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

What is the minimum air pressure required before driving a vehicle equipped with air brakes?

Answer: 100 psi

FMCSA requires air pressure to reach at least 100 psi before a CMV with air brakes can be driven.

What does the low air pressure warning activate in most air brake systems?

Answer: A warning light and/or buzzer

A warning light and/or buzzer activates when air pressure drops to around 60 psi, alerting the driver to stop safely.

What is the purpose of the air compressor governor in an air brake system?

Answer: To control when the compressor cuts in and cuts out

The governor controls the air compressor, causing it to cut out around 125 psi and cut back in around 100 psi.

During the static air leakage test, what is the maximum allowable air pressure drop per minute for a combination vehicle?

Answer: 3 psi

For a combination vehicle, air pressure should not drop more than 3 psi per minute with the engine off and brakes released.

What type of brakes are spring brakes designed to act as?

Answer: Emergency and parking brakes

Spring brakes are designed to serve as emergency and parking brakes, engaging automatically when air pressure is lost.

What is brake fade and what causes it in air brake systems?

Answer: Reduced braking power caused by overheated brake drums

Brake fade is a reduction in braking effectiveness that occurs when brake drums overheat from prolonged or repeated braking.