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C1 - GENERAL - What exactly is the Idle Up, or Devils switch ??

This always seems to confuse new helicopter pilots, but in reality it is a very useful switch, once you understand it's full functionality.

The first thing to understand is that the name itself is somewhat of a misnomer.  It is really only called IDLE UP because the Esky stock radios decided to call it that.  On all other radios it is labelled as the F-Mode Switch, which is far more correct....

The first thing I need to do here is to WARN  all those of you that have the stock Esky Radio system NOT TO FLICK THE IDLE UP SWITCH ON TO SEE WHAT HAPPENS. The result will almost certainly be disastrous, so please read on before touching it.

So what is the Idle-Up (Devils / F-Mode ) switch all about. ?

To fully understand it we need to digress a little first and talk about throttle and pitch curves.

All radios provide at least ONE of each of these curves which are built in to them.  They control exactly how fast the motor runs, and hence the rotor head speed, and the amount of positive or negative pitch that the main rotors will have at any given point as you move the throttle stick up and down.

The standard curves are usually reasonably mild, and are designed to let a new pilot fly and learn to hover successfully.  a typical curve will go from about -3 degrees to + 9 degrees.  However, as you progress, you tend to want to be able to change these curves to make the helicopter more agile.  That is where the IDLE UP switch comes in.

WARNING - The Esky radio
The pair of curves that are built in to this radio for the IDLE UP mode are designed more for 3D flying, and therefore the pitch curves provide far more negative pitch than any reasonably new pilot can cope with. Typically you will see -10 to +10 degrees of pitch.  This means that when the throttle stick is pulled down below half way, the helicopter actually starts to fly DOWNWARDS, TOWARDS THE GROUND due to the negative pitch

Equally on the Esky radio, the throttle curve is set to keep the motor running constantly at around 80% of its maximum revs.  That is actually a good thing for real helicopters, who all use constant head and engine speeds, but with the Esky radio as soon as you throw that switch into IDLE UP mode, it spools up very quickly, EVEN THOUGH YOU HAVE THE THROTTLE FULLY CLOSED.  This is because the stock Esky ESC (Electronic Speed Controller) does not provide a Soft Start option, so the motor picks up speed WAY TOO QUICKLY, and this often results in the teeth being stripped off the main gear due to the sudden acceleration.

At the same time as the head spools up, and because the throttle is still fully DOWN, the helicopter has MINUS 10 degrees of pitch, which means it is standing on the ground trying its best to pull itself down into the ground. - NOT VERY NICE...

Other computerised radios
With radios such as the Spektrum DX6/7 and Futaba/JR, this switch is usually called the F-Mode (Flight mode).  Because not can you can change the settings of both throttle and pitch curves for normal flying, but the F-Mode switch provides an equally configurable second set of curves.  Some of the 7-9 channel radios even offer a third set of settings as well via the F-Mode switch.

In these cases, many pilots initially set both sets of curves to be exactly the same, so that flick the F-Mode switch makes no difference, but as you progress, you can then adjust the second set of curves to be anything you want them to be, for 3D flying or even more gentle for scale flying.  Hence you can see that the term F-Mode is far more fitting than IDLE-UP.

This means that you are not FORCED to have the excessive negative pitch range provided by the Esky Radio, while still benefitting from the modified throttle and pitch settings you choose.

The other thing that you can do with computerised radios is to use the throttle curve to "copy" the behaviour of the Esky IDLE-UP range by setting it to be a dead straight line at 85-90% throughout the throttle range.  However, when using these types of radios you most often also change the ESC (Electronic Speed controller) to a better one, and these will typically provide  what is called a Governor Mode.  When using one of these, the 85-90% throttle setting is identified immediately by the ESC, and the governor then takes over control of the spooling up so that it is nice and soft getting up to full speed.

So, the bottom line is .........

If you have an Esky radio, use the IDLE-UP SWITCH VERY WARILY. It is best to have the throttle at about 50%, but just before the helicopter wants to take off, and then flick IDLE-UP  ON.  Once it is on DO NOT SWITCH IT OFF AGAIN until the helicopter is firmly landed on the ground.

With a computerised radio, set your curves carefully to suit your own particular needs and preferences.



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