Chapter 2a: Air Supply Subsystem

The “Air Supply Subsystem” chapter in the Ontario air brake test manual details the components and functions critical to generating and maintaining air pressure in air brake systems.

Ontario Air Brake Test - Chapter 2a: Air Supply Subsystem

1 / 30

What is the purpose of a one-way check valve in the air system?

To prevent air from flowing back into the supply tank

To cool the compressed air

To mix oil with the air

To drain moisture automatically

2 / 30

What is “cut-out” pressure?

The air pressure at which the compressor starts pumping air

The pressure required to release the parking brakes

The air pressure at which the compressor stops pumping air

The maximum pressure a tank can ever hold

3 / 30

What are the primary and secondary tanks collectively called?

Emergency tanks

Dual-service tanks

Relay tanks

Reservoir tanks

4 / 30

What should a driver do if air pressure drops below the normal cut-in setting while driving?

Open all tank drain valves while moving

Immediately shut off the engine on the road

Ignore it and continue driving

Bring the vehicle to a safe stop as soon as possible

5 / 30

Why must air tanks be drained regularly?

To remove accumulated moisture and oil

To cool the tanks

To refill them with fresh air

To reduce air pressure for parking

6 / 30

Who should verify abnormal air pressure readings with an accurate gauge?

Any other driver

A qualified technician

A fuel station attendant

The driver’s supervisor

7 / 30

What is the main purpose of the air-supply subsystem in an air brake system?

To produce, store, and manage compressed air for the brake system

To increase fuel efficiency

To cool the engine while braking

To lubricate brake components

8 / 30

Which is one problem caused by moisture and oil collecting in the air brake system?

Tires will wear more evenly

Sludge can form and cause valves to stick

The compressor will run quieter

Fuel consumption will decrease

9 / 30

How often do many manufacturers recommend draining the vehicle’s air tanks?

Only during annual inspections

Monthly

Weekly

Daily

10 / 30

What is the minimum allowable actual cut-in pressure in an air brake system?

345 kPa (50 psi)

690 kPa (100 psi)

552 kPa (80 psi)

414 kPa (60 psi)

11 / 30

What is the maximum allowable actual cut-out pressure in an air brake system?

828 kPa (120 psi)

552 kPa (80 psi)

1000 kPa (145 psi)

900 kPa (130 psi)

12 / 30

In what order should the air tanks be drained?

Secondary tank first, then primary, then supply

Supply (wet) tank first, then the others

Primary tank first, supply tank last

Any tank first; order does not matter

13 / 30

Why can moisture in the brake system be especially dangerous in cold temperatures?

It can overheat the compressor

It can freeze and may cause brake failure

It can melt seals

It can overinflate the tires

14 / 30

What is the main function of the air dryer?

To reduce the amount of moisture that passes into the air brake system

To warm the air before it reaches the brakes

To control cut-in and cut-out pressures

To store additional compressed air

15 / 30

Why is the first tank often called a “wet” tank?

It is filled with coolant

It collects most of the moisture and oil that drop out of the air

It is not pressurized

It is mounted near the wheels

16 / 30

What are air tanks primarily used for in an air brake system?

To cool the engine

To store fuel vapour

To store compressed air from the compressor

To store hydraulic fluid

17 / 30

Why are the primary and secondary tanks called “dry” tanks?

They are not pressurized

They are made of non-corrosive material

They do not receive any air

They collect less moisture than the supply or “wet” tank

18 / 30

What is the function of the governor in the air brake system?

To control when the compressor stops and starts pumping air

To apply the wheel brakes

To store compressed air

To remove moisture from the air

19 / 30

What is the main safety advantage of having dual-service (primary and secondary) circuits?

It allows the use of smaller tires

It reduces the need for air dryers

It eliminates the need for a governor

If one circuit fails, the other can still provide enough brake function to stop the vehicle

20 / 30

Normally, cut-out pressure is how much higher than cut-in pressure?

207 to 241 kPa (30 to 35 psi)

34 to 69 kPa (5 to 10 psi)

276 to 310 kPa (40 to 45 psi)

138 to 173 kPa (20 to 25 psi)

21 / 30

How is the air compressor powered on most vehicles?

By a separate electric motor

By the battery only

By the vehicle’s engine

By the starter motor

22 / 30

What is “cut-in” pressure?

The pressure at which the drain valves open automatically

The air pressure at which the compressor starts pumping air again

The air pressure at which the compressor stops pumping air

The minimum tank volume

23 / 30

What component produces compressed air for the brake system?

Wet tank

Air compressor

Air dryer

Governor

24 / 30

Where is an air dryer located in the air brake system?

Between the primary and secondary tanks

Next to the governor inside the cab

Between the air compressor and the supply tank

After the wet tank but before the dry tanks

25 / 30

If a vehicle is equipped with an air dryer, what maintenance task is still required?

No further maintenance is needed

Regular draining of the air tanks

Daily tightening of compressor belts

Regular draining of engine coolant

26 / 30

What is the first tank the compressed air enters from the compressor?

Primary service tank

Supply or “wet” tank

Secondary service tank

Relay tank

27 / 30

Why does moisture collect in the air tanks?

Because the tanks are filled with coolant

Because water is added to cool the air

Because moisture in the intake air condenses as the air is compressed

Because the dryer injects water into the system

28 / 30

When should a vehicle be driven according to the air brake system pressure?

Any time the compressor is running

Only when the governor is at cut-out

Only when the supply tank is empty

Only when air pressure is in the normal operating range

29 / 30

What is the typical normal operating pressure range of an air brake system?

About 690 to 828 kPa (100 to 120 psi)

About 207 to 276 kPa (30 to 40 psi)

About 345 to 414 kPa (50 to 60 psi)

About 900 to 1100 kPa (130 to 160 psi)

30 / 30

What are air tanks usually made of and how are they shaped?

Steel cylinders with domed ends

Rubber-coated boxes

Aluminum cubes

Plastic spheres

Your score is

This section explains how the compressor draws air, which is then stored in reservoirs for use in braking. It covers the roles of the governor, air dryer, and safety valves in regulating and protecting the system. Drivers learn the importance of draining reservoirs to remove moisture and contaminants, which helps prevent brake failure. Understanding the air supply subsystem is essential for passing the Ontario air brake test and for ensuring reliable, safe vehicle operation.