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We do not know all we would like to know about RFI, but we do know that the signal kill
wiring discussed in the previous paragraph is unnecessary in some cases. If you are using
shielded wiring in a metal airplane, RFI probably will not be a problem, and it may not be
a problem if you have shielded wiring in a composite airplane. But a composite airplane
with unshielded wiring usually needs the signal kill circuitry.
AUTOPILOT OUTPUT PINS ON NAV RECEIVERS
Your navigation receiver should have two output signal terminals to be used for driving
an autopilot or a CDI. Usually they are labeled '+ Left' and '+ Right', and they are to be
connected to the corresponding AP-1 terminals. If the labeling is ambiguous, as it is on at
least one fairly popular radio, just connect both wires without worrying about polarity
and check it out in flight test.
Many of the hand-held GPS or LORAN receivers, and a few of the panel mounted units,
have digital autopilot outputs that are not compatible with the analog (varying dc voltage)
signal required by the Navaid autopilot. If you have not yet bought your navigation
equipment, please check with the manufacturer—your receiver (GPS, LORAN, or VOR)
should be able to drive an external CDI, and this same signal is used to drive the
autopilot. If you are already driving an external CDI, just put the autopilot in parallel at
the same terminals.
MOMENTARY DISCONNECT SWITCH
In addition to the wiring shown in Fig. 3, you may wish to add a momentary pushbutton
switch in series with the servo power line. This switch would be located on or quite near
the stick, and it would disconnect the servo as long as the button is depressed. A lighted,
round switch that can mount in a 0.43 inch diameter hole is available (at the time of this
writing) from Mouser Electronics, phone (800) 346-6873. Use the two switch terminals
(of three) that are normally closed to interrupt the servo power wire.
Cap Color
Part No. Price
Red
10PL031
$11.08
Yellow
10PL033
$11.08
Green
10PL036
$11.08
Momentary Pushbutton Switch Options
Table 2
Summary of Contents for AP-1
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