New Hampshire CDL — Air Brakes Practice Test 4

11.The hand check of S-cam slack adjusters starts with parking on level ground and chocking the wheels. Why are the chocks needed for this particular check?

The parking brakes are released for the check, so the chocks are what keep the vehicle from movingThe chocks take the vehicle's weight off the slack adjustersThe chocks keep the air tanks level so the gauge reads trueThe chocks hold the brake shoes against the drums

12.Which order matches the manual's service brake test at the end of the final air brake check?

Set the parking brake, pull against it in a low gear, then release itShut the engine off, hold the foot brake for a minute, then read the gaugeLet air pressure reach normal, take the parking brake off, ease forward at about 5 mph, then brake firmly with the pedalBrake firmly at highway speed, then check the gauge for pressure loss

13.Controlled braking and stab braking are both emergency-stop methods. How does the way you first apply the brakes differ between them?

Controlled braking uses the parking brake control; stab braking uses the foot pedalControlled braking is all the way on; stab braking is a light, steady applicationControlled braking is for vehicles with ABS only; stab braking is for trailers onlyControlled braking is as hard as possible without locking the wheels; stab braking is all the way on until the wheels lock

14.The figure 55 psi turns up several times in the Air Brakes section. Which of these is NOT tied to 55 psi?

The tank pressure before which the low air warning must come onThe minimum pressure to build in both halves of a dual system before drivingThe system pressure below which a wig wag drops into viewThe application pressure at which automatic front limiting valves stop cutting air to the front brakes

15.Which of these air brake parts does the driver work from inside the cab?

The safety relief valveThe S-camThe parking brake controlThe slack adjuster

16.In the four-part air brake check on the vehicle inspection test, the engine is shut off for the air leakage rate test. When do the remaining parts have you start it again?

Right before the air warning device testRight before the emergency brake testThey do not; the air warning device test is done without restarting the engine, and the emergency brake test carries on from thereAfter each one-minute timing period

17.According to the opening of the Air Brakes section, what does an air brake system use to make the brakes work?

Hydraulic fluid pushed by an engine-driven pumpVacuum drawn from the engine's intakeCompressed airElectric motors mounted at each wheel

18.On the vehicle inspection test, you check that the power unit's parking brake holds a combination vehicle. What state should the trailer brakes be in for that check?

SetDisconnected at the glad handsReleasedApplied with the hand valve

19.The manual calls hitting the brakes a good response when someone suddenly pulls out ahead of you, but only under two conditions. What are they?

You have ABS on every axle, and the road is dryYou have room to stop, and you apply the brakes the right wayYou are below 35 mph, and the trailer is emptyThe spring brakes are on, and the clutch is pushed in

20.For which units does the manual say it may be hard to tell whether ABS is fitted?

Truck tractors built after March 1, 1997Buses with dual parking control valvesAny vehicle whose malfunction lamp is yellowTowed units built before the Department of Transportation required ABS