What Happened to the P-38’s Successor?

A Promising Start

The Lockheed XP-49, an offshoot of the successful P-38 Lightning, was designed to be a twin-engine high-performance fighter. In March 1939, the U.S. Army Material Division issued a call for modified designs of existing aircraft to accommodate stronger engines. Lockheed and Grumman received contracts, with Grumman’s design as a backup.

Early Challenges

The XP-49’s development was slow. Initially designed with powerful engines capable of pushing speeds near 500 mph, the aircraft had to be reconfigured in 1940 to use less powerful Continental i430 engines (1,600 hp each) due to engine issues. This adjustment reduced the projected top speed to 458 mph.

Design and Development

The XP-49 shared 66% of its parts with the P-38 and was slightly larger, measuring 12.2 meters long with a wingspan of 15.86 meters. It had a gross weight of 18,750 lbs, about 1,000 lbs heavier than the P-38. Despite these upgrades, the XP-49 was plagued with issues, including frequent hydraulic system failures, which hindered testing for top speed, mock combat, and acrobatics.

Disappointing Performance

First flown in November 1942, the XP-49 underperformed. Its actual top speed was just 406 mph—slower than the P-38’s 414 mph. By 1943, the project was deemed unnecessary. The Continental engines failed to enter production, leaving the XP-49 without a viable powerplant. By 1946, the prototype was scrapped.

Conclusion

Although promising on paper, the XP-49 was ultimately unnecessary. The P-38 had already evolved into the high-performance fighter the XP-49 was meant to be, making the new design redundant. Its downfall was tied to its overpowered beginnings and subsequent inability to match expectations.