Introduction
These trials have been made during the period August 18th to December 12th 1938. Speed trials were made with Spitfire K.9788 to determine whether there was any reduction of speed due to fitting flash eliminators on the guns. No difference in speed could be measured when the guns were fitted with the flash eliminators, four of which protruded in front of the leading edge, or muzzle caps all of which were inside the wing. The speeds measured during these trials confirmed exactly the speeds given in this report. All speed trials were made with the gun channels open and guns in position.
Results of Trials
A comparison is made in the table below between this production aeroplane and the prototype K.5054.
| Prototype K.5054 | Production K.9787 | |
|---|---|---|
| Maximum speed | 349 at 16800 | 362 at 18,500 ft. |
| Maximum cruising speed (at 15,000 ft.) | 311 m.p.h. | 318 m.p.h. |
| Time to 15,000 ft. | 5.7 mins. | 6.5 mins. |
| Time to 30,000 ft. | 17.0 mins | 22.4 mins |
| Service ceiling | 35,400 ft. | 31,900 ft. |
| Weight | 5332 lb. | 5819 lb. |
Night Flying
It is considered that the exhaust manifolds tested are unsuitable.
SUMMARY OF TRIALS
| AEROPLANE | Spitfire | No. K.9787 |
| SPEC. NO. | 16/36 | |
| CONTRACTOR | Supermarine Aviation Works (Vickers) Ltd. |
| TYPE | Landplane | DUTY | Fighter. |
| ENGINES. | Merlin II | Normal B.H.P | 966 at Rated Altitude 12,250 ft |
| At 2,600 R.P.M. | |||
| lb. | |
| Tare weight | 4482 |
| Weight light | 4246 |
| Fixed military load | 236 |
| Service Load | 658 |
| Fuel 84 gallons* | 630 |
| Oil 5½ | 49 |
| Flying weight on trials. | 5819 |
| * Based on 7.5 lb. per gallon. | |
| At Full Throttle | |||
| Height Feet | Top Speed M.P.H. | Time To Climb Mins. | Rate of Climb Ft./Min. |
|---|---|---|---|
| S.L. | 2090 | ||
| 2,000 | 295 | 1.0 | 2195 |
| 5,000 | 307 | 2.3 | 2295 |
| 10,000 | 328 | 4.3 | 2490 |
| 15,000 | 348 | 6.5 | 2062 |
| 20,000 | 360 | 9.4 | 1480 |
| 25,000 | 349 | 13.6 | 900 |
| 30,000 | 315 | 22.4 | 325 |
| Service Ceiling | 31,900 ft. | Landing speed | M.P.H./Kts. |
| Take off run | 420 yds. Time secs. | Distance from rest to clear 50 ft. screen | 720 yards |
| Stalling speed | M.P.H./Kts. | Gliding in A.S.I. | 80 M.P.H./Kts. |
| Best landing A.S.I. | 60 M.P.H./Kts. | ||
| Landing and take off tests corrected to zero wind. | |||
CLIMBING TRIALS
| Height in Standard Atmosphere Feet | Time From Start Min. | Rate of Climb Ft./Min. | True Air Speed M.P.H. | A.S.I. M.P.H. | P.E.C. | Comp. | R.P.M. | Boost lb.sq.in. |
|---|---|---|---|---|---|---|---|---|
| Sea Level | 0 | 2090 | 171.5 | 174.5 | -2.8 | 2095 | +6.4 | |
| 1,000 | 0.5 | 2130 | 174 | 174.5 | -2.8 | - | 2130 | +6.4 |
| 2,000 | 1.0 | 2195 | 176.5 | 174.5 | -2.8 | -0.1 | 2165 | +6.4 |
| 3,000 | 1.4 | 2215 | 179.5 | 174.5 | -2.8 | -0.1 | 2200 | +6.4 |
| 5,000 | 2.3 | 2295 | 185 | 174.5 | -2.8 | -0.2 | 2270 | +6.4 |
| 6,500 | 3.0 | 2355 | 189 | 174.5 | -2.8 | -0.3 | 2320 | +6.4 |
| 10,000 | 4.3 | 2490 | 199.5 | 174.5 | -2.8 | -0.6 | 2440 | +6.4 |
| 13,000 | 5.5 | 2300 | 207 | 172.5 | -2.5 | -0.7 | 2475 | +4.45 |
