Stewart Penney/LONDON

Lockheed Martin has pushed back the first flight of the X-35B short take-off/vertical landing (STOVL) version of its Joint Strike Fighter until early June.

Tom Burbage, Lockheed Martin executive vice president JSF, says that the delay has been caused primarily because Pratt &Whitney needs to complete an accelerated maturity test (AMT) of the JSF119 powerplant. The AMT is critical to receive clearance to fly the X-35B. Initial flight had been expected in April.

Before the X-35B flies it will complete a series of tethered tests attached to a balance for force and moment measurements and a number of low hover tests - known as press-ups - that are expected to kick off in late April/early May.

Burbage says eight weeks have been allocated for AMT, although it could take half this time if all goes well. Meanwhile, Lockheed Martin is seeking clearance for a series of tests in the middle of the flight envelope. These are considered low risk compared with STOVL operations. Starting these trials earlier would allow the inclusion of additional flight data in the proposal to be delivered to the US Department of Defense by mid-August.

The Lockheed Martin executive says that by the end of January the engine had run for around 300h, while more than 200 engagements of the clutch - which links the main propulsion engine to the lift fan drive shaft - had been completed.

Burbage says that earlier problems with the lift fan have been overcome by developing a running-in procedure for the system so that bearings and other mechanical components can bed down.

For the engineering and manufacturing development (EMD) aircraft, Burbage says Lockheed Martin and its team have reviewed the "engineering hardware" and identified "simplifications" to improve the systems.

The X-35C carrier version is soon to fly to the US Navy's Patuxent River test centre to start 30 days of trials.

Boeing and Lockheed Martin are due to submit their EMD proposals to the DoD on 8 February. After a six-to-eight week bid evaluation, a series of questions will be issued and possibly direction to modify the proposals. Final proposals are due around 15 August with selection expected to take four weeks.

Contract negotiations are expected to stretch into early 2002, although Burbage says work is on-going to shrink the time between selection and contract signature.

Source: Flight International