FUTABA GY502 Instruction Manual page 31

Re-reading method
In this case, quickly switch (interval of within 1
second) the transmitter remote gain switch between the
Normal and AVCS sides at least three times and
switch the AVCS side at the neutral trim position set in
the Normal mode. This memorizes the new rudder
neutral position in the GY502.
When the transmitter has a function that allows trim
setting for each flight condition, such as the T9Z, the
AVCS mode trim position is fixed and this operation is
unnecessary.
Never use the transmitter rudder trim in the AVCS mode.
When the rudder is trimmed during flight, the neutral position will
change.
When using the GY502 in the AVCS mode, set revolution mixing
to OFF.
When the rudder neutral position was changed by the linkage,
the rudder neutral position in the AVCS mode must always be
re-read before use.
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ATA ETTING
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