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.
Production of the P-38G was divided across six blocks. There were 708 US-ordered Model 222-68-12 aircraft. 80 of these were P-38G-1-LOs which were generally similar to the P-38F-15-LOs but with the new engines, improved oxygen equipment and more reliable radios. Twelve of them were P-38G-3-LOs with B-13 superchargers. 68 were P-38G-5-LOs with revised instrumentation and 548 were P-38G-10-LOs which combined the improvements introduced in the two previous blocks with winterization equipment, provision for carrying 1600 lb bombs underneath the wing center section, or a triple cluster of 4.5-inch rocket launchers on each side of the central nacelle. The 374 Model 322-68-19s (174 P-38G-13-LOs, equivalent to the P-38G-3-LO and 200 P-38G-15-LOs, corresponding to the P-38G-5-LO) came from the cancelled British contract for Lightning IIs which was taken over by the USAAF.
Unarmed photographic reconnaissance versions of the P-38G were also produced under the designation F-5A. A single F-5A-2-LO (model 222-62-16) was completed by modifying a P-38E airframe (41-2157) by installing V-1719-21/29 engines. All of the other F-5As (Model 222-68-16) had P-38G airframes and 1325 hp V-1710-51/55 engines. Twenty F-5A-1-LOs, twenty F-5A-3-LOs, and 140 F-5A-10-LOs had the same modifications as P-38G variants with corresponding block numbers, and came off the production line in parallel with their fighter counterparts. All were unarmed and carried five cameras.
One F-5A-10-LO (Ser No 42-12975) was modified as an experimental two-seat reconnaissance aircraft under the designation XF-5D-LO. The camera operator was located in a glazed nose compartment with two forward-firing 0.50-in machine guns. Three K-17 cameras were installed, one underneath the nose and one in each tail boom.
One P-38G-5-LO (42-12866) was used as a testbed for the proposed XP-49 armament (two 20-mm cannon and four 0.50-in machine guns). The USAAF also undertook at Wright Field preliminary design for a proposed derivative of the P-38G which was to have carried a 75-mm cannon in a revised and enlarged central nacelle. However, this concept never got past the initial design stage.
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. 1082 P-38Gs had been delivered by March of 1943. 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 but with engines and airframe identical to those of the later P-38J-5-LO. One F-5A-10-LO (Ser No 42-12975) 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.
Serials for the F-5A/P-38G production run were as follows:
41-2157 Lockheed F-5A-2-LO Lightning 42-12667/12686 Lockheed F-5A-1-LO Lightning 42-12687/12766 Lockheed P-38G-1-LO Lightning 42-12767/12786 Lockheed F-5A-3-LO Lightning 42-12787/12798 Lockheed P-38G-3-LO Lightning 42-12799/12866 Lockheed P-38G-5-LO Lightning 42-12870/12966 Lockheed P-38G-10-LO Lightning 42-12967/12986 Lockheed F-5A-10-LO Lightning 42-12987/13066 Lockheed P-38G-10-LO Lightning 42-13067/13126 Lockheed F-5A-10-LO Lightning 42-13127/13266 Lockheed P-38G-10-LO Lightning 42-13267/13326 Lockheed F-5A-10-LO Lightning 42-13327/13557 Lockheed P-38G-10-LO Lightning 43-2185/2358 Lockheed P-38G-13-LO Lightning 43-2359/2558 Lockheed P-38G-15-LO Lightning