The Lockheed P-38 Lightning racked up an impressive series of "firsts"—it was the first Lockheed-designed military aircraft to go into series production, it was the first twin-engined interceptor to serve with the USAAC, it was the first production fighter powered by the Allison V-1710 in-line engine, it was the first modern fighter equipped with a tricycle landing gear, it was the first American plane to use butt-jointed flush riveted external surfaces, it was the first to make extensive use of stainless steel, it was the first fighter to use a bubble canopy right from the start and it was the first fighter with speeds over 400 mph. A total of 3,899 Lockheed Lightnings, mostly P-38Gs, were built.
Lockheed was invited along with Boeing, Consolidated, Curtiss, Douglas, and Vultee to take part in a USAAC design competition X-608 for a twin-engined high-altitude interceptor. The specification called for a maximum speed of at least 360 mph at 20,000 feet and 290 mph at sea level, an endurance at full throttle of one hour at 20,000 feet, and the ability to take off and land over a 50-foot obstacle within 2200 feet.
The Lockheed design staff settled on a twin-boom design with each boom extending aft of the engine and the pilot sitting in an enclosed cockpit in a central nacelle. Each boom was to house one of the new 1150 hp Allison V-1710C twelve-cylinder liquid-cooled engine with an exhaust-driven turbosupercharger. The central nacelle contained a forward-firing armament of one cannon and four 0.50-in machine guns. Tail surfaces consisted of a fin and rudder at the end of each boom and a horizontal tailplane and elevator between the booms. At 14,800 pounds, the XP-38 weighed more than a bombed-up Bristol Blenheim I, at that time the standard British medium bomber. Fowler flaps were fitted between the ailerons and the booms and between the booms beneath the trailing edge of the wing center section.
Although the USAAC was somewhat skeptical about so radical a design, Lockheed was awarded a contract for one XP-38 prototype. Construction began in July 1938. Construction proceeded rather rapidly despite the radical features that it embodied. The XP-38 aircraft was completed in December of 1938. The early test flights turned up some problems with the wheel brakes and with vibrations of the flaps, requiring that some modifications be made to the prototype. Maximum speed was 413 mph at 20,000 feet, and an altitude of 20,000 feet could be attained in 6.5 minutes. Service ceiling was 38,000 feet. Empty weight was 11,507 lbs, gross weight was 13,964 lbs, and maximum takeoff weight was 15,416 lbs.
On April 27, 1939 a Limited Procurement Order for thirteen YP-38 service test aircraft was issued. The YP-38 was redesigned for production and had a pair of 1150 hp Allison V-1710-27 and -29 engines equipped with B-2 turbosuperchargers. Armament was revised to substitute two 0.30-in machine guns for two of the four 0.50-in machine guns, and a 37-mm Browning M9 cannon with 15 rounds was substituted for the 20-mm weapon. The 0.50 inch guns carried 200 rounds per gun and the 0.30 inch guns carried 500 rounds per gun.
Lockheed P-38 Lightning
Twenty-nine of these were delivered as P-38-LO. The P-38 had the same powerplants as the YP-38, but armament was changed to one 37-mm cannon and four 0.50-in machine guns. Armor plate and bulletproof glass was added for pilot protection, and fluorescent instrument lighting was provided for night flying.
Lockheed P-38D Lightning
The A, B and C versions of the Lightning were all consolidated into the D version so no aircraft bearing those designations were built. The P-38D differed from the P-38 in having self-sealing fuel tanks, a retractable landing light, and provision for flares. A change in tailplane incidence, together with a redistribution of elevator mass balances, increased the mechanical advantage of the elevator control, resulting in the elimination of buffeting and facilitating dive recovery. The P-38D featured a new low-pressure oxygen system, which supplanted the old high-pressure oxygen system of earlier versions. This system became standard on all subsequent production models. Normal fuel capacity remained 210 gallons, but maximum internal fuel was reduced from 390 to 340 gallons.
Lockheed P-38E Lightning
The first major production version for the USAAF was the P-38E. It differed from the D-version in having the 37-mm cannon with the 15-round magazine replaced by a 20-mm cannon with 150 rounds. The P-38E had improved instrumentation and revised hydraulic and electrical systems. It had a revised nose section with double the ammunition capacity of earlier versions. An SCR-274N radio was installed. In the middle of 1941, the Hamilton Standard Hydromatic propellers with hollow steel blades were replaced on the production line by Curtiss Electric propellers with dural blades. Early in its life the P-38 earned a reputation as a pilot killer. A terminal velocity dive in a P-38 was believed by many pilots to be a fatal maneuver. It was possible in a high- speed dive to overstress the plane while trying to pull out, and a number of P-38s lost empennages while doing such maneuvers and crashed, usually with fatal results. It was later determined that these problems were the result of the effects of compressibility. Although it was later found that ALL aircraft had problems when they operated in these speed ranges, the P-38 was a pioneer in high-speed flight and thus got a bad reputation. A total of 210 P-38Es were built.
