Summary

.......Climb and level speed performance and position error tests have been carried out on Spitfire XII D.P.845. The results obtained are summarised as follows:

Climb at normal rating.

Max. rate of climb in M.S. supercharger gear3040 ft/min. at   4,000 ft.
Max. rate of climb in F.S. supercharger gear2240 ft/min. at 16,700 ft.
Service ceiling (100 ft/min)38,200 ft.
Time to 10,000 ft.  3.55
Time to 20,000 ft.  8.15
Time to 30,000 ft.15.5
Time to 38,000 ft.35.9

Climb at combat rating.

Max. rate of climb in M.S. supercharger gear3760 ft/min. at   2,600 ft.
Max. rate of climb in F.S. supercharger gear2760 ft/min. at 15,300 ft.
Service ceiling (100 ft/min)39,000 ft.
Time to 10,000 ft.  2.95
Time to 20,000 ft.  6.7
Time to 30,000 ft.12.95
Time to 39,000 ft.35.0

Level speeds.

Max. level speed in M.S. supercharger gear372 m.p.h. at   5,700 ft.
Max. level speed in F.S. supercharger gear397 m.p.h. at 17,800 ft.

1.    Introduction.

.......Performance trials were required on the prototype Spitfire XII D.P.845. This part of the report contains the results of climb and level speed performance and the position error correction curve.

.......Preliminary information regarding the level speed performance was given in a letter to M.A.P. dated 6th September, 1942, AAEE/4493/44.Gen-A.S.56/50. These had been provisionally reduced using the position error correction for the Spitfire F. Mark IX and consequently differed slightly from the results now given.

2.    Condition of the Aircraft relevant to tests.

.......2.1 General.    This aircraft was fitted with a Griffon IIB engine (0.45:1 reduction gear) and a Rotol experimental four-blade propeller. The original engine No.A-255211 developed a cracked sump during the trials and was replaced by engine No.A-166452. The final results given here are the performance of the aeroplane with the latter engine.

.......Universal wings were fitted, differing slightly from the standard Mk.Vc universal wings in that there was only a small bulge on the top surface over the inboard 20 mm. guns; on the standard wing there was a large bulge. The armament consisted of 2 x 20 mm. guns and 4 x .303 in. guns, the unused 20 mm. gun stubs being fitted with 'streamlined' blanks. The leading edge gun ports and the muzzles of the 20 mm. guns were sealed. The ejector chutes for the .303 in. guns were sealed but the 20 mm. gun ejector chutes were open.

.......The engine cowling differed from the Mk. V Spitfire, since it had been modified to accommodate the Griffon IIB engine giving the nose of the aeroplane a square appearance. The engine exhausts consisted of individual ejector stubs.

.......A normal air intake was fitted without the ice-guard.

.......The radiator and oil cooler were the standard Spitfire V tropical types.

.......A wireless mast was provided behind the cabin but neither R/T aerial nor I.F.F. aerials were fitted.

.......The rear view mirror above the windscreen was circular with a hemispherical fairing on the forward side. The standard Spitfire V mirror is rectangular without a fairing.

.......An internal bullet-proof windscreen was provided.

.......The rudder was of greater area and aspect ratio, as may be seen from the accompanying photographs.

.......Special attention has been given to the finish of this aircraft, the external surfaces being flush rivetted throughout. The standard Spitfire V is flush rivitted on the wings and the forward part of the fuselage only. Filling has been applied at joints and edges of overlapping panels. The whole surface of the aeroplane, including the fabric work, has been polished to give a smooth finish. We were given to understand by Messrs. Vickers (Supermarine) that this finish was now standardised for all Spitfires.

.......The position and setting of the pressure head is shown in Fig.1. This is similar to that of a standard Spitfire V.

