THE 456th FIGHTER INTERCEPTOR SQUADRON

THE PROTECTORS OF  S. A. C.

 

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The One Of A Kind XP-38

 

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Lockheed XP-38 - twin-boomed Model 22 design studies

P-38 Lightning

 "During the winter of 1943-1944, I was assigned an airplane that turned out to be the aircraft that provided more information regarding problems in cold weather than most others. It was a P-38J-LO, "Lightning", #213565. This P-38 was specially equipped with 54 thermocouples located in as many places in the aircraft, and I could read the temperature of each through selectors with a potentiometer located where the gun sight normally was mounted. This special installation enabled us to study machine gun lubrication, engine lubrication, cabin heat, carburetor heat and fuel distribution problems, etc. The Lockheed engineer assigned to my project was Lee C. Chambers, a wonderful man, and a great help to many of the project officers in the Cold Weather Test Detachment at Ladd Field, Fairbanks.

"Throughout the month of March, this P-38 was assigned a very special project testing a set of retractable skis. Mr. Frank Ditter, the president of Federal Aircraft Skis, Minneapolis, Minnesota, the manufacturer, assisted with the installation and testing. His personal interest was created by some problems which occured when another P-38 was ski equipped in northern Minnesota. It was damaged on the ground and never flew.

" Would you believe that it snowed 26 of the 31 days that month, with a total accumulation of 34.5 inches? The conditions were ideal for our tests, and I made 165 landings, with complete retraction and extension of the skis between each landing. The interest around the base was high, especially among the Russians based at Ladd Field. Every operation was successful, even the dive test, during which the plane reached speeds up to 450 mph. The advantages were small, though. The ski loading was 640 pounds per square foot, and regardless of the depth of the snow, the skis went to the bottom of it. The propeller clearance was only 14 inches and we could plow that much snow on wheels. The skis worked well on rough snow, covered ground, or ice with cracks, while on glazed ice the landing slide was 7,000 feet. With no torque involved and the engines idling at 500 rpm, it was easy to do figure eights on the ground in the width of the runway.

"It was a pleasure to be the project officer on this aircraft and make it do all the special things that it was capable of doing. While testing the skis, the right engine was flown with the first synthetic oil ever flown, carrying a 165 gallon belly tank on the right side only, with a quantity of synthetic oil just to service the right engine. This unbalanced looking condition drove some of the Russian pilots up a tree, wondering how the P-38 flew with all that weight on one side.

"We were able to start the Allisons without heat and off the battery down to -30 degrees. It was a very good cold weather airplane and I was always first off the ground on cold mornings. "

-Randy Acord, Capt., AAC

 

 

The Lockheed XP-38 Lightning

Joe Baugher

 

The Lockheed P-38 Lightning racked up an impressive series of "firsts"--it was the first Lockheed-designed military aircraft to go into series production, it was the first twin-engined interceptor to serve with the USAAC, it was the first production fighter powered by the Allison V-1710 in-line engine, it was the first modern fighter equipped with a tricycle landing gear, it was the first American plane to use butt-jointed flush riveted external surfaces, it was the first to make extensive use of stainless steel, it was the first fighter to use a bubble canopy right from the start, it was the first fighter with speeds over 400 mph, it was the first US twin-boom fighter to go into production, it was the first USAAF fighter to shoot down a German aircraft, it was the first USAAF fighter to carry out an escort mission to Berlin, it was the first USAAF plane to land in Japan after that country had surrendered, it was the heaviest US single-seat fighter of World War 2, it was the only American fighter in production at the time of Pearl Harbor to be still in production at the war's end, and it accounted for more Japanese aircraft destroyed in combat than any other US fighter.

A total of 10,037 Lockheed Lightnings were built.

Lockheed was invited along with Boeing, Consolidated, Curtiss, Douglas, and Vultee to take part in a USAAC design competition X-608 for a twin-engined high-altitude interceptor. The specification called for a maximum speed of at least 360 mph at 20,000 feet and 290 mph at sea level, an endurance at full throttle of one hour at 20,000 feet, and the ability to take off and land over a 50-foot obstacle within 2200 feet.

The Lockheed design staff was headed by Hall L. Hibbard. Working with Hibbard was the soon-to-be famous Clarence L. "Kelly" Johnson. After studying a lot of different designs, Hibbard and Johnson finally settled on a twin-boom design with each boom extending aft of the engine and the pilot sitting in an enclosed cockpit in a central nacelle. Each boom was to house one of the new 1150 hp Allison V-1710C twelve-cylinder liquid-cooled engine with an exhaust-driven turbosupercharger. The Allison engine at that time had just completed a 150-hour type approval test at 1000 hp. The central nacelle contained a forward-firing armament of one cannon and four 0.50-in machine guns. This armament was quite heavy for its time, the standard USAAC armament of the day being one 0.30-in and one 0.50-in machine guns. One advantage of the twin-boom layout was the possibility of installing the armament in the central nacelle, unhampered by synchronizing gear and allowing sighting of the parallel streams of fire up to the maximum range of 1000 yards. Tail surfaces consisted of a fin and rudder at the end of each boom and a horizontal tailplane and elevator between the booms. It was anticipated that the twin fin-and-rudder tail assembly would increase the effective aspect ratio of the tailplane by the endplate effect, thereby providing stability over a large c.g. range. At 14,800 pounds, the XP-38 weighed more than a bombed-up Bristol Blenheim I, at that time the standard British medium bomber. Fowler flaps were fitted between the ailerons and the booms and between the booms beneath the trailing edge of the wing center section.

The project was given the company designation Model 22-64-01. Lockheed promised a maximum speed of over 400 mph. Although the USAAC was somewhat skeptical about so radical a design, the Model 22 won Design Competition X-608 and on June 23, 1937, Lockheed was awarded a contract for one XP-38 prototype (Ser No 37-457). Construction began in July 1938. Construction 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) engines, which developed 960 hp at 10,000 feet and 1090 hp at 13,200 feet. Each engine had a General Electric B-1 turbosupercharger. To combat torque, the propellers rotated in opposite directions, a special version of the Allison engine being produced with a left-hand rotating propeller shaft. The engines had inwardly-rotating propellers. No armament was installed on the XP-38.

The XP-38 aircraft was completed in December of 1938. On the last day of the year, the completed XP-38 was stripped down, covered with canvas, and loaded onto three trucks. In great secrecy, the convoy of trucks was escorted by police to March Field, near Riverside, California, where Air Corps Project Officer Lt. Benjamin S. Kelsey was to began the flight testing. However, on the very first ground run, the wheel brakes failed and the XP-38 ended up in a ditch. Lt. Kelsey finally took the XP-38 into the air for the first time on January 27, 1939. The early test flights turned up some problems with the wheel brakes and with vibrations of the flaps, requiring that some modifications be made to the prototype. Maximum speed was 413 mph at 20,000 feet, and an altitude of 20,000 feet could be attained in 6.5 minutes. Service ceiling was 38,000 feet. Empty weight was 11,507 lbs, gross weight was 13,964 lbs, and maximum takeoff weight was 15,416 lbs

Reaction to the first few test flights was highly favorable. In spite of the problems encountered on its first few flights, it was decided to attempt a record transcontinental flight before delivering the XP-38 to the Army at Wright Field. At daybreak on February 11, 1939, Ben Kelsey left March Field destined for Mitchell Field, New York with refuelling stops at Amarillo, Texas and Wright Field, Ohio. On the final leg of the flight, the XP-38 lost power as Kelsey was coming in for a landing at Mitchell Field and crashed on a golf course just short of the runway. Fortunately, Lt. Kelsey was unhurt, but the XP-38 was a total loss.

Joe Baugher

References:

 

  1. Lockheed Aircraft Since 1913, Rene J. Francillon, Naval Institute Press, 1987
     

  2. The P-38J-M Lockheed Lightning, Profile Publications, Le Roy Weber Profile Publications, Ltd, 1965.
     

  3. War Planes of the Second World War, Fighters, Volume Four, William Green, Doubleday, 1964.
     

  4. Famous Fighters of the Second World War, William Green, Doubleday, 1967.
     

  5. The American Fighter, Enzo Anguluci and Peter Bowers, Orion Books, 1987.
     

  6. Wings of the Weird and Wonderful, Captain Eric Brown, Airlife, 1985.
     

  7. United States Military Aircraft since 1909, Gordon Swanborough and Peter M. Bowers, Smithsonian Institution Press, 1989.
     

