TruTrak Digiflight II Instal Manual - Manual (Page 4)

TruTrak Flight System 2 DigiFlight II Series Auto Pilot Installation Manual
December 2009 8300-008 Rev D
PROGRAMMER INSTALLATION
Mounting Considerations
The DII programmer unit is designed to mount in the aircraft instrument panel within view and reach of the pilot. Maximum
recommended viewing angle should be no more than 20 deg
. The maximum mounting angle the DII can accommodate is 12
degrees longitudinal axis and 0 degrees lateral axis. The primary unit location should minimize pilot head movement when
transitioning between looking outside of the cockpit and viewing/operating the programmer unit. The location should be such
that the programmer unit is not blocked by the glare shield on top, or by the throttles, control yoke, etc. on the bottom. Use
aircraft installation standards for mounting and support of the programmer.
Wiring Considerations
Use AWG #24 or larger wire for all connections unless otherwise specified. The standard solder pin contacts supplied in the
connector kit are compatible with up to AWG #18 wire. In cases where some installations have more than one component
sharing a common circuit breaker, sizing and wire gauge is based on, length of wiring and current draw on units. In these cases,
a larger gauge wire such as AWG #20 may be needed for power connections. Do not attach any wires to the outside of the
programmer or route high current wires within six (6) inch of the programmer. Ensure that routing of the wiring is not exposed
to sources of heat, RF or EMI interference. Check that there is ample space for the cabling and mating connectors. Avoid
sharp bends in cabling and routing near aircraft control cables. Do not route the COM antenna coax near any autopilot
components.
Pitot and Static Connections
All multi-servo TruTrak autopilots require connections to the pitot and static lines. The preferred method of this connection
would be tee fittings near the aircraft’s altimeter. The static line for the autopilot requires due care in its construction, as
excessive lag or insufficient static orifices can cause the autopilot to oscillate (hunt) in pitch. Although there is compensation
within the autopilot sufficient to handle moderate amounts of lag, the importance of a good static port and line cannot be
overstated. In some cases problems can be caused by having a large number of devices (including the autopilot) connected to a
single, insufficient, static port. In other cases, the static line itself is adequate but there are one or more devices connected to the
same line, one of which has a large static reservoir. A simple remedy for this problem if it occurs is a tee-fitting near the static
port, and a dedicated line to the autopilot only. Obviously, an insufficiently-large orifice coupled with large static reservoirs
can aggravate the problems associated with lag.
RFI/EMI considerations
The autopilot programmer is shielded and does not generate any appreciable level of electromagnetic interference. Moreover,
the servo lines (except for power and ground) are low-current and cannot contribute to RF interference. The servo power and
ground lines do have switching currents through them, but so long as there are no parallel runs of servo power and ground lines
with such things as poorly-shielded antenna lines or strobe light power lines, there is no need to shield the servo harnesses.
The autopilot itself has been internally protected from RF interference and has been tested under fairly extreme conditions,
such as close proximity to transmitting antennas. However, it is always good practice to insure that such antennas are properly
shielded and not routed directly over or under sensitive panel-mounted electronic equipment. Most problems in this area are the
result of improper RF shielding on transmitting antennas, microphone cables, and the like. The most sensitive input to the
autopilot is the Control Wheel Switch input. This line should not be routed in parallel with transmitting antennas or other
sources of known RF interference. If necessary, it can be shielded with the shield connection to pin 13 of the autopilot
connector.