The first major production version for the USAAF was the P-38E-LO series (company designation Model 222-62-09). 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. 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. Serials of the USAAF P-38Es were: 41-1983/2097, 41-2100/2120, 41-2172, 41-2219, and 41-2221/2292. A total of 210 P-38Es were built.
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.
The most obvious effect of high speeds was the onset of tail flutter, which was at first believed to be caused by turbulence from the wing. The eventual flutter correction worked out by "Kelley" Johnson involved a change of incidence of the entire empennage from -1 deg 15 minutes to 0 degrees 0 minutes and the addition of new fillets at the fuselage-wing leading edge junction.
The P-38E was still not yet considered combat-ready, and most P-38Es were redesignated RP-38Es while others were used for various tests. 41-1983 was used to test several features which later ended up being used in the P-38J and P-38K versions. Some P-38Es were modified by Lockheed to carry drop tanks as developed for the P-38F-1-LO and later versions.
One modified P-38E deserves special note. During the spring of 1942, the rapidity of the Japanese advance caught everyone by surprise, and the USAAF became concerned with being able to ship its aircraft to the far reaches of the Southwest Pacific area. One idea to improve the ease at which P-38s could be ferried to combat units in the Pacific islands was to equip these fighters with twin floats under the center section. The retractable wheeled undercarriage would be retained, and the floats would be removed before combat operations from forward air bases were undertaken. However, the success of the scheme demanded that a way be found to keep the tailplane free from spray. As an experiment, P-38E Ser No 41-1986 was fitted with lengthened tail booms, its fins and rudders were recontoured and its tailplane was raised nearly three feet above its normal position. In addition, an engineer/observer's seat was installed aft of the cockpit in place of some of the radio equipment. 41-1986 was only flown as a landplane, the proposed twin floats never being fitted. In the event, such floatplane conversions proved to be unnecessary, since by the end of 1942 the US Navy was fully able to provide adequate shipping for aircraft and materiel sent to the Southwest Pacific.
P-38E Ser No 41-2048 was converted in 1942 as a two-seater with an elongated central nacelle extending aft of the wing trailing edge. This aircraft was intended as a research vehicle to find ways of reducing drag. It was the only P-38 to have have a full dual set of flight controls. Later in the war, this experimental aircraft was fitted with enlarged laminar-flow wing sections just outboard of the engine booms, complete with slots and boundary layer control by means of exhaust bleed air.
One P-38E (serial number unknown) was used in 1942 at Orlando to
demonstrate the feasibility of towing a Waco CG-4A glider. A proposal
was made to modify Lightnings to tow "trains" of up to three of these
troop-carrying gliders, but nothing ever came of this idea.