  8. E-mail from Daniel Stover on P-38 production counts

 

 

The XP-38 CRASH NEWS STORY

U.S. Air Force Fact Sheet


“Mystery” Plane Crashes At End Of Test Speed Hop; Fails to Break Hughes Mark

New York, February 11 (1939)-(AP)-
A new secret twin-motor Army pursuit monoplane crashed into a tree on the edge of Mitchel Field on Long Island tonight at the end of a near-record transcontinental test flight.

The pilot and sole occupant, Lieutenant Ben S. Kelsey, crack test flier, was saved from serious injury by the plane’s all-steel cabin.

Kelsey took off from March Field, Calif., at 9:12 a.m. (Eastern Standard Time), stopped briefly at Amarillo, Texas, and Dayton, Ohio, and arrived here at 4:57 p.m. His elapsed time of 7 hours 45 minutes was only 16 minutes and 35 seconds longer than Howard Hughes' 1937 Burbank, Calif.-Newark, N.J. nonstop record.

He apparently overshot the field, observers said, and zoomed the motors to pick up speed and altitude. The right motor appeared to choke, sending him into a steep right turn.

As Kelsey cut the throttle again, the plane slipped down and sheared off the tops of trees bordering the field, the undercarriage caught in a thirty-five-foot tree, and the plane plunged down into a sand pit on the Cold Stream Golf Course.

Bystanders pulled Kelsey out of the wreckage. He was taken to a hospital with cuts on one eye and one hand, and suffering from shock. He was released after examination.

Scores of cars jammed around the spot. Field officials threw a fifty-man guard around the wreckage and rushed the plane’s instruments to the field office, their condition undetermined.

Colonel James Chaney, field commandant, called an inquiry board into session immediately, with Kelsey present. The findings were expected to be kept secret and sent to Washington in an army plane.

The weather at the time of the crash was clear, with a light shifting wind. At the time of the crash it was blowing southeast.

The plane was a new Lockheed, the Army’s first twin-engined pursuit plane, completed at the Lockheed Burbank plant two weeks ago and capable of doing 350 miles an hour.

It was an all-metal single-seater, with stratosphere operating equipment, tricycle undercarriage, and super-high lift devices.

It was designed to carry a nest of high-power machine guns, but none today. Its designation was XP-38.

Kelsey left Amarillo at 12:21 p.m. (E.S.T.), stopped at Dayton for 20 minutes, and took off at 3:34 p.m. (E.S.T.)

His distance was estimated officially at about 2,400 miles. Hughes flight was about 2,587 miles.

Kelsey, 33, is married and is regularly assigned to the laboratory division of Wright Field, Dayton

 

 

Photo Gallery

 

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The Lockheed P-38 Lightning

By Greg Goebel  /   Public Domain

The P-38 Lightning was one of the most important American fighters of the Second World War. Although its operational record was somewhat mixed, in general the P-38 was a fast, powerful, and capable aircraft that performed well in a wide range of roles. This document provides a short history of the P-38.

 

The Origins

 The Lockheed P-38 was designed in response to a 1937 US Army Air Corps (USAAC) specification for a high-altitude interceptor, capable of 580 KPH at an altitude of 6,100 meters (360 MPH at 20,000 feet). The Bell P-39 Airacobra and the Curtiss P-40 Warhawk were designed to meet the same request.

At that time, really powerful piston engines that could push prop-fighter performance to the limit were not available, and so the Lockheed design team, under the direction of Clarence "Kelly" Johnson, who would eventually design a string of famous aircraft up to the SR-71 Blackbird spy plane, decided to use two supercharged 12-cylinder, V-inline, water-cooled Allison V-1710 engines. When Johnson selected it, the Allison had not been rated at even 746 kW (1,000 HP).

Johnson's initial concepts for the new fighter covered a range of configurations, but the Lockheed team finally decided on a scheme with twin booms to accommodate the engines, and with the pilot and armament in a central nacelle. The propellers would rotate in opposite directions to eliminate the effect of torque. The superchargers were positioned in the booms, behind the engines. Armament was to consist of four machine guns in the nose of the nacelle, clustered around a cannon. The design featured tricycle landing gear, making the aircraft one of the first with such a feature.

The prototype Lockheed "Model 22", later designated the "XP-38", was rolled out in December 1938 and first flew on 27 January 1939. It was powered by "handed" Allison V-1710-11 and V1710-15 engines with 716 kW (960 HP) each. The XP-38 set a cross-continental speed record by flying from California to New York on 11 February 1939, in 7 hours and 2 minutes, including two fuel stops. Unfortunately, the prototype landed short of the runway in New York and was wrecked, much to the distress of the Lockheed engineering team. They had opposed the flight, but it was done at the insistence of General Henry "Hap" Arnold, commander of the USAAC.

The engineers regarded the loss of the aircraft as a serious setback, but it had a beneficial side effect. On the basis of the record flight, the Air Corps ordered 13 "YP-38" evaluation aircraft in April 1939. If the XP-38 had not been destroyed, orders would not have been placed until the prototype had been thoroughly evaluated.

However, manufacture of the YP-38s proved troublesome, and the first didn't roll off the production line until September 1940, with the last delivered in June 1941. Although they looked much like the custom-built XP-38, they were substantially redesigned and differed greatly in detail. They were lighter, and there were changes in engine fit, most particularly in that the direction of propeller spin was reversed, with the propellers rotating up towards the cockpit rather than down as had been the case in the XP-38.

They were powered by Allison V-1710-27/29 engines with 858 kW (1,150 HP) each. Although weapons were not fitted in most of these aircraft, they were designed to be armed with two 12.7 millimeter (0.50 caliber) Browning machine guns with 200 rounds per gun, two 7.62 millimeter (0.30 caliber) Browning machine guns with 500 rounds per gun, and an Oldsmobile 37 millimeter cannon with 15 rounds.

Orders were already in hand from France, Britain, and the USAAC. The French and the British ordered a total of 667, with a "Model 322F" for the French and a "Model 322B" for the British. Each of these variants had unique minor equipment fits tailored for their respective air arms, such as metric measurements on the flight indicators for the French aircraft, but they both shared a major change from all other P-38 variants that were ever made: the superchargers were to be deleted, and the left-handed and right-handed engine arrangement was to be changed to twin right-handed engines.

As superchargers were a new technology, the Anglo-French purchasing commission that ordered the fighters was concerned that the superchargers might lead to delays, and felt that as the aircraft were intended for medium-altitude combat the superchargers would not be needed. The requirement for the sole use of right-handed engines was for commonality with the large numbers of Curtiss Tomahawks both nations had on order. Lockheed engineers protested strongly against this decision, and privately labeled the variant the "castrated" P-38.

After the fall of France in June 1940, the British took over the entire order. They decided that only the first 143 of the order would be delivered in the castrated format, as "Model 322 Lightning Is", with the remaining 524 to be delivered with superchargers and left and right-handed engines, as "Model 322 Lightning IIs".

The British never got that far. Three of the castrated Lightning Is were delivered to the UK in March 1942, and were promptly given a thumbs-down. They "redlined" at 480 KPH (300 MPH) and had nasty handling characteristics. The entire order was cancelled.

The remaining 140 Lightning Is were completed for the USAAF. and the rest of this batch of castrated aircraft, most of them refitted with contra-rotating engines but still minus superchargers, were relegated to US Army Air Forces (USAAF, which superseded the USAAC in June 1941) for training under the designation "RP-322".

These aircraft helped the USAAF train new pilots to fly a powerful and complex new fighter. The RP-322 was actually a fairly hot aircraft at low altitude and satisfactory in the training role. The other positive result of this fiasco was to give the aircraft its name: "Lightning". Lockheed had originally wanted to call it the "Atlanta", but the RAF name won out. 30 initial production "P-38 Lightings" were delivered to the USAAF in mid-1941. Although not all these aircraft were armed, when they were they were fitted with four 12.7 millimeter machine guns, instead of the pair of 12.7 millimeter and pair of 7.62 millimeter weapons of their predecessors. The 37 millimeter cannon was retained. They also had armor glass, cockpit armor, and fluorescent cockpit controls. One was completed with a pressurized cabin on an experimental basis and designated "XP-38A".

The 30 P-38s were part of an order for 66, but in light of USAAF feedback the remaining 36 in the batch were fitted with various small improvements such as self-sealing tanks and enhanced armor protect to make them "combat capable". For some odd reason, the USAAF specified that these 36 aircraft were to be designated "P-38D". As a result, there never were any P-38Bs or P-38Cs. Early Lightning production variants are a confusing subject.

