Washington CDL — Air Brakes Practice Test 2

1.Which foundation brake design is found most often on air brake vehicles?

The s-cam drum brake.The wedge brake.The air-over-hydraulic disc brake.The external band brake.

2.What is a 'wig wag' on an air brake vehicle?

A lever that manually drains the tanks.A mechanical arm that drops into view when pressure falls below 60 psi.A gauge needle showing the applied brake pressure.A switch that turns on the brake lights.

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

150 psi.125 psi.100 psi.60 psi.

4.According to the manual, what is the most common brake defect found during roadside inspections?

Brakes that are out of adjustment.Missing alcohol evaporators.Cracked supply pressure gauges.Overfilled air tanks.

5.Why is needlessly pumping the brake pedal on and off a dangerous habit in an air brake vehicle?

It overheats the alcohol evaporator.It can drain air faster than the compressor can replace it, leaving too little to brake.It permanently raises the governor cut-in pressure.It causes the safety valve to seal shut.

6.What most directly causes brake fade on a long grade?

Draining the tanks too often.Keeping the vehicle in too low a gear.Overusing the service brakes instead of engine braking, which builds excessive heat.Refilling the alcohol evaporator mid-descent.

7.Why is it important to remove the water and oil that gather in the air tanks?

Because moisture can freeze in cold weather and knock the brakes out.Because oil raises the governor's cut-out pressure over time.Because water improves stopping power and must be rationed.Because the compressor cannot run while any liquid remains.

8.Using the recommended braking technique on a long downgrade, once you are in the proper low gear you should do what?

Hold steady light pressure on the brakes the entire way down.Leave the brakes alone and rely only on the gear.Fan the pedal on and off several times per second.Brake firmly to slow about 5 mph below your safe speed, release, then repeat as needed.

9.What have tests shown about front-wheel braking on slippery surfaces?

Skids caused by front braking are unlikely even on ice, so front braking helps everywhere.Front brakes must always be disabled below freezing.Front-wheel braking triples the chance of a skid on ice.Front brakes only work once the trailer is loaded.

10.Why can the brakes still be applied several times even after the compressor quits pumping?

Because the wheels store braking energy mechanically.Because the governor keeps generating pressure on its own.Because the storage tanks hold a reserve of compressed air.Because the spring brakes recharge the system automatically.