Air Brake Systems Flashcards
7 cards from real CLP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Air Brake Systems flashcards as text
What is the correct technique for braking on a long, steep downgrade with air brakes?
Answer: Apply brakes firmly to reduce speed by about 5 mph, release, then reapply as needed
The proper technique is to apply brakes firmly until speed drops about 5 mph below your target speed, then release them and allow brakes to cool before reapplying.
What does a properly functioning air dryer do in an air brake system?
Answer: Removes moisture and contaminants from compressed air before it reaches the tanks
An air dryer removes water vapor and contaminants from compressed air to prevent moisture buildup that could freeze lines or damage system components.
How much air pressure loss per minute is acceptable for a combination vehicle during the static leakage test with brakes released?
Answer: 5 psi or less
For a combination vehicle with brakes released, the air pressure should not drop more than 4 psi in one minute (3 psi for single vehicles); 5 psi or less is acceptable.
What is the role of the S-cam in a drum air brake system?
Answer: It rotates to force the brake shoes outward against the brake drum when brakes are applied
When air pressure moves the push rod, it turns the S-cam, which pushes the brake shoes outward against the drum to create friction and slow the vehicle.
Why should you never push down the brake pedal to release spring brakes (parking brakes) when there is no air pressure?
Answer: There is no air pressure to compress the springs, so the service brake pedal cannot release them
Spring brakes are held released by air pressure; without air, the springs are fully extended and the foot valve cannot mechanically compress them.
What is a slack adjuster, and when does it need adjustment?
Answer: A mechanical arm that adjusts the distance between brake shoes and drum; needs adjustment when push rod travel exceeds limits
Slack adjusters connect the push rod to the S-cam and compensate for brake lining wear; they must be adjusted when push rod stroke exceeds the legal limit.
What happens to the emergency brakes on a trailer if the trailer breaks away from the tractor?
Answer: The trailer's spring brakes automatically apply due to the loss of air supply
When a trailer breaks away, the air supply line loses pressure, causing the trailer's spring brakes to automatically apply and stop the runaway trailer.