Propulsion Test Branch at Arnold AFB helping power the Air Force since 1950s

  • Published
  • By Deidre Moon

The Engine Test Facility (ETF), which is part of the AEDC Propulsion Test Branch at Arnold Air Force Base, was the first facility on base, with its construction completed in 1953.

Equipment making up the ETF test cells, such as the motors and compressors, were confiscated from a Bavarian Motor Works (BMW) plant in Munich, Germany, following World War II. This equipment was modernized and expanded considerably during its installation at Arnold. The motors and compressors were later decommissioned in 2008.

ETF test cells, which are known as the J (jet) cells and T (turbine) cells, are used for development and evaluation testing of engines most vital to the nation’s aerospace weapon systems. The first turbojet engine test was conducted in the T-1 test cell on May 3, 1954. The engine was a J-47, which was later used to power the B-47 Stratojet bomber.

The largest rocket propulsion unit tested in ETF up until September 1959, was Reaction Motor’s 50,000-pound-thrust liquid-propellant engine for the X-15 Research Aircraft. The purpose of the test was to determine the starting and throttling capabilities of the engine under high altitude conditions. Altitudes from 20,000 to 70,000 feet were simulated in the test cell, and a total of 20 starts were made during the first phase of the test program.

During the 1960s, the J1 test cell was used for testing of space systems. A full-scale Gemini abort system was checked out in J1 in 1963 and helped determine a solution for retrorocket failures during a launch abort.

Over the years, J1 has tested the F100 for the F-15 Eagle and F-16 Fighting Falcon; the F110 for the F-16 Fighting Falcon; the F118 for the B-2 Spirit and U-2; the F101 for the B-1B; and performed core testing on the Advanced Turbine Engine Gas Generator. J1 was also used to test the Rolls Royce Pegasus engine that powers the AV-8B Harrier Short Take-off/Vertical Landing aircraft as well as testing of the Tomahawk cruise missile.

In 2006, the F118-GE-100 engine for the B-2 Spirit was tested in J1 as part of the General Electric’s Service Life Extension Program, which was part of the Air Force Component Improvement Program to replace several components of the F118, F110 and F101 engines with a common core system.

In 2017, a series of tests on the Pratt & Whitney Adaptive Engine Technology Demonstrator engine core was completed in J2. The test was conducted as part of the U.S. Air Force Research Laboratory’s Adaptive Engine Technology Development program, the goal of which is to provide a 25 percent reduction in fuel consumption and a 10 percent improvement in thrust levels.

Testing of the Pratt & Whitney F135 engine recently resumed in the J2 test cell in 2019 to validate the structural integrity and aerodynamic characteristics of a new fan rotor design for the F135, the powerhouse of the F-35 Joint Strike Fighter Lightning II. Testing of the engine was later halted because of a planned outage to accommodate maintenance. Once that outage concluded, testing started again in early 2021.

In J2, altitudes up to 75,000 feet can be simulated, along with temperatures from -60 to 450 degrees Fahrenheit. Flight speeds of up to Mach 2.6 can also be simulated.

The F135 program has conducted more than 5,500 hours of testing in test cells across AEDC.

ASTF added to provide T&E for advancing engines

In the 1960s, NASA and the Department of Defense Aeronautics and Astronautics Coordinating Board identified the need for a facility designed to test integrated, full-scale propulsion systems under more realistic simulated flight conditions. To support the test and evaluation of more advanced engine systems, AEDC leadership began planning for the addition of the world’s largest jet engine testing facility, known as the Aeropropulsion Systems Test Facility (ASTF), at Arnold Air Force Base.

By 1972, a design contract was awarded for ASTF, also known as C Plant. Construction on ASTF began in 1977, and then in October 1984, the new facility was completed. It cost $625 million to build ASTF, which sits on 57 acres at Arnold, making it the largest of the test facilities on base. Comprised of altitude test cells C-1 and C-2, ASTF is designed to test large military and commercial engines in true mission environments. It allows data which was previously only available after extensive flight testing to be acquired through ground testing.

Each test cell within ASTF is more than 25 feet in diameter and just under 50 feet long. The facility is capable of simulating flight conditions at altitudes up to 75,000 feet and at speeds up to Mach 2.3. Either cell can provide engine inlet temperatures of up to 350 degrees Fahrenheit and accommodate engines producing up to 100,000 pounds of thrust.

The C-1 test cell is typically used to conduct performance testing of large augmented turbine engines that power supersonic military fighters and bombers. While C-2 can also be used for testing these engines, the test cell has more recently been used for performance testing of large turbofan engines that power large commercial airliners.

Aeromechanical testing, vectored-thrust testing, icing testing and inlet pressure distortion testing may also be accomplished in ASTF.

In recent years, ASTF has been used to test F119 engines for the F-22A Raptor aircraft and F135 engines for the F-35 Lightning II aircraft. Turbofan engines such as the Rolls-Royce Trent 800 for the Boeing 777, the Trent 900 and GP7200 for the Airbus A380, the Pratt & Whitney 6000 for the Airbus A318, the Trent 1000 for the Boeing 787, the XF7-10 for the Kawasaki P-1, and the BR725 for the Gulfstream G650 have also been tested in ASTF.

“We are the beneficiaries of our predecessors’ foresight, technical skill and dedication,” said Lt. Col. Lane Haubelt, director of the Aeropropulsion CTF at Arnold AFB. “ASTF remains an extremely capable test facility and is the centerpiece of advanced turbine altitude testing for the nation. The task in front of us now is sustaining this world-class test capability while investing to keep ASTF the facility of choice for propulsion system test and evaluation over the next 35-plus years.”

Sea level engine testing at Arnold

In addition to the J, T and C test cells, the Propulsion Test Branch includes test cells with sea level testing capabilities. These cells, SL-2 and SL-3, were acquired in the late 1990s from the Navy base in Trenton, N.J., closing as a result of base realignment and closure.

SL-2 and SL-3 provide cost-effective durability testing of large augmented turbine engines at near-sea level conditions. Arnold AFB sits at approximately 1,000 feet above sea level.

Durability is assessed through accelerated mission testing, or AMT, which allows the simulation of a lifetime of missions in a matter of weeks. The facility can also support RAM AMT, in which air inlet pressures are higher than ambient. AMT and RAM AMT conditions can be alternated throughout a single test program to increase efficiency and reduce cost. In addition to AMT, SL-3 is equipped for specialized testing, such as corrosion testing.

In recent years, SL-2 and SL-3 have been primarily used to test F100 engines for the F-16 Falcon, F119 engines for the F-22 Raptor, and F135 engines for the F-35 Lightning II.

The Propulsion Test Branch continues to build upon this legacy of ground test and evaluation today.

“It was AEDC’s disciplined engineering and technical excellence that underwrote many of the advancements in American aerospace history,” Haubelt said. “Our team continues that tradition today. The rich history of propulsion ground test and evaluation here at AEDC instills a sense of pride in everything we do, and everyday provides us a new opportunity to continue that legacy.”