User's Manual Part 1

CAS / Part No. 9000000

SYSTEM DESCRIPTION AND INSTALLATION MANUAL

34-43-20

15 Feb 2003

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CAS uses data provided by the Flight Management Computer, the GPS

receiver, and other aircraft subsystems to p redict a 3--D flight path based upon a

curve--fit extrapolation of the most recent position and velocity data received.

This predicted flight path is then compared with the internal terrain map of the

immediate area and an assessment of the potential threat of aircraft collision with

terrain is computed by the Collision Prediction and Alerting (CPA) algorithm.

(b) Conventional GPWS Modes of Operation.

Mode 1: Excessive rate of descent with respect to terrain

When the CPA mode is inoperative, this mode provides not only a reactive

short--term warning as defined in RTCA DO--161A, but also a reactive

medium -- term caution when the current flight path is descending toward the

terrain ahead of the aircraft at an excessive rate.

Mode 2: Excessive closure rate to terrain

When the CPA mode is not operative, this mode provides a reactive

short--term warning as defined in RTCA DO--161A when the current flight

path and the terrain ahead of the aircraft are closing at an excessive rate.

Mode 3: Excessive altitude loss after take--off

CAS meets the requirement for Mode 3 alerts as defined in RTCA

DO -- 161A. This mode provides an alert when there is a loss of altitude after

take-- off or during a missed approach. The mode uses the radar altimeter to

determine proximity to the ground and the barometric altimeter to determine

altitude loss. If an excessive loss of altitude occurs after take-- o ff, a warning

is issued.

Mode 4: Incorrect aircraft configuration with regard to terrain

CAS meets the requirement for Mode 4 alerts as defined in RTCA

DO --161A. Mode 4 usually applies during the landing phase of flight and

results in the annunciation of an alert in the event of insufficient terrain

clearance when the aircraft is not in the proper landing configuration. Mode

4 consists of the following two submodes:

• Mode 4A, when the landing gear is up

• Mode 4B, when the landing gear is down, but the flaps are not in landing

configuration.

Mode 5: Excessive glide path deviation

CAS meets the requirement for Mode 5 alerts as defined in RTCA

DO --161A. Mode 5 applies in the event of an excessive descent below the

instrument glide path when making a front-- course approach with the gear

down. In a back--course landing configuration, Mode 5 is automatically

inhibited.