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Jun 27, 2005, 06:13 AM
fldmshlschroe's Avatar

Fuel Tank Clunk

Should the fuel tank clunk fall to the front of the tank when in a dive or should it just roll around the rear of the tank just above the back of the tank????

thanks all!
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Jun 27, 2005, 07:37 AM
Registered User
Ideally it should fall to where the fuel is -- at the front of the tank in a dive. If it doesn't, it could be because it's a bit too long so that it hangs up on the side of the tank, or because it's tubing is not flexible enough.
Jun 27, 2005, 08:41 AM
Bako's Avatar
wait wait. I thought fuel always in on the back side of tank. in dive the acceleraing force reacts and pushes fuel back. I'm not about UFO style flyind.
Jun 27, 2005, 09:24 AM
God is good
Viper Pilot's Avatar
If the clunk moves too far forward, the fuel line will become crimped and restrict fuel flow.

That is why the clunk position should be checked after a crash or extremely hard landing.

It should always be to the rear of the fuel tank!!

Jun 27, 2005, 10:10 AM
S.A.D. member
ivanc's Avatar
Viper and Bako have it right. Add my vote to them.
Jun 27, 2005, 11:08 AM
Registered User
I agree that the clunk line can become constricted if it moves too far forward, but I don't accept that it should always be towards the rear of the tank. The fuel is not always on the back side of the tank, and the whole idea of the clunk is to follow the fuel so far is is possible.

But, yes, there are problems if you try to implement this 100%.
Jun 27, 2005, 12:51 PM
God is good
Viper Pilot's Avatar
Originally Posted by abenn
. . . . but I don't accept that it should always be towards the rear of the tank. The fuel is not always on the back side of the tank . . . .
I've had many planes in an attitude that would put the fuel away from the back of the tank, away from the clunk, and have not had a dead-stick once the engine has been properly tuned in.

Granted, a sustained dive from way, way up might kill the engine because of a diminished fuel supply, but so far this has not happened. I think the plane would self-destruct on a dive like that before it killed the engine.

Viper Pilot
Jun 28, 2005, 10:56 AM
Registered User
The clunk belongs toward the back ...... Read the instructions !!!! If it is allowed to bend forward it will crimp off the line and starve the engine. Sorry to be so brash but think about it. ENJOY !!!! RED
Jun 28, 2005, 11:03 AM
Deletedfor proving Nauga wrong
Depends on the size of the tank...

In some of the small tanks the clunk would kink the pickup line and potentially get stuck near the front of the tank if it went forward. Usually such small tanks are used with smaller engines, and the fuel in the line is adequate to keep the engine running a few seconds... then if the engine is properly tuned it will very rapidly draw the air out and continue operating when the nose comes up. (but you may hear the engine speed up... as it pulls air instead of fuel)

My experience is that 10 to 12 oz tanks.. depending on shape are the break line between it being good or bad for the clunk to be able to go forward if the line inside the tank is "standard" medium silicon fuel tube. Thinner tube lets it be OK for the clunk to go forward n a smaller tank ( 6 oz is the smallest I haven't had problems with stuck clunks using small tube)

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