PAUL LEWIS / ORLANDO
McDonnell Douglas YC-15 could be revived as demonstrator
Boeing is studying the modification of the McDonnell Douglas YC-15 prototype into a tilt-wing technology demonstrator within the next two years in support of the company's Phantom Works Advanced Theater Transport (ATT) concept for a super short take-off and landing (SSTOL) aircraft.
The YC-15 would be an around 80%-scale ATT demonstrator, and the principal modification would be the installation of a forward-cranked wing that could rotate the trailing-edge down by up to 20°. The original Pratt & Whitney JT8D-15 turbofans would be replaced by four off-the-shelf 2,235kW(3,000shp) class turboprops with cyclic-controlled propellers.
"We would leave the tail on to start with until we demonstrate the cyclical control for yaw and pitch. Downstream we would take off the tail. Flying the vehicle would be no different. The advanced control programme we've had going with NASA Dryden routes stick and rudder pedal commands through a computer controller. We're taking it to a new extreme and rolling in the propulsion system," says George Muellner, Boeing senior vice-president air force systems.
The demonstration is intended to prove the viability and utility of a tilt-wing SSTOL transport capable of operating within a 200-300m (650-1,000ft) field length.
The other main technology goal would be to validate cyclic controls for the first time on a fixed-wing aircraft. Active flow control over the wing for low-speed control could also be tested, as could an "opportunistic landing system" for identifying suitable landing strips.
The YC-15 was conceived as aSTOL replacement for the Lockheed Martin C-130 before cancellation in 1979. It is considerably smaller than the planned ATT, which would have a fuselage cross-section similar to the Boeing C-17. The ATT would be capable of carrying 36,320kg (80,000lb) over 5,550km (3,000nm) and require 8,950kW-class turboprops, not yet available.
Boeing owns the stored YC-15, but is seeking Department of Defense and Defense Advanced Research Projects Agency cash to support the demonstration. While the US Army puts increased importance on the need for an advanced mobility transport, the mission is the responsibility of the US Air Force, where it is less of a priority.
Source: Flight International
