P-38 Floatplane

[wuzak]

Looking at the P-51 design: I basically get the layout so that's good.  What is surprising is how much coolant is used!  Is the coolant factored into the operational empty weight?

If engine coolant is then, yes, the intercooler coolant will be too.

I don't actually have any idea of what is included in operational empty weight as it certainly varied between countries and probably between manufacturers.

Looking at the P-40 design: Considering the oil-cooler and radiator were occupying the same scoop, I assume the P-38 could have used the same arrangement -- it would have freed up the wings

The radiators for the P-38 were never on teh wings, so grouping them with the oil cooler would not free up anything.

The intercoolers were mounted in the outer wing leading edges, the idea being that they would sufficiently cool the compressed air while not requiring and intakes or protuberances for cooling, all of which would add drag.

The problem was when the engines got over 1100-1200hp there was insufficient cooling in the intercoolers for the higher rating. The P-38H used the same engines as early blocks of the P-38J but could not use the higher power rating at high altitudes (at lower altitudes there was a lower pressure ratio required from the turbo's compressor and the air was heated less and needed less intercooling).

Looking at the P-38 diagrams: At the penalty of sounding idiotic -- if it's an air-to-air intercooler, what's the liquid coolant for?

Engine coolant. The radiators for which are mounted on the booms.

The advantages of the liquid to air intercooler are the shorter air path from engine to supercharger, the ability to remote mount the intercooler radiator and the smaller size of that radiator compared to air to air types.

I'm confused: If a liquid-to-air cooler allows for a remote-mounted intercooler radiator -- then wouldn't an air cooled design have an intercooler and radiator in one?  Unless I misunderstood, or you got this backwards, it doesn't seem to make sense.

Take the P-51. You could use an air to air intercooler for the compressor, and you could locate it in the rear scoop as was the actual intercooler radiator. But then you would have to duct air all teh way back to the intercooler and then all the way forward to the engine. Each of these ducts would be substantially larger than the coolant lines in the actual P-51. The intercooler radiator would also be bigger than the coolant radiator, so extra drag there.

The air to air type was, in general, in close proximity to teh compressor feeding it.

That doesn't really apply to the P-38, as it is a long path between the turbo and teh wing intercoolers, and an even longer one to the front mounted core type intercooler.

The F4U for example


The P-47 had the turbo remote, so though the intercoolers were relatively close they still needed ducts to go back to the engine.

The XP-39 had the intercooler close


While the XP-37 stuffed both the engine cooler and intercooler behind the engine, requiring the cockpit to be moved back.

[KJ_Lesnick]

Everybody

Do you guys have any idea how much radius and range the P-38E's had provided they carried drop-tanks?


wuzak

If engine coolant is then, yes, the intercooler coolant will be too.

Okay

The radiators for the P-38 were never on teh wings, so grouping them with the oil cooler would not free up anything.

The intercoolers were mounted in the outer wing leading edges

Sorry -- what I meant

the idea being that they would sufficiently cool the compressed air while not requiring and intakes or protuberances for cooling, all of which would add drag.

Okay

The problem was when the engines got over 1100-1200hp there was insufficient cooling in the intercoolers for the higher rating. The P-38H used the same engines as early blocks of the P-38J but could not use the higher power rating at high altitudes (at lower altitudes there was a lower pressure ratio required from the turbo's compressor and the air was heated less and needed less intercooling).

I thought it freed up fuel?

Engine coolant. The radiators for which are mounted on the booms.

Okay...

Take the P-51. You could use an air to air intercooler for the compressor, and you could locate it in the rear scoop as was the actual intercooler radiator. But then you would have to duct air all teh way back to the intercooler and then all the way forward to the engine. Each of these ducts would be substantially larger than the coolant lines in the actual P-51. The intercooler radiator would also be bigger than the coolant radiator, so extra drag there.

The air to air type was, in general, in close proximity to teh compressor feeding it.

Okay


BTW: Do you have an answer of exactly what kind of structural problems would have existed with banana booms?

[wuzak]

BTW: Do you have an answer of exactly what kind of structural problems would have existed with banana booms?

No.

Thyey just look more complicated and heavier to me.

[wuzak]

The problem was when the engines got over 1100-1200hp there was insufficient cooling in the intercoolers for the higher rating. The P-38H used the same engines as early blocks of the P-38J but could not use the higher power rating at high altitudes (at lower altitudes there was a lower pressure ratio required from the turbo's compressor and the air was heated less and needed less intercooling).

I thought it freed up fuel?

Well, yes, when they moved the intercooler they took the opportunity to add more tankage.

But the change was made for performance reasons. If the usable engine power didn't increase more than enough to overcome drag the performance would have fallen away a little.

Remember that during the design period for the P-38J the USAAF still did not believe that a long range escort was necessary.

[KJ_Lesnick]

Wuzak

No.

Oh well...

Thyey just look more complicated and heavier to me.

1. Could you make a guess as to how much weight it would have added?

2. When exactly did NACA/USAAF and so on, realize that the problems with the plane wasn't flutter but compressibility?

Well, yes, when they moved the intercooler they took the opportunity to add more tankage.

So, if range was more important earlier on: This would have been more creative?

But the change was made for performance reasons. If the usable engine power didn't increase more than enough to overcome drag the performance would have fallen away a little.

How much would you say?

Remember that during the design period for the P-38J the USAAF still did not believe that a long range escort was necessary.

Well, they were idiots LOL

BTW: Did the original flaps have a fowler arrangement, or was that only with the maneuvering flap config?