6 March 1943

          1.    OBJECT:

                 To determine the relative tactical value of the P-38F type aircraft for combat service.

          2.    INTRODUCTION:

                 This test was initiated by a letter from the Director of Military Requirements, Headquarters Army Air Forces, Washington, D.C., dated 9 April 1942, to the Commanding Officer, Proving Ground Command, Eglin Field, Florida, concerning the testing of aircraft to determine their operational suitability. The test was started August 7, 1942, and was terminated January 26, 1943.

                 a.    Description.    The articles tested were the standard P-38F type airplanes, A.C. Serial Numbers 41-7536 and 41-7612. The P-38F is a tricycle geared; single-seated, monoplane, powered with two (2) twelve (12) cylinder turbo supercharged Allison engines, models V-1710-49 (R.H.) and V-1710-53 (L.H.), which turn propellers in opposite directions. The length is thirty-seven (37) feet, nine and five-sixteenths (9-5/16ths) inches; height nine (9) feet, nine and three-fourths (9-3/4ths) inches, and the span fifty-two (52) feet, zero (0) inches. It is equipped with tacks to carry two (2) external droppable gas tanks of normal load of one-hundred-fifty-five (155) gallons each, or two (2) with a capacity of three-hundred (300) gallons each, if desired. In normal flight operations with internal fuel tanks full (three-hundred (300) gallons of gas), two-thousand rounds of .50 caliber ammunition, and one-hundred-fifty (150) rounds of 20mm; the gross weight is fifteen-thousand-eight-hundred (15,800) pounds. The armament consists of four (4) free firing .50 caliber machine guns and one (1) free firing 20mm cannon situated in the nose.

          3.    Conclusions:

                 It is concluded that:

                 a.    For a general combination of climb, range, endurance, speed, altitude and fire power, the P-38F is the best production line fighter tested to date at this station. Types tested include the P-47, P-51, P-40F and P-39D-1.

                 b.    The allowable maximum diving speed is not as great as desired for combat operations.

                 c.    At speeds above allowable diving speeds especially over twenty-thousand (20,000) feet, violent vibrations from tail buffeting are experienced.

                 d.    The maintenance difficulties experienced were greater than with any other standard type of American fighter.

                 e.    The subject aircraft is easy to fly. However, a longer period of time will be required for a pilot to become familiar with the operations and maximum performances of the aircraft than is required for a normal single engine fighter.

                 f.    The cockpit installations are crowded and not arranged in a specific orderly fashion.

                 g.    While the rate of climb is superior to all other types tested to date, this is not as great as required, especially below twenty-thousand (20,000) feet, and all excess weight in the structure and installations not vital to combat operations should be reduced or eliminated whenever possible.

                 h.    Cooling capacity of the intercooler is not sufficient to allow maximum horsepower to be extracted from the engine at altitude.

                 i.    The guns will not feed properly during maneuvers which create a pull of greater than 3-1/2 G’s.

          4.    RECOMMENDATIONS:

                 It is recommended that:

                 a.    Steps be taken to eliminate tail buffeting, and flight restrictions be retained until the correction is accomplished.

                 b.    Suitable means of maintaining cockpit heat at altitude be installed. (Cockpit heater on P-39NO is best seen to date.)

                 c.    Continued efforts be made to increase rate of climb and level high speed.

                 d.    Automatic shutter control of coolant and oil temperature be installed.

                 e.    One (1) guns switch be installed for all guns.

                 f.    The generators and battery switch be incorporated with the master switch and the booster pump’s switch incorporated with the individual engine switches.

                 g.    The rate of aileron roll be increased.

                 h.    The case ejection chute control be removed from the cockpit.

                 i.    Elevator trim be moved to rear nearer the pilot for more accessibility.

                 j.    The offset control be replaced by a straight control column in the middle of the cockpit, if possible. If not, the control column be reduced to a minimum safe size to increase the visibility of the instrument panel and save space in the cockpit.

                 k.    Until the automatic turbo governor is installed, a turbo tachometer be added to the instrument panel. This should be done on future types which will have intercoolers of sufficient cooling ability to allow maximum to be extracted.

