Aircraft peformances, is this joke ?

[jf1981]

Originally Posted by winny

I can add some more to this, the figure that is usually quoted for a MK I Spitfire is 362mph at 18,500. This was referring to K9787, the first production Spitfire, in 1938. [...]

This is right

Prototype K5054 1050 bhp at 16'000 ft at 3000 rpm 6 1/4 psi boost reached nearly 350 mph.

Merlin II engine was 1050 bhp at 6.25 psi boost (octane 87) and 1300 hp at 12 psi boost (octane 100) but shortening lifetime by a factor of 10 (100 hours to 10 hours).

-------------
Mk I

Martlesham Heath, 6 january 1939. K9787. Merlin II performance trials.
Cruising 318 mph @ 15'000 ft
Max spd 362 mph @ 18'500 ft
6.5 min to 15'000 ft (2300 fpm mean)
22.4 min to 30'000 ft

-------------
Mk I
May 1939
295 mph @ 1'000 ft
276 mph @ 20'000 ft
(I assume this is IAS)
-------------
Mk II

Spitfire serial K9788 was tested with merlin XII (the Mk II engine) with following results :

Boost 7 lb 366 mph @ 18,900 feet
Boost 9lb 369 mph @ 16,700 feet
Boost 12 lb 372 mph @ 13,450 feet