ACR&Artex G406-4 ELT - Manual (Page 27)

25-62-21
Page 27 of 86
JUL 31/12
ACR ELECTRONICS, INC / ARTEX PRODUCTS
DESCRIPTION, OPERATION, INSTALLATION AND MAINTENANCE MANUAL
G406-4 (453-5012)
DESCRIPTION AND OPERATION
TASK 25-62-21-870-801
1. Description
SUBTASK 25-62-21-870-001
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
(c) Country of registration and country code; plus
(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 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
(c) Alternate emergency contact.
(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 satellite processing of
distress signals from 121.5 and 243.0 MHz beacons.