In January of 1941, the Army issued a requirement for a heavily-armed, high-performance interceptor fighter. The fighter was to be built around the 2300 hp Wright R-3350-17 "Duplex Cyclone" twin-row, eighteen-cylinder air cooled radial engine. This was the heaviest engine yet to be mounted in a fighter, and was the same engine that was to power the B-29 bomber, then under development. Built-in armament was to comprise no less than EIGHT 20-mm cannon or TWELVE 0.5-inch machine guns. Guaranteed maximum speed was to be 468 mph at 27,000 feet.
Curtiss's proposal was submitted to the Army on April 29, 1941. Their design was a cantilever low-wing monoplane with retractable main landing gear and tailwheel. The Wright R-3350 engine was to drive a pair of contrarotating three-bladed propellers. Since the aircraft was intended for high altitude operation, the engine was to be fitted with a turbosupercharger and the aircraft was to be equipped with a pressurized cabin. The pressurized cabin feature was a design first for a new single-seat fighter, the earlier Lockheed XP-38A being an adaptation of an existing design.
On June 27, 1941, the Army ordered two prototypes, one under the designation XP-62 and the other under the designation XP-62A. The XP-62 prototype was to be delivered within fifteen months, and the XP-62A was to be delivered fifteen months later.
On August 2, 1941, some changes in specifications were submitted for approval. The principal changes were a reduction in maximum speed to 448 mph and an increase of 1537 pounds in loaded weight. A mock-up inspection took place in December, and ninety changes were recommended. The status of the XP-62 project was reviewed on January 1, 1942, and it was recommended that the loaded weight be reduced from 15,568 pounds to 14,000 pounds by revising the structure, by removing four of the eight cannon, and by eliminating the propeller anti-icing equipment.
Proposals were submitted on January 13, 1942 for 100 production P-62 fighters, the first of which was to be delivered in May of 1943. A letter contract for 100 P-62s was approved on May 25, 1942. However, the contract was terminated by the Army on July 27, 1942 since it was feared that production of the new P-62 would have adversely affected deliveries of critically-needed Curtiss-built P-47G Thunderbolts.
Even though no production of the P-62 was envisaged, work on the XP-62 continued. The pressure cabin proved to be a problem, and delays in its delivery caused the first flight to the XP-62 to be pushed back. Eventually, it was decided that the first flight testing of the XP-62 should take place without the pressurized cabin being fitted. The first flight of the XP-62 (serial number 41-35873) took place on July 21, 1943. The portion of the contract covering the XP-62A was cancelled on September 21, 1943.
A limited amount of flight testing had been conducted with the XP-62 by February 1944 when it was decided to install the pressure cabin for general development work. However, by this time the XP-62 project had a very low priority and work proceeded very slowly. In the fall of 1944, the XP-62 was finally scrapped without any further flight testing.
Specification of Curtiss XP-62:
Powerplant: One 2300 hp Wright R-3350-17 "Duplex Cyclone" twin-row, eighteen-cylinder air cooled radial engine. Performance: The following performance figures are manufacturer's estimates, since only limited flight testing of the XP-62 took place. Maximum speed: 448 mph at 27,000 feet, 358 mph at 5000 feet. Normal range: 900 miles. Maximum range: 1500 miles. Climb to 15,000 feet in 6.9 minutes. Service ceiling: 35,700 feet. The weights of the XP-62 were 11,773 pounds empty, 14,660 pounds normal loaded, and 16,651 pounds maximum. Dimensions were wingspan 53 feet 7 3/4 inches, length 39 feet 6 inches, height 16 feet 3 inches, and wing area 420 square feet.