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

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

Only when the supply tank is empty

Any time the compressor is running

Only when the governor is at cut-out

Only when air pressure is in the normal operating range

2 / 30

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

Daily

Monthly

Weekly

Only during annual inspections

3 / 30

What is the main function of the air dryer?

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

To control cut-in and cut-out pressures

To warm the air before it reaches the brakes

To store additional compressed air

4 / 30

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

Supply or “wet” tank

Relay tank

Secondary service tank

Primary service tank

5 / 30

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

It can overheat the compressor

It can melt seals

It can overinflate the tires

It can freeze and may cause brake failure

6 / 30

Why must air tanks be drained regularly?

To refill them with fresh air

To remove accumulated moisture and oil

To reduce air pressure for parking

To cool the tanks

7 / 30

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

The driver’s supervisor

A qualified technician

Any other driver

A fuel station attendant

8 / 30

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

828 kPa (120 psi)

552 kPa (80 psi)

900 kPa (130 psi)

1000 kPa (145 psi)

9 / 30

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

To store compressed air

To control when the compressor stops and starts pumping air

To apply the wheel brakes

To remove moisture from the air

10 / 30

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

Immediately shut off the engine on the road

Open all tank drain valves while moving

Ignore it and continue driving

Bring the vehicle to a safe stop as soon as possible

11 / 30

How is the air compressor powered on most vehicles?

By the vehicle’s engine

By a separate electric motor

By the starter motor

By the battery only

12 / 30

What is “cut-out” pressure?

The air pressure at which the compressor stops pumping air

The maximum pressure a tank can ever hold

The air pressure at which the compressor starts pumping air

The pressure required to release the parking brakes

13 / 30

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

The compressor will run quieter

Tires will wear more evenly

Sludge can form and cause valves to stick

Fuel consumption will decrease

14 / 30

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

552 kPa (80 psi)

690 kPa (100 psi)

345 kPa (50 psi)

414 kPa (60 psi)

15 / 30

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

It eliminates the need for a governor

It allows the use of smaller tires

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

It reduces the need for air dryers

16 / 30

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

They are not pressurized

They do not receive any air

They are made of non-corrosive material

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

17 / 30

What are the primary and secondary tanks collectively called?

Emergency tanks

Relay tanks

Dual-service tanks

Reservoir tanks

18 / 30

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

After the wet tank but before the dry tanks

Between the air compressor and the supply tank

Next to the governor inside the cab

Between the primary and secondary tanks

19 / 30

What is “cut-in” pressure?

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

The pressure at which the drain valves open automatically

20 / 30

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

Regular draining of engine coolant

Daily tightening of compressor belts

No further maintenance is needed

Regular draining of the air tanks

21 / 30

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

To store fuel vapour

To store hydraulic fluid

To cool the engine

To store compressed air from the compressor

22 / 30

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

It is filled with coolant

It is not pressurized

It is mounted near the wheels

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

23 / 30

What component produces compressed air for the brake system?

Air compressor

Air dryer

Wet tank

Governor

24 / 30

In what order should the air tanks be drained?

Primary tank first, supply tank last

Secondary tank first, then primary, then supply

Supply (wet) tank first, then the others

Any tank first; order does not matter

25 / 30

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

About 207 to 276 kPa (30 to 40 psi)

About 690 to 828 kPa (100 to 120 psi)

About 900 to 1100 kPa (130 to 160 psi)

About 345 to 414 kPa (50 to 60 psi)

26 / 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

27 / 30

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

Plastic spheres

Rubber-coated boxes

Steel cylinders with domed ends

Aluminum cubes

28 / 30

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

276 to 310 kPa (40 to 45 psi)

207 to 241 kPa (30 to 35 psi)

34 to 69 kPa (5 to 10 psi)

138 to 173 kPa (20 to 25 psi)

29 / 30

Why does moisture collect in the air tanks?

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

Because water is added to cool the air

Because the dryer injects water into the system

Because the tanks are filled with coolant

30 / 30

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

To cool the engine while braking

To increase fuel efficiency

To lubricate brake components

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

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.