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With large-scale wind tunnel testing completed, Lockheed is fabricating a shipset of winglets for flight testing on a C-130 in 2012. The modification could be available for both retrofit and forward-fit by early 2014.
Computational analysis and small-scale tunnel tests have been completed on the C-5 winglets. Large-scale tunnel tests are planned for 2012, leading to flight tests in 2014 “if the customer is interested,” says Jack O’Banion, director of advanced development programs at Lockheed’s Marietta, Ga., plant.
The 5-ft.-tall winglets are projected to reduce cruise fuel flow by 170 lb./hr. on the C-130J and “probably more” on older versions of the Hercules, he says. They are designed to be fitted to any C-130 with the beefed-up “enhanced service life” center wingbox. This has the extra structural margin to accommodate winglet-induced bending loads.
Winglets for the C-5M are 6 ft. tall and projected to reduce cruise fuel flow by 1,100 lb./hr. This is on top of the 8-20% improvement in fuel efficiency that comes with re-engining of the C-5 with General Electric CF6-80C2 high-bypass turbofans, O’Banion says, adding that the wing already has sufficient margin to accommodate the winglet loads.
Lockheed Martin in August flight tested an aft-body drag-reduction modification on the C-130. This comprises a series of 36 vortex generators mounted on the aft fuselage. These “microvanes” alter the aft-body flowfield to pull the underbody vortex closer in and reduce base drag, he says.
Results are still being analyzed, but indications are the microvanes will reduce total drag by up to 3.7%, O’Banion says, for a fuel-consumption reduction of 2-3%. No significant changes in aircraft handling have been observed, he says.
The vortex generators, mounted in rows on the aft fuselage on either side of the rear loading ramp, are planned to be available by the end of 2012 for forward-fit and retrofit to the C-130J and earlier Hercules.
Another fuel-saving modification being studied for older C-130s is an upgrade to the latest Series 3.5 version of Rolls-Royce’s T56 turboprop, coupled with Hamilton Sundstrand’s NP2000 eight-blade propeller.
For the C-5, Lockheed also is working on a drag cleanup that is expected to improve fuel efficiency by 2-3%. This would include new seals on the flight controls to minimize aerodynamic leaks that cause drag; and new seals in the pressurization system to reduce bleed-air demand on the engines and thus improve their fuel efficiency.
In addition, equipment installed on the C-5s over time — such as defensive systems — would be cleaned up to reduce parasitic drag. “We are in the process of laying out a detailed program for the Air Force, including the business case and potential benefits,” O’Banion says.
The C-130 and C-5 drag reductions are part of an initiative by the U.S. Air Force to cut its fuel consumption. Other elements include drag cleanups on the Boeing C-17 and KC-10 and engine upgrades on the KC-135.