To RAAF HQRS
From OHQ RAAF KWAY
6 Sept 1943
Spitfire Aircraft Engineering.
5 Spitfire Mk 5 aircraft given extensive test fights here successively with each of the following types of of air intake assembly and engine cowling. (A) original tropical (B) New Tropical with bypass valves (C) Temperate.
Average max speeds were
1 sea level) A) 312 B) 312) C) 316
2 10000ft) A) 355.5 B) 355.5 C) 360
3 at FTH ) A) 357 B) 358.5 C) 363
Considered that improvements in speed were too small to warrant departure from original type tropicalization hence new scheme will not be applied retrospectively to Mk5 aircraft. Latest tropical intake with bypass valve will be incorporated Mk 8 aircraft.
from Australian Archives:
Title
DTS [Directorate Technical Services] - Spitfire Aircraft - Performance comparison - tropical and non-tropical types
Contents date range
1942 - 1944
Series number
A705