CDL Air Brakes Test flashcards

To safely descend long, steep grades with air brakes, use a low gear, engine brake, and short, firm applications (snubs) of the service brakes to maintain a safe speed and prevent overheating.

• Use a low gear to maximize engine braking.
• Apply service brakes firmly until speed drops by 5 mph.
• Release brakes to allow cooling, then repeat.
• Never 'ride' the brakes or coast.

Memory trick: Downhill: 'Gear Low, Snub Slow!'

Components of an air brake system that store compressed air for use by the brakes and other air-powered accessories.

• Hold a reserve of air pressure.
• Essential for multiple brake applications.
• Must be drained regularly to remove contaminants.

Memory trick: Tanks are like batteries, holding air for when you need it.

An emergency braking technique used in air-braked vehicles WITHOUT ABS, involving full brake application followed by a brief release to prevent wheel lock-up and maintain steering, then reapplying.

• For vehicles without ABS.
• Apply brakes fully, then release.
• Prevents wheel lock-up.
• Maintains steering control.

Memory trick: No ABS? Stab and steer, clear your fear!

A pre-trip inspection test that measures how quickly the air compressor can build air pressure from 85 psi to 125 psi at operating RPM, indicating its health and efficiency.

• Engine at operating RPM.
• Single vehicle: 85 to 125 psi in 45 seconds or less.
• Combination vehicle: 85 to 125 psi in 45 seconds or less.

Memory trick: Recovery Rate: 'Forty-Five Seconds, Fast and Fine!'

The total distance a fully loaded commercial vehicle with air brakes travels from the moment a driver perceives a hazard until the vehicle comes to a complete stop.

• Includes perception, reaction, brake lag, and actual braking distance.
• Approximately 450 feet at 55 mph.
• Significantly longer than passenger vehicles.
• Crucial for safe following distance.

Memory trick: Fifty-five, four hundred fifty, stay alive and don't be hasty.

A technique used on long downgrades to control vehicle speed and prevent brake fade by applying brakes firmly for short periods, then releasing them to cool.

• Prevents brake fade by allowing cooling.
• Used on long, steep downgrades.
• Involves firm, short brake applications.

Memory trick: Downhill, don't drag, just 'snub' to be safe.

A defect in the air lines or components of the service brake system that allows compressed air to escape, reducing braking effectiveness and causing pressure loss.

• Rapid pressure drop upon pedal application.
• Reduced or ineffective braking.
• Indicates a critical safety issue.

Memory trick: Leaks mean low pressure, no stop, no go.

A component in an air brake system that controls when the air compressor starts and stops, maintaining system air pressure within a safe and efficient range.

• Cuts out (stops) between 100-125 psi.
• Cuts in (starts) between 85-100 psi.
• Maintains optimal air pressure.
• Essential for air brake function.

Memory trick: Governor: High (Cut Out) and Low (Cut In) keeps the air flow.

The total distance a vehicle travels from the moment a driver perceives a hazard until the vehicle comes to a complete stop.

• Comprises Perception Distance, Reaction Distance, Brake Lag Distance, and Braking Distance.
• Increases significantly with speed and vehicle weight.
• Air brake systems have an inherent brake lag component.

Memory trick: Perceiving, Reacting, Lagging, Braking – that's the full distance.

The typical air pressure range applied to brake chambers during a routine, controlled service brake application in an air brake system.

• Usually 40-60 psi.
• Provides controlled braking force.
• Prevents over-pressurization.

Memory trick: Pressure Points: Low for light, Medium for normal, High for hard.

The air pressure range at which the spring brakes (parking/emergency brakes) in an air brake system will automatically engage due to insufficient air pressure, typically between 20-45 psi.

• Activates automatically when air pressure is too low.
• Provides emergency braking if service air fails.
• Also used for parking the vehicle.

Memory trick: Spring Brakes 'Snap' from Twenty to Forty-Five!

A braking technique for non-ABS vehicles on slippery surfaces, where the driver applies firm brake pressure, releases completely when wheels are about to lock, and then reapplies, to maximize braking while maintaining steering.

• For vehicles without ABS.
• Used on slippery surfaces.
• Apply firm, release completely, reapply.
• Prevents sustained wheel lock-up.

Memory trick: Slippery Road, No ABS? 'Stab and Steer, My Dear!'

The inherent time delay in an air brake system between when the driver presses the brake pedal and when the brakes actually begin to apply.

• Characteristic of air brake systems.
• Caused by air travel time.
• Increases stopping distance.
• Must be accounted for by drivers.

Memory trick: Lag is the wait, fade is the heat.

A pre-trip inspection procedure for air-braked combination vehicles to check for air system leaks by measuring pressure drop over one minute with brakes fully applied.

• Engine off, service brakes fully applied.
• Maximum 4 psi pressure drop in one minute.
• Higher drop indicates a leak.
• Crucial for safety and compliance.

