F119 engine modules arrive at OC-ALC

Published May 19, 2009
By Howdy Stout
Tinker Public Affairs

TINKER AIR FORCE BASE, Okla. -- The first modules from the production engines powering the Air Force's F-22 Raptor are beginning to arrive at the Oklahoma City Air Logistics Center for depot-level maintenance and the center's experience with these high-tech engines puts Tinker in the running for the contract to maintain the engines powering the new F-35 Joint Strike Fighter.

On the cutting edge of jet engine technology, two F119 engines power the F-22. A derivative of that engine design -- the F135 -- is the power plant for the new F-35.

"We're working on plans to get the F135 engine here," says Jimmie Green, production support flight chief for the 544th PMXS at the OC-ALC.

"We've got the experience," says Rick Robinson, F100-F119 unit chief for the 544th.

Different engine versions are proposed for the F-35 -- one for the Air Force, one for the Marines and one for the Navy. Officials at Tinker are lobbying for the maintenance contract for the Air Force version as it shares the same core module as the F119.

"They will have interchangeable parts," explains Mr. Green.

Also interchangeable will be the experience of Tinker's maintenance units. Tinker's F119 engine shop is a public-private partnership between the Air Force and engine manufacturer Pratt and Whitney. Pratt and Whitney spent $7.5 million equipping the shop while the OC-ALC staffed it with some of the best jet engine mechanics available.

The fully-equipped shop stood up in July 2004, handling maintenance on pre-production engine modules. In-service engine modules began arriving this February.

"There are six major modules to the engine and the one we're going to see is the core module," explained Mr. Green. "We're expecting about eight a month by the end of the year."

Mr. Green said the Air Force and engineers are still revising the maintenance schedule on the F119 engines. Barring unforeseen damage, engine maintenance is determined by the Time and Cycles, which is the number of times the engine is powered up. At this point, Mr. Green said, the Time and Cycles is being revised upward as engineers find the engine is requiring less maintenance than expected.

"This thing is performing far beyond what they thought it would," he said. "Even Pratt and Whitney is amazed it performs as well as it does. It's far exceeded even their expectations." As a result, Mr. Green said, the shop won't be fully staffed with its compliment of 85 jet engine mechanics until 2012 when the Raptor fleet is expected to reach in-service maturity.

The engine's reduced maintenance schedule is a direct result of its design. Engineers used Computer Aided Drafting software to design everything from the blade angles of the compressor blades to the milling of entire compressor fans from single pieces of metal. Engine components are also covered with a special coating to reduce radar returns, contributing to the stealthiness of the F-22.

Composite materials are also used in the construction of the engine, lightening the engine's overall weight. And the unique pivoting, rectangular-shaped nozzle - itself an engineering marvel - directs engine thrust for added aircraft maneuverability.

The result is a highly efficient engine capable of Mach 1.5 flight - super cruise - without the need for fuel-consuming afterburners.

"Pratt and Whitney are really proud of this engine because of the design of it," said Mr. Green. "The thing about the F119 engine is that it is a counter-rotating engine - it takes all the torque out of it," he said, explaining that reduced torque means reduced stress on engine components.

"And it has about 40 percent fewer parts."

"They totally thought outside of the box on this one," agreed Davon Hill, a first-line supervisor at the F119 shop. Although Mr. Hill has 10 years of experience with the F100 engine that powers the F-15 and F-16, his work with the F119 required a steep learning curve.

"They said take what you know and through it out, it's totally different," Mr. Hill said. "There's a whole lot of learning to do. It's totally new."

Part of the learning process is finding the limits of what the engine can and can't do and how that affects scheduled inspections and maintenance. So far, the engineers have been impressed with the durability of the F119 engine compared to the "tired iron" jet engines of the past.

"The program is so young that they're still establishing limits," Mr. Green said. "This is cutting-edge technology."

One instance of the engine's durability was a module brought for servicing after ingesting a landing gear safety pin. On inspection, the engine still spun freely with only one, small compressor blade missing.

"And that missing blade was only a little bit bigger than my thumbnail," Mr. Green said. "If the on-board computer hadn't notified the pilot, I think that engine still would have flown."