27 General Section
Fail Safe
Fail Safe is available only when SPCM has been
selected as the Modulation Type in the SYSTEM
Menu. The receiver must be of the PCM variety, as Fail
Safe does not function in the PPM/FM mode.
When interference occurs on the frequency of
operation, PCM receivers do not pass the interference
on to the servos. Instead, the receiver commands the
servos to either hold their last good position (HOLD) or
to move to a pre-determined position (FAIL SAFE).
Both options exist for each channel and the settings are
adjustable in the Fail Safe function.
Many experienced pilots designate all channels as
HOLD, except for the throttle—it is commanded to
assume a Fail Safe position that corresponds to idle. In
this configuration the aircraft will continue to do
whatever it was doing before the interference occurred,
except the throttle will reduce to idle. The servos will
continue to hold their last position and the throttle will
remain at idle until the interference subsides, at which
time normal operation is resumed.
More often than not, the pilot will not realize the system
went into Fail Safe except for hearing the throttle
momentarily reduce RPM. This is also a good
configuration if interference is encountered while the
aircraft is on the ground because the throttle reduces to
idle, reducing the chances of the aircraft careening out
of control at a higher throttle setting. In the event that
the interference does not subside and the system
remains in Fail Safe, it is better for the aircraft to crash
with the engine at idle than at a higher throttle setting.
1. Run the engine in the aircraft and adjust the throttle
stick/travel and trim so the engine has a dependable
idle—perhaps a click or 2 above low idle. Leave the
throttle and trim in these positions.
2. Access the Fail Safe function by highlighting and
selecting Fail Safe in the FUNC.LIST.
3. Highlight and select THR, moving its indicator from
the HOLD position to the F.S. (Fail Safe) position.
This instructs the Fail Safe function to move the
throttle servo to a pre-determined position when the
receiver detects interference.
4. Press the CLR button next to MEMO to the left of the
display. This memorizes the current position of all
channels that are set to F.S. - in this case the throttle
which should be at idle. Whenever the RX detects
interference it will move the throttle to this position.
The remainder of the servos will hold their last good
position.
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