California CDL — Air Brakes Practice Test 10

1.What is "controlled braking" in an emergency stop?

Braking as hard as possible without locking the wheelsBraking only with the trailer hand valveLocking the wheels intentionally to scrub off speedUsing the parking brake and service brake together

2.Why is it a bad habit to press and release the brake pedal over and over when you do not need to?

It makes the governor cut out the compressor too earlyIt causes the safety relief valve to openIt sends extra air to the spring brakes and locks them onEach release vents air, and you can use it up faster than the compressor refills the tanks

3.What is the correct way to confirm that the parking brake holds the vehicle?

Release it on a downgrade and see whether the vehicle rollsSet it, then pull gently against it in a low gearDrive forward at about 5 mph and pull the control knob outHold the brake pedal down for one minute and watch the air gauge

4.Before starting down a long, steep downgrade in a vehicle with air brakes, what should you do?

Speed up to get down the grade quickly before the brakes heat upShift into neutral to reduce wear on the transmissionApply the parking brake lightly to help the service brakesSlow down and shift to a low gear so engine braking controls your speed

5.During an inspection of s-cam brakes with a manual slack adjuster, you pull hard on each slack adjuster (with the parking brakes released and wheels chocked). When does a slack adjuster need adjustment?

If it moves at all when pulled by handIf it moves more than about an inch at the point where the push rod connectsIf it moves more than about three inches where the push rod attachesOnly if the brake drum shows cracks

6.How are the brake lights turned on in an air brake system?

A cable connected to the brake pedal pulls a mechanical switchAn electric stop light switch that works by air pressure turns them onThe driver must turn them on with a dashboard toggleThe governor activates them at cut-out pressure

7.Any time you park a vehicle equipped with air brakes and leave it unattended, what should you do?

Leave the vehicle in gear with the engine idlingHold light service-brake pressure with a pedal lockApply the parking brakes by pulling out the yellow, diamond-shaped knobDrain the air tanks so the spring brakes cannot release

8.What must a driver do to hold a CDL without an air brake restriction?

Complete an approved air brake repair courseHold the CDL for at least one year without violationsPass the air brakes knowledge test and take the skills test in a vehicle with full air brakesSubmit a medical certificate showing normal hearing for the low-air buzzer

9.On heavy trucks and buses, the parking and emergency brakes are held on by mechanical force — usually springs — rather than by air. Why?

Air pressure applies the brakes too slowly for parkingCompressed air freezes whenever the engine is shut offAir pressure can leak away over timeSprings produce more stopping power than the service brakes

10.The air compressor governor controls when the compressor pumps air into the storage tanks. At about what pressure does the governor stop the compressor from pumping (the "cut-out" pressure)?

About 60 psiAbout 100 psiAbout 125 psiAbout 150 psi