When, in 1936, the USAAC Materiel Division placed an order for the SEV-1XP as the P-35, it had stipulated that the 77th and last series aircraft be fitted with a more powerful supercharged engine. The chosen engine was the Pratt & Whitney R-1830-19 of 1,200hp, fitted with an integral medium-altitude two-stage mechanical supercharger.
A contractual modification enabled Seversky to complete the airframe to a standard similar to that of the private-venture AP-4. The AP-9 was, in fact, used for competitive evaluation at Dayton in lieu of the XP-41 until the latter became available. Power plant apart, the aircraft was in virtually all respects similar to the AP-4.
The XP-41 36-430 was delivered to Wright Field for USAAC evaluation in February 1939, but the Air Corps preferred the turbo-supercharged AP-4 and further development of the XP-41 was discontinued, although trials continued at Langley. This was the last of the Kartveli-designed fighters to bear the Seversky appellation, as the company thereafter became the Republic Aviation Corporation.
Engine: P&W R-1830, 1200hp
Wingspan: 10.97 m / 36 ft 0 in
Wing area: 20.44 sq.m / 220.01 sq ft
Length: 8.23 m / 27 ft 0 in
Height: 3.78 m / 12 ft 5 in
Max take-off weight: 3175 kg / 7000 lb
Empty weight: 2445 kg / 5390 lb
Useful load: 1210 lb
Max. speed: 520 km/h / 323 mph
Cruise speed: 290 mph
Ceiling: 7000 m / 22950 ft
Range: 789 km / 490 miles
Armament: 1 x 7.62mm + 1 x 12.7mm machine-guns
All Aero 