P-47N Thunderbolt vs. F4U-4 Corsair - Which was superior?

[DAVIDICUS]

RG_Lunatic:

My understanding was that the M2 was the standard gun used on U.S. aircraft throughout the war. (There certainly was no need to engineer and introduce a fifty with a higher rate of fire. Six fifties were considered more than adequate against other fighters [especially Japanese fighters] and most of the "N" models had eight! Also, as the cyclic rate increases, so do the jams.)

I'd like to read anything you know of that states differently. I have heard that the rate of fire of the M2 would increase as the belt got used up as the gun would be dragging a lighter ammunition belt although, frankly, I'm not sure about that claim.

As to the dive claim, please name some of these "number of planes" that could exceed the speed of a P-47 in a dive. I have never read or heard of these planes and everything I have read and heard indicates that the P-47 was faster in a dive than the F4-U, probably due to drag from the different wing loadings. The F4-U's wing loading made is better able to haul heavy loads and require less airstrip to get airborn. Perhaps you've heard of the joke about P-47's - Q: How mush airstrip does a P-47 need to take off? A: All of it!

Perhaps you have some date you can share concerning various "critical mach levels" of different aircraft.

One more unrelated question if you would be so kind as to indulge me. How exactly are the "confirmed kills" and "unconfirmed kills" calculated when you post?

Thanks.

Originally Posted by DAVIDICUS

RG_Lunatic:

My understanding was that the M2 was the standard gun used on U.S. aircraft throughout the war. (There certainly was no need to engineer and introduce a fifty with a higher rate of fire. Six fifties were considered more than adequate against other fighters [especially Japanese fighters] and most of the "N" models had eight! Also, as the cyclic rate increases, so do the jams.)

The M2 was the standard gun. The M3 was introduced very late in WWII. Apparently it was only used for the top front turret on a few B-29's and the P-47N. Years ago I tracked the shipments of the approximately 18,000 M3's deployed during WWII to 3 bases, one of which was Iwo Shima, which only fielded P-47N's in any significance. The P-47N was ideal for the M3 because of its huge ammo supply of 500 rpg, and I believe it had a power assist belt feed. I believe the F-86 also sported the M3 in Korea, but aside from that it has only been used on helicopters. The jam rate probably did increase, but given that the M2 had a Jam rate of only about 1/3rd the rate of the Hispano or MG151/20, how is this relevant? Also, steralite lined barrels and other improvements to the M3 design would mitigate the increase in jam rate. And evidence from the use of the "nickle trick" is that it did not significantly increase jam rates, but that it did tend to wreck guns by cracking the reciever after a dozen or so sorties - but usually these guns were still working when the cracks were found by the armorers!

Originally Posted by DAVIDICUS

I'd like to read anything you know of that states differently. I have heard that the rate of fire of the M2 would increase as the belt got used up as the gun would be dragging a lighter ammunition belt although, frankly, I'm not sure about that claim.

I'll have to search for the info. It's been 4 or 5 years, two moves, three machine and two or three OS updates since I dug out the records. It's in some military accounting records somewhere (the tracking of the M3's) which should be easy to find if the urls are still good, but which will be hard if I have to locate them in old offline content under an old OS installation (which sucks because there is no way to view it short of firing up the old installation).

BTW: another thing that effects RoF is gun age. Older guns tend to fire faster as the springs become worn.

Originally Posted by DAVIDICUS

As to the dive claim, please name some of these "number of planes" that could exceed the speed of a P-47 in a dive. I have never read or heard of these planes and everything I have read and heard indicates that the P-47 was faster in a dive than the F4-U, probably due to drag from the different wing loadings. The F4-U's wing loading made is better able to haul heavy loads and require less airstrip to get airborn. Perhaps you've heard of the joke about P-47's - Q: How mush airstrip does a P-47 need to take off? A: All of it!

Perhaps you have some date you can share concerning various "critical mach levels" of different aircraft.

Sure. Spitfire XIV = 0.89, Tempest = 0.83, P-51B = 0.84, P-38 = 0.65, P-47C = 0.69

Note: "limiting mach" is usually figured at about 0.02 below crtical mach, which is where the really bad behavior hits hard.

Of course, the P-47N would have had a better critical mach figure than the C model. The experimental J model had a critical mach of 0.83.

