All/More Electric Aircraft Engine & Airframe Systems - Turbo & Jet ...

“Conventional”
Philosophy
Secondary power systems (SPS) are the power distributed
around the engine and airframe systems and not used for
propulsion (this being the primary power). On most aircraft
SPS are distributed in three forms:
Electric (avionics, lights, instruments, entertainment, etc.),
Hydraulic (primary & secondary flight controls, landing gears,
brakes, steering, doors, other actuation functions),
Bleed air or pneumatic (environmental control system ECS, cabin
pressurization, engine cowl and wing ice protection, engine starting).
Unclassified
4