Half-century of AEDC support for F100 engine approaches

ARNOLD AIR FORCE BASE, Tenn. – When the F100 engine was tested at Arnold Engineering Development Complex (AEDC) near the end of the 1960s, it marked the beginning of what would become a longstanding relationship. Throughout the subsequent 50 years, variants of the F100, the propulsion unit used to power the F-15 Eagle and F-16 Fighting Falcon, would undergo thousands of hours of testing at Arnold across numerous facilities within the complex. Arnold has continued its support of the F100 ever since the first test. 

 “The F100 engine powers fighter aircraft vital to the defense of our nation,” said Lt. Col. Lane Haubelt, AEDC Aeropropulsion Combined Test Force director. “The proud and continuing legacy of the U.S. Air Force F-15 and F-16 aircraft is rooted in the successful development, fielding and sustainment of this workhouse engine. AEDC remains at the center of that success. The F100 engine program also highlights the importance of an enduring and integrated relationship between AEDC, engine manufacturers, engine program offices and the end user. “As we look toward the future, strong and trust-based relationships with our national security partners are essential to accomplishing our mission.”

 The history of the F100 at Arnold began in the late 1960s when the complex began supporting the F-15 program. AEDC was instrumental in the development of the F-15, as Arnold test cells and wind tunnels were used to evaluate engine and airframe performance. Data collected during these tests was used to assist in the optimization of the aircraft. Two companies – Pratt & Whitney and General Electric – were competing for an Air Force contract to build the engine for the F-15. Using engine test facilities at Arnold, the Air Force was able to evaluate the systems side-by-side in identical conditions. In 1970, the year after these efforts began, the Air Force awarded the F-15 power plant contract to Pratt & Whitney for the company’s F100-PW-100 engine.

The first operation at Arnold involving the Pratt & Whitney F100 occurred Dec. 18, 1969, in the T-4 engine test cell. From that point, AEDC logged more than 23,000 hours testing the F100 engine, which equates to more than two-and-a-half years. By 1973, AEDC testing had figured into all phases of the development cycle of the F100. Air Force Systems Command delivered the first F-15 to Tactical Air Command on Nov. 14, 1974. The F100-PW-100 engine was the initial engine installed in the F-15. The F100-PW-200 engine was the initial engine installed in the F-16, which was deployed in the late 1970s. Over time, improvements to the -200 series of the engine produced the -220. Also tested on the -220 was the variable-pitch nozzle incorporated into the F-15 Short Takeoff and Landing demonstrator fighter.

 The Aeropropulsion Systems Test Facility, also known as C-Plant, was dedicated at Arnold Air Force Base in early October 1984. The month prior, AEDC received an operational F100 engine, loaned to the Complex by the Aeronautical Systems Division out of Wright-Patterson Air Force Base, Ohio. The engine was used to verify ASTF could safely conduct testing. The first successful test run for ASTF occurred in January 1985. For this run, an engine simulator matched to the size of engines in the DC-10 and 747 commercial airliners was placed in the ASTF C-2 test cell. However, it wouldn’t be long after this that the F100 made its return to ASTF.

