Florida CDL — Air Brakes Practice Test 7

1.Some air brake systems include an alcohol evaporator. What job does it do?

It boosts air pressure when the compressor failsIt cleans exhaust fumes out of the compressed airIt lubricates the s-cam rollers automaticallyIt puts alcohol into the system to help keep ice from forming in valves and lines during cold weather

2.What does a good normal service-brake stop feel like in a bus or truck with air brakes?

A smooth, safe stop using enough pedal pressure — clutch in only when engine rpm nears idleA quick, firm stop that tests the brakes at every lightCoasting in neutral and finishing with the parking brakeLight pedal taps repeated until the vehicle drifts to a halt

3.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

4.During your pre-trip you find cracked brake drums and an audible air leak at a brake chamber. What are you required to do?

Drive slowly and get the repairs done at your destinationLog the defect and continue if the low-air warning worksNot drive the vehicle until the brake defects are repairedDisconnect the leaking chamber and rely on the remaining brakes

5.In an emergency stop, 'controlled braking' means:

Braking lightly and steering sharply around the hazardApplying the brakes as hard as possible without locking the wheelsUsing only the trailer brakes to keep the rig straightPumping the pedal rapidly the whole time

6.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

7.You are about to park for the night in freezing weather, and your brakes are soaking wet from slush. What does the handbook suggest doing first?

Set the parking brakes right away so they hold before freezingRide the brakes lightly in a low gear to warm and dry themSpray the brake drums with alcohol from the evaporatorPump the brake pedal several times to blow the water out

8.While driving a truck with a dual air brake system, pressure in one of the two systems falls dangerously low. What should you expect?

One end of the vehicle, front or rear, will brake at reduced power and your stop will take longerThe healthy system automatically doubles its pressure to make up the differenceSpring brakes clamp instantly on every axle of the truckBraking is unaffected, because both systems draw from one shared tank

9.Your tractor has antilock brakes but the trailer behind it does not, and during a hard stop the trailer begins swinging out. What is the right response?

Apply the trailer hand valve fully to pull the trailer straightAccelerate until the trailer drops back into line behind youReduce pressure on the brake pedal, when it is safe to do so, until the trailer settlesHold maximum pedal pressure and steer hard in the opposite direction

10.The parking and emergency brakes on trucks, tractors, and buses must be held on by mechanical force, usually powerful springs, rather than by air. What is the reason?

Springs apply the brakes faster than air can flowAir-applied brakes would overheat while parkedSprings give more stopping power than service brakesAir pressure can slowly leak away over time