Part Four Taws Interface; Section 1: Introduction; Overview; Operating Criteria - Garmin 400 Series Pilot's Manual Addendum

Section 1: Introduction

Overview

Garmin' s Terrain Awareness Warning System (TAWS) is an optional feature for the GPS 500 and
GNS 530/530A to increase situational awareness and aid in reducing controlled flight into terrain (CFIT)
(Figure 1-1). Garmin TAWS satisfies TSO-C151b Class B requirements for certification. Class B TAWS is
required for all Part 91 aircraft operations with 6 or more passenger seats and for Part 135 turbine aircraft
operations with 6 to 9 passenger seats (FAR Parts 91.223, 135.154).

Operating Criteria

Garmin TAWS requires the following to operate properly:
• The system must have a valid 3D GPS position solution
• The system must have a valid terrain/obstacle database

GPS Position and GPS-MSL Altitude

Garmin TAWS uses information provided from the 500 Series GPS receiver to provide a horizontal
position and altitude. GPS altitude is derived from satellite measurements. GPS altitude is converted to a
Mean Sea Level (MSL)-based altitude (GPS-MSL Altitude) and is used to determine TAWS alerts. GPS-
MSL Altitude accuracy is affected by factors such as satellite geometry, but is not subject to variations
in pressure and temperature that normally affect pressure altitude devices. GPS-MSL Altitude does not
require local altimeter settings to determine MSL Altitude. Therefore GPS altitude provides a highly
accurate and reliable MSL altitude source to calculate terrain and obstacle alerts.
PART FOUR
TAWS INTERFACE
Section 1
Introduction
Figure 1-1: Garmin TAWS satisfies TSO-C151b Class B
requirements for certification
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