Missouri CDL — Air Brakes Practice Test 3

11.What is a 'wig wag' device?

A gauge that shows how much pressure is appliedA valve that drains the tanks automaticallyA backup buzzer wired to the stop lightsA mechanical arm that drops into the driver's view when pressure sinks below 55 psi

12.The safety relief valve in the first air tank is usually set to open at what pressure?

150 psi100 psi55 psi125 psi

13.At roughly what tank pressure does the governor tell the compressor to stop pumping (cut-out)?

Around 55 psiAround 125 psiAround 150 psiAround 100 psi

14.The total stopping distance for an air brake vehicle is made up of which four parts?

Perception, reaction, tire, and drum distancePerception, reaction, brake lag, and braking distanceReaction, coasting, gear, and braking distancePerception, steering, lag, and skid distance

15.When should you skip setting the parking brakes and use wheel chocks instead?

Any time the vehicle is loadedWhen the brakes are very hot from a grade or very wet in freezing weatherOnly on a slight inclineWhenever the engine is running

16.Using the stab braking method, what do you do after the wheels lock up?

Ease off the brakes until the wheels roll again, then reapply them fullyHold the brakes locked until you stopPump the pedal rapidly while steering hardShift to a lower gear and coast

17.When the low air warning light and buzzer first come on, what should you do?

Stop the vehicle safely without delay, while you still have control over the brakesKeep driving until the spring brakes apply by themselvesPump the pedal to rebuild pressure and continueRelease the parking brake and coast

18.How often must you empty air tanks fitted with manually operated drain valves?

Once a weekAt the end of each day you driveOnly before long tripsEach time you refuel

19.Why is it a mistake to pump the brake pedal on and off without need?

It overheats the slack adjustersIt forces the governor to cut out earlyIt drains oil out of the compressorIt can release air faster than the compressor replaces it, dropping pressure too low to brake

20.When you pull on an s-cam slack adjuster by hand, about how much movement suggests it needs adjustment?

Any movement at allMore than three inchesMore than roughly one inch where the push rod attachesOnly if it does not move