I saw Widewing listed the P-47D-21 as an aircraft he thought should be added. What is the difference between the P-47D-21 and P-47D-23?
Here is the breakdown of P-47 development until the first bubbletop from the 368th fighter group web page~
Specifically between the D21 and D23/22 is a there was a slight increase in internal fuel, jettesonable canopy, bullet proof glass and the larger Hamilton or Curtis prop being factory installed. Earlier Ds were retrofitted stateside or in the field as Randy's document demonstrates. From the D-20 on they were able to generate 2300hp factory settings on WEP.
The P-47B was fitted with a Pratt & Whitney R-2800-21 engine rated at 2000 hp.
The engine drove a 12' 2"diameter Curtiss Electric C542S-A6 propeller.
The P-47B had an empty weight of 9,346lbs and a maximum loaded weight of 13,360 pounds.
The P-47B was essentially a test model and most were modified and quickly replaced by the P-47C model.
Only 171 P-47B models were built and very few were sent overseas.
Republic P-47C
The first Thunderbolt to be considered truly combat-ready was the P-47C-2-RE.
Perhaps the most important change introduced by this production block was the provision for shackles and
a release mechanism for a bomb or a fuel tank on the underside of the belly. When carrying a 200-gallon
belly tank the range was extended to 1250 miles at an altitude of 10,000 feet.
The P-47C-5-RE introduced revised radio, instruments, and antenna. Cockpit heating was also introduced.
The P-47C was the first Thunderbolts to see combat in Europe.
602 P-47Cs were delivered by February 1943, when the improved P-47D replaced it on the production line.
Republic P-47D
The Early P-47D differed very little from the P-47C-5-RE. The P-47D had changes in the turbo
supercharger exhaust system which incorporated an adjustable duct and redesigned vents for the engine
accessory section. Additional cowl flaps were fitted to improve engine cooling airflow.
More extensive armor protection was provided for the pilot.
Demand for the Thunderbolt was so great that Republic built a new factory at Evansville, Indiana to
augment production of the P-47D. 1050 P-47Ds were ordered from Evansville on January 31, 1942, and
the first Evansville-built P-47D (serial number 42-22250) rolled off the assembly line in September of 1942.
Evansville-built P-47Ds were distinguished by the use of the RA manufacturer letter code rather than RE.
Curtis built 354 P-47's designated P-47G, these were identical as the Republic versions, however most
Curtis built P-47's remained stateside and were used by training units.
All early Thunderbolts used the R-2800-21 engine. Water injection capability was added to this engine
beginning with the D-4-RA and D-5-RE production blocks. Provision was made for the mounting of
15-gallon tank carrying a water-alcohol mixture to the bulkhead just aft of the engine. A line from this tank
was plumbed directly into the fuel intake. When injected into the combustion chamber, the water checked a
dangerous rise in cylinder head temperature while manifold pressure was boosted. For brief instants, a
15-percent increase in engine power could be obtained, giving a maximum war emergency power of 2300
hp. In the D-5-RE, D-6-RE, and D-10-RE (D-4-RA, production bolcks, the pilot manually controlled the
water flow of the injector, but the injection procedure was automatically- controlled on the D-11-RE
(D-11-RA) and subsequent blocks. This happened when the throttle was pushed forward into its last
half-inch of travel.
Production batches from the D-20 onward were fitted with a "universal" wing which could carry a variety
of drop tanks or bombs. These batches also introduced the R-2800-59 engine with an improved ignition
system. The power was the same as that of the -63, with a war emergency power output of 2300 hp.
Production batches D-22-RE and D-23-RA, a 13' diameter paddle-bladed propeller (either a Hamilton
Standard Hydromatic 24E50-65 or a Curtiss Electric C542S) was fitted to make full use of the additional
power provided by water injection. Blocks D-22-RE and D-23-RA were also provided with a jettisonable
cockpit canopy which was activated by the pilot pulling a ring. A bullet-proof windshield was fitted, and
internal fuel capacity was increased.
