New Hampshire CDL — Air Brakes: Safe Driving Practices Practice Test

Question 1

In an emergency, a driver manually adjusts an automatic slack adjuster as a temporary measure. What does the manual expect to happen to that brake afterward?

Accepted Answer

It will probably be out of adjustment again before long — The manual allows this only as a stopgap, because the procedure usually leaves the real cause of the adjustment problem unfixed. The brake is likely to drift out of adjustment again soon, so the vehicle still needs to go to a repair facility.

Answer

It will stay in adjustment until the next brake job

Answer

It will lock up the first time the brakes are applied hard

Answer

It will switch itself over to manual adjustment for good

Question 2

The hand check of S-cam slack adjusters starts with parking on level ground and chocking the wheels. Why are the chocks needed for this particular check?

Accepted Answer

The parking brakes are released for the check, so the chocks are what keep the vehicle from moving — You cannot move the slack adjusters while the parking brakes are applied, so the check is done with them released. With no parking brake holding the vehicle, level ground and wheel chocks are what stop it from rolling while you pull on each adjuster.

Answer

The chocks take the vehicle's weight off the slack adjusters

Answer

The chocks keep the air tanks level so the gauge reads true

Answer

The chocks hold the brake shoes against the drums

Question 3

Which of these air brake parts does the driver work from inside the cab?

Accepted Answer

The parking brake control — The parking brake control is in the cab and lets the driver release the air from the spring brakes so the springs apply. The safety relief valve sits in the first air tank the compressor fills, and the S-cam and slack adjuster are part of the brake at the wheel.

Answer

The safety relief valve

Answer

The S-cam

Answer

The slack adjuster

Question 4

The Air Brakes section spreads its extra checks across the seven-step inspection. Which of these is done in the Step 7 final air brake check, not in the Step 5 walk-around?

Accepted Answer

Timing the air leakage rate — Slack adjusters, drums or discs, linings and hoses are walk-around items. The air leakage rate test belongs to the final air brake check, together with the governor, low pressure warning, spring brake, pressure buildup, parking brake and service brake checks.

Answer

Pulling on the slack adjusters

Answer

Looking over brake drums and linings

Answer

Checking the air hoses at the brake chambers

Question 5

Two trucks both have alcohol evaporators. Truck A's air tanks have manual drain valves; Truck B's have automatic drain valves. Under the alcohol evaporator passage, which truck still needs its tanks drained by the driver every day?

Accepted Answer

Truck A only — The evaporator only lowers the risk of ice in the valves and other parts. The manual says daily tank drainage is still needed to remove water and oil, with one exception: systems that have automatic drain valves.

Answer

Truck B only

Answer

Both trucks

Answer

Neither truck, because the alcohol removes the water

Question 6

The figure 55 psi turns up several times in the Air Brakes section. Which of these is NOT tied to 55 psi?

Accepted Answer

The minimum pressure to build in both halves of a dual system before driving — Before driving a dual-system vehicle you let the compressor build at least 100 psi in both the primary and secondary systems. The 55 psi figure belongs to the low air warning, the wig wag, and the application pressure at which automatic front wheel limiting valves stop reducing front brake air.

Answer

The tank pressure before which the low air warning must come on

Answer

The system pressure below which a wig wag drops into view

Answer

The application pressure at which automatic front limiting valves stop cutting air to the front brakes

Question 7

Wedge brakes and S-cam brakes use different mechanisms. What does the manual's description show they have in common?

Accepted Answer

Both force brake shoes against the inside of a brake drum — In an S-cam brake the cam spreads the shoes; in a wedge brake the push rod drives a wedge between the shoe ends. Either way the shoes end up pressed against the drum from inside. The power screw, caliper and pads belong to disc brakes, and only some wedge brakes are self-adjusting.

Answer

Both use a power screw to clamp a rotor

Answer

Both rely on a caliper with lining pads

Answer

Both are self-adjusting on every vehicle

Question 8

Why does the manual say an air brake system includes a stop light switch?

