Cessna 150M - Emergency Locator Transmitter.; Transmitter Life; Checkout Interval

16-75. EMERGENCY LOCATOR TRANSMITTER.
16-76. DESCRIPTION. The ELT is a self-contained,
solid state unit, having its own power supply, with an
externally mounted antenna. The C589510-0209 trans-
mitter is designed to transmit simultaneously on dual
emergency frequencies of 121. 5 and 243.0 Megahertz.
The C589510-0211 transmitter used for Canadian
registry, operates on 121. 5 only. The unit is mount-
ed in the tail cone, aft of the baggage curtain on the
right hand side. The transmitters are designed to
provide a broadcast tone that is audio modulated in a
swept manner over the range of 1600 to 300 Hz in a
distinct, easily recognizable distress signal for re-
ception by search and rescue personnel and others
monitoring the emergency frequencies. Power is
supplied to the transmitter by a battery-pack which
has the service life of the batteries placarded on the
batteries and also on the outside end of the transmit-
ter. ELT's thru early 1974 models, were equipped
with a battery-pack containing six magnesium "D"
size dry cell batteries wired in series. (See figure
16-15) Mid 1974 thru early 1975, ELT's are equipped
with a battery-pack containing four "in-line" lithium"
"D" size batteries wired in series. Early 1975 and
on ELT's are equipped with a battery-pack containing
four lithium "D" size batteries which are stacked in
two's (See figure 16-16). The ELT exhibits line of
sight transmission characteristics which correspond
approximately to 100 miles at a search altitude of
10,000 feet. When battery inspection and replacement
schedules are adhered to, the transmitter will broad-
cast an emergency signal at rated power (75 MW-
minimum), for a continuous period of time as listed
in the following table.
TRANSMITTER LIFE
TO 75 MILLIWATTS OUTPUT
6 Cell 4 Cell
Temperature
Magnesium Lithium
Battery Pack
Battery Pack
+130°F
89 hrs
115 hrs
+ 70°F
95 hrs 115 hrs
-
4°F
49 hrs 95 hrs
- 40°F
23 hrs
70 hrs
Battery-packs have a normal shelf life of five to ten
(5-10) years and must be replaced at 1/2 of normal
shelf life in accordance with TSO-C91. Cessna
specifies 3 years replacement of magnesium (6-cell)
battery-packs and 5 years replacement of lithium
(4-cell) battery packs.
16-77. OPERATION. A three position switch on the
forward end of the unit controls operation. PlaCing
the switch in the ON position will energize the unit
to start transmitting emergency signals. In the OFF
poSition, the unit is inoperative. PlaCing the switch
in the ARM position will set the unit to start trans-
mitting emergency signals only after the unit has
received a 5g (tolerances are +2g and -(Ig) impact
force, for a duration of 11-16 milliseconds.
/CAUTION\
Do not leave the emergency locator transmitter
in the ON position longer than 5 seconds or
you may activate downed aircraft procedures
by C. A. P., D. O. T. or F. A. A. personnel.
IWARNING'
Magnesium (6-cell) battery-packs (excluding
4
cell lithium battery-packs) after prolonged
continuous use (1 hour) in a sealed environ-
ment give off explosive gas. If your ELT
has operated for this time period or longer,
as a precautionary measure, loosen the
ELT cover screws, lift the cover to break
air tight seal and let stand for 15 minutes
before tightening screws. Keep sparks,
flames and lighted cigarettes away from
battery-pack.
NOTE
After relatively short periods of inactivation,
the magnesium (6-ceU) battery-pack develops
a coating over its anode which drastically
reduces self discharge and thereby gives
the cell an extremely long storage life.
This coating will exhibit a high resistance
to the flow of electric current when the
battery is first switched on. After a short
while (less than 15 seconds), the battery
current will completely dissolve this coating
and enable the battery to operate normally.
If this coating is present when your ELT is
activated, there may be a few seconds delay
before the transmitter reaches full power.
16-78. CHECKOUT INTERVAL:
100 HOURS.
a. Turn aircraft master switch ON.
b. Turn aircraft transceiver ON and set frequency
on receiver to 121. 5 MHz.
c.
Remove the ELT's antenna cable from the ELT
unit.
d. Place the ELT's function selector switch in the
ON position for 5 seconds or less. Immediately re-
place the ELT function selector switch in the ARM
position after testing ELT.
e. Test should be conducted only within the time
period made up of the first five minutes after any
hour.
/CAUTION\
Tests with the antenna connected should be
approved and confirmed by the nearest control
tower.
NOTE
Without
its antenna connected, the ELT will
produce sufficient signal to reach your receiver,
yet it will not disturb other communications
or damage output circuitry.
Change 3
16-31