REPUBLIC AVIATION PERFORMANCE DATA - P-47 "M" and

[DaveB.inVa]

Most of the big bombers that I know of had autopilots from the beginning. Remeber that the Norden (and Sperry I believe) bombsights were interfaced with the autopilot and cranking in the right stuff into the bombsights would in turn fly the plane through the autopilot. Most times the lead aircraft flew on autopilot..... it was everybody behind that had to worry bout jockying the throttles and working very very hard to maintain tight formation.

Also coming with the B-17G the autopilot was equipped with a "Formation Stick". This stick actually was connected to the autopilot and in formation flight the pilot could input slight controls in through the stick and effectively fly the aircraft.

The B-29 was equipped with an autopilot but did not have the formation stick. It had some buttons on the autopilot that could perform the same function. Ive read a couple storys about B-29's with controls shot out being able to fly all the way back to Iwo Jima or the Marianias using the buttons on the autopilot.


I'm also fairly certain the P-47N had foldable rudder pedals that would allow the pilot more legroom during a long cruise on autopilot... don't quote me on that before checking it out though.

Also the relief tube just emptied into the air! I remember reading about one P-47N pilot on Ie Shima who had a little trouble with his tube. His crewchief decided to have a bit of fun with him and plugged the tube where it exited the aircraft. Just so happened the pilot got into combat on this mission and during some hard maneuvering ended up getting a little wet!!

[Lunatic]

Originally Posted by Soren

So the 16,300lbs normal loaded figure for the -47N was correct afterall....I thought so

Which is what we were looking for. (or atleast me)

For example the Spit XIV's Combat gross weight was 8500lbs, and the Bf-109K-4's was 6,940lbs. Both are with full internal fuel load and ammunition.

So to keep it fair, we should be looking at the -47N's combat gross weight aswell.

ROFL - "to keep it fair"

How is it fair to compare the performance when fully loaded when the P-47 has so much greater range?

To "keep it fair", all three aircraft should be loaded with sufficient fuel to give them equal ranges don't you think?

Originally Posted by Soren

I set up the Bf-109K-4 as an example, because these two would meet in battle under these exact conditions; The 109 would be weighing its normal combat gross weight of 6,940lbs while the -47N weighing its normal combat gross weight of 16,300lbs. Thats how it would be, now you can call that unfair all you'd like, but thats how war is.

How do you figure? The P-47 would have flow from a distant base, the 109K would have scrambled for intercept. The P-47 would likely have much less than its maximum fuel onboard at the point of combat.


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Lunatic

[Lunatic]

Originally Posted by Soren

DAVID all else being equal, fighters did not fly out on half full or even 3/4 full internal fuel tanks, that's just not the way it was done. And they certainly didn't fly on half full internal fuel tanks coupled with drop tanks..

So while the -47N might have had an excessive amount internal fuel for 'one' mission, it would still be fully fueled up in case of any emergency.

Not necissarily. The fuselage fuel would be filled to capacity, but the wing tanks might or might not be. The P-47N had fuel cells rather than normal tanks in the wings, IIRC it had 6 cells in each wing. It was entirely reasonable and possible to fill all, some, or none of the cells depending on mission parameters.

On the P-38L the fuel tanks outside of the engines were often left empty, so your contention that maximuim internal fuel was always loaded is false.

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Lunatic

[FLYBOYJ]

Originally Posted by Lunatic

Not necissarily. The fuselage fuel would be filled to capacity, but the wing tanks might or might not be. The P-47N had fuel cells rather than normal tanks in the wings, IIRC it had 6 cells in each wing. It was entirely reasonable and possible to fill all, some, or none of the cells depending on mission parameters.

On the P-38L the fuel tanks outside of the engines were often left empty, so your contention that maximuim internal fuel was always loaded is false.

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Lunatic

DISAGREE! You cannot continually leave a fuel tank empty - the cell will deteriorate and rot! Those aircraft with a plain wet wing will have fuel tank sealant within the wing break down as well. Additionally the seals in boost pumps and transfer valves will also rot as well. The only time fuel was left behind was to carry a load or because of density altitude performance, or both. Additionally it was SOP to top off fuel tanks after a mission to prevent condensation in the fuel tank. I've confirmed this with several WW2 wrench turners who served in both ETO and PTO.

[evangilder]

Interesting point, Joe and I will add that with our airplanes at the museum, they always fuel them after a flight before putting them away. I wondered why, but never asked. Condensation makes perfect sense, especially in Camarillo.

[FLYBOYJ]

Originally Posted by evangilder

Interesting point, Joe and I will add that with our airplanes at the museum, they always fuel them after a flight before putting them away. I wondered why, but never asked. Condensation makes perfect sense, especially in Camarillo.

Yep - big time down your way being so close to the beach! I've seen condensation build in the tanks just by being on the ground for 1 hour!

[evangilder]

Wow, I didn't realize it could build that quickly.

[Lunatic]

Originally Posted by FLYBOYJ

DISAGREE! You cannot continually leave a fuel tank empty - the cell will deteriorate and rot! Those aircraft with a plain wet wing will have fuel tank sealant within the wing break down as well. Additionally the seals in boost pumps and transfer valves will also rot as well. The only time fuel was left behind was to carry a load or because of density altitude performance, or both. Additionally it was SOP to top off fuel tanks after a mission to prevent condensation in the fuel tank. I've confirmed this with several WW2 wrench turners who served in both ETO and PTO.

