Originally posted by HoHun
Hi Widewing,
>I'm not suggesting anything, I'm telling you that the SoETP found the P-47 to be the superior fighter in a dive.
Widewing, you posted a list of dive speeds and right beneath it the statement:
"Recent testing by the Society of Experimental Test Pilots established that the military's ratings were accurate."
Simple question: Did the SETP establish that the dive speeds you posted are accurate or not?
>Also, I meant that the "eight-gun installation" on the P-47 was adequate for its mission, which was to destroy enemy fighters.
The Brownings might have been able to fulfill their mission, but the P-47 outfitted with Brownings is another thing.
You won't get any "lead on target" if you're low on fuel and returning home when the "targets" get at your bombers. Against the Schweinfurt raids, many Luftwaffe fighters could perform three interception sorties because the bomber flew over most of the Reich un-escorted. The width of the gap between fighter range and distance to target was directly responsible for the catastrophic losses the 8th Air Force took.
>Referred to as the Fighter Mafia
Was this term actually in used WW2? It's usually associated with the group around Boyd, who had great impact on fighter tactics and procurement in the 1960s and 1970s.
>Switching the P-47 to 20mm cannon would not have allowed for additional fuel with the existing wing design.
The earlier the Brownings were replaced, the better a constructive solution could have been found. A new engine mount like with the Fw 190 or a re-located cockpit like with the F4U might have provided the centre-of-gravity shift or the extra space needed to carry more fuel even in the fuselage.
The new engine mount for the Fw 190 was a minor engineering change, so I presume it would not have been a problem for republic either. The resulting forward move of the centre of gravity might have made an additional rear fuelage tank possible. (Wing tanks like the F4U-1's might not even have required an engine shift.)
Besides, a lighter aircraft has a longer range on the same amount of fuel as a heavier aircraft, so 20 mm cannon would have been beneficial even without any extra tanks on the P-47.
Regards,
Henning (HoHun)
I no longer have the SoETP book, some years ago I loaned it to a friend who misplaced it. However, I recall the general results of their testing and Francis Dean mentions the results in his book, America's Hundred Thousand. They found the P-47 to be the fastest accelerating and the most stable of the bunch in a dive. It out-distanced the others rapidly.
The numbers I provided are right out of the various pilot manuals for each type. Specific limits for the P-47 were 500 mph IAS below 25,000 feet and 400 mph IAS above 25,000 feet. For the Mustang, the limits were 505 mph IAS below 9,000 feet, 500 mph IAS above this, with a 300 mph IAS limit above 35,000 feet. Limits for the FG-1D were: 299 mph IAS at 30,000 feet, 368 mph IAS at 20,000 feet and 443 mph IAS at 10,000 feet. Typical of the Navy and Grumman, the F6F's limits were poorly defined. Largely to the severity of the airspeed indicator error. As it was, 370 knots (426 mph) IAS above 15,000 feet and 390 knots (449 mph) IAS below 15,000 feet. If you calculate 390 knots @ 15,000 feet, it equates to 566 mph TAS, or Mach .78, which is certainly well into compressibility.
As to adding 20mm cannon... The M2 cannon was nearly 40 inches longer than the BMG .50, which would have resulted in the guns protruding nearly four feet beyond the leading edge. Moving them rearward was not an option as the main spar was in the way. The difference in weight between 8 Brownings and 4 Hispanos amounts to just over 100 lbs. Normally, the P-47 carried 498 pounds of ammo (weight includes links). A typical weight of ammo for the M2 (as used on the P-38) was 92 pounds. Times 4, that equates to 368 pounds, or 130 lb less than the .50 cal load. Therefore, the total weight reduction is about 235 pounds. If every pound reduced was transformed into additional fuel, it would add 39 gallons. At 42" MAP, 2550 RPM, the P-47 burned 175 gallons/hour. So, this would add about 13 minutes of endurance, or less than 7 minutes to its combat radius. Now, the question begs, would the major level of modification required be worth the time, money and production delays associated with retooling? I think that the USAAF and War Production Board would say "hell no!" Moreover, a 1.4% reduction in loaded weight will not impact range in any measurable way.
Beginning with the P-47D-4, an 8 inch extention was added to the engine mount to allow for a QEC (Quick Engine Change) set-up, which greatly reduced the time required to change an engine. This pushed the P-47s MAC as far forward as Republic thought prudent.
To meet the need for additional range, the P-47D-25 introduced an enlarged internal aux tank, adding 65 gallons. With this, there was no more volume within the fuselage for additional fuel. Thus, Republic's extended, wet wing design that appeared on the P-47N.
My regards,
Widewing
