Was This The Fastest Piston Engine Fighter Ever?

While the P-47 Thunderbolt truly made its mark in the history of aviation, it’s not so well remembered as the XP-47J, which is known to be the fastest piston-engine fighter ever built.

Notable Difference

The most notable difference between the XP-47J and the standard aircraft was the alterations to the engine mount and nose. The engine was changed to a Pratt & Whitney R-2800 57c radial engine with a standard rated output of 2100 hp. In a war emergency setting, it can reach up to 2,800 hp.

The XP-47J also had a tight cowling fitted to enclose the engine and cooling was achieved by an intake fan and a new chin scoop. Inlets were also placed to give air to the turbosupercharger and the exhaust system was modified to be vented out of ventral poles that would give the plane an additional thrust.

Other modifications were also made to improve the performance: Armament was reduced to six machine guns and ammunition was cut down to 267 rounds per gun.

Also, to keep the airframe aerodynamically clean, it couldn’t hold external ordnance or drop tanks.

The Fastest Piston Engine Plane

The XP-47J first flew in November 1943, with the modifications achieving the basic intentions. It was later fitted with a new propeller and a General Electric CH5 turbocharger.

Reportedly, pilots would reach a top speed of 505 mph and climb rates that reached 30,000 ft. All of these factors would make the XP-47J the fastest piston-engine fighter of all time and justified its nickname as the Superbolt.

Issues And Cancellation

However, these results were never replicated and when the USAAF took possession of the aircraft and started their own test program, they only achieved a top speed of 484 mph. The engine also had to be switched out after only 10 hours of flight testing!

Ultimately, the second prototype never got built, limiting the XP-47J to just a single aircraft.

This is partially because Pratt & Whitney never sorted out the issues with their contrarotating propeller system that was intended to be fitted. It can also be attributed to the fact that the Republic itself lost interest in the idea of making XP-47Js.

Switching to the P-47J as a production standard would need a large amount of retooling just as a requirement for fighters was at its height. The P-47D was also found to be adequate for the job at hand.