The Aircraft Electrical System is
one of the most important systems in an aircraft — it provides, distributes,
and controls electrical power for all the aircraft’s components and systems.
⚙️ 1. Purpose of Electrical System
The aircraft electrical system provides power to:
- Avionics (radios, navigation systems)
- Lights (interior & exterior)
- Instruments
- Flight control systems
- Engine starting system
- Cabin systems (air conditioning, entertainment, etc.)
- Emergency systems (backup power, warning lights)
⚡ 2. Types of Electrical Power
Aircraft use two main types of current:
|
Type |
Description |
Common Uses |
|
DC (Direct Current) |
Flows in one direction |
Battery, starter motor, some avionics |
|
AC (Alternating Current) |
Changes direction periodically |
High-power systems like de-icing, lights, and large
avionics |
🔋 3. Power Sources
Main sources of electricity in aircraft:
- Battery – Supplies
DC power when engines are off or as backup.
- Alternator/Generator – Driven by
the engine or APU; converts mechanical energy to electrical energy.
- Auxiliary Power Unit (APU) – A small
engine that generates electrical power when the main engines are off.
- Ground Power Unit (GPU) – External
power source used on the ground to save fuel.
⚙️ 4. Power Distribution System
The electrical power is distributed through:
- Bus Bars: Central
distribution points that connect power to systems.
- Main Bus
- Essential Bus
- Battery Bus
- Avionics Bus
- Circuit Breakers & Fuses: Protect
circuits from overload or short circuit.
💡 5. Common Aircraft Voltages
|
System |
Voltage |
Type |
|
Light aircraft |
14V / 28V |
DC |
|
Commercial jets |
115V / 200V |
AC, 400 Hz |
⚙️ 6. Components
- Relays and Contactors: Control
high-current circuits.
- Inverters: Convert DC →
AC.
- Transformers/Rectifiers: Convert AC →
DC.
- Voltage Regulators: Keep voltage
stable.
- Bus Tie Breakers: Connect or
isolate power sources.
🧰 7. Redundancy & Reliability
Aircraft electrical systems are redundant —
meaning there are backup power sources to ensure safety even if one system
fails:
- Dual or triple generators.
- Independent power buses.
- Emergency battery power for essential instruments.
🚨 8. Emergency Power
If all main systems fail:
- The battery powers essential instruments.
- On large aircraft, a RAT (Ram Air Turbine) deploys
to generate emergency power using airflow.