Fired up: F117 engine tested after overhaul

Published June 22, 2012
By Mike W. Ray
Tinker Public Affairs

TINKER AIR FORCE BASE, Okla. -- The first F117 jet engine to be tested at Tinker Air Force Base after an overhaul by the 76th Propulsion Maintenance Group was test-fired June 13.

The engine was slated to be shipped out June 20 after a 107-day repair schedule, records reflect.

Several of the engines have been repaired at Tinker, but afterward they were transported to Charleston AFB, S.C., for testing. Until just recently, Tinker did not have a test cell certified by the Federal Aviation Administration to accommodate the engines, explained Everett Guertin of the 544th Propulsion Maintenance Squadron, flight chief for the F117 Heavy Maintenance Center.

It took approximately two years of test-cell preparation to test the F117-PW-100 engines, which are a little over 15 feet long and weigh slightly over 10,000 pounds each.

Mr. Guertin said the test cell preparations included designing the test frame, maintenance stand, Pacer Comet 4 software upgrades, technical data, airflow studies, airflow improvement features and test cell correlation.

A new concrete pad was poured under the engine area "due to degradation of the original concrete," and a special floor-to-ceiling steel screen door inside the cell was designed and constructed after air flow studies revealed an air flow problem.

New heavy-duty glass panes were installed between the control room and the test cell, for observation of jet engines during test runs. In a related matter, the closed-circuit camera system was augmented with equipment that allows the operator to view the screen and engine inlet to ensure no ice buildup occurs during winter weather.

The F117 test cell, in Bldg. 3234, was renovated in a partnership between the Oklahoma City Air Logistics Center and the engine manufacturer, Pratt & Whitney.

According to Joel Williamson, accountable manager, FAA Repair Station, 76th MXW, Quality Assurance, the Department of Defense has several contractor-operated repair stations that have been certified by the FAA. Tinker's, though, is the first -- and so far only -- civil service-operated repair station in the DOD that has been certified by the FAA.

The Tinker AFB repair station includes the mechanics in Bldg. 3001 who overhaul the engines, the renovated test cell in Bldg. 3234, plus the KC-10 strip-and-paint operation in Bldg. 2280, Mr. Williamson said. "This adds to our capability," he said. "It takes us to the next level of expertise."

The F117 Heavy Maintenance Center has produced 22 engines to date. Approximately 95 Tinker employees in the 76 PMXG are assigned to the F117 HMC repair unit, Mr. Guertin said.

The F117 engine is has a rated capability of 40,000 pounds of thrust. The Air Force's advanced transport, the C-17 Globemaster III; is powered by four F117-PW-100 engines which enable the aircraft to carry a payload of 160,600 pounds. The engines are equipped with a directed-flow thrust reverser that can be deployed in flight, for use as a braking mechanism. On the ground, the thrust reverser can back a fully loaded aircraft up a 2-degree slope.