Graupner GmbH & Co. KG MC-20 用户手册

187

Practical approach

Although the throttle and collective pitch control 
systems are based on separate servos, they are 
always operated together by the throttle/pitch joystick 
(except during autorotation fl ight). This coupling is 
performed by the helicopter program automatically. 
In the 

mc-20

 HoTT program, the trim wheel of control 

function 1 acts principally only on the throttle servo. 
However, in the »Stick mode« menu (see page 106) 
a decision can be made if this should be used for idle 
trimming as part of the throttle limit function, or for 
idle trimming during the auto-rotation phase ("throttle 
AR").
The process of fi ne-tuning throttle and collective 
pitch, i.e. setting the motor power curve to match 
the collective blade pitch setting, is the most 
important aspect of setting up a model helicopter. 
The

mc-20

 HoTT software provides for independent 

confi guration of the throttle, collective pitch and torque 
compensation curves, in addition to the C1 control 
curve (»Channel 1 curve« menu, page 131). 
While these curves can be modeled using up to 
six points, fewer points are generally suffi cient. We 
recommend starting with three-point curves to begin 
with. This involves setting individual values for the 
center point and other (optional) reference points, 
and for the two end-points ("L", "low", and "H", "high") 
of the throttle/collective pitch stick: together, these 
defi ne the control curves. 
Before setting the throttle and collective pitch 
function, the rods of all servos should be 
mechanically pre-adjusted correctly according to the 
set-up instructions for the given helicopter.

The idle setting, whose detailed description begins 
on page 117, always takes place with the throttle 
limiter closed – normally with the trim wheel of the 
C1 function and only in special cases is the throttle 
limiter itself also utilized (as standard, the CTRL 6 
proportional rotary control). 
The programming of a corresponding value for the "L" 
point of the throttle curve acts to set the descent speed 
of the motor, without infl uencing the hover confi guration.
Here, for example, fl ight phase programming can be 
used to set different throttle curves. This increased 
system rotational speed below the hover point proves 
to be useful in certain circumstances, e. g. for fast, 
steep landing approaches with greatly reduced 
collective pitch, and for aerobatics.

The fi gure depicts a curve with a 
slightly changeable throttle setting 
below the hover point at the control 
center. 

Different throttle curves are programmed to be 
fl ight-phase dependent in order to achieve the given 
optimal adaptation to hovering fl ight as well as 
aerobatics:

Low system rotational speed with smooth, gentle 

•

control response and low noise when hovering
Higher rotor speed for aerobatics with motor power 

•

set close to the maximum. In this case, the throttle 
curve must also be adjusted in the hover range. 

Even though pitch and throttle curves can be set 
electronically over a wide range with the 

mc-20

 HoTT 

transmitter, all linkage in the model should already 
be mechanically pre-adjusted correctly according to 
the instructions for the given helicopter. Experienced 
helicopter pilots will be glad to help with this basic 
set-up.
The carburetor linkage must be set so that the throttle 
is just past the fully open setting with collective pitch 
set to maximum or, for electric helicopters, with the 
speed controller set to full. When the throttle limiter is 
closed, however, it must be possible to just close off 
the carburetor using the C1 trim wheel (rapid throttle 
setting of the "digital trim", see page 58 ), without the 
servo mechanically striking its end-stop. For electric 
helicopters, it must be possible to cut the electric 
motor's speed controller safely with the throttle limiter 
closed.
Take great care when confi guring these settings, 
by adjusting the control linkage as required and/or 
altering the linkage point on the servo or carburetor 
lever. Only then should the throttle servo's fi ne-tuning 
be electronically optimized.

With this basic set-up complete, the motor should 
be started in accordance with the motor operating 
instructions: idling can then be confi gured using 
the trim wheel of the throttle/collective pitch stick. 
The preset idle position will be displayed on the 
transmitter's basic display by a horizontal bar next 
to the C1 trim wheel position indicator. Refer to the 
description of digital trim on page 58 of this manual.