Aircraft General Knowledge - Airframe, Systems and Structures
What you must understand
Start with structural philosophy: the difference between fail-safe (multiple load paths, crack-stopper straps, scheduled inspection) and safe-life (component retired before predicted failure), and damage tolerance as the modern extension of fail-safe. Know the primary, secondary and tertiary structure and why a question about a wing spar versus a fairing matters. Understand semi-monocoque construction, stringers, frames, skin, and how stress concentrations arise at cut-outs, rivet rows and joints.
Systems knowledge needs functional understanding, not just names: hydraulic systems (reservoir pressurisation, pumps, accumulators, relief and priority valves, redundant circuits), pneumatic systems (bleed sources, precoolers, pressure regulation), fuel systems (vent, boost pumps, crossfeed, unusable fuel), pressurisation (outflow valve, cabin pressure controller, negative relief), flight controls (cables and pulleys, push-pull rods, artificial feel, trim), ice and rain protection (thermal anti-ice, boots, weeping wing), and landing gear (sequencing, downlocks, microswitches).
Traps
Candidates confuse an accumulator's function (damping and emergency reserve) with a reservoir's. Questions often test which valve protects the system versus which protects the component, and which indication appears first in a sequence.
Worked example
A hydraulic system has a main pump and an electric standby pump with a check valve downstream of each. If the main pump fails, the standby pump supplies the system but cannot back-drive the failed pump because the check valve blocks reverse flow. That single check valve is the answer to most "why doesn't fluid return through the failed pump" questions.