Figure 2-1. Acceptable Field; Of-View - Garmin GNS 480 Installation Manaul

Installation Procedures
2.5.3.1 Determination of Acceptable Field-of-View
The FAA has determined that the acceptable field-of-view for TSO C146a installations is approximately ±
35° horizontally from the center of the attitude indicator (or centerline of the pilot's seat / yoke). The
acceptable vertical field-of-view includes the area from the top of the instrument panel to the portion of
the instrument panel that is immediately below the basic 'T' instruments. For IFR GPS operations, the
GNS 480 must be located within the acceptable field-of-view. Refer to Figure 2-1 and the steps below to
determine whether or not the GNS 480 is within the acceptable field-of-view:
1. Measure the horizontal distance from the centerline to the left or right edge of the GNS 480, as
appropriate.
2. If the GNS 480 is mounted to the right of the instruments, and the left edge of the GNS 480 is within
13.8 inches to the right of the centerline, and the bottom edge of the GNS 480 is in the acceptable
area, the GNS 480 is considered within the acceptable field-of-view.
3. If the GNS 480 is mounted to the left of the instruments, and the right edge of the GNS 480 is within
11.8 inches to the left of the centerline, and the bottom edge of the GNS 480 is in the acceptable area,
the GNS 480 is considered within the acceptable field-of-view.
4. If the GNS 480 does not meet the criteria for acceptable field-of-view as defined above, the installation
may only be approved for IFR operations under the AML if the location has been previously approved by
the FAA (ACO). Refer to Appendix E for a list of aircraft that do not meet the acceptable field-of-
view requirement above but have been evaluated by the FAA and determined to be acceptable.
upper limit
ACCEPTABLE
FIELD-OF-VIEW
AREA
NOTES:
1. FOR AIRCRAFT WITHOUT THE BASIC INSTRUMENT 'T' CONFIGURATION, THE CENTER OF THE PILOT'S YOKE
SHOULD BE USED TO DETERMINE THE CENTERLINE.
2. FOR AIRCRAFT WITHOUT THE BASIC INSTRUMENT 'T' CONFIGURATION, THE LOWER LIMIT OF THE
ACCEPTABLE FIELD-OF-VIEW SHOULD BE 3.25 INCHES BELOW THE BOTTOM OF THE LOWEST INSTRUMENT
TYPICALLY FOUND IN THE BASIC 'T' OR CDI, WHICHEVER IS LOWER.
3. FOR AIRCRAFT IN WHICH THE TYPE CERTIFICATED CDI OR HSI LOCATION IS BELOW THE BASIC 'T', THE
LOWER LIMIT OF THE ACCEPTABLE FIELD-OF-VIEW SHOULD BE THE BOTTOM OF THE CDI OR HSI.
2-6
Pilot's Instrument 'T'
lower limit
11.8 in
16.8 in
Figure 2-1. Acceptable Field-of-View
560-0982-01 Rev L
bottom edge of
GNS 480 must
be within this
area to be within
the acceptable
field-of-view
3.25 in
13.8 in
16.8 in
1
Instrument 'T' Centerline
GNS 480 (CNX80) Installation Manual
Glareshield
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