CAAB AME B1.2 key terms

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

Functions such as sine, cosine and tangent that relate the angles of a right-angled triangle to the ratios of its sides. They are used to resolve forces and other vectors into perpendicular components.

The power to which a base must be raised to produce a given number. Logarithms turn multiplication and division into addition and subtraction, and they appear in decibel and sound-level calculations.

The acceleration of a body is directly proportional to the net force acting on it and inversely proportional to its mass, written as force equals mass times acceleration. It underpins thrust, drag and load calculations.

In a steady flow of fluid, an increase in the fluid's speed is accompanied by a decrease in its static pressure, provided no energy is added. This principle explains how a wing generates lift.

The fractional change in length of a material per unit change in temperature. It predicts how much a metal part grows when heated, which matters for clearances and for joints between dissimilar metals.

For a conductor at constant temperature, the current through it is proportional to the voltage across it, written as voltage equals current times resistance. It is the basis of simple circuit analysis and voltage-drop checks.

Around any closed loop in a circuit, the algebraic sum of the voltage rises and voltage drops is zero. It is used to find unknown voltages and currents in series and parallel networks.

The ability of a component to store electrical charge, measured in farads. A capacitor opposes changes in voltage, so it is used for smoothing, filtering and timing in aircraft circuits.

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

The effective value of an alternating current or voltage, producing the same heating effect as the equivalent direct current. For a sine wave it is 0.707 times the peak value.

A two-terminal device made from p-type and n-type material that conducts easily in one direction and blocks current in the other. It is used for rectification, protection and signal detection.

A three-terminal semiconductor device in which a small base current controls a much larger current flowing between collector and emitter. It is used as an amplifier or as an electronic switch.

A high-gain integrated-circuit amplifier with an inverting and a non-inverting input. With external feedback components it performs precise amplification, filtering and mathematical functions in instrument and control circuits.

An electronic circuit that produces a defined output for a given combination of binary inputs. Common types include AND, OR, NOT and NAND, which form the building blocks of digital systems.

A widely used civil aircraft digital data bus standard that sends 32-bit words from one transmitter to one or more receivers over a twisted pair. It carries data between avionics units.

A circuit that converts a continuously varying voltage into a digital code a computer can process. It forms the interface between sensors such as pressure or temperature probes and digital indicating systems.

Corrosion caused by electrical contact between two dissimilar metals in the presence of an electrolyte, where the more active metal becomes the anode and is eaten away. It is prevented by separation, sealing or protective coatings.

Heating an aluminium alloy until the alloying elements dissolve, then quenching rapidly to hold them in solution. It is followed by natural or artificial ageing, which raises the strength and hardness of the part.

A permanent fastener with a manufactured head and a plain shank, installed by deforming the projecting end into a second head. It is the standard structural fastener for sheet-metal aircraft structures.

A standard screw-thread system with a 60-degree profile, designated by nominal diameter and threads per inch, such as UNF fine or UNC coarse series. It ensures interchangeability of bolts, nuts and fittings.

The manufacturer's document giving approved procedures, tolerances and inspection intervals for maintaining a specific aircraft type. It is the primary reference for scheduled and unscheduled maintenance tasks.

A tool that applies and indicates a controlled twisting force to a fastener so that the specified preload is reached. It must be calibrated at intervals and used within its rated range.

A safety method in which annealed wire is threaded through holes or around fasteners and twisted so that vibration cannot loosen them. Twist direction and end length follow approved maintenance practice.

Inspection methods that reveal defects in a part without damaging it, including dye penetrant, magnetic particle, eddy current, ultrasonic and radiographic techniques. Each method suits particular materials and defect types.

The angle between the chord line of a wing and the relative airflow. Increasing it raises lift up to the critical angle, beyond which the wing stalls.

The point at which the aircraft's weight is considered to act. Its position must stay within the forward and aft limits for stable, controllable flight and to keep structural loads within design values.

A sudden loss of lift that occurs when a wing exceeds its critical angle of attack. It can happen at any speed, attitude or weight, and is recovered by reducing the angle of attack.

Drag created as a by-product of lift, caused mainly by the rearward inclination of the lift vector and by wingtip vortices. It rises with angle of attack and is reduced by higher aspect ratio.

A framework describing human performance as the interaction of software, hardware and environment with the liveware at the centre. Mismatches at these interfaces create error, so the model guides investigation and safety work.

Being aware of what is happening around the aircraft and what it means for the task in hand, now and shortly ahead. Losing it is a common factor in maintenance and operational errors.

A self-satisfied state in which a person assumes all is well and stops checking, often after long familiarity with a task. It leads to skipped steps, missed defects and routine violations.

A mandatory instruction issued by the state of registry requiring inspection or modification of aircraft to correct an unsafe condition. Compliance is compulsory within the stated timescale and is recorded in the aircraft records.

An approval issued by the airworthiness authority confirming that an aircraft, engine or propeller design meets the applicable certification requirements. It defines the approved design and precedes certification of individual aircraft.

A certification, signed by authorised personnel, that required maintenance has been completed satisfactorily and the aircraft or component is fit to return to service within stated limits.

An approved document allowing an aircraft to be dispatched with specified items of equipment inoperative, subject to defined conditions, limitations and rectification intervals. It is derived from the master minimum equipment list.

The theoretical distance a propeller would advance in one revolution if it turned in a solid medium with no slip. It is fixed by blade angle and radius, and is compared with the effective pitch.

The difference between the geometric pitch of a propeller and the distance it actually advances through the air in one revolution. It indicates how effectively the blades convert rotation into thrust.

Turning the propeller blades to an angle at or near zero lift so that the propeller stops windmilling and produces minimum drag. It is used on multi-engine aircraft after an engine failure.

A propeller whose blade angle is varied automatically by a governor so that the engine holds a selected rotational speed as load or power changes. Blade angle increases when the engine tends to overspeed.