Mounting Considerations - Garmin GNS 530W Installation Manual

2.5 Mounting Considerations

The 500W Series unit is designed to mount in the avionics stack in the aircraft instrument panel within
view and reach of the pilot. The primary unit location should minimize pilot head movement when
transitioning between looking outside of the cockpit and viewing/operating the GPS 500W/GNS 530W.
The location should be such that the 500W Series unit is not blocked by the glare shield on top, or by the
throttles, control yoke, etc. on the bottom.
For VFR-only installations, the 500W Series unit must be mounted in the aircraft manufacturer's
approved location or other FAA approved location (see Figure 2-2). No CDI/HSI interface is required
but if provided, proper source selection annunciation must be used.
In accordance with AC 20-138A, for IFR GPS installations the 500W Series unit must be mounted in the
aircraft manufacturer's approved location or other FAA approved location, and the required CDI/HSI
must be mounted in the primary field of view. CDI/HSI navigation source selection annunciation must be
on or near the affected display and any additional annunciations must be mounted within the normal
field-of-view.
An FAA issue paper was written to clarify the TSO-C146a annunciation requirement of "on or near the
affected display". This issue paper said, in order to preclude the need for external source selection
annunciations (i.e. using the annunciation within the 500W Series unit), the source selection
annunciation displayed on the 500W Series unit must be within 13.856 inches of pilot view centerline. If
the CDI is to the left or right of centerline, it must favor the same side as the 500W Series unit placement
(i.e. typically the radio stack is on the right of the pilot's view centerline, so the CDI should be on the
right side of the basic primary flight instruments). A CDI/HSI with a built-in annunciation may also be
used in lieu of a separate external annunciator to satisfy the source selection annunciation requirement.
In addition, any required GPS navigation annunciations must be within 16.805 inches of the pilot view
centerline. If the 500W Series unit display is within this area, then no external GPS navigation
annunciations are required.
The 500W Series unit, as a redundant or secondary TSO-C146a certified navigation device, may be
installed outside the acceptable view parameters if the unit is used as a backup system. Example: To the
right of a center radio stack, when two columns of avionics are available. This places the unit too far
from the pilot's normal scan. As such, IFR flights may not originate or be predicated on this unit unless
the primary system has failed.
2.5.1 Determination of Acceptable Field-of-View
The FAA has determined that the acceptable field-of-view for TSO C146a annunciations related to
navigation source selection is approximately ±30° horizontally from the center of the attitude indicator
(or centerline of the pilot's seat/yoke), and that the acceptable field-of-view for TSO C146a
annunciations related to GPS navigation data is approximately ±35° horizontally from the center of the
attitude indicator. These angles are based on the closest panel distance of 24 inches resulting in a
measured offset from the attitude indicator of 13.856 inches and 16.805 inches respectively.
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. An example of the viewing
area based on the attitude indicator in an aircraft with basic "T" instruments is depicted in Figure 2-2.
For an IFR-approved GPS installation, the 500W Series unit must be located within the ±35° horizontal
acceptable field-of-view or source selection and GPS annunciations are required to be installed. If the
500W Series unit is installed between ±30° and ±35°, at a minimum, source selection annunciation must
be installed. See Figure 2-3.
500W Series Installation Manual Page 2-7
190-00357-02 Rev. D