Only one fact was more remarkable than the lightning swiftness of the war: the utter lack of military preparations in the US. This meeting at Wright Field was being held to change that.
Among those present at the meeting were Lt. Col. Howard Z. Bogert and Maj. Franklin O. Carroll of the Air Materiel Division Experimental Engineering Section; Capt. Marshall “Mish” Roth, Project Officer; Julius Hulman of the Power Plant Laboratory; Paul B. Smith of the Technical Staff; and Maj. Lawrence “Bill” Craigie, Bogert’s assistant.
Defining SpecificationsKartveli, an immigrant from Russia, listened as the attendees began to describe the specifications that would be needed in fighter aircraft for the war that they tacitly agreed was coming. (Carl Spaatz and Ben Kelsey had already seen what the British thought was the minimum airplane necessary, and Bogert had properly been filled in.)
As the specification took shape, Kartveli may well have mentally torn up the vellums for his XP-44 fighter. He knew the airplane being described in this room was something entirely different.
Mish Roth later told of how Kartveli had sketched the outline of the fighter in a compartment on the train ride back to New York. Kartveli’s primary concern was wing loading, the single design point that seemed most critical to fighters. Based upon an estimated combat weight of 12,000 pounds, on the back of an envelope he drew a semi-elliptical wing with an area of 300 square feet. (Although neither Roth nor Kartveli knew it then, that’s the way the airplane would turn out.)
Although it took Republic only eight months from contract to prototype, the pieces that formed the Thunderbolt (Hart Miller gets credit for the name) were, in fact, beginning to fall into place decades earlier—and that’s the real story of the P-47.
Throughout the early 1900s, Moss and others who attempted to design a turbine engine encountered stubborn hurdles in metallurgy and in compressor efficiency. Like today’s fusion-power researchers, Moss was unable to design a compressor that would leave him with net power from the turbine to do some work—the “break-even” point could not be reached.
Thus, by the time Alexander Kartveli went shopping for a turbocharger for his AP-4/YP-43 fighter, Dr. Sanford Moss’s device was available, for sale, and listed in the General Electric catalog. A later NACA study estimated that the Pratt & Whitney R-2800 without a turbocharger was approximately twenty-eight percent efficient. With the turbocharger, the efficiency rose to thirty-three percent. The turbocharger remains one of the most significant contributions of American technology in that era.
Archrival Wright had cleaned out its sock drawer in 1932 to concentrate on the development of the Cyclone and the new R-2600 and -3350. Ailing engineering vice president George Mead of Pratt placed his faith in his manager. Luke Hobbs, a steady hand who had signed on at McCook after World War I before coming to Pratt & Whitney.
Hobbs, bewildered by this turn of events and determined to reverse it, set to work on a remarkable study which demonstrated conclusively that the supposed drag advantage of liquid-cooled engine installations was mythical once airplanes attained high enough airspeeds and the engines grew to sufficient horsepower. In fact, he drew a four-row radial with a spiraling cylinder arrangement that promised lower drag than the equivalent liquid-cooled engine (and, as it happened, he described perfectly the future four-row Wasp Major that powered the B-36).
That persuaded the Army to equip with the Wasp-powered Boeing, designed the P-12A, and, by 1930, the 1st Pursuit Squadron in 450-hp P-12As was flying combat formations at 30,000 feet. (See September ’79 issue cover painting by Keith Ferris and article on p. 120 by Jeff Ethell.) But in subsequent years, the Europeans at the Schneider Trophy Races had demonstrated that higher horsepower with then-current fuels seemed to drive engines toward liquid cooling, and the Allison gained its adherents in the US.
With Mead’s health failing, it was now up to Rentschler to return from & Whitney organization out of its crisis. He sized up the situation, immediately agreed with Hobbs’s assessment of the Army program, and he used his personal relationship with Hap Arnold to sit down with him and talk some turkey.
Arnold never hesitated. His only question to Rentschler was, “Why didn’t you tell me all this sooner?” Pratt & Whitney went on to deliver about half the horsepower used in World War II, and the R-2800 Double Wasp engine became a classic, eventually reaching 3,400 hp.
The AirframeIn 1915, one of the Czar’s naval aviators lost his right leg. The pilot, Alexander P. de Seversky, promptly replaced the lost leg with a wooden one and got back into airplanes again. Shortly after de Seversky was sent to the US as part of a Russian mission, he asked to remain in the US and was assigned as a test pilot and engineer for the government.
In 1931, he formed his own company and began to build an amphibian, the SEV-3, in Earl D. Osborne’s Edo Aircraft works at College Point on Long Island. It had a semielliptical wing. But anyone who could afford an amphibian was already buying Grover Loening’s giants. In 1934, fellow ex-Russian Kartveli arrived with credentials that included time with Bleriot and Fokker. De Seversky and Kartveli mapped out a “modular” design strategy of one airframe matched to a variety of wings and engines.
By 1938, de Seversky himself was in trouble with his financial backers due to colossal mismanagement and failures on the P-35 program. By 1939, he was gone for good, off to write the stirring book Victory Through Air Power. The Seversky Aircraft Corp. in October, with Kartveli staying on as vice president of engineering.
Kartveli’s first turbosupercharger, was installed in the Ap-4/YP-43, and he established its location—in the tailcone—as well as the extensive ductworks for exhaust gases and intake air then. The turbocharger and its ducts were laid out first, and the airplane designed around them. The turbocharger was the size of a small washing machine, and the ducts capacious enough for a man to crawl through them.
The R-2800 needed four propeller blades to absorb its horsepower, and, even then, Kartveli had to build the main gear with a “shrink” mechanism that would shorten it by nine inches at retraction to leave enough room for the outboard guns.
An epidemic of tail failures that arose in 1941 continued through the long, hot summer of 1942 at Langley before tests revealed that loads at high speeds could balloon the fabric coverings; all-metal tails resulted. Earlier compressibility studies after the XP-38 inflight disintegrations revealed the problem had resulted in an electric dive-recovery flap that was added to the P-47 as well. (Still, cadets were taught to be patient in their dive recoveries, to wait until reaching the dense air at lower altitudes.) Velocity-G-force recorders revealed how enormous were the aeroelastic problems at these speeds, and the wing was beefed up to compensate. And the NACA “paddle” propeller blades added 400 fpm to the climb—which it needed.
The Thunderbolt got pressed-paper wing tanks, a bubble canopy, rocket tubes, and bombs on the wings and belly, but, throughout the war, changes to it were minimal. It was produced in greater numbers than the P-51, which took over long-range bomber escort and converted the “Jug” into a low-level attack airplane whose rockets and Browning .50s busted tanks and railroads with ease. No other righter ever achieved its reputation for ruggedness.
“I was in the Ardennes a few days [after the battle turned]. We came to a thick woods where von Runstedt had hidden a munitions dump. He couldn’t have picked a better spot so far as air reconnaissance went. That had been a really heavy woods before we blew it all to hell.
“Even blown up, though, right through the center of that woods, you could see by the shattered trees and the torn branches where the P-47s had gone through. You’d have to see it to believe it. Those crazy kids flying the P-47s couldn’t see what was hidden from above. So they went right into the forest to find out. They cut a path right through the top of that woods. … one minute, you think of an airplane as a fragile thing, and then you see something like that.”
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