Where does the fuel go while in flight?
08-04-2004, 06:53 AM
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Where does the fuel go while in flight?
I have long pondered this question, but have not found the answer. Perhaps the engineers and physicists can tell me....where does the fuel in the tank go while in the various conditions of flight? I imagine that in a vertical climb, the fuel would be at the back of the tank...but what about in a power off vertical downline?...or in straight and level flight? Thanks for your comments.
jim
jim
08-04-2004, 07:09 AM
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RE: Where does the fuel go while in flight?
It would go towards the predominant G force.
In un accelerated level flight it would be lying on the bottom of the tank, just as if it were sitting on the ground. It might be sloshing around a bit from the engine vibration but mostly on the bottom.
I the case you ask about, it depends. Power off vertical dive, if you start off from a push over up high, more than likely the fuel is going to roll forward and lie on what was the front of the tank. As the aircraft accelerates due to gravity, it may start to float slightly off the front. I doubt it will blob up and float free altogether because without power you won't be accelerating to a free fall rate. Then as you reach terminal velocity the fuel will be firmly on the front of the tank.
Now as you become facinated with visualizing the fuel in the front half of the tank, you will forget to pull up and your aircraft will impact the ground. Up to a fraction of a second before the tank slams into the now stationary firewall that fuel will still be filling the front end of the tank. A nanosecond later chaos theory takes over and the fuel is radically distributed over the plane and the stationary ground.
[X(]
In un accelerated level flight it would be lying on the bottom of the tank, just as if it were sitting on the ground. It might be sloshing around a bit from the engine vibration but mostly on the bottom.
I the case you ask about, it depends. Power off vertical dive, if you start off from a push over up high, more than likely the fuel is going to roll forward and lie on what was the front of the tank. As the aircraft accelerates due to gravity, it may start to float slightly off the front. I doubt it will blob up and float free altogether because without power you won't be accelerating to a free fall rate. Then as you reach terminal velocity the fuel will be firmly on the front of the tank.
Now as you become facinated with visualizing the fuel in the front half of the tank, you will forget to pull up and your aircraft will impact the ground. Up to a fraction of a second before the tank slams into the now stationary firewall that fuel will still be filling the front end of the tank. A nanosecond later chaos theory takes over and the fuel is radically distributed over the plane and the stationary ground.
[X(]
08-04-2004, 07:23 AM
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RE: Where does the fuel go while in flight?
Thats hillarious...thank you for the enlightenment, and the comic relief. I did get a good laugh out of it. In a vertical downline, I then am left to worry about having enough fuel already in the pickup line to keep the motor running until the next flooding of the pick up clunk. And, since it is expected that air will be drawn into the fuel line during the downline, why then does the motor not cease to run when that blob of air reach the carb?
jim
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08-04-2004, 07:40 AM
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RE: Where does the fuel go while in flight?
> why then does the motor not cease to run when that blob of air reach the carb? <
My non-expert observation is that condition occurs commonly on the ground and can be seen through the transparent fuel line. As I run my tank dry at the end of the day the air gaps in the line get sucked up quickly and the next slug of fuel is pulled into the carb while the engine drains the line. Let the experts explain what is happening here.
My non-expert observation is that condition occurs commonly on the ground and can be seen through the transparent fuel line. As I run my tank dry at the end of the day the air gaps in the line get sucked up quickly and the next slug of fuel is pulled into the carb while the engine drains the line. Let the experts explain what is happening here.
08-07-2004, 11:16 PM
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RE: Where does the fuel go while in flight?
This highly profound question has bothered me for years. I like to use a very flexible clunk line that is longer than usual, so that the clunk sorta curves around the back of the tank, and is able to slide all the way forward in long, power-reduced dives, where the engine would otherwise would soon be sucking air. I haven't seen any terribly ill effects from using a rather small diameter clunk line, but I use mostly tuned pipes, and they generate a lot of tank pressure.
