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in a hangar, a costly ground or airborne search is
avoided. In the case of an inadvertent 406 MHz ELT
activation, the owner can deactivate the 406 MHz
ELT. If the 406 MHz ELT equipped aircraft is being
flown, the RCC can quickly activate a search.
406 MHz ELTs permit the Cospas−Sarsat satellite
system to narrow the search area to a more confined
area compared to that of a 121.5 MHz or 243.0 MHz
ELT. 406 MHz ELTs also include a low−power
121.5 MHz homing transmitter to aid searchers in
finding the aircraft in the terminal search phase.
(c) Each analog ELT emits a distinctive
downward swept audio tone on 121.5 MHz and
243.0 MHz.
(d) If “armed” and when subject to crash−
generated forces, ELTs are designed to automatically
activate and continuously emit their respective
signals, analog or digital. The transmitters will
operate continuously for at least 48 hours over a wide
temperature range. A properly installed, maintained,
and functioning ELT can expedite search and rescue
2/19/04 AIM
Emergency Services Available to Pilots 6−2−3
operations and save lives if it survives the crash and
is activated.
(e) Pilots and their passengers should know
how to activate the aircraft’s ELT if manual activation
is required. They should also be able to verify the
aircraft’s ELT is functioning and transmitting an alert
after a crash or manual activation.
(f) Because of the large number of 121.5 MHz
ELT false alerts and the lack of a quick means of
verifying the actual status of an activated 121.5 MHz
or 243.0 MHz analog ELT through an owner
registration database, U.S. SAR forces do not
respond as quickly to initial 121.5/243.0 MHz ELT
alerts as the SAR forces do to 406 MHz ELT alerts.
Compared to the almost instantaneous detection of a
406 MHz ELT, SAR forces’ normal practice is to wait
for either a confirmation of a 121.5/243.0 MHz alert
by additional satellite passes or through confirmation
of an overdue aircraft or similar notification. In some
cases, this confirmation process can take hours. SAR
forces can initiate a response to 406 MHz alerts in
minutes compared to the potential delay of hours for
a 121.5/243.0 MHz ELT.
3. The Cospas−Sarsat system has announced the
termination of satellite monitoring and reception of
the 121.5 MHz and 243.0 MHz frequencies in 2009.
The Cospas−Sarsat system will continue to monitor
the 406 MHz frequency. What this means for pilots is
that after the termination date, those aircraft with only
121.5 MHz or 243.0 MHz ELT’s onboard will have
to depend upon either a nearby Air Traffic Control
facility receiving the alert signal or an overflying
aircraft monitoring 121.5 MHz or 243.0 MHz
detecting the alert. To ensure adequate monitoring of
these frequencies and timely alerts after 2009, all
airborne pilots should periodically monitor these
frequencies to try and detect an activated 121.5/243.0
MHz ELT.
b. Testing.
1. ELTs should be tested in accordance with the
manufacturer’s instructions, preferably in a shielded
or screened room or specially designed test container
to prevent the broadcast of signals which could
trigger a false alert.
2. When this cannot be done, aircraft
operational testing is authorized as follows:
(a) Analog 121.5/243 MHz ELTs should only
be tested during the first 5 minutes after any hour. If
operational tests must be made outside of this period,
they should be coordinated with the nearest FAA
Control Tower or FSS. Tests should be no longer than
three audible sweeps. If the antenna is removable, a
dummy load should be substituted during test
procedures.
(b) Digital 406 MHz ELTs should only be
tested in accordance with the unit’s manufacturer’s
instructions.
(c) Airborne tests are not authorized.
c. False Alarms.
1. Caution should be exercised to prevent the
inadvertent activation of ELTs in the air or while they
are being handled on the ground. Accidental or
unauthorized activation will generate an emergency
signal that cannot be distinguished from the real
thing, leading to expensive and frustrating searches.
A false ELT signal could also interfere with genuine
emergency transmissions and hinder or prevent the
timely location of crash sites. Frequent false alarms
could also result in complacency and decrease the
vigorous reaction that must be attached to all ELT
signals.
2. Numerous cases of inadvertent activation
have occurred as a result of aerobatics, hard landings,
　
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