The Arnold Engineering Development Center at Arnold Air Force Base, Tenn., recently completed a Continuous Improvement Program Life Extension Accelerated Mission Test on an F119 engine for the F-22 Raptor in the Sea Level 2 facility.
“The purpose of this particular test, a life extension Accelerated Mission Test, was to add another 2,165 TACs to it, which is equivalent to approximately another five years of life in the field,” said Rich Walker, AEDC F119 engine test project manager.
This established a new record of ground testing on the engine, a record which had been previously set at AEDC in May 2010.
However, Walker said more importantly, it’s what the test has accomplished for the war fighter.
“We’re taking an engine that’s already gone as far as it’s supposed to go by specifications and now we’re going to fly it the equivalent of five more years to see what happens, where the wear accumulates on parts, where things stop working the way they’re supposed to work,” he said. “The full life of an F119 is 8,660 TACs, which is equivalent to approximately 20 years of regular service in the field.
“This engine had already accumulated that many TACs and that equivalent time on it when it arrived here in June of 2011.”
Walker said the benefits of an AMT approach to ground testing the F-22 Raptor’s power plant are indisputable.
“We’re trying to expand the tech order limits,” he said. “In other words, if there’s a tech order in the field that says you have to replace this part after so much time, because that’s a calculation, but if we can prove that no, you don’t need to replace it at this interval, you can wait until a longer interval. That saves the taxpayer a lot of money, because you’re not replacing parts before they need to be replaced.”
2nd Lt. Carl Tegtmeier, AEDC’s other Air Force project manager on the test, said, “This engine is still tested within its operational vibration limits, but it’s purposefully put out of balance so you see what the worst type of allowable vibrations will do to the wear of the engine.”
Walker said the most important reason for “testing before flight” can’t be measured in dollars.
“It’s a whole lot better to find out issues here on the ground than when it’s on an F-22 and there’s a pilot involved,” he said. “You don’t want to put the pilot in harm’s way.”
During an AMT test program, the engine undergoes a sequence of mission profiles designed to generate a specific number of Total Accumulated Cycles to simulate the operational wear it would experience in the field. An AMT mission profile is a sequence of throttle, horsepower and nozzle vector movements and specific amounts of operating time at idle, cruise, intermediate and maximum power settings.
The F119 AMT program includes AMT mission profiles which are conducted at three types of test conditions: ambient, heated and RAM. To minimize cost, the majority of the AMT missions are conducted at ambient conditions.
The Sea Level SL-2 and SL-3 test cells were designed to provide all three types of AMT test conditions, having an operating mode for each. In atmosphere-intake mode, the air supplied to the engine is drawn directly from outside via the atmospheric intake.
In heated-intake mode, the air supplied to the engine is first drawn over a set of steam coils, via the Sea Level facilities’ corrosion-air blowers, to set the desired inlet temperature. In RAM mode, pressurized, heated air is supplied to the engine from the C-Plant air-supply compressors. This simulates conditions that the engine would experience as the pilot flies the aircraft low and fast.
Now that the test has concluded, the engine will go back to the manufacturer, Pratt & Whitney, for a complete tear down, inspection and rebuild. The engine will return to AEDC later this year as a brand-new build for another cycle of AMT work.