AGK - Pneumatics

Cabin Heating:

Piston Aircraft: Ram Air + heat exchanger

Turbine: Bleed air + compresor

Bleed Air - Isolation Value

Usually a left and right pack, these are usually separate in normal operation, but connected via isolation valve
Which can open to connect the two systems in abnormal situations.

Isolation valve is normally closed, opens when there is a pressure difference or when the system is off.

Cabin Air - Taken from the HP Compressor

Ram Air Inlet Valve:

Regulates the flow of ram air

Sources of Pressurisation:

• super charger

• turbo charger

• compressor

Electric Pneumatic System

• Benefit includes increased efficiency and reduced fuel consumption

• less weight

• more range

• improved reliability
  
  NOT The answer:

• Shorter take off run (even though it does make sense)

Bleed Air Pressure Gauge:

Is bleed air relative to the atmospheric static pressure.

In Pistion Aircraft, the pneumatic system can be used by:

• Cabin Heating

• De-icing

• Gyroscopic Instrument

Bleed air Duct Leaks Indications

What indication to pilot: - Bleed duct leak indicator light

What indication in the CABIN: Reduced airflow from vents.

Pressurisation Relief Valves

• Positive / Safety Valve - Prevents over pressure

• Negative / inward relief valve -

What regulates the cabin pressure?

The outflow valve, can be automatically or manually controlled.
Outflow valve maintains pressurisation

Cabin Altitude Warning:

Triggers around 10,000ft (think oxygen required)

Air Cycle / Bootstrap Machine (same thing)

The main function is to cool incoming air.

Bleed air → Primary Heat Exchanger
→ Compressor → Secondary Heat Exchanger
→ Explanded → Turbine Section → Water Removed → Humidifyer → Cabin

Max Pressure Differential

5-10PSI
5-7 on turbo prop
8-9 on a jet

Pre-Pressurisation:

The aircraft begins to pressurise on the ground, during startup / taxi

so there isn’t a big pressure jump on take off.