RCU Forums - High Engine idle reqd in downlines

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High Engine idle reqd in downlines

Why is high idling rpm required for engines in vertical downlines say of 1000 feet------At 1300 rpm or so which is just right for landing the rpm is too slow for extended vertical downlines and during pull-out from a manuever the engine wants to die.

Someone said that since the prop is turning with a very low load in downlines as the engine is no longer countering Gravity the carb/diaphragm pulls in more gas than the Combustion burns in every respective prop revolution causing flooding.This causes the engine to die.

While keeping a high idle for such conditions does solve the problem it accelarates the model.

Any further info would be highly appreciated.

RE: High Engine idle reqd in downlines

There are really two reasons for this. On extended down lines the engine could easily load up especially a reed block twin. Then if you have too low an idle during a spin the carb pump at lower RPM may noy have enough pull to get the fuel out of the tank.

Shawn

RE: High Engine idle reqd in downlines

Quote:

ORIGINAL: ajay1

Why is high idling rpm required for engines in vertical downlines say of 1000 feet------At 1300 rpm or so which is just right for landing the rpm is too slow for extended vertical downlines and during pull-out from a manuever the engine wants to die.

Someone said that since the prop is turning with a very low load in downlines as the engine is no longer countering Gravity the carb/diaphragm pulls in more gas than the Combustion burns in every respective prop revolution causing flooding.This causes the engine to die.

While keeping a high idle for such conditions does solve the problem it accelarates the model.

Any further info would be highly appreciated.

Hey Ajay1 .... It's quite possible that your low end needle may be either too rich or too lean..... At idle (on the ground) when you quickly power up to full throttle, does the engine hesitate or want to shut down? Or does it load up with fuel & has to clear out before the full power comes up (smoke coming out of the mufflers)?

What engine are you using?

I've not had a problem like that on a downline, even though my throttle is set low enough to be able to enter a spin.
Wayne
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