Textron Cessna 172S Skyhawk SP, Information Manual

Page: 198 / 491

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>CESSNA
MODEL,172S
SECTION 7
. AIRPLANE & SYSTEMSDESCRIPTION"
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LOW VOLTAGE ANNUNCIATION
.... The low 'voltage warning annunciator.is ....incorporated in' thel
annunciator. panel and activates when voltage .falls below 24.5 volts.
If low.voltage is detected; the red .annunciation VOL 1S will flash for
approximately 10 ..seconds before illuminating' steadily. The pilot
cannot turn off the annunciator.
In the event an overvoltage condition occurs, the alternator
control unit automatically opens. the AL T FLD circuit breaker)
removing alternator field current 'and shutting off the aiternator.
Thel
battery will then supply system current as shown bya discharge
rate .. on' the. a'mmeter. Und.er-lhese conditions; depending on
electrical system load, the low voltage, warning annunciator' will
illuminate when' system voitagedrops below normal. The alternator .
control unit may be reset by resetting the, circuit brea,ker. If the
10~
voltage warning. annunciator extinguish'es, normal .. alternato
. charging has' resumed; however, if the annunciator illuminate
again, a malfunction has occurred, and the. flight .should b
terminated as soon as practicable.' .' . ..
NOTE
Iliuminatio'n of the low' voltage annunciator and' ammeter
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discharge indications may occur during low RPM conditions
with an electrical load on the system; such as during a low
RPM taxi. Under these conditions, the light will go out at
higher RPM. .
CIRCUIT BREAKERS AND FUSES
All circuit breakers inside the airplane are of the "push to reset"
or "switch/breaker" type. The power distribution module uses spade
type (automotive style) fuses and one glass type fuse (controlling
the clock).
Spare fuses for the power distribution module are located inside
the moduie. If one of the spare fuses is used, a replacement spare
should be obtained and reinstalled before the nex1 flight.
Revision 4
7-35