Part-66 Module 1 key terms

A quantity that has both magnitude and direction, such as force or velocity, and which is added to other vectors by geometric or component methods rather than by simple arithmetic.

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

The single vector that produces the same overall effect as two or more component vectors acting together, found by vector addition.

The process of splitting a single force into two perpendicular components, usually horizontal and vertical, so that each can be analysed separately.

The turning effect of a force about a point, calculated as force multiplied by the perpendicular distance from the point to the line of action of the force.

Two equal, parallel, oppositely directed forces whose lines of action are separated by a distance, producing rotation without any net translational force.

The point through which the total weight of a body is considered to act, so that the body balances about it in any orientation.

Mass is the quantity of matter in a body, measured in kilograms and unchanged by location; weight is the gravitational force on that mass, measured in newtons and dependent on gravity.

The internal intensity of force within a material, calculated as load divided by cross-sectional area and expressed in pascals or newtons per square millimetre.

The deformation of a material expressed as the change in length divided by the original length. It is a dimensionless ratio and may be elastic or plastic.

The ratio of tensile stress to tensile strain within the elastic region of a material, representing its stiffness.

Progressive cracking of a material caused by repeated or fluctuating stress at levels below its ultimate strength, often starting at a stress concentration.

A local increase in stress caused by a sudden change of section, hole, notch, or sharp corner, which can initiate cracks.

Chemical or electrochemical deterioration of a metal by reaction with its environment, commonly forming oxides or salts that weaken or pit the surface.

Corrosion accelerated when two dissimilar metals are in electrical contact in the presence of an electrolyte, the more active metal becoming the anode and corroding.

Controlled heating and cooling of a metal to alter its internal structure and so change properties such as hardness, strength, or ductility.

A heat treatment that softens a metal and relieves internal stresses by heating it and then cooling it slowly, usually by furnace cooling.

A material's resistance to local surface indentation or scratching, often assessed by an indentation test and used as an indicator of wear resistance.

The relationship stating that current through a conductor is directly proportional to the potential difference across it and inversely proportional to its resistance, at constant temperature.

The opposition of a conductor to the flow of electric current, measured in ohms and depending on material, length, cross-sectional area, and temperature.

A property of a material expressing how strongly it opposes current flow, independent of the component's shape; resistance equals resistivity times length divided by area.

In series, components share one current path so current is common and voltages add; in parallel, components share the same voltage and currents add.

Two rules for circuit analysis: the current law states that currents entering a junction equal those leaving, and the voltage law states that voltages around a closed loop sum to zero.

The ability of a component to store electric charge per unit voltage, measured in farads and determined by plate area, separation, and the dielectric between them.

The property of a coil by which a changing current induces an electromotive force opposing that change, measured in henries.

The total opposition to alternating current in a circuit, combining resistance with reactance and measured in ohms.

A two-terminal device that conducts readily in one direction and blocks current in the reverse direction, used for rectification and circuit protection.

A three-terminal semiconductor device that can amplify or switch signals, in which a small control current or voltage regulates a larger current between the other terminals.

A circuit, usually using diodes, that converts alternating current into direct current, producing half-wave or full-wave output.

A basic digital circuit element that produces an output determined by combinations of its inputs, according to a rule such as AND, OR, or NOT.

A number system using only the digits 0 and 1, each position representing a power of two, widely used because digital circuits have two stable states.

A system that measures total pressure from a forward-facing probe and static pressure from a flush port, supplying the airspeed indicator, altimeter, and vertical speed indicator.

An instrument that derives speed from the difference between pitot (total) pressure and static pressure, displaying indicated airspeed.

An instrument that displays height above a reference pressure level by sensing static pressure, set to a local or standard pressure datum.

The angle between the chord line of an aerofoil and the relative airflow, whose increase raises lift until the critical angle is reached.

The aerodynamic force perpendicular to the relative airflow that supports an aircraft in flight, arising mainly from pressure differences around the aerofoil.

A loss of lift occurring when the angle of attack exceeds the critical value and airflow separates from the upper surface, largely independent of airspeed.

The upward angle of the wings relative to the lateral axis, which provides lateral stability by producing a restoring roll after a sideslip.

The tendency of an aircraft to return to its original flight condition after a disturbance, described separately for pitch, roll, and yaw axes.

In forward helicopter flight, the advancing blade meets air faster than the retreating blade, producing unequal lift that is balanced by blade flapping.

The sideways drift of a helicopter in the direction of tail rotor thrust, normally countered by a small cyclic input or a built-in mast tilt.

A certification, made by authorised personnel after maintenance, confirming that the work has been completed satisfactorily and the aircraft or component is fit for return to service.

The condition of an aircraft or component meeting the applicable design, maintenance, and operational requirements so that it is safe to fly.

A mandatory instruction issued by an aviation authority requiring inspection, modification, or other action on affected aircraft or components to correct an unsafe condition.

An organisation holding a formal approval from the competent authority to perform specified maintenance within the scope and limitations of that approval.

A structured set of processes and policies for identifying hazards, assessing and controlling risk, and continuously improving safety within an organisation.

An unintended action or omission by a person that leads to a deviation from intended outcome, commonly classified as slip, lapse, mistake, or violation.

A model of human factors describing mismatches at the interfaces between Software, Hardware, Environment, and Liveware, with the central Liveware representing the person.

The reaction force on a helicopter fuselage caused by the engine driving the main rotor, which the tail rotor counteracts to maintain heading.

A principle stating that in steady streamline flow of an incompressible fluid, an increase in velocity is accompanied by a decrease in pressure, used to explain aerofoil lift.

The reduction in fluid pressure that occurs where a flow is constricted and its velocity increases, applied in instruments such as some airspeed and fuel devices.

A calibrated tool that applies a measured twisting moment to a fastener, used where specified tightening loads must be achieved without overstressing components.

Inspection methods such as dye penetrant, magnetic particle, eddy current, ultrasonic, and radiographic testing that reveal defects without damaging the part.

Measures such as protective coatings, sealants, plating, and drainage design that keep moisture and electrolytes away from metal surfaces to limit deterioration.