Rockwell Commander 112 - Page 182

ROCKWELL
COMMANDER
112/B/TC/TCA
MAINTENANCE MANUAL
SECTION vm
INSTRUMENTS
Never apply compressed air to lines
or components installed in the airplane.
The excessive pressures will damage
the gyro
instruments. If an obstructed
line is to be blown out, disconnect it at
both ends and blow from the instrument
panel out.
Vacuum
Regulator Valve Adjustment
When a vacuum
regulator valve adjustment is neces-
sary, it is suggested that a suction test gage be in-
stalled as a means of verifying the accuracy of the
aircraft suction gage.
a. Remove vacuum regulator filter.
b. Install suction test gage in place of aircraft
suction gage.
c.
Loosen adjusting screw checknut on regulator
valve.
d. With engine
operating at 1800 rpm adjust regu-
lator setting to obtain 5.1 c: .1)inches of mercury.
e. Tighten adjusting screw checknut on regulator
val ve, do not alter regulator valve setting.
f. Check filter and be sure it is clean before in-
stallation.
g. Operate engine at 1800 rpm and check for a
gage
reading of 4.5 to 5.2 inches of mercury.
h. Remove test gage and connect vacuum line to
aircraft suction gage and repeat step g., to check
accuracy of gage.
DIRECTIONAL GYRO (OPTIONAL)
The directional gyro is operated from the instrument
vacuum system. The air-driven gyro rotates with
its spin axis horizontal. Due to gyroscopic inertia,
the spin axis of the gyro remains constant even
though the
aircraft direction is changed; therefore,
the relative motion between gyro and instrument case
is indicated on the face of the instrument in degrees.
A knob extending from the instrument is used for di-
rectional heading adjustments and caging the gyro.
ATTITUDE GYRO (OPTIONAL)
The attitude gyro indicator provides a visual refer-
ence of the aircraft attitude relative to the pitch and
roll axis of the gyro. The gyro, which is air-driven
and operated by the vacuum system, is installed in
the left side of the instrument panel. Correct setting
of the instrument vacuum system and periodic re-
placement of the instrument air filter are essential
to accurate operation of the instrument.
TURN COORDINATOR (OP'rIONAL)
The turn coordinator consists of two instruments
within one case. The turn coordinator is operated by
an electrically-driven gyro which is connected to the
white
airplane on the face of the indicator. The air-
plane, which deflects proportionally to the rate of
turn, indicates that the aircraft is turning in the di-
rection (left or right) shown by the airplane. The
bank indicator is a curved, fluid-filled tube contain-
ing a
ball. Gravitational and centrifugal forces posi-
tion the ball within the tube to indicate correct lateral
attitude for the rate of turn.
ALTIMETER
The altimeter is an absolute pressure instrument that
converts atmospheric pressure to altitude using sea
level as a reference base (see Figure 8-5). As atmos-
pheric pressure varies with changes in altitude the
change
in pressure is expressed on the instrument
dial in feet above sea level. The altimeter has a fix-
ed dial and is equipped with three concentrically ar-
ranged pointers with a range of 20,000 feet. The long
pointer registers in 100-foot increments, the short
pointer registers in 10, ODD-foot increments, and the
remaining pointer registers in 1, ODD-foot increments.
A movable barometric scale, visible through a small
window in the main dial, indicates the barometric
pressure in inches of Hg. An adjusting knob provides
a means of adjusting the three pointe rs and barome-
tric scale simultaneously to correct for changes in
atmospheric pressure and to establish the proper
reference to sea level. . Barometric pressure is
sensed through the instrument static system.
AIRSPEED INDICATOR
MODEL 112. The airspeed indicator registers air-
speed in both knots and miles-per-hour (see Figure
8-5). The indicator is operated by the pressure dif-
ferential between impact air pressure from the pitot
tube
and barometric pressure sensed through the static
system. A white arc from 54 to 109 knots (62 to 125
mph)
indicates the wing flap operating range. A green
arc from 61 to 143 knots (70 to 164 mph) indicates the
normal operating speed. A yellow arc from 143 to
180 knots (164 to 207 mph) indicates the caution range
in which all operations must be conducted with care
and then only in smooth air. A red radial line at 180
knots (207 mph) indicates the maximum speed at which
the aircraft may be safely flown.
MODELS 112B/TC. The airspeed indicator registers
airspeed in both knots and miles-per-hour (see Figure
8-5). The indicator is operated by the pressure diff-
erential between impact air pressure from the pitot
tube and
barometric pressure sensed through the
static system. A white arc from 51 to 109 knots (59
to 125 mph) indicates the wing flap operating range.
A green arc from 56 to 143 knots (64 to 164 mph) in-
dicates the normal operating speed. A yellow arc
from 143 to 180 knots (164 to 207 mph) indicates the
caution range in which all operations must be con-
ducted with
care and then only in smooth air. A red
radial line at 180 knots (207 mph) indicates the max-
imum speed at which the aircraft may be safely flown.
MODEL 112TCA. The airspeed indicator registers
8-7
Copyright Commander Owners Group 2013 All Rights Reserved
**unofficial copy**