PC-21 Environmental Control System (ECS) Flashcards
What is the purpose of the ECS?
1) Cockpit air temp
2) Humidity
3) pressure
4) Provide conditioned are to the avionics bay
5) Provides bleed air to OBOGS
6) Bleed air to Anti-g system
What are the 7 subsystems of the ECS?
1) Engine bleed air distribution
2) Air Cycle System (ACS)
3) Vapor Cycle System (VCS)
4) Cockpit air distribution
5) Cabin Pressurization Control System (CPCS)
6) Ram air system
What is the purpose of the engine bleed air distribution?
Supplies hot compressed bleed air that is tapped off two high pressure or low pressure ports, depending on engine power setting.
What two distinct routes does engine bleed air supply take?
1) To the Air Cycle System (ACS) which supplies air for heating, cooling and pressurization
2) To the Oxygen and Anti-g systems
What is pressure for ACS decreased to? How is this controlled?
- 20 +- 3 psi
- Controlled by overpressure and over-temperature switches
Which pressure bleed air line is the Oxygen and Anti-g supplied from?
High pressure section
What is the function of the ACS?
Control the temperature of the bleed air passing through it to a value determined by the IECS controller
How is airflow from ACS separated?
- Part is cooled in the refrigeration pack
- Other part bypasses refrigeration pack and it mixed with the cooled air before entering water separator
How is air cooled in the refrigeration pack?
- In a heat exchanger by flow of ram air
- By expansion by flowing through a turbine
What controls the mixture ratio of hot and cooled air?
- IECS controller
- This is controlled by the temperature selector on the front cockpit ECS panel.
What occurs once hot and cooled air has been mixed?
Dried in the water separator and then enters the cockpit air distribution through the firewall shut off valve.
What does the VCS do?
Augments the ACS in hot weather conditions by passing cockpit air through an evaporator and heat exchanger that is cooled by refrigerant gas
What prevents ice formation on the cockpit and avionics bay evaporators?
Hot gas bypass valves
What is the function of the cockpit air distribution?
To allow the pilot to control the quantity and direction of conditioned air coming from the ACS and VCS.
What does the Y separator valve do? How is it controlled in the cockpit?
- Directs flow to demisting transparencies
- Pilots feet
- Controlled by Y-separator valve by means of the AIR SUPPLY lever on the centre pedestal in each cockpit.
How can cooled air from the VCS be controlled?
By the air vents in the centre pedestal in each cockpit.
What must the pilot do for max defogging?
Close the air vents on the centre pedestal, so that the VCS evaporator fan can augment the ACS defog.
What is the function of the Cabin Pressure Control System (CPCS)?
Automatically control the pressure in the cockpit by adjusting the outflow of the air from the cabin through the cabin pressure control valve.
- Fully automatic
What does the cabin pressure control valve do?
- Interfaces with the no.2 static pressure port and operates automatically to release conditioned air to the avionics bay at a rate that maintains cabin pressure at correct altitude.
What is max pressure differential? What altitude is this achieved at? What cabin altitude does it give?
- 3.76 psi
- Achieved at 25,000 ft
- Gives cabin altitude of 13,000 ft
What is provided as a safety feature for cockpit pressurisation?
Safety inward relief valve
What is the purpose of the ram air system?
- Provides a means to equalize the cabin pressure with ambient pressure and to ventilate the cockpit with fresh air.
- Normally held closed by the pressure of servo air drawn from ACS air supply.
How can pilot control the RAM air system?
Using cabin pressure selector on the front cockpit ECS panel.
What does the IECS do?
Automatically regulates the cockpit temperature by adjusting the delivery temperatures of the ACS and the VCS to maintain the temperature set by the temperature selector on the front cockpit ECS panel
