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Questions and Answers
What is the main purpose of high pressure bleed air in the engine?
Where does medium-pressure bleed air typically come from to start the engine?
What is one of the main functions of bleed air tapped from the engine on an aircraft?
How is excess heat removed from the air conditioning packs on an aircraft?
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In what way does bleed air contribute to keeping passengers comfortable?
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Besides providing cabin pressurization, what other purpose does bleed air serve on an aircraft?
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What is the primary purpose of bleed air on an aircraft?
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What is the primary cause of kinetic heating on an aircraft?
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What is the equation used to calculate the recovery temperature of air flowing over an aircraft's surfaces?
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What is the purpose of air-driven pumps (ADPs) on an aircraft?
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What is the purpose of the International Standard Atmosphere (ISA) in aircraft design?
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Study Notes
Pneumatic Systems
- High-pressure bleed air is used to power valves associated with bleed air extraction in engines.
- Medium-pressure bleed air is used to start engines, either from ground power units, APU, or cross-bleed from another engine.
- Bleed air provides anti-ice protection by heating engine intake cowling and is used as the motive power for engine thrust reversers.
- Bleed air is used to pressurize the cabin and provide air to the cabin conditioning environmental control system.
- Bleed air is used for ancillary functions such as pressurizing hydraulic reservoirs, rain dispersal, and water and waste systems.
Associated Aircraft Systems with Bleed Air
- Air conditioning (ATA Chapter 21)
- Cargo compartment heating (ATA Chapter 21)
- Wing and engine anti-icing (ATA Chapter 30)
- Engine start (ATA Chapter 80)
- Thrust reverser (ATA Chapter 78)
- Hydraulic reservoir pressurization (ATA Chapter 29)
- Rain repellent nozzles-aircraft windscreen (ATA Chapter 30)
- Water tank pressurization and toilet waste (ATA Chapter 38)
- Air driven hydraulic pump (ADP) (ATA Chapter 29)
Environmental Control Systems
- Kinetic heating occurs due to friction between the aircraft skin and air molecules.
- Skin temperatures can reach up to 1000°C or more in low-level flight at transonic speeds.
- Kinetic heat loads can be negative in subsonic cruise at altitude on a cold day, requiring heating.
- Leading edges of the aircraft feel the full effect of kinetic heating, reaching ram temperatures.
- Other surfaces are subject to slightly lower temperatures, termed recovery temperatures.
- Equations to calculate ram and recovery temperatures: Trec = Tamb (1+0.18M2) and Tram = Tamb (1+0.2M2)
Environmental Control System Components
- Ram air cooling
- Fuel cooling
- Engine bleed
- Bleed flow and temperature control
- Cooling systems
- Air cycle refrigeration systems
- Turbofan systems
- Bootstrap systems
Emergency Systems
- Designed to operate only in emergency situations.
- Impossible to test at the beginning of each flight, as they are essentially “dormant”.
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Description
This quiz provides a summary of Lecture No. 2 on Aircraft Systems Continuations, focusing on topics such as Pneumatic Systems, Environmental Control Systems, and Emergency Systems. It covers the use of high pressure bleed air in engines and the components associated with the bleed air extraction.