| 15,000 | 6.5 | 2065 | 208.5 | 168.0 | -1.8 | -0.8 | 2465 | +2.8 |
| 16,500 | 7.2 | 1890 | 210 | 164.5 | -1.3 | -0.8 | 2460 | +1.75 |
| 18,000 | 8.1 | 1710 | 211.5 | 161.0 | -0.7 | -0.9 | 2455 | +0.8 |
| 20,000 | 9.4 | 1480 | 213.5 | 157.0 | 0 | -1.0 | 2440 | -0.4 |
| 23,000 | 11.7 | 1135 | 216.5 | 150.0 | +1.1 | -1.1 | 2420 | -2.0 |
| 26,000 | 14.8 | 790 | 220 | 143.5 | +2.3 | -1.1 | 2390 | -3.4 |
| 28,000 | 17.8 | 555 | 222 | 139.0 | +3.1 | -1.2 | 2365 | - |
| 30,000 | 22.4 | 325 | 225 | 135.0 | +3.9 | -1.2 | 2345 | - |
| 32,000 | 32.9 | 95 | 227 | 130.5 | +4.8 | -1.3 | 2315 | - |
| 11,000* | 4.8 | 2530 | 202.5 | 174.5 | -2.8 | -0.6 | 2475 | 6.4 |
| 31,900** | 31.7 | 100 | 227 | 130.5 | +4.8 | -1.3 | 2315 | - |
| * Full throttle height | ||||||||
| ** Service ceiling | ||||||||
| Estimated absolute ceiling | 32,800 | Greatest height reached | 32,400 | |||||
| R.P.M. stationary on ground | 2175 | Boost pressure lb./sq.in. | +6½ | |||||
SPEED TRIALS
| Height in Standard Atmosphere Feet | True Air Speed M.P.H. | A.S.I. M.P.H. | Compressibility and Position Error Correction M.P.H. | R.P.M. | Boost lb/sq.in. | True Air Speed at Normal Revs. | |
|---|---|---|---|---|---|---|---|
| P.E.C. | Comp. | ||||||
| Sea Level | |||||||
| 1,000 | 291 | 295 | -8.5 | -0.2 | 2335 | +6.4 | |
| 2,000 | 295 | 295.5 | -8.5 | -0.4 | 2370 | +6.4 | |
| 3,000 | 299 | 295 | -8.5 | -0.5 | 2400 | +6.4 | |
| 5,000 | 307 | 294.5 | -8.5 | -1.0 | 2475 | +6.4 | |
| 6,500 | 313 | 294 | -8.5 | -1.5 | 2530 | +6.4 | |
| 10,000 | 328 | 292 | -8.5 | -2.2 | 2650 | +6.4 | 320 |
| 13,000 | 340 | 289.5 | -8.5 | -3.0 | 2755 | +6.4 | 319 |
| 15,000 | 348.5 | 288.5 | -8.5 | -3.5 | 2820 | +6.4 | 318 |
| 16,500 | 355 | 287 | -8.5 | -4.0 | 2875 | +6.4 | 317.5 |
| 18,000 | 361 | 285.5 | -8.5 | -4.5 | 2930 | +6.4 | 316 |
| 20,000 | 360.5 | 276.5 | -8.5 | -4.8 | 2940 | +5.1 | 315 |
| 23,000 | 355 | 259.5 | -8.5 | -5.0 | 2920 | +2.6 | 313 |
| 26,000 | 345 | 240 | -8.2 | -4.9 | 2855 | +0.1 | 310 |
| 28,000 | 333.5 | 223.5 | -7.5 | -4.5 | 2780 | -1.5 | 308 |
| 30,000 | 315 | 202 | -6.0 | -3.8 | 2660 | -3.1 | 306 |
| 18,500* | 362.5 | 284.5 | -8.5 | -4.7 | 2945 | +6.4 | 316 |
| *Full throttle height | |||||||
| Landing and take off tests corrected to standard atmosphere and zero wind | |
| Take off run | 420 yds. |
| Distance from rest to clear 50 foot screen | 720 yds. |
| Gliding in A.S.I. | 80 M.P.H. |
| Stalling speed | --- M.P.H. |
| Best landing A.S.I. | 60 M.P.H. |
| Distance to rest (with brakes) after passing over 50 ft. screen | --- yds. |
| Landing run with brakes | 380 yds. |
| Landing run without brakes | --- yds. |
| Take off speed by Panoramic camera | 86 m.p.h. | |
| Take-off and landing results uncorrected. | ||
| Wind 8 m.p.h. | Temperature 20° | Pressure I.C.A.N. +120 ft |
| Take-off run | 367 yds. | |
| Distance from rest to 50 ft. screen | 640 yds. | |
| Best landing A.S.I. | 60 M.P.H. | |
| Distance to rest (with brakes) after passing over 50 ft. screen | 640 yds. | |
| Landing run with brakes. | 315 yds. | |
Night Flying
Night flying was made at full load with two types of exhaust manifold:
