Garmin GNC 420AW, Руководство по установке

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400W Series Installation Manual Page 2-7
190-00356-02 Rev. G
2.5 Mounting Considerations
The 400W 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 400W Series unit. The
location should be such that the 400W 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 400W 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 400W 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 400W Series unit), the source selection annunciation
displayed on the 400W 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 400W 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
400W Series unit display is within this area, then no external GPS navigation annunciations are required.
The 400W 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 400W 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
400W Series unit is installed between
±
30° and
±
35°, at a minimum, source selection annunciation must
be installed. See Figure 2-3.
2.5.1.1 Source Selection Annunciation
Use the steps below to determine whether or not the integrated source selection annunciation displayed on
the 400W Series unit to be installed is within the acceptable field-of-view (see Figure 2-2):