Exploiting Full Butterfly Servo Travels - Multiplex COCKPIX SX Manuel D'utilisation

C SX
OCKPIT

14.11.6. Exploiting full Butterfly servo travels

(Offset for inboard / outboard flaps)
MIXER
Menu: (
If the Butterfly (crow) system is used as landing aid on
a four-flap wing, special requirements are placed on
the servo travels for the inboard and outboard pairs of
flaps (ailerons, camber-changing flaps).
Symmetrical control surface travels
The control surface lies at the neutral
position relative to the wing airfoil,
and moves through the same dis-
tance up and down. This is the de-
fault setting when you set up a new
model.
For the outboard flaps (ailerons)
this applies:
The up-AILERON travel must be
large (ca. 20°). 10° is a common
value for down-aileron (corres-
ponding to 50% differential). For
SPOILER (Butterfly) a large
travel is desirable, e.g. 40°. If the
ailerons are also used as cam-
ber-changing flaps (FLAP), the
additional up / down travel only
needs to be around -2° / 3°.
For the inboard flaps (camber-changing flaps) this
applies:
If the inboard flaps are set up to
follow the AILERON function,
an up-travel of 20° is a good
starting point. Often no travel is
set for down-aileron ("split"
mode). In order to
maximum braking effect for
SPOILER (Butterfly), the in-
board flaps should deflect down
as far as possible when the
spoilers are deployed, e.g. 60°.
This arrangement requires highly asymmetrical aileron
and flap travels: in one direction the control surface
travel should be as large as possible, in the other direc-
tion a much smaller travel is sufficient. If the control
surfaces are controlled starting from the servo centre-
point, part of the servo travel is always unused.
However, if you apply an Offset to both pairs of control
surfaces, the full servo travel can be exploited. This
also has a positive effect on any lost motion in the link-
age, the effective servo power and the shock loads on
the servo gearbox in a hard landing.
The next illustration shows in graphic form how the
inboard flaps are to move. Flaps require large down-
travel (landing setting, Butterfly), but small up-travel
(speed tasks).
The picture on the next page shows a cross-section
through the wing, and illustrates what we have said for
the camber-changing flaps.
) OFS AI and OFS F
obtain
Example for Flaps
Flap at neutral position,
servo offset by"Offset"
servo centre
100%
Flap up-deflection,
e.g. for AILERON function
-100%
Flap deflection increased by "Offset",
for Butterfly / Crow
40°
10°
SPOILER input to Flap
20°
This is the procedure if you wish to work with an
Offset
Example: camber-changing flap, four-flap glider:
1. Set the servo electrically to centre
Fit the servo output arm at right-angles to the case
2. Decide the required working range of the control
60°
surface
Example: the control surface (e.g. flap) has a
working range of +20° to -60°, starting from the
neutral position (flap in line with airfoil).
The centre of the flap's working range is therefore
located at -10°.
The pushrod should now be adjusted so that the
flap is at -10° when the servo is at its centre point.
Now adjust OFS F until the flap returns to the
3.
neutral point (flap in line with airfoil again).
If you wish to set up ailerons with an offset, use the
same procedure, but with the reverse travel ratio (more
up-aileron travel than down). The parameter to be ad-
justed in this case is OFS Q.
Page 46
Offset for FLAP
new servo neutral position
by OFS F
AILERON input to Flap
AI->F
+ 20°
50%
- 10°
-10° = electrical = elektr.
-150%
Servomitte
servo centre
- 60°