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Technology update
JSF propulsion testing
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Lockheed Martin JSF propulsion team validated its STOVL propulsion system with a lift fan high-power clutch engagement during testing at Pratt & Whitney's West Palm Beach, FL, facility.
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Moving along with its development of the Joint Strike Fighter (JSF) propulsion system, Lockheed Martin has recently validated its Short Takeoff and Vertical Landing (STOVL) and conventional engine configurations. Testing of the STOVL shaft-driven lift fan high-power clutch engagement was conducted at Pratt & Whitney's facilities in West Palm Beach, FL, while testing of the Pratt & Whitney JSF119-611 engine was performed at the Arnold Engineering Development Center (AEDC) C-2 and J-2 test cells at Tullhoma, TN.
During STOVL testing, the lift fan was engaged by the clutch and locked to the driveshaft while the JSF119-611 developmental engine was operated above its typical in-flight conversion power setting. This was done to simulate the propulsion system's seamless conversion from the conventional flight configuration to the STOVL approach and vertical landing. The system was then converted back to the conventional mode via computer control, without any engine or lift fan anomalies.
Earlier STOVL testing demonstrated lift fan engagements at varying speeds from idle to 75%, which are typical of short or vertical takeoffs. The purpose of this testing was to verify the lift fan's capability of engaging and disengaging at any engine speed, and under a variety of conditions.
Another JSF119-611 developmental engine was used to complete conventional configuration testing. More than 330 h of altitude testing was conducted on this engine in the AEDC C-2 and J-2 test cells. The tests validated the complete X-35 (Lockheed Martin's JSF demonstrator) flight envelope, with good operability demonstrated throughout.
Engine control logic for all three JSF aircraft variants - conventional takeoff and landing, carrier capable, and STOVL - was also successfully tested. Successful augmentor operation was verified for both the conventional and STOVL (three bearing-swivel) augmentor ducts. This also confirmed an acceptable air-start envelope for the demonstrator.
Other testing and development work on the conventional engine configuration included structural evaluations, component evaluations, performance development, operability and stability development, controls development, and augmentor/nozzle development. Another demonstrator engine is scheduled for delivery to AEDC for final altitude flight qualification testing this fall.
Completion of conventional engine and STOVL lift fan testing puts the Lockheed Martin JSF propulsion system on track for the X-35's first flight scheduled for next year. Government selection of a contractor for the JSF Engineering and Manufacturing Development phase is scheduled for 2001.
Frank Bokulich
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