With thinking on a future tactical airlifter shifting towards a larger aircraft able to carry heavier US Army vehicles, the US Air Force Research Laboratory is evaluating bids for its Speed Agile technology demonstration to refine concepts for a short take-off and landing intra-theatre transport.
"We are looking for one platform that can fly efficiently at 90kt [165km/h] for STOL and also transonic cruise above Mach 0.8, carrying future army payloads," says programme manager Cale Zuene. The goal is to take off and land in 460-610m (1,500-2,000ft) carrying a 30t (65,000lb) payload. "We want to get away from established airfields," he adds.
The Speed Agile concept demonstration supports AFRL efforts to fly an Advanced Joint Air Combat System (AJACS) technology demonstrator by 2015. AJACS is aimed at an eventual replacement for the Lockheed Martin C-130. "Army vehicles are getting larger and heavier, and will surpass the C-130's size," says Zuene. The goal is an aircraft that would fit between the C-130 and Boeing's C-17."
A cargo-bay width of 4m - the same as in the Airbus Military A400M - has been specified. "That's the sweet spot," says Zuene. "It can carry a lot, but does not make the aircraft so big that it competes with the C-17 on cost and size."
The requirement to operate from short and improvised runways requires a robust high-lift system, soft-field landing gear, integrated propulsion that can prohibit or tolerate foreign-object damage, and reduced observability to radar, infared and humans, says Zuene.
One of the bidders, Northrop Grumman, has proposed a flying wing with a powered-lift system using blown flaps to increase lift by 50% for STOL. The tail-less design offers stealth, lower drag for higher cruise speed and higher lift for extreme STOL, and Northrop says it has an "innovative approach" to the low-speed control challenges.
Under the 34-month Speed Agile demonstration, the winning contractor will refine its concept design, conduct low-speed and transonic windtunnel testing and use the data to develop control laws for flight simulations. "The main goal is to demonstrate speed agility - the ability to go fast and slow," says Zuene.
Source: Flight International
