If not for the desperate wants and needs of the RAF in late 1939 and early 1940, there would never have been a Mustang story to tell. For it was the RAF that first ordered the airplane into production, named it and was the first air arm to fly the Mustang into aerial combat against the Axis powers in the war.

It was during this time when Great Britain was hard pressed to acquire what it thought was an adequate number of combat aircraft. Its very own airframe and powerplant facilities were already going full-bore to build enough airplanes and engines to meet the challenge put forth by the Axis powers. It foresaw an invasion by Germany and knew that it had to have hundreds if not thousands of fighter aircraft to help push it back into the Channel. Even though it had an ace up its sleeve – the Chain Home radar system to give early warning of approaching enemy aircraft – it needed a large number of fighter aircraft to shoot them down. So, as discussed in Part 1, Great Britain turned to the US, specifically NAA, to acquire additional fighters licence-built through Curtiss for NAA-built P-40D airplanes. This, however, never came to fruition due to the salesmanship of Kindelberger whereby an NAA designed and built fighter would be produced. The first result of this was, of course, the one-of-a-kind NA-73X fighter demonstrator 


The resulting Mustang fleet of fighters had come forth from a deal made between the British Government and NAA. The US Army Air Corps had little to no involvement in the early development processes. However, NAA had to acquire US Government permission to manufacturer combat aircraft for Great Britain or any other friendly nation. So, under the Foreign Release Agreement, NAA was forced to supply two production NA-73 airplanes to the USAAC as XP-51 airplanes which it did in 1941.

Since RAF Fighter Command was the first buyer of the Mustang and hence its first user, it was also the biggest non-American user air force to employ the fighter. And between late 1941 and mid-1945, the RAF acquired a total of 2,570 Mustang aircraft.

It was not until mid-1942 that the recently created US Army Air Forces (as of 20 June 1941) began to show interest in the Mustang, more than two years after Great Britain had. In any event, production Mustangs were flowing steadily into Great Britain. Eventually, the RAF would field six primary and two secondary variants which are now discussed.

Royal Air Force Mustangs

Mustang Mark I 

The RAF ordered 620 Mustang Mark I airplanes in two production batches. The first batch under NA-73 included 320 airplanes while the second under NA-83 produced 300 additional Mk.I airplanes. All of these aircraft were strictly purchased for use by the RAF and never received USAAF designations or USAAF serial numbers. Of the 620 airplanes built, the RAF received 608 of them. Two were retained by NAA (the first NA-73 and first NA-83) and the remaining ten were sent to Russia for evaluation by its air force.

Two more NA-73 airplanes, the fourth and tenth ones built, were constructed at the expense of NAA to meet the Foreign Release Agreement (approved 4 May 1940) that required that the USAAC Materiel Command would freely receive two experiment XP-51 airplanes for its evaluations. Thus, in all, 322 NA-73 airplanes were built. The NA-73 was ordered on 29 May 1940 and the NA-83 ordered on 24 September 1940. Apparently, the British Purchasing Commission had great faith in NAA since the NA-73X demonstrator did not even fly until 26 October 1940, more than a month after it had ordered the NA-83.

The first NA-73 (AG345) made its first flight on 23 April 1941 followed by the second (AG346) on 3 July 1941.

The first XP-51 had flown during the interim on 20 May. It was this second airplane that was the first Mustang Mk.I sent to Great Britain and arrived by ship in Liverpool on 24 October 1941 and was trucked to the Aeroplane and Armament Experimental Establishment (A&AEE) at RAF Boscombe Down for evaluation. It then went to RAF Duxford for further evaluation by the Air Fighter Development Unit (AFDU). The very first Mustang Mark I (AG345), first flown on 23 April 1941, was retained by NAA for ongoing evaluations and/or modifications to the type. By 1 January 1942, 138 Mk.I airplanes had been accepted by the RAF. The 320 NA-73 Mustang Mk.I airplanes received RAF serial numbers AG345 to AG664; the 300 NA-83 Mustang Mk.I aircraft got RAF serial numbers AL958 to AL999, AM100 to AM257, and AP164 to AP263.

The very first production NA-73 and still unpainted was RAF serial number AG345. This Mustang Mk.I was retained by NAA for developmental evaluations and was used in part to test dive brakes and bomb release mechanisms on the forthcoming A-36 light attack bomber. (NAA via Chris Wamsley)

AG345 on its first flight with NAA test pilot Lou Wait at the controls on 23 April 1941, almost six months after the first flight of the NA-73X on 26 October 1940. The airplane was painted in RAF camouflage and national markings despite its staying stateside. (NAA via Chris Wamsley)

The number two Mustang Mark I (AG346), first flown on 3 July 1941, and subsequent NA-73 airplanes were equipped with armament comprised of eight machine guns: four .30 calibre and four .50 calibre. Two .50 calibre guns were installed in the lower nose (200 rounds per gun) and these were synchronised to fire through the arc of the propeller. The remaining six guns were installed in the wings, one .50 calibre in between two .30 calibre per wing (500 rounds per gun).

A number of other Mark Is were evaluated and it was soon found that these airplanes were best suited for low altitude missions such as photographic reconnaissance and ‘Rhubarb’ attacks strafing airfields and targets of opportunity such as vehicle convoys and trains. A large number of Mark Is were fitted with F-24 cameras to perform high-speed (up to 400 mph), low-altitude (under 15,000 ft) photo-recce sorties primarily over France while the non-camera equipped Mark Is primarily performed the Rhubarb sorties. These missions began in early 1942 and continued throughout the war. The F-24 cameras were installed just aft of the pilot’s seat aimed outward and aftward on the left side of the fuselage. A second camera, mounted vertically (looking downwards) was later installed just forwards of the tail wheel into a number of Mark Is for higher-altitude (above 15,000 ft) photo-recce missions. The RAF had accepted 138 Mark Is by 31 December 1941.

