Maryland CDL — Air Brakes Practice Test 10

1.Why must you drain the water and oil out of the air tanks?

To make the compressor run more quietlyBecause trapped water can freeze and lead to brake failureTo raise the governor cut-out pressureTo keep the brake lights from staying on

2.When the spring brakes finally set on a lightly loaded rig, or on a slick road surface, what extra danger appears?

The trailer brakes let go before the tractor brakes doThe compressor restarts on its own and rebuilds full pressureThe vehicle can slide and you may lose control of itThe steering axle locks itself into a straight-ahead position

3.What is brake lag, the extra delay that air brakes add to stopping?

The distance you coast before noticing a hazardThe short delay while air travels through the lines to the brakesThe time it takes the compressor to refill the tanksThe gap between the tractor and the trailer brakes

4.As soon as the low-pressure warning first comes on while you are driving, what should you do?

Speed up to reach your destination before the air runs outPump the brake pedal repeatedly to rebuild pressureIgnore it until the spring brakes apply by themselvesImmediately pull over and stop safely while you still have air to work the brakes

5.How do air brakes actually bring a heavy vehicle to a stop?

Compressed air presses the shoes or pads against the drum or rotorBrake fluid is pumped under pressure to each wheel cylinderEngine vacuum pulls the linings tight against the drumsAn electric motor spins the wheels backward to slow them

6.What is true of an air tank fitted with a manual drain valve?

It empties the tank by itself while you driveIt only works when the parking brake is setIt comes standard with an electric heaterYou must open it yourself by turning it or pulling a cable

7.What is the purpose of an alcohol evaporator in an air brake system?

It lowers the chance of ice building up in the valves during cold weatherIt boosts the octane of the fuel supplyIt replaces the need to check tire pressureIt cools the brake drums after long descents

8.What does the governor control on an air brake vehicle?

How fast the vehicle is allowed to travel on the highwayWhen the compressor pumps air into the storage tanksHow much pressure is being sent to the brake chambersWhen the spring brakes release for parking

9.How does a modulating control valve let a driver use the spring brakes?

It applies the spring brakes only fully or not at allThe farther you move the lever, the more firmly the spring brakes engageIt drains the air tanks a little at a timeIt raises the governor cut-in pressure gradually

10.At 55 mph on dry pavement, about how long is the total stopping distance for an average driver with good brakes?

Over 450 feetAbout 100 feetAbout 200 feetUnder 50 feet