F-35 Cancelled, then what ?

[Engines]

MOSOCS, Glad,

Again, just trying to help - here's some detail on the weapons bay development.

The JORD requirement for weapons bays had a very significant impact on the JSF designs. In any high speed combat aircraft, internal volume is at a premium, and having to include the volume of two bays really drives the design in many ways.

When the modelling was being done by the DoD JSF Team to support JORD development, it became clear that the STOVL variant would face even greater pressure on internal volume, due to the need for the lift fan and other lift system components. As a result, the JORD's internal carriage requirement for the STOVL was set at two 1000 pound JDAMS and two AIM-120. (Not quite a bag of sugar). The A and C retained the 'two by 2000 pounders and two AIM-120' requirement.

Early in the design process, LM's weight and volume estimation tools were very poorly suited to the F-35 (they were derived from experience on F-16, where all stores are carried externally). Reliance on these led to overoptimistic weight forecasts and in turn led LM to (foolishly in my view) adopt what they called the 'common weapons bay', which would allow the F-35B to take a 2000 pound weapon with a change of doors, as well as reducing the differences between the B and the other two variants.'Commonality' of production was a big driver at that stage (around 2001/2). Notably, the JORD was not changed.

Unfortunately, the F-35 with the common weapons bays was an unachievable design. LM could not get the centre/aft fuselage internal layout to work, and badly designed load paths generated even more weight. It may interest some people reading this to note that while the STOVL variant suffered first, weight problems were very nearly as bad for the A and the C. Despite repeated warnings (mainly from the USN's highly experienced weight estimation team within Navair) LM kept going with the design until late 2003/early 2004 when the US Government effectively pulled the plug on them and directed them to redesign the aircraft to get weight back to a sensible level.

The F-35B bays were redesigned to what was called the 'spec compliant' configuration, built around the (still extant) JORD requirement, and the whole centre/aft fuselage was 'restacked' to get items in the right place at the right weight.

Hope all this stuff is of some interest - as ever, happy to respond to PMs if that would help.

Best regards as ever to all those trying to get all the bits in and working

Engines