BC Air Brake Exam Flashcards

Q: How many questions are on the ICBC air brake knowledge test?

ICBC's knowledge-test tip sheet lists the air brake knowledge test as 25 multiple-choice questions, requiring 20 correct answers (80%) to pass, with a 45-minute maximum time limit.

Q: What happens if I fail the air brake knowledge test?

ICBC's standard retest waiting period for knowledge tests is 7 days. If an applicant fails the air brake knowledge test after three total attempts, ICBC requires completing or repeating an approved 7-hour air brake training course before testing again.

Q: What pressure does the low-air warning device activate at?

ICBC's Driving Commercial Vehicles guide states the low-air warning device must come on when air pressure drops below 60 psi (414 kPa).

Q: How long is the air brake knowledge test result valid?

ICBC states air brake knowledge test results are valid for one year. If the endorsement isn't placed on the licence within that year, the test must be retaken.

Question 1

Why are air brakes used on heavy commercial vehicles instead of hydraulic brakes?

Accepted Answer

Compressed air can generate very high braking force for heavy loads, and the compressor continuously replenishes the air supply, unlike a fixed hydraulic fluid volume.

Question 2

What are the basic components of a simple air brake system?

Accepted Answer

A compressor with a governor to control it, air lines, a reservoir to store compressed air, a foot valve (brake pedal) to direct air to the brakes, and foundation brakes to apply mechanical force.

Question 3

How does an air-over-hydraulic braking system work, and what B.C. licence does it require?

Accepted Answer

Air pressure actuates a hydraulic pressure intensifier, and hydraulic pressure then applies the foundation brakes. Most air-over-hydraulic vehicles require a B.C. air brake endorsement (code 15), just like fully air-braked vehicles.

Question 4

How fast must the compressor build reservoir pressure from 50 to 90 psi, and at what engine speed?

Accepted Answer

Within three minutes, at a fast idle of about 1,000 to 1,200 rpm, per ICBC's Driving Commercial Vehicles guide.

Question 5

What is the typical operating pressure range for an air brake system, and what is the governor's job?

Accepted Answer

Most systems operate at a maximum of about 125 psi (range 105-135 psi across vehicles). The governor stops ("unloads") the compressor once maximum pressure is reached and restarts it once pressure drops enough, keeping roughly a 20 psi spread between cut-out and cut-in.

Question 6

At what pressure must the governor restart (cut in) the compressor at the latest?

Accepted Answer

The governor must cause the compressor to resume building air before pressure drops below 80 to 85 psi.

Question 7

What does the safety (pop-off) valve protect against, and at what pressure does it vent?

Accepted Answer

It protects reservoirs from bursting if the governor fails to unload the compressor. It is normally set to vent excess pressure at approximately 150 psi. If it releases, the governor or compressor needs service.

Question 8

Why is the first (supply) reservoir called the "wet tank"?

Accepted Answer

Compressed air from the compressor carries water vapour, oil mist, and carbon particles; most contaminants condense and settle in the supply reservoir before air moves on to the primary and secondary reservoirs.

Question 9

In a dual air brake system, which axle brakes does the primary circuit usually control, and which does the secondary control?

Accepted Answer

The primary section (closest to the pedal in the dual foot valve) usually operates the drive (rear) axle brakes. The secondary section usually operates the steering (front) axle brakes.

Question 10

What keeps a primary or secondary reservoir from losing its air if there's a failure upstream (such as a ruptured compressor discharge line)?

Accepted Answer

A one-way check valve between the supply reservoir and each service reservoir allows air to flow in only one direction, preventing the primary and secondary reservoir air from flowing backward and being lost.

Question 11

At what pressure must the low-air warning device activate?

Accepted Answer

Below 60 psi (414 kPa), per ICBC's Driving Commercial Vehicles guide. The warning may activate above 60 psi on some systems, but it must not activate later than 60 psi.

Question 12

If reservoir pressure is only 80 psi, what is the maximum service brake application pressure the system can deliver?

Accepted Answer

No more than the 80 psi available in the reservoir — brake application pressure can never exceed the pressure stored in the reservoir supplying it.

Question 13

At what pressure range may spring parking brakes begin to drag, and at what range may they automatically fully apply?

Accepted Answer

Spring brakes may begin to drag below about 60 psi and may automatically fully apply at about 20 to 45 psi, depending on the system.

Question 14

Where are spring parking brakes commonly mounted on a truck or bus?

