Automatic Flight Control, Avionics and Navigation Architecture
Automatic flight control
Know the components: autopilot computer, servos or actuators, mode control panel, and the sensors (ADC, AHRS/IRU, radio altimeter). Modes include heading, altitude hold, vertical speed, ILS approach, and autothrottle. Traps: assuming the autopilot can be engaged with any failure (it may be inhibited by a disagreement between sensors); and forgetting that an autopilot disconnect must be announced by an aural warning.
Avionics and navigation architecture
Know the architecture: sensors (pitot/static, gyros, GNSS, VOR/ILS, DME, ADF, radar altimeter), processing (flight management system, air data computer, attitude and heading reference system), and displays (primary flight display, navigation display, engine indication and crew alerting system). Data buses (ARINC 429, 629, 664) carry the data. Traps: confusing a flight director with an autopilot (the FD gives guidance, the AP moves the controls); and assuming a GPS approach is precision (it is not, unless it is an SBAS/LPV or GBAS approach).
Worked example
Worked example: the autopilot disconnects and the master warning sounds. Reasoning: check for a sensor disagreement (airspeed, altitude or attitude), an autopilot fault, or a power interruption. The rule is: disconnect, fly manually, identify the cause, and only re-engage when the cause is understood.