                 l.    The energizing and starter switches be placed next to the main motor switches. Also all other switches that have to be used either for starting the engines or during take-offs be grouped together. These switches should be placed in a horizontal row, “off” when down and “on” when up. A drop bar should be placed below this so all switches could be turned on when the bar is lifted, after which the bar will drop back down.

                 m.    Provision be made for sufficient intercooling to permit maximum horsepower to be extracted from the engines at all altitudes up to the service ceiling.

                 n.    One (1) button on front of wheel be provided to fire 20mm cannon and machine guns, eliminating machine gun button and retaining only safety switch.

                 o.    The toggle switch type of primer (Stromberg Electric Priming Valve-T.O. – 03-10BA-25) be installed for ease and speed of operation in interception work.

                 p.    The starters be of such a type that both engines may be started at the same time for interception work.

                 q.    The top glass of the canopy be redesigned so that the shell will extend four (4) inches lower, thus putting the metal strip where the new canopy joins the windows below level of pilot’s eyes, instead of level with them as is now the case.

                 r.    Only one (1) landing light of a stationary type be installed on the leading edge of the left wing.

                 s.    The gun sight be of the type which will accommodate a 100 mil circle, permit bulb change in flight and reflection adjustment for low level bombing.

                 t.    As soon as the .50 caliber machine gun installations are corrected so they fire in more than a 3.5 G turn, that the gun chargers be eliminated from the cockpit.

                 u.    The front wind screen be made of bulletproof glass.

                 v.    Paddle blade propellers be incorporated in the P-38 design to improve climbing capabilities.

                 w.    A gun sight be installed that will allow the 161 mil view over the nose to be used in deflection shooting.

          5.    RECORD OF TEST:

                 This test was conducted pursuant to the “Program for testing the Tactical Suitability of Service Aircraft,” this headquarters, dated 9 July 1942, a copy of which is attached as Inclosure No. 1.

          6.    DISCUSSION:

                 a.    Performance.

(1)    Speed (See Inclosure No. 2).
(2)    Rate of Climb (See Inclosure No. 2).
(3)    Range (See Inclosure No. 2).
(4)    Maneuverability: The subject aircraft was flown in mock combat against P-39D, P-40F, P-47C-1, and P-51 types of aircraft and the following results were obtained:
(a)    The subject aircraft could outclimb all other types used in the test.
(b)    The P-47C-1 was faster at all altitudes, and the P-40F and F-51 were faster up to fifteen-thousand (15,000) feet. The P-39D was considerably slower.
(c)    Against the P-39D, P-51, and the P-40F, the P-38F had a longer radius of turn below twelve-thousand (12,000) feet. From twelve-thousand (12,000) feet to approximately fifteen-thousand (15,000) feet, the radius was almost the same, and from fifteen-thousand (15,000) feet on up, the P-38F had a equal or shorter radius of turn. In the initial turn, due to the slowness of aileron roll of the P-38F, the other types could roll into a turn faster and close up the circle rapidly before the P-38F would reach its maximum radius of turn. It would then take the P-38F sometime, if ever, to overcome this initial disadvantage. The P-38F’s best maneuver against all types tested was to climb rapidly out of range and then turn and commence the combat from a superior altitude. Once gaining this altitude it should retain it, making passes and climbing again rapidly. Knowledge of the local enemy fighter performance will dictate the tactics to be used by the P-38F in the combat zone. It is doubtful if this aircraft will meet in combat any type of enemy aircraft in which close-in fighting will be its best offensive action.
(5)    Ceiling: The operational ceiling was approximately thirty-thousand (30,000) feet and the service ceiling approximately thirty-eight-thousand (38,000) feet, due to engine coolant and carburetor air temperatures becoming excessive.

                 b.    Flying Characteristics.