Accepted Answer

On the rear axles only — not on the steering axle — in the common spring parking brake arrangement.

Question 15

What must be done before manually caging a spring parking brake?

Accepted Answer

Block the wheels first, because caging mechanically removes the spring's parking force at that wheel and the vehicle could roll.

Question 16

What happens to a trailer's spring parking brakes during a breakaway that ruptures the air supply line?

Accepted Answer

Loss of supply-line pressure causes the trailer spring brake valve to exhaust air from the spring brake chambers, automatically applying the trailer's spring parking brakes.

Question 17

What are "foundation brakes"?

Accepted Answer

The mechanical wheel-end brake parts operated by the air system: brake chambers, pushrods, slack adjusters, drums or rotors, and linings or pads.

Question 18

What does the slack adjuster do on an s-cam drum brake?

Accepted Answer

It acts as a lever between the pushrod and the s-cam, rotating the s-cam to apply the brake, and it also serves as the adjustment point used to keep pushrod travel within tolerance.

Question 19

Using the pry method, what is a good free-stroke range, and what measurement means the brake needs adjustment?

Accepted Answer

1/2 to 3/4 of an inch (12-20 mm) is a good range. More than 3/4 of an inch (20 mm) means the brake needs adjustment.

Question 20

Using the applied stroke method (full brake application), what is a good stroke range, and what measurement means the brake needs adjustment?

Accepted Answer

1 to 1 1/2 inches (25-38 mm) is a good range, measured at a full application of 90 to 100 psi. More than 1 3/4 inches (45 mm) means the brake needs adjustment.

Question 21

For a typical Type 30 chamber with an automatic slack adjuster, what applied-stroke measurement means the brake needs repair?

Accepted Answer

More than two inches (50 mm) — automatic slack adjusters normally run slightly longer strokes than well-adjusted manual ones, but stroke beyond this limit means the adjuster has failed, is misinstalled, or there is another foundation brake problem.

Question 22

How much pushrod force does a typical Type 30 brake chamber develop at 100 psi?

Accepted Answer

About 3,000 pounds, based on roughly 30 square inches of effective diaphragm area on a regular Type 30 clamp-type chamber.

Question 23

Why is repeatedly manually adjusting an automatic slack adjuster dangerous?

Accepted Answer

It can temporarily shorten stroke while masking an underlying installation, wear, or foundation brake problem that actually needs qualified repair, creating a false sense of security.

Question 24

How does brake fade develop from repeated hard braking, according to ICBC's guide?

Accepted Answer

Heavy or repeated braking overheats the brakes; hot brake drums expand away from the linings, reducing contact and braking force, so the vehicle takes longer to stop or may not stop at all.

Question 25

What does the tractor protection system do if a trailer breaks away or an air line ruptures?

Accepted Answer

It closes off the trailer air loss so the tractor's own air supply is protected, allowing the tractor to still make a safe stop.

Question 26

Why can a bobtail tractor (no trailer attached) lock its drive axle brakes easily?

Accepted Answer

Without a trailer, there is very little weight over the rear drive axles, so relatively light brake applications can lock the rear wheels.

Question 27

What precaution is required for a parked trailer that has relay emergency brakes but no spring parking brakes?

Accepted Answer

The trailer's wheels must be blocked, because small leaks can reduce or deplete the applied service-brake air pressure holding the trailer, letting it roll away.

Question 28

When a driver makes a 20 psi foot-valve application, what control signal does the trailer's relay system normally receive?

Accepted Answer

Approximately the same 20 psi signal — during normal service braking, the trailer receives a control signal roughly equal to the driver's application pressure.

Question 29

What is the purpose of the tug test during a Class 1 pre-trip inspection?

Accepted Answer

Gently tugging against the applied tractor or trailer parking brakes in low gear confirms the brakes actually hold the combination before the vehicle is driven.

Question 30

How should a driver brake during an emergency stop in an ABS-equipped air brake vehicle?

Accepted Answer

Apply and maintain firm, continuous brake pressure so the ABS system can modulate individual wheel pressure and help preserve steering control.

Question 31

If the ABS warning lamp stays on after the normal self-check or comes on while driving, what does that mean?

Accepted Answer

The anti-lock feature has a fault and is disabled, but normal service braking remains available. The vehicle needs service.

Question 32

What does Automatic Traction Control (ATC) add to a vehicle that already has ABS?

Accepted Answer

ATC uses wheel-speed sensors to detect drive-wheel loss of traction; it can apply the brake on a spinning wheel and, in very slippery conditions, reduce engine power to help the wheels regain grip.

