Mississippi CDL — Air Brakes Practice Test 3

11.At operating rpm, your dual air truck with standard-size tanks takes about two minutes to climb from 85 to 100 psi. What does that tell you?

That is normal for any dual air systemThe governor needs to cut out soonerPressure is building too slowly, so do not drive until it is fixedYou should drive gently and it will catch up

12.A new driver says his truck has ABS, so he can follow closer because he will always stop shorter. What does the manual say?

ABS does not necessarily shorten stopping distance, but it helps keep the vehicle under control in hard brakingHe is right, since ABS cuts stopping distance in halfABS adds to normal braking power, so closer following is safeABS works only at highway speeds

13.Braking hard on a slick road in a vehicle without ABS, you lock the rear wheels but not the steering wheels. What is the main danger?

Losing all steering control at the frontNothing, since only steering-wheel lockup mattersA skid, a jackknife, or even a spinThe spring brakes applying on their own

14.You watch your air gauge climb to about 125 psi and then hold steady. What is the most likely reason it stopped rising?

The safety valve opened to dump the extra airA leak is letting air out as fast as it comes inThe compressor broke down once the tanks were fullThe governor reached its cut-out point and stopped the compressor from pumping

15.In stop-and-go traffic you keep pressing and releasing the brake pedal far more than you need to. What could this lead to?

The governor cutting out early and overfilling the tanksThe spring brakes releasing on their ownBrake lag dropping to zeroAir leaving the system faster than the compressor can replace it, until the brakes no longer work

16.You start a truck with a dual air brake system. The primary gauge reads 105 psi, but the secondary reads 80 psi. Are you ready to drive?

Yes, because one system above 100 psi is enoughNo; wait until the secondary system also reaches at least 100 psiYes, because both systems are above 55 psiNo; wait until both systems reach 150 psi

17.If your service brakes fail, how can a modulating control valve help you stop?

It releases the spring brakes so you can coast to a stopIt sends air from the trailer tanks to the tractor brakesIt lets you apply the spring brakes gradually, harder the farther you move the leverIt cuts front brake pressure in half

18.Your truck has a brake system failure. To bring it to a stop, the emergency brake system relies on parts of which other systems?

The engine cooling and fuel systemsThe service brake and parking brake systemsThe trailer hand valve and the turn signalsOnly the front-axle brake chambers

19.Of these air brake items, which one belongs in the engine compartment step of the seven-step inspection rather than a later step?

The slack adjusters on the s-cam brakesThe governor's cut-in and cut-out pressuresThe low air pressure warning signalThe air compressor drive belt, if the compressor is belt-driven

20.Your brake lights stay dark when you apply the air brakes, even though the bulbs are good. Which air brake part is most likely involved?

The governorThe safety relief valveThe slack adjusterThe stop light switch, an electric switch worked by air pressure