                        The subject aircraft is simple and pleasant to fly. However, the number of instruments and controls will give a new pilot the feeling that he is flying a complicated aircraft. The cockpit drill should be stressed and the inexperienced pilot should spend twice the normal time of sitting in the cockpit and studying the controls and instruments. If possible, a new pilot should spend a minimum of thirty (30) hours in a single-engine fighter to build up his confidence and then several familiarization flights as a co-pilot in a twin-engine ship to help his twin-engine technique. Taxiing single-engine operation, use of throttle and use of cross-over feet should be covered on these flights. An experienced pilot should have no trouble with a P-38F aircraft. However, a longer period of transition will be required before the pilot heels that he can get the maximum performance from the aircraft. The aircraft is quite stable at lower altitudes, but at higher altitudes it has a slight lateral instability. While flying at high altitude at high speeds, a tail buffeting is felt, and if a tight turn is then executed, the buffeting becomes objectionable only in very tight turns.

(1)    Due to tail buffeting, the maximum allowable diving speed is four hundred (400) miles per hour indicated air speed at seal level, which is not as great as desired. This decreases with altitude, and the pilots should be familiar with limitations. The aircraft is difficult to stall with power on and will approach almost a vertical position before stalling. In a power-off stall, the aircraft falls forward and recovers easily. Due to restriction, no spins, no spins were attempted.
(2)    Little torque is noticed in the aircraft in changing speeds and going from a dive into a climb. The temperature of the oil and prestone changes rapidly in dives and climbs requiring constant changing of both shutter positions. (Automatic shutter control was recommended.)
(3)    It is not possible to climb the P-38F to thirty-five-thousand (35,000) feet at constant maximum allowable horsepower without exceeding allowable carburetor air temperatures. Constant exceeding of these temperatures will cause detonations and possible engine failure.
(4)    The landing glide is good and the aircraft lands easily; however, due to its weight the plane settles very rapidly if landed high.

                 c.    Cockpit Arrangement.

                        The cockpit is crowded and the switches and controls are arranged in a disorderly fashion. This is due in part to the large offset control column and the wheel which prevents the right side of the cockpit from being used for any control handles or switches. This large control column also hides the switch panel at the bottom of the instrument panel. The oil cooler control switches are too hard to reach for switches that have to be used numerous times during flight and they require the pilot to keep his head in the cockpit during the time the oil shutters are changing positions. (automatic coolers are recommended.) The trim controls are separated widely in the cockpit. (An ideal arrangement of trim controls may be seen in a P-51.)

                 d.    Pilot Comfort.

                        In temperate weather the cockpit at lower altitudes is warm enough, but in climbing to altitude the cockpit becomes very cold and remains that way. This will require pilots flying in tropical climates to wear heavy flying clothes when going on normal missions that may require altitude flying.

                 e.    Armament.

(1)    The armament combination, which consists of the free firing four (4) .50 caliber machine guns and one (1) 20mm cannon, is considered satisfactory for fire power.
(a)    It is concluded that, on the whole, the armament installation on the P-38F airplane is satisfactory, with the exception of the following conditions which were unsatisfactory:
(1)    The blast tube of the lower left .50 caliber gun is unsatisfactory.
(2)    The guns will not feed properly during maneuvers which create a pull of more than 3-1/2 G.
(3)    The effort required to operate the gun chargers in the air is too great.
(4)    The system of switches and triggers for the firing circuit is tool complicated.
(5)    The field of view is unsatisfactory forward, due to gun sight and armor plate glass.
(6)    The present sight reticle pattern is unsatisfactory.
(7)    The blast tube cover plate of the 20mm cannon is unsatisfactory.
(8)    When fires at night the flash from the guns is unsatisfactory.
(2)    The position of the free firing guns in the nose so close to the line of sight is considered the best of all standard American fighter planes. Fire should be more accurate at longer ranges, and center of impact will remain practically the same at all ranges for the four (4) .50 caliber guns. (See Inclosure No. 4 for recommended gun harmonization.)

                 f.    Armor.

                       See Inclosure No. 3 for armor diagram.

                 g.    Vulnerability of Vital Installations.

                       No test on vulnerability of P-38F’s was made at this station.

                 h.    Gun Platform.

(1)    The plane offers a stable gun platform at all angles and speeds, except fro tail flutter. Little effect is noticed in firing of the guns, although a small amount of smoke is blown back into the cockpit during the firing.
(2)    The vision through the sight is 58 mils down. However, looking around the sight the angle from the line of sight down the nose is 161 mils. This calls for a different type sight.

                 i.    Visibility.

