B737
MAINTENANCE MANUAL
EFFECTIVITY
Post ELT STC ST03081AT
23-24-00
PAGE 004
JAN 02/07
D.
Antenna
(1) The ELT system uses a blade type antenna. The antenna is installed on the exterior (top)
of the aircraft at the rear, in front of the vertical stabilizer. The antenna provides efficient
radiation at 121.5, 243 and 406 Mhz. Antenna Features:
(a) Transmitter to Antenna connection via single cable.
(b) Blade type antenna
(c) Triple frequency 121.5/243/406.025 MHz
(d) VSWR: 2.0:1 Max at 121.5/243 MHz 1.5:1 Max for 406.025 MHz
(e) Vertical polarization
(f) BNC connector
(g) Omnidirectional radiation pattern
3. Operation
A.
Operation
(1) One of the primary features of the C406-1 series ELT is its simplicity of operation. As long
as the ELT is locked into its mounting tray, it will activate in a crash. Neither the cockpit
switch nor the ELT unit switch can be positioned to prevent automatic activation once the
unit is mounted properly.
(2) It also is designed against human error and misuse in regards to automatic activation. The
unit activates only when securely mounted in its tray and has pins 5 & 8 jumpered. The
ELT cannot be accidentally activated by dropping , rough handling or during shipping.
(3) When the ELT is activated, the presence of the emergency swept tone and a flashing front
panel light indicates a normal functioning unit. The front panel light must immediately begin
to continuously flash upon ELT activation.
(4) Under normal operation the switch configuration on your panel is the down position,
reading ARM. The switch on the ELT unit will also be positioned down to read OFF. Should
an emergency arise to the degree that you want to manually activate your ELT, reverse
either switch so it is up (ON) position. Remember, that as long as the front panel and ELT
switches are in the ARM/OFF position the ELT will automatically activate on impact.
(5) If your ELT is activated, you will need to reset it. Do this by moving the front panel switch to
ON, then moving it back to ARM after approximately 1 second. You may also reset the ELT
at the unit itself by positioning the switch on the ELT up to ON, then back down to OFF
after approximately 1 second.
B.
Overall Functions
(1) The ELT unit is considered to be active “ACTIVE” or “INACTIVE”. When “INACTIVE”, the
unit lies in a state of rest and performs no functions. Taking the unit from the “INACTIVE”
to the “ACTIVE” state requires a positive switch transition from one of three sources:
(a) Panel Mounted Switch
(b) Unit Mounted Switch
(c) G-switch
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