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The Northrop P-61C was the final production version of the Black Widow night-fighter, and differed from earlier aircraft in having more powerful turbo-supercharged engines. The first few production aircraft entered service just before the end of the Second World War, but the end of the war also saw the end of the contract, and none were used in their intended role.
The P-61C was developed because the USAAF felt that the standard P-61A/ P-61B lacked speed and didn’t have a high enough service ceiling. Both of these faults could be traced back to the decision not to use a turbo-supercharged engine in the P-61, and at the end of 1943 the Army asked Northrop to develop a more powerful version of the P-61, using turbo-supercharged Pratt & Whitney R-2800-77 engines.
Northrop didn't have the spare development capacity to work on this project, and so Goodyear was given the job. The new engines caused most of the problems with the project. The -77 engines weren't available, and so Goodyear had to use Naval -14W engines instead. These were then replaced by -57 engines, and the two prototypes were redesignated as XP-61Ds. Finally the -77 engines arrived, and the prototypes were tested with their intended engines.
As expected the XP-61D was significantly faster than the P-61A/B, with a top speed of 430mph and a service ceiling of 41,000 feet, improvements of 60mph and 8,000ft respectively. The new aircraft also had a tighter turning circle, thanks to the use of 'fighter brakes' – air brakes fitted to the wings. The army placed a contract for 207 P-61Cs, and the first production aircraft was completed in July 1945.
The end of the war meant that this contract was cancelled after only 54 aircraft had been constructed, thirteen of which were immediately scrapped. The remaining aircraft were used for a variety of purposes, with the largest number going to Project THUNDERSTORM, which saw aircraft deliberately fly into thunderstorms to record the conditions within the clouds. Despite their impressive performance, all 41 surviving P-61Cs had been stricken from the Air Force inventory by April 1949.