Pratt & Whitney’s F135 short takeoff/vertical landing (STOVL) variant propulsion system for the F-35 Joint Strike Fighter took one more step toward government certification recently with the successful completion of thermal testing, the company said yesterday.

Pratt & Whitney is a United Technologies Corp. [UTX] company.

The high temperature margin test, which took place at Arnold Engineering Development Center (AEDC) in Tennessee, involves intentionally running the engine to turbine temperatures beyond design conditions while simultaneously operating the turbomachinery at or above 100 percent of design conditions.

“While these are conditions the F135 engine will not experience during normal field operations, the purpose of this test is to demonstrate design margin at the most extreme operating conditions that could possibly exist,” said Tyler Evans, director of F135 programs. “This is without a doubt one of the most demanding tests for an F-35 engine and the F135 passed the test with flying colors.”

The test also demonstrated the F135 propulsion system’s ability to produce margin relative to thrust with this engine producing 28 percent more thrust than the specification requirement.

The engine is now scheduled to complete STOVL powered lift performance qualification testing in West Palm Beach, Fla., one of the last steps before receiving Initial Service Release qualification from the government.

The F135 has completed more than 19,000 hours of testing. The Conventional Takeoff and Landing (CTOL)/Carrier Variant (CV) engine received Initial Service Release (ISR) in February, indicating that it is now cleared for use in the field. The STOVL engine is expected to receive ISR certification before the end of the year.

Pratt & Whitney has delivered all flight-test engines required for the program as well as the first 10 production engines.