Four-Phase Program Hopes To Add To Freighters Capability

The USAF's C-17 Integrated Test Force at Edwards Air Force Base, CA is in the midst of a four-phase test program to chart the aircraft's 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.

Phase 2 is scheduled to get under way December 4. It follows lessons learned from flight tests conducted during Phase 1, which occurred between September 16 and November 8 at Fort Hunter Liggett, CA.

According to Lieutenant Colonel Bob Poremski, C-17 Integrated Test Force director, the first phase validated the jet's ability to bring a large force into an airfield without making runway condition corrections.

Testing at Fort Hunter Liggett started with charting performance on an unprepared, dry landing zone according to Poremski. Once completed, the team added water to the surface approximating differing amounts of rainfall.

Successful testing should allow deployment of the aircraft closer to the combat zone cutting transit times.

"The C-17 was designed to deliver forces and cargo from an initial pick-up point directly to the battlefield. This is called the direct-delivery concept," said Poremski, but original testing of the aircraft didn't include unimproved surfaces. "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 Edwards' 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, with the exception of the Edwards runway, are 5,800-feet long. For the wet-testing we proposed in the test plan, we really didn't have enough room to execute on a fully-wetted runway. So, we split 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."

Testing at Fort Hunter Liggett eventually validated the upgraded software models; by the end of testing it was able to accurately predict 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 dust clouds and wet dirt that arose from takeoffs and landings added some unusual aspects to the testing process.

"Through semi-prepared runway operations testing and weighing the aircraft after the take-offs and landings, we've seen anywhere from 1,200 to 1,500 additional pounds of dirt collected in the aircraft," noted Poremski. "We've seen enough dirt collect in the wheel wells to where it was eight to 10 inches in depth.

Maintenance is also an issue. Crews used fire hoses to get the mud off the aircraft. Instrumentation temporarily mounted to the landing became "semi-permanent" because of the dried mud.

The third and fourth phases are scheduled to take place at Fort Chaffee, AR, and Fort McCoy, WI next year. Officials say all four phases of testing should be complete by November 2007.

ANN Salutes Technical Sergeant Eric M. Grill of 95th Air Base Wing Public Affairs.

FMI: www.af.mil