Geoffrey Sinclair
Staff Sergeant
- 1,093
- Sep 30, 2021
AVIA 6/10393 Effect of Equipment on Spitfire Top Speed, Calculated Corrections at 360 mph, difference between ideal and variation
Spitfire V EN946
Total projected increase in speed 30 mph, measured increase 30 mph
Speeds in mph assuming modifications done. NOTE: Ideal speed aircraft would NOT be combat worthy.
Spitfires listed as tested, prototype K9793, Mk I N3171, X4257, K9787, Mk V K9788, N3053, X4922, W3134, AA787, AA937, AB873, EF644, EN946 (original and RAE modified), Mk IX N3297, BF274, JL227, EN498
Various parts A&AEE report 692
RAE Technical Note Number Aero 1217 (Flight) June 1943, Improvement of performance of Spitfire EN946
RAE Technical Note Number Aero 1246 (Flight) July 1943, Comparison of three production Spitfires
| Equipment | Ideal Condition | Variation | Correction mph |
| Exhausts | Multi Ejector | Original Mk I | 5.25 |
| Exhausts | Multi Ejector | Triple Ejector+Fishtail | 7.75 |
| Exhausts | Multi Ejector | Triple Ejector+Fishtail+Gun Heating | 9 |
| Air Intake | No snowguard | Guard fitted | 8.5 |
| Air Intake | No stoneguard | Guard fitted | 7.5 |
| Windscreen | Conical | Internal bullet proof | 4 |
| Windscreen | Conical | External bullet proof | 7.75 |
| Rear View Mirror | None | Faired | 3.5 |
| Rear View Mirror | None | Unfaired | 6.75 |
| Radio Mast | None | Standard | 1.5 |
| Radio Mast | None | Whip | 0.75 |
| Armament | No protruding cannon | Two cannon | 6.25 |
| Armament | No protruding cannon | Two cannon+2 stubs | 8.5 |
| Cannon fairing bulges | None | Small | 0.5 |
| Cannon fairing bulges | None | Large | 1.5 |
| Ejector chutes | Flush cut | Projecting from wing surface | 1.25 |
Spitfire V EN946
| Equipment | Original | Final | Correction mph |
| Exhausts | Triple Ejector+Fishtail | Multi Ejector | 7.75 |
| Air Intake | External snowguard | Removed | 8.5 |
| Rear View Mirror | Rectangular unfaired | Circular faired | 3.25 |
| Radio Mast | Standard | Whip | 0.75 |
| Ejector chutes | Projecting | Cut Flush | 1.25 |
| Total Above | All | All | 21.5 |
| Finish | Ex Factory | Smooth | 8.5 |
Speeds in mph assuming modifications done. NOTE: Ideal speed aircraft would NOT be combat worthy.
| Aircraft | As tested | Ideal speed, normal finish | Ideal speed and finish | Equipment Effect | Finish Effect |
| Prototype Mk I | 367 | 383 | 383 | 16 | 0 |
| Production Mk I | 357.7 | 378.7 | 383 | 21 | 4.3 |
| Early Mk V + AB873 | 371.5 | 405.3 | 407 | 33.8 | 1.7 |
| Late Mk V except AB873 | 356.3 | 395.8 | 407 | 39.5 | 11.2 |
| Mk V EN946 | 388 | 407 | 407 | 19 | 0 |
| Prototype Mk IX | 414 | 438 | 445 | 24 | 7 |
| Production Mk IX | 403.7 | 436.3 | 445 | 32.6 | 8.7 |
Spitfires listed as tested, prototype K9793, Mk I N3171, X4257, K9787, Mk V K9788, N3053, X4922, W3134, AA787, AA937, AB873, EF644, EN946 (original and RAE modified), Mk IX N3297, BF274, JL227, EN498
Various parts A&AEE report 692
RAE Technical Note Number Aero 1217 (Flight) June 1943, Improvement of performance of Spitfire EN946
RAE Technical Note Number Aero 1246 (Flight) July 1943, Comparison of three production Spitfires