1.             According to Air Ministry instructions, and A.D.G.B. letter reference ADGB/S.32179/Air Trg. Dated 28th December 1943, Tactical trials have been completed on the Mustang III. Aircraft No. FZ.107 was delivered on 26.12.43, and was checked and weighted as for operational load (total 10,100lbs). For descriptive purposes chief comparisons have been made with Spitfire IX No. BS.552 (clipped wings and a fairly old aircraft), Spitfire IX No. JL.359, normal wings, fitted with S.U. pump carburetor. Brief comparative trials were carried out against Tempest V. No. JN.737 Spitfire XIV No. RB.141, Focke Wulf 190 No. PM.679 and Me.109G No. RN.228.


2.             The Mustang III is a high altitude long-range single seater fighter, armed with four .5” Browning’s in the wings. It is fitted with a V-1650-3 engine (i.e. Packard built Rolls Royce Merlin 61 type), of approximately 1550h.p. It can carry two long-range tanks or two 500lbs. bombs under the wings. In appearance it differs from the Mustang 1 in that it has a different type of engine, four blade airscrew, air intake immediately under the airscrew hub, a deeper fuselage behind the wings housing all the radiators and oil coolers, and a slightly larger fin and rudder. It is a very clean looking aeroplane.

3.             The pilot’s cockpit is similar to the Mustang 1. It has been “cleaned up” considerably. Of particular note are: -

(i)    The only undercarriage-warning device is a red light by the gun site, which lights when the wheels are unlocked. (There is no light when the wheels are locked up or down.)
(ii)    The cockpit, and in particular the instruments, are of American design and consequently seem oddly placed to a British pilot.
(iii)    When the engine is started and the mixture lever placed in “Normal”, the locking unit must be tightened, otherwise the pitch control may creep back on take off.
(iv)    The tail wheel only becomes castoring when the stick is pushed right forward.
(v)    It should be impossible to retract the undercarriage when the weight of the aircraft is on the wheels.
(vi)    There are three trimming wheels for all control surfaces.
(vii)    The flap angle is pre-selected by the control lever in the cockpit. There is a safety stop, which need only be used when carrying the 120-gallon long-range tanks (i.e. does not apply when carrying normal 62.5 gallon long-range tanks). This is to prevent lowering the flaps more than 30 deg.

4.             The control column is well placed and of the stick variety. It is pivoted in both directions at its base.

5.             No “misting up” was encountered during the trials, including flying at and diving from heights up to 35,000 feet.


6.             The Mustang III is very similar to fly and land as the Mustang 1. It is therefore delightfully easy to handle. It is as easy to fly as a Spitfire IX with the exception that the rudder is needed whenever changing bank (in order to prevent skid, and to prevent the sight from swinging off). This soon becomes automatic. The engine feels very smooth.

Flying controls
7.             These are well balanced and positive, especially at high speeds. In comparison with the Spitfire IX : -

(a)    The rudder is heavier. It is far more effective as only a small amount of re-trimming is necessary at high speeds (over 400mph I.A.S.) to keep the aircraft straight. There is no lateral wander.
(b)    The ailerons feel lighter, especially over small movements and in general flying. There appears, however, to be a cushioning effect when full aileron is applied. This is because considerably more stick force is necessary when a quick change of bank is desired.
(c)    The elevators are considerably heavier. They are not tiring, partly because the change of trim with speed is less.

Formation Flying
8.             Because the aircraft is clean, one would expect station keeping to be difficult, but engine response is so steady that formation flying is very easy.

Low Flying
9.             The view forwards and downwards over the leading edge of the wing is the same as the Mustang 1, and therefore better than the Spitfire IX. This helps to make the aircraft easy to low fly. It was not, however, built for low flying operations, and to improve its air to air combat the Unit is advising a certain harmonization which will make the aircraft difficult for ground attack.

Night Flying
10.            Normal flying at night is quite straightforward. The exhaust glow does not seriously inconvenience the pilot. A different type of exhaust stub would be necessary for night fighting.

11.            Apart from certain cockpit lighting troubles listed below, the take off and landing is also quite straightforward. Use of the floodlight is recommended rather than an airfield floodlight, as considerable cockpit dazzle results when using the latter. To prevent exhaust glare on landing, an engine-assisted approach right to the ground is recommended. With a small modification, blinkers could be fitted to the aircraft where a dusk or night landing is anticipated. It is considered that the disadvantage that would be suffered in day combat, would outweigh this luxury.

