TM 55-1520-228-10
or in straight and level flight. The warning flag, atti-
tude (ATT) and rate of turn pointer provide indication of
system malfunctions. W hen the gyro is being caged or
when 28 Vdc power is interrupted, the ATT flag will be
in full view. The rate of turn pointer will be biased out
of view when 28 Vdc is interrupted. The circuit is pow-
ered by 28 Vdc essential bus and protected by ATTD
HRZN and ATTN TURN circuit breakers. The rate-of-
turn pointer is driven by 115 VAC internal circuitry that
derives rate-of-turn from the output synchro transmitter
of the directional gyro magnetic compass.
2-65. TURN AND SLIP INDICATOR.
A. Theturnandslipindicator(figure 2-13) is controlled
by a direct current electrically actuated gyro. This in-
strument has a needle (turn indicator) and a ball (sli
p
indicator). Although needle and ball are combined in
one instrument and are normally read and inte rp rete d
together, each has its own specificfunctiona
nd ope r-
ates independently of the other. The ball indicates when
the helicopter is in directional balance either in a turn or
in straight and level flight. If the helicop
ter is yawing or
slipping, the ball will be off center. The needle indicates
in which direction and at what rate the helicopter is turn-
ing.
2-66. FREE AIR TEMPERATURE INDICATO
R.
Thebi-metalfreeairtemperatureindicator(figure 2-13
and figure 2-14) is in the windshield, and provides a di-
rect reading of the outside air tem
perature.
2-67. MAGNETIC COMPAS S .
The magnetic compass (figure 2-13 and figure 2-14)
is a standard, non-stabilized, magnetic type ins trument
mounted on a support which is at
tached to the right side
of the ca bin structure forwa rd of t he pilot. The compass
is used in conjunction with a compass correction card
that is locate d near the co
mpass. In aircraft with low re-
flective painted interior, the compass correction card will
be located in the front of the logbo ok.
2-68. VERTICAL SPEED INDICATOR.
The vertical speed indic
ator (figure 2-13 an d figure 2-14)
displays the helicopter ascent and descent speed in feet
per minute. the indicator is actuated by the rate of atmo-
spheric pressure change.
2-69.
C. CONUS NAVIGATION SYSTEM
(AN/ARN-123).
Refer to Chapter 3.
2-70. RADAR ALTIMETER (AN/APN-209).
Refer to Chapter 3.
2-71. RADAR WARNING SYSTEM.
Refer to Chapter 3.
2-72. MISCELLANEOUS INDICATORS.
Instruments and indicators that are independent or are
linkedwithmorethanonesystemaretheclockandmas-
ter caution and warning system (figure 2-12).
a. Clock. The clock (figure 2-13 and figure 2-14)
has a sweep-second pointer and a minute totalizer hand
to indicate elapsed time. The control knob in the upper
right corner of the case starts, stops, and retur
ns the
pointers to the 12 o’clock position when actuated.
b. Caution System. The caution system (figure
2-13 and figure 2-14) is a segment wording type, con-
sisting of a segment word warning CAUTI
ON panel
(figure 2-19) on the lower console and a remote MAS-
TER CAUTION segment on the instrument panel. The
purpose of the CAUTION system is to pr
ovide visual
indication suitable for day or night operation, that a fault
condition has occurred. In addition, a positive signal is
provided to illuminate the remo
te MASTER CAUTION
indicator. Each fault co ndition, as it occurs , is indicated
by
A., flashing of the lettering on the segment involved
and by a flashing of the MASTER C
AUTION indicator.
C., stea dy illumina tion of the lettering on the segment
involved and by a steady illumination of the MASTER
CAUTION indicator. A mome
ntary positioning of RE-
SET-TEST switch to RESET extinguishes the MAS TER
CAUTION light so that it will illuminate for the next fault
indication; also, the f
ault segment will be steadily ON.
Segments will remain lighted as long as the fault co n -
dition(s) exist. Momentarily pressing the RESET-TEST
sw
itch to TEST will che
ck if all caution lights
are operational. Testing of the system will not change
the existing fault conditions. The BRIGHT-DIM
2-46.2 Change 14
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