Giving a new lift to old wings

Press, 10 March 1987, Page 13

Giving a new lift to old wings

By

BRIAN WALTERS,

aviation correspondent

Heavily laden aircraft need long runways so that they can pick up enough speed to give them the lift for take off. Designing a passenger aircraft that would take off on a short runway, or even vertically, but without being prohibitively costly, has challenged engineers for years. An unusual wing design, pioneered in America more than 35 years ago, forms the basis for a new British aircraft that has excited considerable interest in the Pentagon and could have potential in the civil market. The brainchild of Tim Luscombe of United Aerospace Technologies, the P2O Raider makes use of a channel wing to take off and land in short distances. As long ago as 1951, Willard R. Custer developed a small transport aircraft whose two piston engines were suspended over deeply curved channels. Their function was to speed up airflow through the channels, producing substantially greater lift over that part of the wing. This enabled the five-seat aircraft to clear a 15-metre hurdle after a run of only 76 metres. Custer’s aircraft could cruise at 288km/h but stalled at only 32km/h — an incredibly slow speed even by today’s standards.

But the plane never entered production and little has been heard of it since the 19605. Recent work has concentrated on development of aircraft like the V-22 Osprey. This is a tilt rotor aircraft which combines the vertical take-off of a helicopter with the the forward flight of a conventional aeroplane. It is to be used by all four of the United States forces and is to enter service in the early 19905. However, the complexity of the large tilting rotors makes the Osprey an expensive aircraft to buy. This has led United States Navy experts to consider cheaper alternatives — and some regard Luscombe’s P2O Raider to be a strong candidate. Attracted by the exceptional performance of Custer’s design, Luscombe has adapted it in a number of ways to simplify production, and to further improve take-off performance he has added a “vortex” flap system behind the engines. This looks like a Venetian 'blind, smoothing the downward curve of the airflow to produce an “air flap.”

Called the Coanda effect, this will ensure that the Raider will be able to take off from the shortest runways. So although the Raider will not hover or take off and land vertically, it will be capable of carrying a useful load in its boxlike fuselage (30 combat troops or cargo) more cost effectively than the Osprey. That, at least, is the theory. But it will need a considerable investment to build and prove the design. Luscombe’s company specialises in combining composite materials technology with advanced aerodynamics, but he will need to find a partner in order to exploit the unusual characteristics of the P2O Raider. Discussions with Sam Stoner, president of the Custer Channel Wing Corporation, have already taken place, but a projct of such magnitude will need the involvement of at least one major company which could provide the necessary technical facilities as well as finance.? Copyright — London Observer Service