(a)    Undercarriage warning light is lethal. Unless the British type instrument is fitted, this light must be covered over.
(b)    The cockpit lighting when suitably manipulated is adequate

Compressibility Speeds
12.            Because the Mustang III increases speed so rapidly in the dive, it is not difficult to enter compressibility range at high altitudes (approaching the speed of sound). This can only be done in a dive. The maximum permissible airspeeds at various heights are: -

336mph  "30,000ft
376mph  "25,000ft
422mph  "20,000ft
468mph  "15,000ft
520mph  "10,000ft
574mph  "  5,000ft

13.            The following is a summary of the R.A.E’s instructions (Report No. Aero.1906). Should the speeds at height be exceeded by any type of aircraft. In the dive, the nose may suddenly tend to drop. On no account must the trimming wheel be used to prevent it doing so, but only backward pressure on the stick. When the aircraft has reached a lower altitude where the speed of sound is greater, the aircraft will come out of the compressibility range and behave normally, being pulled out of the dive. Had the trimming wheel been used to prevent the nose dropping when in the compressibility range, there would have been a very sudden nose up tendency on coming out of the compressibility range. The result of such a sudden change of trim is liable to cause structural failure.


14.            A very close comparison can be made because the engines are of very similar design and capacity. The tactical differences are caused chiefly by the fact that the Mustang III is a much cleaner aircraft, is slightly heavier, and has a higher wing loading than the Spitfire IX (43.8lbs. per sq.ft of the Mustang III. against 31 lbs. Per sq.ft)

15.            The Mustang III with maximum fuel load has between 1.5 and 1.75 the range of a Spitfire IX with maximum fuel load. The fuel and oil capacities are 154 gallons and 11.2 gallons respectively, as opposed to 85 gallons 7.5 gallons of the Spitfire IX, both without long-range tanks. With long range tanks, the Mustang can carry a total of 279 gallons of petrol (2 62.5 gall. long range tanks) as opposed to the Spitfire IX’s maximum of 177 gallons (1 90 gall. "Slipper tank").

16.            The fuel consumption at similar boost and rev settings is approximately the same for the two aircraft, but the Mustang is approximately 20 mph faster in level flight. Therefore if the ranges are compared directly according to the fuel capacities of the two aircraft when the long-range tanks are fitted, the Mustang will still have something in hand.

17.            The official speed curves are not yet available. This Unit's speeds runs have therefore not been confirmed. They show, however, that in general for the same engine settings the Mustang III is always 20-30mph faster in level flight at all heights. This is also true for the maximum engine setting of 3,000 r.p.m. 67" (+18 lbs.) or whatever is available, depending on the height. The best performance heights are similar, being between 10,000 and 15,000 ft., and between 25,000 and 32,000 ft.

18.            The Mustang III has a considerably lower rate of climb at full power at all heights. (In a formation take off, Spitfire IX maintains formation with 5 lbs. less boost). At other engine settings and 175 m.p.h. the two aircraft have a similar climb. The Mustang has, however, a better zoom climb in that it can dive 5,000 feet or more and regain its original altitude at a greater speed. It needs less increase of power to regain its previous altitude and speed.

19.            The Mustang III pulls away very rapidly in a slight dive. At the same revs the Spitfire IX requires from 4 to 6 lb. more boost to remain in formation.

Turning Circle
20.            The Mustang is always out-turned by the Spitfire IX. Use of flaps on the Mustang does not appear to improve the turning circle. There is adequate warning of the high-speed stall in the form of elevator buffeting, followed by tail buffeting.

Rate of Roll
21.            Although the ailerons feel light, the Mustang III cannot roll as quickly as the Spitfire IX at normal speeds. The ailerons stiffen up only slightly at high speeds and the rates of roll become the same at about 400 m.p.h.

22.            The all-round view from the pilot’s cockpit is the same as the Mustang 1, therefore generally inferior to the Spitfire IX, but better forwards and downwards on either side of the fuselage. A sliding hood has been designed and is being fitted to service Mustangs. This makes its rear view at least equal to, if not better than the Spitfire IX.

Sighting View and Firepower
23.            The aircraft is fitted with an American 70 m.p.h. sight. A bracket for the G.M.2 sight has been designed and is fitted to most aircraft. If it is not fitted, a universal adaptor as shown at Appendix 'B' (not included here) can be made and fitted by the squadron. Due to the fact that it is most unlikely that the aircraft will be used against ground targets, the highest possible setting for the guns and sights has been chosen to produce the maximum amount of sighting view over the nose. This gives a vertical view of 180 m.p.h. cruising speed, increasing to an unrestricted view at approximately 45° to the vertical, with guns ¾° cocked from aircraft datum. This is considerably better than the Spitfire IX. The guns are cocked up about 2° above the aircrafts cruising line of flight. The fire-power consists of four .5 Browning's in the wings. This is very little compared with the Spitfire.