This freeze frame clearly shows the details of the nose of AG346. Visible features show two protruding barrels of its nose-mounted .50 cal. machine guns, three-bladed Curtiss Electric propeller and spinner, and its six left-bank V-1710-39 (F3R) engine exhaust outlets. (Peter M. Bowers Collection)

This Mustang Mk.I (AG346), the second production Mustang, was the first to be delivered to the RAF in Great Britain. It was transported cross country from Inglewood to New York City via railroad, then onboard a cargo ship to Liverpool, England, where it arrived on 24 October 1941. It was first flown in Great Britain on 11 November 1941. (NAA via Chris Wamsley)

The fourth production Mk.I (AG348). It was first flown by Bob Chilton on 19 September 1941 and this particular Mustang Mark I was turned over to the VVS (Russian Air Force) in mid-1942 for its evaluation with several other Mk.I airplanes. As good as the Mustang was, the VVS was not impressed preferring Bell P-63 Kingcobra instead. The shape of the laminar flow airfoil is clearly defined. (Peter M. Bowers Collection)

This bird’s-eye view of AG348 from the roof of its assembly building details the squared flying surfaces of the Mustang Mk.I and all subsequent Mustangs. Heretofore, all pursuit-type monoplanes featured rounded tips on their flying surfaces which, according to Schmued, ‘...created unwanted parasite drag.’ The squared-off tips on the flying surfaces of the Mustang helped to eliminate this. (NAA via Chris Wamsley)

This late production Mustang Mk.I (AG633) flaunts its colours in mid-1942 while in operation with the Army Cooperation Command. Its smiling pilot had named the airplane ‘Eileen’ that is barely discernible just forwards of the canopy windshield. An F.24 camera is fitted just aft of the pilot’s seat. (Royal Air Force Museum)

On 19 May 1942, the A&AEE at RAF Boscombe Down near Amesbury published the results of flight-test operations with the seventh production Mustang I (AG351) powered by a 1,150 hp Allison V-1710 F3R (V-1710-39) engine spinning a three-bladed Curtiss Electric (constant speed) 10-ft-6-in.-diameter propeller; NA-83 used a three-bladed constant speed Curtiss Electric propeller as well.

A No. 414 Squadron NA-83 Mustang Mk.I (RAF AM186) flies over the British countryside on 25 March 1944. The RAF employed its Mk.I airplanes primarily through the Army Cooperation Command as armed tactical reconnaissance aircraft. (Photograph courtesy of the Royal Air Force Museum)

Most of the P-51Bs went to the USAAF but a large number went to the RAF as Mustang Mark IIIs. This is one of 400 P-51B-1-NA (43-12342) Mustangs while still at the NAA factory in Inglewood. (Stan Piet collection)

Mustang Mk.I Specifications

Length: 32 ft 3 in. 

Height: 12 ft 2 in. 

Wing span: 37 ft 

Wing area: 233 sq ft 

Propulsive system: one 1,150-hp Allison V-1710-39 (F3R) Vee engine 

Propeller: three-bladed constant speed 10-ft-6-in.-diameter Curtiss Electric propeller 

Empty weight: 6,278 lb 

Gross weight: 7,967 lb 

Maximum speed: 382 mph at 13,000 ft 

Armament: four wing-mounted .30 calibre machine guns (500 rounds per gun); two nose-mounted and two wing-mounted .50 calibre machine guns (200 rounds per gun)

Mustang Mark I (Dive Bomber) 

The RAF received a single factory-fresh NA-97 A-36A-1-NA (42-83685) for evaluation at its Aeroplane and Armament Experimental Establishment (A&AEE) at Boscombe Down in March 1943.

It was issued RAF serial number EW998 and was given the designation Mustang Mark I (Dive Bomber). It was the twenty-third of 500 A-36A airplanes manufactured (NAA serial number 97-15903), and after a series of performance and weapon delivery tests, the RAF decided to procure the Hawker Typhoon fighter-bomber instead. Whether this airplane was returned to the USAAF or retained by the RAF remains unclear.

Six additional A-36A-1-NA airplanes from the 12th Air Force in the MTO were obtained by the RAF in early to mid-1944 for ground support duties. They were issued RAF serial numbers and they included: HK944 (42-84018), HK945 (42-83898), HK946 (42-84117), HK947 (42-84107), HK955 (42-83906) and HK956 (42-83829).

Mustang Mark IA 

The RAF ordered 150 NA-91 Mustang Mk.IA airplanes on 7 July 1941. These were issued RAF serial numbers FD418-FD567. However, by this time the new Lend-Lease programme was in force and these aircraft had to be ordered as defence aid through the USAAF and designated P-51 – USAAF serial numbers 41-37320 to 41-37469.

With the advent of Pearl Harbor on 7 December 1941, however, a large number of these were diverted to the USAAF and the RAF only received a limited amount. After the US Lend-Lease Act was put into effect on 11 March 1941, all subsequent foreign aircraft orders had to go through the US War Department and its contracting agencies. And since the Mustang was a US Army Air Forces programme, additional P-51 airplanes had to be ordered through a USAAF contract. Therefore, the USAAF ordered 150 NA-91 P-51 airplanes to be delivered to the RAF as Mustang Mark IA aircraft. However, after the USAAF had realised the potential of the Mustang for its own use, it held back from full delivery and retained thirty-nine of the P-51s for its own purposes. The Mustang Mark IA designation was applied to 111 out of 150 California-built NA-91 P-51 airplanes received by the RAF. These were assigned intermittent RAF serial numbers FD438 to FD449 (12), FD465 (1), FD470 to FD509 (40), and FD528 to FD587 (60). The RAF had been slow to adopt the Mustang Mark I and Mustang Mark IA aircraft and the Army Cooperation Command was the first user of these two types in the Second World War.

British Army Cooperation Tactical Employment of the Mustang Mark I and IA (P-51)




APO 520 

26 August 1943


British Army Cooperation Tactical Employment of the Mustang Mark I and Mustang Mark IA (P-51).


Commanding General, Northwest African Air Forces, APO 650.

(Attention: Tactics Officer) 

The following report on the Cooperation Tactical Employment of the Mustang Mark I and Mustang Mark IA (P-51) has been submitted by Colonel C. W. Bunch, Operational Engineering Officer, Northwest African Strategic Air Force:


1. Wing Commander Peter Dudjeon, a former squadron commander of one of the Army Cooperation Units, was contacted on 31 May, 1943, for the purpose of obtaining information on their daylight intrusion raids (Rhubarbs) using the North American Mustang I and IA aircraft. W/C Dudjeon was most helpful and cooperative in spite of the fact that the Army Cooperation Activities were being, that day, taken over by the R.A.F. Fighter Command and all personnel was engaged in moving to the new post. Additional time was spent with him after he had moved to the new headquarters.


