Aeroplane Aerodynamics, Structures and Systems
Control and high-speed effects
Primary controls are ailerons (roll), elevators (pitch) and rudder (yaw); secondary controls include flaps, slats, spoilers and trim. Flaps increase lift and drag; spoilers dump lift and add drag. At high speed know the critical Mach number, shock formation, Mach buffet, Mach trim and the purpose of wing sweep. Fly-by-wire replaces mechanical linkage with computers and can provide flight-envelope protection.
Structures
Semi-monocoque construction: the skin carries pressurisation loads and shear, stringers and frames stiffen it, and spars carry bending. Know the stress types - tension, compression, shear, torsion and bending - plus fatigue, corrosion and damage-tolerance inspection intervals.
Systems
Hydraulics (commonly around 3 000 psi), pneumatics, air conditioning and pressurisation, fuel, ice and rain protection, landing gear and brakes (anti-skid, auto-brake), and electrical power (AC generators, transformer-rectifier units, batteries, bus ties).
The traps
Thinking the outflow valve opens to raise cabin pressure (it opens to let pressure out, so cabin altitude climbs); confusing spoilers with speed brakes; forgetting that a hydraulic system serves several users and has priority valves; assuming fly-by-wire removes the need for pilot skill.
Worked example
An aircraft in level flight shows cabin altitude climbing. The outflow valve has opened too far, reducing differential pressure. Rule: outflow valve open = cabin pressure falls toward ambient; outflow valve closed = cabin pressure rises.