None of these aircraft ever saw combat. Their main role in the story of the P-38 was to work out bugs and give the USAAF experience with handling the type.

Tail flutter was quickly found to be a problem. As a fix, small weights were attached to little booms in the middle of the elevator. Kelly Johnson was contemptuous of the "fix", regarding the weights as useless, and in fact the buffeting eventually proved to be due to the straight connection of the wing root to the fuselage pod. A few aerodynamic changes, most particularly the addition of a wing-root fillet, solved the problem. Nonetheless, the little weights were a feature of every P-38 built from then on.

A more serious problem was "compressibility stall", the tendency of the controls to simply lock up in a high-speed dive, leaving the pilot no option but to bail out. The tail structure also had a nasty tendency to fall apart under such circumstances, and in fact this problem killed a YP-38 test pilot, Ralph Virden, in November 1940. A USAAC major named Signa Gilkey managed to stay with a YP-38 in a compressibility lockup, riding it out until he got to denser air, where he recovered using elevator trim. This feat led to experiments that would eventually resolve the problem.

Kelly Johnson later recalled: "I broke an ulcer over compressibility on the P-38 because we flew into a speed range where no one had ever been before, and we had difficulty convincing people that it wasn't the funny-looking airplane itself, but a fundamental physical problem. We found out what happened when the Lightning shed its tail, and we worked during the whole war to get 15 more knots more speed out of the P-38. We saw compressibility as a brick wall for a long time. Then we learned how to get through it."

That would not be until later, however, and the new P-38 had other defects. The most dangerous problem was that if one engine failed on takeoff, "asymmetric power" would flip the aircraft over and slam it upside-down into the ground. Eventually, procedures were devised to allow a pilot to deal with the situation: reduce power on the running engine, feather the prop on the dead engine, and then increase power gradually until the aircraft was in stable flight.

This took a skilled pilot. An unskilled pilot died. The P-38 went into combat with a bad reputation.

 

The Lightning's Go To War

The first combat-capable Lightning was the "P-38E", which featured improved instruments, electrical systems, and hydraulic systems; new Curtiss Electric duralumin propellers, though early P-38E production retained the older Hamilton Standard Hydromantic hollow steel propellers; an SCR-247N radio; and the definitive armament configuration, featuring four 12.7 millimeter machine guns with 500 rounds per gun, and a Hispano 20 millimeter cannon with 150 rounds instead of the unreliable Oldsmobile 37 millimeter cannon.

Interestingly, while the machine guns had been arranged symmetrically in the nose on earlier variants, they were "staggered" in the P-38E and later versions, with the muzzles sticking out of the nose in the relative lengths of roughly 1:4:6:2. This was done to ensure a straight ammunition belt feed into the weapons, as the earlier arrangement had led to jams. 

The first P-38E rolled out of the factory in October 1941. 210 P-38Es were built. They were followed, starting in April 1942, by the "P-38F", which featured Allison V-1710-49/53 engines with 988 kW (1,325 HP each); an SCR-522 or SCR-535 radio; and racks inboard of the engines for fuel tanks or a total of 900 kilograms (2,000 pounds) of bombs. 527 P-38Fs were built.

Over a hundred P-38Es were completed in the factory or converted in the field to a photo-reconnaissance variant, the "F-4", in which the guns were replaced by four cameras in a modified nose. Most of these early reconnaissance Lightning's were retained stateside for training, but the F-4 was the first Lightning to see combat, beginning operations out of Australia and then New Guinea in April 1942. Three of the F-4s were operated by the Royal Australian Air Force in this theater for short period, beginning in September 1942.

By June 1942, P-38s were operating in the Aleutians as well. The fighter's long range made it well-suited to the campaign over the almost 2,000 kilometer (1,200 mile) long island chain, and it would be flown there for the rest of the war. It was one of the most rugged environments available for testing the new aircraft under combat conditions. More Lightning's were lost due to weather and other conditions than enemy action. There were cases where Lightning pilots, mesmerized by flying for hours over gray seas under gray skies, simply flew into the water.

Nonetheless, the P-38 scored successes. On 4 August 1942, two P-38Es, operating at the 1,600 kilometer (1,000 mile) end of a long-range patrol, bounced a pair of Japanese Kawanishi H6K "Mavis" flying boats and destroyed them. They were the first of many Japanese aircraft to be shot down by the Lightning.

In the meantime, Lightning's were ferrying themselves across the Atlantic via Iceland to England, though most of them made the trip on freighters. On 15 August, a P-38F and a P-40 operating out of Iceland shot down a Focke-Wulf 200 shipping raider over the Atlantic. This was reputedly the first Luftwaffe aircraft destroyed by the USAAF.

The Lightning's sent to England were part of the force being built up for the invasion of North Africa. The invasion took place in November 1942, and Lightning pilots, including those of a photo-reconnaissance unit under command of Colonel Elliot Roosevelt, the American president's son, then began acquiring familiarity with operating under "austere conditions" and matching their skills and aircraft against the enemy.

The Lightning proved surprisingly maneuverable at low altitudes. The contra-rotating props had the benefit of eliminating the effects of engine torque, and on occasion a Lightning could even out-turn smaller fighters. However, maneuverability wasn't its strong suit, its major virtue in close combat being a "terrific zoom climb" that would leave pursuers in the dust.

Luftwaffe pilots also quickly learned not to make head-on attacks on the P-38, since its concentrated firepower made such a tactic suicidal. Although not the best dogfighter, the P-38 was a formidable interceptor and attack aircraft, and in the hands of a good pilot it could be dangerous in air-to-air combat. The P-38 remained a force to be reckoned with in the Mediterranean for the rest of the war.

The Lightning proved ideally suited for the Pacific theater, as it combined excellent performance with very long range required for operations over wide reaches of ocean. While the P-38 could not outmaneuver the Zero and most other Japanese fighters, its speed and climb gave American pilots the option of choosing to fight or run, and its focused firepower was even more deadly to lightly-armored Japanese warplanes than to the Germans. Jiro Horikoshi, who headed the design team that build the Zero, wrote: "The peculiar sound of the P-38's twin engines became both familiar and hated by the Japanese all across the South Pacific."

General George Kenney, commander of the USAAF Fifth Air Force operating in New Guinea, could not get enough P-38s. This could be seen as limited praise since Kenney otherwise had to rely on serviceable but inadequate P-39s and P-40s, but Lightning pilots began to compete in racking up scores against Japanese aircraft, including one of the most famous missions of the war, the airborne assassination of Admiral Isoroku Yamamoto on 17 April 1943.

Yamamoto was the architect of Japan's naval strategy in the Pacific. When American code breakers found out that he was flying to Bougainville Island to conduct a front-line inspection, 16 Lightning's were sent on a long-range flight to intercept him. The mission went off perfectly, the Lightning's met Yamamoto's G4M "Betty" bomber and escorting Zero fighters just as they arrived, and the G4M was shot down over the jungle. The admiral was killed.

The P-38F was followed in early 1943 by the "P-38G", with Allison V-1710-51/55 engines that offered no increase in power but some technical improvements, and the older SCR-274N radio. 1,082 P-38Gs were built. The P-38G was followed in turn by 601 similar "P-38Hs", with further updated Allisons with 1,065 kW (1,425 HP) each, an improved 20 millimeter cannon, and a bomb capacity of 1,450 kilograms (3,200 pounds). These models were also field-modified into "F-4B" and "F-5A" reconnaissance aircraft.

There was never a "P-38I". The USAAF didn't use the "I" designation since it looked like a "1".

 

The Lightning In Maturity : P-38J, P-38L

The definitive "P-38J" was introduced in August 1943. The twin booms of previous Lightnings featured a sleek, art-deco streamlining. However, the coolant system that had been housed in the inner part of the wings had proven vulnerable to combat damage and was inefficient anyway, and so engine fit was rethought. The most noticeable feature of the new fit was that the radiators were placed under the prop hub at the front of the booms, forming a "beard" that made the P-38J visibly different from its predecessors. The space left open in the wings was replaced with fuel tanks, further increasing the aircraft's long range. The revised engine fit made cooling much more efficient and improved both performance and reliability.

Late production P-38Js also finally overcame the compressibility problem through the introduction of minor aerodynamic changes. The most significant of these changes was the addition of a set of small dive flaps just outboard of the engines, on the bottom centerline of the wings. With these improvements, a USAAF pilot dived one to a terminal velocity of almost 970 KPH (600 MPH) and recovered in one piece.

