Model menu
Collective pitch -> needle valve
Collective pitch -> tail rotor
F X - 4 0
19.7 COLLECTIVE PITCH -> NEEDLE VALVE MIXER
This function is used to program an automatic needle valve
adjustment which follows the movement of the collective pitch
stick. It enables you to set the optimum fuel mixture at the car-
burettor (by adjusting the needle valve) whenever the load on
the motor alters due to changes in the pitch angle of the rotor
blades. An acceleration option can also be programmed to
optimise this function.
With the ‘Helicopter’ type already selected, mark this option in
the Model menu. The screen display now looks like this:
The first step is to activate this mixer in the standard manner:
simply mark the Status field, and the label in the field changes
from ‘INA’ to ‘ON’ or ‘OFF’, according to the physical position
of the switch. Define a switch and its direction of operation in
the standard way, using the ‘Switch’ column. The default set-
ting is ‘NONE’, i.e. the mixer is always switched on. The
effects and method of setting the ‘Glob’ or ‘Sepa’ mode have
already been described; the function is programmed in the
appropriate switch field.
An acceleration function can be programmed in a separate
frame. This function is described in full in Section 19.3 on page
88. You can enter a separate percentage value (Rate) for each
mixer, for both maximum travels of the collective pitch stick
(Min. and Max.): mark the field and enter the values required
using the arrow buttons. The setting is displayed in the field as
a percentage value. It is also possible to enter a percentage
value in the ‘Damping’ field; this determines how long the
function is to remain active once the change in setting has
been carried out.
In the bottom line you can define a point for both sides which
represents the position from which the function is to take
effect: move the transmitter stick to the desired position, and
mark the associated field. The software stores the trigger value
and the field displays the position.
The mixer function is actually set up with the help of the asso-
ciated curve using the familiar method. First define the curve
type, then program the curve using the standard procedure:
the first step is to select the curve type, then enter the curve
points separately for the left side (Rate A) and the right side
(Rate B). The method of programming a mixer curve is exactly
as described in Section 17.2 on page 58; please refer back to
that section if you are not sure.
The screen shot below shows an example of a programmed
‘Collective pitch -> needle valve’ curve.
19.8
COLLECTIVE PITCH -> TAIL ROTOR MIXER
(REVOLUTION MIXER
)
The purpose of this function is to detect torque fluctuations at
the main rotor, caused by changes to the throttle or collective
pitch settings, and pass that information to a mixer which con-
trols the tail servo, so that the tail rotor always generates the
appropriate corrective torque, thereby more or less eliminating
unwanted moments around the vertical (yaw) axis. If this mixer
is set up accurately, it greatly eases the task of the tail rotor
gyro system. However, an incorrectly set mixer of this type
(also known as a Revo mixer) will interfere with the gyro’s pro-
per function. For this reason it is particularly important to set
up this mixer accurately. An acceleration function can be pro-
grammed to optimise this function.
If a modern gyro is installed, and operated in heading-hold /
AVCS mode, the revolution mixer must always be switched off.
With the ‘Helicopter’ model type already selected, mark the
Revolution mixer (Collective pitch -> tail rotor) in the Model
menu. The screen now looks like this:
The first step is to activate the mixer in the usual way: simply
mark the Status field, and the label in the field changes from
‘INA’ to ‘ON’. The effects and method of setting the ‘Glob’ or
‘Sepa’ mode have already been described; the function is pro-
grammed in the appropriate switch field.
An acceleration function can also be programmed in a sepa-
rate frame. This function is described in full in Section 19.3
(Acceleration) on page 88. You can enter a separate percen-
tage value (Rate) for both maximum deflections of the collec-
tive pitch stick (Min. and Max.): mark the field and enter the
values required using the arrow buttons. The setting is dis-
played in the field as a percentage value. You can also enter a
percentage value in the ‘Damping’ field to indicate a time; this
determines how long the function is to remain active once the
change in setting has been carried out. In the bottom line you
can define a point for both sides which represents the position
from which the function is to take effect: move the transmitter
stick to the desired position, and mark the associated field.
The software stores the trigger position, and displays it in the
field.
The mixer function is actually set up with the help of the asso-
ciated curve in the usual way: first define the curve type, then
enter the curve points separately for the left side (Rate A) and
the right side (Rate B). The method of programming a mixer
curve is exactly as described in Section 17.2 on page 58; refer
back to that section if you are not sure.
Please be extremely cautious when making these adjust-
ments, and carry out any changes in small steps. Check all the
settings very carefully before eventually moving on to very
careful test-flights. From a stable hover the helicopter should
exhibit no tendency to rotate around the vertical (yaw) axis
when you open the throttle or increase the collective pitch set-
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