Best World War II Aircraft?

[drgondog]

Originally Posted by renrich

A little far afield but I have often speculated that overall the Corsair might have been the best fighter in the US arsenal. Began thinking about some readily accomplished modifications which would have made the Corsair more suitable for the ETO and lightening the AC by removing the tail hook and making the wing non folding would have resulted in a little less weight and better performance.
Actually there were a number of Corsairs built by Goodyear that did not have tailhooks or folding wings and I have never seen any tests of that model which show how the weight loss affected it's performance. The F4U1 had wing tanks, not self sealing but with a CO2 purge system. It had an internal fuel capacity of 361 gallons which gave it a "yardstick" range of around 1500 miles. A realistic combat radius of around 550 miles was possible off of land bases with that fuel load.
The original XF4U had two MGs mounted above the engine. The F4U1 production AC had the fuselage lengthened by around 3 feet so that fuselage fuel tank counld be accomodated and the guns removed to the wings with the six fifties supplied with 400 rounds each except for the two outboard guns which had 375 rounds each because of wing taper.

Ren - it was this mod (extending fuselage and removing cowl guns/ammo) that enabled the 240 gallon fuse tank to be added. Additionally the 4x 50 and 6x50's had to be positioned outboard of the wing fuel tanks to keep roll performance in line with the added weight of the wing armament/ammo over the XF4U

Now comes the modification which might have made it the premier US fighter, ( if it wasn't already.) Delete the MGs in the wing and mount two 50 BMGs above the engine with 500 rounds each. Remove the accursed, infamous oil cooler from the wing root and place it behind the engine like the Hellcat and mount two 20 mm cannon, one in each wing root, with 150-200 rounds per gun, like the FW190, all guns synchronised with the prop. The guns therefore would throw all projectiles into about a 5 foot square and the g-load jamming problems of wing mounted guns would be eliminated.

I believe this suggested mod has two serious disadvantages. First and foremost adding the nose armament and oil cooler back to the airframe also removes most or all of the forward fuel tank space... even if forward fuel tank has some capacity there will then continue to be a possible cg issue as all fuel and all forward ammo is expended - I suspect this would not be serious, however - not as serious as removing/reducing the main fuel tank

The second serious issue is the the inboard wing tanks must be replaced by the newly installed inboard 20's so, to maintain the range, not only must that tank be entirely replaced outboard of the Gull section (and landing gear), but the lost fuel due to the new nose armament must also be relocated - I would estimate that nearly all of the F4U fuel in this config has to buried outboard of landing gear (opposite of Mustang) - which would really screw up roll performance. The 51 had 184 gallons inboard of the 50's, the F4U would be looking at 300-360 outboard of the landing gear.


The resulting space in the wings could be used for larger self sealing fuel tanks. I estimate that at least enough additional fuel could be carried to allow a 2000 mile "yardstick" range. That would give it a combat radius of around 750 miles on internal fuel only. Even longer range would result with belly tanks. All these modifications could have been accomplished without radical redesign. Any body have comments? LOL

So, these are my thoughts about the improvement ideas.

To get 400 plus gallons in the a/c in this notion, the fuse probably has to extended to be able to put more fuel aft of cockpit for both space and cg, the winspan probably has to increase ~ 5 feet to jam the fuel into a tapering wing outboard of the gear, and get rid of USN carrier qual as result of gross weight, and low speed performance due to the weight increase of extra wing span, wing fold issues, added weight of fuse and wing structure as you shift weight away from the cg.

God knows how it now handles in ACM although extra wing with fuel gone makes it climb and turn better - but significanly less manueverable in first half of mission - and lower payload, longer run on takeoff.

I like the Corsair that actually flew - better.

[renrich]

Bill, many thanks for your, as usual, well informed post about my adventure into aircraft redesign. I have a cutaway drawing of the production Cosair which shows a bay with accesory equipment in it, just in front of the fuel bay and just behind the engine. It looks to me that the prototype, I don't have a cutaway of it, had that same space and it looks in photos like the top of that space was where the receivers of the MGs and ammo was located with the barrels of the MGs passing over the engine and the rounds exiting though holes in the outward edge of the engine cowling. In the production models, the MG receivers and ammo belts would be positioned in that upper portion of the bay in front of the fuel tank bay, just aft of the leading edge of the wing, thus possibly not causing much of a shift in CG with ammo use and the fuselage fuel tank would remain the same. The prototype carried 273 gallons of fuel in the wings, all outboard of the landing gear, I believe. The production models had 62 gallons in each wing for a total of 124 gallons in the wings. If the wing tanks in my hypothetical AC carried say 230 gallons in the wings, factoring in capacity lost for SS tanks or even 273 gallons if the tanks had the CO2 purge system, the range would get a significant boost. In the escort role, the wing tanks would be full and used first, just like the 85 gallon tank aft of the pilot in the P51 and just like what the F4U1 did with the 124 gallons in the wings. In other roles where the additional range was not needed, the wing tanks would be empty. With the wing guns deleted except for the 20 mms in the wing roots and with wing tanks empty, would not the Corsair have an increased roll rate? In the cutaway, since I know the Corsair fuselage was extended around three feet to accomodate the fuselage fuel tank, the bay for the accesories and the bay for the fuel tank both look to be about three feet long, which would accomodate the receivers for the 50 BMGs. Not sure about ammo storage but the prototype had room for it without the fuselage extension. Also the cutaway shows the wing root section looks to be empty space behind the wing spar so the two cannon look like there is room for them, one in each wing root. Not being an engineer, much less an aero engineer, I am probably all wet, but I am having fun with it. Bill, what say you?

