How the Designer of the SR-71 Created an American Ace-Making Fighter
When walking around the museum, it’s easy to think of the aircraft of different eras as existing almost in different worlds from each other. But when I talk to visitors about one of our most popular aircraft, the Lockheed SR-71 Blackbird, they are always amazed to find that it is deeply connected to one of the greatest World War II fighter planes, the P-38 Lightning.
The SR-71 Blackbird is one of the most awe-inspiring aircraft to ever fly in the United States’ inventory. Though its design can be traced back to concepts as early as the late 1950s, its combination of sleek curves and sharp angles looks futuristic even 60 years later. The Blackbird is known for its high-altitude (well over 80,000 feet) and extremely high speeds (over three times the speed of sound, over 2,000 miles per hour). It still holds many world records for top speeds of piloted, air-breathing airplanes. The lead designer behind this technological marvel was Lockheed engineer Clarence “Kelly” Johnson.
But long before the Blackbird was a gleam in Johnson’s eye, he co-led design efforts on another high-speed, high-altitude airplane that became one of the most effective U.S. fighters of World War II. The Germans allegedly called it the “Fork-Tailed Devil,” American ace fighter pilot Major Jack Ilfrey called it “a beautiful monster.” The U.S. Army Air Forces called it the P-38 Lightning.
The Art of Interception
Johnson made a name for himself as early as 1933 when, as a student at the University of Michigan, he improved the aerodynamic design of the Lockheed Model 10 Electra by incorporating a twin-tail design—a feature that became a hallmark of Lockheed products for decades after. Around the same time, in 1934, 1st Lt. Benjamin Kelsey became the project officer for fighter aircraft development in the Army Air Corps. Interested in the contemporary concept of a bomber-destroyer aircraft, Kelsey’s office issued a proposal for a high-speed, heavily armed fighter with the primary mission of intercepting and destroying high-altitude enemy bombers. Lockheed submitted a design—primarily done by Johnson—which just barely lost to Bell’s entry, the XFM-1 (Fighter-Multiplace) Airacuda. Although one squadron of Airacudas eventually became operational, the five-crew dual-engine pusher aircraft experienced a myriad of technical problems. Its failure was one factor among others that convinced Kelsey, who was fond of Johnson’s proposal, that smaller, single-seat fighter designs might be more effective for the mission of intercepting enemy bombers.
Kelsey worked with Lieutenant Gordon Saville, who was on the Army Board for aircraft procurement. Both men desired a fighter with more engine power (up to 1,500 horsepower, well beyond that of the XFM-1) and up to 1,000 pounds of armament, which was significantly higher than the 500 pounds called for by American pursuit planes of the mid-to-late 1930s. In February 1937, Kelsey issued a circular proposal for a single-seat version of his interceptor concept. Keeping to that ideal, the proposal called for a minimum speed of 360 miles per hour and specified the use of the powerful Allison V-1710C engines incorporating new General Electric turbosuperchargers for high-altitude performance.
Six companies were invited to submit designs: Boeing, Consolidated, Curtiss, Douglass, Vultee, and Lockheed. With most of Lockheed’s small engineering staff focused on other projects, the new fighter, referred to as the Model 22, was co-designed by Johnson and the company’s chief engineer Hall Hibbard, with additional help from Willis Hawkins and James Gerschler. Johnson considered six potential designs, including pusher engines, a dual pusher-puller concept, a twin fuselage with the cockpit on the left side, and a design placing the engines in the center with extended shafts leading to wing-mounted propellers.
Looking back years later, Johnson recalled that the design process had been a simple “logical evolution” driven by the proposal’s requirements. The Allison 1710 engines plus the turbosuperchargers made for long assemblies, and the proposal also called for a retractable tricycle landing gear. As Johnson described, “By the time we had strung all of that together we were almost back to where the tail should be. So we faired it back another five feet and added the tail. . . . [T]hat produced the characteristic twin-tailed airplane.” This simple approach of evolving a design logically from essential mission requirements marked Johnson’s career, including the later process of designing the dual-engine twin-tailed A-12 that evolved into the SR-71 Blackbird. That plane, also known for pushing the boundaries of speed and altitude to new limits, was the result of twelve iterations of evolved designs and the only one that maximized all the requirements of speed, altitude, range, and stealth characteristics. Both the Model 22 and SR-71 design processes also pointed to what Johnson’s successor and close friend Ben Rich recalled as Johnson’s “fanatical” belief “that an airplane that looked beautiful would fly the same way.”
Lightning in the Sky
The first flights of the XP-38 were anything but beautiful. Kelsey himself took the controls, but before it even got off the ground, the brakes failed, and on the first flight, the flaps failed. After addressing these issues and other minor setbacks, on February 11, 1939, Kelsey flew the plane from March Field in Riverside, California, to Wright Field in Dayton, Ohio, after a refueling stop in Amarillo, Texas. The XP-38’s airspeed on that flight averaged 360 miles per hour. In contrast, two years prior, Howard Hughes had set a cross-country speed record of seven hours, twenty-five minutes, averaging 327 miles per hour in an H-1 racer. After landing in Ohio, the XP-38 looked poised to beat that record. Meeting Kelsey at Wright Field, Army Air Corps Major General Henry “Hap” Arnold instructed Kelsey to continue to Mitchell Field in New York to go for the record. While approaching Mitchell Field, the XP-38’s engines experienced icing and lost power. Despite Kelsey’s efforts, the prototype crashed into treetops before skidding through a golf course. Kelsey was unharmed but the plane was destroyed. Despite missing the runway by about 2,000 feet, he had still made the record time of seven hours and two minutes. An impromptu speed record attempt in a prototype had beaten Hughes’ carefully planned record with his highly calibrated racing plane.
Pushing the boundaries of speed and setting records was a hallmark of Johnson’s work at Lockheed. Similar to the XP-38, the A-12—which later evolved into the SR-71 Blackbird—experienced similar issues in its early days. The first test flight of the A-12 in 1962 experienced dangerous wobbling before test pilot Lou Schalk brought it down into a dry lakebed. The SR-71 later set its own cross-country record in 1990, shooting from Los Angeles to Washington, DC, in one hour and four minutes.
The P-38 became one of the most versatile aircraft of World War II. The top two highest scoring American ace pilots of all time, Majors Richard Bong and Thomas McGuire, achieved all of their aerial victories in P-38s. Of the top eight highest scoring U.S. Army Air Forces aces in the Pacific Theater (those with 20 or more victories), seven flew P-38s. The Lightning was the third highest-scoring aircraft in the war in terms of aerial victories (only the P-51 Mustang and F6F Hellcat had higher totals). The P-38’s high speed, exceeding 400 miles per hour, combined with its long range (up to 2,500 miles with extra fuel tanks) and its ability to take damage and stay in the air made it especially useful in the mission of photoreconnaissance. Trading out the guns for cameras, the photo-recon model of the P-38 was named the F-5. Although Johnson had not set out to make the P-38 a reconnaissance plane, his emphasis on pushing the boundaries of speed and altitude made him adept at designing planes for that role. In that sense, the SR-71 Blackbird, his crowning achievement in a long tradition of high-speed reconnaissance planes, dated back to his work on the P-38.
Of course, no aircraft is the work of one person. Both the P-38 and the Blackbird, as well as all the other aircraft created under Johnson’s tenure, were collaborative efforts with teams of engineers, designers, manufacturers, scientists, and test pilots. But Johnson did leave his fingerprints on these planes, creating a legacy of twin-tailed airplanes that earned a powerful place in aviation history and memory.
Michael Hankins is the curator for U.S. Air Force History at the Smithsonian's National Air and Space Museum.