GRAUPNER MC-22S, Programming Manual

Page: 93 / 180

93 Program description: Mixers
by setting the control travel to 125% in the » Control
adjust « menu.
If you would like to obtain fi ner control of the throttle
limit slider, you can also use “Expo throttle limit” (page
54). This gives you the opportunity to locate the idle
setting exactly at the ratcheted centre position of the
slider, which you can easily fi nd at any time:
Set the throttle limiter to its centre detent, and adjust
the value for “EXPO throttle limit” until the motor idles
perfectly, i.e. without moving the slider from the rat-
cheted centre position. The motor can then be star-
ted without problem in this position. To cut the motor,
slide the throttle limit control to the bottom end-point,
i.e. without even touching the Ch1 cut-off trim.
The limiting action of the throttle limiter is shown by a
horizontal bar in the throttle curve graph:
C h a n n e l 1 T h r o t t l e
I n p u t - 7 0 %
C u r v e O u t p u t - 7 0 %
o f f P o i n t ?
®
O
U
T
P
U
T
- +
1
10
0
« N o r m a l »
The output signal to the throttle servo cannot be gre-
ater than the value dictated by the horizontal bar, in
this illustration max. approx. -70%.
Tip:
If you wish to time the fl ight of a (glow-powered) mo-
del helicopter, you can assign a control switch to the
throttle limit slider, and then use this to switch a timer
on and off; see page 72.
Channel 1 tail rotor
C h a n n e l 1 T a i l r o t .
I n p u t 0 %
C u r v e O u t p u t 0 %
o f f P o i n t 1 0 %
®
O
U
T
P
U
T
-
+
1
10
0
« N o r m a l »
The purpose of this mixer is to provide static torque
compensation. The fi rst step is to ensure that the di-
rection of main rotor rotation has been entered cor-
rectly in the »
Helicopter type « menu, page 53.
This mixer should be set up in such a way that the he-
licopter does not rotate around the vertical (yaw) axis
(i.e. deviate from the hover heading) during a long
vertical climb or descent, due to the change in torque
of the main rotor. At the hover the yaw trim should be
set using the digital tail rotor trim lever only. For a re-
liable torque compensation setting it is essential that
the collective pitch and throttle curves are already set
up correctly, i.e. that main rotor speed remains con-
stant over the full adjustment range of collective pitch.
This third fi ve-point curve applies only to the control
curve of the tail rotor servo when the throttle / collec-
tive pitch stick is moved, whereas the “Channel 1 cur-
ve” (see page 70) applies to
all servos which are af-
fected by the throttle / collective pitch stick. Note that
the output signal of the “Channel 1 curve” also acts
as the input signal for the tail rotor curve which is pro-
grammed at this point: the vertical line in the diagram,
which moves in parallel with the throttle / collective
pitch stick, follows the actual Channel 1 curve as set
in the »
Channel 1 curve « menu.
As standard, the software includes a three-point tail
rotor curve with a linear mixer ratio of 30%. Using the
method described above, you can modify the mixer
by placing two further reference points on the curve,
and thereby set asymmetrical mixer ratios above and
below the hover point.
In the auto-rotation fl ight phase this mixer is auto-
matically switched off.
Tail rotor throttle
The tail rotor normally compensates for the effect of
main rotor torque on the fuselage, but it is also the
primary method of controlling the helicopter around
the vertical (yaw) axis. However, if you increase tail
rotor thrust by giving a yaw command, motor power
must also be increased to avoid a fall-off in system ro-
tational speed.
In this menu you set the degree to which the thrott-
le follows the tail rotor. The throttle only follows the
tail rotor
on one side , i.e. to the side where tail ro-
tor thrust is increased, and the adjustment range is
therefore 0 to +100%. The direction of mixing vari-
es according to the rotational sense of the main rotor
(left or right), and this must fi rst be set correctly in the
»
Helicopter type ” menu. For left-hand rotation sys-
tems, e.g. HEIM/GRAUPNER helicopters, the thrott-
le follows the tail rotor when the tail rotor stick is mo-
ved to the left. Right-hand rotation systems: when the
stick is moved to the right.
In the auto-rotation fl ight phase this mixer is auto-
matically switched off.
Programming notes:
To set the mixer value accurately you should fi rst fl y
several high-speed pirouettes in the opposite direc-
tion to main rotor rotation (i.e. with a HEIM system
machine, pirouette to the left). Alternatively, hover the
helicopter in a cross-wind heading on a fairly breezy
day, holding in the required large tail rotor defl ection.
The mixer value should now be adjusted until the ro-
tational speed does not fall off in this situation. For a
HEIM system machine this value needs to be around
30%.