I have not been able to find anything more on the F4U critical mach figure than that it was "comparable to the P-51", other than that the prototype in 1941 got a figure of 0.73 in the wind tunnel - which probably would translate to about 0.78 true.

Originally Posted by DAVIDICUS

One more unrelated question if you would be so kind as to indulge me. How exactly are the "confirmed kills" and "unconfirmed kills" calculated when you post?

Thanks.

LOL - I have no idea. You will have to ask a board Admin.

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Lunatic

[cheddar cheese]

I dont know how theyre calculated, its kinda random As a general rule, the more you put in a post, the more you get.

(The reason mine are so low is cos im on here so much and it limits you to certain amounts a day)

[DAVIDICUS]

RG_Lunatic:

Are you saying that the Spitfire XIV, Tempest, P-51B, and P-38 could exceed the P-47 in dive speed? I don't think so but at present can offer nothing more in support than what appears below.

Chuck Hawks wrote an article "The Best Fighter Planes of World War II." In it, he favored the P-51. He received a letter from Lt. Rip Collins who piloted both P-51's and P-47's in the 35th Fighter Group in the Pacific. Lt. Collins took him to task citing several reasons why the P-47 was a better fighter than the P-51. See number 4 below. If the Corsair's dive speed was "comparable to the P-51" as you mentioned, then Lt. Collins claim would indicate that the P-47 was superior to the Corsair in a dive.


1. The Republic Thunderbolt had a radial engine that could take hits and keep on running. I know of an actual case where a Jug brought a pilot back from Borneo after 8 hours in the air. The pilot landed with the master cylinder and three other cylinders blown out of commission. But the Jug kept chugging along, running well enough to bring its pilot back safely to his base at Morotai. I was there.

2. The Jug's radial engine was air cooled, instead of liquid cooled with a radiator system, like the Mustang's V-12. This is significant because one small caliber hit on an aluminum cooling line in a Mustang would let the coolant leak out, and when the coolant was gone, the engine seized, and the show was over. I took a small caliber hit in a coolant tube over Formosa (Taiwan). When I landed back at base, my crew chief said, "Lieutenant, did you know you got hit?" I replied, "No." He continued, "You took a small caliber shell in the coolant tube on the right side of the engine. I'd give you between 10 and 15 minutes flying time remaining." I had just flown from Formosa, over nothing but the Pacific Ocean, to our fighter strip on Okinawa.

3. The P-47 could fly higher than the P-51. With its huge turbocharger, it could climb to over 40,000 feet. You could just look down at your enemy in a stall and smile.

4. The Jug could out dive the Mustang. As a matter of fact, it could out dive any enemy fighter, and at 7.5 tons loaded, it dove fast! I have personally been in a dive at what we called the "state of compressibility," at nearly 700 mph indicated air speed. I was scared to death, but with a tiny bit of throttle, I pulled it out at about 2,000-foot altitude, literally screaming through the sky.

5. The Thunderbolt had eight .50's. The Mustang had six. That's 33 1/3% more firepower. This made a major difference.

6. The later model Thunderbolt's could carry and deliver 2,500 pounds of bombs. (One 1,000-lb. bomb on each wing, and one 500 lb. bomb under the belly.) This was a maximum load and you had to use water injection to get airborne. But it would do this with sufficient runway. I have done this myself.

In addition to being a first class fighter, it was also a superb fighter-bomber and ground level strafer. Jugs practically wiped out the German and Italian railroads. I have strafed Japanese trains, troops, ships, gunboats, warships, airfields, ammo dumps, hangers, antiaircraft installations, you name it. I felt secure in my P-47.

7. The P-47 was larger and much stronger, in case of a crash landing. The Jug was built like a machined tool. Mustangs had a lot of sheet metal stamped out parts, and were more lightweight in construction. One example was the throttle arm. You can see the difference. What does all this mean? The safety of the fighter pilot.

8. The Thunderbolt had no "scoop" under the bottom. You can imagine what happens during a crash landing if your wheels would not come down (due to damage or mechanical trouble). On landing, it could make the P-51 nose over in the dirt as the scoop drags into the earth. In water (and I flew over the Pacific Ocean most of my 92 combat missions), it could cause trouble in a crash landing because the air scoop would be the first part of the aircraft to hit the water. Instead of a smooth belly landing, anything might happen.

