Air Brakes Flashcards
The stop light switch:
Turns on the brake lights to warn drivers behind you
Truck and bus parking or emergency brakes must be heald on by:
Mechanical Force
The most common type of fundation brake found on heavy vehicles is the:
S-cam drum
You are on a steep downgrade and have reached your “safe” speed of 40 mph. You would apply the service brake until you speed drops to ___
35 mph
How should you check that the trailer brakes come on when air pressure in the system drops below a certain level?
Chock the wheels, release the parking brake, shut the engine off, and check for movement
If your truck’s air compressor has its own oil supply, when should you first check the oil level?
Before Driving
For air brake systems, the air compressor should start pumping at no lower than ___psi
85 psi
You should know you brakes are fading when:
You have to push the brake pedal harder to control speed on a downgrade
Repeatedly pressing and releasing (fanning) the brake pedal may result in:
The loss of brake air pressure
The air brake lag distance at 55 mph on dry pavement adds about ___feet to you stopping distance
32 ft
In air brake vehicles, the parking brakes should be used:
Any time the vehicle is parked
If the spring bakes are on, when should ypou push the brake pedal?
Never
If your truck has a dual air system and one of the systems is ow on pressure:
Either the front or rear brakes will not be fully operational
The air loss rate for a straight truck or bus with the engine off and the brakes on should no be more than:
3 psi in one minute
The brake pedal in an air brake system:
Controls the air pressure applied to put on the brakes
The braking power of the spring brakes:
Depends on the service brakes being in adjustment
The driver must be able to see a low air pressure warning which comes on before pressure in the service air tanks falls below___psi.
55 psi
What is emergency control braking:
You apply the brakes as hard as you can without locking the wheels
If your truck or bus has dual parking controls valves, you can use pressure from a separate tank to:
Release spring emergency/parking brakes to move a short distance
During normal driving, spring brakes are usually heald back by:
Air pressure
The parking or emergency brakes of trucks and buses can be legally heald on by ___ pressure
Spring
The air compressor governor controls:
When air is pumped into the air storage tanks
A supply pressure gauge tells you how much pressure is in the:
Air Tanks
When you apply the brakes, the brake shoes/linings are pressed against the:
Brake Drum
Why drain water from compressed air tanks?
Water can freeze in cold weather and cause brake failure
Some brake systems have an alcohol evaporator. what may happen if you don’t keep the unit filled with alcohol?
Ice may form in the air storage tanks and cause the brakes to fail
The (first) most important thing to do when low air pressure warning comes on is:
Stop and safely park as soon as possible
If you vehicle has an alcohol evaporator, every day during cold weather you should:
Check and fill the alcohol level
Your truck has a properly functioning dual air brake system and minimum size air tanks. The air pressure should build from 85 to 100 psi within ___ seconds
45 seconds
Your truck or bus has a dual air brake system. If a low air pressure warning comes on for only one system, what should you do?
Stop and safely park. Continue only after the system is fixed
It is not safe to drive a vehicle that has brake drums (or discs) with craks or that are thinner than manufacturer’s specifications, generally this will be ___ inch.
1/4 inch
Air braking takes more time than hydralic braking because air:
takes more time to flow through the lines than hydraulic fluid
Total stopping distance for vehicles with brakes is longer than that for vehicles with hydralic brakes due to ___ distance
Brake Lag
If you must make an emergency stop, brake so you:
Can steer and you vehicle stays in a straight line
When is it OK to leave your truck unattended without applying the parking brake or chiking the wheels?
Never
The use of air brakes on a downgrade is only a supplement to the:
Braking effect on the engine
The proper method of braking when going down long and/or steep grades after selecting the proper gear, is to brake until you speed is about ___ miles per hour below your “safe” speed, then release your brakes.
5 mph
The S-cam:
Forces the brake shoes agaist the inside of the brake drum
To test air service brakes, you should:
Brake firmly when slowly moving forwards
If you dont have automatic tanks drains, how often should you drain the oil and water from the bottom of compressed air storage air tanks?
At the end of each day of driving
Which of these is NOT a proper time to apply the parking brakes?
When you brakes are very hot
the brake system that applies and releases the brakes when the driver uses the brake pedal is the ___ brake system
Service
For air brake systems in good condition, the air compressor should start pumping at about ___ psi.
100 psi
Before driving a truck or bus with a dual brake system, the pressure in each system should be at least ____psi.
100 psi
Modern air brake systems are three different systems combined together. They are the service, parking, and the ___ brakes.
Emergency
The modulating control valve allows you to control the:
Spring Brakes
Exessive heat in the brakes can cause the:
brakes to fade or fail
How should you check that the spring brakes come on when air pressure in the system drops below a certain level?
Park on level ground, chock the wheels, release the parking brake whe you have enough pressure, shut the engine off, and repeatedly press and release the brake pedal
The applicatipn pressure gauge shows how much air pressure you:
Are applying to the brakes
What is emergency stab braking?
brake hard, release the brakes when the wheels lock, and reapply the brakes when the wheels start rolling
Under normal conditions, to engage the parking brake the driver must first:
Let the air out of the spring brakes
If you truck has a dual air brake system and one of the systems is low on pressure:
Either the front or rear brakes will not be fully operational
The parking or emergency brake on a heavy vehivle can only be held in position by something that cannot leak away, like:
Spring Pressure
The air supply pressure gauge shows how much pressure:
Is in the air tanks
All air brake equipped vehicles have:
An air supply pressure gauge
If air pressure does NOT build up fast enough within the correct amount of time:
Your air pressure may drop too low during driving
The spring brakes used on tractors and straight trucks will bring you truck to a stop when air pressure drops below ___ psi
20 psi
How should you check that your service brakes are working properly?
wait for normal air pressure, release the parking brake, move the truck forward slowly, and apply the brake firmly using the brake pedal
To check the brake slack on S-cam brakes, you should park on:
level ground, chock the wheels, and release parking brakes
The air brake system for a straight truck or bus should not leak at a rate of more than ___ psi per minute with the engine OFF and the brakes released.
2 psi/min
The air loss rate for a straight truck or bus wih the engine off and the brakes on should NOT be more than:
3 psi in one minute
The safety valve is set to automatically reduce pressure at ___ psi
150 psi
With air brake vehicles, the parking brakes should be used:
Whenever you leave the vehicle unattended
A truck with air brakes going 55 mph would require a stopping distance of:
More than 300 feet
If you vehicle has an alcohol eveporator, it is there to:
Reduce the risk of ice in air brake valves in cold weather
The brake system that applies and releases the brakes when the driver uses the brake pedal is the ___ brake system.
Service
The air compressor governor controls:
When air is pumped into the air tanks
