What cause idle speed (RPM) higher than set after flying for 5-8 minutes. Sometimes I can not land because of high speed of airplane. How to solve the problem.

Thanks

Idle speed is set in yout transmitter by using the ATV function to set the throttle servo "End Point," or minimum setting.

If your setting keeps changing, check your throttle cable for binding, or on the other hand, flexing.

Either of these extremeties can prevent the throttle from closing in fully when the Tx throttle stick is moved to the idle position.

When you first start your engine its still cold and it will idle lower, when you take it up and the engine has warmed up you will find that the engine is idling at a higher RPM, that might be one reason why you are experiencing the problem. Might that be it?

if the airplane consistantly won't slow down adequately to land... try the next lower pitch prop... usually also going to the next larger diameter to maintain the load factor on the engine.

The lower pitch provides less pull at low rpm. Larger dia provides more "disk area" and that gives significantly higher static thrust (which is what you want for high climb rates) Top speed of the model might be reduced a little... but I doubt you'll notice. (sometimes top speed increases if you are still in the speed range where static thrust is more important than pitch)

As the tank level drops the fuel mixture leans slightly. That could account for a small increase in idle speed, assuming all else is correct. You might try setting the high, and low, speed needles when there is just a small amount of fuel in the tank.

First, when you adjust the low end, the engine should have been running for about 2 - 3 minutes so it is completely warmed up. Your trim for the throttle should be adjusted so that at 1/2 - 2/3 of the way is where you start the engine and about 1/4 - 1/3 of the way open is where it should idle with the throttle stick fully closed. After you have adjusted the idle AND trim, start the engine, make sure everything is OK (high speed needle), taxi out to the flight line, REDUCE THE TRIM to the idle position, THEN take off. Set this way, you can kill the engine by fully closing the trim. Once you have set the low end, you should not have to touch it again.

Another thing to keep in mind/check is the brand of propellor.

An APC prop is more efficient than a Master Airscrew prop. This is due to the blade shape.

If you are presently using an APC prop (the grey props), try a Master Airscrew (the black props) of the same size. What you will notice is the following: The Master Airscrew will create a little more noise, the plane will slow down faster and MAY also idle lower due to the wider blade (more resistance) and you will loose a little on the top end which is rarely noticeable. If you are presently using a Master Airscrew, drop down one size in the pitch and/or go up one inch in diameter.

On the reverse of this - using an APC instead of a Master Airscrew. I have seen a NOTICEABLE difference in power/performance and a lower noise level.

Most of my planes use an APC prop, however, on two of them I use a Master Airscrew because the APC has too much thrust. On my Rascal 40 (46 FX) I switched to a Master Airscrew because the ONLY WAY I could land with the APC was to kill the engine. On my Rearwin Speedster I switched to a Master Airscrew so it would slow down more for landing (I really dislike landing "hot").

Hope this helps.