P-47: Range, Deceit and Treachery

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I would have assumed most people here see Greg's videos the day they come out and that one came out two weeks ago. Are Greg's videos not appreciated here? This is a sincere rather than rhetorical question. I thought he was a long time commentor as well, but was never sure it was the same guy.
 
I would have assumed most people here see Greg's videos the day they come out and that one came out two weeks ago. Are Greg's videos not appreciated here? This is a sincere rather than rhetorical question. I thought he was a long time commentor as well, but was never sure it was the same guy.

If it's the two Greg's I think you are referring to, no, they aren't the same person.
 
Good analysis! A few extra points:

1. In the P-51 the pilot had to first burn off fuel from the main tanks (about 30 gal) to allow the excess fuel return to go into the tanks and not be vented overboard. Once that was taken care of the P-51 with the aft fuselage tanks had to burn off fuel for that tank (about 30 gal) to prevent the CG from getting to far aft. Only THEN could the pilot start using the drop tanks. That means that when you punched off your drop tanks you did not have full internal fuel available, but were down probably 50 - 60 gallons or so.
2. I read of a case where P-51's were flying over Yugoslavia they did frequent abrupt course changes to evade flak traps. They were using drop tanks and a rookie pilot on his first mission noted that when they would make those turns the fuel would slosh and the engine would sputter as a result. He did not like that, so he punched his tanks off, but the other three guys kept theirs, the engine sputtering not being of concern to the old hands. The rookie barely made it back to base since he did not use all the fuel in his tanks.
3. The paper 108 gallon fuel tanks were sent to Wright Field for evaluation and a year later they replied that they were not usable, presumably because after 24 hours they were soggy and had to be defueled and discarded. By that time the 8th AF had found out that they worked and ignored the evaluation.
 
From Warren Bodies' monumental work on the Thunderbolt:

P-47DropTanks-1.jpg
 
Good analysis! A few extra points:

1. In the P-51 the pilot had to first burn off fuel from the main tanks (about 30 gal) to allow the excess fuel return to go into the tanks and not be vented overboard. Once that was taken care of the P-51 with the aft fuselage tanks had to burn off fuel for that tank (about 30 gal) to prevent the CG from getting to far aft. Only THEN could the pilot start using the drop tanks. That means that when you punched off your drop tanks you did not have full internal fuel available, but were down probably 50 - 60 gallons or so.
2. I read of a case where P-51's were flying over Yugoslavia they did frequent abrupt course changes to evade flak traps. They were using drop tanks and a rookie pilot on his first mission noted that when they would make those turns the fuel would slosh and the engine would sputter as a result. He did not like that, so he punched his tanks off, but the other three guys kept theirs, the engine sputtering not being of concern to the old hands. The rookie barely made it back to base since he did not use all the fuel in his tanks.
3. The paper 108 gallon fuel tanks were sent to Wright Field for evaluation and a year later they replied that they were not usable, presumably because after 24 hours they were soggy and had to be defueled and discarded. By that time the 8th AF had found out that they worked and ignored the evaluation.

IIRC, one of the 'virtues' of the paper tanks was that they were of no use to the Axis when dropped, as they could not be reused/recycled, unlike the aluminium tanks.
 
Well, the paper tanks were not completely without value. A friend of mine, a Polish POW, said that pilots would fly over their camp and jettison their drop tanks. There usually was a small amount of gasoline left and they were able to fill their cigarette lighters. He did say that the tanks were made out of paper.

By the way, does anyone know if the RAF used the paper drop tanks? I guess their Mustang III and IV used them.
 
1. In the P-51 the pilot had to first burn off fuel from the main tanks (about 30 gal) to allow the excess fuel return to go into the tanks and not be vented overboard. Once that was taken care of the P-51 with the aft fuselage tanks had to burn off fuel for that tank (about 30 gal) to prevent the CG from getting to far aft. Only THEN could the pilot start using the drop tanks. That means that when you punched off your drop tanks you did not have full internal fuel available, but were down probably 50 - 60 gallons or so.
From what I remember, they would run on the center tank so as to move the center of gravity forward -- it was basically right up on the aft limit when filled to 85 gallons. Generally, you would drain the fuel down to 30-gallons (removing 55 gallons) as this gave the aircraft good responsiveness.

The P-51/P-51A's used the Allison V-1710, which was lighter than the V-1650 fitted to the P-51B's. The heavier engine, though more powerful (particularly at altitude), it made the aircraft more nose-heavy (I figure the 4-bladed prop didn't help) and, while it didn't appear to be in danger of tipping onto it's nose: It was heavier on the controls. They fixed this by putting a ballast in front of the rudder, if I recall (IIRC, it was about 85 pounds).