Memory trick: Combo Four, Single Two, Leaks are bad, it's true!

A pre-trip inspection procedure to check for air leaks in a single commercial vehicle's air brake system by measuring pressure drop over time with the engine off and brakes applied.

• Engine off, wheels chocked.
• Service brakes fully applied.
• Maximum 3 psi drop in one minute for a single unit.

Memory trick: Pressure Drop: 'Three' for a Truck, 'Five' for a Fleet!

A technique for braking on slippery surfaces with air-braked vehicles without ABS, involving applying firm, consistent pressure just short of wheel lock-up to maintain steering control.

• For vehicles without ABS.
• Apply brakes as hard as possible without skidding.
• Maintain steering control.
• Ease off if wheels begin to lock.

Memory trick: Slippery roads? Control your stop, don't let it pop!

When parking an air-braked vehicle on a grade, set the parking brake, and place the transmission in the lowest gear (for upgrades) or reverse (for downgrades) to provide additional security against rolling.

• Use parking brake.
• Use proper gear (low for upgrade, reverse for downgrade).
• Consider chocking wheels.

Memory trick: Parked on a Hill? 'Gear Up, Then Lock It Still!'

The air pressure at which the air compressor governor stops the compressor from pumping air into the storage tanks.

• Typically occurs between 120-140 psi.
• Prevents over-pressurization of the air brake system.
• Ensures adequate air supply without wasting energy.

Memory trick: The governor smartly cuts off when pressure is high.

The correct sequence of actions to safely secure a commercial vehicle with air brakes when parking, typically involving engaging the parking brake before engine shutdown.

• Engage parking brake first.
• Then shut off the engine.
• Ensures vehicle is secured.
• Prevents accidental rolling.

Memory trick: Park first, then power off.

For a straight truck, with the engine off and service brakes firmly applied, the air pressure should not drop more than 3 psi in one minute.

• Engine off, brakes applied
• Maximum 3 psi drop in 1 minute
• Indicates excessive leaks if exceeded

Memory trick: Remember 'three' for 'straight truck' when you're testing the brakes.

In a typical dual air brake system, the primary system controls the rear service brakes and the parking brake control, while the secondary system controls the front service brakes.

• Primary = Rear Brakes + Parking Brake Control.
• Secondary = Front Brakes.
• Ensures critical redundancy.

Memory trick: Primary to the back, secondary to the front, parking brake follows the main run.

In a dual air brake system, having separate air lines for the primary and secondary systems ensures that a failure in one line does not compromise the air supply and function of the other braking system.

• Crucial for system redundancy.
• Maintains partial braking in an emergency.
• Protects against single-point failure.

Memory trick: Two lines mean two chances to deliver air.

A typical dual air brake system features separate primary and secondary air tanks that supply air through separate lines to different sets of brake chambers, often splitting between front and rear axles.

• Primary/Secondary tanks
• Distinct air lines
• Often front/rear split

Memory trick: Separate tanks and separate lines mean a 'split' system for safety.

Refers to the independent control mechanisms within a dual air brake system that ensure the primary and secondary service brake systems operate without mutual interference, preserving redundancy.

• Ensures system independence.
• Aids in partial braking during failure.
• Includes distinct sections of the foot valve or relay components.

Memory trick: Independent controls mean one switch won't break the other.

The parking brake (spring brakes) typically uses air pressure from the primary air system to keep them released. A pressure drop in the primary tank when applying/releasing the parking brake can indicate a leak in that circuit.

• Primary system often supplies parking brake air.
• Spring brakes engage when air pressure is lost.
• Air is used to 'hold off' the spring brakes.

Memory trick: Park with primary air, leaks make it scary.

The requirement for dual air brake systems in commercial vehicles stems from the critical need for safety redundancy.

• Prevents total brake failure.
• Ensures partial braking capability.
• A foundational safety regulation.

Memory trick: Two systems, two chances, to avoid the worst advances.

For a straight truck, the maximum allowable air loss rate with the engine off and brakes released is 2 psi in one minute.

• Engine off, brakes released.
• Maximum 2 psi drop per minute.
• Applies to primary and secondary systems individually.
• Higher loss indicates a leak.

Memory trick: Two for straight, three for combo, no more loss, or no go.

The separation of primary and secondary air brake systems helps maintain vehicle stability and steering control during a partial brake system failure.

• Prevents total loss of braking.
• Allows driver to maintain control during emergencies.
• Ensures safer stopping with partial braking.

Memory trick: Dual brakes mean dual chances to steer clear of disaster.

The low air pressure warning system is designed to alert the driver when the air pressure in either service brake system drops to a critical minimum level.

• Warning activates at 60 psi or lower.
• Applies to both primary and secondary systems.
• Indicates a need to stop and address the issue.

