Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: caldera on April 15, 2012, 01:05:00 PM
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IIRC, the old P-40s had two fuel tanks: main and fuselage. Now they have fuselage, forward and aft tanks. Any benefit to manual fuel tank select and what order is best?
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Well on the 190's, you want to burn the aft tanks. Aside from that I haven't a clue as to what the best order for fuel burn on the P-40 is.
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All in all... just let the computer do it for you.
The only exception is the F4U models with the wing tanks: burn the left wing tank first, it helps the wing from dipping too early (stall out). Not only is that true in AH, it is true in the real deal as well. Start video at 12:20 min :aok
http://www.youtube.com/watch?v=kpxyyLQ7u7g
Other than that, if people *really* think that draining certain fuel tanks before other will improve their chances of survival or their ability to perform -that- much better... then let them keep their sanity. They are probably the same kool-aid drinkers that fire off all the .30 cal MG ammo from the Mossi and the 8mm MG rear gunner ammo "to get rid of extra weight so it can turn better". I'll be happy to test out any theories with the diehards.
The P47 may benefit from burning 1 tank before the other because it is the most likely first point of damage. That is a damage issue not a performance issue though.
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Good idea to burn off the aux tank in the 51s first.
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Good idea to burn off the aux tank in the 51s first.
Oh yeah agree there
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All in all... just let the computer do it for you.
The only exception is the F4U models with the wing tanks: burn the left wing tank first, it helps the wing from dipping too early (stall out). Not only is that true in AH, it is true in the real deal as well. Start video at 12:20 min :aok
http://www.youtube.com/watch?v=kpxyyLQ7u7g
Other than that, if people *really* think that draining certain fuel tanks before other will improve their chances of survival or their ability to perform -that- much better... then let them keep their sanity. They are probably the same kool-aid drinkers that fire off all the .30 cal MG ammo from the Mossi and the 8mm MG rear gunner ammo "to get rid of extra weight so it can turn better". I'll be happy to test out any theories with the diehards.
The P47 may benefit from burning 1 tank before the other because it is the most likely first point of damage. That is a damage issue not a performance issue though.
I know on the N you want to burn out both wings if you're loaded, either that or burn one and turn only one way really good.
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In the real world they had to use the fuselage tank first (at least to a certain mark) as there was a fuel return line from the carburetor back to this tank.
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Oh yeah agree there
oh? What for?
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Well on the 190's, you want to burn the aft tanks. Aside from that I haven't a clue as to what the best order for fuel burn on the P-40 is.
I forgot we were talking about 190's...
Check this link out:
http://www.sim-outhouse.com/sohforums/showthread.php?53807-For-Kelti-P-40-fuel-tanks
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oh? What for?
IIRC the weight in the Aux tank in the 51 alters the planes center of gravity making it a little harder to control, and more prone to loss of control. Burning the aux tank dry fixes the problem.
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IIRC the weight in the Aux tank in the 51 alters the planes center of gravity making it a little harder to control, and more prone to loss of control. Burning the aux tank dry fixes the problem.
"Loss of control"? As in dipping the left wing? :headscratch:
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I forgot we were talking about 190's...
Check this link out:
http://www.sim-outhouse.com/sohforums/showthread.php?53807-For-Kelti-P-40-fuel-tanks
Either you're trolling, or you're even dumber than I gave you credit for. The sad part is that its only about even money chances of it being a troll.
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Couldn't we calculate the moment arm of the aircraft if we knew the exact location of each tank and each ones size?
With that information we could figure out how emptying one tank before the other would affect center of gravity.
Unfortunately I have no idea how to do any of that, but someone might?
As for my guess I think dumping the aft first then the center and finally the forward. For the flying in AH I am thinking that we want the center of gravity as far forward as possible, keeping the tail end as light as possible. My rationale is that in AH we would have a P40 that responds better to quick elevator movements and in a stallfight the tail seems to sit real low in a turn. That has to add additional drag due to the P40 sorta "crabbing" around the turn.
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I found this online, no real reference unfortunately but it's interesting regardless.
According the the WWII Training Manual for the P-40 (written primarily for the later models) :
"The fuselage tank is called the vented tank, which means there is an overflow line between this tank and the carburetor. The fuel line carries excess gas from the carburetor back to the fuselage tank. At high engine rpm, the fuel overflow may run as high as 10 or 15 gallons per hour.
Always use the fuselage tank for takeoff. During takeoff the chance of fuel overflow is especially high, and unless you are using the fuselage tank--the only one built to handle overflow gas--the overflow is lost.
After takeoff, always use at least 15 gallons from the fuselage tank before switching to another fuel tank.
The fuselage tank accumulates possible overflows from the other tanks during flight. Always turn the selector handle to the fuselage tank if it appears you have run out of gas. The fuselage tank probably contains a few gallons of overflow fuel."
The training manual later suggests: "Climb at a speed of 150-160 mph. When you reach 1000 feet, switch from the fuselage tank to the belly tank and fly on the belly tank until it is empty." I believe one of the considerations for doing this is that the belly tank does not have a fuel gage, so it is best to use this fuel first and have a known quantity in the other tanks.
