Special Aircraft Service

Please login or register.

Login with username, password and session length
Advanced search  
Pages: [1]   Go Down

Author Topic: Republic P-47 J31 & J35 "Turbobolt"  (Read 417 times)

0 Members and 1 Guest are viewing this topic.


  • Professional Amateur
  • member
  • Offline Offline
  • Posts: 100
  • I need bacon.
Republic P-47 J31 & J35 "Turbobolt"
« on: October 12, 2019, 02:51:20 PM »

Yeah, I'm going berserk with the "what-if" and 1946 ideas. I managed to dig up yet another wacky contraption that was considered in 1944 but never officially titled or constructed. In essence, this thing was an early brainstorm for what would become the F-84 Thunderjet.

Again, this fills that current void in the USAAF's jet-powered ground-attack capabilities and also gives the YP-80 another friend to fly with.

Thankfully, even though this was only a concept tossed around in the USAAF, I found a couple of good schematics. I think I'm finally getting the hang of this.

From militaryfactory:
By the end of 1944, the Germans had pushed the Messerschmitt Me 262 "Schwalbe" into operational service, giving German pilots a decided edge in the skies over Europe. This prompted American authorities to expedite work on their own jet-powered types. However, traditional long-term development was not favored so the route of converting an existing airframe was entertained in an effort to bring the jet fighter into service as quickly as possible. One endeavor emerged from Republic whose P-47 "Thunderbolt" had already entrenched its legacy in the years-long war.

The P-47 seemed a natural choice because of its oversized fuselage housing the massive and powerful Pratt & Whitney R-2800 "Double Wasp" series radial piston engine. The Republic product itself was a workhorse and excellent gunnery platform while also being used in the attack role by way of dropping bombs and launching rockets. The "tear-drop" style canopy gave its sole pilot excellent vision for a combat fighter and the inherent performance of the aircraft as a whole was equally excellent - capable of going toe-to-toe with the latest Messerschmitt Bf 109 and Focke-Wulf Fw 190 prop-driven designs coming out of German factories.

Initially, engineers were called to fit the General Electric J31 centrifugal compressor turbojet engine into the aircraft in place of the R-2800. This jet engine was the same as used in the upcoming Bell P-59 "Airacomet" fighter as well as the Ryan FR "Fireball" mixed-power fighter and could generate up to 1,650 lb of thrust. In theory the mating seemed viable but it was soon found that, despite the large diameter of the P-47's existing fuselage, it was still not large enough to accommodate the J31 engine without much modification to the structure - thus delaying testing and service entry. From there came the decision to replace the J31 with the Allison J35 (about 4,000lb of thrust), this engine originally developed by General Electric as well. This engine would also soon power the classic Republic F-84 "Thunderjet" and Northrop F-89 "Scorpion" lines of the Cold War years (1947-1991) and its size was better suited to the P-47's airframe so work began to redraw the lines of the aircraft.

Because the R-2800 and its propeller were situated at the nose, their removal cleared the section for a nose-mounted intake and armament. The intake aspirated the J35 unit through a curved duct assembly running under the cockpit floor. The J35 would be buried under the pilot's position, promoting a deeper fuselage than even the original P-47 had. Exhausting of the turbojet was through a simple port found under the tail fin. The 8 x 0.50 caliber Browning heavy machine guns originally mounted to the wings (four per wing) were now relocated to the nose for better concentrated firepower. The elliptical wings of the P-47 were retained as were the rounded tailplanes featuring a single vertical fin. It is assumed that the original tail-dragger undercarriage would have been retained as well.

Nevertheless, this proposed turbojet-powered P-47 (no formal name or model designator was ever assigned to the "paper" project) never made it beyond some concept drawings commissioned by Republic. In the end, the mating of the J31 with the P-47 airframe was not meant to be for it was becoming an impractical exercise best left to the imagination. There were also ongoing concerns about the imbalance that the engine would have caused on an aircraft originally intended to feature its mass at the front. Engineers also realized that the P-47 airframe, as it was, stood to gain very little in terms of performance for it was already nearing its maximum specs even with its R-2800 in place.

As such, the P-47 offshoot never emerged into a realistic prospect leaving the USAAF to pursue the traditional design and development route for its first jet - which became the mildly successful P-59 from Bell.

Performance and structural dimensions reported on this page are estimates on the part of the author.

Specs (J35):

Crew: 1
Length: 36.09 ft (11 m)
Width: 40.85 ft (12.45 m)
Height: 14.76 ft (4.5 m)
Weight (Empty): 10,031 lb (4,550 kg)
Weight (MTOW): 18,078 lb (8,200 kg)

Power: 1 x Allison J35 axial flow turbojet engine developing about 3,800lb to 4,000lb of thrust*

Speed: 450 mph (725 kph; 391 kts)
Ceiling: 37,730 feet (11,500 m; 7.15 miles)
Range: 621 miles (1,000 km; 540 nm)
Rate-of-Climb: 1,200 ft/min (366 m/min)

*With the General Electric J31 producing only 1,650lbs of thrust, variants equipped with this engine would have greatly reduced flight characteristics; easily less than half of what the J35 provided. However, it's still a jet engine with significant speed boosts. In fact, with the Allison J35 having such an incredible amount of power (and being the main engine of the later F-84 Thunderjet), the P-47's airframe seems inadequate to take full advantage of it.


P-47 J31 A (1944) - "Solution 1" from schematics above using the General Electric J31 engine, equipped with the standard eight 50-cals in the wings.
P-47 J31 C (1944) - "Solution 3" from schematics above using the General Electric J31 engine, equipped with the standard eight 50-cals in the wings.
P-47 J35 (1946) - Allison J35 engine variant from depiction above with eight 50-cal MGs in the nose.

And voila! Although it might be sluggish as a jet fighter, its ground attack capabilities and armor are what would make this shine as an excellent battle companion for the YP-80. With the alternative history that a 1946-scenario provides, it's not too far-fetched to have the USAAF go ahead with the jet P-47 conversions since the planes are already built and ready for modification. The J35 modification was passed up in obvious favor of the specially-designed F-84 Thunderjet, but again, alternate history and extended warfare leads to some interesting possibilities.
Pages: [1]   Go Up

Page created in 0.014 seconds with 26 queries.