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JSF COMPETITORS CONTINUE TESTING

For Lockheed Martin's JSF crew it was work as usual on Saturday 16 December. At 9:23am local time that day the X-35C took off from the runway in Palmdale with test pilot Joe Sweeney at the controls, to be flown to nearby Edwards AFB. The Naval (CV) version of the JSF demonstrator which, compared with the X-35A, has enlarged wings and tails, remained airborne for 27 minutes.

After two preparatory flights on 19 December to check out the aircraft's handling, on 22 December the X-35C began its primary job of demonstrating its flying characteristics during aircraft carrier landings. For the purposes of practising carrier landings, the outline of a deck has been painted onto the runway at Edwards and an appropriate signalling system has been installed. The flight trials were shared initially between Sweeney and Brian Goszkowicz from the US Navy. Goszkowicz described the approaches as "stable and predictable". By the beginning of January the X-35C had completed over a dozen sorties.

In the adjoining hanger of the Joint Strike Fighter test unit at Edwards they were not twiddling their thumbs over the New Year either. For technical reasons (hydraulics problems which prevented high speed flying) Boeing had completed its aircraft carrier approach tests first, and on 21 December the X-32A broke the sound barrier. The aircraft passed Mach 1 at around 10,000m (3,000ft) altitude. Test pilot was Lt Colonel Edward Cabrera from the US Air Force.

One day earlier the X-32A had completed its first in-flight refuelling operation. The aircraft, fitted with a folding probe next to the cockpit, mated with the drogue of a KC-10A Extender from the 6th Air Refuelling Squadron without any problems. Philip Yates of the US Navy carried out this test manoeuvre at an altitude of 6,100m (20,000ft) and at a speed of 435km/h (235kt).

While the conventional take-off and landing (CTOL) JSF demonstrators continue their flight test programme, the short take-off and vertical landing (STOVL) versions are being prepared for their maiden flights. For example, on 8 January Boeing carried out the most important engine trials on the X-32B, during which the thrust from the rectangular nozzle at the tail was redirected to the two swivelling nozzles in the fuselage. The transition lasted between one and three seconds. On 9 January taxiing trials at low and medium speed were to be performed.

The first flight of the X-32B could take place in March. However, it will be carried out in the "normal" way. Only after some preparatory tests are transitions planned at higher altitude. These will require the lift nozzle system, currently undergoing fatigue testing at Pratt & Whitney, to be cleared for flight. To date over 500 trials have been carried out.

Fatigue testing of the lift system for Lockheed Martin's X-35B will be completed in March at the earliest. Hover pit testing of the aircraft is to commence in February. To this end the lift fan was mounted behind the cockpit of the first prototype, which had previously undergone flight testing as the X-35A, at the end of December in Palmdale.

While Boeing sees its exhaust nozzle system as a logical and low-risk further development of the "battle-proven" Harrier, Lockheed Martin is trumpeting the advantages of its patented new technology, such as a cooler footprint on the ground. For the lift fan is driven through a shaft of the Pratt & Whitney JSF119-611 powerplant and blows out cool air. It delivers 80kN of thrust, the same amount as the tail nozzle swivelled downwards. This means that drive shaft, gearbox and clutch must handle a huge power output, the difficulties of which were reflected in a number of problems during development. However, according to the manufacturer the latest version should function without any trouble after detail improvements have been incorporated recently.

From page 86 of FLUG REVUE 3/2001