Conquering the Sky!

Air Classics, Jun 2005 by O'Leary, Michael

BUILDING THE LIGHTNING: AN INSIDE LOOK AT THE COMPLEX STRUCTURE OF THE P-38 / PART THREE

VINTAGE ADVERTISEMENTS COURTESY SCOTT BLOOM

The P-38L (Model 422-87-23) was the final production version of the Lightning, and it was built in two blocks. Let's examine what was underneath the aluminum skin of this fighter. Power came from Allison V-1710-111/-113 engines which had a war emergency rating of 1600-hp at 28,700-ft and a military rating of 1475-hp at 30,000-ft. Lockheed built 1290 L-1-LOs, which were very similar to the J-25-LO. A stunning 2520 L-5-LOs were also constructed, and these aircraft had submerged fuel pumps and provisions for underwing rocket launchers as well as strengthened center section pylons for 2000-lb bombs. With production rising at Lockheed, a license agreement was reached with Vultee in Nashville, Tennessee, to build P-38s - starting with a batch of 2000 P-38L-5-VNs - but production delays saw just 113 aircraft completed by VJ-Day with the remainder being swiftly canceled.

With the P-38L, the General Electric B-33 turbosuperchargers were mounted in the tup of each forward boom at station 207, and were attached to the center section rear shear beam. Air entering the system through scoops mounted on the outboard side of each boom below the wing was rammed into the impeller section of the turbosupercharger, where it was compressed. The compressed air then passed through a duct to the intercooler, and then to the carburetor.

The air induction system controlled the intake, flow and temperature of the air from the intake scoops to the carburetors. A closed system of cuts, starting with the boom-mounted intake scoops, controlled and routed the air flow.

From the scoops, the air went through the air filter (if in operation) through the compressor of the supercharger, and through pressure-tight ducts to the intercooler. The intercooler was of the core type, and was equipped with electrically-operated flaps. Compressed hot air from the turbosupercharger passed around the tubes of the cooling element and was cooled sufficiently to make it suitable for engine operation. From the intercooler, the air passed by pressure-tight ducts to the carburetor.

An auxiliary system of scoops and ducts was provided to conduct cooling air to various sections of the engine. Air was directed to the spark plugs, magnetos, distributors and to the cap baffles of the turbosupercharger. This cooling air remained in a free state, and escaped to the outside atmosphere after use.

Exhaust manifolds from the cylinder banks converged in a "Y" aft of each engine, and a shrouded tail pipe carried exhaust gases from that point to the supercharger nozzle box. Gases passed through the supercharger and out the wastegate, after driving the turbine bucket wheel. The latter was mounted at opposite ends to the compressor impeller on the same shaft.

The empennage of the P-38L consisted to two empennage booms, two vertical stabilizers, two rudders and tabs, one horizontal stabilizer and one elevator and tab. The horizontal stabilizer tips were interchangeable, right and left, and were attached to the outboards sides of the empennage booms. The elevator was made of one panel and attached to the horizontal stabilizer by ball-bearing hinges. The operating cables actuated a torque tube in each empennage boom. The torque tubes were fastened to the elevator by screws.

The elevator tab was located on the center line of the P-38L, in the trailing edge of the elevator. It was attached to the elevator by a hinge fitted with a corrosion-resistant steel hinge pin, and was connected to the actuating unit in the horizontal stabilizer hy a push-pull tube. A clip at the left end of the elevator secured the tab hinge pin. The inboard ends of the elevator torque tubes were carried in bearings on the stabilizer rear spar. The torque tube balance arm, attached to the outboard end of the tube by two taper pins, contained a bearing that slipped over a pin to the empennage boom. The arms extended forward, and to them were fastened the control cables and the balance weights.

The rudders were constructed in two sections, upper and lower, and were interchangeable, right and left. Rudders were attached to the vertical stabilizer by ball-bearing hinges, and to the torque tubes and to each other by screws. A counterbalance extended forward of the hinge line of each section. The rudder tab was attached to its rudder by a hinge, with a corrosion-resistant steel hinge pin, and was connected to the actuating unit by a push-pull tube. A clip on the rudder at the lower end of the upper rudder secured the hinge pin.

The rudder torque tubes, bearings, brackets and arms were assembled as units, and were attached to the vertical stabilizers by bolts. The control arm projected outboard from each tube, and connected by a push-pull tube to the walking beams in the boom. The empennage boom consisted of two parts, forward and aft, which were joined at boom station 430. The empennage boom formed a tail cone to the aft beam, the tail cone fairing to a trailing edge flush with the horizontal stabilizer tip, and with the elevator when it was in neutral position. The horizontal stabilizer tip was attached to both fore and aft sections.