MS CDL Air Brakes case studies
MS CDL Air Brakes · Put your knowledge to work in context.
The Mississippi CDL Air Brakes knowledge test is the endorsement exam a driver must pass before operating a commercial vehicle equipped with air brakes. It applies to tractors and trailers, dump trucks, buses, and any power unit whose brakes work by compressed air rather than hydraulic pressure. The MS CDL Air Brakes case studies are 5 cases and about 3,147 words.
1Hissing at the Left Rear Chamber After Parking Brake Release
A driver is pre-tripping a 2019 tandem-axle tractor with a dual air system. Both dash gauges show 118 psi after the governor cuts out.
599 words, about 3 min2One Gauge Reads Zero While the Other Holds 105 psi
A driver starts a 2020 straight truck with a dual air brake system on a cold morning. The secondary gauge climbs to 105 psi; the primary gauge stays at 0.
691 words, about 3 min3Pushrod Stroke Out of Limit on One Side
During a pre-trip inspection of a 2016 tandem-axle dump truck, the driver measures the left rear service chamber pushrod. With the brakes released, the pushrod is at 0.5 inch; with the brake pedal fully applied and the system at 110 psi, it extends to 2.75 inches.
534 words, about 3 min4Leak-Down Test Fails After Ten Minutes
A driver performs an air brake leak check on a 2018 tractor-trailer after charging the system to governor cut-out at 120 psi. He shuts off the engine, releases the parking brake, and applies and holds the service brake pedal for one minute.
611 words, about 3 min5Air Pressure Falls Below 50 psi on a Downhill Highway
A driver is descending a 5% grade on a two-lane highway at 50 mph in a 40,000 lb tractor-trailer. The low-pressure warning buzzer sounds and the primary gauge falls from 95 psi to 48 psi in about 15 seconds.
712 words, about 4 min