Specifications of the P-38E Lightning
The P-38E was powered by Allison V-1710-27/29 turbosupercharged engines. Maximum speed was 395 mph at 25,000 feet. An altitude of 20,000 feet could be reached in 8 minutes, and service ceiling was 39,000 feet. Weights were 11,880 lbs empty, 14,424 lbs gross, and 15,482 lbs maximum takeoff. Armament was one 20mm cannon and four 0.50 inch machine guns.
Lockheed P-38F Lightning
The P-38F version of late 1942 was the first Lightning version that was considered fully combat-ready. It included 377 US-ordered aircraft, plus 150 planes that had originally been ordered under British and French contracts. The P-38F was powered by 1325 hp turbosupercharged Allison V-1710-49/53 engines and had the same armament as did the E-version—one 20-mm cannon and four 0.50-in machine guns. There were five separate production batches of the P-38F, differing from each other mainly in internal equipment.
The initial F-version was the P-38F-LO. 128 of these were built. The next F-version was the P-38F-1-LO, which differed from the P-38F-LO in being modified after delivery to carry a pair of drop tanks or a pair of 1000-lb bombs under the wing center sections. Each rack could also carry a Smoke Curtain Installation or a 22-inch torpedo. This version had SCR-525 and SCR-522 radio. 149 of the P-38F-1-LO version were built. The P-38F-5-LO version, of which 100 were built, was built from the onset with provision for drop tanks. It also had revised landing lights, desert equipment, identification lights, and various other minor improvements. The twenty-nine P-38F-13-LOs and the 212 P-38F-15-LOs had modified instruments and introduced combat flaps which could be rapidly extended to 8 degrees during maneuvers to tighten the turning radius. Finally Twenty P-38F-1-LO airframes with 1325 hp V-1710-49/53 engines were completed as F-4A-1-LO unarmed photo-reconnaissance aircraft with four K-17 cameras in a modified nose.
Specifications of the P-38F
The P-38F was powered by 1325 hp turbosupercharged Allison V-1710-49/53 engines and had the same armament as did the E-version—one 20-mm cannon and four 0.50-in machine guns. The P-38F had an empty weight was 12,264 lbs, gross weight was 15,900 lbs, and maximum takeoff weight was 18,000 pounds. Maximum speed was 395 mph at 25,000 feet. An altitude of 20,000 feet could be reached in 8.8 minutes.
Lockheed P-38G Lightning
The P-38G began to roll off the production lines in June of 1942. It was basically similar to the P-38F apart from a change to the Allison V-1710-51/55 (F10) engine with increased boost ratings and offering 1325 hp for takeoff. However, the engine was limited to 1150 hp at 27,000 feet due to inadequate cooling. In addition, the P-38G carried a SCR-274N radio and A-9 oxygen equipment. The P-38G had a loaded weight some 200 pounds less than that of the P-38F, and was the most widely-built version of the early Lightnings. 3082 P-38Gs had been delivered by March 1944. 181 of these had been completed as F-5A photo reconnaissance aircraft and another 200 had been completed as F-5Bs with camera installations similar to that of the F-5A-10-LO. One F-5A-10-LO was modified as an experimental two-seat reconnaissance aircraft under the designation XF-5D-LO.
Specification of P-38G-1-LO
Maximum speed: 345 mph at 5000 feet, 360 mph at 10,000 feet, 400 mph at 25,000 feet. 850 miles range on internal fuel at cruising speed of 219 mph at 10,000 feet. 1750 miles range at 211 mph at 10,000 feet with two 125 Imp. gall. drop tanks. Climb to 10,000 feet in 3.7 minutes, climb to 20,000 feet in 8.5 minutes. Service ceiling of 39,000 feet. Weights were 12,200 lbs empty, 15,800 lbs normal loaded, 19,800 lbs maximum loaded. Dimensions were wingspan 52 feet 0 inches, length 37 feet 10 inches, height 9 feet 10 inches, wing area 327.5 square feet. Armed with one 20-mm Hispano M1 cannon with 150 rounds and four 0.50-in Colt-Browning MG 53-2 machine guns with 500 rounds per gun. Could carry two 325, 500, or 1000-lb bombs.
Lockheed XP-38H Lightning
The groups of P-38G fighters sent to Russia had proved the type was effective but was limited by an inadequate and unreliable engine installation. In addition, there was some concern that all American aircraft flying in Russia were dependent on the same general type of engine. This would be remedied to some extent when the P-47 Thunderbolt arrived in quantity but that only went to show the superiority of air-cooled radials over liquid-cooled engines. Accordingly, Lockheed were asked to investigate the modification of the Lightning to use a radial engine. Originally Lockheed envisaged using a R-2600 but this proved unsuitable for turbocharging so Lockheed made “the big jump” the using the R-2800. This required such a major redesign that the XP-38H was redesignated the XP-49.