NCATT AET key terms

The angle between an airfoil's chord line and the direction of the relative wind. Increasing it increases lift up to the critical angle, beyond which the wing stalls.

The point where the aircraft's total weight is considered to act. It must remain within published forward and aft limits for stable, controllable flight.

A system of probes and ports that supplies impact (pitot) pressure and undisturbed static pressure to airspeed, altitude, and vertical speed instruments, and to air data computers.

The ratio of total lift produced by an aircraft to its gross weight, expressed in Gs. Higher load factors increase structural stress and raise stall speed.

In a steady flow of fluid, an increase in speed is accompanied by a decrease in pressure. This explains how airfoils produce lift and how venturi instruments work.

A coordinate system of fuselage stations, wing stations, buttock lines, and waterlines used to locate components and wire routing points on a specific aircraft model.

The relationship stating that current equals voltage divided by resistance (I = E/R). Technicians use it to calculate expected values when troubleshooting a circuit.

The total opposition a circuit presents to alternating current, combining resistance with capacitive and inductive reactance. It is measured in ohms and varies with frequency.

A device, usually made of diodes, that converts alternating current into pulsating direct current. Aircraft DC systems often use rectifiers fed from AC generators.

A component that stores energy in an electrostatic field between two conductors separated by a dielectric. It blocks DC while passing AC and is used for filtering and timing.

A coil that stores energy in a magnetic field and opposes changes in current. Its opposition, called inductive reactance, increases as frequency increases.

A device with two or more coils coupled by a magnetic core that changes AC voltage and current levels through mutual induction, without a direct electrical connection between windings.

The common return path in an electrical circuit. In aircraft, the metal structure often serves as ground, so one wire can feed a component and current returns through the airframe.

A resettable protective device that opens a circuit automatically when current exceeds a rated value, protecting wiring from overheating. Unlike a fuse, it can be reset after the fault is corrected.

A base-2 numbering system using only the digits 0 and 1. Digital computers represent all data and instructions as patterns of binary bits.

A circuit that produces a specific output based on combinations of digital inputs, following rules such as AND, OR, NOT, NAND, and NOR.

A circuit that samples a continuously varying voltage and converts it into a digital number a computer can process, for example when digitizing a sensor output.

A widely used one-way digital data bus standard in which a single transmitter sends 32-bit words to up to 20 receivers over a twisted, shielded pair.

An avionics component designed to be removed and replaced quickly on the aircraft, usually with simple tools, to restore a system without shop-level repair.

A shared set of wires or fiber used to carry digital messages between avionics units, greatly reducing the amount of point-to-point wiring required.

A standard numbering system that specifies conductor size. Smaller numbers indicate larger wires; each three-number change roughly doubles the cross-sectional area.

A terminal or splice attached to a wire by mechanically compressing its barrel around the conductor with a controlled tool, forming a gas-tight electrical and mechanical joint.

A cable with a center conductor surrounded by insulation, a braided shield, and an outer jacket. It carries high-frequency signals with controlled impedance and low loss.

A low-resistance conductor connecting metal parts so they are electrically common, providing a return path and reducing static buildup, lightning damage, and radio noise.

The method of connecting a cable shield to ground or to a connector shell. Proper termination controls where interference currents flow and preserves shielding effectiveness.

A permanent joint connecting two or more wire ends so they conduct as one conductor. Aviation splices must be mechanically sound, insulated, and approved for the wire type.

The individual pin or socket inside a connector that mates with its opposite to carry a signal or power. Contacts are crimped or soldered to wires and held in the shell.

A test instrument that measures voltage, resistance, and current, and often continuity. It is the basic tool for verifying aircraft circuits before and after repair.

An instrument that applies a high test voltage to measure insulation resistance. It detects moisture, contamination, and cracked insulation that an ordinary ohmmeter cannot reveal.

A test instrument that sends a pulse down a cable and displays reflections. The delay and shape of reflections reveal opens, shorts, and impedance changes along the line.

A check, usually made with an ohmmeter, confirming that a conductor provides a complete low-resistance path between two points.

A measurement of the voltage lost across a connection or conductor while current flows. Excessive drop indicates high resistance such as corrosion or a loose terminal.

An instrument that graphs voltage against time, letting a technician see waveform shape, amplitude, frequency, and noise in a circuit.

Diagnostic circuitry built into an avionics unit or system that monitors operation, detects faults, and reports results to the flight crew or maintenance personnel.

A device that radiates or receives electromagnetic energy, converting between guided electrical signals and free-space radio waves. Its performance depends on location, ground plane, and bonding.

A small pointed device on trailing edges of flight controls that bleeds off accumulated static electricity, reducing precipitation static interference with radios.

Unwanted electrical energy, radiated or conducted, that disturbs the operation of electronic equipment. Shielding, grounding, and wire separation are common defenses.

Strong external radio-frequency fields, such as from radar or broadcast transmitters, that can upset or damage aircraft electronics. Installations must be designed to withstand them.

An avionics unit that replies to ground radar interrogations with a coded altitude and identity, allowing air traffic control to identify and track the aircraft.

The practice of physically separating power, signal, and antenna cables to limit coupling of noise and to prevent a single failure from damaging unrelated circuits.