Finally, later production of the P-38J was equipped with power-boosted flight controls, making the P-38J one of the first aircraft to have such a feature, and did much to improve the Lightning's roll rate and maneuverability. With a truly satisfactory Lightning in place, Lockheed ramped up production, working with subcontractors across the country to produce hundreds of Lightnings each month. Some 2,970 P-38Js were built.

   LOCKHEED P-38J LIGHTNING:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                15.85 meters        52 feet
   wing area               30.42 sq_meters     327.5 sq_feet
   length                  11.53 meters        37 feet 10 inches
   height                  2.99 meters         9 feet 10 inches

   empty weight            5,797 kilograms     12,780 pounds
   max loaded weight       9,798 kilograms     21,600 pounds

   maximum speed           676 KPH             420 MPH / 365 KT
   service ceiling         13,410 meters       44,000 feet
   range, no drop tanks    1,891 kilometers    1,175 MI / 1,022 NMI
   range, with drop tanks  3,627 kilometers    2,260 MI / 1,965 NMI
   _____________________   _________________   _______________________

The 5,000th Lightning built, a P-38J, was painted fire-engine red, and had the name "YIPPEE" painted on the underside of the wings in big letters. This aircraft was used by Lockheed test pilots Milo Burcham and Tony LeVier in remarkable flight demonstrations, performing such stunts as slow rolls at treetop level with one prop feathered to show that the P-38 was not the unmanageable beast of legend. Their exploits did much to reassure pilots that the Lightning might be a handful, but it was no "widow maker". 

There was a single "P-38K", an experimental version with improved Allisons and wide-chord propellers, but its performance was little better than that of the P-38J, and the next production version was the "P-38L", which was generally similar to the P-38J but featured still more powerful Allison engines with 1,100 kW (1,475 HP) each.

The P-38L was the most heavily produced variant of the Lightning, with 3,923 built. 113 of the total were built by Consolidated-Vultee in their Nashville plant. Lockheed production of the Lightning was distinguished by a suffix consisting of a production block number followed by "LO", for example "P-38L-1-LO", while Consolidated-Vultee production was distinguished by a block number followed by "VN", for example "P-38L-5-VN".

The P-38L was fitted to carry 12.7-centimeter (5-inch) "high velocity air rocket (HVAR)", at first with seven HVARs on pylons beneath each wing but later with ten HVARs on each wing on "Christmas tree" launch racks. Earlier P-38 variants had on some occasions carried triple-tube "bazooka"-type launchers for the M-8 rocket on the bomb pylons, but the M-8 had been a much less effective weapon. The P-38L also had strengthened stores pylons to allow carriage of 900 kilogram (2,000 pound) bombs or 1,140 liter (300 US gallon) drop tanks.

200 P-38J airframes were modified in production to become unarmed "F-5B" photo-reconnaissance aircraft, while hundreds of other P-38Js and P-38Ls were field-modified to become "F-5Es", "F-5Fs", and "F-5Gs". A few P-38Ls were field-modified to become two-seat "TP-38L" familiarization trainers.

Late model Lightning's were delivered unpainted, as per USAAF policy established in 1944. At first field units tried to paint them, since pilots worried about being too visible to the enemy, but it turned out the reduction in weight was a minor plus in combat.

15 P-38Js and P-38Ls were flown by the Nationalist Chinese late in the war, and after the war they also received a similar number of F-5Es and F-5Gs.

The new Lightning's were operated by the US Army Eighth Air Force in Europe beginning in 1943 for long-range escort missions, but did not achieve great success in this role. This was partly because it was harder to fly than a single-engine aircraft and, since it had no engine in front of the pilot to keep him warm, was an "icebox" during high-altitude missions.

The Eighth operated F-5 recon variants with more enthusiasm and success. They were also operated by a Free French squadron, which worked as part of the USAAF Twelfth Air Force, and in fact the French would continue to operate the type up to 1952.

Unfortunately, since F-5s operated alone, when their missions went wrong they generally disappeared without a trace. The noted aviation pioneer and writer Antoine de Saint-Exupery vanished in an F-5 while on a reconnaissance mission over Lyons, France, on 31 July 1944. A French scuba diver found the wreckage of a Lightning in the Mediterranean off Marseilles in 2000, and this wreck attracted interest as there was reason to believe it was Saint-Exupery's.

Despite its mixed career in Europe, the Lightning remained an outstanding success in the Pacific. Freezing cockpits were not a problem in the warm tropics. In fact, since there was no way to open a window while in flight, as it caused buffeting by setting up turbulence through the tail plane, it was often too hot, and pilots would fly stripped down to shorts, tennis shoes, and parachute.

P-38 pilots racked up big scores against the Japanese. Richard Ira Bong and Tom McGuire of the USAAF competed for the top position, a rivalry made interesting by the contrast in personalities of the two men.

Both Bong and McGuire were unbelievably aggressive and fearless in the air. After dogfights, their P-38s would be warped out of shape by overstress. On the ground, they were completely different men. Dick Bong was a modest, quiet, almost shy man, while the egotistical McGuire was "an unpleasant individual with a talent much bigger than he was," as one of his colleagues remembered him.

The famed Charles A. Lindberg, working in the South Pacific for Lockheed as an operational test pilot, where he shot down a few Japanese aircraft with his P-38 while "testing his guns", shared a tent with McGuire. Visitors recalled McGuire ordering Lindberg around, telling him to run errands as though he were a servant.

Bong was rotated back to the States as America's ace of aces, after making 40 kills. He was killed on 6 August 1945, the day the atomic bomb was dropped on Japan, when his P-80 Shooting Star jet fighter flamed out on take-off. McGuire had been killed in air combat in January 1945, over the Philippines, after racking up 38 confirmed kills, making him the second-ranking American ace. Both men were awarded the Medal of Honor.

The seventh-ranking American ace, Charles MacDonald, also flew a Lightning against the Japanese, scoring 27 kills in his famous aircraft, the "Putt Putt Maru".

The P-38 fought all around the Pacific, from the Aleutians to New Guinea to Burma and China. A P-38 is said to have been the first American aircraft to land in Japan after VJ-Day, when a pair of them set down on Nitagahara, with the pilots later claiming they were "low on fuel".

 

Lightning Variants

 

Pathfinders, Night Fighters, The XP-49, & XP-58

The Lightning was modified for other roles. In addition to the F-4 and F-5 reconnaissance variants, a number of P-38Js and P-38Ls were field-modified as formation bombing "pathfinders", fitted with a glazed nose with a Norden bombsight, or a radar "bombing through overcast" nose. A pathfinder would lead a formation of other P-38s, each overloaded with two 900 kilogram (2,000 pound) bombs, and the entire formation would release when the pathfinder did.

A number of Lightning's were modified as night fighters. There were several field or experimental modifications with different equipment fits that finally led to the "P-38M Night Lightning" night fighter.

80 P-38Ls were modified to the Night Lightning configuration, painted dead-black with flash cones on the guns, an AN/APS-6 radar pod below the nose, and a second cockpit with a raised canopy behind the pilot's canopy for the radar operator. The headroom in the back cockpit was limited, and radar operators were preferably of short stature.

The additional external clutter imposed surprisingly little penalty on the P-38M's performance, and in fact it was faster than the purpose-built Northrop P-61 Black Widow night fighter. The Night Lightning's saw some combat duty in the Pacific towards the end of the war.

Lockheed also built two sister designs to the P-38: the "XP-49" and the "XP-58 Chain Lightning".

In the spring of 1939, the Air Corps issued a request for an advanced twin-engine interceptor, to be derived from an existing type and fitted with advanced high-performance engines. Lockheed responded to the request with the "Model 222", which was much like a P-38 except that it had a pressurized cabin and was to be powered by 24-cylinder inline Pratt & Whitney X-1800-SA2-G engines, which were in development and were expected to provide over 1,490 kW (2,000 HP). The Model 222 was to be armed with four 12.7 millimeter and two 20 millimeter guns, and a P-38G was modified to test this armament fit.

The Model 222 won the competition, with the Air Corps ordering a single prototype as the "XP-49" in October 1939. Lockheed proposed that production P-49s be fitted with turbocharged Wright R-2160 Tornado radials with 1,715 kW (2,300 HP) each, which would give the P-49 an estimated performance of 800 KPH (500 MPH) at altitude.

