P51

[Romulus]

P-51 started with the Allison V-1710 engine, piss poor performance above 15000ft, faster than a VB Spitfire up to this level, slightly better until 25000ft after which the Spit was way ahead (as it was in terms of manoeuvrability at all altitudes).

April 30 1942 Ronald Harker (RR test pilot) took a 30 min flight in a Mustang, noted the power fall off at altitude and suggested the Merlin 61 with 2 stage supercharger would be ideal. First flies as such on Oct 13 1942 with exceptional results, 70mph faster, climb rate 50% greater than a P51A. US conversion and refinement flew 30 Nov 1942, roughly the same speed but even greater rate of climb (double P-51A).

First Merlin Mustangs saw action Oct 1943, first "bubble" canopy 17 November 1943 which ultimately became the P-51D after the teething problems were generally sorted.

No production Griffon engined P-51 built, considered but discarded as it was too large and the surprisingly good results of the two stage supercharger meant the Merlin 61 was a much better option.

as for piston-jet combat standard tactics for dealing with 262s was to bounce them as they came in to land due to spool up time of early jets. Significant numbers were shot down in this manner, the Luftwaffe response was to have 190s providing cover as the 262s returned. Various Allied aircraft undertook these ops.

Hope this helps