Cessna 402C Pilot Operating Handbook page 239

~~L402C
SECTION 7
AIRPLANE & SYSTEMS DESCRIPTIONS
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Operation of the directional and horizon gyros can be checked during
taxiing
by
watching for an abnormally slow erection rate and erratic opera-
tion. After shutdown of the airplane on the ground, abnormal noise coming
from either gyro can indicate a near failure condition. Checking the
suction gage for proper vacuum and no failure buttons exposed will assure
proper gyro vacuum is available.
In flight. the directional gyro can be checked by flying a standard rate
turn and observing the directional gyro for a turning rate of 3 degrees per
second. Also the precession rate in straight and level flight should not
exceed 5 degrees in 10 minutes. The horizon gyro operation can be checked
by establishing a level flight attitude; the gyro should indicate wings
level within 1 degree. Initiate a 20-degree bank for a l80-degree turn.
then smoothly return to level flight; gyro should indicate wings level
within 3 degrees. Establish level flight at 150 KIAS; gyro should indicate
level airplane within I degree. Smoothly pitch airplane nose down 10
degrees, then return to level flight; gyro should indicate level flight
within 1 degree.
STALL WARNING SYSTEM
A stall warning system is required equipment which consists of a stall
warning transmitter vane located in the left outboard wing leading edge. a
flight deck warning horn and the necessary wiring to complete the system.
The stall warning horn will sound 5 to 10 KIAS above the stall in all
flight configurations. Proper operation of the warning system can be
checked duri ng prefl i ght in specti on by movi ng the sta11 wa rni ng vane; the
horn should sound. Condition of the stall warning vane heater should al so
be checked during preflight by actuating the stall and vent heat switch and
feeling the vane for heat. Full heat to the system is available only inl
fl ight. The heating circuits are wired through the landing gear shock
strut safety switch to provide lower heat during ground operation.
AVIONICS
AVIONICS INTERFERENCE
. . . - - - - - - - - N O T E - - - - - - - - - - ,
When tuned to a weak NAV signal, keying the COMM
transmitter may cause momentary interference within
the NAV receiver causing a NAV flag to appear.
Should circumstances warrant, ATC should be
requested to assign another COMM frequency.
AVIONICS MASTER SWITCHES
Two optional avionics master switches are provided with factory in-
stalled avionics. The master switch breaker labeled AVIONICS BUS is lo-
cated on the top forward section of the side console, see Figure 7-18.
This switch supplies power from the battery bus through a circuit breaker
located aft of the battery box to the individual avionics circuit breakers
and is used for all nonnal operations. An emergency power avionics bus
switch breaker labeled EMER POWER AVIONICS BUS is located in the lower
section of the side console and is protected by a red switch guard cover.
See Figure
7~18.
Thi s swi tch suppl ies power from the al ternator bus to the
individual avionics circuit breakers. The emergency power avionics bus
switch is recommended for use only when the avionics bus
swit~h.
associated
Wiring or battery circuits become inoperative.
1 November 1979
Revision 4 - 1 December 1983
7-35