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High-speed aerodynamics
Mach number M = TAS ÷ local speed of sound. Subsonic below M0.75, transonic M0.75–1.2, supersonic above. Shock waves cause wave drag, buffet and Mach tuck. Swept wings, area rule, vortex generators and supercritical aerofoils delay compressibility effects. Critical Mach number is the free-stream Mach at which airflow first reaches M1 locally.
Structures & zoning
Semi-monocoque construction: skin carries shear, stringers carry bending, frames maintain shape. Design philosophies: safe-life, fail-safe and damage tolerance. Aircraft are divided into zones and stations (Fus. STA, WS, BL, WL) so defects and tasks can be located precisely. Pressurised fuselages are limited by cycles as well as hours.
Flight controls
Primary: ailerons (roll), elevator (pitch), rudder (yaw). Secondary: flaps, slats, spoilers/speed brakes, trim tabs. Systems may be manual, power-assisted or fully powered fly-by-wire with artificial feel. Balance and mass balance prevent flutter; rigging and control-surface travel checks are done against the AMM with rig pins and protractors.
Hydraulics, landing gear & flight controls
Typical transport hydraulic systems run at 3000 or 5000 psi using phosphate-ester fluid (Skydrol) with multiple independent systems and PTU cross-connection. Landing gear includes oleo-pneumatic shock struts, retraction, brakes with anti-skid and autobrake, nose-wheel steering, and tyres inflated with nitrogen.
Air, pressurisation, ice & rain
Engine bleed (or electric compressors on the B787) feeds air conditioning packs with air-cycle machines. Cabin pressurisation is controlled by outflow valves to a cabin altitude typically ≤8000 ft, with maximum differential protection. Ice protection: hot bleed air on wing/cowl anti-ice, electrical heating for probes and windshields, and pneumatic boots on turboprops.
Electrical, fuel, fire and other systems
Electrical: engine IDG/VFSG generators, APU generator, external power, TRUs, batteries and RAT for emergencies. Fuel: tank layout, boost pumps, crossfeed, refuel/defuel panel, jettison, and measurement by capacitance probes. Fire protection: detection loops, smoke detectors and Halon/next-generation extinguishing. Also covered: oxygen, water/waste, avionics, doors, windows and lights.