-off properties are combined with poor short-landing properties.
There are currently two CCW aircraft left. The CCW-1 is located in the Smithsonian National Air and Space Museum in Suitland, Maryland . The CCW-5 is on display at the Mid-Atlantic Air Museum in Pennsylvania .
Aircraft previously built according to the channel wing principle
| Models | developer | Companies | approximate year of construction |
|---|---|---|---|
| CCW-1 | Willard Ray Custer | Custer Channel Wing Corporation | 1942 |
| CCW-2 | 1948 | ||
| CCW-3 | 1949-1952 | ||
| CCW-4 | |||
| CCW-5 | 1953-1964 | ||
| RF-1 not secured | Hanno Fischer | Rhein-Flugzeugbau, Mönchengladbach | 1960 |
| P-20 Raider | Product Development Group | 1985 | |
| P-50 Devastator | 1986 | ||
| V-22 Osprey variant | not completed | 1988 | |
| Antonov An-181 | Pyotr V. Balabuyev | Design office Antonov | around 1990 |
literature
- Donald Liska - Channelwing aircraft , The Wisconsin engineer Vol. 57, No. 6, pp. October 16-19, 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 June 24-26, 2002, AIAA 2002-3275, St. Luis, Missouri, 2002
- Walt Boyne - The Custer Channel Wing Story , Airpower Magazine, Volume 7 No. May 3, 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