ELDT ELDT - Entry Level Driver Training Air Brakes Questions and Answers 1 — Questions and Answers
Question 1: What is the minimum air pressure required before driving a vehicle equipped with air brakes?
- 60 psi
- 80 psi
- 100 psi (Correct answer)
- 120 psi
Correct answer: 100 psi
FMCSA requires air pressure to reach at least 100 psi before a CMV with air brakes can be driven.
Question 2: What does the low air pressure warning activate in most air brake systems?
- An automatic brake application
- A warning light and/or buzzer (Correct answer)
- The parking brake release
- The exhaust brake
Correct 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.
Question 3: What is the purpose of the air compressor governor in an air brake system?
- To release air from the tanks
- To control when the compressor cuts in and cuts out (Correct answer)
- To monitor brake temperature
- To regulate the spring brakes
Correct 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.
Question 4: During the static air leakage test, what is the maximum allowable air pressure drop per minute for a combination vehicle?
- 1 psi
- 2 psi
- 3 psi (Correct answer)
- 4 psi
Correct 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.
Question 5: What type of brakes are spring brakes designed to act as?
- Service brakes
- Emergency and parking brakes (Correct answer)
- Trailer brakes only
- Exhaust brakes
Correct answer: Emergency and parking brakes
Spring brakes are designed to serve as emergency and parking brakes, engaging automatically when air pressure is lost.
Question 6: What is brake fade and what causes it in air brake systems?
- Reduced braking power caused by overheated brake drums (Correct answer)
- A sudden increase in brake pressure
- Air leaking from brake lines
- Improper slack adjuster setting
Correct 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.
ELDT ELDT - Entry Level Driver Training Air Brakes Questions and Answers 1
What is the minimum air pressure required before driving a vehicle equipped with air brakes?