I've seen just one photo of it, and Good knows that I'm a ww2 tech nerd for the last 40 years
IMO - it was a very, very rare occurrence to have P-47s flying in combat with these.
Greg of Auto and Airplanes has asked for a Debate
- Thread starter ObtuseOcelot
- Start date
IMO - it was a very, very rare occurrence to have P-47s flying in combat with these.
drgondog
Major
Agreed - Republic Delivered ONLY the 200 gal bullfrog (Gabreski).
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- Sep 11, 2014
Greg needs to come forward with his other 3 supposed documents on this tank.
Here is what I suspect:
These documents refer to the ferry tank and he has just read into them the existence of this unicorn tank. In the debate he stated that he "thinks" the image I posted above is the 200 gallon. So this implies there are no pictures in his other documents, which suggests to me he has no means of correlation between them because the Jan43 manual with the image he thinks is the unicorn tank contains no named nomenclature. So without either a pair of images or a name for this tank, how has he even confirmed that whatever documents he has are even about the same thing....or are just not about the 200 gallon tank everyone already knows about.
I think that's more likely than Greg discovering from nowhere a mystical drop tank nobody in the historical record has ever before mentioned.
Additionally: if there is some separate 200 gallon tank out there....how did nobody at the time try to use it? P-47s obviously used other drop tanks in 1943 and everyone was scrambling to make improvised tanks as well. Are we meant to believe that all this was going on and somehow everyone missed that there was a perfectly good drop tank made by Republic that could have been ordered into production? Surely Republic would have been screaming about it.
And Greg can't say that it's because the mafia blocked drop tanks because other drop tanks were already in use at the time.
IMO Greg was being disingenuous when he suggested the tanks didn't need to be pressurised above 20000 ft, since he said thousands of commercial aviation airliners were flying around with unpressured tanks at much higher altitude to this day.
Look at most Boeing, 707 and up, at almost any other civilian airliner, their engines hang below the wings, and they're usually low wing aircraft too, their engines are probably 6-10 ft. below their fuel tanks, since the beginning of time liquid flows easily downhill .
While in the P-47, the wing tanks are the lowest part of the fuel system, so who should be surprised that it needed a little boost of positive pressure in the tank at high altitude to assist the fuel pump to get the fuel to the engine. And it's just possible maybe aviation fuel pumps have improved in the last 80 years since the events in question.
Then acting as if the operating conditions were the same in the Pacific operations and Europe.
In European operations all allied aircraft had to be at high altitude before they crossed the French coast, and the fighters had to be availible to escort them from that point on.
The fighters best economy cruise speed and altitude usually didn't match what the bombers could do at altitude, nor was any mission a straight path to the target.
Just so many facets of the missions were completely ignored. Greg and his fans seem to think the bombers flew straight from their base to the target, and the same escorts went with them the whole way.
They seem to know nothing about several relays of fighter groups escorting the bombers in relays.
That the bombers had to fly indirect paths to their targets both to avoid known flak hot spots and to attempt to fool the Germans as to exactly what their target was as long as they could so the Luftwaffe couldn't concentrate their fighters where they could be most effective.
And the mission profile in the Pacific was usually different, so the ranges flew by even the same aircraft in the different theaters was often apples to oranges.
Just so much that wasn't said.
Look at most Boeing, 707 and up, at almost any other civilian airliner, their engines hang below the wings, and they're usually low wing aircraft too, their engines are probably 6-10 ft. below their fuel tanks, since the beginning of time liquid flows easily downhill .
While in the P-47, the wing tanks are the lowest part of the fuel system, so who should be surprised that it needed a little boost of positive pressure in the tank at high altitude to assist the fuel pump to get the fuel to the engine. And it's just possible maybe aviation fuel pumps have improved in the last 80 years since the events in question.
Then acting as if the operating conditions were the same in the Pacific operations and Europe.
In European operations all allied aircraft had to be at high altitude before they crossed the French coast, and the fighters had to be availible to escort them from that point on.
The fighters best economy cruise speed and altitude usually didn't match what the bombers could do at altitude, nor was any mission a straight path to the target.
Just so many facets of the missions were completely ignored. Greg and his fans seem to think the bombers flew straight from their base to the target, and the same escorts went with them the whole way.
They seem to know nothing about several relays of fighter groups escorting the bombers in relays.
That the bombers had to fly indirect paths to their targets both to avoid known flak hot spots and to attempt to fool the Germans as to exactly what their target was as long as they could so the Luftwaffe couldn't concentrate their fighters where they could be most effective.
And the mission profile in the Pacific was usually different, so the ranges flew by even the same aircraft in the different theaters was often apples to oranges.
Just so much that wasn't said.
Complete rubbish about tank pressurisation it seems. For a start jet airliners have tank venting to prevent air pressure over or under pressure which can cause structural damage in flight.
Jet airliners have multi KW electric immersed fuel pumps that generate 50psi at very high flow.
So why is pressurised tanks mentioned? It is purely because the easiest way to move fuel from an underslung external tank is to air pressurise the tank and let air pressure push the fuel up into a normal aircraft tank. This saves all the problems with pumps in external tanks. Vapour pressure is a problem with fuel and at high altitude, it is more so, and an air pressurised external tank will work best.
