Thursday, August 05, 2021
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Lockheed P-38 Lightning

 

The P-38 was powered by two Allison V-1720 liquid cooled engines driving Curtiss Electric opposite rotating propellers.  Each engine had a General Electric turbo-supercharger that was recessed in to the top of each tail boom.  The tail booms, unique to the P-38, replaced the central and rear parts of what would normally be the fuselage.  The fuel system consisted of six fuel tanks, four in the centre section of the wing and two in the outer sections of each wing.  Each engine had a separate feed from its own outer wing tank but the four inner wing tanks were interconnected to provide fuel flow to both engine. 

 

The pilot’s cockpit was positioned in a central nacelle which also contained the armament, one 22mm cannon and four 0.5 machine guns, all of which fired forward with no convergence.  The screen was initially curved but after the model J the centre section had optically flat bullet proof glass fitted.  Armour plating was provided on the front bulkhead, on the back and bottom of the pilot’s seat and behind the pilot’s seat and head.  Armour plate was also located on the inboard side of the turbo-superchargers to protect the pilot from possible fragmentation of the turbo blades.  The nacelle was an all metal structure built of bulkheads and covered with flush riveted smooth metal skin. 

 

The Lightning had a tricycle undercarriage with the nose landing gear being located in the central nacelle and the main landing gear being housed in the tail booms.  All wheels retracted rearwards with each main wheel having brakes.  The layout of the undercarriage and position of the central nacelle ensured that the pilot had good forward visibility at all times.  Each boom had a tail with a rudder and elevator and the rear of the booms were connected with a single tailpiece that also contained an elevator with a trim tab.

 

At the conception stage the design team, led by Kelly Johnson (* see note), would have liked to have used the wing design employed by R.J. Mitchell on the Spitfire but due to the internal fuel load requirements (400 gallons) and oil capacity (four times that of the Spitfire) had to settle for a near symmetrical airfoil of relatively thick section.  The wing was constructed in five sections and was of an all metal construction, mainly Alclad.  The ailerons had a hydraulic ‘boost’ system that allowed the pilot ‘feel’ but removed over 80% of the operating force required.  Fowler flaps were employed which from the 38G model became what were referred to as ‘manoeuvring’.  In essence the flaps were given a special combat setting which permitted a small extension and droop to provide greatly increased lift for very little drag with the result that a high degree of manoeuvrability was available over a wide speed range.  Cooling radiators were positioned on the flanks of the tail booms and on early models induction intercoolers were located on the wing leading edges.  On later models the intercoolers were repositioned together with the oil coolers under the engines.  There was a major accessibility problem surrounding the location of the engine and other equipment within the limit confines of the twin booms.

 

The P-38 first flew in January 1939 and first saw combat in August 1942.  Over 9000 were built most going to the ETO.  All of the P-38’s operating in the Far East were allocated to American squadrons. 

 

There are many recorded incidents involving the P-38 but possibly the most widely known was the attack made by sixteen Lightnings belonging to 339 Fighter Squadron on the 18th April 1943.  These P-38’s, acting on intelligence information, destroyed an aircraft carrying Admiral Isoroku Yamamoto, in the process the Admiral was killed.  It was aircraft flown from Admiral Yamamoto’s carrier fleet that had attacked Pearl Harbor on the 7th December 1941.

 

(Data from Duxford and Hendon archives)

 

‘Kelly’ Johnson (article in ‘Engineering Management Journal’):  Born Clarence Leonard in 1912 to a family of Swedish immigrants.  Father was a jobbing bricklayer and carpenter and in the summer recess Clarence helped out on building sites.  A strong and stocky youngster he had a natural aggression that earned him the nickname ‘Kelly’ (fighting Irish).  Went on to Michigan university graduating in 1932 with a Bachelor of Science degree and continued his studies at the university under Professor Edward Stalker in the field of aerodynamics.

 

Allan and Malcolm Loughead, pronounced Lockheed, founded the Alco Hydroplane Company in 1913.  In 1916 company folded.  Started up again a few years later.  John Northrop joined the company which floundered again in 1921.  Third attempt made to establish the company in 1926 under the name ‘Lockheed Aircraft Corporation’.  The growing success of the company resulted in it being taken over in 1929 by the Detriot Aircraft Corporation.  This company collapsed in 1931.  Some old hands, which did not include Allan Loughead, acquired the assets of Lockheed.  Hall L Hibbard was hired to design a modern all metal monoplane.  The model for Hibbard’s design was sent to Michigan university whose wind tunnel was used to confirm the flight characteristics.  The wind tunnel work was carried out by ‘Kelly’ Johnson (KJ).  The resultant model became the famous Electra.  KJ became Lockheed’s thirty sixth employee.

 

Lockheed gave KJ a thorough grounding in every aspect of aircraft design, by 1938 he had become Chief Research Engineer.  In 1936 the USAAF briefed companies on a radical new fighter aircraft.  Hibbard and KJ submitted a design that became the P-38.  The success of the Lightning and Hudson, which was derived from the Electra design, transformed Lockheed.  In 1931 the company had fifty employees.  By 1943 it employed, worldwide, ninety four thousand people.  In the same year Lockheed was given a contract to develop a jet fighter.  KJ set up a research and development organisation separate from the rest of the works.  It became a prototype for ‘project management’.  KJ’s team produced the F-80 ‘Shooting Star’, then in the early 1950s the F-104 ‘Starfighter’ and U2 spy plane.

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