P-38 Floatplane

[KJ_Lesnick]

PR19_Kit

Lockheed were hardly likely to fit it with larger radiators just for the hell of it, were they?

Good point, I mistyped: What I meant was the radiator design of the earlier P-38 doesn't look like the radiator design used on other aircraft such as the following

• Hawker Hurricane
  
• Supermarine Spitfire
  
• P-39 Intercooler Radiator: It was mounted on the P-39 prototype and was on the right side of the fuselage
  
• P-38 Intercooler Radiator: Mounted on the booms
  
• P-40
  
• P-51
  

Which were based around the idea of using the heat from the radiator to produce a ramjet effect and appeared more jet intake like...

[jcf]

The boom radiators on the P-38 are the engine cooling radiators, bupkis to do with the intercoolers.
On the 'smooth-chin' P-38s the inter-cooling was done via the wing leading edge, on the 'big-chin'
models they put core type intercoolers in the enlarged chins, it's why they went to the 'big-chin'.

[kitnut617]

I'm curious why the P-38 had the original radiator design that it did and not something bigger?

weight distribution also came into play ---

[wuzak]

Remember that the radiators weren't sized for WEP or Military Power, but for normal or cruise powers.

[KJ_Lesnick]

Wuzak

Remember that the radiators weren't sized for WEP or Military Power, but for normal or cruise powers.

1. Is this normal for most planes of the era?

2. The banana-tailed design is said to have provided no improvement at higher mach performance: Yet, at least some work was done on a redesigned tail-plane (longer chord) and, according to Secret Projects, it was said to increase max mach number to 0.75 supposedly...


joncarrfarrelly

The boom radiators on the P-38 are the engine cooling radiators, bupkis to do with the intercoolers. On the 'smooth-chin' P-38s the inter-cooling was done via the wing leading edge

Now that, I did not know...

on the 'big-chin' models they put core type intercoolers in the enlarged chins, it's why they went to the 'big-chin'.

Why did they use the smooth design shape to begin with?  The typical radiators of the day seemed to be more like the core-type (an intercooler radiator is a radiator)

[KJ_Lesnick]

Oh, I have two other questions to ask

Fuel Capacity

• Early on the P-38's fuel load was fairly low compared to later on
  
• Part of it had to do with the position of the oil-coolers: Which were initially in the wing leading-edge
  
• Why were the oil coolers placed in the leading edge and not on the nacelles (the B-24 had them on the nacelles if I recall)
  

.
Maneuvering Flaps

• Did the early P-38's have fowler-flaps, or was that added with the P-38F (I know the P-38 was the first to use a maneuver setting, but I'm not sure if they all had fowler flaps or not)
  
• While I know that the maneuver flap setting was added to help tighten up the rate of turn at high altitudes: I'm curious why they didn't realize they had a rate of turn issue earlier?
  

[wuzak]

Wuzak

Remember that the radiators weren't sized for WEP or Military Power, but for normal or cruise powers.

1. Is this normal for most planes of the era?

2. The banana-tailed design is said to have provided no improvement at higher mach performance: Yet, at least some work was done on a redesigned tail-plane (longer chord) and, according to Secret Projects, it was said to increase max mach number to 0.75 supposedly...

1. Yes.

Even the hotes fighters spent most of their time in cruise settings. The extra size and weight of coolers meant for military or war emergency power would cause extra drag, reducing range, etc. Engines could live being warmer for short periods.

Also, many engines weren't given WEP ratings until later on.

2. The mach limit was largely due to the main wing.

However, some of the issues that the P-38 had were due to the turbulent wake from the wing interfering with the elevator. Moving the stabilizer and elevator higher might reduce the problem.

The banana booms wouldn't be necessary (and probably structurally difficult) - the stabilizer could put atop the vertical stabilizers.

[wuzak]

joncarrfarrelly

The boom radiators on the P-38 are the engine cooling radiators, bupkis to do with the intercoolers. On the 'smooth-chin' P-38s the inter-cooling was done via the wing leading edge

Now that, I did not know...

on the 'big-chin' models they put core type intercoolers in the enlarged chins, it's why they went to the 'big-chin'.

Why did they use the smooth design shape to begin with?  The typical radiators of the day seemed to be more like the core-type (an intercooler radiator is a radiator)

Oh, I have two other questions to ask

Fuel Capacity

• Early on the P-38's fuel load was fairly low compared to later on
  
• Part of it had to do with the position of the oil-coolers: Which were initially in the wing leading-edge
  
• Why were the oil coolers placed in the leading edge and not on the nacelles (the B-24 had them on the nacelles if I recall)
  

The oil coolers were mounted under the spinner in the early "smooth" nose P-38s.

The intercoolers on early models were in the leading edge. When they moved to the core type intercoolers they added extra fuel tanks in the wings.

[KJ_Lesnick]

1. Yes.

Okay...

Also, many engines weren't given WEP ratings until later on.

When did that start in the US, UK, and Germany?

2. The mach limit was largely due to the main wing.

Well some loss of control has to do with turbulent flow hitting the tail; some has to do with shockwaves themselves forming on the tail, depriving it of smooth air; then there's the loss of the downwash going away as the shockwave moves further back and interrupts it (the tail is deprived of most of it's load)

However, some of the issues that the P-38 had were due to the turbulent wake from the wing interfering with the elevator. Moving the stabilizer and elevator higher might reduce the problem.

It was moved higher and would take it partially out of the worst of the wake; the chord was also increased, making it thinner so shockwaves wouldn't form as quick across the tail.

The tail being higher would also give it more lever arm (leverage applies if you're further left, further right, further back, or further above and below the center of gravity)

The banana booms wouldn't be necessary (and probably structurally difficult)

In terms of weight (and thus CG), aeroelasticity, or both?

the stabilizer could put atop the vertical stabilizers.

