SUMMARY

                  Climb and level speed performance has been measured on Spitfire F. MK. IX B.F.274 both with and without a 30 gallon external jettisonable tank fitted. The climb performance at combat rating and position error have also been measured without the tank fitted. The engine was fitted with a 0.477:1 reduction gear and a Rotol R3/4F5/3 metal propeller.

                  A summary of the results follows:-

Without 30 gallon tank

Climb at normal rating:
Maximum rate of climb in M.S. supercharger 3200 ft.min at 13,500 ft.
Maximum rate of climb in F.S. supercharger 2540 ft/min. at 25,900 ft.
Service ceiling (100 ft/min) 42,100 ft.
Time to 10,000 ft. 3.1 mins.
Time to 20,000 ft. 6.5 mins.
Time to 30,000 ft. 10.7 mins.  
Time to 40,000 ft. 20.2 mins.  

Climb at Combat rating:
Maximum rate of climb in M.S. supercharger 3860 ft.min at 12,600 ft.
Maximum rate of climb in F.S. supercharger 3020 ft/min. at 25,200 ft.
Service ceiling (100 ft/min) 43,400 ft.
Time to 10,000 ft. 2.7 mins
Time to 20,000 ft. 5.6 mins.
Time to 30,000 ft. 9.2 mins.
Time to 40,000 ft. 16.6 mins.  

Level Speeds.
Maximum true air speed in M.S. supercharger 380 1/2 m.p.h. at 15,400 ft.
Maximum true air speed in F.S. supercharger 403 m.p.h. at 27,400 ft.

With 30 gallon tank
Climb at normal rating (but using 3000 r.p.m. above 30,000ft)
Maximum rate of climb in M.S. supercharger 3020 ft.min at 13,000 ft.
Maximum rate of climb in F.S. supercharger 2360 ft/min. at 25,900 ft.
Service ceiling (100 ft/min) using 3000 r.p.m. 42,400 ft.
Time to 10,000 ft. 3.3 mins.
Time to 20,000 ft. 7.0 mins.
Time to 30,000 ft. 11.5 mins.  
Time to 40,000 ft. 20.6 mins.  

Level Speeds.
Maximum true air speed in M.S. supercharger 366 m.p.h. at 15,400 ft.
Maximum true air speed in F.S. supercharger 389 m.p.h. at 27,400 ft.

1.    Introduction.

                  Performance tests were required on Spitfire F. MK.IX. B.F.274. This report deals with position error, climb, and level speed tests.

                  Preliminary results were forwarded to M.A.P. by letter, ref. A.A.E.E./4493/44/Gen-A.S. 56/50, dated 6th September 1942 and by postagram dated 17th September 1942.

2.    Condition of aircraft relevant to tests.

                  The aircraft was a standard Mk.IX fitted with a Merlin 61 engine having a 0.477:1 reduction gear. A production propeller type Rotol R3/4F5/3, having dural blades to Drg.No.RA.10061 was fitted.

                  Standard Mk.Vc (universal) wings were fitted. This wing has the large bulge in its top surface over the 20 m.m. guns. The two remaining 20 m.m. gun stubs in the leading edges were fitted with hemispherical blanks. The leading edge gun ports and the muzzles of the 20 m.m. guns were sealed. The ejection chutes beneath the wing relevant to the guns fitted were open.

                  A fuel cooler was fitted in the port wing root with an intake duct in the leading edge.

                  A rectangular rear view mirror without fairing was fitted above the windscreen. The bulletproof windscreen was fitted internally. The tail wheel was not retractable.

                  No snowgaurd was fitted over the air intake.

                  Individual ejector exhaust stubs were fitted.

                  One coolant radiator and the oil cooler were housed in a duct beneath the port wing and a second radiator and the intercooler coolant radiator in a similar duct beneath the starboard wing.

..................The aircraft was finished in normal fighter camouflage.

