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 “cut-in” pressure?

The air pressure at which the compressor starts pumping air again

The minimum tank volume

The air pressure at which the compressor stops pumping air

The pressure at which the drain valves open automatically

2 / 30

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

414 kPa (60 psi)

345 kPa (50 psi)

690 kPa (100 psi)

552 kPa (80 psi)

3 / 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

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

It eliminates the need for a governor

4 / 30

How is the air compressor powered on most vehicles?

By the starter motor

By the battery only

By the vehicle’s engine

By a separate electric motor

5 / 30

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

To mix oil with the air

To cool the compressed air

To drain moisture automatically

To prevent air from flowing back into the supply tank

6 / 30

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

It can freeze and may cause brake failure

It can overinflate the tires

It can overheat the compressor

It can melt seals

7 / 30

Why must air tanks be drained regularly?

To cool the tanks

To remove accumulated moisture and oil

To reduce air pressure for parking

To refill them with fresh air

8 / 30

What component produces compressed air for the brake system?

Air compressor

Air dryer

Governor

Wet tank

9 / 30

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

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

It is filled with coolant

It is mounted near the wheels

It is not pressurized

10 / 30

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

About 690 to 828 kPa (100 to 120 psi)

About 345 to 414 kPa (50 to 60 psi)

About 900 to 1100 kPa (130 to 160 psi)

About 207 to 276 kPa (30 to 40 psi)

11 / 30

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

Any time the compressor is running

Only when the supply tank is empty

Only when the governor is at cut-out

Only when air pressure is in the normal operating range

12 / 30

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

34 to 69 kPa (5 to 10 psi)

276 to 310 kPa (40 to 45 psi)

207 to 241 kPa (30 to 35 psi)

138 to 173 kPa (20 to 25 psi)

13 / 30

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

Fuel consumption will decrease

Tires will wear more evenly

Sludge can form and cause valves to stick

The compressor will run quieter

14 / 30

Why does moisture collect in the air tanks?

Because the tanks are filled with coolant

Because the dryer injects water into the system

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

Because water is added to cool the air

15 / 30

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

900 kPa (130 psi)

552 kPa (80 psi)

1000 kPa (145 psi)

828 kPa (120 psi)

16 / 30

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

A qualified technician

The driver’s supervisor

Any other driver

A fuel station attendant

17 / 30

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

To store compressed air from the compressor

To store fuel vapour

To cool the engine

To store hydraulic fluid

18 / 30

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

Relay tank

Primary service tank

Supply or “wet” tank

Secondary service tank

19 / 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

20 / 30

In what order should the air tanks be drained?

Any tank first; order does not matter

Primary tank first, supply tank last

Secondary tank first, then primary, then supply

Supply (wet) tank first, then the others

21 / 30

What are the primary and secondary tanks collectively called?

Relay tanks

Dual-service tanks

Emergency tanks

Reservoir tanks

22 / 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

23 / 30

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

They are made of non-corrosive material

They are not pressurized

They do not receive any air

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

24 / 30

What is the main function of the air dryer?

To control cut-in and cut-out pressures

To warm the air before it reaches the brakes

To store additional compressed air

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

25 / 30

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

Monthly

Only during annual inspections

Daily

Weekly

26 / 30

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

Plastic spheres

Steel cylinders with domed ends

Aluminum cubes

Rubber-coated boxes

27 / 30

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

Next to the governor inside the cab

Between the primary and secondary tanks

Between the air compressor and the supply tank

After the wet tank but before the dry tanks

28 / 30

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

Bring the vehicle to a safe stop as soon as possible

Ignore it and continue driving

Open all tank drain valves while moving

Immediately shut off the engine on the road

29 / 30

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

To remove moisture from the air

To apply the wheel brakes

To store compressed air

To control when the compressor stops and starts pumping air

30 / 30

What is “cut-out” pressure?

The pressure required to release the parking brakes

The air pressure at which the compressor starts pumping air

The maximum pressure a tank can ever hold

The air pressure at which the compressor stops pumping air

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.