GRAUPNER mc-16 Programming Manual page 69

Setting the Throttle and Collective Pitch curves:
Fundamental Explanations
Setting the Throttle and Collective Pitch
The tuning of throttle and collective pitch, and thus
the performance curve of the engine and collective
pitch control, is the most important adjustment
procedure with a helicopter model. The goal of this
tuning is it to achieve a constant main rotor speed
throughout the entire collective pitch range in flight,
and to ensure that at the point at which the helicopter
hovers is achieved with the throttle / collective pitch
stick as near as possible to a central position.
Firstly a wide-spread misunderstanding must be
clarified for model helicopter pilots:
The model helicopter throttle servo must NEVER be
connected just to an auxiliary channel and operated
via a proportional module alone!!!
Although throttle and collective pitch are controlled
by separate servos, these are always operated
together by the throttle / collective pitch control stick
(the only exception is Autorotation). This coupling is
done by the helicopter program in the transmitter.
The trim levers for the throttle / collective pitch
control stick work, in the helicopter program,
exclusively on the throttle servo and then only in the
minimum throttle position of the control stick.
A proportional module attached to CH 6 permits a
shift of the collective pitch range around by range of
±25% without influencing the throttle servo.
The helicopter program of the mc-16/20 transmitter
permits the programming of independent throttle and
collective pitch curves.
In addition to the central position and two end
positions appropriate to the throttle / collective pitch
control stick, individual values entered for the
collective pitch and throttle are stored in each case.
No-load setting and throttle preselect
The no-load operation setting makes it possible to
set the engine RPM for no-load, without influencing
the hovering flight setting.
With the option "TL1" the throttle servo position is set
in such a way that with the control stick in the idle
position one achieves stable no-load operation. With
the trim lever and the idle setting, the engine can be
turned off.
During flight it is possible to switch over to a limited
throttle setting (i.e. minimum RPM), which is
generally called "Idle-up".
The "Idle Up" setting acts to prevent excessive rotor
RPM and is primarily for use when the collective
pitch is taken under the point of hovering flight, for
example with fast, steep approach flights. Therefore
it may only be effective below the hovering flight
position (central position) of the pitch control stick.
Occasionally a changeover of the throttle curve is
used for an increase in the system RPM for certain
flight manoeuvres, usually for helicopter models
whose rotor construction does not permit a constant
RPM for hovering flight and aerobatics. In addition it
is used to ensure the settings for both hovering flight
and aerobatics are optimal: Low system RPM for
calm, soft stick reactions and low noise in hovering
flight, higher RPM for aerobatics, within the range of
the maximum power of the engine. In this case the
throttle curve is also changed within the hovering
flight range.
In order to allow for all these requirements, the mc-
16/20 transmitter possesses a changeover system
for throttle and collective pitch curves which goes far
beyond simple idle-up. If you attach additional
external switches to connections 4 and 5 on the
transmitter plate, they allow up to two alternative
throttle and pitch curves to be programmed and
called up during flight.
The announcement appearing in the display for the
option of "TL..." depends on the switch positions:
"TL1:" Both switches in the OFF position
"TL0:" Switch 4 = ON, switch 5 = OFF
"TL2:" Switch 4 = ON or OFF, switch 5 = ON
Preferable to two independent switches is the use of
the 3-way differential switch, Part No 4160.22, which
then gives the following switching:
Lower position: Throttle / Pitch Curve 0
Centre position: Throttle / Pitch Curve 1
Upper position: Throttle / Pitch Curve 2
In this case use curve 0 for the basic adjustment in
place of curve 1
Not only can the throttle minimum values for all three
switching positions be set differently, but also the
values for hovering flight throttle and minimum
collective pitch. The value for full power is set and
shared for all switching positions together, likewise
hovering flight collective pitch and maximum
collective pitch.
Helicopter 69