QCAA Aerospace Systems key terms

A shaped surface, such as a wing or tailplane, designed to produce lift as air flows over it. Its curved upper surface speeds up airflow, lowering pressure above the wing.

The angle between a wing's chord line and the oncoming relative airflow. Increasing it raises lift up to the stall angle, beyond which airflow separates and lift drops sharply.

The curvature of an aerofoil, measured as the distance between its mean line and chord line. More camber generally produces more lift at a given speed but also more drag.

A straight reference line drawn from the leading edge to the trailing edge of an aerofoil. It is the baseline used to measure angle of attack and camber.

The upward aerodynamic force generated perpendicular to the relative airflow. It results from pressure differences around an aerofoil and must balance weight for level flight.

The aerodynamic force opposing an aircraft's motion through the air, acting parallel to the relative airflow. It includes parasite drag from shape and skin friction, plus induced drag created by lift.

Drag produced as a by-product of generating lift, caused by high-pressure air spilling around wingtips to form vortices. It increases with angle of attack and is greatest at low speed.

A swirling mass of air trailing from a wingtip where higher-pressure air beneath the wing curls around to the lower-pressure upper surface. Vortices create induced drag and wake turbulence.

A small vertical extension fitted to a wingtip that reduces the strength of wingtip vortices. This lowers induced drag and improves fuel efficiency without greatly increasing wingspan.

A sudden loss of lift when the angle of attack exceeds a critical value and airflow separates from the upper wing surface. It can occur at any speed or attitude.

The specific angle of attack at which airflow begins to separate from an aerofoil and lift starts to decrease. Exceeding it causes a stall regardless of airspeed.

The point through which the total weight of an aircraft acts. Its position affects stability and control, and must remain within approved limits for safe flight.

The point on an aerofoil where the total aerodynamic force effectively acts. Its position shifts as angle of attack changes, influencing pitching moments on the aircraft.

An aircraft's tendency to return to its original flight condition after being disturbed. It depends on the relative positions of the centre of gravity and aerodynamic forces.

The forward force produced by engines or propellers that overcomes drag and propels the aircraft. In steady level flight it equals total drag.

The downward force on an aircraft caused by gravity acting on its mass. In steady level flight it is balanced by lift.

A principle stating that where fluid speed increases, its pressure decreases. It helps explain how faster airflow over a wing's upper surface produces lower pressure and generates lift.

The law stating every action has an equal and opposite reaction. It explains lift and thrust as the aircraft deflecting air downward and rearward, producing opposite forces.

The direction of air approaching an aircraft as it moves through the atmosphere. It defines angle of attack and determines the aerodynamic forces acting on the airframe.

The ratio of a wing's span to its mean chord, describing how long and slender it is. High aspect ratio wings produce less induced drag and suit gliders and efficient airliners.

The main body of an aircraft that houses the cockpit, cabin and payload, and to which the wings and tail are attached. It carries primary structural loads.

The tail assembly of an aircraft, comprising the horizontal and vertical stabilisers plus their control surfaces. It provides stability and pitch and yaw control.

A fixed aerodynamic surface at the tail that keeps the aircraft steady in pitch or yaw. It is often fitted with a movable control surface such as an elevator or rudder.

A hinged control surface on the outer trailing edge of each wing that moves in opposite directions. It controls roll about the longitudinal axis.

A hinged control surface on the horizontal stabiliser that changes the aircraft's pitch. Moving it up or down raises or lowers the nose.

A hinged control surface on the vertical stabiliser that controls yaw about the vertical axis. It is operated by the pilot's feet through rudder pedals.

A hinged surface on the inner trailing edge of a wing that extends to increase lift and drag at low speeds. Flaps allow slower takeoff and landing speeds.

A main longitudinal structural member running along a wing or fuselage that carries bending loads. Spars form the backbone of the wing structure.

A curved structural member that gives a wing its aerofoil cross-sectional shape and supports the skin. Ribs run chordwise between the spars.

The outer covering of an aircraft that forms the aerodynamic surface and carries part of the structural load. It may be aluminium alloy, composite or fabric.

A material made from two or more constituents, such as carbon fibres set in a resin matrix, to combine strength and light weight. Composites are widely used in modern airframes.

The progressive weakening and cracking of a material caused by repeated cyclic loads over time. Fatigue failure is a major concern for ageing aircraft structures.

Rotation of an aircraft about its lateral axis, raising or lowering the nose. It is controlled primarily by the elevator.

Rotation of an aircraft about its longitudinal axis, tilting the wings left or right. It is controlled primarily by the ailerons.

Rotation of an aircraft about its vertical axis, swinging the nose left or right. It is controlled primarily by the rudder.

A jet engine in which a large fan drives air rearward, with some air bypassing the core. It provides high thrust efficiently and powers most modern airliners.

A gas turbine engine that drives a propeller through a reduction gearbox. It is efficient at lower speeds and suits regional aircraft.

The condition of an aircraft being safe and fit for flight according to approved standards. It is maintained through design certification, inspection and maintenance programs.

The formal regulatory process confirming an aircraft or component meets required safety standards. It typically involves type certification of designs and individual airworthiness certification.

A government body responsible for setting and enforcing aviation safety rules, such as CASA in Australia. It certifies aircraft, licenses personnel and oversees maintenance.

A documented plan specifying when and how inspections, servicing and component replacements must be carried out. It keeps the aircraft compliant with airworthiness requirements.

Scheduled servicing and inspection intended to prevent failures before they occur. It contrasts with corrective maintenance performed after a fault is found.