Guy Norris/LOS ANGELES
Boeing and Lockheed Martin Joint Strike Fighter (JSF) concept demonstration development teams are tackling emerging problems with the short take-off and vertical landing (STOVL) propulsion systems. But both companies insist that the first flight target dates will still be met.
Boeing's problems with the Pratt & Whitney JSF119-614 are thought to centre on development and verification of the software for the X-32B integrated flight propulsion control (IFPC) system. This handles the transition from vertical, jet-borne flight, to horizontal, wing-borne flight by integrating flight control and engine inputs, while making it transparent to the pilot.
"We are looking at several weeks behind schedule," admits the US manufacturer. "But that is due to the normal software and hardware development issues that are associated with a direct lift system. We are working those risk items, but there is no threat to the first flight in the summer of 2000."
Rolls-Royce, which is developing the rear nozzle, roll off-takes and other hardware elements of the direct lift system for the -614, denies that the delay is linked to the late delivery of key components earlier this year. The engine maker says provision for the delay was absorbed into the development schedule when it became apparent that there would be delivery delays.
Pratt & Whitney, which is integrating and testing all four JSF engine derivatives at its West Palm Beach site in Florida, declines to be specific about the problems but says: "Certainly the full system integration of STOVL is a key challenge, and development of a reliable software package could be an item pacing the programme."
The US engine manufacturer completed assembly of the first -614 flight test engine on 11 November and expects to deliver it to Boeing's X-32 Palmdale assembly site later this month (December). The engine will power the conventional take-off and landing (CTOL) X-32A, which is expected to make its first flight around April next year, and is one of six developmental, qualification and flight test powerplants being built for the Boeing JSF.
Problems with the JSF119-611 (above) powering Lockheed Martin's X-35 concept demonstrator have also been tackled by P&W, which says a recent compressor seal and high oil consumption issue has been fixed with a seal re-design. R-R, which provides the two-stage lift fan for the X-35, is working to catch up after modifying the oil system.
The redesign was carried out after an oil consumption problem with the second lift fan was found while on rig tests at P&W. "We discovered oil blowing by the carbon seals," says Tom Hartmann, R-R Fighter and Trainer programmes vice-president. "The problem occurred mainly at an idle condition".
The fix "has taken a bit of time, so we have changed the schedule, but not killed it". The remaining tests are aimed at "must have" data, rather than "like to have" says Hartmann. "We've been pushed by the Joint Programme Office to hold the schedule as advertised". Lockheed Martin says that a first flight of its STOVL contender is still set for the third quarter of 2000.
Source: Flight International
