1.   Introduction.

            Brief level speed measurements were carried out on the 2nd Spitfire F.21 PP.139 fitted with a Griffon 61 engine.

            These tests were not completed as the aircraft was required urgently by A. & A.E.E.

2.   Summary of Results

            At an all up weight of 9070 lb. and under engine conditions of 18 lb/sq.in. and 2750 r.p.m., the results are:-

(a)   Maximum level speed in F.S. gear, 460 m.p.h. at 25600 ft.
(b)   Maximum level speed in M.S. gear, 432 m.p.h. at 12200 ft.

3.   Condition of Aircraft

(a)   Griffon 61 engine (R.G.4.S.M.) No. 1280 fitted. This engine has a .45 airscrew reduction gear.
(b)   11 ft. 0 in. dia. 5 blade Jablo Rotol airscrew with faired roots, type R.14/5F5/2. Blades to Drg. No. RA.10129/JT.

(c)	Morris type QEV intercoolant radiator	Port duct
	Morris type QEZ radiator	Port duct
	Morris type QEY radiator	Starboard duct
	Morris type QEZ oil cooler	Starboard duct

(d)   Tropical type of air intake to Drg. No. 35638 Sht. 35 was fitted without a filter or by-pass shutter.
(e)   Multi-ejector exhausts fitted.
(f)   Windscreen with conical front panel.
(g)   T.R.1143 whip type aerial fitted.
(h)   Undercarriage leg fairings and wheel flaps fitted. Retractable tail wheel.
(i)   Four 20 m/m cannon armament.
(j)   All up weight 9070 lb. C.G. 3.06" inches aft of datum.

4.   Reduction of Results

            Results have been reduced to I.C.A.N. standard conditions in accordance with A.P. 970. Chap. 1000 para. 23.

5.   Engine Limitations

            Maximum for all out level: 5 minutes duration 18 lb/sq.in. boost at 2750 r.p.m.

6.   Results

            The level speed results are given on the attached curves.

            To facilitate drawing a reasonable curve and also for comparitive purposes, the curves for the 1st Prototype aircraft DP.851 have been added.

7.   Further Developments

            When the aircraft is returned from A. & A.E.E. the performance tests will be completed.