Model menu
Aileron differential
F X - 4 0
18.1
AILERON DIFFERENTIAL
Differential aileron travel is often required on fixed-wing model
aircraft in order to compensate for the phenomenon known as
adverse yaw. When the aeroplane is turning, the outboard
wing moves through the air more quickly, which means that
the drag generated by the down-going aileron (on the outside
of the turn) is greater than that of the up-going aileron. The
result is a yawing moment which tends to turn the model’s
nose away from the turn, swinging the model around its verti-
cal axis.
The effect of aileron differential is to reduce the travel of the
down-going aileron relative to that of the up-going aileron, with
the aim of generating equal amounts of drag on both wing
panels. This eliminates the adverse yaw problem.
This function acts as a mixer for two separate aileron servos,
enabling you to adjust travels for ‘aileron up’ and ‘aileron
down’ individually for each aileron. One of the auxiliary trans-
mitter controls can be set up as a means of fine-tuning the
degree of differential.
A separate
servo must be
used for each
control surface.
The FX-40 soft-
ware allows
you to assign
transmitter
controls in any
way you like.
The diagram above shows a typical fixed-wing model with two
ailerons on each wing panel.
Mark the ‘Aileron diff.’ option in the Model menu. The screen
now looks like this:
In our example the programming procedure is described for a
model with ‘only’ two aileron servos. Nevertheless, if you need
to activate this option for a complex model glider with up to
four ailerons, the set-up procedure is more or less identical.
Please follow the programming procedure described below:
• Define the basic settings
In the ‘Glob’ field you can select ‘Sepa’ or ‘Glob’ modes;
the effect has already been described, and is set using the
standard method.
Press the ‘Master’ field in the top right corner of the screen
to move on to the AFR and D/R settings for the ailerons.
The screen now looks like this:
The first step is to set the display mode in the ‘Display’ field;
you can define individually whether the screen is to show all
the flight modes (All modes), the currently active mode
(Separate) or the ‘AFR’ and ‘D/R’ settings.
The ‘Speed’ frame is used for adjusting servo transit speed.
You can enter a speed separately for the ‘there’ and ‘back’
directions, and the adjustment range is 0 to 27 increments.
Please note: the higher the number, the more slowly the
servo moves. The maximum value (27 increments) corres-
ponds to a duration of nine seconds. The default setting is
always ‘0’. When you mark one of the fields ‘there’ or
‘back’, the arrow button fields appear at the right margin. It
is possible to make adjustments in steps of one or ten
increments. Pressing the ‘Reset’ button restores the default
setting.
Pressing the ‘D/R’ button field displays the current Dual
Rate settings. Dual Rate values can be set at this point, in
parallel with the programming facilities which are described
in Section 17.2 on page 57.
• Enter the differential travels
For the aileron servos (max. four) mark the appropriate
adjustment field for the left and right side. The arrow but-
tons are used to enter adjustments; note that you have to
move the stick to the right or left end-point in each case.
Adjustments can only be carried out for the side to which
the stick has been moved.
• Set up a curve
It is possible to program a curve for the effect of the aileron
differential function. A percentage value can be entered in
addition to your preferred curve type for each side (Rate A
and Rate B). The values are adjusted exactly as described
for programming the Dual Rate curves; please refer to this
in Section 17.2 on page 58.
65
No differential
50% differential
100% differential (split mode)
Aileron 1
Aileron 3
Aileron 4
Aileron 2
