文档介绍：Introduction to Aircraft Design
Chapter 6
What’s under the skin?
Airframe systems
1
Secondary Power Systems
Secondary power is usually provided by an aircraft’s main engines when they are operating but can be supplied by other sources such as an auxiliary power unit (APU) in the aircraft or an external source on the ground.
Almost all present a/c SPS are of three types: electric power, bleed air/pneumatic power, and hydraulic power, see .
the engine’s hp shaft drives an accessory gear box on which are mounted generator and hydraulic pumps as well as the engine’s own accessories.
2
Air-conditioning and pressurization
Bleed air is tapped from one or more points along the engine compressor to supply the aircraft’s air-conditioning and pressurization system.
It is usual to maintain an a/c cabin at a pressure equivalent to that at 8000ft (2400m) or less and this requires a constant supply of pressurized air.
Oxygen used by the occupants must be replaced and the temperature and contaminant levels controlled, requiring a significant air.
3
Air-conditioning and pressurization
Fig. shows the major elements of an air-conditioning system.
The combination of air-conditioning, pressurization and oxygen systems are usually termed the environmental control system (ECS).
In addition to cooling the crew and passenger compartments on high-speed a/c it may be necessary to remove heat from the undercarriage bays, electrical equipment and flying control areas.
4
Air-conditioning and pressurization
Military a/c use ECS systems working on the same principles as those for civil a/c, but
The pressurized cabin has a much smaller volume and works at a lower pressure differential.
Oxygen systems are used in normal operations at higher altitudes.
Military avionics are more complex and produce comparatively more heat and thus require more cooling. Hawk Trainer is shown in .
5
Ice protection systems
Dangerous icing condi