TruTrak AFS Pilot User Manual

AFS Pilot Series Autopilots

Installation/User Manual

Rev C

TRUTRAK FLIGHT SYSTEMS

1500 S. Old Missouri Road

Springdale, AR 72764

POSTAL SERVICE ADDRESS

Springdale, AR 72765-0189

Ph: 479-751-0250 Fax: [phone]

www.trutrakap.com

P.O. Box 189

INSTALLATION/USER MANUAL

Revision

Date

Description

Page #

A

11/04/2010

Initial Release

B

10/18/2011

Added ground power up recommendation

4 C 2/26/2014

Updated schematic for G board change

6

For

AFS Pilot Series Autopilots

TABLE OF CONTENTS

Mechanical Considerations ..................................................................................................................................................................... 4

Pitot / Static Connections ........................................................................................................................................................................ 5

RFI / EMI Considerations ........................................................................................................................................................................ 5

Ground Checkout ......................................................................................................................................................................................... 6

First Flight ...................................................................................................................................................................................................... 3

Electrical Pin-out ......................................................................................................................................................................................... 5

Wiring Diagram............................................................................................................................................................................................ 6

Block Diagram .............................................................................................................................................................................................. 7

AFS Pilot Operation .................................................................................................................................................................................... 8

Trutrak Warranty Description ........................................................................................................................................................... 12

RETURN MERCHANDISE POLICY AND PROCEDURE ........................................................................................................... 13

Mechanical Considerations

The installation information in this section is extremely important and must be clearly
understood by the installer. Improper servo installation or failure to observe and
diagnose installation problems prior to flight can result in extremely serious
consequences, including loss of ability to control the aircraft. If there are any
questions on the part of the installer it is mandatory to resolve these questions prior to
flight of the aircraft.

Most modern experimental aircraft use push-pull tubes to drive the primary controls. These tubes generally have a

total travel of 3” or less; therefore, it is best to connect the autopilot servo to the primary control by the same method.

This connection consists of an arm on the servo connected by a push-pull rod to the primary control. Rod-end bearings
are required on each end of the push-pull rod.

The servo arm must not rotate even near to the point called OVER CENTER, the point at which the
primary aircraft control would lock up. Some aircrafts mechanical primary control installations will not
allow this to occur and do not need the servo stops.

This is a condition that would result from the servo being back driven when the pilot operates the controls,
or from the servo itself driving the controls to a stop. To protect against this mechanical stops are supplied
with the servos. These stops are drilled so that they can be mounted at different angles as required (18
intervals).

In addition to the proper use of the stop it is important to know the amount of travel on the primary

control that the servo can handle. With the push rod connected to the outermost hole (1 ½”) the travel on
the primary cannot exceed 2 ½”, the intermediate hole 2 1/16”, and the inner hole 1 5/8”.

It is important to note that at the neutral point of the control the SERVO ARM must be PERPENDICULAR to
the push rod, and that the stop must be mounted so as to limit travel as near as possible to equal amounts
in both directions. In certain factory-designed installations there may be well-proven exceptions.

There will be installations in which space does not permit the use of the stop. When this is done the aircraft’s primary

control stops must be positive and care must be taken to be sure that at the neutral point the servo arm is
perpendicular to the push rod, and that the travel limits of the servo arm are not exceeded.

There are installations in which the travel of the push-pull tube exceeds the allowable 2 ½”. For such installations, the
drive can be applied to a bell crank at a radius point that moves the desired 2 ½” of maximum allowed travel in the
outermost hole of the arm.

When there is no way to have a drive point of less than 2 ½” or when the primary control is cable-driven it is necessary
to use the capstan-cable servo drive. When this is done the servo should be mounted so that the 1/16” diameter cable

which wraps around the capstan when extended parallel to the primary cable is approximately 3/16” from the primary
cable. If the primary control travel does not exceed 5” the cable locking pin will be 180 away from the point at which

the cable leaves the capstan. When the primary control is at the neutral point this means the total cable wrap around
the capstan is 360 . If the primary control travel is greater than 5” the cable wrap is 720 and the pin is adjacent to the
output point when the primary control is at the neutral point.

The cable clamps, when properly installed, will not slip, but it is desirable to NICO press or swedge a fitting on to the
cable so as to provide added assurance that the cable will not become slack. If the bridle cable is not sufficiently tight
there will be lost motion in the autopilot drive. This will result in hunting (oscillation).

TruTrak Flight Systems 4 AFS Pilot Installation/User Manual
October 2011 Rev B

PROGRAMMER INSTALLATION

Mounting Considerations

The AFS Pilot programmer unit is designed to mount in the aircraft instrument panel. Maximum recommended viewing
angle should be no more than 20 deg. The maximum mounting angle the programmer can accommodate is 10 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.

TruTrak Flight Systems 5 AFS Pilot Installation/User Manual
October 2011 Rev B