Most of the magic in stealth aircraft design is created by geometry. By shaping an aircraft surface to reflect transmitted radio waves away from their source, the radar is effectively blinded. This works fine as long the stealthy aircraft has no need to manoeuvre. Any change in direction or altitude involves geometry-spoiling movements of control surfaces. The slightest switch can illuminate the aircraft on a radar screen.
BAE Systems apparently does not want the next generation of stealth aircraft to suffer the same limitations.
In partnership with several UK universities a decade ago, BAE sponsored the flapless air vehicle integrated industrial research project, which led to flight tests of the subscale, unmanned Demon prototype aircraft in 2010. The design validated that compressed air siphoned from a turbine engine and ejected through the trailing edge of a wing can replace a conventional high-lift system to keep an aircraft from stalling at low speeds, particularly during take-off and landing.
The Demon tests largely replicated research by the US Navy dating back to 1968. The navy wasn’t interested in stealth, but in a fighter-sized aircraft that could operate from a small-deck carrier. A modified Grumman A-6 Intruder demonstrated the concept successfully in 1979, but the US Marine Corps instead preferred continuing with production of the AV-8B Harrier. The idea of using aerodynamic flow to replace control surfaces lived on, particularly at Georgia Tech, where researchers continue to study the concept.
But now BAE is taking the research a step further by unveiling the unmanned Magma demonstrator. In addition to Demon’s flapless technology, the Magma will use a circulation control wing and fluidic thrust vectoring to replace all control surfaces. It represents the most ambitious attempt to replace mechanical control surfaces with a pneumatic-based system since the introduction of the Notar anti-torque system by MD Helicopters.
If the technology works, BAE could make a profound contribution to the field by applying it to stealthy aircraft applications. It could become a key element of BAE’s competitive offerings as the UK engages with separate European partners on future combat aircraft.
Every advance in stealth has been matched by comparable developments in counter-stealth. Combining extreme radar stealth with supersonic speed in the Lockheed Martin F-22 was the last major event. Adding stealth-preserving manoeuvrability to aircraft design may be the next major leap.
Source: Flight International