9. The Thunderbolt had a much larger, roomier cockpit. You were comfortable in the big Jug cockpit. In my Mustang, my shoulders almost scraped the sides on the right and left. I was cramped in with all my "gear." I could not move around like I could in the P-47. I found the ability to move a little bit very desirable, especially on seven and eight hour missions.

10. The Mustang went from 1,150-horse power Allison engines to the Packard built Rolls-Royce Merlin engine that had 1,590 hp. The Thunderbolt started out with a 2,000 hp Pratt & Whitney engine, and ended up with 2,800 war emergency hp with water injection. That's close to twice the power.

11. The Jug had a very wide landing gear. This made it easy to land just about anywhere, with no tendency to ground loop. Many times we had to land on rice paddies and irregular ground. When you set the Thunderbolt down, it was down. In the Far East, England, Africa, and Italy, this helped you get down and walk away from it. To me, that was very important for the safety of the pilot.

12. The Jug's record against all opposing aircraft is remarkable. The ratio of kills to losses was unmistakably a winner. Thunderbolt pilots destroyed a total of 11,874 enemy aircraft, over 9,000 trains, and 160,000 vehicles.

[cheddar cheese]

The Jug certainly was tough, someone posted on here a while back that they had read of a P-47 literally flying through trees (on purpose!) and surviving

Originally Posted by DAVIDICUS

RG_Lunatic:

Are you saying that the Spitfire XIV, Tempest, P-51B, and P-38 could exceed the P-47 in dive speed? I don't think so but at present can offer nothing more in support than what appears below.

The P-38 critical mach number was lower than that of the P-47, to it's max dive speed would be even lower.

It is important to understand that initial dive acceleration is a huge part of the "dive" performance. This is where the P-47 (and almost all US planes by virtue of their weight) excelled. At the start of the dive a P-47 could quickly pull thousands of feet away of a pursuer. After that, planes with higher critical mach figures would start to slowly catch up.

Also, critical mach figures usually indicate where the plane stops being responsive to controls, and often reflect wing and tail surface mach levels. At this point portions of the airflow over the plane such as the cowl and canopy might already be exceeding mach airflow, causing undesirable flying characteristics. The pursued plane would be less concerned with this than the pursuer, as he does not need to shoot.

Another important issue is terminal dive speed. Both the P-38 and the P-47 (and espeically the Me262) had serious terminal dive speed issues (where a dive could not be recovered and meant an inevitable crash), which were eventually "solved" through the use of dive recovery flaps. Dive recovery flaps had to be deployed at the beginning of a dive, once high speed was attained the hydrolics could not deploy them. These flaps had to reduce the critical mach figure for the planes and also acted as air brakes slowing dive acceleration.

Anyway, both the P-47 and the F4U were large planes with about the same relative power, so both would have had similar initial dive acceleration. The P-47N had a psuedo-laminar flow wing, so perhaps it's critical mach was equal to or higher than that of the F4U-4. Also, the F4U-4 had to be very careful above about 535 mph IAS or the fabric on the wings could be ripped off.

Attached is an interesting document concerning the behaivor of the Spitfire IX at high fractions of mach.

The 700 mph figure quoted is rubbish. Down low the air is just too thick for such speeds from a P-47 (and have the pilot survive), up high that exceeds mach 1. I suspect either the pilot was exagerating or the airspeed indicator was inaccurate at such high speeds (very likely). The maxium reading on the air speed indicator of the P-47 is 700 mph. Any dive steep enough to exceed much over 550 mph in a P-47 was probably terminal. A P-47 at 250 mph at 25,000 feet could not execute a normal power split-S without eating dirt!

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Lunatic

Originally Posted by cheddar cheese

The Jug certainly was tough, someone posted on here a while back that they had read of a P-47 literally flying through trees (on purpose!) and surviving

The USAAF and USN conducted post war tests and determined the F4U was the tougher plane. Its wing spar is much stronger (to support carrier operations) and the P-47's turbo-supercharger and fuel tank layout made it more vulnerable to enemy fire.

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Lunatic

[the lancaster kicks ass]

altough that's not to say that the P-47 couldn't take damage...........

an CC can you find this post as there were several mentions of P-47's flying through the trees as in below tree top level but no single engined plane could literally fly into a tree and survive.......

[cheddar cheese]

No I cant find it...it was months ago and ive no idea where I read it...

