The F135 short takeoff/vertical landing (STOVL) variant propulsion system, which includes the Rolls-Royce LiftSystem, has exceeded thrust performance expectations in recently completed tests, providing more vertical power than required by the F-35 Lightning II STOVL aircraft. The testing was conducted on a specially instrumented "hover pit" at Lockheed Martin in Fort Worth, Texas.

"The F135 engine continues to exceed performance expectations to deliver the most advanced, capable fifth generation fighter engine for the F-35," said Warren Boley, vice president, Pratt & Whitney F135/F119 Programs. "The engine demonstrated 41,100 pounds of vertical thrust against our requirement of 40,550 pounds. This means we will deliver excellent margin for the vertical landing and short takeoff performance for our STOVL customers."

During hover-pit testing, the aircraft is anchored to a metal grate 14 feet above a sloped concrete floor, separating the jet from ground effect and enabling it to simulate free-air flight. Sensors measure thrust and the aircraft's response to pilot inputs. This is a highly integrated software driven airplane where the testing also demonstrates functional operation of all systems required for vertical flight.

This includes control of the doors associated with the STOVL propulsion system: engine auxiliary inlet, LiftFan inlet, LiftFan exit, roll posts, and doors that open to enable the Rolls-Royce three-bearing swivel duct to articulate and vector engine thrust. The hover-pit tests are the final series of ground tests before airborne STOVL testing begins. The F135 STOVL propulsion system includes the Pratt & Whitney main engine and the Rolls-Royce LiftSystem components.

FMI: www.jsf.mil, www.pratt-whitney.com