Arizona CDL — Air Brakes Practice Test 1

1.Some buses have a separate air tank tied to a dual parking control valve. What important limit applies to it?

It holds only enough air to release the spring brakes a few times, so plan your movesIt can keep the spring brakes released for an entire shiftIt refills itself automatically from the trailer supplyIt works only while the engine is switched off

2.Antilock brakes are fitted to your tractor but not your trailer, and during hard braking the trailer begins to swing out. What is the correct reaction?

Come off the brakes somewhat, if you can do that safely, until the trailer lines up againPress the pedal down harder to force the trailer straightPull the parking brake knob out while still movingCut the steering wheel sharply toward the shoulder

3.Why is it important to let the water out of the air tanks, especially before cold weather?

Water improves braking friction and must be measuredOil in the tanks raises the governor cut-out pressureWater keeps the alcohol evaporator topped offWater sitting in the tanks can freeze and cause the brakes to fail

4.On a tractor or straight truck, spring brakes will apply by themselves once air pressure falls into roughly what range?

70 to 90 psi45 to 60 psi20 to 45 psi5 to 15 psi

5.When should you avoid setting the spring parking brakes and use wheel chocks instead?

Any time you park on level groundWhenever the vehicle is loadedWhen the brakes are very hot from a steep grade, or very wet in freezing weatherWhenever the engine is running

6.What is the 'wig wag' device found on some air brake systems?

A gauge that shows how much pressure is being appliedA valve that limits pressure to the front brakesA knob that releases the spring brakesA mechanical arm that drops into the driver's view when pressure gets low

7.Why can you still apply the brakes a few times even if the air compressor quits working?

The storage tanks keep a reserve of compressed airThe springs generate their own supply of airThe governor makes air without the compressorThe brake pedal pumps air by hand

8.What is a reliable way to find out whether your vehicle was built with antilock brakes?

Count the number of air tanksCheck the color of the parking-brake knobRead the certification label to see when the vehicle was builtMeasure the governor's cut-out pressure

9.Who needs to study the air brakes material to be properly prepared?

Only drivers of vehicles built before 1975Only drivers who pull a trailerOnly bus driversAnyone who will operate an air-braked truck or bus, or tow a trailer equipped with them

10.The safety relief valve on the first air tank is normally set to open at about what pressure?

About 60 psiAbout 100 psiAbout 125 psiAbout 150 psi