Work on the XP-49 went slowly as Lockheed was caught up in the prewar US military buildup. As development work plodded along, both the Air Corps and Lockheed began to have doubts for various reasons about the powerful engines to be fitted to the aircraft, and so the design was changed to incorporate two Continental XIV-1430-9/11 12-cylinder inverted-V engines with 1,150 kW (1,540 HP) each for takeoff.

Engine availability further delayed development of the aircraft, and the XP-49 didn't take to the air until April 1942. The XP-49 looked much like a P-38, except for increased length and longer nacelles, and in fact the two aircraft shared about two-thirds of their parts. The aircraft was evaluated into the summer of 1943, but the Continental engines were troublesome.

   LOCKHEED XP-49:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                15.85 meters        52 feet
   wing area               30.42 sq_meters     327.5 sq_feet
   length                  12.22 meters        40 feet 1 inch
   height                  2.99 meters         9 feet 10 inches

   empty weight            7,020 kilograms     15,475 pounds
   max takeoff weight      8,505 kilograms     18,750 pounds

   maximum speed           737 KPH             458 MPH / 398 KT
   service ceiling         12,200 meters       40,000 feet
   range                   1,287 kilometers    800 MI / 649 NMI
   _____________________   _________________   _______________________

Some sources claim that the XP-49 had few if any performance advantages over existing P-38 production, others cite a test pilot as saying it "fly rings around the Lightning", but whatever the case the USAAF abandoned all plans to put the XP-49 into production. The single prototype was used for occasional tests, including being dropped from a crane to simulate hard landings, and was finally scrapped in 1946.

The XP-58 actually started life in the spring of 1940 as an advanced escort fighter version of the P-38, with the development at the request of the USAAF. Single-seat and two-seat versions were considered, with the two-seat version fitted with additional turret-mounted armament.

The single-seat version was quickly abandoned, and the two-seat version went through a number of radical design changes, particularly with regards to engine fit. With the outbreak of the Pacific War in December 1941, the project was more or less put on the "back burner", with most of the staff moved to higher-priority projects.

The USAAF then began to flip-flop on their requirements, redefining the XP-58 as a ground attack aircraft, then a bomber, then an interceptor, with a bewildering variety of equipment fits considered. The single XP-58 prototype finally flew on 6 June 1944.

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The XP-58 was a substantially more radical departure from the original P-38 design than the XP-49. While the XP-58 had the general Lightning configuration, nobody could have mistaken it for a Lightning. It was a monster, more on the scale of the Northrop P-61 Black Widow night fighter, and powered by two 24-cylinder Allison V-3420-11 inline engines with 1,565 kW (2,100 HP) each. 

The XP-58 was to mount four 37 millimeter fixed forward-firing cannon and two remote-control barbettes, each with two 12.7 millimeter machine guns, mounted at the rear of the crew nacelle. An alternate forward armament of two 12.7 millimeter machine guns and a 75 millimeter cannon, for breaking up bomber formations, was also considered, but in reality no armament was ever fitted.

   LOCKHEED XP-58 CHAIN LIGHTNING:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                21.34 meters        70 feet
   wing area               55.74 sq_meters     600 sq_feet
   length                  15.06 meters        49 feet 5 inches
   height                  3.66 meters         12 feet

   empty weight            9,070 kilograms     20,000 pounds
   max takeoff weight      17,780 kilograms    39,000 pounds

   maximum speed           702 KPH             436 MPH / 380 KT
   service ceiling         12,200 meters       40,000 feet
   range                   4,830 kilometers    3,000 MI / 2,610 NMI
   _____________________   _________________   _______________________

By the time the prototype flew, the USAAF had completely lost interest in the project, and the flight test program was short and indifferent. A second prototype was never completed, and the one flying example was scrapped after the war. Whether the XP-58 would have been a good idea or not, it still would have been interesting to see what would have happened if it had actually hit something with four 37 millimeter cannon!

 

 

Unusual Lightning Variants

 

There were a number of oddball experimental modifications of the Lightning:

 

 

The Lightning In Twilight

 

The P-38's final report card gave somewhat mixed grades. On the negative side, it was certainly harder to fly than the best single-engine fighters, pilots suffered badly from the cold in northern climates, and its twin supercharged Allison's were temperamental. A good portion of Lightning's lost during the war were brought down by engine difficulties rather than the enemy, and unscheduled engine changes were common.

It did not have a reputation for being a maneuverable aircraft, though it was surprisingly agile at low altitudes. Its real virtues were long range, heavy payload, high speed, fast climb, and concentrated firepower.

Clustering all the armament in the nose meant that Lightning pilots had to be good shots, and Dick Bong would fly recklessly in towards his targets to make sure he hit them, in some cases flying through the debris of his victim. However, the clustered guns also had a "buzz-saw" effect on the receiving end, and made the aircraft useful for strafing as well.

Over 10,000 Lightning's were manufactured in all, and it was one of the few combat aircraft that had been in production at the beginning of the war that was still in production at the end.

* The end of the war left the USAAF with thousands of war-weary P-38s on their hands, rendered obsolete by the jet age. Fifty late-model Lightning's were provided to Italy and operated for several years, and a dozen were sold to Honduras. The others were put up for sale for $1,200 USD apiece to whoever wanted one, and the rest were scrapped.

Lockheed test pilot Tony LeVier was among those who came up with the money to buy a P-38 and run it as an air racer. The Lightning was a popular contender in the air races from 1946 through 1949, with brightly colored Lightning's making screaming turns around the pylons.

F-5s were bought by aerial survey companies and used for aerial mapping. From the 1950s on, however, the Lightning steadily declined, and today only a little more than two dozen exist, with a handful still flying. One particularly pretty example is a P-38L owned by the Lone Star Flight Museum in Galveston, Texas, painted in the colors of Charles MacDonald's "Putt Putt Maru."

One of the most remarkable flying survivors is a P-38 named "Glacier Girl". On 15 July 1942, six P-38Fs and two B-17Es were flying from Greenland to Iceland on a leg of a trans-Atlantic shuttle to Britain when they ran into a blizzard. They turned back to Greenland but the base was socked in, and they were forced to belly in on the Greenland icecap. One P-38 flipped over on landing but none of the aircrew received any serious injuries, and in fact the aircraft suffered very little damage. The aircrew were dropped survival gear and rations and were hauled out by dogsled about ten days later. One pilot threw the keys of his P-38 on the fighter's seat for anyone who wanted to recover the thing later.

The eight aircraft of the "Lost Squadron" forgotten until 1981. Two Americans, an airplane dealer named Patrick Epps JR and an architect named Richard Taylor, were chatting. Taylor owned a Learjet but told Epps he really wanted a P-38. Epps replied that he knew where six were, and said they would be like new. All they would have to do is shovel some snow off them.

They mounted a number of expeditions to find the machines, finally locating them in 1988 with ice-penetrating radar. Epps knew they would be buried in ice, but everyone was astounded when they found the aircraft at a depth of well over 86 meters (250 feet)! This was more than Epps and Taylor expected and they were not able to follow up the matter by themselves. Ultimately the project to recover the aircraft passed on to a Kentucky businessman named J. Roy Shoffner.

A series of expeditions used a hot-water drill to bore down through the ice and reach the aircraft. The recovery crew went down to a B-17 first, which turned out to have been crushed by the weight of the ice, but then they tried one of the P-38s and found it in excellent condition. They melted out a cavern around the P-38, dismantled it, and brought it to the surface in August 1992. 

The P-38F was transported back to the US and was brought back up to operational trim after 50 years in the deep freeze. Although the airframe had suffered some damage under the ice, about 80% of it was still usable. The aircraft was given the appropriate name of "Glacier Girl" and returned to the air on 26 October 2002.

By Greg Goebel


 

The XP-38

 

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XP-38.jpg XP-38Det.jpg

XP-38 LIGHTNING by Larry Lapadura

Larry Lapadura's painting, "XP-38 Lightning", is a commemorative painting celebrating the Lockheed P-38 Lightning's first flight on January 27, 1939 from March Field, piloted by Army Air Corps Wright Field test pilot, Lt. Ben Kelsey.


 

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A One Of A Kind P-38

This one-off prototype was flown only by Kelsey during its brief fourteen day flying existence. The XP-38, AC37-457, crashed on February 11, 1939 at the end of a transcontinental speed dash record attempt from California's March Field to Mitchel Field, Long Island. Upon his unannounced arrival, Lt. Kelsey had to crash land in the Cold Stream Golf Course after his engines probably iced up in the idle setting when he was stuck behind three or four slow flying PB-2A training planes in the pattern. His low airspeed was probably caused by the traffic but perhaps other concerns such as a low speed requirement for flap extension or inadequate brakes contributed. Nevertheless, the engines failed to accelerate on final approach and he had insufficient altitude to glide to the field.

