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F4U-5 to 7 Corsair (Long nose) variants – some queries


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Nose length

 

Some publications are adamant  the F4U-7 was the same length as the F4U-4 and others that it was the same length as the F4U-5/AU1.

 

It is clear that the 7 inherited the AU airframe and its cheek cowling bulges.  It is possible that the extra 10” was removed between the wing and cooling flaps but as a minimal change variant, I would think this unlikely, since the panel tooling for the F4U-4 was probably gone by then. In any case the following statement would seem to knock the short nose theory on the head

 

From Lucien Dejeannot, F4U7 engine mechanic (1958-1961) at Telergma, French Algeria….

 

"The AU1 and the F4U7 were identical in size. When we use to disassembly the cowl parts, you could see very clearly the framework that was added on the lower sides to "reconstruct" the cheeks allowing the use of F4U5 & AU1 side cowls. We never received a "proper" F4U-7 spare [airframe] part catalogue. We used the AU1 one with some addition (mainly the ducting parts). We received in 1958 (if my memory is correct) a couple of "new" AU1 from the USA and they were (engine apart) VERY identical to the F4U7 we had. In some occasion, we did exchange cowl parts from AU1 to F4U7 without problem. Finally, be careful with museums. A friend of mine visited USA some time ago and he saw there one of our old U7 exposed...with a F4U4 engine and cowl which would maybe explain your confusion."

 

Leading edge intake slots

 

These were apparently different for all three variants.

 

With the separate cheek  carburetor air intakes in the nose, each F4U-5 leading edge intake slot (like on the F4U-4) now only supplied air to a front facing oil cooler matrix and, via three turning vanes, the intercooler buried behind the engine. 

 

F4U-5-Corsair.jpg

 

With the AU-1 there was a blanking panel where the oil cooler used to be and the three turning vanes, formally used to supply air to the now dispensed with intercooler, were now used to feed air to the buried oil coolers and (I assume in absence of cowling intakes) carburetor air as well (am I correct?).

 

For the F4U-7, the three guiding vanes were larger and spaced out evenly across the entire intake slot. I assume this fed air to the buried oil coolers and re-instated F4U-4 intercooler.  I assume that if the extra 10” (not required by the F4U-4)was retained, there was still room for both the re-instated intercooler and the AU-1 style buried oil coolers in the fuselage.

 

Alternatively (assuming the tooling for the wing root intakes had not been irretrievable altered) were the oil coolers moved back to the F4U-5 leading edge position with the guiding vanes providing a measure of small arms protection?

 

AU-1Inletvkitinlet_zpsc7b1f05a.jpg

 

The above modelling photo (in absence of any detail photos of actual slots) shows the F4U-7 arrangement on the left and AU-1 on the right.

 

The F4U-7 chin intake

 

It has been claimed elsewhere that when they stuffed the F4U-4's R-2800-43W into the AU-1 airframe to make the -7, they again needed intercooler space. The tooling for the wing root intakes had been irretrievable altered, since the AU-1 was the last planned variant and it was not economically feasible to retool for the limited number of French aircraft being purchased. So room was found for a single oil cooler in the nose, under the engine (thus the "chin" scoop was used to feed oil cooler air and engine combustion air was routed from the wing roots.

 

As I have said above in relation to the 7’s leading edge intake slots, I think the oil coolers would have been either

  • retained in the fuselage AU-1 style or
  • (assuming the tooling for the wing root intake tooling had not been irretrievable altered) moved back to the leading edge F4U-5 style where they were afforded at a cost of some cooling efficiency some protection from small arms fire by the guiding vanes .

 

My inclination is (assuming the nose length was as per the 5 and AU1 and therefore there was a spare 10" of space)  the oil coolers remained in the fuselage AU1 style and the chin intake was for carburetor air as per the F4U-4.

 

I assume that the F4U-5 cheek carburetor air scoops were not re-adopted because either the tooling for the cheek intakes had been irretrievable altered, or because the F4U-4s R-2800-43W auxiliaries set up, dictated a chin carburetor air scoop.  I would love to know either way. 

 

Simon

 

 

 

 

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Hi!

  The F4U-5 had the additional length, and the "cheek" intakes added due to the additional turbocharger added. The following is from a friend (since passed) who worked at Vought, building Corsairs. During F4U-5 production the tooling for the earlier round cowl versions was disposed of(scrapped, modified, I do not know). So when the Au-1 (originally the F4U-6 ) was proposed they only tooling for Corsair cowls were the F4U-5 tools. They plated over the intakes as they were not needed. As far as the wing intakes the oil coolers were moved further into the airframe and armored. The F4U-7 was the mating of the AU-1 airframe with a R-2800 which had some power at altitude. So -4 R-2800s were used to give decent performance both down low and at altitude. Since the -7 used the -4 R-2800, it needed the -4s carb intake, which was added under the cowl, which also had the "cheek" bulges.  .