24.            Armour plating on the Mustang III is provided for the pilot by means of two plates located behind the pilots seat. One 5/16" thick extends from just below the bottom of the seat to a point just level with the pilots shoulders. The other 7/16" thick is attached to the top of this plate and affords protection to the pilot’s head. Otherwise protection is provided by the ¼" armour plate fire-wall, the engine, and the 1½" armour plate glass windshield. ¼" armour plate is also located immediately forward of the coolant tank on the forward end of the engine. There is no armour plate on the fuel tanks, but the tanks themselves are self-sealing.


Maximum Endurance
25.            By comparison the Spitfire XIV has no endurance.

Maximum speed
26.            There is practically nothing to choose in maximum speed.

Maximum climb
27.            The Spitfire XIV is very much better.

28.            As for the Spitfire IX. The Mustang pulls away; but less markedly.

Turning Circle
29.            The Spitfire XIV is better.

Rate of Roll
30.            Advantage tends to be with the Spitfire XIV.

31.            With the exception of endurance, no conclusions should be drawn, as these two aircraft should never be enemies. The choice is a matter of taste.


Maximum endurance
32.            By comparison, the Tempest V has no endurance.

Maximum speed
33.            The Tempest V is 15-20mph faster up to 15,000 ft. There is then no choice until 24,000 fee when the Mustang rapidly pulls ahead, being about 30 m.p.h. faster at 30,000 feet.

Maximum climb
34.            These compare directly with the results of the speed tests. At similar performance height, the Tempest has the better zoom climb.

35.            The Tempest tends to pull away.

Turning circle
36.            The Tempest is not quite as good.

Rate of Roll
37.            The Tempest is not so good. This attribute of the Tempest V may be improved upon in later aircraft.

38.            The Mustang has endurance and general performance above 24,000 feet. Conclusions should not be drawn below this height, but the Tempest has a better speed and climb below 10,000 feet.


Maximum speed
39.            The FW.190 is nearly 50 m.p.h. slower at all heights, increasing to 70 m.p.h. above 28,000 feet. It is anticipated that the new FW.190 (DB.603) might be slightly faster below 27,000 feet but slower above that height.

40.            There appears to be little to choose in the maximum rate of climb. It is anticipated that the Mustang III will have a better maximum climb than the new FW.190 (DB.603). The Mustang is considerably faster at all heights in a zoom climb.

41.            The Mustang can always out-dive the FW.190.

Turning circle
42.            Again there is not much to choose. The Mustang is slightly better. When evading an enemy aircraft with a steep turn, a pilot will always out-turn the attacking aircraft initially because of the difference in speeds. It is therefore still a worthwhile manoeuver with the Mustang III when attacked.

Rate of Roll
43.            Not even a Mustang III approaches the FW.190.

44.            In the attack, a high speed should be maintained or regained in order to regain height initiative. The FW.190 could not evade by diving alone. In defense a steep turn followed by a full throttle dive should increase the range before regaining height and course. Dog-fighting is not altogether recommended. Do not attempt to climb away without at least 250 m.p.h. showing initially. Unfortunately, there is not enough information on the new FW.190 (DB603) for any positive recommendations to be made.


Maximum Speed
45.            The Mustang III is faster at all heights. Its best heights, by comparison, are below 16,000 ft (30 mph faster approx.) and above 25,000 ft. (30 mph increasing to 50 mph at 30,000 ft).

Maximum climb
46.            This is rather similar. The Mustang is very slightly better above 25,000 ft. but worse below 20,000 feet.

Zoom Climb
47.            Unfortunately the Me.109G appears to have a very good high-speed climb, making the aircraft very similar in a zoom climb.

48.            On the other hand in defense the Mustang can still increase the range in a prolonged dive.

Turning Circle
49.            The Mustang III is greatly superior.

Rate of Roll
50.            Not much to choose. In defense (in a tight spot) a rapid change of direction will throw the Me.109G's sight off. This is because the 109G's maximum roll is embarrassing (slots keep opening)

51.            In attack, the Mustang can always catch the Me.109G, except in any sort of climb (unless there is a high overtaking speed). In defense, a steep turn should be the first manoeuver, followed if necessary, by a dive (below 20,000 feet). A high-speed climb will unfortunately not increase the range. If above 25,000 ft. keep above by climbing or all-out level.


52.            There is a serious loss of speed of 40-50 mph at all engine settings and heights. It is, however, still faster than the FW.190 (BMW.801D) above 25,000 ft. Although slower than the Me.109G.

