Environmental Control System (ECS) Introduction

Question 1

What does the ECS consist of?

Answer 1

1) Aircraft cabin pressurization
2) Air-conditioning
3) Avionics cooling
4) Fuel tank pressurization
5) Anti-icing and defogging
6) Rain removal

Question 2

What is the purpose of the pressurization system? What is in each cockpit to determine this?

Answer 2

• Primary purpose if to maintain the cabin pressure at an altitude below 10,000 ft.
• Cabin altimeter

Question 3

What is the ACS?

Answer 3

• The ACS is the air conditioning system that operate in a wide range of thermal conditions, while also maintaining a suitable environment for the view, passengers and cargo.

Question 4

What are two methods to cool engine bleed air?

Answer 4

1) Air-Cycle System
- Air passing through the system’s turbine is expanded and cooled.
- Cooled air is then remixed with hot air that has bypassed the turbine, to achieve the desired cabin
temperature
2) Vapour-Cycle System
- Have greater cooling capacity that air-cycle systems and are generally used for ground operations in hot ambient conditions.

Question 5

What is rate of cabin change?

Answer 5

The rate of cabin change measured in feet per minute

Question 6

What is cabin differential?

Answer 6

Difference between atmospheric pressure and he cabin pressure within a pressurized aircraft

Question 7

What is fuel tank pressurisation?

Answer 7

Pressurization of the fuel tank

Question 8

What are 2 advantages of fuel tank pressurization?

Answer 8

1) Maintains a constant positive pressure which reduces the tendency for fuel to vaporize at lower atmospheric pressures
2) Reduces the amount of induced water contamination, due to the use of engine-bleed supply conditioned air
3) reduces the rate of fuel expansion and contraction associated with non-pressurized systems.

Question 9

How is cabin pressurization achieved?

Answer 9

The incorporation of an airtight fuselage and the supply of large quantities of conditioned air, sourced predominantly from the compressor stage of the engines.

Question 10

What is the common compressor bleed air temperature and pressure?

Answer 10

200 C

30 psi

Question 11

What does the pressure relief and shutoff valve do?

Answer 11

Terminates supply in the event of:

1) Over-pressurization
2) Inlet air contamination
3) Take-off performance demands in extreme conditions

Question 12

What does the heat exchanger do?

Answer 12

Cools the hot bleed air

Question 13

What does the cabin altitude controller do?

Answer 13

Maintains the cabin altitude and rate of change by varying the position of the outflow valves to regulate airflow.

Question 14

What does the safety/dump valve do?

Answer 14

Ensure cabin differential pressure specifications are not exceeded due to abnormal operating conditions.

Question 15

What do the pressure reducing valve/regulating valves do in the ACS?

Answer 15

Match the supply of air to the demand.

Question 16

What do check valves do in the ACS?

Answer 16

Ensures the supply air travels in a single direction only

Question 17

What are the crossfeed valves used for?

Answer 17

To facilitate the transfer of air from an alternate source to an area normally serviced by a supply source

Question 18

What does the water separator do?

Answer 18

Removes moisture from the airstream through cyclonic separation

Question 19

What does the Air Cycle Machine (ACM) do?

Answer 19

Supply conditioned dehumidified air for the various ECS operations

Question 20

What are some advantages of the Air Cycle System?

Answer 20

• More effective utilization of ambient conditions
• Minimizes the weight and complexity of coolant-based refrigerant systems
• Reduction in associated system pressure enables lighter and less complex system construction
• Reduce maintenance
• Eliminates the toxicity and flammability issues associated with coolant-based systems

Question 21

What are some disadvantages of the Air Cycle System?

Answer 21

• Comparatively less efficient than vapor cycle coolant-based systems
• Can require augmentation during on-ground operations during extreme heat conditions

Question 22

What are the key components of a vapour cycle system?

Answer 22

1) Refrigerant
2) Refrigerant expansion (or Metering) Valve
3) Evaporator
4) Compressor
5) Discharge line
6) Condenser/Receiver
7) Oil Circulation

Question 23

What are the two main sections of a VCS system?

Answer 23

• Low pressure which commences at the expansion valve

- High pressure which commences at the compressor

Question 24

What is the most common supply for avionics cooling?

Answer 24

ECS air-cycle conditioning system which can be augmented by a range of alternate supplies such as ram air, liquid cooling or ground supply.

Question 25

For Cockpit Temperature Control, where is temperature normally monitored ?

Answer 25

1. The Cabin
   2 The Cockpit
2. Conditioned air ducts
3. Distribution air ducts

Question 26

What is the purpose of an OBIGGS (OnBoard Inert Gas Generation System)?

Answer 26

To remove oxygen from compressed air to allow for fuel tank pressurization with just nitrogen.

Question 27

What is used to cool aircraft cockpits and avionics on the ground?

Answer 27

• ECS airccyle
• Ram air
• Liquid cooling
• Ground supply

Question 28

Temperature control is achieved by a Temperature Control Valve, how does it control the temp?

Answer 28

Through the temperature controller

Question 29

What is another name for a vapour cycle system?

Answer 29

Closed system