New Hampshire CDL — Air Brakes Practice Test 5

1.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

2.In the manual's description of the air compressor governor, what is the "cut-in" pressure?

The tank pressure, around 100 psi, at which the governor lets the compressor pump againThe tank pressure, around 125 psi, at which the governor stops the compressorThe pressure at which the safety relief valve opens to protect the tanksThe pressure at which the low air warning signal has to come on

3.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

4.Some air tanks expel water and oil automatically. What else does the manual say these tanks may be equipped for?

Refilling the alcohol evaporatorReleasing the spring brakesManual draining as wellShutting off the compressor

5.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

6.Step 3 of the seven-step inspection in Section 2 has you look at the gauges once the engine is running. What does it say about the air pressure gauge?

It should hold steady at 55 psi while the engine idlesIt should climb from 50 psi to 90 psi in no more than 3 minutes, and you go on building to governor cut-outIt should reach 150 psi before you release the parking brakeIt should drop 3 psi each minute until the engine warms up

7.A straight truck's air leakage is checked both ways with the engine off. With the brakes released, the gauge falls 2.5 psi in one minute. With the foot brake held fully down, it also falls 2.5 psi in one minute. How do those results compare with the manual's limits for a single vehicle?

Within the limit on both testsToo much loss on both testsToo much loss with the brakes released, but within the limit with the foot brake appliedWithin the limit with the brakes released, but too much with the foot brake applied

8.Why does the manual say an air brake system includes a stop light switch?

Because the low air warning needs a second lampBecause the compressor must shut off during brakingBecause the parking brake knob needs a dash indicatorBecause drivers behind you have to be warned when you brake

9.Which of these Step 7 checks does the manual have you run with the engine shut off?

The governor cut-out checkThe rate of air pressure buildup checkThe service brake testThe low pressure warning signal test

10.Each time you let up on the brake pedal, some compressed air leaves the system and tank pressure drops. What does the manual say makes up for the lost air?

The spring brake chambersThe alcohol evaporatorThe air compressorThe safety relief valve