Republic P-47D Thunderboilt

P-47D/G Thunderbolt

By Joe Baugher

In 1934, text text.

    The P-47D was the first version of the Thunderbolt to undergo really large-scale production. The first USAAF contract came on Oct 14, 1941, when 850 examples were ordered, to be followed by many more.

    In its initial form, the P-47D differed very little from its predecessor P-47C. It had some changes in the turbo-supercharger exhaust system that incorporated an adjustable duct and redesigned vents for the engine accessory section, additional cowl flaps for better engine cooling airflow, more extensive armor protection for the pilot. However, early P-47Ds can be distinguished from Cs only by serial numbers.

    Demand for them was such that Republic built a new factory at Evansville IN to augment production. 1,050 Evansville P-47Ds were ordered on Jan 31, 1942, and the first one rolled off the assembly line in Sep 1942 [42-2225]. They were distinguished from Farmingdale-built P-47Ds by their s/ns and an -RA manufacturer code replacing Republic's -RE.

    Following cancellation of an Army contract for the P-60A in Jan 1942, Curtiss-Wright was given a contract to build P-47Ds under license at its Buffalo plant—designated P-47G and with -CU as a manufacturer code. In Dec 1942, their first 20 P-47G-CUs were similar to the P-47C, but the remainder, P-47G-1-CU through P-47G-15-CU, were identical to Republic's P-47Ds, again distinguishable only by their s/ns. Since Curtiss P-47Gs tended to lag behind Republic models in the latest refinements, most were relegated to training roles and very few went overseas. Curtiss production of 354 planes ended in March 1944.

All early Thunderbolts used the P&W R-2800-21, with water injection added (R-2800-63) beginning with the D-4-RA and -RE production blocks. Provision was made for mounting a 15-gallon water-alcohol tank to the bulkhead just aft of the engine, a line from which was plumbed directly into the fuel intake. When injected into the combustion chamber, the water checked a dangerous rise in cylinder-head temperature, while boosting manifold pressure. For brief instants, a 15% increase in engine power could be obtained a maximum war-emergency 2300hp. In the D-5-RE, D-6-RE, and D-10-RE, the pilot manually controlled the water flow of the injector, but the procedure was automated on the D-11-RE and subsequent blocks. This happened when the throttle was pushed forward, past a detent, into its last half-inch of travel.

    Factory-installed R-2800-63s began to appear on the Farmingdale and Evansville production lines with blocks D-10-RE and -RA, while retrofitting kits were made available for earlier P-47Cs and Ds. Since they were already built to accommodate water-injection, the D-4, -5, and -6 bunch could be quickly modified, but D-1, -2, -3, and the earlier C-2 and -5 ships required about 200 hours of work each for addition of the capability.

Shackles for a belly drop-tank or a 500# bomb were added to P-47D-5-RE and D-11-RA and later production blocks; underwing pylons were introduced on the D-15-RE and D-15-RA blocks. Fuel-line changes had to be made to incorporate plumbing for underwing drop-tanks. Stores increased to two 1000# or three 500# bombs for maximum bomb load. A 108-gal drop tank carried under each wing added 150 miles to the P-47's range. Earlier P-47C and D models could be modified in the field to accommodate underwing racks, but the amount of work required many man-hours. Underwing pylons had a detrimental affect on performance—their air resistance cut 45 mph off the maximum speed—but a redesigned, more streamlined pylon cut the loss to about 15 mph.

    Two Curtiss P-47Gs were converted as tandem, two-seat trainers in which one of the fuselage fuel tanks was removed and a second cockpit fitted in its place. Redesignated TP-47G, they retained the eight-gun armament.

Toward the end of 1943, 8th Air Force Thunderbolts began returning from escort missions over Europe "on the deck," searching out ground targets of opportunity for their unused ammunition. It was found that they were well suited for this new role and it led to perhaps the most successful adaptation of the P-47—as a fighter-bomber.

    P-47D-6-RE to -11-RE and P-47G-10-CU to -15-CU production blocks had only ventral shackles, stressed to accommodate one 500# bomb, but subsequent production blocks were fitted with wing pylons and stronger wings which permitted two 1000# bombs, three 500# bombs, or a combination of bombs and drop-tanks. Either six or eight machine guns could be carried, and maximum ammo capacity was 425 rpg; however, with a full ordinance load, that was reduced to 267 rpg.

    Suddenly a number of Thunderbolts suffered mysterious engine failures during missions that could not be ascribed to enemy action. It was soon discovered that the addition of bombs and drop-tanks added so much weight to the aircraft that it built up excessive dive speeds in bombing attacks. During recovery from those dives, G-forces got so high that a surge, or vapor lock, was produced in the fuel lines that the fuel pump was unable to overcome.

    Production batches from P-47D-20-RE on were fitted with a "universal" wing that could carry a variety of drop-tanks or bombs. Those batches also introduced the R-2800-59 engine with an improved ignition system. The length of the tail wheel leg was increased.

Beginning with production blocks D-22-RE and -23-RA, a 13' paddle-blade propeller. either Hamilton Standard Hydromatic 24E50-65 or Curtiss Electric C542S, was used to make full use of the additional power provided by water injection. It added 400 fpm to the climb rate, but there was a scant six inches of clearance between blade tips and the ground during take-offs and landings, which must have been hair-raising!