 In April 1985, a successful checkout test was performed in the ASTF C-1 test cell using the F100 turbofan engine. The engine ran in the test cell for more than an hour at a simulated flight condition of 16,000 feet altitude and 0.8 Mach number. The engine was operated at power levels from idle to afterburner ignition. While the test required only one of the facility’s six air supply compressor and just one of its 12 exhaust compressors, it demonstrated the successful integration of the facility equipment required to operate an engine. This marked the first test involving an actual engine in the then-new ASTF and the first in a series of F100 engine tests to validate engine operation and continue shakedown of the facility. Soon after this, the engine was tested from idle to maximum augmented power in the ASTF C-1 test cell. During this test, the F100 was operated at a simulated flight condition of 30,000 feet altitude and 0.9 Mach number. The F100 was tested at maximum augmented power to demonstrate afterburner operations. Several engine throttle transients were subsequently obtained at sea-level-static conditions, culminating in a successful engine throttle “snap” from idle to intermediate power. During this 5.3-hour test, integrated operation of the facility air supply compressors, coolers, exhaust compressors, process controls and engine support systems were successfully demonstrated. An additional engine test was conducted at maximum augmented power at sea-level-static conditions to verify engine trim. This test completed the first phase of engine tests with manual facility control. A more extensive series of tests began later in 1985 to validate ASTF operation with the Automatic Test Control System, used to control and monitor facility equipment to provide simulated flight conditions in the test cell, and the Test Instrumentation System, which records test data and calculates engine performance. The first F100 engine test using 50 of the 500 TIS data channels was successfully conducted in ASTF in July 1985. That September, an F100 test using the TIS and ATCS was also completed successfully, signaling ASTF for Initial Operating Capability. The following year, the ASTF C-2 test cell was used to test an F100 fitted with a thrust-vectoring and reversing exhaust nozzle, which was designed to deflect exhaust and reverse thrust both in flight and on the ground. This would significantly increase aircraft flight maneuverability and reduce landing distances under both normal and icy conditions.

 In the first half of 1988, Pratt & Whitney’s F100-PW-229 Increased Performance Engine, an evolved version of the standard F100 engine, completed Initial Flight Release testing at AEDC. More than 170 hours of simulated altitude testing were conducted in the Engine Test Facility over a nine-week period to clear the engine for flight testing in an F-15 aircraft that April. Some of the test periods lasted up to 22 hours, during which more than 900 engine parameters were recorded. The engine was subjected to simulated altitudes of up to 50,000 feet and speeds exceeding Mach 2. By 1992, 5,000 Total Accumulated Cycles, or TACs, which are units of measurement for major rotating engine components tracked during an engine’s operational life, were completed on the engine to substantiate the latest modification of its fourth stage turbine blades. In 1996, the F100 Super Pacer engine underwent RAM accelerated mission testing to determine how the F100 would age.

 Accelerated mission testing, or AMT, is used by engine manufacturers to rapidly age an engine. Using this method of testing, the manufacturer can accumulate several years of normal life in a very short amount of time, allowing the manufacturer to identify and work to correct issues before they would occur in normal use. RAM AMT is a variation of AMT developed by the Air Force to provide additional stress on the engine. The term “RAM” refers to the use of test facility compressors to increase the engine inlet pressure and temperature to more closely simulate actual flight conditions.The F100 has also been subjected to plenty of testing at Arnold during the new millennium. In 2001, testing in test cell T-1 validated improvements to the P&W F100-220 engine in preparation for flight testing. That August, a 12-month test program in which an F-100-PW-229 engine performed 3,503 sea level AMTs and 988 RAM AMT cycles in the center’s Sea Level Test Cells SL-2 and SL-3 concluded. Around two years later, the F100-PW-229 was brought back to SL-3 for testing to validate the durability and integrity of the engine hardware. The P&W F100-220 underwent sea-level RAM testing in the SL-2 cell in 2003. Prior to this, the engine completed testing in the J-2 Test Cell to support the Component Improvement Program. Among the testing that occurred during the 2000s involving the F100 was, at that time, the longest-running jet engine test at AEDC. This testing on the F100-PW-229 Engine Enhancement Package began in SL-3 on Oct. 19, 2009, and concluded on Sept. 21, 2010. The AMT subjected the engine to 6,000 TACs to simulate the operational stresses it would experience in flight between depot overhaul visits. The F100-PW-229 engines were typically rated at 4,300 TACs. This test, conducted with the goal of extending the operational life of the engine while reducing maintenance time and cost, involved more than 2,000 test hours. The program consumed nearly 3 million gallons of fuel. 

During 2011, altitude testing was conducted on the F100 as part of a Continuous Improvement Program project, in which new parts installed in the engine were evaluated. Another long-running test involving the F100 kicked off in early 2013. A 15-month AMT of the F100-PW-220 began in the SL-3 in January of that year and ran until the spring of 2014. This test helped extend the life of F100-PW-220 by two years – from 8 years to 10.