Florida CDL — Air Brakes: Handling Emergencies Practice Test

Question 1

What normally keeps the powerful springs in spring brake chambers from applying the brakes while you drive?

Accepted Answer

Air pressure holding the springs back — Air pressure holds the springs compressed and the brakes released. If pressure is removed — by parking or by a leak — the springs apply the brakes mechanically.

Answer

Hydraulic fluid pressure

Answer

An electric solenoid lock

Answer

The slack adjuster ratchet

Question 2

Some vehicles have a modulating control valve — a dash lever with taper-graduated positions. What is it for?

Accepted Answer

Gradually applying the spring brakes to stop the vehicle if the service brakes fail — The modulating valve lets you apply the spring brakes gradually by hand: the farther you move the lever, the harder they apply. It is designed for controlled stops if the service brakes fail while driving.

Answer

Adjusting how quickly the compressor recharges the tanks

Answer

Balancing braking force between tractor and trailer

Answer

Setting the governor cut-out point from the cab

Question 3

Certain vehicles, such as buses, carry an extra air tank tied to dual parking control valves. Why is that tank there?

Accepted Answer

To free the spring brakes briefly so a stranded vehicle can be moved in an emergency — Losing the main air supply sets the spring brakes. Pushing the spring-loaded control in feeds air from that reserve tank and frees the brakes long enough to move the vehicle out of danger. The reserve holds only a few applications, so plan the move before you make it.

Answer

To feed extra air to the trailer brakes whenever the load is heavy

Answer

To keep the alcohol evaporator supplied during cold weather

Answer

To power the low air pressure buzzer after the engine shuts down

Question 4

What is the main cause of brake fade on a downhill run?

Accepted Answer

Excessive heat from using the brakes too much instead of engine braking — Relying on the service brakes instead of engine braking overheats the drums and shoes. Excessive heat reduces friction, and the brakes fade until they cannot slow the vehicle — sometimes permanently damaging them.

Answer

Moisture freezing inside the brake lines

Answer

Too much air pressure in the tanks

Answer

Driving with the front brake limiting valve in normal

Question 5

While driving a truck with a dual air brake system, pressure in one of the two systems falls dangerously low. What should you expect?

Accepted Answer

One end of the vehicle, front or rear, will brake at reduced power and your stop will take longer — Each half of a dual system serves different axles, so losing one half leaves part of the vehicle braking at reduced power and stretches your stopping distance. Bring the truck to a safe stop and have the fault repaired before you drive on.

Answer

The healthy system automatically doubles its pressure to make up the difference

Answer

Spring brakes clamp instantly on every axle of the truck

Answer

Braking is unaffected, because both systems draw from one shared tank

Question 6

You always drive a straight truck whose antilock system is working on every axle. In a genuine emergency stop, the handbook allows you to:

Accepted Answer

Push the brake pedal all the way down and keep it there — This is the one exception to braking exactly as you normally would. With antilock control functioning at each axle, maximum pedal pressure will not lock the wheels, so you can use everything the brakes have while keeping the ability to steer.

Answer

Pull the parking brake knob out while the truck is still rolling

Answer

Steer around the hazard first and brake only after the turn is finished

Answer

Select neutral so the wheels are free to keep turning

Question 7

The low air pressure warning light and buzzer come on while you are rolling down the interstate. Your first responsibility is to:

Accepted Answer

Stop and park in the safest place available as soon as you can — Stop and safely park as soon as possible. If the leak continues, the spring brakes will eventually apply themselves, and controlled braking may become impossible.

Answer

Continue to the next truck stop where a mechanic is available

Answer

Downshift and rely on engine braking for the rest of the trip

Answer

Pump the brake pedal to rebuild pressure

Question 8

The yellow ABS malfunction lamp stays lit after the start-up bulb check and is still on once you are rolling. What does that tell you?

Accepted Answer

Antilock protection may be gone at one or more wheels, though the normal brakes still work — A lamp that refuses to go out reports a fault in the antilock system, so one or more wheels may no longer be protected against lockup. Your ordinary air brakes keep working, so drive as you always have and get the system repaired soon.

Answer

The parking brakes are dragging and overheating

Answer

The governor has quit cycling the air compressor

Answer

The truck has no braking ability at all and must be towed

Question 9

A bad air leak drains your tractor's tanks while you are driving. What will happen once pressure falls into the 20–45 psi range?

Accepted Answer

The spring brakes will apply on their own — When air pressure gets low enough — typically 20 to 45 psi — the spring brakes apply on their own. That is why you must pull over and stop safely as soon as the low pressure warning first appears, while you still have braking control.

Answer

The compressor will switch to a backup tank automatically

Answer

The service brakes will grip harder than normal

Answer

Nothing changes until pressure reaches zero

Question 10

Why should you avoid pressing the brake pedal down while the spring brakes are applied?

Accepted Answer

The combined spring and air forces could damage the brakes — The forces of the springs and the service-brake air pressure can add together and damage the brakes. Many systems have anti-compounding protection, but you should not count on it.

Answer

It wastes fuel by loading the compressor

Answer

It could set off the low air pressure warning falsely

Answer

It will release the parking brake unexpectedly

Question 11

Using the proper braking technique on a long downgrade, you have reached your safe speed of 40 mph in a low gear. What comes next?

Accepted Answer

Brake firmly down to about 35 mph, release, and repeat when speed returns to 40 mph — Apply the brakes just hard enough to feel a definite slowdown and reduce speed to about 5 mph below your safe speed, then release. When speed climbs back to your safe speed, repeat the cycle.

Answer

Hold light, steady pedal pressure all the way to the bottom

Answer

Shift to a higher gear so the engine turns more slowly

Answer

Apply the parking brake in short bursts

Question 12

Your brakes stop working partway down a long mountain grade and there is an escape ramp ahead. What does the handbook say to do?

Accepted Answer

Use the escape ramp, since it can stop you with far less damage than a crash — Use an escape ramp if one is available. Ramps are built with loose material or an upgrade to stop a runaway vehicle, and any damage from using one is far less serious than a runaway crash.

Answer

Avoid the ramp because it will destroy the truck

Answer

Swerve gently from shoulder to shoulder to scrub off speed

Answer

Shift into neutral and coast until the grade levels out

Florida CDL — Air Brakes: Handling Emergencies practice test

Study questions with answers

1. What normally keeps the powerful springs in spring brake chambers from applying the brakes while you drive?

2. Some vehicles have a modulating control valve — a dash lever with taper-graduated positions. What is it for?

3. Certain vehicles, such as buses, carry an extra air tank tied to dual parking control valves. Why is that tank there?

4. What is the main cause of brake fade on a downhill run?

5. While driving a truck with a dual air brake system, pressure in one of the two systems falls dangerously low. What should you expect?

6. You always drive a straight truck whose antilock system is working on every axle. In a genuine emergency stop, the handbook allows you to:

7. The low air pressure warning light and buzzer come on while you are rolling down the interstate. Your first responsibility is to:

8. The yellow ABS malfunction lamp stays lit after the start-up bulb check and is still on once you are rolling. What does that tell you?

9. A bad air leak drains your tractor's tanks while you are driving. What will happen once pressure falls into the 20–45 psi range?

10. Why should you avoid pressing the brake pedal down while the spring brakes are applied?

11. Using the proper braking technique on a long downgrade, you have reached your safe speed of 40 mph in a low gear. What comes next?

12. Your brakes stop working partway down a long mountain grade and there is an escape ramp ahead. What does the handbook say to do?

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