Profile-P-38 Lightning

In the UK, the P-38 wings initially provided long range escort for the 8th Air Force, in that critical phase of the daylight bombing offensive, when Luftwaffe strength was at its best, and US bomber losses began to reach unsustainable proportions. The presence of the P-38 allowed the offensive to continue at a point, where it may have been scaled down due to disproportionate attrition.

The Lockheed P-38 was a complex aircraft, using innovative technology, which experienced a painful and protracted development phaseand in the end, was denied the credit which it deserved for the importance of its role. This becomes all the more apparent upon closer examination.

Early Development – the XP-38 and YP-38

The story of the Lightning actually began in the mid ‘thirties, in a United States still very much isolationist, and in an acquisition climate dominated by fierce rivalry between the Army and Navy, who fought bitterly over what little money was spent on aircraft procurement. There was only mediocre support for developing new technology, either from the politicians who saw little payoff in buying toys for the boys, as with senior military officers, most of whom were still thinking in terms of 1920s technology and refighting WWI. This now absurd mindset decreed that a single seat fighter was to be restricted to agun/ammunition load of 5001b and a powerplant well below l,000hp. At this time, two forward junior officers, Lt Benjamin Kelsey and Lt Gordon Saville, realised that a :fighter with an air-air weapon load of 1,0001b and at least l,500hp was both feasible and necessary to defeat the coming generation of long range bombers.

To beat the bureaucracy and circumvent the rules restricting what could be done with :fighters, Kelsey and Saville invented the interceptor category and convinced the Army Air Corps to invite submissions on such a design. The February, 1937 C ircular Proposal X-608 (ie RFP) for a single and a twin engined :fighter called for the use of the very new Allison V-1710 inline liquid cooled V-12, equipped with the new GE turbocharger for high altitude performance, and for the use of very heavy armament including cannon. Tricycle undercarriage was specified as preferred and large internal fuel capacity was mandatory, to circumvent_ an administratively imposed ban on the use of drop tanks by fighters.

The single engined fighter contract was won by Bell with what eventually became the ineffective P-39, while the $163,000AC-9974 twin contract went to Lockheed’s Model 22. Lockhheed’s chief designer, Hall Hibbard, and senior ,designer, C larence “Kelly” Johnson, an M IT Master’s graduate, had gone through six unorthodox airframe configurations before settling on the t’Yin boom layout The XP-38 airframe proposal carried 400USG of fuel internally, employed a near to symmetrical NACA 23016/4412 section and grossed out at 11,4001b. Designed for l,150hp engines, the Model 22 was built to exceed 360kt at altitude, stunning performance for the time. Johnson had at the time commented in detail on the possibility of compressibility affecting the handling of the aircraft, this was later to prove to be a major issue.

Construction of the first XP-38 began in July 1938, while Lockheed was gearing up for mass production of Hudsons for the RAF. Some fabrication problems developed, but these were overcome and the first prototype was loaded on a truck for its journey to MarchField on December 31, 1938.

The sleek silver prototype was worked on for the following two weeks, and first flew on January 27, piloted by Lt Ben Kelsey, the writer of the initial specification. The first flight was troubled, with severe flap vibration due to a broken support rod, but ended safely, in spite of brake problems. Subsequent flights saw a range of minor problems resolved, as the flight test programme progressed.

The XP-38 proved to be a stunning performer, easily achieving 350kt speeds. The system design of the airframe and propulsion was unique and radical, while strictly functional. The powerplant installation in the nacelle/tailbooms exemplified this. The V-1710 engine was mounted in the front of the nacelle, driving a large three bladed Curtiss Electric constant speed prop. The GE turbochargers were mounted in the booms, aft of the wing, with intercoolers embedded in the outer leading edges of the wing; ie the airflow was channelled to the wingtip via a corrugated double skin and back via the leading edge cavity, and engine glycol radiators in aft boom scoops. The armament of four 0. 50 cal machine guns and a single cannon was mounted in the nose, thus neatly avoiding the dispersion problems associated with wing mounted guns.

The test programme progressed rapidly and by February, 1939, the flight test team decided to attempt a long range record breaking flight across the continental US, in spite of unresolved flap and brake system problems. The attempt ended however in disaster, when carburettor icing during a prolonged approach at Mitchel Field in NY state, near the very end of the flight, caused a loss of power. Lt Ben Kelsey force landed the aircraft on a local golf course. The XP-38 was wrecked, but fortunately Kelsey survived and had successfully demonstrated the superlative speed and range of the aircraft.