                       The visibility over nose is satisfactory for deflection shooting, but the armor plate window and gun sight obstruct the forward vision for search.

(1)    To the sides the view downward is limited definitely by the position of the wings and engine, and searching below will have to be accomplished by banking the airplane from side to side. The search view on both sides is greatly obstructed by metal strips where canopy joins the window. The view to the rear is limited by boom and rudders, and rear armor plate.
(2)    A slightly stepped down position will be required for formation flying due to postion of engine. A looser formation will be required than for single-engine fighters due to two (2) engines and to lag, and the overspeeding of turbos.

                 j.    Night Flying.

(1)    The aircraft is satisfactory for night flying. Landings and take-offs are simplified by the view over nose and level position of aircraft while on ground.
(2)    The flash from guns being fired cause a short period of blindness to the pilot. Suitable flash hiders will be required if the P-38F is used for night fighting.
(3)    The turbo, when hot, can be seen for approximately two-thousand (2,000) feet in the air.

                 k.    Instrument Flying.

                       The aircraft is considered satisfactory for instrument flying. Once trimmed up, pilots should be able to make long flights on instruments.

                 l.    Speed of Servicing.

                       Crew of four (4) armorers, one (1) crew chief, and one (1) helper; Time – minimum ten (10) minutes. This was done with a pressure gas tank. In the field with hand pump for gasoline and with unknown amount of ammunition to be loaded, it is believe the time to service will be in the neighborhood of thirty (30) minutes.

                 m.    Maintenance.

(1)    It has been reported that carburetor temperatures have been running too high. Intercoolers are easily subjected to damage of the floating baffles which tend to distort and bend out of alignment due to back firing or sudden acceleration of engine.
(2)    Exhaust cooling shrouds are unsatisfactory due to the constant trouble encountered in maintaining them. It is believed that the material is not of sufficient strength to withstand the intense hear applied to then which results in their disintegrating and cracking.
(3)    Considerable time is being lost due to difficulties in removing inspection panels throughout the airplane structure. It is believed that a great percentage of these panels could be installed with dzus fasteners which could then be removed in a matter of seconds and not hours. All panels now installed with Phillips head screws have a tendency to freeze making their removal impossible without the aid of an easy-out tool.
(4)    It is recommended that the voltage regulator and battery relay switch be relocated to a position where it can be more easily and quickly gotten to for inspection and repair. It is also recommended that a small dzus panel be installed for this electrical control if relocation of voltage and battery relay is possible.
(5)    It is recommended that a safety catch be installed on the fuselage gun and ammunition door to eliminate possible danger of props striking door if accidentally fastened when engines are started.
(6)    It is recommended that an inspection panel or door be installed directly over battery in left boom so that ground crews can inspect and service battery without removing it entirely from airplane.
(7)    Pilot’s seat is unsatisfactory as far as its removal and installation. Ground crews have found that many man hours are lost when seat has to be remove. It is believed that an installation similar to the airplane type P-36 installation could be used; the seat can then be removed in a matter of minutes.
(8)    Inspection plate be installed to allow inspection in rear of instrument panels. At present there are ninety-six (96) Phillips’ head screws that have to be removed to perform inspections or maintenance work on instruments.
(9)    A study be made of the P-38 fuel system to determine a method of eliminating the siphoning of gasoline from gas tanks while in flight when descending from altitudes due to change of pressure; this is considered a dangerous condition and a considerable loss of fuel might results.
(10)    Oil and Coolant lines installed in engine compartment are not sufficiently secured. It is recommended that more securing clamps be installed to hold vibrations of these lines to a minimum.
(11)    Pilots have reported that the heating of the cockpit is unsatisfactory. Inspection of the heating system revealed that the heating blast ducts are too small to be sufficient in heating the cockpit satisfactorily. It is recommended that the ducts be made of a larger diameter to secure more heating volume, and an attempt be made to make the cockpit airtight.

          7.    INCLOSURES:

                 Inclosure No. 1 - Test Program.
                 Inclosure No. 2 - Charts.
                 Inclosure No. 3 - Armor Diagram.
                 Inclosure No. 4 - Bore Sighting Diagrams.

Main    P-38 Performance