Originally Posted by M2Dude
Actually Rolls Royce always told me that the (new) Type 28 secondary nozzle was a bit of a dissapointment. Aerodynamically it was a far better interface with the wing from a drag point of view than the original design, but fell short of it's design promise in terms of performance. The design responsibility for the secondary nozzle system awarded to the French engine manufacturer SNECMA.
Well as that well known lady Randy Mice-Davies said " They would say that wouldn't they" (That shows my age!)
Seriously, they couldn't possibly know that the new nozzle fell short of it's design promise. There was no means of measuring thrust in flight installed on the aircraft and even if there had been the possible precision would not have allowed one to make such judgement. The only certain thing in aircraft design is weight, and that could be established unequivocably - it was lighter than the original. Any aerodynamicist looking at the two designs could tell you that the drag of the TRA (Tuyere Reverse Aval) was going to be less than that of the prototype nozzle, but establishing an exact value was another matter.
For the record. the idea of a new design originated in Sud Aviation. The development of the design was entrusted to a joint BAC/RR/Sud/Snecma team (I was one of that team, so maybe I am biased!). Snecma were not very keen on the idea of a new nozzle, largely from pride and a strong NIH factor, but one could not in fairness blame them for any performance shortfall - it was a joint effort.
CliveL