By Emelie Rutehrford
The Marine Corps’ Joint Strike Fighter (JSF) variant should fly for the first time in conventional mode this month and make its maiden short-take-off-and-vertical-landing (STOVL) flight around the first of the year, according to airframe builder Lockheed Martin [LMT].
The F-35B STOVL variant of the stealth fighter is expected to embark on its first flight “probably within the next week or so,” Lockheed Martin spokesman John Smith said last Friday, though a specific date had not been set at the time.
The F-35B’s shaft-driven lift fan propulsion system–that will enable the fighter to make the short takeoffs and vertical landings for which it is intended–operated for the first time in the aircraft during ground testing on May 25, the company said last Friday.
A test pilot performed two conversions from conventional to STOVL mode when the aircraft was anchored to a hover pit at Lockheed Martin’s STOVL test facility in Fort Worth, Tex., according to a Lockheed Martin press release.
“The F-35B’s STOVL propulsion system operated exactly as expected, providing the power output that our models forecast and transitioning very smoothly from conventional to STOVL-mode and back,” Bobby Williams, Lockheed Martin vice president and F-35 deputy program manager, said in the release.
Before the first flight in the coming weeks, the F-35B is conducting a final series of ground tests.
The aircraft is flying in conventional mode during the initial test flights “to evaluate overall flying qualities and airworthiness,” the company says.
The Pentagon’s purchase of a half dozen F-35Bs hinges in part on the upcoming conventional-mode flight. When Pentagon acquisition executive John Young approved the purchase of additional JSFs in April, as part of a Low Rate Initial Production II stage, he said six STOVL variants could not be bought until the F-35Bs have a successful first flight (Defense Daily, April 15).
The program has had some hiccups. During proof testing in February, a third-stage turbine blade of the F135 engine vibrated while at very high frequencies at a stress level that can cause it to crack, and cracks and holes were discovered, according to F135 engine developer Pratt & Whitney [UTX] (Defense Daily, March 20). A similar fatigue issue had been discovered last August, during an early phase of the qualification program.
“Our aim is to retire technical risk well before we deliver F-35s to the fleet,” Williams said.
The JSF STOVL variant is expected to reach initial operating capability in 2012.
Current plans call for the F-35B to be moved the Naval Air Station in Patuxent River, Md., early next year, though Smith said it has not been decided if the initial STOVL flights planned for December or January will be in Fort Worth or in Patuxent River.
The JSF effort–which is developing variants for the Air Force, Marine Corps and Navy–is the Air Force’s largest acquisition program.
Lockheed Martin is developing the F-35 with partners Northrop Grumman [NOC] and BAE Systems. In addition to Pratt & Whitney, a team made up of General Electric [GE] and Rolls-Royce is developing a second engine–the F136–for the JSF, though it is not as far along in development as Pratt & Whitney’s F135.