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XP-38

No in-flight photos were taken of the XP-38, so paintings are the sole means to portray this most beautiful aircraft in it's primary setting, the sky. A Lockheed ad of the period, showing the XP-38 (although not labelled as such) was painted by the late Ren Wicks, an ASAA founder. Another Lockheed ad showed a "flying" XP-38 was just a retouched ground photo.

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Early Lockheed ad by Ren Wicks showing the XP-38 prototype.

Kelsey had this to say about the radical design of the P-38: "I don't think any of you will ever appreciate the trail breaking the P-38 accomplished; it was unique in history in many ways. It did more things at the time that set the stage for later on. For one instance, we were somewhat concerned about a 45 pound wing loading because we were buying ones that rarely topped 30 pounds. Looking up aircraft that had been flown at high wing loadings, the only one we had that had any experience was the Sikorsky boat that had all of Long Island Sound to take-off in, making record flights. It had gone up to 45 pound per square foot. Here we were talking about a tactical aircraft that we would want to get over 50 foot obstacles both ways in about 2200 feet with wing loadings fully that high. The elegance of this design was apparent and we were willing to look at it." The 45 pound wing loading was made possible largely through the use of the Fowler flap, first used in production on the Lockheed Model L-14 transport, the "Super Electra," in 1937. Lockheed received a service test production order for thirteen YP-38s within about 60 days of the crash (April 27, 1939).

 

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Lockheed ad from Fortune Magazine showing "in-flight" picture of XP-38. Was just a retouched ground photo.

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1939 painting of XP-38 by Charles H. Hubbell.

Oddly, there wasn't extensive magazine coverage of the XP-38 crash although news services carried February 11th dispatches about the crash; the AP headlined their article, "'Mystery' Plane Crashes At End of Test Speed Hop: Fails to Break Hughes Mark." The AP account was way off the mark insofar as describing the cause of the crash. "Time" magazine carried an article written in their abbreviated style but with reasonable accuracy. Here's a reprint of that short column. From the "TRANSPORT" column of the February 20, 1939 "Time" magazine, page 28.) "Sleek, Fast and Luckless. She was sleek as freshly peeled willow. As overalled mechanics trundled her out for the warm-up at March Field one day last week she gleamed slimly among the bulb-nosed fighters, the potbellied bombers on the Army Air Corps Southern California airdrome. Major General Henry H. Arnold, graying Chief of the Air Corps, surveyed with particular approval her twin engines, Prestone-cooled V-12 Allisons of 1,000 horsepower each, faired trimly into the metal wing. Well he knew that broad beamed radial air-cooled motors, such as the big U. S. engine builders have brought to perfection, could not be used on such a ship without protruding in speed-killing humps on the wing's leading edges, that only the Allison (TIME, Jan. 30) could do the job cut out for the new fighter. When the engines had been warmed up, Lieutenant Ben S. Kelsey, one of the Army's ace test pilots, buckled his parachute leg-straps, climbed into her independent midships compartment (she is twin-tailed) and took off. Half an hour later he landed, and delighted Henry Arnold issued a statement to the press about XP-38, the Air Corps's break from pursuit tradition. The ship, said he, "opens up new horizons of performance probably unattainable by nations banking solely on the single engine arrangement." Kelsey had traveled more than 350 miles an hour in the test. He was satisfied the Lockheed was highly maneuverable, had more than 400 miles an hour in her.

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YP-38 on Ground

XP-38

Day after the test, Ben Kelsey took the ship East, stopped 22 minutes at Amarillo for fuel, lost another 23 minutes at the gas pit in Dayton. When he whipped over Mitchel Field on Long Island, just as the sun was setting, he was seven hours, 45 minutes (elapsed time) out of March Field, 2,400 miles away, and only 17 minutes slower than Howard Hughes's record non-stop transcontinental flight in a racing plane in 1937. Swinging swiftly in a wide arc he squared away for a landing, let down his landing gear. Then came some more of the sort of bad luck that has dogged new Army ships of late. As Pilot Kelsey suddenly realized that he was falling short, he opened his throttles to drag into the field. Without so much as a cough his left engine died. Plowing her wheels through a tree, the XP-38, with right engine throttled, slammed into the sand bunker of a golf course, came to a stop with her right wing torn off, her props hopelessly snaggled, her fuselage twisted (see cut). A passing motorist helped dazed Ben Kelsey from the wreck. He had been only slightly cut. Probably damaged beyond repair was XP-38. But in the Lockheed factory, at Burbank, Calif., were all the drawings, dies and jigs needed to make many more like her. Pilots said the twin-engined pursuit ship had joined the Air Corps." (Caption for photo of wrecked XP-38, "XP-38 Wrecked on Long Island. The twin-engined pursuit ship joined the Air Corps nevertheless.")

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May 1939 issue of Model Airplane News - a timely painting. The story of the XP-38 crash has some weird statements about Lt. Kelsey's condition following the force landing. Note the fanciful paint scheme applied by the great Jo Kotula!

 

 

 

 

 

 

A Joe Ott "Flying Battle Plane Kit" No. 3216 "Lockheed" with 32" wingspan. Not dated but probably from around 1941. The XP-38 shape was used and the box illustration is unmistakably a XP-38, much of it in the same fanciful colors as the Jo Kotula cover. Makes you want to buy that kit! It appears as if the box art was traced from Kotula's cover and rotated a bit. Why is the RH nacelle nose not painted red as the LH?

Exactly two years following the XP-38's first flight, the January 27, 1941 issue of LIFE magazine carried a Lockheed ad which featured a painting of the P-38 and Hudson done by the late Ren Wicks. The P-38 depicted is the XP-38, not the production version YP-38 of the day. I asked Ren why he painted the XP in 1941 and he said that the drawings and information that were given to him by Lockheed were for the XP - a slip up by the art director for the advertising. The detail of the XP-38 from the 1941 ad is shown below.

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The use of XP-38 images in later advertising is a reoccurring theme. The full-page, Curtiss Electric Propeller ad, shown below, is from the Aero Digest of July 1941. The P-38 shown at top appears to be a YP-38 commonly pictured during that era. However, the P-38 in the lower left corner is actually the one-off XP-38 (shown in more detail below also); can you pick out the five or six prominent features that mark this one-of-a-kind prototype? 

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In spite of the XP-38 crash, Kelly Johnson had some enhancements planned for the next prototype. The order for additional P-38 prototypes allowed Johnson to able to incorporate many improvements into the next design. The first YP-38 was rolled out nineteen months later.

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XP-38 by Stan Stokes.

Lockheed was struggling to fill many types of orders and was rapidly growing. The main focus was to produce the Hudson. There were not many available engineers and designers to work on the fledging P-38 project. Lockheed looked to the 1939 contract with Curtis to produce the P-40 as an example. In 1939, there were not many orders for the P-40, and it was basically a break-even proposition for Curtis. Lockheed was informed not to expect many orders for the P-38. Lockheed also had put up most of the money for the first prototype, and the proposition for profit was limited. So as any company would do, they focused on making money. The country was not at war, so there was no immediate need to produce something that would at best break even. In June 1939, Lockheed took over a local distillery building and began to use it for YP-38 production.

Lockheed engineers were following Allison improvements in their V-1710 engine and planned to incorporate the new V-1710-F engine in the YP-38 models. Lockheed started production for the thirteen YP-38s soon after taking over the distillery building. During this time, Bob Gross thought that no more than sixty models would ever be produced. He based his belief on the overwhelming favoritism being placed on bombers than fighters in the military. The military believed a bomber with massive armor and machine guns would not encounter problems with enemy fighters.

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Marshall Headle with YP-38

The XP-38

The YP-38 design was also improved for production ease. The XP-38 was not designed with this mindset, and would be extremely hard to produce in any significant numbers. The new Alison engine was rated at 1150 hp at 20,000 ft. Propeller rotation was changed and reduced downwash onto the wing/centersection/fuselage juncture. This solved the problem of disturbed airflow over the horizontal stabilizer (tail flutter & buffeting). The YP-38 had a designed empty weight of 11,171 lbs., and a designed gross weight of 13,500 lbs. This rose to 14,348 when additional space was allotted for fuel tanks. Lockheed engineers guaranteed a high speed on 405 mph at 20,000 ft.