1. Ejector Type.
2. Streamline with special exits. (See photographs).
The usual glim flare path with "Chance" floodlight was laid out in accordance with A.&O.A261/38.
Results
1. Comparing the streamline and ejector manifold it was found that the former were slightly superior. There is considerable flame from both types at full speed in level flight and at cruising speed; although this does not interrupt the view directly ahead, any object in a position slightly below and to one side of the observers path would be hidden. There is no flame noticeable at all with the engine throttled back to any speed below about 1650 r.p.m.
It is considered that the exhaust manifolds cannot be accepted as satisfactory for night flying in the present condition.
2. Cockpit.
The cockpit lighting is found to be satisfactory and switches are conveniently placed. It is noted that the switch controlling the undercarriage position indicator is easily knocked into the "off" position when the throttle is being closed, this would undoubtedly be very disconcerting to a pilot who had throttled back to put down the undercarriage and inadvertently knocked the switch. Although the undercarriage indicator lighting is very bright it is considered that it should be dimmed as it is important that is should be noticeable; it can be easily switched off if necessary.
3. Landing lights.
The landing lights are satisfactory for position but should preferably be more powerful, the lamps fitted are 240 watt.
4. Take-off.
The take-off is very long and in night flying this is rather uncomfortable for the pilot. In this connection it is recommended that a flare path of at least 800 yards in length should be used, and obstruction lights should be used on the highest obstructions around the whole boundary of the aerodrome.
At take-off there is considerable flame from the exhausts, but this is not inconvenient until the aeroplane has passed the last flare when the position of the nose combined with the exhaust flames makes forward view extremely difficult.
The slight swing taking off can be checked easily.
Approach and landing.
The approach and landings were made using the aircraft lights or the Chance light. The approach is rather flat which makes landing easier, and a good estimate of height above the ground can be made. With the engine throttled back there is no flame from the exhaust and at 1600 r.p.m. there is sufficient speed in had to adjust the approach. By using a slight crab-sideslip the line of flares can be kept in view during the approach.
The landing is normal but owing to the poor view ahead landings have to be made well out from the line of flares and it is recommended that the heat of the "T" of the flare path be increased to 300 yards.
Taxying.
The aeroplane in taxying tends to reach the limiting coolant temperature very quickly, and for this reason it is necessary that as little time as possible be spent on the ground with engine running; on no occasion should the aeroplane be left stationary with engine running, unless pointing directly into the wind.