Eng
Jet airliners have multi KW electric immersed fuel pumps that generate 50psi at very high flow.
So why is pressurised tanks mentioned? It is purely because the easiest way to move fuel from an underslung external tank is to air pressurise the tank and let air pressure push the fuel up into a normal aircraft tank. This saves all the problems with pumps in external tanks. Vapour pressure is a problem with fuel and at high altitude, it is more so, and an air pressurised external tank will work best.
Eng
Any discussion of pressures, bleeds from instruments, paper tanks, glass fibre tanks, shackles, mountings, approvals and designs, secret projects and ideas is a welcome and well used distraction from the plain and obvious fact that a 1943 P-47 couldnt engage in combat over Schweinfurt for 15 minutes and then make it back to the UK. The other "thang" that must never be discussed is if the "bomber mafia" werent committed to unescorted bombers being self defending what would they be committed to, as a doctrine? The P-38 was like rocking horse manure in 1942, the P47 was just being sent to UK (operational in Spring 1943)and the P-51 was in the process of fitting a Merlin. The P-51 may have turned out to be the best escort fighter of the war, because of what happened, no one in the USA in the mid 1930s could have strategy based on producing it.
I think there are 2 pivot points that Greg uses in his case
Pivot btw the 2 points when one becomes untenable.
- The bomber generals pre war believed that B-17s wouldn't need fighter escort and made sure there were no drop tanks on fighters
- During 1943 the bomber generals refused to provide fighter escort even though options were available with tank equipped P-47s or P-38s
Pivot btw the 2 points when one becomes untenable.
MiTasol
Major
The jet aircraft fuel pump configuration is why they do not need pressurised tanks and there are a number of other factors involved.
In a nutshell - WW2 fighters suffered from vapour lock, especially from drop tanks, because they used suction pumps. Modern jet aircraft can not suffer from vapour lock because they use pressure pumps.
In all post 1950 jet aircraft the fuel pump is mounted either inside the fuel tank at the lowest point of the fuel tank or below the lowest point of the fuel tank. This means that the pump is never sucking fuel in. The in flow is supplied by the fuel itself and gravity. Even if the pump was to suck air for a second the moment as the wing drops low the moment the wing becomes level again the fuel flow recommences.
On most ww2 aircraft, especially fighters, the fuel pump was a suction pump fitted between the tanks and the engine and I cannot think of any ww2 fighter that did not share a single pump between all tanks. This pump was usually fitted above the lowest point in every tank and was "far" above the lowest point of any drop tank and the lowest point in the tank is where the fuel is drawn from. Once primed it works perfectly until it loses suction for any reason and then it would not again lift any fuel unless there is an initial flow supplied to the pump by gravity to re-prime it.
The second major factor that Greg totally ignores is that a perfect suction pump can only lift fluid the equivalent of one atmosphere of the fluid - in the case of water about 32ft or 9.75metres at standard sea level pressure of 1013hpa. In simple terms this is because the pump creates a suction and the atmospheric pressure forces the fluid to flow towards the suction.
Because avgas has a lower specific gravity than water (0.72) the pump can lift fuel further - about 44 feet/13m.
As an aircraft climbs the atmospheric pressure drops and the ability of the pump to lift liquid drops by the same amount. At 20C ground temperature the temperature at 20,000ft is -20C and the air pressure drops to just 445 hpa. At that altitude a perfect water pump will lift water 14 feet or avgas 19 feet so a perfect pump is now less than 1/2 as efficient as at sea level.
The temperature at 30,000ft is -40C and the air pressure drops to just 265 hpa. At that altitude a perfect water pump will lift water 8.3 feet or avgas 11.5 feet. A perfect pump is now less than 1/3 as efficient as at sea level.
The temperature at 40,000ft is -55C and the air pressure drops to just 150 hpa. At that altitude a perfect water pump will lift water 4.7 feet or avgas 6.4 feet. A perfect pump is now only 1/7 as efficient as at sea level
The third major factor, and the most important, that Greg ignores is that fuel contains many different compounds and those various compounds gasify (boil) at different air pressures and temperatures. This is produces what is called vapour lock and is discussed at Vapor lock - Wikipedia. There are only two ways to prevent vapour lock. Change the fuel specification to something far closer to diesel or kerosene, which will destroy the engine, or pressurise the fuel tank.
WW2 fighters suffered from vapour lock because they used suction pumps. Modern jet aircraft can not suffer from vapour lock because they use pressure pumps.
In a nutshell - WW2 fighters suffered from vapour lock, especially from drop tanks, because they used suction pumps. Modern jet aircraft can not suffer from vapour lock because they use pressure pumps.
In all post 1950 jet aircraft the fuel pump is mounted either inside the fuel tank at the lowest point of the fuel tank or below the lowest point of the fuel tank. This means that the pump is never sucking fuel in. The in flow is supplied by the fuel itself and gravity. Even if the pump was to suck air for a second the moment as the wing drops low the moment the wing becomes level again the fuel flow recommences.
