Missouri CDL — Air Brakes Practice Test 10

11.On a long, steep downgrade, the service brakes should be used how?

As the only means of slowing, held down steadilyInstead of downshifting, to spare the transmissionAs a supplement to the engine's braking, after you are in a low gearOnly after the spring brakes have engaged

12.How does the air brake system turn on your brake lights for drivers behind you?

An electric switch operated by air pressure lights the lamps when you brakeA cable mechanically pulls the light onA sensor reads wheel speed and lights the lampsThe compressor signals the lamps directly

13.What is the benefit of a modulating control valve for the spring brakes?

It automatically drains the tanksIt doubles tank pressure in an emergencyIt locks only the front wheelsIt applies the spring brakes gradually, giving control if the service brakes quit

14.Why do the brakes still work for several applications after the compressor stops running?

The wheels store energy that runs the brakesEach brake chamber holds its own backup canisterThe governor makes air without the compressorThe storage tanks keep a reserve of compressed air on hand

15.In controlled braking during an emergency, how hard should you press the brakes?

Fully to the floor until the wheels lockLightly, then release completelyOnly enough to feel a slowdownFirmly, but not so hard the wheels lock, using only small steering inputs

16.An air brake arrangement is really a combination of three braking functions. Which set correctly names them?

The service, parking, and emergency brakesThe hydraulic, mechanical, and vacuum brakesThe front, rear, and trailer brakesThe primary, secondary, and reserve brakes

17.How large a crack in a brake drum is unacceptable during inspection?

Any hairline mark on the outer surfaceA crack shorter than one inchOnly a crack that goes fully throughA crack running more than half the width of the friction area

18.At roughly what tank pressure does the governor tell the compressor to stop pumping (cut-out)?

Around 55 psiAround 125 psiAround 150 psiAround 100 psi

19.After fully applying the foot brake for one minute on a single vehicle, air loss above what rate is too much?

More than 1 psiMore than 3 psiMore than 6 psiMore than 8 psi

20.How do you check that the parking brake will hold?

Rev the engine to redline with the brake offCoast downhill without the parking brakePress the brake pedal while parkedSet the parking brake and gently try to pull forward in a low gear