400/500 Series Garmin Optional Displays
400/500 Series Garmin Optional Displays
400/500 Series Garmin Optional Displays
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PDA alerting is provided for both non-published visual approaches and published instrument<br />
approaches to airports. When an instrument approach is loaded in the active flight plan, the PDA<br />
function can provide a greater margin of safety by alerting for altitude deviations below minimum<br />
approach altitudes. Minimum altitudes are typically known for the segment prior to the final approach<br />
fix and for step-down fixes prior to the missed approach point. Minimum descent altitudes, decision<br />
altitudes, and decision heights are not known for instrument approaches. These minimum altitudes, as<br />
shown on instrument approach procedures, are published as MSL altitudes and flown by reference to<br />
barometric altitude provided on the altimeter.<br />
Non-standard atmospheric conditions, as described in the previous section, may result in differences<br />
between GPS-MSL altitude and Baro-Corrected altitude. These differences may reach a level that can<br />
trigger a PDA when flying the published minimum altitude as indicated on the altimeter.<br />
Operations in below-standard-temperature environments may require the pilot to compensate for the<br />
non-standard temperature by increasing the minimum altitude that is defined in the approach procedure<br />
for standard atmospheric conditions. Differences between GPS-MSL altitude and Baro-Corrected<br />
altitude typically increase as height above ground level increases due to non-standard atmospheric<br />
effects. In response to PDAs, the pilot should always ascertain the appropriate altitude is being flown in<br />
consideration of atmospheric conditions.<br />
Limitations<br />
The TAWS function displays altitudes of terrain and obstructions relative to the aircraft’s altitude and<br />
are advisory in nature only. Individual obstructions may be shown if available in the database. Not all<br />
obstructions may be available in the database and data may be inaccurate – do not maneuver or navigate<br />
to avoid obstacles using this information. Terrain information is based on terrain elevation data contained<br />
in a database, which may contain inaccuracies. Terrain information should be used as an aid to<br />
visual acquisition – do not use terrain information to navigate or maneuver to avoid terrain.<br />
Section 1<br />
Introduction<br />
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