53.            The rate of climb is greatly reduced. It is outclimbed by the FW.190 (BMW.801), Me.109G and FW.190 (DB.603).

Zoom Climb
54.            The Mustang III is still good in the zoom climb (attack), but is still outstripped (defense), if being followed all the way by the FW.190 (BMW.801D), and definitely outstripped by the Me.109G.

55.            So long as the tanks are fairly full, the Mustang still beats the FW.190 (BMW.801D) and the Me.109G in a power dive.

Turning Circle
56.            The tanks do not make quite so much difference as one might expect. The Mustang III can at least turn as tightly as the FW.190 (BMW.801D) without stalling out and therefore definitely more tightly than the Me.109G.

Rate of Roll
57.            General handling and rate of roll are very little affected.

58.            The performance of the Mustang III is greatly reduced when carrying drop-tanks. Halfhearted attacks could still be evaded by a steep turn, but determined attacks would be difficult to avoid without loosing height. It is still a good attacking aircraft especially if it has the advantage of height.


Gun Harmonization
59.            No difficulty was experienced in harmonizing the guns in the manner described above (Para. 23). The American Reflector Sight mounting bracket has no adjustment in elevation for harmonization. The necessary movement was obtained by moving and locking the adjustable reflector glass.

Gun Firing
60.            The guns were fired in the air at various heights up to 25,000 feet. There was one stoppage, due to a lightly stuck cap; otherwise the guns fired 100%. The installation proved satisfactory, and the aircraft a steady gun platform.

61.            This was carried out by two armourers only, and the time taken was :-

First re-arm -7½ mins.
Second re-arm -7½ mins.

The capacity of the tanks is :-

Inboard guns - 350 rounds each.
Outboard guns - 280 rounds each.

Cine-gun Installation and Harmonization
62.            The G.S.A.P. Cine Camera with 3 inch lens is fitted and was harmonized ¼" from the top. No difficulties were encountered.

Air Tests
63.            Films were taken at heights between 5,000 and 30,000 feet, all of which were satisfactory.

64.            One V.H.F. set is fitted, the control box being fitted on the right-hand side of the cockpit. This position is rather awkward. It was found easiest to use the left hand for operating it.

65.            The American economizing system is fitted. It is necessary to adapt the connections at a suitable place if the British type face masks are to be used. If the British F, G, or H type mask is to be used, it is essential to blank off the compensating valve in the side of the face piece. The American system draws in the appropriate amount of air at the control box.

Engine Temperatures
66.            These are well controlled if the oil and coolant switches are left on "Automatic". The temperatures appear to remain constant however the aircraft is flown.

Starting Hints
67.            Starting is quite straightforward if carried out as per starting instructions for Bendix Stromberg Carburetors.

Servicing hints
68.            The servicing is the same for Mustang 1 and 1A. Ground equipment is interchangeable, except for propeller kit, which has to be exchanged for a Hamilton Propeller kit, instead of a Curtiss electric. Flaps have an angular movement of 50 °. Movement restricted to 30 ° when carrying ferry tank (125 gallons) by use of lock bar on flap quadrant. This should be fitted in place by the rigger fitting the tanks. No restriction is necessary when using combat tanks (62.5 gallons).

69.            The rammed and unrammed air control lever in the cockpit of the Mustang III No.FZ.107 was inclined to creep back half way between settings during flight. This caused the pilot to be unable to produce the required amount of maximum boost and increased petrol consumption. Much useless flying was carried out before the effects were noticed. For use "at home" it is therefore suggested that for squadron aircraft the lever should be wired in the "Ram-air" position with copper wire.


70.            The Mustang III is a delightful and easy aircraft to fly.

71.            Its advantages over the Spitfire IX lie in a considerably greater range and greater all round speed. It can outstrip the FW.190 in a dive, followed if desired by a shallow climb. Its only serious drawback is a slightly less rate of climb than the Spitfire IX, particularly at height.

72.            A pilot needs to understand the effect of compressibility speeds. Practices should not be attempted.


1.            Pasting –lbs of boost readings on to the face of the boost gauge for ease of reading for British pilots, as below.

  of HG  
Lbs. per
22  -4
26  -2
30    0
34  +2
38  +4
44  +7
48  +9

2.            Wire-up the air control lever in the cockpit. (Para.69)

3.            For night flying, cover over the Undercarriage Warning Light. (Para 11a)

AFDU/3/21/36Wing Commander
8th March 1944. Commanding, A.F.D.U.

Transcribed by Neil Stirling

WWII Aircraft Performance   Mustang Performance Trials