GRAUPNER MC-20 HoTT Programming Manual page 191

function.
Tail rotor AR
In normal fl ight, the tail rotor is set so that it
compensates for motor torque while the model is
hovering. It therefore generates some a certain
amount of thrust even in its normal position. The
level of thrust is then varied by the tail rotor control
system, and also by the various mixers which provide
all manner of torque compensation, while the tail rotor
trim is also used to compensate for varying weather
conditions, fl uctuations in system rotational speed
and other infl uences.
For auto-rotation, however, the main rotor is not
driven by the motor, but by the "windmill" principle.
Since this, in turn, does not generate any torque
for which the tail rotor must compensate, all
corresponding mixers are switched off automatically.
Since the absence of torque in auto-rotation also
means the above-mentioned thrust is superfl uous,
however, a different tail rotor confi guration is also
required:
Cut the motor and place the helicopter on the ground
in a level attitude. With the transmitter and receiving
system switched on, select the fl ight phase "Auto-
rotation" and then fold the tail rotor blades down. Now
change the value on the "Tail rotor" line until the tail
rotor blade angle of attack is zero degrees. Viewed
from the tail, the tail rotor blades should be parallel to
one another.
Depending on the friction and running resistance
of the gearbox, the fuselage may still yaw slightly,
however. This relatively slight torque must then be
corrected if necessary by adjusting the tail rotor
blade pitch angle. This value will always be a fi gure
between zero degrees and a pitch angle opposed to
the pitch angle in normal fl ight.
Detail program description - Helicopter mixer / Auto-rotation settings 191