I have 3 question for airplane as :
1. What is meaning of idle up and idle down?
2. What is relation between throttle and idle?
3. What is relation between idle down and engine stalling.

Well Idel up is mostly used on helicopters and lets us do 3d manuevers without lowering the throttle. idel is when the engine is sitting at low rpm and usally is when the stick is all the way down on the transmitter and throttle is when you add power to the engine usally by increasing the stick on the transmitter.

If you are talking about the idle-down function found in Futaba (and probably others) radios, it is a function that lets you choose two idle rpm settings. I use this function with my Extra 300. High idle for aerobatics, to be absolutely sure that the engine won't quit when I chop the throttle, regardless of attitude, and when it's time to land I flick the idle-down switch to get lower idle and minimum thrust. It is basically two different idle rpm settings for different "flight modes".

Thank you very much Sandal ! I bought Futaba FF9 CHP from my friend,but really I don't know how to use it. So,I started to read the manual, but still don't understand about meaning and relative between Throttle and Idle up and Idle down. How to setting them to each events? In the manual explained that Idle down will be prevent engine stalling. What meaning of engine stalling? I knew only aerobatic stalling maneuver. Please give me more details,because I just start to learn as baby. Thank you agian for your kindly please me.

This is how I have done it (Futaba 9C):

The end point function should be set up to have the carburettor fully open when the stick is all the way forward, and a reliable idle with the throttle stick all the way back. Don't worry about idle up or idle down for now.

Start and tune the engine, and use the throttle trim next to the stick to fine tune idle rpm. This will change a little depending on weather and fuel level (and a couple of other things). This is the "high idle" setting, so let it idle a little faster than the lowest reliable rpm, to make sure it won't quit in the air.

The idle-down function assigns a certain amount of throttle reduction to a switch. In other words: Idle down off - high idle (for aerobatics and max reliability), idle down on - low idle (for landings and steeper descents without gaining too much speed). You can set the percentage of throttle reduction in the menu, but this is not critical at this point. The throttle trim next to the stick will trim whatever idle setting is active. If idle down is on and you trim idle rpm up, only the idle down setting will be affected (and vice versa).

There is also a function called throttle cut that works almost like the idle down function, that stops the engine when you flick the switch.

Idle up is usually a heli function (enables you to fly inverted), but some airplane radios might have normal/idle-up instead of normal/idle-down.

Hope this clears up more than it confuses.

Here are my answers to this question in the airplane mode.
1) When you set your idle before flying some time the plane comes in too fast after you have flown and are ready to land. You can use idle down to get the engine to slow down enough for you to land by waiting until you are almost on the ground and then flip the switch and the engine will turn real slow. BEcause the plane is moving through the air it will not stop. I use this to land my planes at a really slow speed.

2) On the engine, you can move the throttle up to get the engine to run at it's maximum speed and down until it stops. When you move the throttle to the position where the engine will turn over at it's slowest, reliable speed, this is idle. Idle is usually the setting to make the engine turns slow so you can land and the engine never shuts off until you are ready.

3) As in number two, you want the slowest, reliable speed for the engine to run. If you turn on idle down, then the engine will turn slower than this and it will usually turn off or stall.

I hope this helps to explain it.

This is how/why I use the idle up/idle down method. I've got it programmed on a switch.

When flying IMAC maneuvers such as hammerheads (stall turns) and spins, it is necessary to actually stall the airplane. There at times that you need to have your engine idle for quite a long time before getting the airplane to stall such as entering a spin, either inverted or upright. When you have the idle set for landing speed, the airspeed actually helps your prop keep turning at a higher RPM. But, when you're looking for a complete stall, you often have to have a couple of hundred less RPM due to the lack of forward movement and more like the chance of your engine quitting.

As mentioned before, I've got mine programmed on a mix switch. I usually set the idle up about 200 RPM more than the low idle. That assures me of a good slightly higher than low speed idle for engine reliability. I usually flip the switch once in the air for idle up and flip it off when I'm ready for landing. I'm never hunting for my trim switch to do that for me. I've also go my igntion on an optical shutoff switch so, in essence, I never touch my idle trim for any reason. I keep that at the center detent. All the adjustment are done in the travel setup before ever letting go of the airplane.

Hi! Sandal ,Geistware and John;
At first,Thank you very much for your reply for me. Now I understood more than last time. I would like to comfirm my image for this matter, but I don't know how to attach figure to this post.

Posting Images "How-To"
[link]http://www.rcuniverse.com/forum/m_2629917/tm.htm[/link]

Ken

Thank you very much RCKen !

Hi ! Sandal;
I would like you to comfirm my image for Idle down as below figure ( A is correct or B is correct ?)

...it doesn't look quite right, but I have made a diagram

Thank you ! Sandal. I already clear for your kindly reply. But I have many questions to ask you as belows:
1. I think that you are using FF9. But I think that FF6 was enough for airplane control. Why did you chose FF9 for your airplane? How to use CH 7,8,9 ?
2. Can you explain me for AUX-CH Function ? I already read manual,but I did not understood. What is meaning of AUX-CH and How to use it ? In this function, " Vr-A " means Knob-A or not?
3. Can you advise me for some rc airplane books to make more better flight.
4. Someone told me to make myself model. How about you?

vuth,
I can answer questions 1 and 2, but I need a little help with 3 and 4...

1. I had a Hitec Eclipse and found out that it didn't have all the functions I needed for my helicopter. The FF9 has two extra channels and more advanced gyro/governor mixing, so I bought one and sold my Eclipse. A basic four-channel radio is sufficient for flying a standard airplane (ailerons, elevator, throttle, rudder), but the more advanced radios are required when you need p-mixes, idle-down (or up), air brakes etc. The need for more than six channels comes when you have several wing servos and perhaps flaps or retractable landing gear. My Flyin' King has two aileron servos (to make it easy to adjust aileron differential, flaps and a tow release, and this setup requires 7 channels. Bottom line: An FF9 or a similar radio is generally not needed for an airplane, but the extra functions and channels are often very nice to have because they make adjustments and programming easier. It depends on what you want and what you need.

2. In the FF9's menus, channels 7, 8, and 9 are called AUX1, AUX2 and AUX3. These channels can be operated by a Vr knob, a switch or mixed. You can select which knob or switch you want to control each channel. Or, if you have two elevator servos, you can connect one to channel 2 and the other to AUX1 or AUX2, and use a p-mix to copy the default elevator channel (master ELEV, slave AUX1 (or AUX2), trim ON, link ON, rate 100%, switch [any], position NULL)

3. I know that there are several very good books on RC flight, but I don't know much about them. Maybe someone can point us in the right direction.

4. I'm not sure that I understand the question...? (English is not my first language...)

sandal
Thank you very much for your helps. I will be locate to make my other questions on transmitter forum.