Airspeed Indicator; Rate-Of-Climb Indicator; Altimeter; Vacuum System And Instruments - Cessna 150 AEROBAT A150M Pilot Operating Handbook

SECTION 7
AIRPLANE & SYSTEMS DESCRIPTIONS
CESSNA
MODEL Al50M
A heated pitot system may be installed and consists of a heating ele-
ment in the pitot tube, a rocker-type switch labeled PITOT HT on the low-
er left side of the instrument panel, a 10-amp circuit breaker under the
engine controls on the instrument panel, and associated wiring. When the
pitot heat switch is turned on, the element in the pitot tube is heated elec-
trically to maintain proper operation in possible icing conditions. Pitot
heat should be used only as required.
AIRSPEED INDICATOR
The airspeed indicator is calibrated in knots and miles per hour.
Limitation and range markings include the white arc {44 to 85 knots),
green arc {50 to 123 knots), yellow arc (123 to 164 knots), and a red
line {164 knots).
If
a true airspeed indicator is installed, it is equipped with a rotata-
ble ring which works in conjunction with the airspeed indicator dial in
a manner similar to the operation of a flight computer. To operate the
indicator, first rotate the ring until pressure altitude is aligned with
outside air temperature in degrees Fahrenheit. Pressure altitude
should not be confused with indicated altitude. To obtain pressure
altitude, momentarily set the barometric scale on the altimeter to 29.92
and read pressure altitude on the altimeter. Be sure to return the al-
timeter barometric scale to the original barometric setting after pres-
sure altitude has been obtained. Having set the ring to correct for
altitude and temperature, then read the airspeed shown on the rqtatable
ring by the indicator pointer. For best accuracy, this indication should
be corrected to calibrated airspeed by referring to the Airspeed Calibra-
tion chart in Section 5. Knowing the calibrated airspeed, read true
airspeed on the ring opposite the calibrated airspeed.
RATE-OF-CLIMB INDICATOR
The rate-of-climb 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 7-9) provides the suction
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