Taws - Garmin G2000 Pilot's Manual

6.6 taWS

Do not use TAWS information for primary terrain avoidance. TAWS is intended only to enhance
WarninG:
situational awareness.
Government agencies provide data for the TAWS databases. Garmin accurately processes and cross-
note:
validates the data but cannot guarantee the accuracy and completeness of the data.
Terrain information is not available when the aircraft is outside of the installed terrain database
note:
coverage area.
The Terrain Awareness and Warning System (TAWS) is a software feature that provides the pilot with visual
annunciations and voice alerts for potential conflicts between the current flight path and surrounding terrain and
obstacles. The TAWS messages are advisory in nature only.
TAWS satisfies TSO-C151b Class B requirements for certification.
TAWS requires the following to operate properly:
• A valid terrain and obstacle database
• A valid 3-D GPS position solution
TAWS uses terrain and obstacle information from government sources. Terrain information is based on terrain
elevation information in a database that may contain inaccuracies. Individual obstructions may be shown if
available in the database. Garmin verifies the data, per TSO-C151b. However, the displayed information should
never be understood as being all-inclusive and data may be inaccurate.
TAWS uses information provided from the GPS receiver to provide a horizontal position and altitude. GPS
altitude is derived from satellite measurements. GPS altitude is then converted to the height above geodetic
sea level (GSL), which is the height above mean sea level (MSL) calculated geometrically. The system uses GSL
altitude for its alert calculations. GSL altitude accuracy is affected by satellite geometry, but is not subject to
variations in pressure and temperature that normally affect pressure altitude sensors. GSL altitude does not
require local altimeter settings to determine MSL altitude. It is a widely-used MSL altitude source. Therefore,
GSL altitude provides a highly accurate and reliable MSL altitude source to calculate terrain and obstacle alerts.
The TAWS terrain and obstacle databases are referenced to MSL. Using the GPS position and GSL altitude,
TAWS provides a 2-D picture of the surrounding terrain and obstacles relative to the position and altitude of the
aircraft. Furthermore, the system uses the GPS position and GSL altitude to calculate and "predict" the aircraft' s
flight path in relation to the surrounding terrain and obstacles. In this manner, TAWS can provide advanced alerts
of predicted dangerous terrain and obstacle conditions.
Baro-corrected altitude (or indicated altitude) is derived by adjusting the altimeter setting for local atmospheric
conditions. The most accurate baro-corrected altitude can be achieved by frequently updating the altimeter
setting to the nearest reporting station along the flight path. However, because actual atmospheric conditions
seldom match the standard conditions defined by the International Standard Atmosphere (ISA) model (where
pressure, temperature, and lapse rates have fixed values), it is common for the baro-corrected altitude (as read
from the altimeter) to differ from the GSL altitude.
190-01263-01 Rev. A
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Garmin G2000 Pilot's Guide for the Cessna T240
Hazard avoidance
411