Hydraulic, electrical, fuel, environmental control/pressurization, and landing gear systems, how they interact as one system of systems, and the fail-safe redundancy philosophy every one of them is engineered around.
An aircraft's hydraulics, electrical power, fuel, environmental control, and landing gear systems are not five independent design problems — a hydraulic pump is driven off the same engine accessory gearbox as an electrical generator, a fuel system's feed path has to keep working through the exact maneuvers stability and control analysis evaluates for handling qualities, and none of the five is actually sized in isolation from what happens when one of the other four fails first. This module works through each subsystem in turn before closing on the fail-safe design philosophy — physical separation, functional redundancy, and independent backup means — that ties all five together.
By the end of this module you should be able to explain why a catastrophic failure condition carries a roughly one-in-a-billion-per-flight-hour probability target achievable only by combining independent redundant elements, and why a minimum equipment list codifies pre-analyzed engineering margin rather than improvised judgment — the same redundancy discipline this program's spacecraft systems module (Module 14) applies under an even harder constraint: no maintenance access at all.