.......2.2 Propeller particulars.    The leading particulars of the propeller are:-

Rotol experimentalMark XH.54D-RM-55
Diameter10 ft. 5 in.
No. of blades4 (Dural)
Direction of rotationR.H.
Hub serial No.E.H.202
Blade No. 1 Serial No.E.D.415
Blade No. 2 Serial No.E.D.416
Blade No. 3 Serial No.E.D.417
Blade No. 4 Serial No.E.D.418
Pitch range35 deg.
Fine pitch setting40 deg.-0'

.......2.3 Engine limitations.    The limitations of the Griffon IIB engine, obtaining at the time of the test were:-

R.P.M. Boost (lb.sq.in)
Max. for take-off2750+12
Max. for continuous climbing (60 min. limit)2600+  9
Max. for all-out level flight and combat climbing (5 min. limit)2750+12

.......2.4 Loading.    The take-off weight for these trials was 7415 lb., with the centre of gravity 4.9 in. aft of the datum (undercarriage down).

3.    Scope of tests.

.......The following tests were made:

(i)Position error measurements by the aneroid method, in level flight with flaps and undercarriage up.
(ii)Partial climbs at mean heights of 6,000 ft and 17,500 ft. in M.S. supercharger gear and at 18,000 ft. and 29,500 ft. in F.S. supercharger gear to determine the best climbing speed.
(iii)Three climbs at normal rating with the radiator shutter fully open and using the best climbing speeds from test (ii).
(iv)Three climbs at combat rating, one in M.S. supercharger gear, one in F.S. supercharger gear and a final one combining both. The radiator shutter was fully open on all climbing tests and the best climbing speeds from test (ii) were used.

.......(Combat rating is normally permitted for periods of 5 minutes only, but for test purposes the full climbs were all-out at this rating).
.......
(v)Level speeds at heights between ground level and 14,000 ft. in M.S. supercharger gear, and between 10,000 and 25,000 feet. in F.S. supercharger gear with the radiator in the minimum drag position.

4.    Results of tests.

.......The method of reduction given in A.& A.E.E. Memorandum dated 27th August, 1942 was used in reducing the climb and speed results to standard atmospheric conditions.

(i)The position error correction varies almost linearly with speed, i.e. from +5.7 m.p.h. at 120 m.p.h. A.S.I. to -10 m.p.h. at 360 m.p.h. A.S.I. Full details are given in Fig.2. The altimeter corrections when connected to the static side of the airspeed system are given in Fig.3
(ii)The best climbing speed found from the partial climbs was 190 m.p.h. A.S.I. up to 16,000 ft. (approximately full throttle height in F.S. supercharger gear), then decreasing by 3 1/2 m.p.h. per 1000 ft.
(iii)Full results of the climb at combat rating are given in Table I and Fig.4. briefly they are:

Max. rate of climb in M.S. supercharger gear3760 ft/min.@   2,600 ft.
Max. rate of climb in F.S. supercharger gear2760 ft/min.@ 15,300 ft.
Service ceiling 39,000 ft.; estimated absolute ceiling 40,000 ft.

(iv)Full results of the climb at normal rating are given in Table II and Fig.4. Briefly, they are:-

Max. rate of climb in M.S. supercharger gear3040 ft/min.@   4,000 ft.
Max. rate of climb in F.S. supercharger gear2240 ft/min.@ 16,700 ft.
Service ceiling 38,200 ft.; estimated absolute ceiling 39,000 ft.

(v)The level speeds are given fully in Table III and Fig.5. The maximum true airspeeds are:-

In M.S. supercharger gear372 m.p.h. at 5,700 ft.
In F.S. supercharger gear397 m.p.h. at 17,800 ft.

TABLE I
Performance on climb (combat rating)
Take-off weight - 7415 lb........Supercharger gear changed at 11,200 ft.
Height
(feet)		Time from
start
mins.		Rate of
climb
ft/min.		T.A.S.
m.p.h.		A.S.I.
m.p.h. 		P.E.C.
m.p.h.		Comp.
corr.
m.p.h.		Boost
lb/sq.in.		R.P.M.MixtureRadiator
shutter
00---------
  2,000    .553760196.5190+0.8-0.112.0  2740RichFully open
*2,600  .73760198   ""-0.112.0  ""
  4,000  1.053600202   ""-0.210.8  """
  6,000  1.653370208   ""-0.49.2"""
  8,000  2.253130215   ""-0.57.8"""
10,000  2.952900221.5""-0.76.4"""
12,000  3.652760228.5""-0.812.0  """
14,000  4.352760236   ""-1.012.0  """
15,300  4.852760240   ""-1.212.0  """
16,0005.12680243   ""-1.211.2  """
18,000  5.852460242.5183+1.2-1.39.4"""
20,0006.72230242.5177+1.6-1.47.82700""
22,000  7.652000242   170+2.0-1.56.1"""
24,000  8.751780240.5163+2.4-1.54.6"""
26,0009.91560239.5156+3.0-1.63.1"""
28,00011.3  1340238   148+3.5-1.61.7"""
30,00012.951110235   141+4.1-1.60.3"""
32,00014.95  890234   135+4.5-1.6-1.1"""
34,00017.55  660230   127+5.1-1.6-2.4"""
35,00019.2    550230   124+5.4-1.6-3.1"""
36,00021.2    440229   121+5.6-1.6-3.7"""
37,00023.8    320227.5117+5.9-1.6-4.2"""
* Full throttle heightService ceiling 39,000 ft.
Estimated absolute ceiling40,000