2. This phase of the Army Cooperation effort started as a photo reconnaissance operation using the Mustang I fitted with two cameras; a vertical camera in a quick detachable mount and an oblique camera mounted aft of the pilot’s head and “shooting” out the left side of the canopy through a small circular opening cut in the Plexiglas. The cameras were automatic in their operation and controlled by the pilot. 

3. These aircraft were equipped with four .50 cal. and four .30 cal. machine guns with a total of 1000 rounds for the .50 cal. guns and a total of 3492 rounds for the .30 cal. guns. 

4. The long range (fuel capacity 180 U.S. gal) of this aircraft made it an excellent tactical reconnaissance aircraft and its armament made it effective against most ground targets. As their operation progressed, they swung more and more to offensive reconnaissance and began to take advantage of targets of opportunity until the operation finally developed into a strategic effort against ground objectives such as railway locomotives, canal barges, heavy motor transport vehicles and aircraft on the ground. 

5. These daylight intrusion raids (Rhubarbs) were very successful largely due to the care and effort which went into the planning and operation of their missions. The theme was the destruction of those targets designated with the minimum number of casualties. That this was achieved is attested by the record of this squadron which in 18 months of operation destroyed or damaged severely, 200 locomotives, over 200 barges and an undetermined number of enemy aircraft on the ground. This was accomplished with only one ship being shot down by enemy fighters, five ships lost by enemy flak and two ships vanished without any record or information as to what happened to them. During this period of operation, they were never once intercepted over enemy territory. This included raids over Holland, occupied France, Belgium and Germany, the longest one having been a flight of over 1000 miles. Their furthest victory was a locomotive shot up just outside Wilhelmshaven, an airline distance of approximately 350 miles from their base. 

6. The results of a typical raid are as follows: two ships were gone from the base 3:40 (90 miles was flown over Germany); each ship used approximately 118 U.S. Gallons of fuel. The two Mustangs destroyed or damaged 5 locomotives, 5 loaded goods barges, and one “R” boat. The Mustangs were unharmed. 

7. It is felt that with the present load on the enemy shops and the possible shortage of the high quality steel necessary for the boiler tubes that a locomotive that has been holed by .50 cal. machine gun fire will be out of service from 3 weeks to 6 months depending on the location with reference to repair facilities. In some cases the locomotive explodes; if it does not explode, often the escaping steam blows the fire out of the fire box into the cab. The repetition of these attacks has definitely made the profession of locomotive engineer unpopular in that part of Europe within range of the Mustangs. 

8. In general their tactics consist of sending into a given target area a sufficient number of ships to “saturate” the enemy air defense warning system and to cause the maximum confusion through a multiplicity of plots and through pre-determined zig-zag courses laid out in short legs (6 mins. each) arranged so as to carry them parallel to their objectives (canals and railways). The most usual formation employed is a pair line abreast, although four line abreast or two and sometimes three flights of four abreast have been used. It was found that the smallest unit of two abreast worked out better in most cases. The formation proceeds to a given point off the enemy coast at which time it breaks up into the smaller units who then fly their respective pre-determined course so as to cover the particular section to be attacked. All crossing of the enemy coast are at as nearly the same time as possible. 

9. The flight from the home base to within 40 miles of the point of crossing the enemy coast is made at 200 IAS, 1100 R.P.M. and 30.0” Hg. at between 25 to 50 feet altitude. Upon reaching the above mentioned point, the power is increased to maximum cruising (250-275 mph – 2600 R.P.M. – 34.5” Hg.) and left there during the entire time over enemy territory and until 40 miles away from enemy coast on the return trip. If a landfall is not made within 5 miles of the predetermined point at which the enemy coast was to be crossed, then the flight should return home immediately because the entire flight plan will be thrown off too much, and also, since the entry point is chosen with careful regard for the flak map, there is apt to be serious trouble from this cause. 

10. Just at the point of crossing the coast, an attempt should be made to “flash” in as quickly as possible – pulling up slightly and then diving with a burst of gun fire in the direction of any gun locations that may be firing – once across the coast, going back to tree top height, taking advantage of all the natural cover possible. Attacks on locomotives should never be made near stations or other locations where flak defenses are apt to be concentrated, but should be made between the stations out in the country where there is usually only single track; in which case the damaged locomotive holds up traffic until a wrecker or another engine can be brought in to tow the disabled engine to a siding. It often happens that the locomotive explodes which usually causes damage to the track and roadbed further disrupting traffic. Attacks should be alternated between the two members of the flight, one covering while the other makes the attack. Each pilot of the pair should be constantly searching for enemy aircraft so as to avoid a surprise attack by enemy pursuit. Attacks should be made from one side of the railway, canal or roadway to the other – never along. An attack should never be repeated even though the objective has been missed, because the protecting element of surprise is no longer present. At a speed of 270 mph and at zero altitude, the search area is comparatively limited and targets appear quickly. Experience and alertness are required to pick out these targets in time to make an attack. It has been found necessary for inexperienced pilots to fly at not over 250 mph until they acquire the necessary skill and experience. It has also been found that depressing the flaps 5º will have little effect on the speed, but it will change the altitude of the aircraft so that targets can be more easily seen over the nose. 

11. The route in enemy territory usually involves about 90 miles, following the predetermined zig-zag course which has been laid out with reference to the latest flak map and with maximum target possibilities in mind. The six minute legs of the courses just about give the enemy time to pick out a plot, determine the speed and course, and dispatch interception. The course is then changed and the interception is always about 6 minutes behind time or out of phase. Strict adherence to the original flight plan must be maintained for many reasons, one of which, is so that the rendezvous after the enemy coast is left will not be prevented and thereby deprive the entire flight of the protection offered by supporting numbers during the trip home when interception is more likely. 

12. At the point of leaving the coast, flash out as fast as possible, weaving and changing place in the flight. Make use of cloud cover if possible. After 40 miles from the coast throttle back to 200 mph (1100 RPM and 30.0 Hg) and proceed to the home base. 

13. It has been found that speed is not protection or at least not sufficient protection from ground fire and weaving must be employed for the maximum protection. 