Accepted Answer

Because drivers behind you have to be warned when you brake — The switch is electric but is operated by air pressure. When you apply the air brakes it turns the brake lights on, which is how following drivers learn that you are slowing.

Answer

Because the low air warning needs a second lamp

Answer

Because the compressor must shut off during braking

Answer

Because the parking brake knob needs a dash indicator

Question 9

A drum brake stops the vehicle by pressing its shoes and linings outward on the drum. Besides slowing the vehicle, what does the manual say the resulting friction creates?

Accepted Answer

Heat — Friction between the linings and the drum is what slows the vehicle, and it produces heat as it does so. How much a drum can take depends on the force and duration of braking, and excessive heat can leave the brakes not working.

Answer

Extra air pressure in the tanks

Answer

Moisture in the brake chambers

Answer

Slack in the push rods

Question 10

The manual names the two halves of a dual air brake system "primary" and "secondary." Which name does it give the half that typically works the rear-axle brakes?

Accepted Answer

Primary — The manual describes one system that typically operates the rear-axle brakes and another that covers the front axle, and sometimes one of the rear axles too. It then names the first of those the primary system and the other the secondary system.

Answer

Secondary

Answer

Neither; both halves work every axle equally

Answer

Whichever half shows the higher gauge reading

Question 11

One of the two air leakage tests in the Step 7 check times the pressure drop with your foot off the brake. Which of these is NOT part of setting it up?

Accepted Answer

Holding the foot brake fully applied — For that test you charge the system fully, shut the engine off, release the parking brake and time the drop. Fully applying and holding the foot brake belongs to the other leakage test, which has its own, slightly higher limits.

Answer

Starting with a fully charged air system

Answer

Turning the engine off

Answer

Releasing the parking brake

Question 12

Step 3 of the seven-step inspection in Section 2 has you look at the gauges once the engine is running. What does it say about the air pressure gauge?

Accepted Answer

It should climb from 50 psi to 90 psi in no more than 3 minutes, and you go on building to governor cut-out — Section 2 lists air pressure among the gauges to watch after start-up: it should go from 50 psi up to 90 psi inside 3 minutes, and you then keep building until the governor cuts out, which is usually somewhere in the 120 to 140 psi range. It also tells you to know your own vehicle's requirements.

Answer

It should hold steady at 55 psi while the engine idles

Answer

It should reach 150 psi before you release the parking brake

Answer

It should drop 3 psi each minute until the engine warms up

New Hampshire CDL — Air Brakes: Safe Driving Practices practice test

Study questions with answers

1. In an emergency, a driver manually adjusts an automatic slack adjuster as a temporary measure. What does the manual expect to happen to that brake afterward?

2. The hand check of S-cam slack adjusters starts with parking on level ground and chocking the wheels. Why are the chocks needed for this particular check?

3. Which of these air brake parts does the driver work from inside the cab?

4. The Air Brakes section spreads its extra checks across the seven-step inspection. Which of these is done in the Step 7 final air brake check, not in the Step 5 walk-around?

5. Two trucks both have alcohol evaporators. Truck A's air tanks have manual drain valves; Truck B's have automatic drain valves. Under the alcohol evaporator passage, which truck still needs its tanks drained by the driver every day?

6. The figure 55 psi turns up several times in the Air Brakes section. Which of these is NOT tied to 55 psi?

7. Wedge brakes and S-cam brakes use different mechanisms. What does the manual's description show they have in common?

8. Why does the manual say an air brake system includes a stop light switch?

9. A drum brake stops the vehicle by pressing its shoes and linings outward on the drum. Besides slowing the vehicle, what does the manual say the resulting friction creates?

10. The manual names the two halves of a dual air brake system "primary" and "secondary." Which name does it give the half that typically works the rear-axle brakes?

11. One of the two air leakage tests in the Step 7 check times the pressure drop with your foot off the brake. Which of these is NOT part of setting it up?

12. Step 3 of the seven-step inspection in Section 2 has you look at the gauges once the engine is running. What does it say about the air pressure gauge?

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