Lightning From the Ground Up
Lockheed's P-38 Lightning
by Jeff Ethell
Copyright © 1993 by the Confederate Air Force and Jeff Ethell. All rights reserved.
In February 1937 the U.S. Army Air Corps asked the American aircraft industry to submit designs for an experimental pursuit having "the tactical mission of interception and attack of hostile aircraft at high altitude". Specifications called for a minimum true air speed of 360 mph at altitude and a climb to 20,000 feet within six minutes.
In essence the Air Corps was asking for a major breakthrough in performance since there were no engines of sufficient power to produce the expected results. 1,600 horsepower would be necessary and the only engine coming close to that kind of power was General Motors' small Allison Division V-1710-C8, which in February 1937 had yet to be tested at 1,000 hp.
One of the solutions envisaged taking two of the Allisons and building a fighter around them; the other was to reduce the requirements and challenge the designers to refine an airframe to utilize every bit of the Allison's power. That there was some freedom to pursue almost any course of action can be laid at the feet of the officer in charge of Wright Field, Ohio's Pursuit Project Office, Lt. Benjamin S. Kelsey. As he later recalled, "We had to find a name that kept people from telling you what should go into the spec, a name that nobody was familiar with or could relate to. We came up with 'interceptor'. Of course it was a fighter in mission but we told these guys that just so we could develop what we needed in a fighter."
Lockheed's Model 22, later the XP38, and Bell's XP-39 were entered into the competition. The Lockheed project was certainly the more radical approach to the problem, resulting in an airplane 150 percent the size of the normal single engine fighter. Clarence L. "Kelly" Johnson designed a twin-boomed, twin engined aircraft that was quite sophisticated. The two large propeller discs offered increased efficiency for the horsepower being generated and the resulting larger wingspan gave better high altitude performance. The guns would fire down the center line and single engine returnability resulted.
Bell Aircraft took the other approach as Larry Bell and Bob Wood designed a fighter with an engine behind the cockpit over the aircraft's center of gravity. The result was a machine 20 percent lighter through placing the main landing gear on the main spar of the wing.
Air Corps contract 9974, dated June 23, 1937, authorized Lockheed to build one XP-38, USAAC serial number 37-457. The Bell XP-39, AAC serial number 38-326, was ordered on Oct. 7, 1937.
Construction of the XP-38 began in July 1938 and it was fitted with the Allison C-9 Model (V-1710-11/15), rated at 1,090 hp. Its right engine turned "backwards" (clockwise viewed from the front), thus countering the effects of propeller torque. It would weigh more than 15,000 pounds loaded. The aircraft combined the latest technological innovations: tricycle landing gear, very high wing loading, Fowler flaps for good low-speed handling, butt joints and flush riveting of the skin which would share flights loads with the interior structure, a bubble canopy and metal covered control surfaces.
The XP-38 was completed in December 1938, then disassembled and loaded on three trucks, covered by canvas, and taken to March Field, California from Burbank during the early morning hours of New Year's Day 1939. Ben Kelsey began taxi tests on Jan. 9 and made the first flight Jan. 27 1939 after delays due to the problems with the brakes. The aircraft was an immediate success and came well within projected performance parameters.
After about five hours total flying time the aircraft was scheduled for delivery to Wright Field, with the possible continuation of the flight to Mitchel Field, New York. On Feb.11, Kelsey took off from March, refuelled at Amarillo, Texas, and landed at Wright Field averaging 360 mph, true air speed at cruise power. Chief of the Air Corps, General Henry H. "Hap" Arnold, was waiting for Kelsey at Wright and the two discussed going to Mitchel. Arnold thought a complete transcontinental dash to make some headlines and prove the U.S. still had a top notch aircraft industry would be beneficial to Air Corps funding in Congress.
Kelsey recalled the last leg: "Descending into Mitchel, I think I probably picked up carburetor ice. This was a problem that had not been solved there wasn't enough heat available via the superchargers at low rpms to handle carburetor ice. I had the throttle way back to lower the flaps and then since I was faced with a landing without wheel brakes (having used them up for the Amarillo and Dayton stops - they simply weren't designed to last on such a big airplane). I had to drag it in under power at low speed."
"The flap problem and the brake problem were just waiting on one additional problem lack of power at a critical time - to produce disaster. As I attempted to ease-in power, the engines failed to respond. Both continued to idle nicely but wouldn't accelerate. I was low and slow on final, in landing configuration. Without power, there was nothing I could do to add a single inch to the approach. I struck the ground short of the runway. The aircraft was a total loss; I was uninjured."
Arnold took Kelsey to Washington the day after the crash to tell four or five top level people about the new XP-38, how fast it was, how nicely it handled. Within 60 days Lockheed had a contract for 13 service-test YP-38s. This would not have been possible had the XP survived since it would have been necessary to validate all its performance estimates with a prototype airplane full of bugs. The order for 13 service-test YP-38s was Air Corps Contract 12523 dated April 27, 1939, but the first YP did not fly until Sept. 16,1940 and the last one was not delivered until eight months after that. The P-38 was the sweetheart of Kelsey's flying career. He saw it through most of its teething pains, including its bout with compressibility, Atlantic ferry and combat.
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