Page 4-8
GTN 625/635/650 TSO Installation Manual
Rev. C
190-01004-02
4.10 Equipment Mounting
4.10.1
Rack Installation
Use the dimensions shown in Figure C-3 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.
Figure C-1 shows outline dimensions for the avionics rack for the various GTN units. Install the
rack in a rectangular 6.32‖ x 4.60‖ hole (or gap between units) in the instrument panel. 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. See Figure C-4 for more information. Ensure
that no screw heads or other obstructions prevent the unit from fully engaging in the rack
(see the ―Connector Engagement Test,‖ Section 6.3). Exercise caution when installing
the rack into the instrument panel. Deformation of the rack may make it difficult to
install and remove the GTN unit.
2.
Install the rack in the aircraft panel using ten #6-32 flat head screws and ten self-locking nuts.
The screws are inserted from the inside through the holes in the sides of the rack.
3.
To attach the backplate to the rack, align the backplate so that the backplate screw heads pass
through the keyed holes in the back of the rack.
4.
Slide the backplate to the right (viewing from cockpit) until it clicks into place. Secure the
backplate by tightening the four #4-40 screws.
4.10.2
GTN Unit Insertion and Removal
It may be necessary to insert the hex drive tool into the access hole and rotate the drive tool
counterclockwise until it completely stops in order to ensure correct position of the retention mechanism
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 3/8 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. Rotate
counterclockwise until the unit is forced out about 3/8 inches and the hex drive tool completely stops.
This will allow the unit to 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.
4.10.3
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 6.11.1 outlines the power-up
self-test sequence.
