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NEWS | Dec. 1, 2006

Dirt runway testing increases C-17 safety, agility

By Tech. Sgt. Eric Grill 95th Air Base Wing Public Affairs

In an effort to expand the capability of the C-17 Globemaster III, about 40 people from the C-17 Integrated Test Force are in the midst of a four-phase test program to determine the C-17 takeoff and landing performance on non-paved surfaces.

Engineers and pilots are testing the aircraft in extreme runway conditions to eventually write the book for landing on dirt runways during dry, wet and muddy runway conditions.
"The landing on different types of surfaces significantly plays a role because of the friction factor," said Capt. Erin Meinders, 15th Airlift Squadron pilot. "The more friction the surfaces cause during landing and take off plays a role in determining the weight the aircraft can carry. These tests will prove to be extremely valuable for they will give us more of an understanding on the capabilities of the aircraft and allow us to better aid the warfighters on the ground."

Phase 2 is scheduled to get under way Monday. It follows lessons learned from flight tests conducted during Phase 1, which occurred between Sept. 16 and Nov. 8 at Fort Hunter Liggett, Calif.

According to Lt. Col. Bob Poremski, C-17 Integrated Test Force director, the first phase put the C-17 through tests to validate the ability to bring a large force into an airfield without making runway condition corrections.

Testing at Fort Hunter Liggett started with a dry landing zone "without re-grooming or re-preparing the runway to see if it's able to sustain rapid deployment operations with enough aircraft," Colonel Poremski said. "Once that was done, we progressively wet the ground in a controlled manner to correlate how much rainfall would happen if something like a thunderstorm rolls by and drops a quarter-inch of rain to see the effect it has on the braking action of the aircraft."

The purpose of the testing is to open up the capability to bring warfighters and equipment closer to the combat zone so there is not as much transit time.

"The C-17 was designed to deliver forces and cargo from an initial pickup point and directly to the battlefield. This is called the direct-delivery concept," Colonel Poremski said. "The original testing only cleared a small portion of the types of surface the earth is made out of. Our testing is expanding the types of surfaces the C-17 can operate in and out safely."

Performing tests on wet, semi-prepared runways proved to be a challenge, said Gus Christou, a mechanical subsystems engineer with the 418th Flight Test Squadron.
"The biggest concern we had was executing this test on a relatively short runway," Mr. Christou said. "Most of the runways are 5,800-feet long and for the wet-testing, we proposed in the test plan by splitting the runway into a partial wet section and a partial dry section to ensure the aircraft could perform stopping as well as takeoff (again)."

There also was a computer modeling issue, Mr. Christou said. The performance software that currently is available for the aircraft addresses both take offs and landings on wet and dry conditions for ordinary concrete runways. However, in this particular case there is a mixed condition runway.

"The software cannot predict performance of the airplane on a combination of dry and wet runways," he said. "That existing software had to be blended to accommodate a dry and wet runway. It was very time-consuming."

In the end of the testing at Fort Hunter Liggett, the upgraded software models were able to accurately predict the aircraft performance.

"But it's quite a spectacular site to see this huge cloud of dust chasing you when you're taking off, and then the same thing happening when you're landing -- a dust cloud chasing you as you come to a stop," Mr. Christou said.

The third and fourth phases are scheduled to take place at Fort Chaffee, Ark., and Fort McCoy, Wis., next year. Officials say all four phases of testing are scheduled to be completed by November 2007. (AFPN)