..................The 30 gallon external fuel tank fitted during some of the tests was of the type that can be fitted to the MK.V.

..................The take-off weights for these trials were:-

....................................7480 lb. without the 30 gallon tank.
....................................7775 lb. with the 30 gallon tank.

..................The following engine limitations were relevant to the tests made:-

R.P.M. Boost (lb/sq.in.)
Maximum for take-off. 3000 +12
Maximum for continuous climbing(60 min.limit) 2850 +12
Maximum all-out level flight and combat climbing (5 min. limit) 3000 +15

3.    Scope of Tests.

                  The following tests are dealt with in this report.

         (i)      The position error in level flight was measured between 320 m.p.h. and 130 m.p.h. A.S.I. by the 'aneroid' method.

         (ii)      Partial climbs were made using both normal and combat climb ratings to establish the best climbing speed.

        (iii)      Ceiling climbs were made using both normal and combat rating. Combat rating is normally permitted only for periods of 5 minutes, but a concession was allowed on this limitation for test purposes and the full climbs were made in this rating. The rate of climb was such that the boost fell from +15 to +12 lb/sq.in. due to altitude in less than 5 minutes in each supercharger gear.

                  Climbs were also made with a jettisonable 30 gallon fuel tank fitted externally beneath the fuselage. Prior to the introduction of combat rating, 3000 r.p.m. was permitted on the climb above 30,000 ft. and this procedure was used on the climb with the 30 gallon tank.

                  On all climbs the radiator flaps were fully open. The best climbing speed found from test (ii) was used.

        (iv)     Level speeds both with and without the 30 gallon tank were measured in M.S. and F.S. supercharger gears. The radiator flaps were closed for all level speed tests, giving the minimum drag position.

                  The tests were made between 15th August and 15th September 1942.

4.    Results.

                  The performance results are summarized on the first page of this report. Reductions of the results have been made by the method of A.& A.E.E. Memorandum dated 27.8.42.

                  The position error curve is given in Fig.3, the position of the pressure head in Fig.4, and the correction to altimeter when connected to the static of the A.S.I. system in Fig.5.

                  The best climbing speed found from partial climbs was 160 m.p.h. A.S.I. up to 25,000 ft. (approximately full throttle height in F.S. supercharger gear), decreasing 3 m.p.h. per 1000 ft. thereafter. This speed applied to climbs at both normal and combat ratings.

                  Details of the climb performance are given in Tables I, II and III and are plotted in Fig 1. During the climbs the automatic supercharger gear change device was over-ridden by a specially incorporated switch in order that the gear might be changed at the height for optimum climb.

                  Details of the maximum level speed performance are given in Tables IV and V and are plotted in Fig 2.

TABLE I
PERFORMANCE ON CLIMB
Without 30 gallon tankTake-off weight 7480 lb.
Normal ratingRadiator flap open.
Supercharger gear changed at 18,700 ft.
Standard
Height
(feet)
Time
from start
mins
Rate of
climb
ft/min
True air
speed m.p.h.
ASI
m.p.h.
P.E.C.Comp.R.P.M. Boost
lb/in2
S/c
gear
Sea level 0           
  2,000 0.6 3200 166.5 160 +2   -.1 2850 +12 M.S.
  5,000 1.6 3200 174.5 " +2   -.2 " +12 "
  6,500 2.0 3200 178    " +2   -.2 " +12 "
10,000 3.1 3200 188    " +2   -.5 " +12 "
  13,500* 4.2 3200 198.5 " +2   -.7 " +12 "
15,000 4.7 2960 203.5 " +2   -.7 " +10.7 "
16,500 5.2 2810 208    " +2   -.8 " +9.4 "
18,000 5.8 2630 213.5 " +2   -.8 " +8.1 "
20,000 6.5 2540 221    " +2   -1.1 " +12 F.S.
23,000 7.7 2540 231    " +2   -1.3 " +12 "
  25,900* 8.9 2540 238.5 157 +2.3-1.6 " +12 "
28,000 9.7 2240 240    151 +2.8-1.6 " +10 "
30,000 10.7   1950 240    145 +3.2-1.7 " +8.1 "
33,000 12.4   1520 239.5 136 +4.0-1.6 " +5.6 "
36,000 14.7   1090 238    127 +4.8-1.8 " +3.0 "
38,000 16.9    760 238.5 121 +5.3-2.0 " +1.4 "
40,000 20.2    440 239.5 115 +5.7-1.8 " -0.2 "
Service ceiling (100 ft/min.) 42,100Estimated absolute ceiling 42,800 ft.
Greatest height reached 41,000* Full throttle heights.