[renrich]

Another point about the Corsair which occurs to me while looking at the cutaway drawing is the infamous oil cooler. The oil cooler is located just inside of the outboard edge of the intake opening in the port wing root. The inboard edge has an intake for the intercooler for the supercharger. The oil cooler is connected to the oil tank, 20 gallon capacity, which is mounted just forward of the fuselage fuel tank and is protected in front by a piece of armor and from behind and above by the fuel tank armor. The oil cooler and this is approximate, looks like about a foot in diameter and about a foot deep. Looks like a small target to me but there are also the oil lines connecting it to the oil tank. (An aside, a cutaway of the Hawker Sea Fury shows the oil cooler in the same location.) I don't know if there is an oil cooler in the starboard wing root or not but my guess is there is not.

There has been a lot of debate here about that oil cooler and whether or not it played a significant role in losses of the Corsair in WW2 and Korea. It seems to me that looking at the AC as a whole, that the oil cooler and the lines connecting it to the tank represent a very small portion of the F4U as a target. Kind of like the brain of an elephant. One may recall that Karamojo Bell killed a lot of elephant with a 6.5 Mannlicher and a 7x57 Mauser. That record would indicate that an elephant is easy to kill. Looking closer though, Bell killed his many elephants when they were very plentiful and he got so close that the muzzle was practically in the ear and that very small, long and puny bullet only had to penetrate some soft tissue to destroy the brain. Trying to make that shot from 75 or 100 yards would be a matter of luck. It seems to me that looking at the relative vulnerability of the Corsair and it's oil cooler versus the Hellcat or Jug with their oil cooler locations doen't give a very big edge to the Hellcat or Jug. In other words, how often, when those aircraft are being shot at do the oil coolers actually get hit. To me, the coolant system in a liquid cooled engine would be a much, much, larger target.

[drgondog]

Ren - I can't make an informed comment as I don't have the drawings of the Xf4U and F4U -1 in front of me.

Off hand - replacing each 62 gallon wing tank with an inboard 20mm cannon plus ammo is a fair trade off . The swap of 3x 50 plus the ammo for the outboard fuel tanks is not as good a trade until about 1/3 of the fuel is burned away.

There was a lot of fuselage space for the 85 gallon tank and it took up about 3 feet back there (for 11 cubic feet of fuel). The cross section of the corsair was larger but I still wonder how much fuel could be accomodated in addition to oil cooler ducting and cooler plus guns/ammo. There is an additional question about ducting and heat transfer over the oid cooler as it would be in a fairly hot environment behind the engine

[renrich]

In retrospect, I think the oil cooler should stay where it was originally located like an elephant's brain. The bay where the 50 BMGs would be located contains the following: a hydraulic reservoir, supercharger housing, fire suppressor cylinder, the oil tank and armor, intake air duct for supercharger, the intercooler for the supercharger and some engine support frames. I assume that the XF4U had the same bay with the same accesories and the 2 MGs located right behind the engine. If you delete the 6-50s from the wings and 2350 rounds you lose 1125 pounds. If you add 2-20mms plus 200 rounds of ammo each you add 504 pounds and 2- 50s plus 1000 rounds adds another 440 pounds for a net loss of 176 pounds.If you add the wing tanks with 230 gallons of fuel instead of 124 gallons your net gain in fuel weight is around 600 pounds plus a little more for bigger wing tanks but the loss of 176 pounds in guns and ammo offset that a little. So, in the escort role the Corsair with full internal fuel would be carrying an additional weight of around 500 or so pounds. Since the Corsair could carry an exterior bomb load of easily 2000 pounds, that 500 pounds extra would not be a problem at all for a landbased ETO escort fighter. Now, I am not saying the ETO optimised Corsair I am proposing would replace the P51 B, C or D but rather supplement it and perhaps be available for long range escort 6 months before the Mustang.

[drgondog]

The F4U was my second favorite Allied fighter for all the reasons stated here... with respect to ETO I think it would have done as well or better than the P-47 but reminded that its best performance altitude was closer to Fw 190 and Me 109 than the P-51 and that the 51 was best where the LW had to play with the bombers..

[renrich]

Agree Bill. Actually, one of my sources says the Xf4u was initially armed with a 30 cal and 50 cal in the nose and a 50 cal in each wing. It also had small bomb bays in the wings besides the fuel tanks. I did not know that about the wing mounted MGs in the prototype. The prototype was 31 feet 11 inches long and the F4U1 was 33 feet 4 and three quarters inches long.

[Civettone]

Originally Posted by drgondog

Kris - That might have been his theory but probably without merit. All aircraft lose energy in a turn, but as long as the thrust available exceeds the amount required for that manuever it can maintain energy...and the F4U had plenty of power (and plenty of drag)

What causes the stall is when the bank angle and speed force an approach to maximum CL for the wing to provide the vertical lift component to sustain level flight - but that point is difficult to predict in theory and even more difficult to substantiate and repeat in flight tests. There are too many factors involved (trim drag, spanwise flow, aileron reversal, aeroelastic effects, etc)

What is possibly true is that the outboard gull section could be adding a very slight increment to the vertical lift component of the wings - but conversely the inboard (down wing) section should stall out first... so hard to know.

Additional considerations regarding the effectiveness of the Gull sections is that both up and down wing sections are totally immersed in the turbulent flow behind the prop.

In short I doubt it - but remain open minded to the possibility.

Yeah I don't know either ...

Kris