Spitfire Mk XIV Performance Testing

Vickers Armstrong Ltd.
Supermarine Works

10 September 1943

Spitfire VIII Conversion JF.319
Level Speed Tests With Griffon R.G.5.S.M. Engine
18 lb/sq. in. Boost Rating

Summary of Results

            At the all up weight for the Spitfire XIV i.e. 8400 lb. and at 18 lb/sq.in. and 2750 r.p.m., the results are:-

(a)   Maximum level speed in F.S. gear, 447 m.p.h. at 25600 ft.
(b)   Maximum level speed in M.S. gear, 389 m.p.h. at 6000 ft.

Level Speeds and Boost

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Aeroplane and Armament Experimental Establishment
Boscombe Down

27 October 1943

Spitfire F. Mk. VIII(Conv) (Prototype Mk.XIV) JF.319
(Griffon RG5SM)

Climb and level speed performance and position error

           (i) On the climb at combat rating.

Max. rate of climb in MS supercharger gear5,040 ft/min. at 2,100 ft.
Max. rate of climb in FS supercharger gear3,550 ft/min. at 22,100 ft.

           (ii) In all-out level flight.

Max. true air speed in MS supercharger gear391 mph at 5,500 ft.
Max. true air speed in FS supercharger gear446 mph at 25,900 ft.

Performance on Climb at Combat Rating
Level Speed Performance

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Rolls Royce Ltd.
June 1944

Spitfire XIV low altitude speed at +21 lbs./sq.in.

20 July 1944

Speeds of F.Mk. XIV (Griffon 65)

August 1944

Spitfire XIV RB.176
(Griffon 65)

Top level speed at +25 lbs/sq.in. Boost


(A.F.D.S. REPORT No. 176)
July 1946

Spitfire XIV
(Griffon 65)

Climb and Level Speed Performance (+18 Boost)

Maximum Climbing Performance
Level Speed Performance


Comments from No. 610 Squadron ORB relating to performance of Spitfire XIV

Griffon HP Chart
The Roll-Royce Griffon
Roll-Royce Griffon 65

Climb and Speed at +18 lbs Boost Supermarine, October 1944. There was much discussion during the summer and fall of 1944 between the Air Ministry, Supermarine and Rolls-Royce as to whether, for production reasons, the Spitfire XIV should switch to a .45 reduction gear to match that of the Spitfire 21 or retain the .51 gear. It was decided that the advantages of the .51 were such that it would be retained for the Spitfire XIV.

Spitfire XIV Aircraft Data Sheet
Spitfire XIV A.F.D.S. Level Speed Check Runs

Technical Note No.Aero.1501(Flight) Improvement of Performance of Fighter Aircraft Operating Against the German Flying Bomb

610 Squadron Operations Record Book, July 1944 - "21 lbs boost on 150 octane petrol"

610 Squadron Operations Record Book, 6 September 1944: First operation over Germany by Spitfire XIV Wing comprised of 350, 402 and 610 squadrons.

Use of Grade 150 Fuel by the Second Tactical Air Force, 20 November, 1944.

402 Squadron Operations Record Book, 26 February 1945 - "150 grade fuel"

Memo regarding replacement aircraft for 125 Wing showing +21 lbs boost employed by the Spitfire XIVs of 2nd TAF.

Spitfire Mk XIV versus Me 109 G/K: A Performance Comparison

[WWII Aircraft Performance] [Spitfire Performance Testing]
[Weights and Loading Data] [Handling Trials] [AFDU Tactical Trials] [Tactical Comparison with Me.109G-6]