Quick questions on Aircraft electrical and avionics: HSC Engineering Studies Aeronautical Engineering

A typical airliner electrical system has:

Most large airliners use 115 V AC three-phase at 400 Hz for main distribution. The higher frequency (versus 50 Hz mains) allows smaller transformers and motors, saving mass. The Boeing 787 raised the standard to 235 V AC three-phase, allowing the same power at lower current and reducing wire mass.

Traditional aircraft used mechanical cables and pushrods from the control column to the hydraulic actuators at the control surfaces. Modern airliners use fly-by-wire (FBW):

For a DC system, Ohm's law gives the voltage drop along a wire:

Essential systems (flight instruments, hydraulics, fly-by-wire, communication) are powered from an essential bus that can be fed from any generator, the APU, the battery or the RAT. Non-essential systems (galleys, in-flight entertainment, cabin lighting) are on separate buses and are shed first during a generator failure.

The Boeing 787-9 Dreamliners operated by Qantas use MEA architecture; the Airbus A380 fleet (still in service for Qantas international routes) uses traditional bleed-air pressurisation and hydraulic primary flight controls but FBW. Royal Australian Air Force F-35A Lightning II combat aircraft use a fully FBW flight control system with quadruply redundant computers.

400 Hz is chosen for mass reasons (smaller transformers and motors), but it limits cable lengths because of skin-effect and inductive losses.

Aircraft electrical systems have at least four independent generation sources for the essential bus.