North Carolina CDL — Air Brakes Practice Test 3

1.What is a dual air brake system?

One system that powers both the brakes and the hornA setup with two brake pedals for redundancyTwo separate air brake systems operated by a single set of controlsA backup hydraulic circuit that takes over if air is lost

2.Why should you avoid pressing the brake pedal while the spring brakes are applied?

The combined spring and air forces could damage the brakesIt will drain the trailer's air tank instantlyIt disables the ABS warning lampIt forces the governor to cut out early

3.An air-brake vehicle actually contains three braking systems. Which set correctly names them?

The primary, secondary, and reserve systemsThe service, parking, and emergency systemsThe foot, hand, and drum systemsThe hydraulic, electric, and mechanical systems

4.During a walk-around, brake linings should be rejected if they are:

Slightly dusty but firmly attachedLoose, soaked with oil or grease, or dangerously thinWarm to the touch after drivingA different brand than the drums

5.Why is repeatedly pumping (fanning) the brake pedal when it isn't needed a bad habit in an air-brake vehicle?

It overheats the alcohol evaporatorIt forces the governor into an early cut-outIt can release air faster than the compressor can replace it, dropping pressure too lowIt permanently locks the spring brakes

6.According to the manual, front-wheel braking on an air-brake vehicle is:

Helpful in all conditions, with front-wheel skids from braking unlikely even on iceDangerous on wet roads and best switched offOnly useful when the trailer is fully loadedAutomatically disabled above 60 psi

7.With the engine off and the foot brake fully applied for one minute, the air-loss rate is too high on a single vehicle if pressure drops more than:

3 psi in one minute10 psi in one minute1 psi in one minute20 psi in one minute

8.How should you test the service brakes at the end of the brake check?

Apply them hard while parked and watch the gaugeRoll forward slowly, about 5 mph, then press firmly and note any pulling or delayPump the pedal until the low-air warning soundsSet the parking brake and rev the engine

9.What is the purpose of an alcohol evaporator in some air-brake systems?

To top off the compressor's own oil supplyTo boost pressure to the front brakes on hillsTo automatically drain the reservoirsTo lower the chance of ice forming in valves during cold weather

10.How do air-operated disc brakes differ from S-cam brakes?

They use springs instead of air to apply the padsThey use a power screw that clamps the rotor rather than an S-camThey need no brake chamber or slack adjusterThey work the front wheels only