By Joe Baugher
Lockheed was invited, along with Boeing, Consolidated, Curtiss, Douglas, and Vultee to take part in USAAC's Design Competition X-608 for a twin-engine, high-altitude interceptor. Specification called for a top speed of at least 360 mph at 20,000' and 290 mph at sea level, an endurance at full throttle of one hour at 20,000', and the ability to take-off and land over a 50' obstacle within 2,200'.
The Lockheed design staff was headed by Hall Hibbard. Working with Hibbard was the soon-to-be famous Clarence "Kelly" Johnson. After studying many different designs, the pair settled on a twin-boom design with the pilot in a central nacelle. The booms would each house a 12-cylinder 1150hp Allison V-1710C with an exhaust-driven turbo-supercharger!51;the liquid-cooled Allison had just completed a 150-hour type-approval test at 1000 hp.
The nacelle contained a forward-firing 20mm cannon and four .50 machine guns, armament quite heavy for its time. One advantage of the twin-boom design was a nacelle, unhampered by synchronizing mechanisms, that could deliver parallel streams of fire up to 3000'. It was estimated that the twin-tail assembly would increase the effective aspect ratio of the tailplane by the endplate effect, providing stability over a large c/g range. Trailing-edge Fowler flaps were inboard of the ailerons and between the booms.
As their Model 22-64-01, Lockheed promised a top speed of over 400 mph. Although the AAC was somewhat skeptical about so radical a design, Model 22 won Design Competition X-608 and, on June 23, 1937, Lockheed received a contract for one unarmed XP-38 prototype [37-457]. Construction began in July 1938 and proceeded rather rapidly despite the radical features that it embodied. Few problems were presented by the installation of the Allison V-1710-11/15 (C9)s, each with a General Electric B-1 turbo-supercharger. To combat torque, the propellers rotated inwardly in opposite directionsa special version of the Allison had a left-hand rotating propeller shaft.
The XP-38 was completed in Dec 1938 and, on the last day of the year was stripped down, covered with canvas, and loaded onto three trucks. In great secrecy the convoy was escorted by police to March Field, where AAC Project Officer Lt Benjamin Kelsey was to do flight testing. However, on the very first ground run, wheel brakes failed and the plane ended up in a ditch. Kelsey finally got airborne on Jan 27, 1939. Early test flights disclosed some problems with the brakes and vibrations of the flaps, requiring modifications be made to the prototype. Maximum speed was 413 mph at 20,000', an altitude reached in 6.5 minutesservice ceiling was 38,000'. Empty weight was 11,507#, gross weight 13,964#, max take-off weight 15,416#.
Reaction was highly favorable in spite of the problems encountered on its first few flights, and it was decided to try for a record transcontinental flight before delivering the ship to Wright Field OH. At daybreak on Feb 11, 1939, Kelsey departed for Mitchel Field NY, with refuelling stops at Amarillo and Wright Field, but as Kelsey was coming in for a landing at Mitchell, the XP-38 lost powerl Field and crashed on a golf course just short of the runway. Kelsey was unhurt, but the XP-38 was a total loss.
The Lockheed P-38 racked up an impressive series of "firsts" ... it was the first Lockheed-designed military aircraft to go into series production, the first twin-engine interceptor in the USAAC and the first US twin-boom fighter to go into production, the first production fighter powered by the Allison inline V-1710, the first modern fighter with a tricycle gear, the first American plane to use butt-jointed flush-riveted external surfaces, the first to make extensive use of stainless steel, the first fighter designed with a bubble canopy, the first fighter with speeds over 400 mph, the first AAF fighter to shoot down a German aircraft, it was the first AAF fighter to carry out an escort mission to Berlin, it was the first AAF plane to land in Japan after that country had surrendered [ed: actually two days prior to thatSEE Tice Gets the Sword], the heaviest US single-seat fighter of WW2, the only American fighter in production both at the beginning and end of WW2, and it accounted for more Japanese aircraft destroyed in combat than any other US fighter. A total of 10,037 Lockheed Lightnings were built.
Even before YP-38s had been built, on Sep 20, 1939 the Army placed an order for 66 P-38 fighters. 29 of those were delivered as P-38 (company Model 222-62-02) [40-744/761, 763/773] with the same powerplants as YP-38, but armament was changed to one 37mm cannon and four .50 machine guns. Armor plate and bulletproof glass was added for pilot protection, and fluorescent instrument lighting for night flying.
P-38 [40-744] was later modified to study the effects on flight crews of asymmetric cockpit locations. Superchargers were removed, and the space in the port boom housed a cockpit for a flight surgeon.
Despite of the loss of XP-38, the Lightning had shown its true potential. On Apr 27, 1939 a Limited Procurement Order for 13 YP-38 service test aircraft was issued [39-689/701]. Lockheed's designation was Model 122-62-02.
