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Fuel starvation in a dive?

Old 06-28-2006, 01:00 AM
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chevy43
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Default Fuel starvation in a dive?

I noticed the clunk can't swing to the front of the tank. How does the engine get fuel when diving?
Old 06-28-2006, 01:06 AM
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Razor-RCU
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Default RE: Fuel starvation in a dive?

I suppose there is a physics lesson in all this but I am gonna guess:

* The fuel stays at the back of the tank like when you swing a jug of water in a circle and it does not spill--

* Or there is enough fuel in the lines for a short dive-

Just guessing-
Old 06-28-2006, 01:27 AM
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KidVermin
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Default RE: Fuel starvation in a dive?

# 1 only applies to centrifugal force.

# 2 is more correct since the clunk tube will bend enough to pick up fuel unless the tank is lower than 1/2. I never use the stiff clunk tubing that comes with the tank kit; instead, I use small or medium fuel line.
Old 06-28-2006, 05:57 AM
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Default RE: Fuel starvation in a dive?

I have had problems on some planes with short fuel lines in a dive. As you surmise, the fuel in the line is the primary source. Typically in a dive, you reduce throttle, which obviously reduces fuel demand. Another trick I've used is to put a loop in the fuel line between the tank and the carb. This provides an additional fuel reservoir. A large fuel filter can also help. In the extreme, a header tank can also help.

Most dives don't last long enough to require a lot of fuel.

Brad
Old 06-28-2006, 06:48 AM
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RCKen
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Default RE: Fuel starvation in a dive?

The fuel stays in the back of the tank because of inertia. In fact, I prefer to add a small bit of stiff tubing in the pick up line so that it can't move to the front of the tank. This will eliminate the clunk from getting stuck into the front of the tank. See attached diagram to see what I'm talking about.

A common mistake a lot of beginner's make is while on the ground they will hold the nose of the plane down to check their needle settings. Doing this on the ground can and will cause the motor to lose fuel pickup because the fuel will run to the front of the tank. This because the plane doesn't have any forward momentum and therefore doesn't have any inertia. They will then assume that the same problem exists in the air, which it doesn't because of the motion of the plane.

Hope this helps

Ken
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Old 06-28-2006, 06:53 AM
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Ross Kean
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Default RE: Fuel starvation in a dive?

If you are accelerating in a dive, the fuel will remain in the back of the tank. If the fuel level is at least a third full, you will be OK on a modest (non-accelerating) downline. Otherwise, you will usually be OK with the fuel in the lines for several seconds. I guess that there might be an issue with a very long vertical dive where there is minimal acceleration (beyond normal gravitational acceleration). I have never had a flame-out in a dive situation and I would never even consider a clunk line flexible enough to fall to the front of the tank. It's too easy for such a line to kink ot get caught up at the front of the tank.

just my experience.

Ross
Old 06-28-2006, 09:05 AM
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skiman762
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Default RE: Fuel starvation in a dive?


ORIGINAL: chevy43

I noticed the clunk can't swing to the front of the tank. How does the engine get fuel when diving?
are you having this problem or asking if it is a problem ?
Old 06-28-2006, 01:46 PM
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chevy43
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Default RE: Fuel starvation in a dive?

I'm not having a problem - I'm just trying to understand how it works. I just set up a fuel tank and wanted to know how it works so I could set it up right.

Obviously I would like my engine to come on line if I dive down close to the ground and need it to get me out of trouble.

Seems like this could be a problem in a steep glide as well.
Old 06-28-2006, 02:32 PM
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Default RE: Fuel starvation in a dive?

Besides the inertial force that keeps the fuel at the back of the tank, there is also pressure within the tank which pushes the fuel towards it's outlet (the carburetor) provided as mentioned that you're 1/3 full or more.. with little fuel in the tank, yes you can have a flame out in a long-not so vertical... dive... hasn't happened to me (yet)

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