APO 520

26 August 1943

SUBJECT:British Army Cooperation Tactical Employment of the Mustang I (P-51).
TO:Commanding General, Northwest African Air Forces, APO 650.
 (Attention:  Tactics Officer)

   1.       The following report on the Cooperation Tactical Employment of the Mustang I (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 hole cut in the plexiglass. 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, and 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 flight 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 a 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.       Specialised 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 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 neighbourhood of 90 miles for reach flight. The point 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 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.

   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. It’s 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 will fulfil 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 theatre 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.

   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.

Brigadier General, CSC,
Asst Chief of Staff, A-3.

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