The F9F-4 Panther (and the F9F-5 that was developed in parallel with it) differed from the previous F9F-2/F9F-3 in having a 19.5-inch longer forward fuselage that made it possible to increase the internal fuel capacity from 923 to 1003 gallons. In addition, the height and area of the vertical tail surfaces were increased. The F9F-4 was powered by the uprated Allison J33-A-16, capable of delivering 6250 pounds of thrust dry and 6950 lb.s.t. with water injection.
The 99th and 101st production airframes (F9F-2s BuNos 123084 and 123086) were modified as the XF9F-4 prototype and the static test airframe. 123084 flew for the first time on July 5, 1950, powered by a 6250 lb.s.t. Allison J33-A-16 turbojet.
The F9F-4 was equipped with four external store pylons underneath each wing. The three outboard pylons were stressed to carry bombs of up to 500 pounds in weight, bringing maximum external load to 3465 pounds.
The J33-A-16 turbojet proved to be unreliable in service, and many F9F-4s were delivered to the Navy as J48-powered F9F-5s, and most of the others were re-engined with J48-P-6As once they entered service. They thus became indistinguishable from F9F-5s.
In early 1954, F9F-4 BuNo 125081 was modified as a test bed for a high-lift boundary layer control system.
123084 Grumman XF9F-4 Panther 123086 Grumman XF9F-4 Panther 125081 Grumman F9F-4 Panther 125156/125227 Grumman F9F-4 Panther 125913/125948 Grumman F9F-4 Panther
Engine: One Allison J33-A-16 turbojet, rated at 6250 lb.s.t dry and 6950 lb.s.t. with water injection. Performance: Maximum speed 593 mph at sea level, 547 mph at 35,00 feet. Stalling speed 131 mph. Cruising speed 495 mph. Initial climb rate 5140 feet per minute. Service ceiling 44,600 feet. Range 1175 miles. Dimensions: wingspan 38 feet 0 inches, length 38 feet 10 1/2 inches, height 12 feet 4 inches, wing area 250 square feet. Weights: 10,042 pounds empty, 15,264 pounds combat, 17,671 pounds gross, 21,250 pounds maximum takeoff. Internal fuel capacity 1003 US gallons Armament: Four 20-mm cannon. Offensive loads of up to 3465 pounds of bombs and rockets could be carried on eight underwing pylons.