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AFRL Works With DAFB to Make C-17s Safer, Lighter, More Fuel Efficient

Senior Airman Terrence Williamson, 736th Aircraft Maintenance Squadron aerospace maintenance journeyman, explains to Roberto Guerrero, Deputy Assistant Secretary of the Air Force for Operational Energy, Headquarters U.S. Air Force, Washington, D.C., how microvanes are positioned on each side at the rear of a C-17 Globemaster III fuselage using a Mylar® template. (U.S. Air Force photo by Roland Balik)

The Air Force Research Laboratory’s (AFRL) Advanced Power Technology Office (APTO) at Wright-Patterson Air Force Base (AFB), Ohio, collaborated with Dover AFB, Delaware, and private companies on programs to make the entire C-17 Globemaster III fleet lighter, safer and more fuel-efficient for the future.

Three programs currently being developed by the APTO to improve the Air Mobility Command’s (AMC) C-17 fleet include the installation of microvanes, the use of synthetic tie-downs instead of cargo chains, and the use of winch cables instead of steel cables. 

This visit was a follow-up to APTO’s initial visit to Dover AFB in September 2017 to showcase the three ongoing programs to Roberto Guerrero, Deputy Assistant Secretary of the Air Force for Operational Energy, Headquarters U.S. Air Force, Washington, D.C., using a C-17 set up by 736th Aircraft Maintenance Squadron (736th AMXS) personnel.

“We visited Dover late last year [2017] to do some demonstrations, and we received useful feedback from the local crew for redesigning our system. We wanted to come back to see how they liked the changes and get more feedback from them,” said Justin Smoak, Samson Rope application engineering manager, Ferndale, Washington.

Microvanes
The nylon microvanes the APTO is testing are filled with 3D printed glass beads. Each microvane is 2.4 inches tall and 16 inches long. The addition of microvanes to the C-17s is an effort contracted with Lockheed Martin to reduce drag and fuel consumption that is currently being considered for transition by Air Mobility Command.

Using a Mylar® template, 736th AMXS maintenance personnel installed 12 microvanes, six on each side at the rear of a C-17 fuselage that gave Guerrero a firsthand look. 

“Microvanes essentially clean up the airflow in the region of the cargo door by reenergizing the air with small vortices that delay separation, smooth the flow, and reduce drag,” said Capt. Randall Hodkin, AFRL APTO aviation working group lead. “Historically, cargo aircraft have airflow issues in the aft region of the airframe due to the required upsweep of the fuselage to integrate a cargo ramp.”

According to Hodkin, if all 222 U.S. Air Force C-17s had microvanes installed, fuel savings per year could range up to 2 million gallons, equating to $5 to $7 million, depending on fuel prices and mission.

“With support from Dover AFB, we were able to validate that the tooling developed as part of the AFRL program can position C-17 microvanes in the correct location to achieve the expected one-percent fuel savings,” said Hodkin.

C-17 microvane flight testing was conducted by the 412th Test Wing, Edwards AFB, California, between August and December 2016. This valuable flight test program validated that microvanes reduce drag by one percent when in cruise. In addition, the Edwards AFB flight tests also included several test scenarios to validate that microvanes do not affect the critical C-17 air drop mission capability.

Synthetic Tie-downs and Winch Cables
In addition to installing the microvanes, the team also tested synthetic tie-downs and winch cables. Tie-downs are ropes, cords, straps or chains that secure items during airlift operations. Winch cables adjust the tension on tie-downs, securing the load.

AFRL, Hodkin, Samson Rope application engineers, and an AMC subject-matter expert also returned to Dover at the end of January to demonstrate fit-for-purpose synthetic tie-down assemblies and a custom engineered winch cable. These solutions were developed after feedback from an operational evaluation at Charleston AFB in 2016 and the previous demonstration at Dover.

“For the winch cable, safety is definitely paramount,” said Senior Master Sgt. Jeff Witherly, Headquarters, AMC C-17 evaluator loadmaster, Scott AFB, Illinois. “The steel cable we currently have could possibly snap and whiplash, whereas the new synthetic cable fails in a more predictable and controlled manner.”

The proposed 280-foot synthetic winch cable weighs 14 pounds and is 83 percent lighter than the current 80-pound steel wire cable.

Loadmasters from the 3rd Airlift Squadron also helped Witherly, Hodkin, and Samson Rope application engineers with concerns about how the synthetic chain would fit in a slotted interface designed for steel chains on the buffer stop assembly (BSA), a device used during specific airdrop missions to keep pallets from shifting forward in the cargo compartment.

“We received excellent feedback on the final version of the synthetic tie-downs even though they did not interface as nicely with the BSA grooves as we’d like,” said Hodkin. “The loadmasters said that the tie-downs would work with the interface, but could be placed around the BSA frame next to the grooved interface to better restrain the BSA.”

Transitioning the existing 92 C-17 steel chains to synthetic tie-down assemblies can remove 1,000 pounds of excess weight from the aircraft, potentially reducing the annual C-17 fuel budget by $1 million and improving mission capabilities.

Way Forward
“The programs APTO is working on are great examples of how we can increase our combat capability through the smart use of operational energy,” said Guerrero. 

With fuel efficiency and costs at the forefront of the C-17 community, implementation of these three programs could help the Air Force improve capabilities and save money in the future.

The next step in replacing the steel-wire winch cable and tie-downs with a synthetic is to get them approved as official Air Mobility Command requirements. If approved, additional ground or flight testing would be the next step before fleetwide implementation.

To read the original press release, visit http://bit.ly/2nVpkct.

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