New Hampshire CDL — Air Brakes Practice Test 9

11.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

12.Wedge brakes and S-cam brakes use different mechanisms. What does the manual's description show they have in common?

Both force brake shoes against the inside of a brake drumBoth use a power screw to clamp a rotorBoth rely on a caliper with lining padsBoth are self-adjusting on every vehicle

13.Section 5 covers brakes that are too hot or too wet to set the parking brakes on. Which pairing of condition and remedy matches the manual?

Very hot brakes: set the parking brakes to hold the heat in. Wet brakes: drain the air tanksVery hot brakes: let them cool first. Wet brakes: drive in a low gear with light brake pressure until they heat up and dryVery hot brakes: pump the pedal rapidly. Wet brakes: set the parking brakes at onceVery hot brakes: work the parking knob in and out. Wet brakes: top up the alcohol evaporator

14.The final air brake check gives roughly 100 psi for compressor cut-in and roughly 125 psi for cut-out. What reminder does the manual attach to those figures?

Add 10 psi to each figure in cold weatherCheck the manufacturer's specificationsUse them only for vehicles made before 1975Treat them as exact limits that never vary

15.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

16.Section 2 gives a minimum total stopping distance of 419 feet at 55 mph. The Air Brakes section gives a total of more than 450 feet at the same speed. What accounts for the difference?

A longer perception time for drivers of air-braked vehiclesThe extra weight of the air tanks and compressorBrake lag, which adds about 32 feet at 55 mph on dry pavementABS, which lengthens every stop

17.What does the manual warn could happen if you walk away from your vehicle without setting the parking brakes or chocking the wheels?

The spring brakes could overheatIt could roll off and hurt someone or damage propertyThe air tanks could overfillThe ABS could lose its settings

18.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

19.Which gauge does the manual say all air-braked vehicles have, and which does it say is missing on some?

All have an application pressure gauge; the supply pressure gauge is not on every vehicleAll have both gaugesNeither gauge is on every vehicle; both are optionalAll have a supply pressure gauge; the application pressure gauge is not on every vehicle

20.A failed low pressure warning lets air leak away without your noticing. The manual says a dual system will then need a longer stopping distance. What does it add about the braking you have left?

Only limited braking is possible before the spring brakes come onFull braking remains until the tanks are completely emptyThe front brakes shut off but the rear brakes are unaffectedThe ABS takes over and stops the vehicle