PLT111: Series and Parallel Circuits
What code PLT111 covers, why the FAA tests it, and how to study Series and Parallel Circuits before your checkride.
Recall aircraft circuitry - series / parallel
What this means for your checkride
Aircraft electrical circuits are wired in series or parallel. In a series circuit the same current flows through every component and voltage divides among them, so one break stops everything. In a parallel circuit each branch sees the full voltage and current divides, so one branch can fail without killing the rest, which is why buses power loads in parallel.
Series versus parallel explains how a bus and its loads behave and why one failure does or does not take down the system, so the FAA tests the basics.
Pilots expect one blown item to kill the whole electrical system. Loads on a bus are in parallel, so a single failed load usually drops only its own branch, protected by its own breaker.
Where to study it
A code on your test report is an area of deficiency. An authorized instructor must review it with you and endorse that review before you take the practical test, and the examiner may revisit it during the oral. Study it until you can explain it out loud, not just recognize the answer.