Texas CDL — Air Brakes Practice Test 7

1.You are performing the static leakage test on a single vehicle: engine off, fully charged system, foot off the brake, parking brake released, and you time the pressure drop. What is the most the pressure may fall?

4 psi in one minute2 psi in one minute3 psi in 30 seconds1 psi in five minutes

2.Which list correctly names all the parts of total stopping distance for a vehicle with air brakes?

Perception + reaction + brake lag + effective braking distanceReaction + effective braking distance onlyPerception + governor lag + coasting distanceBrake lag + downshift distance + following distance

3.For an average driver in an air-braked vehicle at 55 mph, with good traction and brakes, the total stopping distance is about how far?

About 150 feetAbout 250 feetMore than 450 feetOnly about 32 feet

4.Why does an air-braked vehicle need a greater following distance than a car traveling the same speed?

Brake lag adds stopping distance that hydraulic brakes do not haveAir brakes only work below 45 mphTrucks have better tires, so they can follow closer if neededThe governor limits how hard the pedal can be pressed

5.As part of the seven-step air brake check, how do you test that the low pressure warning signal works?

Rev the engine to 2,000 rpm and watch the supply gaugePull the trailer air supply knob and listen for a buzzerShut the engine off, turn the key on, and fan the pedal until the warning activatesOpen a drain valve until the tanks are completely empty

6.Why should you drain the air storage tanks on a vehicle with manually operated drain valves at the end of each day of driving?

To keep the tanks from over-pressurizing overnightTo reset the governor cut-in pressureTo test the low air pressure warning deviceTo remove water and oil that could freeze and cause brake failure

7.Some buses have dual parking control valves and a separate air tank that can release the spring brakes after main air pressure is lost. Why must you plan carefully before using it to move?

The separate tank holds only enough air to release the brakes a few timesUsing it disables the service brakes until the whole system is repaired by a mechanicIt releases the spring brakes on the front axle onlyIt works only while the engine is shut off

8.Your air compressor has its own oil supply instead of using engine oil. What should you do before driving?

Drain the oil so it cannot reach the air tanksCheck the compressor's oil levelAdd alcohol to the compressor oil reservoirNothing, because the governor monitors compressor oil automatically

9.You are parking a vehicle whose spring brakes are applied with a modulating control valve on the dash. How do you set it?

Move it halfway so the brakes can be released quicklyLeave it in the released position and rely on wheel chocks to hold the vehiclePush the lever all the way and secure it with the locking devicePump the lever several times to build spring pressure

10.By law, when must the low air pressure warning signal in an air-braked vehicle activate?

Before tank pressure drops below 55 psiOnly after the spring brakes have appliedWhen pressure exceeds 125 psiWhen pressure drops below 20 psi