Machine of the Month: P-47 Thunderbolt

Factfile

• The Thunderbolt was the first USAAF single-engined fighter to exceed 400mph in level flight.
• P-47Bs entering squadron service with the 56th FG in early 1942 were state of the art, and had exceptional high-altitude performance due to the aircraft’s massive turbosupercharger. However, the B-model was not yet combat ready, with the 56th spending most of 1942 conducting operational testing that identified and fixed the problems afflicting the aircraft prior to the Thunderbolt being declared operational for service overseas.
• While the P-47 was fast and packed a considerable punch with its battery of eight 0.50-cal. machine guns, the fighter was not without its weaknesses. The most obvious was its sloth-like rate of climb – the slowest of any Allied fighter to 20,000ft. It would take a Thunderbolt nearly 12 minutes to reach 30,000ft, a full three minutes longer than the Spitfire IX and a minute behind the P-51B.
• As the Thunderbolt climbed, it got faster through the thinner air. However, once leveled off at altitude, the P-47 was able to out accelerate and maintain a higher top speed  than nearly all Allied and Axis fighters. Indeed, the XP-47B could maintain 412mph at 34,000ft, pulling 40 inches of manifold pressure at maximum throttle with the turbo on.
• In late 1942, the P-47C-1-RE was introduced, incorporating an eight-inch fuselage extension at the firewall so as to improve cockpit cooling. It also included provision for a belly-mounted external fuel tank to increase flight time and, therefore, range – a critical factor when escorting bombers over Western Europe.
• While poor rate of climb was a significant issue for the Thunderbolt, the fighter could out-dive anything in the sky once it arrived at altitude. Luftwaffe pilots learned very quickly not to try to dive away from an attacking Thunderbolt.
• Its unrivaled performance in a dive came in especially handy when P-47s at altitude would “bounce and zoom” enemy fighters. Pilots swooped down on their unsuspecting foes at high speed, firing quick bursts at carefully selected targets before using the momentum built up in the dive to zoom back up to altitude without losing much speed.
• The Thunderbolt’s diving capability was just as effective when undertaking attack runs on ground targets, pilots using the fighter’s speed and stability to present a minimal target to antiaircraft gunners and then zooming back up to altitude, and relative safety.
• While the P-47C did see combat in Europe, the majority were quickly withdrawn from frontline service with arrival of D-series aircraft from mid-1943. “Razorback” P-47Ds were the first to be adapted to the fighter-bomber role, and from the summer of 1944 they were supplanted by P-47D-25-RE “bubbletops.” The balance had quickly shifted in favor of the “bubbletop” throughout Ninth Air Force Thunderbolt groups by year-end.
• The P-47D Block 30 was the most produced, with 2,500 examples rolling off both the Evansville and Farmingdale production lines starting in the late fall of 1944.
• Since World War II, there has been some debate regarding the relative effectiveness of machine guns and cannon when used by fighter bombers in attacking ground targets. While each has its strengths and weaknesses, the Thunderbolt’s battery of eight Browning AN/M2 0.50-cal. machine guns may have been the best balance between the two types of guns.
• The cannon’s advantage lay in its explosive projectile, which also benefited from muzzle velocity and superior mass. However, a larger projectile and shell meant a reduction in ammunition capacity. The 0.50-cal. round was smaller and lacked the cannon shell’s explosive filler. However, where fighters like the British Hawker Typhoon carried four 20mm cannon, with 120 rounds per gun, the Thunderbolt carried twice as many 0.50-cal. machine guns and up to 3,400 rounds of ammunition.
• The AN/M2 fired 600-800 rounds per minute at a muzzle velocity of roughly 2,900ft per second. Ammunition belts were normally a mix of M2 ball, M8 armor-piercing incendiary and M10 tracer. While not truly an explosive cannon round, the M8 would ignite a small amount of flammable filling due to the impact of striking a target, which would detonate and ignite any adjacent flammable materials.
• The Thunderbolt was also able to carry a large AN/M65 1,000lb bomb under each wing as well, although the weapon was too big to be affixed to the centerline station. Proportionally, the M65 was similar in size to the M64, with slightly more than half of its weight consisting of explosives and the remainder bomb casing. It was ten inches longer than the 500lb bomb and, at 18in in diameter, it was four inches wider than the AN/M64. Both bombs also used the M103A1 nose fuse, although the M65 was also fitted with the longer M102A2 tail fuse.

Technical Specifications

AN/M2 0.50-cal. Machine Guns

The Thunderbolt was equipped with eight wing-mounted 0.50-cal. AN/M2 Browning machine guns that could achieve a rate of fire of up to 850 rounds per minute. A five-second burst from all eight guns would put 500 rounds of M2 ball, M8 armor-piercing incendiary and M10 tracer into a 3ft x 3ft target area 1,100ft in front of the aircraft. Spent cases and steel links were ejected from the bottom of the wing through square, staggered, apertures.

Artwork by Jim Laurier from P-47 Thunderbolt vs German Flak Defenses

• Machine of the Month