   There are several "truths" we can gain from this. The F4U-5, 7 and AU-1 were all the same length, This length was 10" (+ or -) longer.

   Due to tooling changes the F4U-5,7 and AU-1 acquired "cheeks".

   The intakes and length increase of the F4U-5 was due to the turbo installation.

   The lack of intakes on the AU-1 (F4U-6) was due to an engine change to a low altitude R-2800. The wing intakes were changed to provide better protection from ground fire. The length remained unchanged and the cheeks were fro cowl tooling changes

   The F4U-4 style  carb intake was due to the use of the -4s R-2800. again the length remained unchanged and the cowl cheeks were from cowl tooling changes. The wing intakes, not needing to be armored were then changed to -4 style.

 

I do hope this answers most, if not all of your questions.

The Heller AU-1 and F4U-7 do not have the distinctive cheeks. I have not seen the other ( than Hasegawa)  F4U-5s so I cannot comment on them.

 

Bruce

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Thanks Bruce

 

So did the 7 have the AU1's extra armor added for protection from the small arms fire which would be encountered at the lower altitudes where the AU-1 would be working?

 

Since the 7 would also be down in the mud, I assume the 7 did too, along with the buried oil coolers, but you suggest not.  The F4U-4 had the same wing intakes as the 5 (i.e. front facing oil coolers and three guiding vanes to direct air to the intercooler)

 

Also where did the AU1 get its carburetor air from if not the wing intakes ala F4U-1s (no cowl intakes)?

 

Just trying to get a handle on the arrangement of things.

 

Regards

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A work in progress:

 

http://tailspintopics.blogspot.com/2017/04/the-last-propeller-pulled-corsairs-f4u.html

 

AU-1 carburetor air came from the wing inlets as did air to the oil coolers in the fuselage; I don't know about a blanking panel. The F4U-7s had one oil cooler in the lower fuselage just aft of the second row of engine cylinders fed by the chin inlet; my understanding is that the wing inlets provided air to the carburetor and the intercooler.

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So...after much research I am still as confused as I was before.

 

It seems the F4U-7 chin scoop either fed carburetor air as per the F4U-4 or oil cooler air to a uniquely placed oil cooler in the lower fuselage (apparently the extra 10" not needed for the F4U-4 engine arrangement didn't give enough space behind the engine for both an intercooler and one or both oil coolers).

 

It is also seems that the F4U-7 wing inlets were either the same as the AU1 or unique.  Feeding air to the intercooler and either one or more buried oil coolers or to the carburetor, depending on the purpose of the chin scoop.

 

At least I feel confident that the 7 was the same length as the 5 and AU1...unless someone wants to argue differently.

 

What I need to do is look at a 100% genuine F4U-7 and ask an engine mechanic 

 

Thanks all for your help though.

 

Simon

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6 hours ago, detail is everything said:

So...after much research I am still as confused as I was before.

 

It seems the F4U-7 chin scoop either fed carburetor air as per the F4U-4 or oil cooler air to a uniquely placed oil cooler in the lower fuselage (apparently the extra 10" not needed for the F4U-4 engine arrangement didn't give enough space behind the engine for both an intercooler and one or both oil coolers).

 

It is also seems that the F4U-7 wing inlets were either the same as the AU1 or unique.  Feeding air to the intercooler and either one or more buried oil coolers or to the carburetor, depending on the purpose of the chin scoop.

 

At least I feel confident that the 7 was the same length as the 5 and AU1...unless someone wants to argue differently.

 

What I need to do is look at a 100% genuine F4U-7 and ask an engine mechanic 

 

Thanks all for your help though.

 

Simon

Well, maybe this will set your mind at ease about the purpose of the F4U-7 chin scoop.

F4U-7OilCoolerDwg_zps2n4unn2t.jpg

 

With respect to the respective configurations of the AU and F4U-7 wing inlets, the best photos I've found have been added to my F4U-5/AU-1/F4U-7 post. All I can say for sure is that only the -5 had the oil coolers there. The other two appear to have three turning vanes and one or two structural posts but my impression is that the configurations are not identical.

Edited by Tailspin Turtle
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Quote

One last thing I noticed was that the wing root intake was different between the AU1 and the F4U7. The AU1 was like the F4U5 minus the oil cooler, but the F4U7 had the "blades" evenly spaced all over the intake.

 

A quote from an ex- French mechanic, found in this thread on Hyperscale.  There's more about shape details in his quotes, so worth looking (they're all in one post by Don Fenton).

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