Memory trick: Sixty is the limit, don't ignore it.

A noticeable and sustained difference in air pressure readings between the primary and secondary air tanks in a dual air brake system, often indicating a problem with air flow.

• Can be caused by restrictions, leaks, or component malfunctions.
• Requires investigation to ensure safe braking.
• Should be addressed before operating the vehicle.

Memory trick: Uneven air means a flow problem, like a kinked hose.

Separate controls in a dual air brake system mean that the control mechanisms for the primary and secondary systems are independent, preventing a single failure from disabling both.

• Ensures control redundancy
• Critical for safety
• Independent valves/mechanisms

Memory trick: Separate controls are like having two different 'switches' for two different light bulbs.

Separate lines and controls for primary and secondary air brake systems are essential for isolating potential failures and maintaining redundancy.

• Prevents single point of failure.
• Ensures partial braking in emergencies.
• Enhances overall vehicle safety.

Memory trick: Separate lines, separate fears, separate systems, fewer tears.

The safety feature of a dual air brake system where two independent air systems provide braking, ensuring that a failure in one system does not result in total loss of braking capability.

• Mandated for commercial vehicles.
• Provides a critical safety backup.
• Allows for partial braking in emergencies.

Memory trick: Two systems are better than one for stopping power.

One-way check valves are crucial components in an air brake system that ensure air flows in only one direction, maintaining pressure in the reservoirs.

• Prevents air from bleeding back to the compressor.
• Maintains tank pressure if supply line fails.
• Essential for dual system integrity.

Memory trick: Check the valve, air won't leave, only receive.

A one-way check valve in a dual air brake system allows air to flow in one direction only, preventing air loss from one system into another or back to the compressor.

• Ensures system independence.
• Critical for safety redundancy.
• Located between compressor and tanks, and sometimes between tanks.

Memory trick: Check the valve, check the flow, keep them separate, let air grow.

A common cause for slow air pressure build-up in a dual air brake system, when the compressor is otherwise functional, is a restricted air intake filter on the compressor.

• Limits air intake
• Reduces compressor efficiency
• Prevents proper pressure build-up rate

Memory trick: If the air's slow to fill, check the compressor's 'breathing' filter still.

If one air system reaches full pressure and the compressor cuts out, but the other system is significantly lower, it indicates a leak or restriction in the lower-pressure system.

• Compressor stops at cut-out
• Lower system has an issue
• Requires leak/restriction search

Memory trick: If one tank is full and the other's not, the low one has a 'leak' or 'knot'.

A noticeable difference in air pressure between the primary and secondary air systems often indicates a leak in the system with lower pressure.

• Each system has its own gauge.
• Significant difference points to a leak.
• Compressor fills both systems.

Memory trick: Separate gauges, separate troubles, separate fixes.

The primary purpose of a dual air brake system is to provide a critical safety measure by ensuring a backup braking system in the event of a single system failure.

• Redundancy is key
• Prevents total brake loss
• Mandated for safety

Memory trick: Dual systems are like a 'safety net' for your brakes.

In a dual air brake system, significant and persistent pressure differences between the primary and secondary air tanks can indicate a problem.

• Gauges should show similar pressures.
• A difference of 20-25 psi or more may indicate a leak or faulty component.
• Requires investigation and repair before operation.

Memory trick: Two gauges, two numbers, if unequal, something's troubled.

The low air pressure warning for a dual air brake system must activate when air pressure drops to or below 60 psi for EACH system.

• Mandated by federal regulations (e.g., 49 CFR 393.51).
• Applies to both primary and secondary systems.
• Ensures timely warning of critical pressure loss.

Memory trick: Sixty is the safety line for sound and sight.

The minimum air pressure level (60 psi) at which the low air pressure warning device must activate in a commercial vehicle's air brake system.

• Mandated by federal regulations (FMCSA).
• Applies to both primary and secondary systems.
• Crucial for driver safety awareness.

Memory trick: Sixty PSI is the 'danger zone' for air brakes.

When a low air pressure warning device (light/buzzer) fails to activate despite the air pressure in its associated system dropping below the required threshold (60 psi).

• Indicates a fault in the sensor, wiring, or alarm unit.
• Compromises driver awareness of critical air loss.
• Must be repaired immediately for safety.

Memory trick: If the gauge drops but the alarm stays quiet, check the sensor.

The maximum allowable rate of air pressure drop in a straight truck's air brake system (engine off, brakes released) during a leak test, which is 2 psi per minute.

• Tests for air leaks in the system.
• Different limits for combination vehicles.
• Exceeding limits requires repair.

Memory trick: Two PSI is the magic number for straight truck leaks.

Dividing dual air brake system control between different axle groups (e.g., drive vs. steering) provides crucial redundancy, ensuring partial braking if one system fails.

• Prevents total brake loss
• Enhances vehicle stability
• Critical safety feature

Memory trick: Redundancy is like having backup brakes for your primary and secondary axles.