    The same blocks added a jettisonable cockpit canopy. The pilot pulled a ring, the hood would then be pushed backward, and the slipstream would then finish the job of pulling the canopy free of the aircraft. A bullet-proof windshield was also fitted and internal fuel capacity increased.

    The 3,962 P-47D-1-RE to -22-RE, the 1,461 P-47D-2-RA to -23-RA , and all 354 P-47G-1-CU through -15-CU Thunderbolts had the original framed sliding canopy first used on the P-47B. However, combat experience indicated that the the aft decking on them featured a serious blind spot, a real hindrance in aerial combat. In an attempt to improve rearward visibility, a few P-47Ds were field-modified with a Malcolm hood, the Spitfire's bubble canopy that was also appled to both RAF and AAF P-51B and C Mustangs. Yet P-47Ds fitted with Malcolm hoods were quite rare. In search of a more lasting solution, the AAF modified a stock P-47D fuselage [42-8702] with a bubble canopy from an RAF Hawker Typhoon and redesignated XP-47K. Tested in July 1943, the mod was proven feasible and was promptly introduced on Farmingdale and Evansville production lines.

Ordinarily the AAF would have given such a radical modification as that which produced the bubble-canopy Thunderbolt a completely new variant letter, or perhaps even a new type number. However, they chose instead to simply give it a new production block number in the D-series. Consequently, the first batches to feature this new bubble canopy were Farmingdale's P-47D-25-RE and Evansville's P-47D-26-RA. Those batches also had the R-2800-59 or -63 engines, the paddle-bladed propeller, and the "universal" wing. Stronger belly shackles capable of carrying a 110-gal drop tank were fitted which, together with the 305-gal main fuselage tank, an 100-gal auxiliary fuel tank and two 150-gal underwing tanks, made possible a maximum range of 1,800 miles at 195 mph at 10,000'.

    Early "bubble-canopy" Thunderbolts suffered from some directional instability as a result of the loss of aft keel area. From the P-47D-27-RE production lots onward a dorsal fin was fitted just ahead of the rudder to restore stability. P-47D [42-76614] was taken off the production line and modified as XP-47L with a bubble canopy. like XP-47K, and with larger fuel tanks which raised internal fuel capacity from 305 to 370 gallons. Both changes were incorporated in the P-47D-25-RE production batch. Underwing zero-length launching stubs for ten 5" HVAR rockets were added to production blocks from P-47D-30-RA on.

    High dive speeds of which the Thunderbolt was capable pushed the aircraft to the edge of compressibility, so new blunt-nosed ailerons were fitted to improve controllability at those speeds. To assist in dive recovery, an electrically-operated dive-recovery flap was fitted on the undersurfaces of each wing.

Farmingdale produced a total of 2,547 bubble-canopy P-47Ds and Evansville built 4,632. In post-war years numerous surplus ex-AAF Thunderbolts went to foreign air forces—Bolivia, Brazil, Chile, China, Colombia, Dominica, Ecuador, Honduras, Iran, Nicaragua, Peru, Turkey, Venezuela, and Yugoslavia. Some of those flew until the late '60s, when they were replaced by jet aircraft.

    Farmingdale POP: 114 P-47D-1-RA [42-22250/22363]; 200 P-47D-2-RA [42-22364/22563]; 100 P-47D-3-RA [42-22564/22663]; 200 P-47D-4-RA [42-22664/22863]; 250 P-47D-11-RA [42-22864/23113]; 29 P-47D-16-RA [42-23114/23142]; 157 P-47D-15-RA [42-23143/23299]; 800 P-47D-23-RA [42-27389/28188]; 250 P-47D-26-RA [42-28189/28438]; 1,028 P-47D-28-RA [42-28439/29466]; 187 P-47D-20-RA [43-25254/25440]; 224 P-47D-21-RA [43-25441/25664]; 89 P-47D-23-RA [43-25665/25753]; 1,800 P-47D-30-RA [44-32668/33867, 89684/90283]; 665 P-47D-40-RA [44-90284/90483, 45-49090/49554].
    Republic POP: 105 P-47D-1-RE [42-7853/7957]; 445 P-47D-2-RE [42-7958/8402]; 300 P-47D-5-RE [42-8403/8702]; 350 P-47D-6-RE [42-74615/74964]; 250 P-47D-10-RE [42-74965/75214]; 400 P-47D-11-RE [42-75215/75614]; 445 P-47D-15-RE [42-75615/75814, 76119/76364]; 254 P-47D-16-RE [42-75865/76118]; 300 P-47D-20-RE [42-25274/25322, 76365/76614]; 216 P-47D-21-RE [42-25323/25538]; 850 P-47D-22-RE [42-25539/26388]; 385 P-47D-25-RE [42-26389/26773]; 615 P-47D-27-RE [42-26774/27388]; 750 P-47D-28-RE [44-19558/20307]; 800 P-47D-30-RE [44-20308/21107].
    Curtiss POP: 20 P-47G-CU [42-24920/24939]; 40 P-47G-1-CU [42-24940/24979]; 60 P-47G-5-CU [42-24980/25039]; 80 P-47G-10-CU[42-25040/25119]; 154 P-47G-15-CU [42-25120/25273].

Finish up with P-47M/N, plus the Odds & Mods.

SOURCES as previous