[the lancaster kicks ass]

well like i said if i'm thinking of the same one as you they were flying below tree top height, think about it, not even the P-47 or corsair could survive a crash with a tree............

[cheddar cheese]

You do know I mean just the foliage, not the trunk...

Originally Posted by the lancaster kicks ass

altough that's not to say that the P-47 couldn't take damage...........

an CC can you find this post as there were several mentions of P-47's flying through the trees as in below tree top level but no single engined plane could literally fly into a tree and survive.......

There were many cases of P-47's flying into ground objects and surviving. The most famous is one that flew into a radio tower, tore of several feet of one wing, and still made it home.

Also there are many accounts of P-47's, and espeically Corsairs which clipped the tops of trees with their props and survived.

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Lunatic

[DAVIDICUS]

RG_Lunatic:

You still haven't convinced me that, as you stated, "The Corsair was able to dive at speeds up to 550 mph IAS, which is faster than the max IAS of the P-47."

You now state, "The P-47N had a psuedo-laminar flow wing, so perhaps it's critical mach was equal to or higher than that of the F4U-4. Also, the F4U-4 had to be very careful above about 535 mph IAS or the fabric on the wings could be ripped off."

So it sounds like the P-47 would have an initial dive acceleration advantage due to weight and a likely terminal advantage due to a higher critical mach as well.

On another note, I don't see why Collins claim of "nearly 700 mph indicated airspeed" couldn't be true. He did not say that he was diving at an actual airspeed of 700 mph. You, of course, know what IAS means and I understand that the IAS device was often inaccurate at high speeds. In addition, I would not be surprised if there was a little exaggeration there. He did, however, clearly say that the P-47 was superior to the P-51 in a dive (and he flew both) and you indicated that the Corsair had a critical mach comparable to the P-51.

This is rather nitpicky, I know. I would agree with you that below 30K, the Corsair would have the edge and that that edge would be progressively greater as altitude decreased. Over 30K altitude though, I think the P-47 would wax the corsair.

Originally Posted by DAVIDICUS

RG_Lunatic:

You still haven't convinced me that, as you stated, "The Corsair was able to dive at speeds up to 550 mph IAS, which is faster than the max IAS of the P-47."

You now state, "The P-47N had a psuedo-laminar flow wing, so perhaps it's critical mach was equal to or higher than that of the F4U-4. Also, the F4U-4 had to be very careful above about 535 mph IAS or the fabric on the wings could be ripped off."

So it sounds like the P-47 would have an initial dive acceleration advantage due to weight and a likely terminal advantage due to a higher critical mach as well.

Initial dive acceleration would be pretty close. 535 IAS was about the limit of the P-47 as well. If the F4U's fabric had been tightened before the sortie, it could dive faster - the pilot had to pay attention for signs it was rippling.

Originally Posted by DAVIDICUS

On another note, I don't see why Collins claim of "nearly 700 mph indicated airspeed" couldn't be true. He did not say that he was diving at an actual airspeed of 700 mph. You, of course, know what IAS means and I understand that the IAS device was often inaccurate at high speeds. In addition, I would not be surprised if there was a little exaggeration there. He did, however, clearly say that the P-47 was superior to the P-51 in a dive (and he flew both) and you indicated that the Corsair had a critical mach comparable to the P-51.

I agree perhaps Collins' claim of the gauge being pegged could be true - if it was poorly calibrated for high speeds or was defective.

The P-47 would pull away from the P-51 quickly at the start of a dive, but then the P-51 would overtake it. This is a known fact from multiple flight tests. The Corsair would do better at the start of the dive than the P-51 because of its weight.

Originally Posted by DAVIDICUS

This is rather nitpicky, I know. I would agree with you that below 30K, the Corsair would have the edge and that that edge would be progressively greater as altitude decreased. Over 30K altitude though, I think the P-47 would wax the corsair.

Well, I agree with that. The Turbo-superhcarger on the N was still working well at 35K, the Corsair's was finished by about 30K.

=S=

Lunatic

Originally Posted by DAVIDICUS

RG_Lunatic:

My understanding was that the M2 was the standard gun used on U.S. aircraft throughout the war. ...

Just an additional note. The F8F-1 was armed with 4 x M3 .50 BMG's. This gave it the equivilant firepower of 6 x .50's that were deemed sufficient for air-to-air combat.

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Lunatic