SECTION 7
CESSNA
AIRPLANE & SYSTEMS DESCRIPTIONS
MODEL 172RG
Knowing the calibrated airspeed, read true airspeed on the ring opposite
the calibrated airspeed.
VERTICAL SPEED INDICATOR
The vertical speed indicator depicts airplane rate of climb or descent in
feet per minute. The pointer is actuated by atmospheric pressure changes
resulting from changes of altitude as supplied by the static source.
ALTIMETER
Airplane altitude is depicted by a barometric type altimeter. A knob
near the lower left portion of the indicator provides adjustment of the
instrument's barometric scale to the current altimeter setting.
VACUUM SYSTEM AND INSTRUMENTS
An engine-driven vacuum system (see figure 7-10) provides the
suction necessary to operate the attitude indicator and directional indica-
tor. The system consists of a vacuum pump mounted on the engine, a
vacuum relief valve and vacuum system air filter on the aft side of the
firewall below the instrument panel, instruments on the left side of the
instrument panel and a suction gage on the right side of the panel.
ATTITUDE INDICATOR
An attitude indicator is available and gives a visual indication of flight
attitude. Bank attitude is presented by a pointer at the top of the indicator
relative to the bank scale which has index marks at 10°, 20°, 30°, 60°, and 90°
either side of the center mark. Pitch and roll attitudes are presented by a
miniature airplane superimposed over a symbolic horizon area divided
into two sections by a white horizon bar. The upper "blue sky" area and the
lower "ground" area have arbitrary pitch reference lines useful for pitch
attitude control. A knob at the bottom of the instrument is provided for in-
flight adjustment of the miniature airplane to the horizon bar for a more
accurate flight attitude indication.
DIRECTIONAL INDICATOR
A directional indicator displays airplane heading on a compass card in
relation to a fixed simulated airplane image and index. The directional
indicator will precess slightly over a period of time. Therefore, the,
compass card should be set in accordance with the magnetic compass just
'
prior to takeoff, and occasionally re-adjusted on extended flights. A knob
on the lower left edge of the instrument is used to adjust the compass card
to correct for any precession.
7-38
1 July 1979
CESSNA
SECTION 7
MODEL 172RG
AIRPLANE & SYSTEMS DESCRIPTIONS
1 July 1979
7-39
