P-58 Chain Lightning

One of the most ill fated American aircraft programs of World War II, Lockheed’s XP-58 Chain Lightning was a potentially formidable design that nonetheless enjoyed none of the success of its predecessor, the P-38. The genesis of the XP-58 project dates back to early 1940, when Lockheed received the Army Air Force’s permission to sell the P-38 to Britain’s Royal Air Force. As part of this deal, the company agreed to develop, as a private venture, a larger version of the Lightning for American use. Although not yet an active combatant, the United States was anticipating eventually having to enter the fight against Germany, a fight that might have to be conducted from the continental US if Britain fell to the Axis. This led to much attention being focused on aircraft able to conduct very long-range operations, one of which would be the new Lockheed design.

Early plans called for an aircraft that was basically a “big P-38″, to be built in both single and two-seat models. However, this concept soon fell aside, and what eventually took shape on the drawing board was quite different. The Chain Lightning had the same basic planform as the P-38, but was really a completely new design. The XP-58 was more than twice as heavy as the P-38J, and had wingspan nearly twice as wide. Whereas the Lightning’s wings had dihedral from tip to root, those of the XP-58 had dihedral only on the outer sections. The center fuselage pod was also significantly larger to accommodate a second crewmember, whose task would be to operate a pair of turrets that provided rearward defense.

In contrast to the wartime urgency that spurred other designs to make the jump from blueprints to the hardware stage in record time, progress on the Chain Lightning was comparatively glacial. Much of this lack of progress can be attributed to the troubles encountered in developing a suitable powerplant. Originally, Continental IV-1440s were specified, but Pratt & Whitney XH-2600s were later substituted when the -1440 program was canceled. This arrangement was to be short-lived, when the XH-2600 was itself canceled shortly afterward. Wright’s R-2160 Tornado engine was then selected; this 2,350hp powerplant was to give the Chain Lightning a top speed of around 450mph at altitude.

By the fall of 1942, the danger of England succumbing to the Germans had essentially passed. This meant that the Chain Lightning would not be needed for its original mission, but rather than stop the program, the XP-58 was instead recast as a low level heavy attack aircraft fitted with a 75mm cannon to kill tanks. The new role did not last long, as Beech’s A-38 looked to fill this need better. Thus, the Chain Lightning was recast back to the high altitude role as a bomber destroyer, retaining the 75mm cannon. An alternative armament fit would be four 37mm weapons, which would give the XP-58 a very potent punch against even large aircraft.

Progress on the XP-58 remained extremely slow; although the prototype airframe was nearly complete by the early fall of 1942, problems with the Tornado engines stalled the overall effort. Finally, by early 1943 it was decided to scrap the Tornado and use yet another new engine, the Allison V-3420. Rated at 3,000 hp, the -3420 was actually a double engine, being comprised of two V-1710s turning a common crankshaft. By this time, Lockheed had also restarted work on a second XP-58 that had earlier been suspended. The XP-58 finally flew on June 6, 1944, but events taking place on that date half a world away in Normandy guaranteed that this achievement would remain obscure. Although the Chain Lightning had finally taken to the air, there was no hope that the program would progress much farther. Conceived of in the darkest days of the war, the XP-58 was outmoded by the latest piston-engined types, to say nothing of the P-80 jets that were starting to come off Lockheed’s own production lines. By this time, the need for long-range fighters was re-emerging, now driven by the need to conduct very long duration flights over the Pacific. However, the Chain Lightning’s time had come and gone before it ever flew, and new designs such as the Twin Mustang were better suited to the new requirements.

By the fall of 1944, the XP-58 had been transferred to Wright Field for testing, but this was really the end of the road for the Chain Lightning. Although credited with impressive handling, the prototype suffered from turbocharger problems, and service equipment such as the armament and pressurization system were not installed. Although the second aircraft was over half-completed, it was finally canceled for good, and solitary flying example was later relegated to duty as an instructional airframe before being broken up for scrap. Bibliography:

Bill Norton U.S. Experimental & Prototype Aircraft Projects: Fighters 1939-1945 p.126: cutaway of the XP-58 fuselage pod