Florida CDL — Air Brakes Practice Test 6

11.Your older tractor has a front brake limiting valve with 'normal' and 'slippery' settings. According to the handbook, how should you use it?

Keep it in the normal position, because front-wheel braking skids are unlikely even on iceSwitch it to slippery whenever it rains to prevent jackknifingAlternate between settings every few miles to keep the valve from stickingUse slippery mode in town and normal mode on the highway

12.Continuing to fan off air pressure with the key on, you watch for the parking brake knob to pop out on its own. In what pressure range should the spring brakes come on?

Between about 20 and 45 psiBetween about 50 and 75 psiBetween about 85 and 100 psiOnly when pressure reaches zero

13.Some vehicles have a modulating control valve — a dash lever with taper-graduated positions. What is it for?

Adjusting how quickly the compressor recharges the tanksBalancing braking force between tractor and trailerSetting the governor cut-out point from the cabGradually applying the spring brakes to stop the vehicle if the service brakes fail

14.You are parking a vehicle whose spring brakes are controlled by a modulating control valve on the dash. What should you do with the control lever?

Leave it halfway so the brakes can cool while parkedMove it just far enough to feel the brakes take holdReturn it to the released position and chock the wheelsMove it all the way and lock it there with its locking device

15.Most newer heavy vehicles are built with dual air brake systems. What does that mean?

There is one air system for the tractor and a hydraulic system for the trailerTwo separate air systems share a single set of brake controls, so one can still work if the other failsEach wheel has two brake chambers for double the stopping forceThe parking brake and service brake use the same air tank

16.The low air pressure warning light and buzzer come on while you are rolling down the interstate. Your first responsibility is to:

Continue to the next truck stop where a mechanic is availableStop and park in the safest place available as soon as you canDownshift and rely on engine braking for the rest of the tripPump the brake pedal to rebuild pressure

17.Using the proper braking technique on a long downgrade, you have reached your safe speed of 40 mph in a low gear. What comes next?

Hold light, steady pedal pressure all the way to the bottomBrake firmly down to about 35 mph, release, and repeat when speed returns to 40 mphShift to a higher gear so the engine turns more slowlyApply the parking brake in short bursts

18.On most newer trucks and buses with air brakes, how do you set the parking brakes?

Pull out the yellow, diamond-shaped knobPush in the yellow, diamond-shaped knobPull out the red, eight-sided knobPump the brake pedal three times and hold it down

19.Why should you avoid pressing the brake pedal down while the spring brakes are applied?

It wastes fuel by loading the compressorIt could set off the low air pressure warning falselyThe combined spring and air forces could damage the brakesIt will release the parking brake unexpectedly

20.Adding perception, reaction, brake lag, and braking distance together, a heavy vehicle traveling 55 mph on good pavement needs a total stopping distance of:

Under 150 feetAbout 250 feetMore than 450 feetNearly 1,000 feet