The YP-38 models began trickling out of the factory and immediate testing was conducted. Marshall Headle, Milo Burcham, Ralph Virden, Jimmy Mattern, and Swede Parker performed initial Lockheed testing. Headle and Burcham teamed up with Dr. F. E. Poole in an attempt to anticipate the many "unknowns" that would be encountered. Working with the Mayo Clinic, procedures were developed to hopefully prevent any problems due to excessive altitudes. Lockheed constructed a special altitude chamber to test new equipment. During this time period, many of the standard pilot equipment were very primitive. Oxygen systems were unreliable, there were no ejection seats, and data recording was only beginning to move from the "knee pad" methods were only a few of the developing techniques. Soon after testing began, Marshall Headle was seriously injured in an altitude chamber accident, which permanently ended his flying career, and led to a premature death.

The last YP-38 trickled out of the factory in May 1941. By this point of production, Lockheed released some of the YP-38s over to the military for additional testing. Pilots from the First Pursuit Group at Selfridge Field, Michigan, were able to perform additional testing. These pilots would form the initial cadre of P-38 pilots during the war. Major Signa Gilkey was one of these pilots who flew the YP-38. During one flight, he decided to perform a limited test dive. Gilkey underestimated the potential speed buildup of the aircraft, and soon built up excessive speeds. He was one of the first military pilots to experience firsthand the problems of compressibility. He was able to recover the aircraft and land safely.

By September 1941, the YP-38s were in a committed program to test compressibility. Test engineers wanted the test pilots to go past 300 mph starting above 30,000 ft. This was not normally done, and many of the test pilots thought the test dives were too ambitious at this early stage. Ralph Virden was committed to fly the tests and took off on November 4, 1941 for a series of test dives. Partially through the testing, an object broke off from the aircraft. The aircraft entered an inverted spin and crashed. Virden was killed. Kelly Johnson would later say, "I was back in my office when I heard Virden's plane screaming towards the plant. That most unusual sound probably resulted from the propellers striking the air at an angle abnormal to the line of flight." Johnson concluded that a spring tab like broke, which caused full deflection (Virden's aircraft was observed to rise sharply prior to the part breaking off). At a speed of 300 mph at 3,000 ft. of altitude, this deflection would cause the airframe to exceed design criteria. Designers were pushing the limits of aerodynamic knowledge and material strength in the quest for maximum performance. Often these limits were exceeded leading to unexpected or tragic events.

The YP-38 was destined to spend the rest of its operational life with dive testing. If the problems with compressibility were not figured out, much of the aircraft potential as a fighter would be removed. The YP-38 proved to be a great step towards operational P-38s during the war. Without the hard work and sacrifice of the Lockheed engineers and test pilots, the P-38 may have never developed into the aircraft it was. It opened the door for many other aircraft which experienced compressibility and other related phenomena, and allowed the engineers and designers to immediately know what exactly was happening and were able to overcome these obstacles much easier.

Engineers and aircraft designers in the 1930's were facing many obstacles when designing high performance aircraft. Unknown phenomena was common. This section will give an overview in some of the problems the early P-38s experienced, and how they were resolved.

In the early stages of development, the P-38 was far more advanced than any other fighter aircraft being designed by the United States. To think that this new aircraft would not encounter any developmental problems would have been naive. In fact, the P-38 would face a serious problem, one that would almost cause its demise.

Kelly Johnson had admiration for the British Spitfire design. He especially liked the smooth, sleek wing design. The Spitfire was one the finest fighters during the war, and could hold its own against any other fighter in production. One problem was with the range. Spitfires had limited range, and the specifications for the new P-38 fighter called for an aircraft with good range capabilities. In order to accommodate the design specifications, the P-38 had a thick wing. This design allowed for larger internal fuel tanks to be installed within the wings, and would also allow for a sound structure to attach either external tanks or bombs on. The solid wing on the P-38 created tremendous lifting characteristics. One other characteristic was that is also allowed the aircraft to experience compressibility.

Compressibility occurs what the P-38 entered dives stated above 20,000 ft. The airflow would be "splashed" over the leading edge of the wing instead of the usual smooth airflow. The splashed air would approach the sound barrier (not the aircraft itself, but rather the speed of the air flowing over the wing), thus causing a shockwave effect on the trailing edge. This would render the controls inoperable, leaving the pilot without any control of the aircraft. Two possibilities would then ensue. Either the aircraft would slow as it descended into denser air closer to the ground and the pilot would regain control and pull out of the dive. Or in some cases, the P-38 would simply disintegrate. Many pilots would lose their lives when they inadvertently entered a steep dive, or when performing dive tests. More importantly, this problem would affect the performance of early operational versions of the P-38, and also caused many rumors that plagued the P-38 early in the war.

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Tony Levier described compressibility as, "It resembled a giant phantom hand that seized the plane and sometimes shook it out of the pilot's control." George Gray wrote in a history of the NACA, "The behavior was new to pilots, terrifying, baffling. Several men, in putting this two-engine fighter through its diving maneuvers, underwent the experience: A sudden violent buffeting of the tail accompanied by a lunging and threshing about of the place, as though it were trying to free itself on invisible bonds, and then the maddening immobility of the controls, the refusal of the elevators to respond to the stick." Use of elevator trim would sometimes bring the P-38 out of a dive before destruction. Sometimes the P-38 would begin to tuck under and begin to come out of the dive upside-down. Levels of stress on the airframe were staggering, and the fact that the aircraft would come out of the dive at all was proof of its strength. Hal Hibbard described the compressibility problem as, "…the air tends to be 'splashed' by the leading edge of the wing more of less like the prow of a boat at high speed in the water. As one approached the compressibility range, the air is throw to violently up and down the leading edge that is does not have a chance to flow over the wing in the proper manner."

Compressibility encounters go as far back as the YP-38 testing. The XP-38 was never tested enough to encounter compressibility (one further reason why the program was set back at least 2 years). If the XP-38 had encountered it, the problem may have been resolved very early in testing. The initial test flights of the YP-38 were very successful, and no problems were encountered. Prior to the testing of this aircraft, flying at 25,000 was rare, and flying at 40,000 was unheard of. Dr. F. E. Poole and Lockheed test pilot Marshall Headle worked closely with the Mayo Clinic to develop methods to cope with potential serious problems when operating at extreme altitudes. Lockheed constructed a new altitude chamber to test new equipment. The testing during this period was hazardous, simply because this type of testing was not normally done. Also, when testing the aircraft, there were no ejection seats, oxygen systems were unreliable, and data recording was just beginning to move beyond the "notepad on knee" system. The first setback was when Marshall Headle was seriously injured in the altitude chamber, which ended his flying career and lead to a premature death.

YP-38s would continue to trickle out of production, with the last one completed in May 1941. YP-38s were sent to various groups for additional testing. Pilots from the 1st Pursuit Group, stationed at Selfridge Field in Michigan, received the assignment for testing. The P-38 was finally forming a cadre of pilots. Major Signa Gilkey was one pilot who performed some testing on the YP-38. He decided to perform a test dive, and wanted to ease it into the dive conserving as much speed as possible. It accelerated beyond his expectations and encountered severe tail buffeting when he approached 400 mph. He described the sensation of the aircraft wanting to continue diving onto its back, and not wanting to pull out of the dive. Gilkey experienced classic compressibility problems, as well as a tail-buffeting problem. The buffeting problem was easily resolved through aerodynamic testing, but the problem of compressibility was cause for concern.

Military officials called for the P-38 design to include tail weights to prevent tail flutter. Kelly Johnson wrote Report No. 2414, which stated that the tests on the weight balances indicated no positive effects. The weights did not prevent or enhance the performance of the aircraft in any significant way. Johnson would say off the record that the weights only killed several pilots who came in contact with them while bailing out of the aircraft. Many changes were tried in order to address the compressibility problem. Lockheed designers re-skinned the elevator and stabilizer using thicker aluminum, modified the turbo exhaust hoods to reduce the intake area and to potentially change the airflow pattern, and redesigned the canopy shape and gondola skin roughness. Nothing they tried solved the problem.

