Thursday, July 3, 2014
Wind-Tunnel Test To Assess Benefits Of Lockheed’s HWB Airlifter
NASA and the U.S. Air Force Research Laboratory (AFRL) are planning transonic wind-tunnel tests of Lockheed Martin’s Hybrid Wing Body (HWB) fuel-effi cient strategic airlifter concept.
The HWB combines a blended wing and forebody (for aerodynamic and structural effi ciency) with a conventional aft fuselage and tail (for compatibility with current airlift missions, including airdrop).
Under a study for AFRL, Lockheed calculated the twin-engined HWB would burn 70% less fuel than a Boeing C-17 through a combination of better aerodynamics, newer engines and lighter structures. Wind-tunnel tests planned to begin in December at the National Transonic Facility at NASA Langley Research Center in Virginia will focus on validating a key aspect of the
HWB design—mounting the engines above the wing.
Lockheed conducted extensive computational fl uid dynamics (CFD) analysis that showed mounting the
nacelles over the inboard trailing edge of the wing reduced interference cruise drag and improved liftto-
drag ratio by up to 5%.
A 4%-scale, half-span model of the HWB, powered by Rolls-Royce’s conceptual UltraFan ultra-high-bypass
geared turbofan, will be tunnel-tested with the nacelle mounted conventionally under
the leading edge and over the trailing edge to validate the
benefit.
NASA and AFRL also are funding Lockheed to use the ompany’s CFD analysis tools to look at the aerodynamic
optimization of distributed propulsion on the HWB, using multiple smaller fans that would be integrated with the
blended wing.
Previous studies have focused on the design of the propulsion system itself, and particularly on the efficiency
challenges of mechanical or electrical power distribution, rather than its impact on aircraft aerodynamics.
Lockheed, meanwhile, has expanded its companyfunded HWB studies to encompass a multi-role aircraft it says would provide strategic tanker and transport capability with commercial-airliner levels of efficiency.
AFRL also is turning its attention to the next generation of U.S. Air Force aerial refueling tanker to follow the
planned procurement by 2027 of 179 Boeing 767-based KC-46s, which will replace only a portion of today’s KC-135
and KC-10 fleets.
The laboratory is evaluating whether a next-generation tanker will need to be able to operate in contested airspace,
and is taking another look at the stealthy airlifter concepts developed by Boeing, Lockheed Martin and Northrop Grumman
under the AFRL-led Speed Agile program.
Speed Agile, which ended in 2012 with a large-scale wind-tunnel test of Lockheed’s design, demonstrated powered-lift concepts for a future stealthy, super-shorttakeoff-and-landing tactical airlifter to replace the C-130.
—Graham Warwick,
[email protected]