JPT and engine RPM do not correspond to thrust on 100 series Avon . It does if no faults. However any problem with the bleed valve system with correct indications but lack of thrust .The report states BVCU was ok on strip but any leak on a connection will cause problems which couldn't be checked. Anyone remember the problems in the early 80's when we were doing bleed valve checks on a run at the end of every days flying due to a problem with diaphram material in the BVCU until they were all modded ? On the 200 series engine the thrust was checked on an airtest if i recall by checking that the brakes wouldn't hold at full power. Not enough power on 100 series for this. Many times spent extended times in the run bay setting up the BVCU . How much of that experience is around now as the manuals of that era don't have the detail ?