Paul Lewis /Washington DC
Boeing and Lockheed Martin successfully complete STOVL trials on consecutive days The Joint Strike Fighter (JSF) programme has passed the last and perhaps most critical milestone of the four-year concept demonstration phase with the Boeing X-32B and the rival Lockheed Martin X-35B completing first full hovering flights within a day of each other.
Lockheed Martin began its X-35B short take-off vertical landing (STOVL) flight test programme on 23 June with a vertical take-off and landing over a hover pit at Palmdale, California, which is 2,430ft (740m) above sea level.
This was followed the next day by the Boeing X-32B transitioning in flight from wing-borne to full jet-borne hover at 200ft at NAS Patuxent River, Maryland.
The X-32B and X-35Bbuilt up to the hover from opposite ends of the STOVL flight envelope. TheX-35B did a series of "push ups" from the ground. The final step was a sustained 2min stabilised hover with a 1,590kg (3,500lb) fuel load with the aircraft's Pratt & Whitney JSF119-611 and shaft-driven lift fan generating 34,500lb-thrust (153kN) of powered lift.
X-35B STOVL testing now shifts to nearby Edwards AFB and the start of transition testing, gradually slowing the aircraft in flight to a stationary hover. "The great thing is having achieved this hover, I'm coming back to a known point and this allows us to be more aggressive in the build down," says Simon Hargreaves, lead X-35B and BAE Systems test pilot. The X-35B's critical test will be engagement of the lift-fan clutch and transitioning to the hover from wing-borne flight, due to take place this week.
Boeing has completed its build down from wing- to jet-borne flight on 24 June. The aircraft was decelerated below 40kt (74km/h) and put into a steady hover at 200ft with a minimal 770kg fuel load. During several flights on 24 June, the X-32B clocked up 8min of hover time and was manoeuvred through three axes. The first vertical landings were on 27 June, carrying 910kg of fuel.
"We're beating predictions for hover performance by quite a lot," says Dennis O'Donoghue, Boeing X-32B lead pilot. The X-32B will next take-off vertically from a hover pit and land, before it and the X-35B will do a full short take-off, up-and-away to supersonic flight, to test the flight control system from standstill to high speed.
Source: Flight International
