System 40 Modes Of Operation - Cessna 172N 1979 Pilot Operating Handbook

3.0 Theory of Operation

3.1 System 40 Modes of Operation

NOTE:
The Aircraft (AC) instrument light rheostat controls the
annunciator and indicator brightness.
1. The System 40 provides the aircraft with Roll Axis control only.
2. The Turn Coordinator contains the Rate Gyro, Autopilot pick-off, Rate
Gyro RPM detector, and an instrument power monitor that will flag if low
system voltage occurs.
3. The System 40 Programmer/Computer, which contains the Roll Computer,
receives power through the battery buss and connects to the panel mounted
ON/OFF/TEST switch through the A/P circuit breaker (CB).
4. The Rate Gyro is the basic sensor for roll stabilization.
5. The Rate Gyro signal combines either with the Turn Command Knob,
Heading Error Signal, or NAV inputs to generate a Roll Error signal, which
then drives the roll servo as needed.
6. The System 40 operates in one of five Roll Modes, three of which are
Navigation (NAV) Modes. The Roll modes are Stabilizer (STB) and Heading
(HDG); the NAV Modes are Approach (APR), Navigation (NAV), and
Reverse (REV).
7. The Programmer/Computer Unit provides the Mode Select Switches
and annunciation for the system.
8. Mode Annunciation Window displays mode in use.
2nd Ed: October 25, 2002
MODES
L R
SYSTEM 40/50 POH
3-3