Installation of Rolls-Royce-manufactured lift-fan nozzle in F-35B centre fuselage marks assembly milestone

Northrop Grumman is preparing to begin installation of the first Rolls-Royce-produced variable area vane box nozzle (VAVBN) module into the main keel of the first Lockheed Martin F-35B Joint Strike Fighter (JSF) development aircraft at its Palmdale site in California.

The VAVBN, developed by R-R as part of the common lift system for both Pratt & Whitney F135 and General Electric/Rolls-Royce F136-powered F-35B short take-off and vertical landing (STOVL) variants, is the first hardware in the aircraft assembly sequence and is therefore the pacing item for the start of final construction.

The structure consists of six variable titanium vanes arranged like venetian blinds in a aluminium box-like housing that forms an integral part of the main keel and is designed to remain in place throughout the aircraft’s 30-year-plus service life. The VAVBN vectors the 20,000lb-thrust (89kN) of the R-R-developed two-stage lift fan through 54° in less than 2s. The nozzle, which has variable- area capability unlike the original articulated, hooded-nozzle design of the original X-35 concept demonstration aircraft (CDA), also operates as a primary flight control during jet-borne operations.

The remaining elements of the lift system, including the Indianapolis, Indiana-produced lift fan and the R-R Bristol-supplied three-bearing swivel and roll posts, are not scheduled for delivery to Palmdale until the second quarter of 2006. Deliveries of production STOVL lift systems will start in early 2007, with the first F-35Bs scheduled to begin deliveries as part of Lot 2 low-rate initial production in 2008.

Design of the VAVBN presented unique challenges, says Scott Marr, programme director for the Indianapolis lift fan, because “it is a dual purpose unit. It forms part of the aircraft structure in the centre fuselage and it also is used for flight control. It therefore carries a lot of both aerodynamic and structural load and redirects the flow of the lift fan slightly forward to help with the centre of gravity and moment arm.”

The unit is also dramatically lighter and smaller than its CDA predecessor, weighing around 35% less and being reduced in overall height by around 50%.


Source: Flight International