Testing of the YP-38 was continuing throughout 1941. By September, the YP-38 was committed to testing compressibility problems. Test engineers wanted pilots to go past 300 mph above 30,000 ft. Lockheed test pilots Milo Bircham, Jimmy Mattern, and Ralph Virden were given the assignment for testing the YP-38 in the specified dive tests developed by Lockheed engineers. Bircham and Mattern had some reservations, but were committed to developing the P-38. Virden, on the other hand, was absolutely committed to testing the aircraft to the degree specified by the engineers. On November 4, Virden tested a single YP-38, which had new spring tabs at each end of the control surfaces. The tabs were supposed to increase leverage to assist the pilot overcoming tremendous loads while pulling out of a dive. By this point in the testing process, Lockheed was in high spirits, and extremely close to solving the buffeting problem. Virden lifted off and began his appointed tests for the day. While performing tests, pieces of the aircraft were observed breaking off, and witnesses claimed the sound of the aircraft was drastically different. Virden's aircraft went into an inverted spin, and crashed. Virden was never able to get out and was killed. Kelly Johnson stated, "I was back in my office when I heard Virden's plane screaming towards the plant. That most unusual sound probably resulted from the propellers striking the air at an angle abnormal to the line of flight."

Designers were pushing the limits of aerodynamic knowledge and material strengths in their quest for performance, often exceeding limits of their own ability to predict outcomes from their experiments. This resulted in a high degree of risk, and a slow development rate. Johnson concluded that Virden's crash was a result of a spring tab operating link. The faulty link caused the tabs to operate at full deflection (which were most likely the objects seen breaking off the aircraft). While at 3,000 and traveling at 300 mph, it would far exceed design criteria.

Kelly Johnson would issue a report early in 1942. In the "Study of Diving Characteristics of the P-38", Johnson would state that at a critical airspeed, which varies in altitude, a certain condition exists which causes problems with the airflow. The airflow over the surface area of the wings would separate to produce a special form of stall. At higher speeds, flow separation spreads over the upper surface, and the aircraft tends to be nose-heavy due to a shift in the center of lift. This caused a loss of pitch control. Lockheed engineer Phil Coleman originally specified a dive test plan as early as 1940. He stated that vertical dives should be initiated at 35,000 at modest power settings. The dive would continue until reaching a constant speed at 16,000 ft., and would continue until 13,000 ft. The pilot would then execute a 3 - 4 'g' pullout. The pullout should be completed at 7,000 ft., and should never exceed 570 mph.

Most early combat operational models would suffer from the compressibility problem. However, the problem was not experienced in all theaters of operation. The P-38 did not have compressibility issues while operating in India, the Mediterranean, or in the Pacific. This was primarily due to the nature of combat. In these areas, combat rarely took place above 25,000 ft., and compressibility would not occur if a dive was initiated below 25,000 ft. In Europe, combat operations were normally conducted at high altitudes. Soon, German pilots knew if they were in a bad situation, they could easily dive to safety. The P-38 would be able to dive faster than German fighters, but P-38 pilots were probably more scared of a high-speed dive than enemy fighters.

After extensive testing, the answer to the problem was the use of a dive flap (or brakes). These flaps would be attached to the main spar under the wing. This would offset the loss in lift while in high-speed dives, and would allow the pilot to remain in control throughout the dive. Test pilots Tony Levier and Milo Bircham began a series of dive tests with the flaps. Lt. Benjamin Kelsey was sent by the Air Corps to evaluate the progress of the dive flaps. He took the modified P-38 and proceeded to enter the dive. He had problems engaging the flap as he was beginning his dive. While in the dive, he experienced normal compressibility problems because the flaps were not activated, and the violent thrusts sheared the tail off from the main structure. Kelsey was able to bail out and only sustained a broken ankle. The aircraft was totally destroyed. Another test P-38 would not be fitted with dive flaps for a few months.

Finally, another test P-38 was fitted with the dive flaps and testing was resumed. The Air Corps wanted Lockheed to test the aircraft with 2,000 lbs. of more weight and to start dives at 35,000 ft. The extra weight would cause additional acceleration of the aircraft during its dive, and would approach the critical Mach number sooner. This would be even more hazardous than before. Levier and Bircham resumed testing and would start at a 45-degree dive, and increase each test dive an additional 5-degree until they encountered problems. Levier was the first to encounter problem while using the dive flap. He was in a 60-degree dive, and began having problems when we reached 31,000 ft. The aircraft began to get away from him, even with the flaps deployed. Levier was fighting the aircraft to prevent it from tucking under itself as if it were in a regular dive. He decided to ride it out to see what would happen. He began his recovery at 20,000 ft., but he would not really begin to regain control until he was at 13,000 ft. The instruments registering the strain on the airframe were all over the 100% limit load. Bircham eased it back to the base without putting further stress on the aircraft. This was the evidence they needed to prove the flaps would hold up under an extreme dive, and not lead to disaster like many P-38s prior.

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Swordfish P-38

A typical dive of the P-38 from high altitudes would always experience compressibility. Starting from 36,000 ft., the P-38 would rapidly approach the Mach .675 (445 mph true airspeed). At this point, the airflow going over the wing exceeds Mach 1. A shockwave is created, thus breaking up the airflow equaling a loss of lift. The shockwave destroys the pressure difference between the upper and lower wing, and disrupts the ability for the aircraft to sustain flight. As the lift decreases, the airflow moving back from the wing also changes in its form and pattern. Normal downwash aft of the wing towards the tail begins to deteriorate. The airflow across the tail shifts from normal to a condition where there is now a greater upload, of lifting force, on the tail itself. With the greater uploading force applied to the tail, the nose of the aircraft wants to nose down even more, which creates a steeper and faster dive. As the aircraft approaches the vertical line, it begins to tuck under and starts a high-speed outside loop. At this point, the airframe is at the greatest point of structural failure. When the angle of attack increases during the dive, it also increases for the tail. The resulting effect is that the pilot cannot move the controls because tremendous force is required to operate the aircraft. The pilot is simply a passenger during this period. Shockwaves become shock fronts, which decrease the lift no matter what the pilot tries to do. Instead of smooth airflow over the wing, it is extremely turbulent, and strikes the tail with great force. The aircraft can only recover when it enters lower, denser atmosphere lower to the ground.

The solution to the problem was in understanding that the speed of sound changes with the altitude. At sea level, it is 764 mph, while at 36,000 ft. it is 660 mph. An aircraft moving at 540 mph at 36,000 ft. is much higher in the compressibility zone. The same speed at sea level results in the aircraft being exposed to lower effects of compressibility, and will respond to pilot controls. The dive recovery flap was a solution to this problem. In the ETO, German pilots would dive out of trouble because they knew the P-38 pilots would not follow. This greatly reduced the effectiveness of the aircraft in normal battle conditions. The NACA tested the flaps in high-speed wind tunnels at the Ames Laboratory. They tried several locations before discovering that when the flaps were positioned just aft of the trailing edge of the wings, it showed definite improvements. The flaps were finally positioned beneath the wings outboard of the booms, and just aft of the main structural beam. The pilots had a button on the yoke, and would simply activate the flap just prior to entering a dive.

While the P-38 design was starting to prove itself in testing and combat, one underlying problem still existed. Compressibility was still a major obstacle in the performance of the P-38, and it led to many rumors and myth about the flight characteristics. One prototype P-38 was modified for dive testing. An older P-38 E was the aircraft used for this experimentation. The forward gondola section was moved forward by thirty inches, and the cockpit was move forward by thirty-six inches. The cockpit flight controls were the same, but there was room behind the pilot for a co-pilot/observer/test engineer. This modified P-38 E "Swordfish" first too flight on June 2, 1943 and was immediately put into extensive dive tests. The tests would have limited results, but this design led into another use for this type of P-38.

Click on Picture to enlarge

AAF training before Pearl Harbor was only designed to train between 12,000 - 13,000 pilots each year. After the attack, plans were changed and the numbers were increased significantly. However, the problem was that the government was unprepared for any armed conflicts, and pilots were being forced into the P-38 without adequate training. There were no twin-engine trainers available, but when the British balked at purchasing the Model 322 Lightning I fighters, they were employed as trainers. They were basically stripped down models of the P-38, but they were still rather advanced for the average trained pilot taking the controls for the first time. Johnson envisioned the P-38 Swordfish to be used to take pilot trainees along for demonstration flights with an experienced pilot at the controls. This would dispel many rumors and raise confidence in inexperienced pilots. Lockheed test pilot Jimmy Mattern was sent on tour with a Swordfish version of the P-38. He performed maneuvers that were normally feared by the recruits, such as rolling into a "dead" engine and many low-level aerobatics. After five months of training sessions, P-38 accident rates dropped from 6.5% to 1.5%. Mattern would receive the Civil Medal of Merit for his actions, which saved the lives of many recruits. Once again, the P-38 demonstrated its versatility and value to the Allied cause.

 

 

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