Kansas CDL — Air Brakes Practice Test 10

11.In an emergency stop, when does the manual say an ABS-equipped vehicle's brakes may be pushed all the way down?

Whenever the tractor has ABS, even if the trailer does notWhenever the pavement is dry and the vehicle is loadedWhen the straight truck or combination you drive always has working ABS on all of its axlesOnly once the ABS malfunction lamp has come on during the trip

12.How did the s-cam brake get its name?

Its cam is shaped like the letter SThe S stands for 'spring'The S stands for 'service'It was named for the S-shaped air line that feeds it

13.On a long downgrade, a couple of your truck's brakes are out of adjustment while the rest are properly adjusted. How does this lead to trouble?

The adjusted brakes lock up, which sets off the spring brakes on the drive axlesThe poorly adjusted brakes overheat first and turn on the ABS malfunction lampThe air compressor falls behind, so the tanks empty before the bottom of the gradeThe badly adjusted brakes stop pulling their weight, so the others overheat and fade

14.On a long downgrade you keep leaning on the service brakes even after they start to fade. Where can that lead?

The ABS will take over and cool the brakesThe fade will stop once the drums finish expandingThe fade can keep growing until you can no longer slow or stop the vehicleThe spring brakes will hold you at a safe speed automatically

15.Your air compressor is belt-driven. What should you check about the belt during the engine compartment step?

Only that a belt is presentThat it slips slightly at idle to protect the compressorIts condition and how tight it isThe part number printed on it

16.A tour bus has lost main air, and you need to reposition it using the separate air tank that serves its dual parking control valves. What limitation should shape how you plan the move?

Each push of the release button wears out the spring brakes permanentlyThe separate tank holds only enough air to release the brakes a few timesThe release button only works while the engine runs at a fast idleThe low air warning shuts the engine off after about one minute

17.On an older single air brake system (pre-1975), the typical buildup check is 50 to 90 psi within 3 minutes. At what engine speed is that measured?

Full governed engine speedOperating rpm with the vehicle under loadAny speed, as long as the parking brake is releasedAn idle of about 600 to 900 rpm

18.Your straight truck's air system is fully charged at about 125 psi. For the first leakage check, you turn off the engine, push in the parking brake knob, and simply time the pressure drop. What loss rate is acceptable?

Less than 2 psi in one minuteLess than 3 psi in one minuteLess than 5 psi in one minuteAny rate, provided the low air warning stays off

19.Your trailer has ABS but your tractor does not. What does the trailer's ABS make less likely when you brake?

The trailer swinging outThe tractor jackknifingLosing steering control at the frontBrake lag

20.Only your tractor has ABS. During a hard stop, you see in the mirror that the trailer is starting to swing out. What should you do?

Press harder on the pedal so the tractor's ABS can steady the trailerPull the parking brake knob so every wheel locks at onceHold full pressure and wait, since tractor ABS straightens the trailerEase off the brakes, as long as you can do that safely