On most ww2 aircraft, especially fighters, the fuel pump was a suction pump fitted between the tanks and the engine and I cannot think of any ww2 fighter that did not share a single pump between all tanks. This pump was usually fitted above the lowest point in every tank and was "far" above the lowest point of any drop tank and the lowest point in the tank is where the fuel is drawn from. Once primed it works perfectly until it loses suction for any reason and then it would not again lift any fuel unless there is an initial flow supplied to the pump by gravity to re-prime it.
The second major factor that Greg totally ignores is that a perfect suction pump can only lift fluid the equivalent of one atmosphere of the fluid - in the case of water about 32ft or 9.75metres at standard sea level pressure of 1013hpa. In simple terms this is because the pump creates a suction and the atmospheric pressure forces the fluid to flow towards the suction.
Because avgas has a lower specific gravity than water (0.72) the pump can lift fuel further - about 44 feet/13m.
As an aircraft climbs the atmospheric pressure drops and the ability of the pump to lift liquid drops by the same amount. At 20C ground temperature the temperature at 20,000ft is -20C and the air pressure drops to just 445 hpa. At that altitude a perfect water pump will lift water 14 feet or avgas 19 feet so a perfect pump is now less than 1/2 as efficient as at sea level.
The temperature at 30,000ft is -40C and the air pressure drops to just 265 hpa. At that altitude a perfect water pump will lift water 8.3 feet or avgas 11.5 feet. A perfect pump is now less than 1/3 as efficient as at sea level.
The temperature at 40,000ft is -55C and the air pressure drops to just 150 hpa. At that altitude a perfect water pump will lift water 4.7 feet or avgas 6.4 feet. A perfect pump is now only 1/7 as efficient as at sea level
The third major factor, and the most important, that Greg ignores is that fuel contains many different compounds and those various compounds gasify (boil) at different air pressures and temperatures. This is produces what is called vapour lock and is discussed at Vapor lock - Wikipedia. There are only two ways to prevent vapour lock. Change the fuel specification to something far closer to diesel or kerosene, which will destroy the engine, or pressurise the fuel tank.
WW2 fighters suffered from vapour lock because they used suction pumps. Modern jet aircraft can not suffer from vapour lock because they use pressure pumps.
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MiTasol
Major
WW2 aircraft and drop tanks were also vented so your first point is not relevant.
The rest is correct. Multiple aircraft used pressurised drop tanks for the reason you stated and some aircraft used the pressurised drop tanks to top up the main fuel tank which eliminates the requirement for the pilot to select the drop tank and then go back to the main tank.
That's why I said Greg was being dishonest about this, he's a airline capt. with thousands of hours in the very aircraft he describes as having unpressurised fuel tanks and that has nothing to do with the situation of the WW2 drop tanks.
He knows, and he doesn't care, he just doesn't want to admit a lot of what he spouts is BS, and can't be proved .
He got many fanboys, they subscribe to his sites, that's who he's playing to.
He knows, and he doesn't care, he just doesn't want to admit a lot of what he spouts is BS, and can't be proved .
He got many fanboys, they subscribe to his sites, that's who he's playing to.
Thumpalumpacus
Colonel
My comment on his Youtube thread, after finding the time to watch it:
I think both had points made well, but I also think that Greg spent a lot of time appealing to the "Bomber Mafia" when that was actually the point he was trying to make, whereas Bill made many good technical points that are probably lost on Greg's readership.
drgondog, you did well. It's a shame it's probably a case of pearls before swine. You can lead a horse to water, but you can't make him think.
I think both had points made well, but I also think that Greg spent a lot of time appealing to the "Bomber Mafia" when that was actually the point he was trying to make, whereas Bill made many good technical points that are probably lost on Greg's readership.
drgondog, you did well. It's a shame it's probably a case of pearls before swine. You can lead a horse to water, but you can't make him think.
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
I gave you the bacon 'cause I can understand your post. It deserved more than an informative.
I had a conversation with someone about "why don't I like Greg A&A". I pointed out that I never once said that. I did tell him, after reading comments posted here, an aviation ignoramus like me wouldn't know if he was wrong or right on a topic. That is why I stopped watching his videos. This came up after a couple of G A&A episodes on the P-47 were released.
BTW I think G A&A's video on the Wright Brothers is great.
Thumpalumpacus
Colonel
I don't like his "greetings" intro. It's only slightly less-pretentious than "salutations". I bet he doesn't talk to his passengers like that. What the hell is wrong with a "hey guys" or "hiyas"?
C'mon, man. What is this, Buckingham Palace?
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
I personally prefer Professor Propwash's "DUDE!" greeting, myself.
Thumpalumpacus
Colonel
"Dude" is something I'd throw down with anyone, President or peasant. [/Spicoli]
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
Learn it. Know it. Live it.
I think he flies cargo, not passengers. I like his videos. They helped to explain the function of turbochargers and superchargers. I'm just not a fan of the conspiracy theory take.
MiTasol
Major
He should really say Greetings and hallucinations. That would be more accurate
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
Greasings and salivations?
Thumpalumpacus
Colonel
I'm not a fan of how he talks to his viewers. I do watch his vids and try to glom some stuff.
