Electrical and Electronic Systems
Generation, distribution and protection
Know the aircraft electrical architecture: AC generation (IDG or VFG), constant-speed drive principles, APU and emergency sources (battery, RAT, static inverter), TRUs for DC, and bus structures (main, essential, emergency, battery bus). Understand split-bus and parallel operation, generator control units (GCU) with over/under-voltage, over-frequency and differential protection, and the logic of bus transfer. On protection, distinguish circuit breakers (resettable, thermal/magnetic), fuses (one-shot) and the rule that a popped breaker is not simply reset without investigation.
Electronics and indication
Understand the difference between analogue and digital signalling, ARINC 429 versus CAN and AFDX at concept level, and the meaning of redundancy and dissimilarity. Know the pitot-static and air-data chain, the role of the ADC and IRU, and why a blocked pitot or static port gives specific errors (airspeed, altitude, VSI). Note the basics of EMI/HIRF protection and bonding.
Traps
Questions test the unit of protection: what does a GCU protect against, and what does a bus tie do? They test battery behaviour (capacity falls with cold, voltage sags on start) and the correct action on a gen off light (check the cause, do not force the breaker). They test whether a component is on the essential bus and therefore survives loss of a main generator.
Worked example
A question asks what happens when a main generator trips in flight. Reason: the GCU removes the generator from the bus, the bus tie closes to the remaining source, and the essential bus stays powered. Choose the option describing automatic bus transfer, not the option describing manual reset in flight.
Rule of thumb
For each electrical question, ask source, bus, protection, load priority.