14. The use of cloud cover is an important feature of these operations. 10/10 clouds at 500 ft. would represent an almost ideal condition. For operation deep into Germany 10/10 clouds at not over 1500 ft. is required while 6/10 to 7/10 clouds at 1500 ft. is allowable for operations into Holland, Belgium and France. Since the only interception has been at sea every effort is made to take advantage of such cloud cover during the over-water portions of the return trip. On the outgoing trip low flying and proper selection of the approach course gives comparative security from detection by radar until a landfall is made. Absolute radio silence must be observed on the outgoing trip and if for any reason this silence is broken, the flight must return to the home base immediately since the enemy will have been alerted. Once the coast is crossed, there is no longer any great necessity for radio silence, since security and complete concealment are no longer possible; however, even then it is desirable to use the utmost discretion in the use of the radio, preserving silence unless an emergency warrants the use of the radio.


15. Specialized pilot training is a very important phase in this operation. New pilots coming with the unit are not allowed to go on an operational flight for several months. They must have become familiar with every phase of the operation before going out on their own. They are thoroughly instructed in radio procedure and discipline. They must know their airplane completely and have the responsibility for keeping their own ground crew on their toes. They are allowed to make changes in their own aircraft for their personal comfort and are encouraged to keep the wings polished and free from scratches. In fact, no one is allowed to climb up on the wings without a pad in place. The pilots enter from the front stepping on the wing at only two designated spots. They must run slow speed fuel consumption tests so that they are convinced that it is possible to operate at 200 mph and approximately 20 gal per if they keep the R.P.M. down to 1100. They must supervise the swinging and checking of their own compass in order to increase their confidence in their equipment. Blind flying practice is carried out at all times. Each pilot is so trained that he can “lay on” a complete mission in all details. 

16. Each day there is range estimation and gunnery practice. They are encouraged to go out in pairs and practice “shadow shooting” over the water in addition to the carefully scored aerial gunnery practice. Competition is introduced in all phases of the training with the possibilities of becoming a flight leader as a reward. 

17. Formation flying is practiced continually by twos and fours until the pilots are automatic in their ability to handle themselves in a formation of either type. After they have been paired off, they are usually not separated but continue to fly with the same partner – developing their own system of signals for target designation, etc. The four plane line abreast formation is very maneuverable but it is difficult to fly. Proficiency is acquired only through constant practice. The two plane line abreast formation is most usually used as it is the more flexible. 

18. They are briefed constantly on enemy tactics and the capabilities of their own aircraft compared to the enemy opposition. 

19. It has been found that the Mustang is faster than the Me 109 and the Fw 190, and that 4000 to 8000 is a good altitude at which to catch the enemy. At sea level, the Mustang can run away from any enemy aircraft they have encountered to date. The pilots are schooled to run rather than fight because their main objective is the destruction of ground targets, not to fight enemy aircraft. They are instructed in the use of flaps in combat to reduce their turning radius (which with flaps is shorter than the Me 109 or Fw 190). At least one Fw 190 has been made to spin in through the use of a small amount of flap by the Mustang when engaged in a turning contest at low altitude; the Fw 190 tried to tighten his turn to keep the Mustang in his sights after the pilot had dropped his flaps slightly but spun out of the turn. They practice combat, evasion, flak evasion, low altitude flying continually. 

20. They are taught the importance of the proper flying equipment. Goggles must be worn at all times while over enemy territory to protect their eyes from windshield and hood splinters. They must wear escape boots, flying suits (so as to provide two or more layers of clothing) helmets and gloves at all times for the protection those give in case of a fire in the air. In short, they are taught to know their aircraft and equipment and how to use both to the maximum advantage. 

21. A considerable amount of time is spent in training for emergency situations. They practice forced landing under all conditions – particularly the conditions following an engine failure at low altitude over land. It has been found that if the Mustang must be “ditched” it will go under like a shot and that “ditching” must be avoided. If the engine fails at 200 mph and 25 ft. altitude, the aircraft can be pulled straight up to about 500 feet at which point the pilot jumps, but this must be practiced in order to convince the pilots that it is possible if everything is done without delay. In case of such a failure over water, the I.F.F. should immediately be shifted to switch position #3 which is an emergency position giving a wide emergency plot on any radar screen which happens to be following the aircraft at the time. All stations will drop all operational plots and follow an emergency plot giving the location immediately to the nearest Air Sea Rescue Unit. If the aircraft must be “ditched” they are told to use coarse pitch, no flaps, radiator shutters closed, slow up as much as possible and stall onto the water along the swell regardless of wind. The hood should be off, parachute harness off, safety belt and Sutton harness taut, one hand on the instrument panel, and the head slightly forward and rigid. They are cautioned that as long as the engine will run enough to fly, they should keep the aircraft headed for home and endeavour to reach home even if the engine is ruined. They are taught how to handle their engines in such emergencies; if the oil temperature goes up – reduce R.P.M. and increase boost; if the glycol temperature goes up, increase R.P.M. and reduce boost. During their period of operation the squadron did not have any complete engine failures, nor did they have any internal glycol leaks. 

22. They are continually lectured by intelligence officers concerning the general situation in the countries or territories over which they are flying. Particular emphasis is placed on the problems of escape and the changes in the escape situation from time to time. The customs and dress of the people are studied – stories of escapes are discussed and wherever possible people who have escaped discuss their experiences with the pilots. Everything is done to make them more escape conscious. They are encouraged to have personal weapons with them in the aircraft (knife or black jack rather than a gun) and to exercise their own ingenuity in concealing compasses, small saws, etc., in their clothes. They have many types of such compasses; a few are made more or less obvious so that they will be taken leaving the concealed ones for later use. Battle dress should consist of clothing which will not look out of place or strange in the locality where the pilot is apt to be forced down. 

23. If they are down in enemy territory, they are taught never to do anything without a “plan”. Each stage of the escape must be planned. First their aircraft must be destroyed – then clothes must be arranged so as not to attract attention. They must know thoroughly the contents of their escape kit and how to use everything. They should avoid doing anything which would attract undue attention, such as over tipping – lack of knowledge of the money, etc. It has been found that the poor people of a country are always more ready than any other class to help in escaping. They should remember the names and addresses of people who help them and should always avoid all people of their own nationality. 

