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.
P-58 views, from patent
documents
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.
