GUY NORRIS / LOS ANGELES
Successful small-scale trials claimed to have increased customer confidence in concept
The US Army plans to flight test an inflatable aircraft this year which is ultimately intended to glide autonomously to remote locations after being dropped from aircraft such as the Lockheed Martin C-130.
Development of the extended range aerial delivery system (ERADS) vehicle is being undertaken by California-based Vertigo for the US Army Soldier and Biological Chemical Command's Soldier Systems Center in Massachusetts. Vertigo, which specialises in inflatable structures and experimental flight testing, recently completed tests with a NASA Dryden-led team on a small-scale inflatable winged aircraft, the I-2000, and says positive results have "given all our customers a lot more confidence in the concept".
Unlike the I-2000, which weighed 7kg (15lb) and was configured with a conventional tail and fuselage, ERADS will use a fully inflatable tail boom, empennage and wing located high on the body. The fuselage will be a container able to carry 135-230kg payloads to a "stand-off location". The initial ERADS variant will be non-powered, but later phases include studies of possible turboprop powered versions. All variants of the precision supplies delivery vehicle will be equipped with satellite-based navigation systems.
"We are building the first prototype vehicle now, and will fly it this year," says Vertigo technologies programme manager Brook Norton. He adds that the company has "every intention" of developing it for production.
Although details of the design remain veiled, ERADS "looks like a Cessna 150", says Norton, with a span of around 7m (23ft) and a 450kg gross weight.
Key technologies include the robust, inflatable wing design, the inflation system and the spirally braided Vectran material used in spar construction.
The I-2000 tests - which used wings built for a cancelled US Navy project, the gun-launched observation vehicle - also proved that in-flight inflation is feasible. "Originally we had visions of the wings flapping in the wind before they had a chance to reach pressure, but they have shown to be very robust in that area. The inflation pressure [generally 12.4bar (180psi)], was so much higher than the dynamic pressure," adds Norton. In tests, the wing took 0.7s to inflate, and generated significant lift within another 0.05s.
Although the concept of inflatable aircraft has been explored since the 1940s, Norton says aircraft development is now feasible because of improved design and manufacturing techniques which address local stresses and loads.
Source: Flight International
