C-17 drag reduction testing in progress

Testing on improvements to reduce drag on the US Air Force’s C-17 Globemaster III aircraft is now in its final stages with the 418th Flight Test Squadron.

Under the C-17 Drag Reduction programme the air force is looking at ways to reduce the C-17’s fuel consumption by reducing the aircraft’s drag in flight. 

Problem areas of excessive drag were identified during computational fluid dynamics simulations and wind tunnel tests. Parts are being tested in various configurations to see if the external structure modifications can improve airflow around the airplane. 

The first two phases tested parts made by Vortex Control Technologies. The final three of five phases are testing 3-D printed parts produced by Lockheed Martin.

Under the third phase 12 microvanes were placed toward the aft of the C-17, and the fourth phase saw three fairings added to each wing. The fifth phase will keep the 12 microvanes and six total fairings with the addition of two fairings on each winglet.

At least three flight tests are conducted with each phase – a flying qualities regression flight and cruise performance flights at .74 and .77 Mach. Testing will also be carried out to ensure there is no impact on the aircraft’s airdrop capabilities.

Flight data is collected and analysed to see how much drag is reduced. Pending the completion of testing the air force will take a decision on whether or not any of the modifications should be implemented throughout the C-17 fleet.

Bogdan Wozniak, the 418th FLTS, project engineer, said: ‘A one percent improvement in drag reduction will result in 7.1 million gallons of fuel reduction per year. One to two percent drag reduction could translate to $24-48 million dollars in fuel savings per year.’