The USAAF, on the strength of completed tests, ordered 13 development aircraft, designated YP-38. The Lockheed Model 122-62-02 was fitted with a pair of V-1710-F2 engines rated at 1,150bhp with GE B-2 turbochargers and weighed in at 11,1711b empty for a design weight of 13,5001b. Armament was specified at one 37mm Oldsmobile M9 cannon, two . 50 cal and two . 30 cal machine guns. Counter rotating props were specified, these rotating inboard.

The P-38 was clearly a hot performer and the UK Air Ministry and French AF soon took an interest in the type, seeking a nonturbocharged variant with identical powerplants (and same sense prop rotation) to the Curtiss Tomahawks at that time ordered in significant numbers. Designated the Model 322B and F respectively; the RAF promptly sought a total of 667 of these aircraft, a far cry from the 60 or so which Lockheed expected the US government to purchase. Unfortunately; the buyers did not appreciate the limitations of the V-1710 without turbochargers and Lockheed negotiators accepted the order in spite of the known discrepancy and objections from engineering. This was to have unfortunate consequences at a later stage. The US government also moved to order the P-38, requesting in July 1939, 66 aircraft 1940 saw the collapse of France under the treads of Wehrmacht armour, while Lockheed worked away at producing the first YP-38s. The Battle of Britain passed, and much was learned about what was really needed in a fighter, particularly performance at altitude. The first YP-38 flew in September 1940, soon followed by the development aircraft.

These in turn were followed by thirty P-38s, armed with four . 50 cal machine guns in addition to the cannon, the balance of the initial sixty being made up of the subsequent P-38D.

Baptism of Fire – the P-38D and E

Lockheed delivered all thirty P-38Ds to the USAAF by August 1941. The D-model was the first combat capable subtype and was fitted with self sealing tanks, detailed aerodynamic changes, Dural bladed props, a low pressure Oxygen system and typically a 23mm cannon.

The P-38D was followed in production by the P-38E from September 1941 through to April 1942. The P-38E saw further refinements, with a single Bendix 20mm Ml cannon (Hispano) with 150rpg fitted, changes to the hydraulic and electrical systems, flight instruments and nose undercarriage. In total, 2,000 design changes were carried out to meet the needs of mass production.

The P-38E was followed in production by P-38Fs and RAF spec non-turbocharged 322-Bs, 143 of which were ordered in April 1940 as the Lightning I. The first RAF machines were delivered for testing in March 1942.

The RAF was unhappy with the 322, as its high altitude performance was inferior to the then current Merlin 40 series powered Spitfire V. The 322 had by that time also demonstrated problems due to compressibility in dives which caused ‘Mach tuck’, a severe nose down pitching moment due to the aft shift of the Cof’P. This often led to the breakup of the aircraft and usually, loss of the pilot. Like prop rotation sense impaired engine out handling. The 322 affair escalated into a major dispute between Lockheed and the RAF and in the end, all Lightning I airframes were transfered to the USA AF which used them as trainers, under the designation of P-322. The turbocharged Lightning Ils became USAAF production P-38Gs.

Interestingly, the performance problems could have been fixed by fitting Merlins, Lockheed engineers considered this seriously enough to do a paper study in 1941 which indicated that Merlin XX powerplants would provide superior performance, while improving reliability. The US Army however rejected the idea (it has been stated as under the influence of US commercial interests) and thus sentenced the P-38 to engine problems which were not solved until mid 1943.

When the US entered the war in December 1941, the only serious fighters it had were a mixed bag of P-38Ds and Es, and the Curtiss P-40 and Bell P-39 which lacked the speed and altitude performance to challenge the Japanese Zero and German Bf109s.

The first Lightnings to see combat operations were the photoreconnaissance F-4s of the 8th Photo Group, based in Australia, flying recce sorties over New Guinea and the Coral Sea. Initial deployments of P-38D and E models saw units stationed in the Aleutians and Iceland, with the first combat kill credited to a P-38E in the Aleutians in August 1942,downing a H6K Mavis recce aircraft, soon followed by the killing of a Fw200 Condor off Iceland, by a P-38D.

As the US moved to a war footing, the P-38E was deployed during operation BOLERO to the UK together with later model P-38F aircraft. Initial deployments saw the P-38s fly the Atlantic via Greenland, led by B-17s. After some losses, subsequent aircraft were transported on ships.

