[Graham Boak]

I do believe in results taken from a wide range of aircraft from several manufacturers, several nations and years of testing, challenged and confirmed over decades of design and flight. Some may prefer single unsupported anecdotes but a solid backlog of evidence is how engineering actually works. If you actually believe that key design engineers are all pencil-pushing wankers, that reflects only on the credibility of your contributions.

That said, more politely than the comment deserved, this anecdote does have the advantage of being specific to type. It is possible that the wing design was not the critical factor with the Tempest. It is always possible to do worse than the optimum, if never better. For example the P-38, despite its thick wing (as acknowledged by Kelly Johnson), the limited factor is generally thought to be due to interference between the fuselage and the nacelles. The Tempest has no such multi-body interference, but perhaps some other factor came into play? There seems to be no obvious candidates.

However, we also have the evidence of the maximum speeds presented in the manual. Without allowing for the unknown pressure errors it is impossible to be precise, but they suggest a Mcrit of the Tempest around 0.9. For the real Mcrit to be 0.82 would require a stonking pressure error, not unheard of on thick-winged draggy aircraft such as the Vengeance (which has been claimed as supersonic – yeah) but exceedingly unlikely here.

It would be interesting to round off this sub-thread with the equivalent maximum speeds for the Typhoon, if anyone has access to them? Just how close are they to those of the Tempest? They might appear misleading close, if the PEs of both types differ. Does anyone have the Pilot’s Notes for each type?