Aeroplane and Armament Experimental Establishment
Boscombe Down
Spitfire Mk. VA X.4922
(Merlin XLV)
Brief Performance Trials
SUMMARY
Results of tests.
(a) The top speed of the aeroplane is 375 m.p.h. at 20,800 feet.
(b) The maximum rate of climb is 3,140 feet per minute at 14,400 feet. The time to 20,000 feet is 7.1 minutes and the Service ceiling is 37,700 feet.
(c) The radiator is not quite suitable for English summer conditions on the climb.
(d) The oil cooler is suitable for English summer conditions on the climb.
(e) The take-off run in zero wind and standard conditions is 330 yards, and the distance to clear a 50 foot screen is 530 yards.
(f) The airscrew setting of 34 deg. to 54 deg. is suitable for the aeroplane under all conditions of flight.
Aeroplane and Armament Experimental Establishment
Boscombe Down
Spitfire Mk. VB W.3134
(Merlin 45)
Brief Performance Trials
SUMMARY
Brief performance trials were required of a Spitfire Mk VB fully operationally equipped for comparison with two other aircraft of the type not operationally equipped and previously tested at this establishment.
| Height feet |
Top Speed M.P.H. |
Time to Climb mins. | Rate of Climb Ft/min. |
|---|---|---|---|
| S.L. | — | 0 | — |
| 2,000 | — | 0.6 | 3240 |
| 5,000 | — | 1.5 | 3240 |
| 10,000 | 331 | 3.1 | 3250 |
| 15,000 | 351 | 4.6 | 3250 |
| 20,000 | 371 | 6.4 | 2440 |
| 25,000 | 359 | — | — |
| 30,000 | — | 12.2 | 1170 |
Aeroplane and Armament Experimental Establishment
Boscombe Down
8 March 1942
Spitfire Mk. Vc AA.873
(Merlin 45)
Brief Performance and Handling Trials with
4 - 20 m/m guns fitted
SUMMARY
Results of tests.
(i) The maximum rate of climb is 2,900 feet/minute at 13,400 feet. The time to 20,000 feet is 7.4 minutes, and the estimated service ceiling is 36,400 feet.
(ii) The top speed is 374 m.p.h. at 19,000 feet.
(iii) There is no noticeable difference between the handling characteristics of this aeroplane and other Spitfire V types.
Aeroplane and Armament Experimental Establishment
Boscombe Down
15 April 1942
Spitfire Mk. VB (Tropical) AB.320
(Merlin 45)
Position error, and performance with and without
a 90 gallon external overload tank
SUMMARY
This report deals with performance trials on a fully tropicalised Spitfire V.b. with a Merlin 45 engine, with and without a 90 gallon external fuel tank. The performance results were as follows:-
| Without tank | With tank | |
|---|---|---|
| Weight | 6695 lb | 7485 lb |
| Maximum rate of climb | 2660 ft/min. | 2145 ft/min. |
| at full throttle height of | 14,000 ft. | 14,000 ft. |
| Service ceiling | 36,300 | 34,500 ft. |
| Time to 20,000 feet | 8.0 mins. | 10.0 mins. |
| Maximum speed | 354 m.p.h. | 337½ m.p.h. |
| at full throttle height of | 17,400 ft. | 17,400 ft. |
Aeroplane and Armament Experimental Establishment
Boscombe Down
25 November 1942
Spitfire Mk. VC AA.878
(Merlin 45)
Climb, speed, and cooling tests at combat rating
SUMMARY
The operational limitations of the Merlin 45 have been increased, the use of 3000 R.P.M. and +16 lb/sq.in. boost being now permitted for periods not exceeding 3 minutes during combat. Tests have been made to determine the performance of the aeroplane at this new rating, and also whether the oil and radiator cooling are adequate.
| Climb performance | Combat rating | Normal rating |
|---|---|---|
| Maximum rate of climb (ft/min) | 3710 at 8,800 ft. | 2650 at 14,900 ft. |
| Time to 10,000 ft. (minutes) | 2.7 | 3.8 |
| Time to 20,000 ft. (minutes) | 6.15 | 7.9 |
| Level Speed | ||
| Maximum level true airspeed (m.p.h.) | 369 at 13,000 ft. | 359 at 19,900 ft. |
Level speed.
The results show that the rate of climb is increased by about 1,100 ft/min. below 8,800 ft. by the use of combat rating. Above this height the increase is less, falling to 300 ft/min. at 15,000 ft.
In level flight the maximum level true airspeed is higher by about 35 m.p.h. below 13,000 ft.; above this height the increase in speed is less and falls to zero at 19,900 ft., the full throttle height at normal rating.
Aeroplane and Armament Experimental Establishment
Boscombe Down
2 January 1943
Spitfire (F) Mk. VB W.3322
(Merlin 46)
Performance trials with Rolls-Royce S.U.
fuel injection pump
SUMMARY
A Rolls-Royce S.U. fuel pump has been fitted to Spitfire (F) Mk.VB, W.3322 in place of the normal A.V.T.40 float type carburettor and the performance of the aircraft has been measured as part of a general schedule of tests including fuel consumption, carburation and behaviour under negative "g".
The principle results at a weight of 6,516 lb. are:-
| Climb | Maximum rate of climb (2850 r.p.m.) | 2,740 ft/min. |
|---|---|---|
| Service ceiling (100 ft/min) | 39,400 ft. | |
| Time to 39,000 ft. | 27¾ min. | |
| Level Speed | Maximum speed - 368 m.p.h. at 22,500 ft. |
The aircraft is appreciably better than most other Spitfires, after allowing for differences in weight and wing span, the gain being about 1,500 ft. in ceiling and 8-10 m.p.h. in top speed. Both of these improvements may be attributed to the removal of the carburettor, causing a lower pressure drop of the engine air before entering the supercharger, and thus giving an appreciable rise in boost pressure.
Aeroplane and Armament Experimental Establishment
Boscombe Down
25 May 1943
Spitfire F. Mk.VB W.3228
(Merlin 50 M)
Climb and level speed performance when fitted with a
Merlin 50 engine with a cropped supercharger impeller
SUMMARY
Spitfire F. Mk.VB W.3228 has been fitted with a special Merlin 50 engine, on which the supercharger impellor was "cropped" to a diameter of 9.5". On this engine the maximum permitted boost at combat rating was +18 lb/sq.in. instead of +16 lb/sq.in. as on a normal Merlin 50 engine. Climb and level speed measurements have been made at this combat rating and form the subject of this report.
| CLIMB | |
|---|---|
| Maximum rate of climb | 4270 ft/min. at 3850 ft. |
| Maximum rate of climb at 10,000 ft. | 3800 ft/min. |
| Maximum rate of climb at 20,000 ft. | 2320 ft/min. |
| Service ceiling | 35,700 ft. |
| Estimated absolute ceiling | 36,400 ft. |
| Level Speed | |
| Max. level true airspeed at 2,000 ft. | 334 mph. |
| Max level true airspeed at 5,900 ft. (FTH) | 350 mph. |
| Max level true airspeed 10,000 ft. | 347 mph. |
| Max level true airspeed 20,000 ft. | 336 mph. |
