P-51 internal fuel capacity (how?)

[gjs238]

How come the P-51 had such a large internal fuel capacity relative to other fighters interceptors?
Was it a larger aircraft?
Was construction lighter, freeing up internal space?
Did the designers figure out a more space-efficient way to arrange internal components?

 

[drgondog]

How come the P-51 had such a large internal fuel capacity relative to other fighters interceptors?
Was it a larger aircraft?
Was construction lighter, freeing up internal space?
Did the designers figure out a more space-efficient way to arrange internal components?

It was rare in that the original design placed large fuel tanks (internal) in wing (92 gallons each) and wing racks capable of 750 pounds in P-51A. Most contemporary fighters put all fuel tanks in fuselage (P-47, F4U, Bf 109, Spitfire, etc).. P-38 of course had internal wing tanks also

The P-47 didn't get to that design until 1944 in the late D models - which is why the 8th converted to all Mustangs except 56th FG. There is no teeling how large the run up of scores would have been if the 56th had not been cut out of the big air battles deep in Germany during 1944.

It (51BC) evolved to include an 85 Gallon fuel tank in the fuselage and get 1000 pound capacity wing racks (P-51D/K) - the latter capable of 160 gallon Ferry tanks or 108/75 for standard ops.

 

[davparlr]

How come the P-51 had such a large internal fuel capacity relative to other fighters interceptors?
Was it a larger aircraft?
Was construction lighter, freeing up internal space?
Did the designers figure out a more space-efficient way to arrange internal components?

Compared to other American aircarft, the P-51 had a relative light internal fuel load.

P-38J 410 gal

P-47D-20 305 gal

F4U-1 351 gal

P-51D 269 gal

The P-51 was a very aerodynamically clean aircraft which allowed it to get great performance out of each gallon.

 

[Airframes]

All of the above is, of course, spot on. The biggest single advantage of the P51, regarding range, was the efficiency of the laminar flow wing. Also, due to the design of the fuselage, the placement of the cooling system etc, there was room to fit the fusealge tank, behind the pilot, which increased the range still further, although not without some handling problems, until at least half (?) the fuel in that tank had been used. Earlier designs, the Spitfire and Bf109 being prime examples, had been designed to meet the requieremnts of the time (pre war), that is, a short-range interceptor, and had never been envisged as having to fly great distances on, for example, escort missions. Wheras the P51, from the outset, was designed with range and endurance in mind, which even then, was improved as the needs dictated.

 

[MikeGazdik]

While the laminar wing design did in fact give the Mustange great performance, it was the decision of the North American engineers that placed the main tanks between the forward and aft spars of the wing. This enabled a much greater fuel load vs other Liquid cooled aircraft. (Spitfire, Messerschmitt} The other aircraft carried thier main fuel load in the fuselage. Which was the secondary area the later Mustangs used to add to thier fuel capacity.

I think that the decidsion to carry the fuel in the wings, may be one of the biggest acheivements of the Mustang. If it did not have the great range, it would have been just another fighter. The range gave it the ability to be used over enemy territory, which was not possible ( except for the P-38 ) in any other front line fighter.

 

[gjs238]

While the laminar wing design did in fact give the Mustange great performance, it was the decision of the North American engineers that placed the main tanks between the forward and aft spars of the wing. This enabled a much greater fuel load vs other Liquid cooled aircraft. (Spitfire, Messerschmitt} The other aircraft carried thier main fuel load in the fuselage. Which was the secondary area the later Mustangs used to add to thier fuel capacity.

I think that the decidsion to carry the fuel in the wings, may be one of the biggest acheivements of the Mustang. If it did not have the great range, it would have been just another fighter. The range gave it the ability to be used over enemy territory, which was not possible ( except for the P-38 ) in any other front line fighter.

Didn't one version of the F4U place fuel in the wings, with mixed results?

 

[davparlr]

Didn't one version of the F4U place fuel in the wings, with mixed results?

The F4U-1 had two 57 gallon wing tanks. The F4U-1D, and on, did not have these tanks. I have no information on issues with these tanks other than their removal.

 

[drgondog]

Compared to other American aircarft, the P-51 had a relative light internal fuel load.

P-38J 410 gal

P-47D-20 305 gal

F4U-1 351 gal

P-51D 269 gal

The P-51 was a very aerodynamically clean aircraft which allowed it to get great performance out of each gallon.

Note: P-38 had two inline engines so in comparison the 51 had quite a bit more fuel.

The 47 and F4U had gas guzzling Piston engines, so by comparison the 51 had an advantage ther also.

But of course Drag was the key.

 

[GrauGeist]

In regards to drag, I've heard the expression that the P-51D "sliced through the air, like a knife" and if this is the case, then the P-47D simply "tore a hole in the sky, and shoved it's way through"

 

[Shortround6]

Note: P-38 had two inline engines so in comparison the 51 had quite a bit more fuel.

The 47 and F4U had gas guzzling Piston engines, so by comparison the 51 had an advantage ther also.

But of course Drag was the key.

Actually in cruise settings the the P-47 and Corsair engines may have burned a trife less fuel per horsepower hour and thus been , in one way, more efficient.
They were just making a lot more horse power in cruise settings to begin with

P-51 was designed to be better than a P-40.

Even early P-40s had tankage for 160 US gallons of fuel internal.
Late model Brewster Buffalos had tankage for 240 US gallons which might have been part of their problem.

 

[MikeGazdik]

The point of what I was trying to imply, is that because of the fuel in the wings design of the Mustang, it lent itself to more easily be modified and given additional fuel in the fuselage. The internal space of the wings on most of the single engine fighters were used in a way that once into production, only small changes could be made to make them adapt. Maybe change out a machine gun for a cannon, or in some cases add leading edge tanks to the wings.