The Fork Tailed Devil – the P-38F, G and H

P-38F deliveries commenced in March 1942, this variant being fitted with F-4 model engines rated at 1,225hp and equipped with pylons for 165USG drop tanks. Combat flaps were fitted, this facility allowing partial flap deployment at manoeuvre speeds to increase turn rate. The P-38F was followed in production by the P-38G from August 1942. The P-38G had F-10 engines rated at 1,325hp, a 300psi Oxygen system using three bottles in the booms, strengthened pylons for 300USG drop tanks and a larger combat flap envelope.

The mixed P-38E/F force was deployed to New Guinea,while the UK based aircraft were redeployed to North Africa for the Torch landings. In the Pacific, the P-38 quickly demonstrated its superiority over the A6M3 Hamp (Zero) and Ki-43 Oscar. The P-40s and B! early 1943, several P-38 pilots reached ace status, including Richard Bong, later to become the leading US ace of the war. Equipping the 9th and 39th Fighter Squadrons of the 49th and 35th Fighter Groups respectively, these aircraft played a major role in the March 1943 Battle of the Bismarck Sea, stripping the Japanese convoy of its fighter cover.

In August 1942, the Americans landed on Guadalcanal and the P-38 was deployed there soon after with the 13th AF, flying long range fighter missions into the Solomons. Flying from Guadalcanal, in April 1943, 16 P-38Fs of the 70th and 339th Fighter Squadrons flew 350nm to Bouganville, at low level, to engage and destroy Japanese flight carrying Adm Isoroku Yamamoto, Japan’s leadmg naval strategist. In the engagement, Capts Tom Lanphier and Rex Barber downed two G4M Bettys, one of which contained the Japanese admiral.

The key to extracting range from the P-38 was very much in flying technique, usinglow RPM and high boost (eg P-38H 2 300rpm and 34i inches of boost for 215kt at 146 USG/hr for 600+nm radius), and until 1944 this was the art of individual units and pilots.

In the ETO, the 8th Air Force was still working up and the bomber commanders initially saw little use for the Lightning, as they still believed in the concept of unescorted daylight bombing. Nearly all P-38F/Gs were deployed to North Africa, to support the Torch landings in Morocco and Algiers.

The P-38s flew airsuperiority and ground attack missions in the MTO, inflicting heavy damage on the German and Italian air, sea and land convoys attempting to reinforce the theatre. The P-38 was the only US fighter capable of engaging the Bfl09G and Fwl90A on equal terms, providing escort for bombers well out of the range P-39 suffered heavy attrition in the defence of Port Moresby, and the arrival of the P -38 late in 1942 saw the odds begin to swing in favour of Gen Kenney’s 5th Air Force.

The P-38 first engaged the Japanese on the December 27, destroying 12 aircraft and claiming four probables in a sortie over Buna. of the RAF Spitfires. By mid March 1943, the Axis had a force in excess of 500 Ju-52s, Me-323s and SM. 82s dedicated to reinforcing the theatre. The Allies applied the long legged P-38 to cut this air bridge from Sicily,some measure ofthe intensity of this battle can be gauged by three notable sorties. On April 5, 26 P-38s engaged a convoy of 70 Ju-52s escorted by 24 Luftwaffe fighters, destroying 1 1 transports and two fighters, for the loss of three P-38s. On April 10, 41 transports and eight fighters were despatched, the following day 26 Ju-52s and five fighters were destroyed for no loss.

The Allied landings in Sicily and Italy saw further successes for the P-38 force, a notable highlight being an Allied convoy escort CAP (Combat Air Patrol) on October 9, during which Lt Col W L Leverette killed seven Ju-87 dive bombers, another of his pilots killing another five aircraft. It is not surprising that German pilots nicknamed the P-38 Der Gabelschwanz Teufel (the Fork Tailed Devil). The outstanding success of the P-38 in the Med and the Pacific was not matched by units of the 8th AF in the UK. These were applied to the long range escort role, equipped with the P-38H. The H model, a stopgap while production of the P-38J was being organised, supplanted the G in May 1943, and differed primarily in the use of more powerful F-17 engines with automatic engine mixture controls (autolean/autorich), B-33 turbochargers and automatic oil cooler flaps, and a new AN-M2C cannon. The more powerful V-1710F-17 hit the design limits of the leading edge intercoolers, oil coolers and radiators, which limited military power outputto l,240-1,350hp, only late build aircraft with improved oil coolers could maintain the nominal 1,425hp. D

Next Issue: Part II looks at the Lightnings uninspiring record in the high altitude escort role over Germany. Fortunately, later versions overcame the problems being encountered in this new role and the type went on to be one of the most effective US fighters of the period. Don’t miss it!