TABLE II
PERFORMANCE ON CLIMB
Without 30 gallon tankTake-off weight 7480 lb.
Combat ratingRadiator flap open.
Supercharger gear changed at 18500 ft.
Standard
Height
(feet)
Time
from start
mins
Rate of
climb
ft/min
True air
speed m.p.h.
ASI
m.p.h.
P.E.C.Comp.R.P.M. Boost
lb/in2
S/c
gear
Sea level 0         
  2,000 0.5 3690 166.5 160 +2   -.1 3000 +15.2 M.S.
  5,000 1.4 3740 174.5 " +2   -.2 " +15.2 "
  6,500 1.8 3760 178    " +2   -.2 " +15.2 "
10,000 2.7 3820 188    " +2   -.5 " +15.2 "
  12,600* 3.3 3860 196    " +2   -.6 " +15.2 "
15,000 4.0 3470 203.5 " +2   -.7 " +12.7 "
16,500 4.5 3230 208    " +2   -.8 " +11.3 "
18,000 5.0 2980 213.5 " +2   -.8 " +9.9 "
20,000 5.6 2930 221    " +2   -1.1 " +15.2 F.S.
23,000 6.6 2980 231    " +2   -1.3 " +15.2 "
  25,200* 7.4 3020 239    159 +2.1-1.6 " +15.2 "
28,000 8.4 2590 240    151 +2.8-1.6 " +11.7 "
30,000 9.2 2280 240    145 +3.2-1.7 " +9.5 "
33,000 10.7   1830 239.5 136 +4.0-1.6 " +6.7 "
36,000 12.6   1360 238    127 +4.8-1.8 " +4.0 "
38,000 14.3   1020 238.5 121 +5.3-2.0 " +2.4 "
40,000 16.6    680 239.5 115 +5.7-1.8 " +0.8 "
42,000 20.7    350 239.5 109 +6.2-1.8 " -0.8 "
Service ceiling (100 ft/min.) 43,400Estimated absolute ceiling 44,000 ft.
Greatest height reached 42,000* Full throttle heights.

TABLE III
PERFORMANCE ON CLIMB
With 30 gallon tankTake-off weight 7775 lb.
Normal rating-r.p.m. changed Radiator flap open.
to 3000 above 30,000 ftS/c gear changed at 18,800 ft.
Standard
Height
(feet)
Time
from start
mins
Rate of
climb
ft/min
True air
speed m.p.h.
ASI
m.p.h.
P.E.C.Comp.R.P.M. Boost
lb/in2
S/c
gear
Sea level 0         
  2,000 0.7 3020 166.5 160 +2   -.1 2850 +12 M.S.
  5,000 1.7 3020 174.5 " +2   -.2 " +12 "
  6,500 2.2 3020 178    " +2   -.2 " +12 "
10,000 3.3 3020 188    " +2   -.5 " +12 "
  13,500* 4.5 3020 198.5 " +2   -.7 " +12 "
15,000 5.0 2820 203.5 " +2   -.7 " +10.7 "
16,500 5.5 2640 208    " +2   -.8 " +9.4 "
18,000 6.1 2450 213.5 " +2   -1.1 " +8.1 "
20,000 7.0 2360 221    " +2   -1.3 " +12 F.S.
23,000 8.2 2360 231    " +2   -1.3 " +12 "
  25,900* 9.5 2360 238.5 157 +2.3-1.6 " +12 "
28,000 10.4   2059 240    151 +2.8-1.7 " +10 "
30,000 11.5   1780/2000 240    145 +3.2-1.6 2850/3000 +8.1/+9.5 "
33,000 13.2   1570 239.5 136 +4.0-1.8 3000 +5.6 "
36,000 15.4   1140 238    127 +4.8-1.8 " +3.0 "
38,000 17.4    810 238.5 121 +5.3-2.0 " +1.4 "
40,000 20.6    480 239.5 115 +5.7-1.8 " -0.2 "
Service ceiling (100 ft/min.) at 3000 r.p.m. 42,400Estimated absolute ceiling at 3000 r.p.m. 43,000 ft.
Greatest height reached 41,000* Full throttle heights.

