Aircraft Familiarization, Systems, and Hazard Recognition
This domain checks that you can predict how an aircraft is built and how it fails - which compartments hold stored energy, which fluids ignite, and where cutting will kill you.
Structure
Most transport fuselages are semi-monocoque aluminum alloy: skin carrying load, stringers and frames stiffening it, bulkheads closing pressure compartments. Wings are built around spars and ribs with integral "wet wing" fuel tanks. Composites (carbon and glass fiber) now appear in primary structure - they burn with dense toxic smoke, and carbon dust is both a skin irritant and an electrical conductor. Landing gear, engines, APU, and the empennage all create crush and entrapment zones.
Systems that become hazards
Fuel (Jet A flash point roughly 38 °C minimum; avgas far more volatile), hydraulic accumulators holding pressure, bleed air hot enough to burn through turnouts, oxygen cylinders, pressurization, electrical buses that stay live, and the APU, which may start automatically.
Hazards at the wreck
Wheel and brake assemblies can burst - approach from fore or aft, never in line with the axle. Engine intakes and exhausts have published danger zones and stay lethal after shutdown. Escape slides may inflate unexpectedly, ejection seats and ballistic parachutes may fire, lithium batteries in cabins and cargo re-ignite, and a fuselage that looks opened up may still hold pressure.
Break-in points
Many transports carry marked cut-in locations on the fuselage - dashed outlines or corner markers placed to avoid control cables, hydraulic lines, and fuel runs. Use them; the nearest window is not automatically the best entry.
Worked example. A crew faces a closed fuselage with smoke showing at the aft cabin. Reasoning: try doors first using external handles, then the marked break-in point; cutting a window risks the window frame, the pressurization web, and hidden control runs.
Traps. Treating avgas like Jet A; approaching a hot wheel from the side; assuming a crashed fuselage is depressurized.