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A Fourth F-35 Variant?

Andrew Hartland
RUSI Defence Systems, 15 June 2018
Aerospace, Air Power and Technology
With an inherently high thrust-to-weight ratio and modified digital flight control system, an F-35 variant could operate off the Queen Elizabeth class carriers with fewer penalties to the baseline F-35A design than the current F-35B and hence fewer performance trade-offs

The UK is due to start operating it’s F-35B fleet from RAF Marham this year. The UK F-35 order has fluctuated between the F-35B short takeoff and vertical landing (STOVL) variant and the F-35C carrier vessel (CV) variant. It seems that that the UK would really have preferred the F-35C because of its longer range (nominally 800 nm versus 700 nm for the F-35A conventional takeoff and landing (CTOL) variant and only 500 nm for the F-35B STOVL variant) but has reluctantly accepted that the cost and manpower requirements of installing the necessary catapaults and arresting gear on the new Queen Elizabeth class aircraft carriers makes this prohibitive, and hence has reverted to the F-35B.

Current F-35 Variants

The F-35 programme was based on the concept that a single airframe design could be produced in three variants to satisfy the differing requirements of the US Air Force (USAF), US Marine Corps (USMC) and US Navy (USN). The primary difference between the three services’ requirements was in take-off and landing capabilities and are listed in Table 1 below. The USAF aircraft, which will be procured in the largest numbers, operates from conventional runways. The USMC aircraft will operate from 40,000 ton class ships such as the USN amphibious assault ships (LHDs) and forward airstrips. The USN aircraft operates from 90,000 ton USN carriers using catapaults for take-off and arrester wires for landing. The UK was brought into the programme at an early stage to take advantage of British STOVL expertise borne out of the Harrier programme and to provide a repacement for the Royal Navy Sea Harrier fleet.

 The danger inherent in this multi-service approach within the F-35 programme was that the USAF CTOL variant that would be produced in the largest numbers would be compromised by the need to accommodate STOVL and CV variants within a common airframe. Officially these so called ‘scar’ penalties have been avoided (although the CV variant has a 35% larger wing than the other two), but is hard to believe that the fuselage of the CTOL and CV variants would have been shaped as they are if there had been no need to make space provision for the lift fan behind the cockpit in a common fuselage. If the airframe designs had been allowed to diverge it appears better optimised CTOL and CV variants would have been possible, while still retaining avionics and engine commonality (where much of the cost resides).

 Table 1. F-35 Variants

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