Hi Neil,
>Drag and trim changes on Spitfire, Mustang and Thunderbolt in flight at high mach numbers.
Wow, that's EXTREMELY cool information! :-) Do you have the corrosponding Mustang and Thunderbolt charts, too? I'd love to see them!
Note the right-hand column - that's energy.
Interestingly, during the dive from 40000 ft to 30000 ft, the Spitfire hardly loses any energy. This initial dive seems to be slightly "unloaded" judging from the acceleration column. The change in elevator angle doesn't look like a result of trim changes, but rather like the begin of the pull-out (or at least some pulling up).
Of course, the elevator forces are not indicated, so it's hard to say how good the handling qualities were in the dive. The maximum Mach number of 0.89 is quite impressive! Interestingly, it coincedes with the maximum Mach number an unmodified Me 109G airframe reached during similar tests.
The Me 109G was limited in the dive by aileron overbalance, probably indicating aeroelastic deformation of the wing. The Spitfire had the same method of wing construction and also suffered from some aeroelasticity problems. Mike Ssalamander's "Up in Harm's Way" gives some good insights on the Spitfire, and Radinger/Otto/Schick's description of the Me 109 diving trials leads me to believe that in the Me 109, you had to be careful with roll inputs during a dive just in the same way.
Regards,
Henning (HoHun)