Garmin GNC 420AW Pilot's Manual

Also see for GDL 69: Pilot's guide addendum Pilot's guide addendum Activation Instructions Activation Instructions Pilot's guide addendum

Contents

Garmin GNC 420AW Pilot's Manual Manual pdf 67 page image

61Part FiveTerrain ProximityPart Five:Terrain Proximity InterfaceNOTE: Either the TERRAIN, TAWS (500W-series only),HTAWS, or Terrain Proximity functionality will be availablevia the Terrain page, depending on the installed hardwareand configuration. .IntroductionGarmin Terrain Proximity is an optional non-TSO-certified terrain awareness feature of the 400W/500Wseries available in helicopter configurations to increasesituational awareness and help reduce controlled flightinto terrain (CFIT). Terrain Proximity is available inthe Nav page group Terrain pages. Terrain Proximitydepicts nearby terrain and obstacles relative to the air-craft altitude, however it does not provide any alerts.Terrain Proximity uses information provided fromthe GPS receiver to provide a horizontal position andaltitude. GPS altitude is derived from satellite measure-ments. GPS altitude is converted to a Mean Sea Level(MSL)-based altitude (GPS-MSL altitude) and is usedto provide terrain coloring that depicts terrain eleva-tion relative to the aircraft. GPS-MSL altitude accuracyis affected by factors such as satellite geometry, but it isnot subject to variations in pressure and temperaturethat normally affect pressure altitude devices. GPS-MSLaltitude does not require local altimeter settings todetermine MSL altitude.Terrain Proximity utilizes terrain and obstacledatabases that are referenced to mean sea level (MSL).Using the GPS position and GPS-MSL altitude, TerrainProximity displays a 2-D picture of the surroundingterrain and obstacles relative to the position and alti-tude of the aircraft. In this manner, Terrain Proximityincreases awareness of the aircraft proximity to terrainand obstacles.Terrain Proximity requires the following to operateproperly:• The system must have a valid 3-D GPS positionsolution.• The system must have a valid terrain database.Displaying Terrain ProximityThe Terrain Proximity page is in the Map page group.1. Turn the large right knob to the Map func-tion.2. Then, the small right knob to the TerrainProximity page.Terrain Proximity Page190-00356-30 Rev H