In order to increase range for the long-ranged bomber-escort mission, they had managed to reposition some radio equipment, and freed up about 85-gallons of gas. It shifted the center of gravity dangerously far aft, and the ballast was removed. While this might very well have made the difference between an aircraft that was flyable and one that wasn't, it also meant when that 85 gallon tank went down to 0, the aircraft was actually nose heavy. If 30-gallons remained, you'd have about the right balance.
2. I read of a case where P-51's were flying over Yugoslavia they did frequent abrupt course changes to evade flak traps. They were using drop tanks and a rookie pilot on his first mission noted that when they would make those turns the fuel would slosh and the engine would sputter as a result. He did not like that, so he punched his tanks off, but the other three guys kept theirs, the engine sputtering not being of concern to the old hands. The rookie barely made it back to base since he did not use all the fuel in his tanks.
That was something I didn't know -- I do like learning things like this as it's a kind of practical knowledge that real pilots had to know.
3. The paper 108 gallon fuel tanks were sent to Wright Field for evaluation and a year later they replied that they were not usable, presumably because after 24 hours they were soggy and had to be defueled and discarded. By that time the 8th AF had found out that they worked and ignored the evaluation.
Smart move!
 
Hey MIflyer,

The 108 USgal paper drop tanks that are being referred to in this thread are the same as the 90 Impgal paper drop tanks developed by the British, just with different markings and, in some cases, different attachment set-ups. The 90 and 45 Impgal paper drop tanks were originally developed for the Hurricane, I think. I do not know if any paper drop tanks were manufactured in the US, maybe someone else does?

There are 1.2 USgal per 1 Impgal, so 90 Impgal x 1.2 = 108 USgal

The 108 USgal paper drop tanks are sometimes confused with the 110 USgal metal drop tanks, which were US developed/manufactured. I have also seen the 108 USgal paper drop tank mistakenly called a 110 USgal paper drop tank.

There is a brief but nice story about the paper drop tanks at the following website: "The war-winning paper fuel tank"
 
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From what I remember, they would run on the center tank so as to move the center of gravity forward -- it was basically right up on the aft limit when filled to 85 gallons. Generally, you would drain the fuel down to 30-gallons (removing 55 gallons) as this gave the aircraft good responsiveness.

The P-51/P-51A's used the Allison V-1710, which was lighter than the V-1650 fitted to the P-51B's. The heavier engine, though more powerful (particularly at altitude), it made the aircraft more nose-heavy (I figure the 4-bladed prop didn't help) and, while it didn't appear to be in danger of tipping onto it's nose: It was heavier on the controls. They fixed this by putting a ballast in front of the rudder, if I recall (IIRC, it was about 85 pounds).

In order to increase range for the long-ranged bomber-escort mission, they had managed to reposition some radio equipment, and freed up about 85-gallons of gas. It shifted the center of gravity dangerously far aft, and the ballast was removed. While this might very well have made the difference between an aircraft that was flyable and one that wasn't, it also meant when that 85 gallon tank went down to 0, the aircraft was actually nose heavy. If 30-gallons remained, you'd have about the right balance.
That was something I didn't know -- I do like learning things like this as it's a kind of practical knowledge that real pilots had to know.
Smart move!
There was a lot to it. The first conversions where Merlins were put in a Mustang/ P-51A airframe maybe were just that with some rough calculations for weight but the actual production models had a different scoop, different radiators including for the intercooler, they may have had a bigger oil tank too, Merlins burn oil as well as petrol. Later versions had a tail mounted basic radar warning set up. Someone posted here years ago that at the start of the war, Supermarine had one man doing weight and COG calculations, by the end of the war it was a complete department, I presume N/A were similar, as with everything it gets complicated.
 
A lot of the linked articles are referring to Lt. Col. Hough's report on the trials at Bovingdon on 7th July 1943. This was a 200 gallon, unpressurised, pressed paper, belly tank.

This is the original, which also answers some of the questions about where the equipment was manufactured.

Hough 1_small.jpg




Hough-2_small.jpg


Further tests were carried out on 13 July.

The 84 gallon metal 'teardrop' belly tank was first tested on 17 August.

The 108 gallon metal belly tank was not tested until 2 September 1943.
 
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I believe that the 200 gallon tank described in the video was intended only as a ferry tank and thus was only manufactured in small numbers. The only picture I can recall of it showed it with a large wedge shaped wooden block on the front, which I guess was for aerodynamics.

If you look around this site you will see a WWII article I posted on how Lockheed made the 165 gallon drop tanks, stamping them out of steel sheet, so it it not require that many workers to produce them.

https://ww2aircraft.net/forum/attachments/steeeldroptanks-2-jpg.470842/
 
I believe that the 200 gallon tank described in the video was intended only as a ferry tank and thus was only manufactured in small numbers.
Did it have pressurization of any kind?
 

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