Why doesnt a gas/glow engine deadstick on a down line when tank is nearly empty?

There is sufficient fuel in the line between the tank's clunk and the carb. The fuel pressure in the tank will remain unchanged as a function of exhaust pressure. An example might help. While on the starting bench, with the throttle wide open, the engine will continue to run for several seconds after I pinch the fuel line closed between the firewall and the high speed needle. The length of tubing between the clunk and where I pinch is longer than between the pinch and the carb.

Hope this makes sense.

Some day when I can call myself an experienced flier I will use good throttle control which means I will throttle back after initiating the down line which, in this case, will reduce the fuel demand and allow the engine to run longer yet.

What about Gas engines ?  With no back pressure?

Gas engine carbs have a well area that retains fuel. Kinda like a float bowl in a larger 2 stroke engine.

Why not Bladder tanks ? Like real planes?

There is a commercial bladder tank, called the Tetra tank, I think.

It does not make any difference if the tank is nearly empty or nearly full.

Check this recent thread out:

http://www.rcuniverse.com/forum/m_10...m.htm#10845494

Wow . That is a help. Thank you.

It doesn't matter where you pinch the line, there is no vent so the fuel flow stops immediately. That the engine doesn't stop right away means that the fuel mixture is rich and that incoming air is picking up fuel clinging to the crankcase walls and bottom. If it was at peak or lean it will stop immediately no matter how long the line or where you pinch it.