Like a T-tail?

The oil coolers were mounted under the spinner in the early "smooth" nose P-38s.

The intercoolers on early models were in the leading edge. When they moved to the core type intercoolers they added extra fuel tanks in the wings.

Wait... I thought the intercoolers were under the engine; the oil-coolers were in the leading edge?

[jcf]

The inter-coolers and oil-coolers are under the engine on the 'big-chin' models (P-38J and on),
oil-coolers only on earlier variants (P-38 through P-38H) with the inter-cooling via the wing
leading edge.

[KJ_Lesnick]

joncarrfarrelly

The inter-coolers and oil-coolers are under the engine on the 'big-chin' models (P-38J and on), oil-coolers only on earlier variants (P-38 through P-38H) with the inter-cooling via the wing leading edge.

1. Was there any demand for great range on the P-38 early on?

2. Was it technically possible to have the intercooler and oil-coolers under the engine early on (1939 to 1941)?  I'm pretty sure the P-51 (B/C/D at least) had an intercooler intake under the engine, the main radiator under the wing and oil-cooler flaps on the rear fuselage.

[wuzak]

joncarrfarrelly

The inter-coolers and oil-coolers are under the engine on the 'big-chin' models (P-38J and on), oil-coolers only on earlier variants (P-38 through P-38H) with the inter-cooling via the wing leading edge.

1. Was there any demand for great range on the P-38 early on?

2. Was it technically possible to have the intercooler and oil-coolers under the engine early on (1939 to 1941)?  I'm pretty sure the P-51 (B/C/D at least) had an intercooler intake under the engine, the main radiator under the wing and oil-cooler flaps on the rear fuselage.

1. I believe that the P-38 met the range demands at the time.

2. The P-51's intercooler radiator was mounted with the engine radiator.

The oil coolers were ahead of the radiators, low in the scoop.





The scoop under the spinner is for the engine intake



The P-51 intercooler (termed aftercooler in the first image) was different to the P-38's because it was liquid to air instead of air to air.

I found a couple of pictures of Allison installations at Engine History:
http://www.enginehistory.org/Allison/V-1710Details/index.html

P-51:
http://www.enginehistory.org/Allison/V-1710Details/allisonv1710installationinp51.jpg (oil cooler in centre of radiator)

P-40:
http://www.enginehistory.org/Allison/V-1710Details/allisonv1710installationinp40.jpg

P-38:
http://www.enginehistory.org/Allison/V-1710Details/allisonv1710installationinp38.jpg
(note the leading edge intercoolers shown in orange)

[KJ_Lesnick]

1. I believe that the P-38 met the range demands at the time.

Understood

2. The P-51's intercooler radiator was mounted with the engine radiator.

Did the technology exist (or the desire) to place the intercooler and oil-cooler in an arrangement where they'd share a single scoop?

The oil coolers were ahead of the radiators, low in the scoop.

Fascinating...

The scoop under the spinner is for the engine intake

Gotcha

The P-51 intercooler (termed aftercooler in the first image) was different to the P-38's because it was liquid to air instead of air to air.

So air is used to cool the intercooler, transfer the heat to the radiator; then carry away the heat?

I found a couple of pictures of Allison installations at Engine History:
http://www.enginehistory.org/Allison/V-1710Details/index.html

I'm looking at this

P-51:
http://www.enginehistory.org/Allison/V-1710Details/allisonv1710installationinp51.jpg (oil cooler in centre of radiator)

P-40:
http://www.enginehistory.org/Allison/V-1710Details/allisonv1710installationinp40.jpg

P-38:
http://www.enginehistory.org/Allison/V-1710Details/allisonv1710installationinp38.jpg
(note the leading edge intercoolers shown in orange)

None of these work...

[wuzak]

2. The P-51's intercooler radiator was mounted with the engine radiator.

Did the technology exist (or the desire) to place the intercooler and oil-cooler in an arrangement where they'd share a single scoop?

Yes - the P-51 did just that.

The P-51 intercooler (termed aftercooler in the first image) was different to the P-38's because it was liquid to air instead of air to air.

So air is used to cool the intercooler, transfer the heat to the radiator; then carry away the heat?

I believe what you see here is that the intercooler radiator occupied the left hand (from this angle) 1/3 of the radiator assembly, while the the other 2/3 is the engine radiator.

Just typing this I get what you were asking....

The air exiting the supercharger goes through the inter/aftercooler - which is like a radiator, except that it works in reverse. That is, the liquid takes heat from the air. This is then pumped down to the intercooler radiator where the air stream passes through the core to cool the liquid down again.

In effect the Merlin had an intercooler (cooler between compressor stages) and an aftercooler (cooler at the exit of the compressor). The big boxy aftercooler sat on top of the engine, behind the cylinder banks. The intercooler was formed by cooling passages in the supercharger involute casing.



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.

P-51:
http://www.enginehistory.org/Allison/V-1710Details/allisonv1710installationinp51.jpg (oil cooler in centre of radiator)

P-40:
http://www.enginehistory.org/Allison/V-1710Details/allisonv1710installationinp40.jpg

P-38:
http://www.enginehistory.org/Allison/V-1710Details/allisonv1710installationinp38.jpg
(note the leading edge intercoolers shown in orange)

None of these work...

These pictures are all on the AEHS page:

I found a couple of pictures of Allison installations at Engine History:
http://www.enginehistory.org/Allison/V-1710Details/index.html

I'm looking at this

[KJ_Lesnick]

wuzak,

These pictures are all on the AEHS page

Okay...

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?

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

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?

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.