# Driver Training - Air Brakes Study Questions Flashcards Preview

## HFD Recruit Training > Driver Training - Air Brakes Study Questions > Flashcards

Flashcards in Driver Training - Air Brakes Study Questions Deck (23)
1
Q
1. When should a low air pressure warning come on?
A

Will come on when pressure in the tanks fall below 60 psi

• Required on all vehicles with air brakes
• Or one half the compressor governor cutout pressure on older vehicles
• A “wig wag” is a mechanical arm that drops into view when the system pressure drops below 60 psi

Large buses
- Common for low pressure warning devices to signal at 80 to 85 psi

(5-4)

2
Q
1. When should the air compressor governor cut-in?
A

When the tank pressure falls to the cut-out level, around 100 psi
- The governor allows the compressor to start pumping again after “cut-in”

(5-1)

3
Q
1. When should the air compressor governor cut-out?
A

When the air tank pressure rises to the cut-out level, around 125 psi
- The governor stops the compressor from pumping air after reaching the “cut-out” position

(5-1)

4
Q
1. When testing air brakes, during fanning of brakes, when should the parking brake valve “pop out” or “close”?
A

?

5-7?

5
Q
1. What is the air loss rate for a single vehicle?
A

For Single Vehicles:
- Loss rate should be less than two (2) psi in one minute

Apply 90 or more psi with the brake pedal
- After initial pressure drop, if the air pressure falls more than three (3) psi in one min, the air loss rate is too much

For Combination Vehicles:

• Should be less than three (3) psi in one minute
• After application of 90+ psi, air pressure falling more than four (4) psi in one min, air loss rate is too much

(5-7)

6
Q
1. What are the maximum leakage rates (with brake pedal depressed) for a single vehicle?
A

Apply 90 or more psi with the brake pedal
- After initial pressure drop, if the air pressure falls more than three (3) psi in one min, the air loss rate is too much

(5-7)

7
Q
1. With dual air systems the air pressure should build?
A

Before driving a vehicle with a dual air system, allow time for the air compressor to build up to a minimum of 100 psi in both the primary and secondary systems.

(5-6)

8
Q
1. What is brake lag?
A

Time required for air to flow through the lines to the brakes

(5-9)

9
Q
1. What does the application pressure gauge show you?
A

Shows how much air pressure is being applied to the brakes

5-4

10
Q
1. What does the supply pressure gauge show you?
A

Shows how much pressure is in the air tanks

5-4

11
Q
1. What does the service brake system do?
A

Applies and releases the brakes when you use the brake pedal during normal driving

(5-1)

12
Q
1. What does the emergency brake do?
A

Uses parts of the service and parking brake systems to stop the vehicle in the event of a brake system failure

(5-1)

13
Q
1. What should you do if your low pressure signal comes on?
A

Stop and safely park your vehicle as soon as possible

5-10

14
Q
1. How much can a slack adjuster move?
A

Should not be able to move more than about one inch
where the push rod attaches to it

(5-6)

15
Q
1. Why must air tanks be drained?
A

Drain the tanks completely to remove any water and oil that has collected in the bottom of the tank

(5-2)

16
Q
1. What are spring brakes?
A

Spring brakes mechanically hold the emergency brakes and parking brakes of trucks, tractors, and buses

• Springs are held back by air pressure
• When pressure is removed, the springs put on the brakes

(5-5)

17
Q
1. What should you do if your low air pressure signal comes on when you are driving a vehicle with dual air tanks?
A

Stop and safely park your vehicle as soon as possible

5-10

18
Q
1. Can brakes fade or fail from excessive heat caused by using them too much?
A

Yes

5-9, 5-10

19
Q
1. When testing the air brakes, when must the low pressure warning signal come on?
A

Before pressure drops to less than 60 psi

5-7

20
Q
1. When testing the air brakes, when must the low pressure warning signal come on?
A

Before pressure drops to less than 60 psi in the air tank (or tank with the lowest air pressure, in dual air systems)

(5-7)

21
Q
1. All vehicles with air brakes must have what signal?
A

Low Air Pressure Warning

5-4

22
Q
1. When is it ok to leave your truck unattended without applying the parking brakes and chocking the wheels?
A

Never

5-11

23
Q
1. A slack adjusters free play needs to be adjusted if it is more than about how many inches when you pull hard on it?
A

More than about one inch where the push rod attaches to it

5-6