Aircraft Electrical Systems Overview

Batteries and generators are the primary sources of electrical power on an aircraft. They produce electricity directly.

Inverters and transformer rectifier units (TRU) are secondary sources of power. They convert existing electricity into a different form.

Direct Current (DC) flows in one direction. Alternating Current (AC) changes direction periodically. Aircraft systems use both types.

A device that converts DC into AC. Commonly used to power equipment from the battery.

A device that converts AC into DC. Often used to charge batteries from AC generators.

A self-contained power source that provides electrical power and air for engine starting when the aircraft is on the ground.

A device that generates power using the airflow from the aircraft's movement. Used as a backup in case of generator failure.

The electrical system is crucial for aircraft safety and economy. It's interconnected by wires and cables that need careful installation and maintenance.

Fuel is moved between tanks on larger aircraft, either manually by the crew or automatically using a computer.

Aircraft lights are used for safety, operations, servicing, and passenger convenience.

Cabin electronics provide safety features, entertainment, and comfort for passengers.

The passenger address system allows flight crews to make announcements throughout the cabin.

Aircraft galleys are equipped with various appliances depending on the size and purpose of the aircraft.

Air conditioning and pressurization systems provide comfort and safety for passengers at high altitudes.

Airstairs enable passengers and crew to access the aircraft without needing a separate staircase.

Sensors are used to monitor and control various aircraft systems, such as landing gear and control surfaces.

The process of maintaining an aircraft to meet airworthiness requirements ensuring safe operation.

Any work done on an aircraft or component, except pre-flight checks, to fix, inspect, replace, modify, or repair defects.

Electrical components like wires and cables need meticulous installation and regular maintenance to ensure reliable operation.

The staff responsible for ensuring an aircraft or component is safe after maintenance.

Special equipment and documents are needed to maintain an aircraft and its systems.

Direct Current (DC) flows constantly in one direction.

Alternating Current (AC) changes direction periodically.

Inductive reactance (XL) increases proportionally with the frequency of the alternating current.

Capacitive reactance (XC) decreases inversely with the frequency of the alternating current.

Impedance (Z) is the total opposition to current flow in an AC circuit, considering both resistance and reactance.

Impedance (Z), resistance (R), and reactance (X) form a right triangle, where Z is the hypotenuse.

The rate at which energy is used. One watt is equivalent to one joule of energy used per second.

A unit of electrical energy commonly used to measure household electricity consumption.

The relationship between power (P), current (I) and voltage (V) in an electrical circuit. Power is the product of current and voltage.

A device that produces electrical power. They can be powered by batteries, generators, or other sources.

Energy stored in a circuit element, such as a capacitor. Measured in joules (J).

The amount of time over which power is supplied or used. Measured in seconds, minutes, or hours.

The difference in electrical potential between two points in an electrical circuit. Measured in volts (V).

The induced electromotive force (e.m.f.) opposes any change in current. This is why it's also known as a back e.m.f.

The maximum induced e.m.f. occurs when the conductor cuts the magnetic flux lines at a 90-degree angle.

The ability of a coil to induce an e.m.f. within itself when the current through it changes. It's measured in henries (H).

When a changing current in one inductor induces a current in a nearby inductor. This is due to the changing magnetic flux cutting through the second inductor.

The induced e.m.f. in an inductor is proportional to the rate of change of current. This is described by Lenz's law.

A coil is said to have an inductance of 1 henry when a voltage of 1 volt is induced across it when the current changes at a rate of 1 ampere per second.

The formula for calculating self-inductance L is L = -e / (dI/dt), where e is the induced e.m.f. and dI/dt is the rate of change of current.

A coil with a self-inductance of 15 mH has a back e.m.f. of 6.75 V when the current changes at a rate of 450 A/s.