Boeing lead STOVL test pilot Dennis O'Donoghue took the Pratt & Whitney F119-614 engine to maximum thrust over the Boeing engine run pit in Palmdale. During the engine runs, the test team, including Pratt & Whitney and Rolls-Royce, repeatedly redirected engine thrust from the aircraft's cruise nozzle to the lift nozzles and back again. The tests confirmed lift systems operations and verified system integrity.
"The successful tests demonstrated the ease in conversion between conventional and STOVL flight modes — a key advantage of the direct-lift configuration," said Katy Fleming, Boeing JSF system test director. "This was another important step in proving the low-risk aspect of our concept as we move toward the start of X-32B flight testing.
"Additionally, we demonstrated lift nozzle vectoring at high power, highlighting the operational flexibility of direct-lift."
To perform STOVL flight, the system closes the rear exhaust nozzle and redirects engine thrust downward through lift nozzles. For conventional flight the lift nozzles are closed and thrust flows rearward through the two-dimensional thrust-vectoring cruise nozzle — the same as in the X-32A — to propel the aircraft forward and to supersonic speeds. Afterburner is not used in STOVL flight.
The capability to quickly vector the lift nozzles at high power settings will enable the JSF to make rapid transitions to and from wingborne flight and hover. In breaking with the old way of doing business, Boeing will demonstrate X-32B vertical lift with a transition to hover from wingborne flight, rather than the old method of progressing from tethered hovers to a free-air hover.
Boeing plans to demonstrate transitions during X-32B flight test, before performing vertical landings.
"We have a high degree of confidence in our ability to hover and execute vertical landings based on modeling data and simulations, as well as results from engine runs on the test stand," Fleming said.
The X-32B will demonstrate the company's direct-lift approach to the STOVL requirements for the U.S. Marine Corps and the United Kingdom's Royal Navy and Royal Air Force. Previous X-32B STOVL milestones include:
Boeing has 30 years of experience with direct lift — the only combat-proven approach to STOVL flight. The company is leveraging that experience into a new design that incorporates significant improvements to ensure the services receive a true "third-generation" low-risk STOVL solution that is more capable, reliable, affordable and easier to fly than STOVL aircraft operating today.
In more than 1,300 trials on the STOVL engine test stand, transition times between conventional and vertical thrust and back again have been accomplished consistently in one to three seconds. This rapid and direct transition capability is critically important for unrestricted STOVL operations and aircraft safety.
Underscoring the commonality of its JSF design, Boeing used its X-32A to demonstrate aircraft-carrier and conventional-takeoff-and-landing handling qualities.
The Boeing X-32A completed its flight-test program Feb. 3 after 66 flights and 50.4 flight hours with six different pilots in the cockpit.