24. At the operations room, they have a canvas bag for each pilot with his name on the bag. In this bag are his escape kit, his pass which has a civilian photograph and his name, rank and serial number, two photographs (to be used on forged passports if necessary) in which he duplicates as close as possible the appearance of a native of the locality where he is apt to land (manner of dress, moustache or not, etc.) and official money of this locality, also in this bag are his personal weapons, sheath knife, wooden flash light, whistle, small razor, mirror, goggles and gloves. He removes this equipment from the bag and into the bag puts the contents of his pockets (the things mentioned above are all that he can carry with him on a mission) papers, notebooks, etc., his necktie. His escape boots should be kept with the bag and not worn until he leaves the operations room; otherwise they will be partially worn and may not last when he needs them most. His shirt collar is opened and tie removed because of the danger of shrinkage in case he gets in the water and is then unable to loosen his clothes. 

25. As the pilots leave the operations room, their flying equipment is inspected and the last thing he fastens on himself is a sheath knife placed outside everything and in easy reach so that if a chance hit should cause his “Mae West” to inflate in the air, he can puncture it. 

26. During their training period, the pilots are first sent on shipping reconnaissance missions to allow them to get familiar with the aeroplane, navigation and to check their fuel consumption, while doing something which they feel is operationally important. They are next required to simulate three practice Rhubarbs over friendly country – then they are sent out to sea, out of sight of land, and required to fly a predetermined 3 leg course and simulate an approach to the coast and an attack on a land objective. When they are proficient at the above, they are then ready for their first operational Rhubarb.

Objective Planning

27. If the desired target destruction and damage is to be secured with minimum casualties, then very careful training alone is not enough – it must be supplemented with the most careful planning. Requests for “hurry-up” or “flash” missions will have to be ignored and only those missions attempted in which there is time available for planning all details or complete “laying on” of the mission in which no details are slighted. 

28. An experienced unit with all facilities available can “lay on” a mission in 1½ hrs including the briefing. They have more or less control over their target selection since their effort is unsupported and requires no coordination other than in a general way. Their targets are chosen by information contained in photographs, by information obtained from previous missions and by a general knowledge of the transportation system of a given locality. 

29. Once a target is decided upon – for instance a certain area where there are several important rail lines and perhaps a canal – all the latest intelligence is made available. This includes flak maps, radar locations, locations of airfields, fighter strength and disposition, knowledge of other friendly simultaneous action, etc. The number of aircraft is set and those pilots alerted. Those pilots do not leave the post after being alerted nor are they allowed to drink – They are sent to bed early. 

30. The points of entry into enemy territory by the various flights are carefully chosen with regard to the flak map, the air defense warning system, enemy fighters and target proximity and coverage. Separate zig-zag courses of approximately 6 min. length at 275 mph are planned so as to give the maximum coverage in the target area without the separate flights interfering with each other or crossing the path already covered by another fighter (in this case a flight is assumed to be the smallest unit – two abreast). Every element which will contribute to the surprise of each flight is taken into consideration. The distance to be covered by each flight in enemy territory is usually in the neighborhood of 90 miles for reach flight. The points of exit are chosen with regard to the exit points and the route home plotted on the overlay. 

31. The course for the mission for any one flight consists of a number of legs of varying distances and directions. At the early morning briefing, the pilots are allowed to do most of the work in obtaining the data for his particular flight. One pilot will measure all the distances with another checking. Another pilot will obtain all the true tracks with proper checking. All the data is entered on a form 433-A and from the last minute meteorological report and the compass card of each airplane, the pilots work out their magnetic courses, true airspeeds and times. All times, airspeeds and directions will be the same from the base to the dispersal point (50-60 miles from the coast), but different for the individual flights over enemy territory and then the same again (usually) for the trip home from the rendezvous point. Gun cameras in the left landing light location take pictures of all action and verify claims.

Performance of the Mustang I and IA 

32. The record of the Mustang I and IA is excellent. The pilots all like to fly it and its success has been due to its reliability, simplicity and the fact that it is faster than any contemporary aircraft at low and medium altitudes.

NAA produced 310 NA-99 P-51A-1-NA (100), P-51A-5-NA (55) and P-51A-10-NA (155) airplanes in Inglewood. Fifty went to the RAF as Mustang Mk.II aircraft. Shown here is an unidentified P-51A (tail number 75) undergoing engine maintenance somewhere in India during its CBI campaign. (National Museum of the USAF)

33. This aircraft is powered with the Allison 1710-39 engine having a rated power of 1150 H.P. at 3000 R.P.M. and 44” Hg. at 12,000 ft. The engine was originally equipped with an automatic boost control limiting the manifold pressure at the lower altitudes to 44”. The British remove this so as to get the vastly increased performance at lower altitudes thru the judicious use of over-boost. As has been mentioned before, they have had exceptionally good service out of these engines and due to its smoothness at low RPM’s, they are able to operate it so as to obtain a remarkably low fuel consumption giving them an operational range greater than any single-engine fighter they possess (the fact that the Merlin engine will not run well below 1600 prevents them from obtaining an equivalent low fuel consumption and therefore limits its usefulness for similar operations). 

34. Actual combat has proven that the aircraft can run away from anything the Germans have. Its only inferior points are that it can’t climb as well as the Me 109 and Fw 190 and that at the slower speeds of close combat it loses effectiveness of aileron control and therefore has a poor rate of roll – but its turning radius with a slight amount of flap is shorter than either of the German aircraft. 

35. In view of the British experience, it is felt that we have a plane excellently fitted and suited for long range, low altitude daylight intrusion and for a medium altitude escort fighter to accompany our medium bombers. It must be realized that an aircraft that will fulfill the conditions for a medium bombardment escort fighter might not be completely suitable for a long range intruder due to the inability on the part of the engine to run at the exceptionally low R.P.M. necessary for such long range operation. This is also assuming an operation which will allow a major portion of such missions to be made over waters where interception would be unlikely, such as from North Africa or the Mediterranean Islands to the mainland. 

36. In view of the British operation and the fact that we have an approved war emergency rating on the 1710-39 engine of 56”, it is suggested that immediate steps be taken to remove the automatic boost controls from our P-51 airplanes in this theater and that the instrument dials be marked with the proper lights. The British have operated at full throttle at sea level (72” Hg) for as much as 20 min. at a time without hurting the engines. According to them, the Allison is averaging 1500 hours between bearing failures as compared to 500 to 600 hours for the Merlin. The Allison, they have found, will drag them home even with the bearing ruined. 