The YP-38 was upgraded for production with a pair of 1150hp Allison V-1710-27/-29 (F2R/F2L) engines with B-2 turbos-uperchargers and spur reduction gearing rather than the former epicyclic type of gearing, which caused the engine's thrust line to be raised. Propellers changed to outward-rotating rather than inward-rotating as on the XP-38. The chin-mounted lip intake under the prop spinner was replaced by a pair of cooling intakes. Enlarged coolant radiators were adopted on both sides of the tail booms.
Armament was revised to two .30 and two .50 machine guns, and a 37mm Browning M9 cannon with 15 rounds. The .50 guns each carried 200 rpg, and the .30 guns 500 rpg each. One or two YP-38s were seen with prominent gun enclosure tubes protecting the two .50s and flush plates covering the other gun ports, but in reality most YPs were flown without guns installed. At 14,348#, its structural redesign made it lighter than the overweight XP-38.
The first YP-38 flew on Sep 16, 1940 with Marshall Headle at the controls. In Mar 1940 the Army received its first one for service trials, but production lagged seriously behind schedule and all 13 were not completed until June 1941. Maximum speed was 405 mph at 10,000', climb to 20,000' took only six minutes. Normal range was 650 miles, and weights were 11,171# empty, 13,500# gross, and 14,348# maximum take-off.
During trials the YP-38s suffered severe tail buffeting in high-speed dives, making pull-out difficult. On Nov 4, 1941 the tail booms of [39-689] came off during a dive, and test pilot Ralph Virden was killed. It was initially falsely diagnosed as elevator flutter, and a set of external mass balances were added above and below the elevator. The problem was later solved by adding large wing-root fillets at the points where the wings joined the fuselage, which had to be done very carefullya loose fit would severely impair flight characteristics.
A change order to the initial contract provided for the completion of one P-38, redesignated XP-38A, equipped with a pressurized cockpit [40-762]. To offset the extra weight of the cockpit, the 37mm cannon was to be replaced by a 20-mm unit, but no armament was actually fitted to prototype. Manufacturer trials were performed between May and Dec 1942, and the XP-38A was accepted by the AAF at the end of that year. Much of the information gained on the XP-38A project was later used in the XP-49 design.
Based on combat reports from Europe in the spring and early summer of 1941, the Combat Command and Air Materiel Command decreed that all aircraft in production incorporate certain items to make them "combat capable". Among these were self-sealing fuel tanks, no magnesium flares, low-pressure oxygen system, improved armor protection, and provision for bullet-proof glass. The AAF specified that all aircraft with those capabilities be given a "D" suffix. Beginning in Aug 1941, all production P-38s bore the new designation P-38D. Hence there never was a P-38B or C.
Lockheed P-38D Lightning
The result of AAF's specification was that the remainders of the initial order for 66 P-38s were completed as P-38Ds, but the model designation remained 222-62-02.
The P-38D differed from the P-38 in having self-sealing fuel tanks, retractable landing light, and a provision for flares. A change in tailplane incidence, together with a redistribution of the elevator mass balances, increased mechanical advantage of the elevator contro to eliminate buffeting and facilitate dive recovery. It also featured a new low-pressure oxygen system to supplant the old high-pressure one. Those features became standard on all subsequent production models. Normal fuel capacity remained 210 gallons, but maximum internal fuel was reduced from 390 to 340 gallons.
Top speed was 390 mph at 25,000', and 20,000' could be reached in 8 minutes. Service ceiling was 39,000'. The first P-38Ds began to reach AAF units in August 1941.
At one time, early on, the AAF considered naming the P-38 "Atlanta." However, P-38D and subsequent versions were officially christened "Lightning."
Changes were taking place at such a rapid rate that even the those introduced on the P-38D did not really make it combat-ready. In 1942 the P-38 and P-38D were redesignated RP-38 and RP-38D, the prefix meaning "Restricted to non-combat roles"they were to be used only as combat trainers.
P-38s, RP-38s, and some P-38Ds from Selfridge Field were participants in the Sept 1941 Army-Navy joint maneuvers in Louisiana, but few of them actually had guns. By the time of Pearl Harbor, there were only 69 P-38 and P-38D fighters on strength.
POP: 36 P-38D [40-774/809].
OK, now let's move on to Lockheed P-38E.
-- The American Fighter, Enzo Angellucci & Peter Bowers (Orion Books 1987)
-- Famous Fighters of the Second World War, William Green, Doubleday, 1967
-- Lockheed Aircraft Since 1913, Rene J. Francillon, Naval Institute Press, 1987
-- Lockheed P-38, Profile Publications, 1965
-- Lockheed P-38 Lightning: The Definitive Story, Warren M Bodie, Widewings, 1991
-- United States Military Aircraft Since 1909, Swanborough & Bowers (Smithsonian 1989)
-- War Planes of the Second World War, William Green, Doubleday, 1964
-- Wings of the Weird and Wonderful, Eric Brown, Airlife, 1985