Manual

25-62-10

Page 27 of 90

JUL 31/12

ACR ELECTRONICS, INC / ARTEX PRODUCTS

DESCRIPTION, OPERATION, INSTALLATION AND MAINTENANCE MANUAL

C406-1 (453-5002), C406-1HM (453-5003)

DESCRIPTION AND OPERATION

TASK 25-62-10-870-801

1. Description

SUBTASK 25-62-10-870-001

A. Functional Overview

(1) The ELT automatically activates during a crash and transmits the standard sweep tone on

121.5 and 243.0 MHz. Approximately every 50 seconds, for up to 520 milliseconds (long

message protocol), the 406 MHz transmitter turns on. During that time, an encoded digital

message is sent to the COSPAS-SARSAT Search and Rescue (SAR) satellite system.

(2) The information contained in the message includes:

(a) Serial number assigned to the ELT by the beacon manufacturer or the national beacon

registration authority, or

(b) Aircraft identification or registration number, and

(d) Position coordinates, when coupled with an ELT/NAV Interface (453-6500). Refer to the

ELT/NAV Interface Abbreviated Component Maintenance Manual (570-4602) for a

detailed discussion of the interaction between the ELT, ELT/NAV Interface, and aircraft

navigation system.

(3) The 406 MHz transmitter will operate for 24 hours and then shuts down automatically. The

121.5/243.0 transmitter will continue to operate until the batteries are exhausted, which is

typically at least 50 hours.

(4) The 406 MHz transmitter produces a much more accurate position, typically 3 kilometers as

compared with 15 to 20 kilometers for 121.5/243.0 MHz transmitters. When coupled to the

aircraft navigation system via the ELT/NAV Interface, the accuracy improves to approximately

100 meters.

(5) The ELT transmits a digital message that allows search and rescue authorities to contact the

owner/operator of the aircraft through information contained in a database. Information

contained in the database includes:

(a) Type of aircraft and aircraft registration number,

(b) Owner address and telephone number, and

(6) After the ELT is activated and the 406 MHz signal is detected by the SAR satellite system and

a position is calculated, the 121.5/243.0 MHz transmissions are used to home in on the crash

site.

NOTE

: Effective February 1, 2009, COSPAS-SARSAT has terminated the satellite processing

of distress signals from 121.5 and 243.0 MHz beacons.