Neither the outer fuel tanks on the P-38L nor the fuel cells in the P-47N wings were self sealing. They were simple fuel tanks. There was nothing to "rot".

Draining condensation in a fuel tank would be easy enough, if that were a problem.

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Lunatic

[FLYBOYJ]

Originally Posted by Lunatic

Neither the outer fuel tanks on the P-38L nor the fuel cells in the P-47N wings were self sealing. They were simple fuel tanks. There was nothing to "rot".

Draining condensation in a fuel tank would be easy enough, if that were a problem.

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Lunatic

Simple fuel tanks (Riveted aluminum) are still sealed with fuel tank sealant at the riveted seams and all the fastener heads are also sealed as well. Welded fuel tanks usually had a a seal or o ring at the outlet or the crossfeed. Once fuel is placed in the tank and contacts that sealant, the sealant must have occasional contact with fuel our else it will break down, and again you still have interconnecting plumbing and boost pumps and/or transfer valves with o rings and seals that will break down as well.

"Normal" fuel tank condensation is removed by draining the fuel at the lowest point of the system and is usually part of the pre-flight. The amout of water in the fuel tank can be see if drained into a clear container, the water will sink to the bottom and can be seen as little droplets at the bottom of the container, which is usually a glass jar. If you do not keep fuel tanks full, large amounts of condensation will build into the tanks, especially in high humity or an enviornment with a lot of percipitation. Normal SOP for all branches of the military, and I know it's been this way for years - if one or two samples of fuel contain water, the whole tank is drained....

[wmaxt]

Leaving a tank empty is also a fire/explosion hazard and if the tank is less than full the remaining fuel degrades quickly. Degraded fuel can/will gum up/destroy any fuel system component as it turns to varnish. Condensation can be drained but not as effectively as preventing it in the first place, aircraft are not stored empty or even below full, minus expansion volume, if possible. Down loading fuel to taylor the aircraft for a mission is common place.

Flying with empty tanks is common with aircraft esp. airliners and cargo planes to save weight for cargo or fuel economy. These aircraft are required to fill empty fuel tanks with inert gas since flight 800 went down. Even these tanks are not empty for extended periods since seals and other flexible parts dry and crack.

wmaxt

[FLYBOYJ]

Originally Posted by wmaxt

Leaving a tank empty is also a fire/explosion hazard and if the tank is less than full the remaining fuel degrades quickly. Degraded fuel can/will gum up/destroy any fuel system component as it turns to varnish. Condensation can be drained but not as effectively as preventing it in the first place, aircraft are not stored empty or even below full, minus expansion volume, if possible. Down loading fuel to taylor the aircraft for a mission is common place.

Flying with empty tanks is common with aircraft esp. airliners and cargo planes to save weight for cargo or fuel economy. These aircraft are required to fill empty fuel tanks with inert gas since flight 800 went down. Even these tanks are not empty for extended periods since seals and other flexible parts dry and crack.

wmaxt

Thanks wmaxt! I didn't even touch on the fire hazard! I've worked in places that REQUIRED aircraft fuel tanks to be topped off before placing them in a hangar, this done to reduce fumes in the system.....

I've worked on B737s where we put nitrogen into the fuel tanks that were deactived due to maintenance requirements - usually a repair or service bulletin would need to be complied with.....

Bottom line, fuel is left behind to save weight, because of an ordanance requirement or a performance requirment (usually at take off). Aside from this, like the old saying goes, the only time you could have too much fuel is when you're on fire!

[Lunatic]

Originally Posted by wmaxt

Leaving a tank empty is also a fire/explosion hazard and if the tank is less than full the remaining fuel degrades quickly. Degraded fuel can/will gum up/destroy any fuel system component as it turns to varnish. Condensation can be drained but not as effectively as preventing it in the first place, aircraft are not stored empty or even below full, minus expansion volume, if possible. Down loading fuel to taylor the aircraft for a mission is common place.

Flying with empty tanks is common with aircraft esp. airliners and cargo planes to save weight for cargo or fuel economy. These aircraft are required to fill empty fuel tanks with inert gas since flight 800 went down. Even these tanks are not empty for extended periods since seals and other flexible parts dry and crack.

wmaxt

The fuel cells on the P-47N were backfilled with an inert gas as the fuel was consumed to minimize fire hazards should the cell take damage. I'm not sure but I think it was CO2 gas but it might have been nitrogen. Both gasses were used for backfilling by US aircraft in WW2.

And IIRC the fuel cells were welded aluminum.

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Lunatic

[lesofprimus]

I'm not sure but I think it was CO2 gas but it might have been nitrogen.

They actually used both....

[FLYBOYJ]

Originally Posted by lesofprimus

They actually used both....

They were - CO2 is now considered hazmat - N2 is "inert," the gas of choice for this stuff!

[wmaxt]

I belive a fuel "Cell" is lined with a compound to make it self sealing/more resilient to leakage while a welded metal tank is just that a "Fuel Tank". Not trying to be nitpicky but at this level of discussion its an important destinction.

wmaxt