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The Esky 6 channel Transmitters (TX) are famous for confusing
pilots, especially when they try to set up the helicopter
correctly with ZERO PITCH at 50% Throttle, and when they are
trying to understand what the IDLE UP switch (and Idle up Mode)
really does, and how to use (or not use) it.
Hopefully this Tip will explain it in relatively simple
terms so that you will understand all about the relationships
between Throttle and Pitch curves, and Normal and Idle Up modes
The diagrams below have been taken from the Esky
Documentation, and hopefully will help everyone to understand
how these curves interact with each other. (You can click each
image to bring it up larger in a new window for ease of use)
In the first diagram below, you can see the throttle curves
for NORMAL and IDLE UP (spelt IDEL UP by the Chinese translators) on
the left, and the equivalent pitch curves on the right. (Also
note they call it 3D in one heading, and IDEL UP in others)
In NORMAL MODE the throttle curve is in fact a straight
line at 45 degrees from 0% to 100%, which is a reasonable
"curve" for beginners to use. However, look at the
pitch curve for NORMAL MODE at the right and you will see that Pitch
range starts at 50% of the full available range and
rises linearly to 100%.
What does that mean in simple terms then ?
Well, as you push the throttle lever up, it will pass
through all of the points 0,1,2,3,4,5 shown at the bottom of the
graph. So at zero throttle you will have whatever pitch setting you
have configured it to, which is NORMALLY around -2 or -3 degrees of
PITCH. As you increase the throttle, the pitch also increases gently
and in a linear fashion up to the full pitch setting, typically
around +8 or +9 degrees.
While this happens, the throttle is increasing linearly all
the time, so this means that the motor and therefore the rotor head
will spin up to a decent head speed at 50% throttle, BUT you will
still have NO or VERY LITTLE PITCH on the blades, so the helicopter
will NOT TRY TO LIFT OFF.
Now lets move on to the second pair of curves, marked as
IDLE UP. (Well IDEL UP in Chinese)
You can see immediately that the throttle "curve"
is completely different here, starting right up at the top at 100%
throttle with the throttle stick FULLY DOWN. It then DROPS
to 50% throttle as you move the throttle stick UP towards
mid stick. Once you move the throttle stick above 50%, the
throttle starts to increase again, and returns to full
throttle with the throttle stick at 100% throttle.
Meanwhile, the matching pitch curve is still a straight
line, but this time it DOES NOT START AT 50%, but rather at ZERO
PITCH. As you increase throttle, the pitch also increases
linearly all the way up to 100 throttle.
Confusing isn't it ?
Well, Yes and No really.
Lets just think abut these two and see what happens when
you want to make your helicopter take off.
You increase the throttle slowly to 50%, and the rotor head
will speed up to 50% of it's maximum speed, as the left hand top
graph shows us. At the same time of course, the Pitch is ALSO
CHANGING. So by the time
the throttle is at point 3 (50% throttle) the pitch curve has moved
to a position half way through the pitch range. Now lets
assume you have a NORMAL Pitch range of -3 to +8, the TOTAL RANGE
you have is 3+8, or 11 degrees, so at 50 throttle, you will have the
pitch angle that represents 5.5, or just over half the entire range.
That means a pitch angle of around +2 to +3 degrees (-3 + 5.5 =
That is just about right, as it means the helicopter will
just be going a little light on the skids.
Now as you push the throttle up past mid throttle, both
head speed and rotor pitch angle are increasing at pretty well the
same rate. At around 2/3rds throttle, the helicopter will be
lifting off quite happily.
IDLE UP MODE
This is where it all gets tricky. As the lower graph
shows VERY CLEARLY, with the throttle stick FULLY DOWN, if you pull
the IDLE UP Switch forward to engage IDLE UP MODE, you will get 100%
THAT IS FLAT OUT HEAD SPEED -
Now we all know that this scenario is NOT GOING TO BE A
GOOD THING TO DO, as the first thing that will most probably happen
is that the motor will try to spin up to full rpm immediately, the
rotor blades have a lot of inertial to stop them being spooled up
that quickly, and the typical result is that you hear a nasty noise,
and then find that you no longer have ANY TEETH LEFT ON THE MAIN
GEAR, which is really not too surprising.
The IDLE UP THROTTLE setting is designed to allow you to
have a reasonably CONSTANT HEAD SPEED, which allows you to fly
inverted and do all sorts of other things, but clearly you need to
find a way to be able to switch to IDLE UP MODE safely.
The other thing to note is that the total pitch range in
IDLE UP MODE is typically -8 to +8 degrees, so a range of 16 degrees
is available, as opposed to the meagre 11 degrees total range we get
in NORMAL MODE. THIS IS IMPORTANT TO REMEMBER, as -8 is a lot
of NEGATIVE PITCH.
Well, all you need to do is to compare the top NORMAL graph
and the second IDLE UP graph to spot the solution. There is
JUST ONE POINT WHERE BOTH THROTTLE LEVELS ARE THE SAME, and that is
at mid throttle. (point 3 on the bottom range)
You may also have spotted that once you are up to 50%
throttle, there is no difference on the throttle curve (only)
all the rest of the way up to full throttle, so you can indeed
switch between NORMAL and IDLE UP modes anywhere from mid throttle
to full throttle, BUT DEFINITELY NOT BELOW 50% throttle stick.
However, there is is a teeny little flaw in this apparently
Take a good look at the pitch curves...
Yep, your dead right, in IDLE UP MODE there is NO POINT AT
WHICH THE PITCH CURVES CROSS AT THE SAME SETTING.
As you can see from the pitch range values I have added, in
NORMAL MODE at 50% throttle, you will have around 2 to 3 degrees
pitch. If you switch to IDLE UP MODE at this throttle setting, the
pitch is going to go to zero, or possibly a little less, which means
that although your skids were just getting light on the ground in
NORMAL MODE, the pitch has dropped, and there may even be a small
amount of negative pitch which will pull the helicopter downwards a
This is not a particular problem, but you need to be aware
of it, and ready for it, especially if you switch between modes at
higher throttle settings, as the difference in pitch becomes more
CLICK IMAGE to enlarge in a new window
There is one trick you can use to help yourself out here,
and that is to use the Pitch Adjustment Knob that is on the top left
of all Esky stock TX's. The graph immediately above shows what
effect this knob has on the PITCH CURVE. I think it is fairly
self explanatory, in that it shows that you can change the position
of the diagonal pitch line upwards or downwards throughout the
This means that if you INCREASE the value on this knob by
turning it clockwise, the overall pitch range will be HIGHER, but
this means that due to the higher loading, the head speed will
DECREASE, and vice versa. The change you make here effects
BOTH NORMAL and IDLE UP MODES in exactly the same way.
Please do NOT FORGET if you set this knob to anywhere but
12 o'clock, then the pitch change will be different when you switch
between NORMAL and IDLE UP Modes.
If you have the 35MHz TX (it is not on the 2.4GHz TX, as it
has been replaced with a gyro gain control instead), you can also
use the right hand knob on the TX to further adjust the Pitch to a
more realistic "curved" line instead of the straight line
we have seen so far. (Most computer radio users have curves
more like these)
The change this knob makes is not large, but it is a useful
control to try to match the helicopter setup against your flying
CLICK IMAGE to enlarge in a new window
WHY YOU USE IDLE UP WHEN DOING THE MECHANICAL PITCH
This should now be really easy for you to answer by
yourselves - just look at the graphs again....
Quite correct, it is ONLY IN IDLE UP MODE that 50% Throttle
stick equals exactly 50% pitch, and this is the ONLY SETTING we are
interested in when setting the pitch range.