TABLE II
Performance on climb (normal rating)
Take-off weight - 7415 lb........Supercharger gear changed at 10,800 ft.
Height
(feet)		Time from
start
mins.		Rate of
climb
ft/min.		T.A.S.
m.p.h.		A.S.I.
m.p.h. 		P.E.C.
m.p.h.		Comp.
corr.
m.p.h.		Boost
lb/sq.in.		R.P.M.MixtureRadiator
shutter
00---------
  2,000    .653040196.5190+0.8-0.19.02605RichFully open
*4,0001.33040202   ""-0.29.0""
  6,0002.02800208   ""-0.47.6"""
  8,000  2.752570215   ""-0.56.1"""
10,000  3.552340221.5""-0.74.6"""
12,000  4.452240228.5""-0.89.0"""
14,000  5.352240236   ""-1.09.0"""
16,000  6.252240243   ""-1.29.0"""
*16,700    6.552240243.5188+0.9-1.39.0"""
18,000  7.152110242.5183+1.2-1.37.9"""
20,000  8.151920242.5177+1.6-1.46.3"""
22,000  9.251720242   170+2.0-1.54.8"""
24,00010.5  1520240.5163+2.4-1.53.3"""
26,00011.9  1320239.5156+3.0-1.61.9"""
28,00013.551120238   149+3.5-1.60.6"""
30,00015.5    920235   141+4.1-1.6-0.8  """
31,00016.65  820234.5138+4.3-1.6-1.5  """
32,00017.95  720234   135+4.5-1.6-2.1  """
33,00019.45  620232   131+4.8-1.6-2.8  """
34,00021.2    520230   127+5.1-1.6-3.4  """
35,00023.35  420230   124+5.4-1.6-4.0  """
* Full throttle heightService ceiling38,200 ft.
Estimated absolute ceiling39,200

TABLE III
Level speed performance
Take-off weight - 7415 lb.
Height
(feet)		T.A.S.
m.p.h.		A.S.I.
m.p.h. 		P.E.C.
m.p.h.		Comp.
corr.
m.p.h.		Boost
lb/sq.in.		R.P.M.MixtureSupercharger
gear		Radiator
shutter
0346   355   -9.7012.0  2750RichM.S.Min. drag
position
  2,000355   355   -9.7-0.612.0  """
  4,000364.5354   -9.6-1.112.0  """"
*5,700372   353   -9.6-1.812.0  """"
  8,000372   340.5-8.7-2.310.1  """"
10,000370.5329   -7.9-2.78.6""""
12,000368   316.5-7.2-3.07.1""""
14,000364   303   -6.3-3.35.7""""
10,000361   320   -7.3-2.512.0  ""F.S."
12,000370   318.5-7.2-3.112.0  """"
14,000379.5317   -7.1-3.812.0  """"
16,000388.5314.5-6.9-4.412.0  """"
*17,800  397  312.5-6.8-4.912.0  """"
20,000397   301.5-6.2-5.510.0  """"
22,000396   291   -5.4-5.88.3""""
24,000392   278   -4.7-5.86.6""""
* Full throttle height

[Performance on Climb] [Level Speeds and Boost at Heights]

[WWII Aircraft Performance] [Spitfire Mk XII Performance] [Spitfire Mk XII Tactical Trials]