NAA manufactured 310 NA-99 P-51A Mustangs in Inglewood in three production blocks: P-51A-1-NA (100), P-51A-5-NA (55), and P-51A-10-NA (155). Fifty were delivered to the RAF. These were the USAAF’s first purpose ordered versions of the P-51 Mustang for its own use. Factory floor space was at a premium and the warm Californian climate allowed these P-51As to be assembled in the open. (NAA via Peter M. Bowers

37. It is suggested that the Allison powered P-51A may lend itself better to a combination low altitude fighter-intruder and a medium bombardment escorter than will the Merlin powered P-51B due to the inherent difficulty of operating the Merlin engine at the low RPM’s necessary for a low fuel consumption. It is felt that definite engineering and flight information should be secured in these two aircraft immediately.

Charles F. Born 

Brigadier General, CSC, 

Assistant Chief of Staff, A-3.

NAA manufactured 310 NA-99 P-51A Mustangs in Inglewood in three production blocks: P-51A-1-NA (100), P-51A-5-NA (55), and P-51A-10-NA (155). Fifty were delivered to the RAF. These were the USAAF’s first purpose ordered versions of the P-51 Mustang for its own use. Factory floor space was at a premium and the warm Californian climate allowed these P-51As to be assembled in the open. (NAA via Peter M. Bowers)

Mustang Mark II 

The RAF acquired fifty of the 310 NA-99 P-51A airplanes produced by NAA at its Inglewood, California, aircraft production facility. These were designated Mustang Mark II and were assigned RAF serial numbers FR890 to FR939. The RAF praised the Mustang Mk.II to have ‘...the best all-around fighting qualities of any present American fighter’.

Mustang Mk.II Specifications

Length: 32 ft 3 in. 

Height: 12 ft 2 in. 

Wing span: 37 ft 

Wing area: 233 sq ft 

Propulsive system: one 1,470-hp Allison V-1710-81 Vee engine 

Propeller: three-bladed constant speed 10-ft-6-in.-diameter Curtiss Electric propeller 

Empty weight: 6,433 lb 

Gross weight: 8,633 lb 

Maximum speed: 390 mph at 20,000 ft 

Armament: four .50 calibre Browning M2 machine guns with 1,260 total rounds of ammunition; two hardpoints for 500 lb bombs or drop tanks

A non-camouflaged Royal Canadian Air Force (RCAF) No. 441 Squadron Mustang Mk.III showing RAF serial number HB876 with code 9G-L. In addition to the RCAF, Mk.III airplanes were also provided to the South African Air Force (SAAF) and the Royal Australian Air Force (RAAF). (John Melson)

Mustang Mark III 

The RAF put into service more Mustang Mark III airplanes than any other version. These were comprised of Inglewood, California-built, P-51Bs and Dallas, Texas-built, P-51Cs. Like the subsequent Mk.IV and Mk.IVA, the Mk.IIIs should have been designated Mk.III and Mk.IIIA but they were not so named. The RAF received 855 Mk.III airplanes as follows: FB-100 to FB124 (25); FB135 to FB399 (265); FR411 (1); FX848 to FX999 (152); FZ100 to FZ109 (10); HB821 to HB962 (142); HK944 to HK947 (4); HK955 and HK956 (2); KH421 to KH640 (220); SR406 to SR438 (33); and SR440 (1). About 60 Mk.IIIs were diverted to other RAF air bases in Canada and Australia.

Mustang MK.III Specifications

Length: 32 ft 3 in. 

Height: 13 ft 8 in. 

Wing span: 37 ft 

Wing area: 233 sq ft 

Propulsive system: one 1,380-hp Packard-built V-1650-3 Merlin engine or one 1,490-hp Packard-built V-1650-7 Merlin engine 

Propeller: four-bladed constant speed 11-ft-2-in.-diameter Hamilton Standard propeller 

Empty weight: 6,985 lb 

Gross weight: 9,800 lb 

Maximum speed: 440 mph at 30,000 ft 

Armament: four wing-mounted .50 calibre Browning M2 machine guns; two under-wing racks for bombs or drop tanks

Mustang Mark IV and IVA 

It was P-51D and P-51K Mustangs that generated the RAF Mustang Mk.IV and Mk.IVA fleet of aircraft. Both Inglewood and Dallas-built P-51Ds made up the Mk.IV while it was just the Dallas-built P-51K that made up the Mk.IVA. RAF squadrons to get these airplanes were Numbers 19, 64, 65, 112, 118, 122, 149, 154, 213, 260, 303 (Polish), 442 and 611 Squadrons.

RAF serial numbers are KH641 to KH670 (thirty Mk.IV airplanes), KH671 to KH870 (200 Mk.IVA airplanes), KM100 to KM492 (393 Mk.IVA airplanes), KM493 to KM743 (251 Mk.IV airplanes), KM744 to KM799 (fifty-six that were never delivered), TK586 and TK589 – both former USAAF P-51D-5-NA airplanes (44-13524 and 44-13332).Thus, the RAF received 876 Mk.IV and Mk.IVA total aircraft from the US under the Lend-Lease programme.

The RAF Mustang Mark IVA fleet were comprised solely of Dallas, Texas-built, P-51K airplanes. The RAF received these in 1944-1945. During the spring and summer months of 1944, RAF Mk.IV and Mk.IVA Mustangs based in Great Britain accounted for the destruction of 232 V-1 Buzz Bombs by 5 September 1944. The RAF, after VE Day, redirected deliveries of Mk.IV and Mk.IVA Mustangs to its units in India to help ward off the Japanese still fighting in the CBI. After the Second World War, a number of Mustang MK.IV and Mk.IVA aircraft continued to serve with the RAF up until May 1947 when they were superseded by more modern turbojet-powered fighters. A large number were returned to the US while other unserviceable ones were scrapped.

Mustang Mk.IV and Mk.IVA Specifications

Length: 32 ft 3 in. 

Height: 12 ft 2 in. 

