Proposed timeline will see initial operational capability deferred to 2012, but anxieties lessen on weight issues
The F-35 Joint Strike Fighter (JSF) programme will seek approval this week for schedule changes that will delay delivery of the first operational unit by two years to 2012, but restrict the slippage to the type's overall development schedule by only one year.
The proposed schedule, which will be put forward for approval on 17 June, was unveiled last week at the American Helicopter Society's annual forum in Baltimore, Maryland. It will see initial operational capability (IOC) for the US Marine Corps' F-35Bshort take-off and vertical landing (STOVL) variant slide from 2010 to 2012.
IOC for the US Air Force's conventional take-off and landing F-35A would also come two years late, in 2013, but an overall one-year development delay would be preserved by also delivering the US Navy's first operational F-35Cs in 2013.
The IOC date for the UK is "yet to be determined", but programme officials indicate a less-capable F-35 version could be delivered on time in 2012, and later upgraded to the full-up weapon system standard (Flight International, 8-14 June).
John McKeown, JSF technical director, says the schedule changes will be presented later this week to the Pentagon's Defense Acquisition Board. He adds that the IOC dates are considered highly fluid, as these will partly depend on how each service defines the IOC criteria.
Other schedule changes include delaying first flight of the USAF's F-35A by eight months until August 2006. The USMC's F-35B would follow roughly one year later, and the navy's F-35C carrier variant would make its first flight in September 2008.
Meanwhile, weight concerns appear to be fading within the JSF programme. McKeown says he is comfortable that conservative estimates of the planned weight saving changes should fix the problem, which includes about 1,130kg (2,500lb) of excess weight for the STOVL F-35B, and about 680kg extra for both the air force and navy variants.
For the STOVL version, engineering improvements alone will not close the gap, so the programme is considering a range of tweaks to the aircraft's performance envelope. However, its eight key performance parameters will not be affected. Rather, minor requirements could be reduced, such as trimming approach paths after a wave-off on landing, conserving precious kilogrammes in the aircraft's bring-back fuel reserve.
The programme, however, has rejected proposals to offset extra weight by squeezing more thrust from the propulsion system, says McKeown, as slightly increasing the power limits would have a negative effect on the engine's service life. The programme is also seeking to avoid weight reductions that require trade-offs in other performance areas.
STEPHEN TRIMBLE / BALTIMORE
Source: Flight International