TABLE IV
LEVEL SPEEDS
Without 30 gallon tankTake-off weight 7480 lb.
Combat ratingRadiator flap closed.
Standard
Height
(feet)
TAS
mph
ASI
m.p.h.
P.E.C.Comp.RPM Boost
lb/in2
S/c
gear
  6000 338     317    -6.2 -1.4 3000 15.2 M.S.
  8000 347 315 -6.1 -1.9 " 15.2 "
10000 356 314 -6.1 -2.4 " 15.2 "
13000 370     312     -6.0 -3.3 " 15.2 "
  15400* 380 309 -5.9 -4.0 " 15.8 "
16500 380 304     -5.7 -4.2 " 14.0 "
18000 380 297     -5.5 -4.6 " 12.4 "
20000 380     287 -5.2 -4.8 " 10.4 "
23000 377 271 -4.3 -5.2 " 7.8 "
20000 368     277 -4.7 -4.4 2980 15.2 F.S.
23000 382     274     -4.6 -5.2 " 15.2 "
25000 391 272 -4.5 -6.0 " 15.2 "
  27400* 403     270     -4.4 -6.7 " 15.2 "
30000 402     257     -3.6 -6.8 " 12.2 "
33000 398     239 -2.7 -6.9 " 9.0 "
36000 386     218 -1.5 -6.4 " 5.9 "
* Full throttle height

TABLE V
LEVEL SPEEDS
With 30 gallon tankTake-off weight 7775 lb.
Combat ratingRadiator flap closed.
Standard
Height
(feet)
TAS
mph
ASI
m.p.h.
P.E.C.Comp.RPM Boost
lb/in2
S/c
gear
  6,000 328     307    -5.8 -1.3 3000 15.2 M.S.
  8,000 336 306     -5.8 -1.8 " 15.2 "
10,000 345     304     -5.7 -2.2 " 15.2 "
13,000 357     301     -5.6 -3.1 " 15.2 "
  15,400* 366     297 -5.5 -3.7 " 15.8 "
16,500 366     292 -5.3 -3.9 " 14.0 "
18,000 366     285     -5.0 -4.1 " 12.4 "
20,000 365     275 -4.5 -4.3 " 10.4 "
23,000 363     260     -3.8 -4.6 " 7.8 "
20,000 358     270     -4.3 -4.1 2980 15.2 F.S.
23,000 370     266     -4.1 -4.9 " 15.2 "
25,000 378     265     -4.1 -5.6 " 15.2 "
  27,400* 389     260 -3.9 -6.2 " 15.2 "
30,000 384 244     -2.9 -6.1 " 12.2 "
33,000 374 224 -1.8 -5.9 " 9.0 "
35,000 363     208 -1.0 -5.55 " 5.9 "
* Full throttle height

Spitfire IX BF274, Performance on Climb
Spitfire IX BF274, Speed and Boost at Height

WWII Aircraft Performance     Spitfire Mk IX Performance