Hempy,
Thanks for the kind wishes.
The challenge for designers and engineers is that the performance envelope is always being pushed. This is true for all combat aircraft systems, especially propulsion. The F135 is an extremely advanced engine, with a number of novel features. Many of these are firmly 'US eyes only', but my (slightly informed) guess is that it is pushing the boundaries in all areas.
When you do that, you run the risk of the unexpected. This appears to have happened here. It's not at all unusual for new engine programmes, and as I've posted before, the 135 appears to have delivered well to date.
I suppose that, as an engineer, I expect problems. I don't want them to happen, but they usually do.
LO, we could trade engine performance figures for some time, the only common factor being that neither of us has access to the actual data needed for a comparison. All I will say is that if the 135 had not delivered on its thrust/weight targets, the F-35B would not have passed the major review of a few years ago. What I can say is that when I left the programme some years ago, the engine was on target for weight, and was starting a further weight reduction plan that had been applied by the DoD as a 'stretch' target.
During the F-35B weight reduction plan, the propulsion system was required to achieve further reductions, one of the major changes arising from that was re-engineering the 3BSD from steel to titanium. RR's performance on this effort was described to me as 'absolutely stellar' by some hard bitten engineers at Fort Worth. Other areas of work on the propulsion system, led by talented young Brits, generated significant improvements in VL thrust efficiency.
My bottom line - I believe that the F135 driven propulsion system for the F-35B is meeting its weight and performance targets. Others may (and probably will) differ.
Hope this lot is of some interest,
Best regards as ever to those actually crunching the numbers,
Engines