But a wholesale change to making the wing the primary fuel storage area was not possible without a complete change in at least the wing design. ( such as the P-47N) So with that fact the Mustang, though it had good range out the outset, was able to expand even more with the addition of the fuselage tanks.

The wing was really THE greatest part of the Mustang, both in airfoil and in the internal structure, which was stong yet light and enabled the aircraft to carry a large amount of fuel. ( yes, I know there may be an argument about the Merlin engine being the greatest aspect)

 

[Elvis]

On top of aerodynamics, I've heard a few times in the past, that the P-M engine was actually quite thrifty with the fuel, in cruise mode.
It was a combination of both of those factors that allowed the plane to have the long range that it did have.

Also, I understand that the little internal tank, located behind the piilot, came into being because technology had progressed enough that the radio in that plane could be shrunk down with no detriment to performance.
This opened up a cavity and it was decided to put fuel in there.
This idea could've coincided with the P-51 being picked for bomber escort duty into Germany, but on that point, I'm mearly speculating.


Elvis

 

[Milosh]

A 'little internal tank' Elvis?

It is half again as big as this 55gal drum.

 

[davparlr]

On top of aerodynamics, I've heard a few times in the past, that the P-M engine was actually quite thrifty with the fuel, in cruise mode.
It was a combination of both of those factors that allowed the plane to have the long range that it did have.

Elvis

The P-51 was much cleaner than the P-47 or F4U and thus required less HP to cruise. So, even at equal efficiency, the P-51 would use less fuel. I think this advantage would reduce as altitude increased, however, engine efficiency at altitude also becomes a factor so a blanket statement like this is risky.

 

[drgondog]

The P-51 was much cleaner than the P-47 or F4U and thus required less HP to cruise. So, even at equal efficiency, the P-51 would use less fuel. I think this advantage would reduce as altitude increased, however, engine efficiency at altitude also becomes a factor so a blanket statement like this is risky.

Very true. Period. I believe the 51 had it way over both of those ships up to critical altitude respectively, both for reasons of drag and also the fuel consumption for each ship in optimal range cruise speed.

IIRC the optimal cruise (range vs loiter) for the 51D (and B-10 and -15) with the 1650-7 was around 16-17K at 27" and 2000 rpm. As you well know the optimum is influenced by payload but that fuel consumption was around 48gpm. I'm goind to have to dig but I believe the fuel consumption for cruise speed for optimal range for both the F4U and P-47 were about 35-40% higher.

 

[drgondog]

On top of aerodynamics, I've heard a few times in the past, that the P-M engine was actually quite thrifty with the fuel, in cruise mode.
It was a combination of both of those factors that allowed the plane to have the long range that it did have.

Also, I understand that the little internal tank, located behind the piilot, came into being because technology had progressed enough that the radio in that plane could be shrunk down with no detriment to performance.
This opened up a cavity and it was decided to put fuel in there.
This idea could've coincided with the P-51 being picked for bomber escort duty into Germany, but on that point, I'm mearly speculating.


Elvis

Elvis - The command radio for the P-51, A-36, P-51A and P-51B/C and P-51D/K were the SCR-274 with variations including the SCR 522 from P-51A through P-51D/K. In other words the radio behind the pilot didn't change - the fuse tank wasn't placed there in the P-51A and prototype B only because of the cg issue.

 

[Elvis]

Hey, guys, it's what I've heard.
Please, don't shoot the messenger.
If that's incorrect, fine. I was only trying to help shine some light on the initial question.
---------------------------------------------------------------

Daveprlr,

If I had started my post with "In addition to...", instead of "On top of...", then in your mind, would that have changed the meaninig of what I posted?
I ask this, because to me, it seems you misinterpreted my post.


Elvis

 

[drgondog]

Hey, guys, it's what I've heard.
Please, don't shoot the messenger.
If that's incorrect, fine. I was only trying to help shine some light on the initial question.
---------------------------------------------------------------

Not shooting the messenger, just bringing facts to the table.




Elvis

we all hear and repeat 'stuff' myself included. Didn't intend to thump your nose

 

[davparlr]

Hey, guys, it's what I've heard.
Please, don't shoot the messenger.
If that's incorrect, fine. I was only trying to help shine some light on the initial question.
---------------------------------------------------------------

Daveprlr,

If I had started my post with "In addition to...", instead of "On top of...", then in your mind, would that have changed the meaninig of what I posted?
I ask this, because to me, it seems you misinterpreted my post.


Elvis

I am not sure of what you mean by this comment. In you initial comment, you seem to imply that the aerodynamics and engine of the P-47 allowed very good cruise, which I would agree, however it could mislead someone to assume this cruise perfomance was equavlent to the P-51, which it was not. The P-51 cruise performance was not only very good but excellent. The extended range of the later P-47s were due to the massive amount of fuel carried.

 

[davparlr]

Very true. Period. I believe the 51 had it way over both of those ships up to critical altitude respectively, both for reasons of drag and also the fuel consumption for each ship in optimal range cruise speed.

IIRC the optimal cruise (range vs loiter) for the 51D (and B-10 and -15) with the 1650-7 was around 16-17K at 27" and 2000 rpm. As you well know the optimum is influenced by payload but that fuel consumption was around 48gpm. I'm goind to have to dig but I believe the fuel consumption for cruise speed for optimal range for both the F4U and P-47 were about 35-40% higher.

In an earlier post where I was comparing escort performance of American aircraft, and using AF pilot performance charts, I had calculated that the fuel used at cruise for the P-47D-22 was about 260 gallons for 600 miles. For the P-51, the fuel used was 108 gallons for 600 miles. This seems much higher than the 35-40% higher. If I have time, I will go back and reevaluate my calculations to see if i committed some error.