GCAA CAR-66 B2 Exam key terms

The quantity of matter contained in an object, measured in kilograms, and independent of where the object is located. It determines an object's resistance to acceleration and its gravitational attraction.

The force with which gravity pulls a mass toward a body such as the Earth. It equals mass multiplied by gravitational acceleration and is measured in newtons, so it changes with location.

The mass of a substance per unit volume, expressed in kilograms per cubic metre. It links an object's mass to its physical size and is used in buoyancy and fuel calculations.

The ratio of a substance's density to the density of pure water. A value above one means the substance sinks in water; it is used to identify fluids and check electrolyte strength.

A quantity that has both magnitude and direction, such as force, velocity or acceleration. Vectors are added by resolving them into components rather than by simple arithmetic.

A quantity described by magnitude alone, with no direction, such as mass, temperature, time or energy. Scalars combine by ordinary arithmetic addition.

The single vector that produces the same overall effect as two or more individual vectors acting together. It is found by graphical or trigonometric addition of the components.

The turning effect of a force about a point, equal to the force multiplied by the perpendicular distance from the point to the force's line of action. Measured in newton metres.

A twisting moment produced by a force acting at a distance from an axis, commonly applied to shafts, nuts and bolts. It is measured in newton metres and tightened to specified values.

The point through which the total weight of an object acts, regardless of its orientation. Its position affects aircraft balance, stability and control effectiveness.

The internal force per unit area set up within a material when it is loaded, expressed in pascals or newtons per square millimetre. It may be tensile, compressive or shear.

The deformation of a material produced by stress, expressed as the change in length divided by the original length. It is dimensionless and elastic up to the yield point.

The ratio of tensile stress to tensile strain within the elastic region of a material. A high value indicates a stiff material that deflects little under load.

Progressive cracking of a material caused by repeated or fluctuating stress below its ultimate strength. It starts at stress raisers such as scratches, sharp corners or corrosion pits.

Chemical or electrochemical deterioration of a metal by reaction with its environment, such as rusting of steel or galvanic attack between dissimilar metals. It reduces strength and creates stress raisers.

Corrosion caused when two dissimilar metals are joined in the presence of an electrolyte, forming a small electrical cell. The more active metal becomes the anode and corrodes preferentially.

The tensile load deliberately induced in a bolt or fastener when it is tightened, which clamps the joint and reduces the fluctuating load the bolt experiences in service.

The relationship stating that current through a conductor equals the voltage across it divided by its resistance. It applies to purely resistive circuits and underpins all basic circuit calculations.

The opposition a component offers to the flow of electric current, measured in ohms. It converts electrical energy into heat and depends on material, length, cross-section and temperature.

The total opposition to alternating current flow in a circuit, combining resistance with reactance from capacitors and inductors. It is measured in ohms and varies with frequency.

The opposition to alternating current caused by a capacitor or inductor, measured in ohms. Capacitive reactance falls as frequency rises, while inductive reactance rises with frequency.

The rate at which electrical energy is transferred or converted, measured in watts. In a resistive circuit it equals voltage multiplied by current, or current squared times resistance.

A material such as silicon whose conductivity lies between that of a conductor and an insulator and can be controlled by doping. It is the basis of diodes and transistors.

A two-terminal semiconductor device that conducts current readily in one direction and blocks it in the reverse direction. It is used for rectification, protection and freewheeling.

A circuit arrangement of diodes that converts alternating current into direct current. Half-wave types use one diode; full-wave and bridge types use two or four.

A three-terminal semiconductor device used to amplify signals or switch currents. Small base or gate signals control a larger current between the other terminals.

A digital circuit element that produces a defined output from one or more binary inputs according to a truth table, such as AND, OR, NOT, NAND or NOR.

A number system using only the digits zero and one, each position representing a power of two. It is the native language of digital computers and data buses.

A shared set of electrical conductors carrying digital data or addressing information between components in an avionics system. Only one transmitter may drive a bus at a time.

A system of probes and static ports that supplies ram air pressure and ambient static pressure to the airspeed indicator, altimeter and vertical speed indicator.

The angle between an aerofoil's chord line and the relative airflow. Increasing it raises lift up to the critical angle, beyond which the wing stalls.

A condition in which airflow separates from the wing because the critical angle of attack is exceeded, causing a sharp loss of lift and increase in drag. It can occur at any speed or attitude.

The principle that in a steady flow of fluid, an increase in velocity is accompanied by a decrease in pressure. It explains how aerofoils and venturi devices generate lift and pressure changes.

A mistake, slip or lapse by a person that reduces the safety margin of an activity. It is understood as a normal consequence of human limitations rather than solely a personal failing.

A person's accurate perception of what is happening around them and what it means for the task ahead. Loss of it is a common precursor to maintenance and operational errors.

A model describing human factors as the interaction between Software, Hardware, Environment and Liveware, with the central Liveware representing the person. Mismatches at the interfaces create error.

A mandatory document issued by the state of design and adopted by the authority requiring inspection, modification or limitation of an aircraft or component to correct an unsafe condition.

An advisory document from a manufacturer giving recommended inspection, modification or replacement instructions. It becomes mandatory only when referenced by an airworthiness directive or regulation.

A certification, signed by authorised personnel, stating that specified maintenance has been completed and the aircraft or component is fit for return to service within stated limitations.

The formal certification that maintenance work has been completed satisfactorily and the aircraft or component may be returned to service, signed by a certifying staff member with the correct authorisation.