B737
MAINTENANCE MANUAL
EFFECTIVITY
Post ELT STC ST03081AT
23-24-00
PAGE 208
JAN 02/07
1) Activate the ELT, and allow to stabilize.
2)
The measured steady state current should not exceed 200 milliamps (mA).
When the 406.025 MHz module is on (generating the 406.025 MHz burst) the
current may exceed 3.5 Amps.
3) Turn the ELT “OFF”.
4) Disconnect the test harness 611-0024.
5) Reconnect the 2-pin module power harness.
6)
Reinstall the battery pack as described in step (4), “Replace/Reinstall Battery
Pack”.
(13)
Verification of Digital Message
NOTE: If checking the latitude/longitude, ensure that the aircraft’s navigation system and
ELT/NAV Interface are connected and powered on at least 30 seconds prior to
activation of the ELT.
(a) Activate the ELT and allow the ELT to transmit 15 to 30 seconds but not more than
40 seconds.
(b) The SARSAT Beacon Tester will receive the “test message” transmitted at turn off. If
the 406.025 MHz oscillator is not warmed up and stabilized, a ‘BAD FRAME’
message may occur, which could be construed as a problem when, in fact, the
message was generated because the oscillator had not warmed up.
(c)
If a ‘BAD FRAME’ is received, repeat the activation and turn off procedure again.
(d) Foe all testing of the 406 MHz output, only the ‘test message’ that is transmitted at
turn off is required to verify the ELT and ELT/NAV Interface function.
(e) The test message contains all the information contained in the actual distress
message except there is a special digital test prefix that tells the COSPAS/SARSAT
satellites to ignore the message.
NOTE: The initial display on the SARSAT Beacon Test Set can flag several problems prior to
advancing into the individual page displays described later.
1) If a “BAD FRAME” message appears after the 3
rd
or 4
th
transmit attempt, the
Beacon Test Set is not receiving transmit data. Verify that the SARSAT
Beacon Test Set is not receiving data. Verify that the SARSAT Beacon Test
Set does not have a low battery. Check the coax connection between the
ELT’s TPS connector and the SARSAT Beacon Test Set. Check the internal
ELT coax connection between the TPS connector and the 406.025 MHz
module. Finally, try a different battery pack.
2) If a “S’ TEST BAD or ‘DATA ERROR’ message appears, there is a problem
with the ELT (i.e. a programming problem or a problem with the transmitter
module) or the battery pack.
3) If there is no 406.025 MHz transmitter burst present, check the 3.0 Amp fuse
on the circuit board in the battery pack for an open condition. If the fuse is
good, there is most likely a problem with the 406.025 MHz module or its
interconnections.
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