ELDT ELDT - Entry Level Driver Training Air Brakes Questions and Answers 2

Question 1

What is the function of the dual air brake system in a commercial motor vehicle?

Accepted Answer

To provide a backup system if one circuit fails

Answer

To double braking force on the front axle

Answer

To allow independent trailer braking

Answer

To cool brake drums faster

Question 2

How should a driver test the low air pressure warning device before driving?

Accepted Answer

Fan the brakes with the engine off until pressure drops to 60 psi

Answer

Drive until the alarm sounds

Answer

Apply full service brakes for 30 seconds

Answer

Check it using a pressure gauge only

Question 3

What happens to spring brakes when air pressure in the parking brake circuit falls below approximately 20–45 psi?

Accepted Answer

They apply automatically

Answer

They release automatically

Answer

They lock in neutral position

Answer

Nothing — they require manual activation

Question 4

What is a slack adjuster and why is it important in air brakes?

Accepted Answer

A mechanical linkage that adjusts the distance between the brake lining and drum

Answer

A valve that controls airflow to the brake chamber

Answer

A sensor that monitors brake pad thickness

Answer

A pressure relief valve in the air tank

Question 5

Which control is used to apply the trailer brakes independently of the tractor brakes?

Accepted Answer

The hand valve (trailer brake)

Answer

The foot pedal

Answer

The parking brake knob

Answer

The emergency brake switch

Question 6

What does an S-cam drum brake system use to spread the brake shoes against the drum?

Accepted Answer

An S-shaped camshaft

Answer

Air pressure directly

Answer

A wedge mechanism

Answer

Hydraulic pistons