Seafire III LR.765 was the first production Mk.III, made by Messrs. Westland Aircraft Ltd., and was sent to this Establishment for brief check handling and performance trials. This part of the Report deals with the climb and level speed performance.
Results of similar tests made on Seafire II Mk.970 have been reported in the 2nd Part of Report No. A.& A.E.E./785,a.
2. Condition of aircraft relevant to tests.
2.1. General. The cheif features of the aircraft were:-
|A Merlin 50 engine|
|A 4-blade Rotol 10'9" diameter propeller, type R12/4F5/4.|
|Triple ejector exhaust stubs with fishtails and heater stubs.|
|Temperate air intake with snow guard.|
|Radiator below starboard wing, oil cooler below port wing.|
|W/T mast with aerial.|
|Internal bullet proof windscreen.|
|'Balloon ' type hood.|
|Circular rear view mirror with fairing above windscreen.|
|Deck landing arrestor hook below fuselage.|
|Catapult spools beneath centre-section and on fuselage side.|
|Slinging points on fuselage side aft of engine cowling.|
|Mk. VC universal type folding wings with folding tips.|
|2 x 20 mm. guns, 4 x 0.303" guns fitted. Muzzles, leading edge ports, and ejection chutes sealed.|
|Hemispherical blanks over unused 20 mm. gun stubs.|
|Attachment lugs for auxiliary fuel tank beneath centre-section.|
|Mk.VIII pressure head below port wing.|
|The aircraft was finished in normal Naval camouflage.|
2.2. Engine numbers and limitations. The aircraft was fitted with a Merlin 50 engine Nos. 1155319/375640. The engine limitations applicable to the tests were:-
|Maximum for combat (5 minute limit)||3000||+16|
|Maximum for climbing(1 hour limit)||2850||+9|
2.3. Loading. The aircraft was flown throughout the tests at a take-off weight of 7100 lb., with the centre of gravity position 8" aft of the datum (undercarriage down).
3. Scope of tests.
Climbs were made at normal rating to 34,000 ft. with the radiator exit duct in the fully open position, using a climbing speed of 150 mph ASI up to 16,000 ft., and decreasing by 2 mph per 1000 ft. thereafter. These climbing speeds were those determined for Seafire II MA.970, reported on in the 2nd Part of Report No. A.& A.E.E./785,a.
Maximum level speeds were measured at heights up to 26,000 ft. with the radiator exit duct flap in the minimum drag position.
4. Results of tests.
The results of the climb and level speed performance tests have been corrected to standard atmospheric conditions by the methods given in Report No. A.& A.E.E./Res/170, and the results of the level speeds have been corrected to 95% of the take-off weight, viz. 6,750 lb. by the method given in the same Report. A "strut correction" based on ARC.6420 has also been applied and the compressibility correction has been calculated by the methods given in the Addendum to Report No. AAEE/Res/147. The position error has been taken from the 38th Part of Report No. A.& A.E.E./692,i. on Spitfire VC AA.878, which had similar pressure head installation.
The results of the climb performance tests are given in Table I and Fig.1, and those of the level speed performance tests in Table II and Fig.2. A brief summary of the results is given below.
(i) Climb Performance
|Max. rate of climb at sea level||2500 ft/min.|
|Max. rate of climb at 14,200 ft.||(F.T.H.)||2600 ft/min.|
|Max. rate of climb at 20,000 ft.||1920 ft/min.|
|Max. rate of climb at 30,000 ft.||745 ft/min.|
|Service Ceiling||35,600 ft.|
|Estimated absolute ceiling||36,200 ft.|
(ii) Level peed performance.
|Maximum true airspeed at 4,000 ft.||321 mph|
|Maximum true airspeed at 10,500 ft.||(F.T.H.)||351 mph|
|Maximum true airspeed at 24,000 ft.||328 mph|
Tests similar to these were made previously on Seafire II MA.970 and reported in the 2nd Part of Report No. AAEE/785,a. Brief tests subsequently made on the same aircraft after it had been converted to a Mk.III by fitting folding wings showed tthe speed performance to be unchanged. No strict comparison between the results of these tests and those obtained on MA.970 is , however, possible, as MA.970 was fitted with a Merlin 46 engine. The two engines are, however, similar in power out-put under comparable conditions, and the performance of LR.765, the aircraft now tested, is slightly better that that of MA.970. It is therefore concluded that the performance of this first production aircraft is satisfactory.
|Time to |
|Service ceiling 35,600 ft.
Estimated absolute ceiling 36,200