Subject: Number Seventy-Two in the Series--Republic XP-72

From: [email-masked]
Date: 24 May 93 16:39:48 GMT

>From [email-masked]

The Republic XP-72 was Alexander Kartveli's proposal for a replacement 
for his fabulously successful P-47 Thunderbolt.  It was evolved in 
parallel with the XP-69 escort fighter project.  

The XP-69 was a completely new design, whereas the XP-72 was a 
more-or-less straightforward progressive development of the P-47 
Thunderbolt.  The XP-72 was the first fighter to be designed around 
the huge 28-cylinger Pratt & Whitney R-4360 Wasp Major, the most 
powerful piston engine produced during World War 2.  The wing and tail 
of the P-47D were retained, but the airframe was enlarged and 
strengthened.  The lower fuselage was modified to allow for a larger 
air intake for the turbosupercharger (still placed aft of the cockpt).  
The intake for the turbosupercharger was located under the wings 
rather than in the nose as in the P-47.  The Wasp Major engine was 
close-cowled and was fan-cooled.  The Wasp Major was to have driven a 
pair of three-bladed Aeroproducts contrarotating propellers.  The 
XP-72 was to have been fitted with a bubble-type canopy, similar to 
that used by the late production blocks of the P-47D.  Compressibility 
recovery flaps were fitted.  Armament was to consist of six 
wing-mounted 0.50-inch machine guns, and two 1000-pound bombs were to 
be carried on underwing shackles.  

The greater promise displayed by the XP-72 caused the USAAF to cancel 
the XP-69 project in favor of the XP-72.  Two XP-72 prototypes were 
ordered on June 18, 1943.  Serial numbers were 43-6598 and 43-6599.  

XP-72 Ser No 43-6598 flew for the first time on February 2, 1944.  
Power was provided by a 3450 hp Pratt & Whitney R-4360-13 Wasp Major 
air-cooled radial engine.  Since delivery of the planned Aeroproducts 
contrarotating six-bladed propeller had been delayed, the first XP-72 
was equipped with a single four-bladed propeller as a temporary 
stop-gap measure.  Nevertheless, the performance was excellent, a 
maximum speed of 490 mph being reached in flight tests.  The second 
XP-72 (43-6599) flew for the first time on June 26, 1944.  It was 
fitted with the Aeroproducts contrarotating propellers, which had 
finally been delivered.  Unfortunately, the second XP-72 was written 
off in a takeoff crash early in its test flight program.  

In spite of the loss of the second prototype, the USAAF was so 
impressed with the performance of the XP-72 that they ordered one 
hundred P-72 production variants.  These P-72s were to have the 
R-4360-19 engine and were to be provided with an optional choice of 
four 37-mm cannon as an alternative for the the six 0.50-in machine 
guns.  It was anticipated that speeds in excess of 500 mph would be 
attained.  

However, the changing character of the war created a greater need for 
long-range escort fighters than for high-speed interceptors, and the 
USAAF rapidly lost interest in the XP-72 project.  The order for the 
one hundred P-72s was cancelled.  The advent of jet-powered fighters 
which promised even more spectacular performance was undoubtedly also 
a factor.  

Specification of the XP-72: One 3450 hp Pratt & Whitney R-4360-13 Wasp 
Major air-cooled radial engine.  Maximum speed was 490 mph at 25,000 
feet.  Normal range was 1200 miles at 300 mph and maximum range was 
2520 miles at 315 mph with two 125 Imp.  gall.  drop tanks.  Initial 
climb rate was 5280 feet per minute, and climb rate at 25,000 feet was 
3550 feet per minute.  An altitude of 15,000 feet could be reached in 
3.5 minutes, 20,000 feet in 5 minutes.  Service ceiling was 42,000 
feet.  Weights were 11,476 pounds empty, 14,433 pounds normal loaded, 
17,490 pounds maximum.  Dimensions were wingspan 40 feet 11 inches, 
length 36 feet 7 inches, height 16 feet 0 inches, and wing area 300 
square feet.  

The surviving XP-72 (43-6598) is thought to have been scrapped at 
Wright Field at about the time of V-J Day.  

Sources: 

  Fighters of the United States Air Force, Robert F. Dorr and David 
  Donald, Temple Press Aerospace, 1980.  

  The American Fighter, Enzo Angelucci and Peter Bowers, Orion, 1987.  

  American Combat Planes, Third Enlarged Edition, Ray Wagner, Doubleday, 
  1982.  

  War Planes of the Second World War, Fighters, Volume 4, William Green, 
  Doubleday, 1964.  

Joe Baugher		AT&T Bell Laboratories   	
2000 North Naperville Road      Naperville, Illinois 60566-7033