GTN 725/750 TSO Installation Manual
Page 3-7
190-01007-02
Rev. A
3.9 Equipment
Mounting
3.9.1 Rack
Installation
Use the dimensions shown in
TBD
to prepare the mounting holes for the GTN unit. You may also use the
GTN unit mounting rack itself as a template for drilling the mounting holes.
1.
The back plate of the rack may optionally be removed for ease of mounting in the aircraft panel.
To do so, remove the two #4-40 screws, tilt the back plate away from the tray, and then slide the
back plate to the side.
2.
TBD
shows outline dimensions for the aviation rack for the various GTN units. Install the rack in
a rectangular 6.320” x 4.600” hole (or gap between units) in the instrument panel (see
TBD
). The
lower-front lip of the rack should be flush with, or extend slightly beyond, the finished aircraft
panel.
NOTE
If the front lip of the mounting rack is behind the surface of the aircraft panel, the
GTN unit connectors may not fully engage.
Make sure that no screw heads or other obstructions prevent the unit from fully engaging
in the rack (see the “Connector Engagement Test,” Section 5.3). Exercise caution when
installing the rack into the instrument panel. The rack is designed to facilitate removal of
the GTN unit for use in Demo Mode outside the aircraft. Deformation of the rack may
make it difficult to install and remove the GTN unit.
3.
Install the rack in the aircraft panel using six #6-32 flat head screws and six self-locking nuts.
The screws are inserted from the inside through the holes in the sides of the rack.
4.
If the back plate was previously removed (see Step 1), replace the back plate by positioning the
tabs on the back plate in the slots of the left side of the rack (viewing it from the cockpit) and
attaching it by replacing the two #4-40 screws.
3.9.2
GTN Unit Insertion and Removal
It may be necessary to insert the hex drive tool into the access hole and rotate the mechanism 90°
counterclockwise to insure correct position prior to placing the unit in the rack. The GTN unit is installed
in the rack by sliding it straight in until it stops, about 1 inch short of the final position. A 3/32-inch hex
drive tool is then inserted into the access hole at the bottom of the unit face. Rotate the hex tool clockwise
while pressing on the left side of the bezel until the unit is firmly seated in the rack.
To remove the unit from the rack, insert the hex drive tool into the access hole on the unit face and rotate
counterclockwise until the unit is forced out about 3/8 inches and can be freely pulled from the rack.
Be sure not to over tighten the unit into the rack. The application of hex drive tool torque exceeding
15 in-lbs can damage the locking mechanism.
3.9.3 Unit
Replacement
Whenever the GTN unit is removed or reinstalled, verify that the unit power-up self-test sequence is
successfully completed and no failure messages are annunciated. Section
TBD
outlines the power-up self-
test sequence.
Summary of Contents for GTN 725
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