Separate air lines in a dual air brake system means that the primary and secondary systems have distinct plumbing from their air tanks to the brake chambers they serve.

• Ensures system independence
• Prevents total brake loss
• Critical for redundancy

Memory trick: Think of 'separate lines' like two distinct roads leading to different destinations.

If one of the two independent air brake systems fails, the other system will continue to function, providing partial braking capability, though with reduced effectiveness.

• Prevents total brake loss.
• Vehicle will still have some braking.
• Stopping distances will increase.
• Steering control may be affected.

Memory trick: One system down, still some stop, but not top.

In a dual air brake system, separate air tanks isolate the air supply for the primary and secondary braking systems, preventing a single point of failure from causing total air loss.

• Crucial for system redundancy.
• Ensures partial braking capability.
• Prevents cross-contamination of air loss.

Memory trick: Two tanks mean two chances to stop.

The scenario where one of the two independent air brake systems in a commercial vehicle fails, resulting in the loss of braking for the axles controlled by that system, while the other system remains functional.

• The vehicle retains partial braking capability.
• A low air pressure warning will activate.
• Requires immediate and careful driving action.

Memory trick: One system down means half the brakes, still enough to slow.

When one air tank in a dual system reaches the compressor cut-out pressure while the other remains significantly lower, indicating an issue with air delivery or measurement to the lower-pressure tank.

• Suggests a blockage or faulty gauge.
• Can indicate an issue with check valves.
• Requires immediate investigation for safe operation.

Memory trick: If air can't flow, the gauge won't show.

The expected temporary drop in air pressure (typically 10-25 psi) in a dual air brake system during a full service brake application in a combination vehicle, followed by recovery when the brakes are released, indicating normal system operation.

• Normal for combination vehicles.
• Indicates air is being used by brake chambers.
• Recovery confirms compressor function.

Memory trick: Press the pedal, air goes down, release, air comes back up.

If one of the two independent air brake systems (primary or secondary) fails, the other system continues to provide partial braking capability.

• Primary system typically controls rear brakes.
• Secondary system typically controls front brakes.
• Failure of one system means loss of braking for its controlled axle(s).

Memory trick: Front brakes gone, rear brakes on, still slow, but not gone.

Separate air tanks in a dual air brake system provide redundancy, ensuring that a failure in one system does not compromise the entire braking capability.

• Each system has its own tank(s).
• Ensures air supply for at least one braking circuit.
• Crucial for vehicle safety.

Memory trick: Two tanks, twice the safety, twice the stop.

Observing a faster pressure drop in one air system (primary or secondary) during a leak test indicates a fault or leak specific to that compromised system.

• Helps isolate the location of a leak.
• Highlights the value of separate systems.
• Requires investigation of the faster-dropping system.

Memory trick: One tank drops fast, that's where the leak is cast.

Separate controls in a dual air brake system refer to the internal independence of components like air lines, tanks, and pressure gauges, but typically utilize a single foot pedal valve with internal separation for brake application.

• Single foot pedal for driver input.
• Foot pedal valve has internal primary/secondary sections.
• Air tanks, lines, and gauges are separate.
• Ensures redundancy.

Memory trick: Separate parts, single step, safety's goal, no misstep.

The low air pressure warning system (light and buzzer) activates when air pressure drops below 60 psi in either the primary or secondary system.

• Activates at 60 psi or less.
• Must work before air pressure builds to 60 psi.
• If gauges are normal but warning is active, suspect the sensor/switch.

Memory trick: Gauges say good, light says bad, sensor's mad.

For a combination vehicle, a normal drop in air pressure during a firm service brake application is typically 5 psi or less.

• Applies to combination vehicles
• Drop per firm application
• Indicates healthy system

Memory trick: Five for a 'combination' is fine, but less for a 'straight' line.

This test checks for air leaks when the service brakes are applied, with the engine off, for a combination vehicle.

• Engine off, parking brake released, service brake applied.
• Maximum allowable drop is 4 psi in 1 minute.
• Tests the system under load conditions.

Memory trick: Four for a combo, when you press the pedal to the floor, no more.

Separate air lines for primary and secondary systems ensure redundancy, meaning a leak or failure in one line does not compromise the air supply to the other braking system.

• Each system has dedicated lines.
• Crucial for safety and partial braking.
• Prevents single point of failure.

Memory trick: Two paths, two chances, brake with confidence in all circumstances.

Over-pressurization in an air brake system, indicated by the safety valve continuously releasing air and high gauge readings (e.g., 150 psi), is typically caused by a malfunctioning air compressor governor.

• Safety valve opens around 150 psi.
• Governor regulates compressor cut-out/cut-in.
• Failure to cut out leads to over-pressure.

Memory trick: Pressure too high, governor's eye is dry.