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And also this, anecdotal but it's something to start with.
I'm looking at a reprint of the P-40D/E flight instructions from circa 1943. What's interesting is that in this POI, the startup instructions say to prime and start the engine on the reserve tank and to keep the selector valve on "Res." during preflight check and takeoff. Here is the sequence it gives for the tanks following takeoff:
c. Order of Fuel Tank Use.
Belly tank (if installed).
Fuselage tank.
Main tank.
Reserve tank.
d. Belly Tank.
(1) If the airplane is equipped with a belly tank, the fuel selector valve should be set at "BELLY" as soon at practicable after take-off.
(2) If the belly tank is dropped during flight, a slight heaviness will be observed.
I've been searching around casually for the last hour and it seems that mostly everything I've found concerns burning fuel tanks in a specific order to prevent problems with the fuel system and not for performance gains. This might make figuring out in AH (where those problems do not exist) what tank to burn first harder.
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More Reading, this is from a BBS in A2A Sims as were the others (gosh why dont they fly here?) :headscratch:
Hi Ty,
Yes, it is a small world. I guess you probably know then about the ferrying operations from Great Falls during the war (hence my avatar of the 7th Ferrying Group's patch) and how military planes were being flown through this area from factories to bases and from bases to depots. Many of the planes headed for Alaska went through Great Falls, most notably several thousand Airacobras, King Cobras and other Lend-Lease planes for the Russians. We also had a B-17 training mission here, which is why the Air Force base was originally built in 1943.
I don't have the P-40 w/AccuSim package and I'm not at all an expert on the P-40 so I don't know how well I can address your specific question.
The vented tank collects unused fuel vapor that would otherwise be lost. If the vented tank is full, the recycled fuel running into it overflows and I think it is released out of the fuselage and into the airstream. Quite simply, the mechanism for salvaging unused fuel fails and the 'recollected' fuel is wasted. It is better to burn off some of that fuel in the vented tank at the beginning of your flight so that you create space for the salvaged fuel to go to throughout the rest of the flight. (On a similar note, I recall that P-47 pilots were supposed to switch back to the vented tank every hour--for ten minutes I think--to maintain that empty space.)
I'll argue that in the late 1930s the Army really didn't anticipate needing a fighter that would fly more than 100 miles to engage in combat--after all, the U.S. was concerned primarily about defending the continent against the incursion of a naval superpower and with defending our Pacific stations and territories. Japan's navy was eyed as our major threat. The Army wanted fighters that could scramble to engage enemy bombers approaching our factories, ports, coastal defenses, etc. I'll assume that this is why the P-40Bs did not have provisions for an auxiliary belly tank (or at least not drop tanks). Although the Army originally anticipated that operational units would only need a limited combat range, I suppose experience proved it was necessary to fly military pursuit aircraft long distances even if only to relocate them to new bases. Hence, plumbing for a belly tank was added with the 'C' model.
Let's assume that in 1941 (pre-war) if a P-40C pilot knew he was going to fly a long distance that would require an auxiliary tank, he'd already have his route planned and he'd know how much fuel he'd need to get there since total weight is a major consideration. I'm thinking that having a belly tank installed wouldn't be the normal configuration for a squadron on alert because the external tank automatically reduces the airplane's top speed of by 10 mph, and probably wreaks havoc on the airplane's flight stability as well. If I am correct, the belly tank was used primarily for ferrying operations and recon patrols, not for the direct interdiction role. Let's also assume the pilot isn't going to drop his tanks on some poor farmer's barn halfway between Base X and Base Y, if you know what I mean.
The pilot starts up and takes off with his Reserve Wing tank and burns approximately 15 gallons to give him space for unused fuel that will be recollected from the carburetor. He then switches to the Belly (Auxiliary) tank since he is carrying that extra fuel for a reason--he knows he needs that gas to get to his destination. He'll want to empty the Belly tank in case he has to make a belly landing; also, since it is not a gaged tank he'd probably want to use up the fuel and then switch to tank that gives him a needle to watch. The Fuselage tank is recommended next, probably because it is a large tank and is located behind the pilot and therefore affects the airplane's center of balance. When the Fuselage tank gets empty, the pilot can switch to the other gaged tank--the Main Wing tank which is located approximately under his seat. Finally, when the fuel in the Main Wing tank is consumed, he switches to the Reserve Wing tank, which is located fore of the Main Wing tank and approximately under his feet. By now the pilot should be very close to his destination and shouldn't be sweating the exact contents of the Reserve Wing tank. If the fuel selector that is illustrated in the vintage P-40D/E manual is the same as it was in the P-40C, the pilot will never have to move the selector position through an empty tank if he uses this sequence.
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Just a note - fuselage and reserve tank is both the same.
Some P-40 manuals instruct pilots to drain the fuselage tank to 35 gallons (acts as reserve) for better stability, then switch to belly tank.
The normal flow-back from the carburetor is given a 2-10 gallons per hour.