CDL Air Brakes TestDual Air Brake SystemsMedium
A driver is performing a post-trip inspection and observes that the parking brake, which is spring-applied and air-released, is functioning correctly. Which air brake system is typically responsible for supplying the air to release the parking brake?
- AA dedicated emergency air tank, separate from the service brake systems.
- BThe secondary air system, to ensure front brake priority.
- CBoth primary and secondary systems equally, for redundancy.
- DThe primary air system, as it often supplies the largest volume of air.
Show answer & explanationAnswer & explanation
Correct answer: D. The primary air system, as it often supplies the largest volume of air.
In most commercial vehicles with dual air brake systems, the primary air system is responsible for supplying the air to release the spring-applied parking brakes. This is because the primary system typically handles the rear service brakes and often has a larger capacity or is prioritized for systems like the parking brake release.
Why the other options are wrong
- A. While there are emergency systems, the air to release the parking brake generally comes from one of the main service brake systems, typically the primary.
- B. The secondary system typically handles front brakes; parking brake release is usually tied to the primary system.
- C. While redundancy is key for service brakes, the parking brake release is usually supplied by one main system, not equally by both.
Parking Brake Air Supply
The air to release spring-applied parking brakes is typically supplied by the primary air system in a dual air brake setup.
- Primary system responsibility
- Releases spring brakes
- Ensures parking brake function
Memory trick: The 'Primary' system is the 'prime' choice for parking brake release.