Wing span: 37 ft 

Wing area: 233 sq ft 

Propulsive system: one 1,695-hp Packard-built V-1650-7 Merlin engine 

Propeller: one four-bladed constant speed 11-ft-1-in.-diameter Hamilton Standard propeller or one four-bladed 11-ft-diameter Aeroproducts propeller 

Empty weight: 7,125 lbs 

Gross weight: 12,100 lbs 

Maximum speed: 437 mph at 25,000 ft 

Armament: six wing-mounted .50 calibre Browning M2 machine guns with 12,100 total rounds of ammunition; three-to-four under-wing attachment points for bazooka tubes, bombs, rockets and drop tanks

A camouflaged Mk.III of RCAF No. 442 Squadron, RAF serial number KH668, code TY-2, with what appears to be a pilot sitting on its wing. (John Melson)

Mustang Mark V 

The Mustang Mark V designation was allocated to two lightweight Mustang prototype airplanes that were supplied to the RAF by the US War Department for evaluation purposes. One NA-105 XP-51F (43-43334) – the third of three built, was delivered; one NA-105A XP-51G (43-43336) – the second of two built, was not delivered. Respectively, these were assigned RAF serial numbers FR409 and FR410. The XP-51F was evaluated by the A&AEE at RAF Boscombe Down. Two NA-105B XP-51J lightweight Mustang airplanes were also built during this programme but neither was sent to Great Britain.

Mustang Mark X 

There were six RAF Mustang Mk.X airplanes. Only five of these, however, were modified to the Mk.X configuration as one of these, (AG518), was deemed to be too outdated to partake in this programme designed to marry the Rolls-Royce Merlin engine to the Mustang Mk.I. The Mustang Mark X programme, also known as the ‘Rolls-Royce Mustang’ programme, was the RAF variant using a Rolls-Royce Merlin engine in an experimental programme established by Rolls-Royce Limited in 1942.

In April 1942, the AFDU tested the Allison V-1710-engined Mustang at high altitudes and found it wanting, but their Commanding Officer, Wing Commander Ian Campbell-Orde, was so impressed with its manoeuvrability and low-altitude speed that he invited chief test pilot Ronald Ward ‘Ronnie’ Harker from Rolls-Royce’s Flight Test establishment to fly it. It was quickly evident that performance, although exceptional up to 15,000 feet, was inadequate at higher altitudes. This deficiency was due largely to the single-stage supercharged Allison engine, which lacked power at higher altitudes. Still, the Mustang’s advanced aerodynamics showed to its advantage as the Mustang Mark I was also 30 mph faster than a contemporary Curtiss P-40 using the same Allison powerplant. The Mustang Mark I was 30 mph faster than the Spitfire Mark VC at 5,000 feet and 35 mph faster at 15,000 feet, despite the latter having a significantly more powerful engine than the Mustang’s Allison. Harker became the strongest advocate of marrying the Merlin to the Mustang and eventually served as best man during the marriage to become known as ‘The man who put the Merlin in the Mustang.’

Two NA-105A XP-51G airplanes were built (43-43335 and 43-43336). These were originally fitted with five-bladed Rotol Airscrews propellers manufactured in Great Britain. These were electric constant speed propellers, the blades of which were made of laminated wood. These propellers did not work well with the XP-51G aircraft and were soon replaced with four-bladed props. The XP-51G airplanes were powered by special Rolls-Royce RM 14.SM Merlin engines. (San Diego Air & Space Museum via John Melson)

Rolls-Royce engineers rapidly concluded that the Mustang powered by a Merlin 61 would result in a significant improvement in performance and started converting six Mustangs to Merlin power as the Mustang Mark X. With a minimum of modification to the engine bay, the Merlin engine neatly fit into the adapted engine formers. A smooth engine cowling with a chin-type radiator was tried out in various configurations. The Merlin 65 series engine was utilised in all the prototypes as it was identical to the Merlin 66 powering the Spitfire Mark IX, allowing for a closer comparison. Due to the speed of the conversions, engines were often swapped from aircraft to aircraft as well as being replaced by newer units.

The first Mustang Mark X flight was flown by Rolls-Royce chief test pilot Ronald Thomas ‘Shep’ Shepherd on 13 October 1942 who flew AL975/G – formerly a Mustang Mark I. (The G suffix meant that a guard was to be posted when the airplane was on the ground.) Exactly one month later, another former Mustang Mark I, the second Mark X (AM208), was flown for its first time. The high-altitude performance was a major advance over the Mustang I, with one Mustang Mark X (AM208) reaching 433mph at 22,000 feet and AL975 tested at an absolute ceiling of 40,600 feet. One Air Ministry official, Sir W. R. Freeman (Chief Executive at the Ministry of Aircraft Production) lobbied vociferously for Merlin-powered Mustangs, insisting two of the experimental Mustang Mark Xs be handed over to Major General Carl A. ‘Tooey’ Spaatz for evaluation by the US 8th Air Force in Great Britain which Spaatz commanded at that time.

The pairing of the P-51 airframe and Merlin engine created the USAAF P-51B and P-51C airplanes depending on their place of manufacture whether in Inglewood, California, (P-51B), or the new plant in Dallas, Texas, (P-51C). The RAF named these models Mustang Mark III. In performance tests, the P-51B achieved 441 mph at 25,000 feet and subsequent extended range with the use of drop tanks enabled the Merlin-powered Mustang version to be introduced as a superb bomber escort.

The small fleet of Mustang Mark X airplanes included:

AG518: Used for engine installation studies, but due to a lack of guns, armour and radio equipment, it was deemed by Rolls-Royce to be ‘below’ latest production standards and not converted.

Two NA-105B XP-51J airplanes (43-76027 and 43-76028) were tested with V-1710-119 Allison engines with two-stage superchargers in the attempt to allow for better high-altitude performance. This is the first example of the XP-51J (43-76027). (San Diego Air & Space Museum via John Melson)

AM121: This aircraft arrived at the Rolls-Royce Flight Test Establishment at RAF Hucknall on 7 June 1942 and was the first to be delivered, but the last to be converted. A broader chord fin was installed but the aircraft was not slated for testing at RAF Hucknall and was sent to RAF Duxford before being loaned to the 8th Air Force at RAF Bovingdon along with AL963.

AL963: First used for performance and handling trials of the Mustang I before conversion on 2 July 1942. Its nose contours had a much sleeker appearance due to the intercooler radiator being relocated to the main radiator duct. Other changes included a small vertical tail extension and the ‘blanking’ or ‘filling’ of cowling louvers. This example was able to reach 422 mph at 22,400 feet. It was sent to the USAAF Air Technical Section at RAF Bovingdon for evaluation.