Question 33

What are the four components of total stopping distance/time for a commercial vehicle?

Accepted Answer

Perception time + reaction time + brake lag time + braking time. Perception and reaction are each about 3/4 second; add brake lag time and the braking distance itself.

Question 34

What is "brake lag time" for air brakes, and how does it compare to hydraulic car brakes?

Accepted Answer

Brake lag is the roughly 4/10 of a second delay between pressing the brake pedal and the air brakes actually beginning to function. Hydraulic car brakes begin working almost instantly, so air brakes need extra following distance.

Question 35

What gear rule does ICBC give for descending a hill in a commercial vehicle?

Accepted Answer

Use a lower gear to go down the hill than the gear that was used to climb it; never shift to a higher gear on a downgrade unless speed can be controlled by a retarder or engine compression.

Question 36

What is the main purpose of an engine retarder (engine brake) on a heavy vehicle?

Accepted Answer

To provide auxiliary slowing, such as controlling speed on long downgrades, without relying on the main air brake system, saving the main brakes for emergency stopping.

Question 37

What is "brake fade" as defined by ICBC's guide?

Accepted Answer

A condition where the brakes stop working properly because they are overheated, causing the vehicle to take longer to stop or possibly not stop at all.

Question 38

What should a driver do after driving through deep water or in extremely wet conditions to restore brake effectiveness?

Accepted Answer

Apply slight, continuous brake pressure for a short distance while driving to help dry out the brakes before relying on them fully.

Question 39

When is an air brake pre-trip inspection required for a commercial vehicle?

Accepted Answer

Before the vehicle's first trip of the day, as part of the required daily pre-trip inspection; covered commercial vehicles also need a written trip inspection report.

Question 40

For a Class 1 tractor-trailer combination with one trailer, what is the maximum air loss allowed during the one-minute full brake application leakage test, after the initial pressure drop?

Accepted Answer

No more than 4 psi per minute, with the full brake application held at 90 to 100 psi and no audible air leaks.

Question 41

For a Class 1 combination with two trailers, what is the maximum allowed air loss during the same one-minute applied leakage test?

Accepted Answer

No more than 6 psi per minute after the initial pressure drop.

Question 42

For a single-unit vehicle (Class 3, no trailer), what is the maximum allowed air loss during the one-minute full brake application leakage test?

Accepted Answer

No more than 3 psi per minute after the initial pressure drop.

Question 43

How does the pre-trip procedure check that the governor cuts in (restarts the compressor) at the correct pressure?

Accepted Answer

Pump the brakes down to about 80% of maximum system pressure (for example, 100 psi if maximum is 125 psi) and confirm air pressure begins to build again; the compressor must cut in before pressure falls below 80 psi.

Question 44

Why should you check for air leaks with the engine off during a pre-trip inspection?

Accepted Answer

With the engine off, the compressor is not adding air, so any hissing or audible leaks in the air brake system can be heard and located clearly.

Question 45

What endorsement code does B.C. use for most air-brake-equipped, on-highway commercial vehicles?

Accepted Answer

Code 15, ICBC's air brake endorsement, required for most on-highway air-brake-equipped vehicles and most air-over-hydraulic vehicles.

Question 46

What is the format of ICBC's air brake knowledge test?

Accepted Answer

25 multiple-choice questions, 20 correct answers needed to pass (80%), with a 45-minute maximum time allotment.

Question 47

What is the minimum length of an ICBC-approved air brake theory course?

Accepted Answer

7 hours of classroom theory on air brake systems; a certified course adds about 4 hours of practical pre-trip training on top of that.

Question 48

What happens if an applicant fails the air brake knowledge test three times?

Accepted Answer

ICBC requires the applicant to complete or repeat an approved 7-hour air brake training course before attempting the knowledge test again. ICBC's standard knowledge-test retest wait is 7 days after any unsuccessful attempt.

Question 49

For a single-unit on-highway air brake endorsement in B.C., what testing does ICBC require, and what is not required?

Accepted Answer

Approved course completion or qualifying experience, the air brake knowledge test, and an air brake pre-trip inspection test are required. A separate road test is not required for this endorsement path.

Question 50

How long is an ICBC air brake knowledge test result valid if the endorsement hasn't been placed on the licence?

Accepted Answer

One year. If the air brake endorsement isn't placed on the driver's licence within one year of passing the knowledge test, it must be retaken.

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