ARTEX PRODUCTS / ACR ELECTRONICS, INC
DESCRIPTION, OPERATION, INSTALLATION AND MAINTENANCE MANUAL
ME406 (453-6603), ME406HM (453-6604)
Page 18 of 72
Mar 19/15
25-62-30
DESCRIPTION AND OPERATION
TASK 25-62-30-870-801
1.
Description
SUBTASK 25-62-30-870-001
A.
Functional Overview
1)
The ELT automatically activates during a crash and transmits the standard sweep tone on 121.5 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 a navigation interface device, which receives position
data from the aircraft navigation system and transmits it to the ELT.
3)
The 406 MHz transmitter will operate for 24 hours and then shuts down automatically. The 121.5 MHz
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 MHz transmitters. When coupled to the aircraft navigation system via
a navigation 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 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 MHz beacons.
7)
Aircraft communications transceivers are not capable of receiving 406 MHz transmissions; therefore, the
only methods of monitoring the ELT are:
a)
The blinking cockpit remote switch LED,
b)
The buzzer, or
c)
121.5 MHz transmissions, which can be monitored using the aircraft communications
transceiver or an AM radio tuned to 121.5 MHz.