AL975/G: First used for performance and handling trials of the Mustang Mark I before conversion on 2 July 1942, flying for the first time on 13 October 1942. The aircraft was identifiable by a bulged lower engine cowling and was also fitted with a four-blade Spitfire Mark IX propeller. In testing, it achieved a top speed of 425 mph at 21,000 feet.

AM203: The third aircraft was fitted with a four-bladed, 11-foot-4-in.-diameter wooden propeller and achieved 431 mph at 21,000 feet.

AM208: The second conversion had the front radiator flap sealed permanently giving a 6-7 mph boost in speed. The same modification was subsequently made to all test aircraft.

Flying Test Bed

If ever there were an ugly Mustang, it was the highly modified Mustang Mark I sporting RAF serial number AL960. In mid-1943, Rolls-Royce proposed to re-engine the Mustang with a more powerful 2,000-plus horsepower R-R Griffon 65 located in the middle of the fuselage. It was never designated but was to be called a ‘Flying Test Bed’ or FTB. Three surplus Mustang Mark I airframes were provided to R-R by the Ministry of Air Production and these were dismantled to provide the major components for the highly modified FTB airplane. Since Mark I airframe AL960 (an NA-83) was used for the fuselage and empennage, it retained the RAF serial number. The FTB mock-up was completed sans the Griffin 65 engine and for temporary purposes a Merlin 61 was installed. The FTB was examined by representatives of the Air Ministry in early 1944 with very little enthusiasm being shown and the project was not given priority status. The airplane was never fully completed nor flown and the R-R FTB development contract was cancelled in early 1945. The ungainly mock-up was scrapped.


A rather large portion of these RAF Mustangs were employed by other air forces throughout the United Kingdom including the Royal Australian Air Force (RAAF), Royal Canadian Air Force (RCAF), Royal New Zealand Air Force (RNZAF) and the South African Air Force (SAAF). In all, the RAF operated and/or evaluated nine specific variants of the Mustang: the Mustang Mark I, Mustang Mark I (Dive Bomber), Mustang Mark IA, Mustang Mark II, Mustang Mark III, Mustang Mark IV, Mustang Mark V and the Mustang Mark X. One additional Mustang, counted within the 2,570 total delivered to the RAF, was obtained for evaluations by the A&AEE at RAF Boscombe Down. It was a P-51H-5-NA (44-64181) and was issued RAF serial number KN987. Although it was a Lightweight Mustang, it was known as a Mustang Mk.IV instead of a Mustang Mk.V like the XP-51F and XP-51J.

Royal Australian Air Force Mustangs

The Royal Australian Air Force (RAAF) employed a number of Canadian-sent P-51B and P-51C Mustang Mk. IIIs in combat action from late 1942 until VJ Day on 2 September 1945.

In addition, the Australian Government arranged for the Commonwealth Aircraft Corporation (CAC) to manufacture the P-51D under licence from NAA in the early months of 1943. The RAAF desperately needed a new fighter, and to get started, it purchased 100 unassembled P-51D-1-NA (NA-110) airplanes that were shipped to Australia by sea. They arrived in crates packed with all the required sub-assemblies to build the P-51D airplanes such as their engines, fuselages, wings, landing gear assemblies and vertical and horizontal tails.

One P-51D-5-NA Mustang was employed for developmental assessments and bore RAAF serial number A68-1001. It came from the RAF and it was used by CAC as the pattern airplane for its CA-17 assembly programme. The first CAC-assembled Mustang (A68-1), a Mustang Mk. 20, made its first flight on 29 April 1945. It was accepted by the RAAF on 4 June 1945 and the No. 1 Aircraft Performance Unit (APU) used it for further trials including armament, performance and combat manoeuvrability. (The No. 1 APU kept this particular Mustang until October 1946, after which it went into long-term storage until 1953 when it became the property of the Department of Supply at Woomera.)

Using the designation CA-17, eighty of the 100 P-51D aircraft were delivered to the RAAF with Packard-built V-1650-3 Merlin engines. These carried the RAAF serial numbers A68-1 to A68-80.

The RAAF wanted another 170 ‘improved’ Mustangs powered by the Packard-built V-1650-7 Merlin engine, but the contract was reduced to 120 fighters. These were the first all-CAC-built Mustangs (RAAF serial numbers A68-81 to A68-120). The first forty, designated CA-18, were delivered as Mustang Mk. 21s with -7 Merlin engines. Within the last batch of CA-18s, fourteen were delivered as Mustang Mk. 22s (A68-187 to A68-200) with -7 Merlin engines for photographic reconnaissance missions.

A contract for 250 additional CAC-built Mustangs designated CA-21 was cancelled. In lieu of the remaining CAC-built CA-18s and CA-21s, the RAAF procured 298 Lend-Lease P-51D and P-51K Mustangs (A68-500 to A68-583 and A68-600 to A68-813). The RAAF also accepted Mustangs for the Netherlands East Indies Air Force (NEIAF). These carried Royal Netherlands Air Force (RNAF) serial numbers N3-600 to N3-640.

None of the CAC-built Mustangs saw action in the Second World War, so RAAF Mustangs were sent to Japan as part of the occupation force after VJ Day. In early 1946, three RAAF squadrons, Numbers 76, 77 and 82, arrived in Iwakuni, Japan. Numbers 76 and 82 returned to Australia in 1949. RAAF No. 77 Squadron remained in Japan and from there played its part in the Korean War from June 1950 until April 1951 when its Mustangs were replaced by turbojet-powered Gloster Meteors.

Mustangs remained in service with a number of Citizen Air Force Squadrons until they were finally withdrawn from service in 1959.

CAC CA-18 Mustang Mk. 21 Specifications

Length: 32 ft 3 in. 

Height: 12 ft 2 in. 

Wing span: 37 ft 

Wing area: 233 sq ft 

Propulsive system: one 1,490-hp Packard-built V-1650-7 Merlin engine 

Empty weight: 7,863 lb 

Gross weight: 10,500 lb 

Maximum speed: 425 mph at 25,000 ft 

Armament: six .50 calibre Browning M2 machine guns, two 1,000-lb bombs or ten five-inch air-to-ground rockets

Four variants of CAC-built Mustangs were manufactured for the RAAF totalling 200 aircraft as follows: CA-17 Mk.20 (80); CA-18 Mk.21 (40); CA-18 Mk.23 (66); and CA-18 PR.Mk.22 (14).

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