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NS Air Brake Test study materials
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NS Air Brake Test practice questions

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Question 1Air Brake System Components and Operation

In a typical air brake system, what is the primary function of the compressor?

  1. To release air pressure from the brake chambers
  2. To regulate the rate of air flow to the trailer
  3. To build and maintain the supply of pressurized air in the reservoirs Correct answer.
  4. To apply mechanical force directly to the brake shoes

Explanation

The compressor draws in atmospheric air and compresses it to build the pressure stored in the system reservoirs. It is the source of energy for the entire air brake system, and its governing device cycles it to hold pressure within a set range. Brake application force is produced later, by components such as the brake chamber.

Question 2Air Brake System Components and Operation

What is the purpose of the air dryer in a vehicle air brake system?

  1. To increase reservoir pressure above governor cut-out
  2. To supply air directly to the brake chambers during a service application
  3. To remove moisture and contaminants from the compressed air Correct answer.
  4. To cool the compressor discharge before it reaches the reservoir

Explanation

The air dryer uses a desiccant cartridge to strip water vapor and oil carryover out of the compressed air before it enters the wet tank. Keeping moisture out of the reservoirs and downstream valves prevents corrosion and freeze-ups. The desiccant is later regenerated by a purge cycle when the compressor unloads.

Question 3Air Brake System Components and Operation

Which component stores the compressed air that is used for brake applications?

  1. The slack adjuster
  2. The brake chamber
  3. The reservoir tank Correct answer.
  4. The treadle valve

Explanation

Reservoirs store compressed air so that several brake applications can be made even after the compressor stops building pressure. Supply and service reservoirs are plumbed so that a loss in one circuit does not necessarily drain the other. The stored air is released to the chambers through valves when the driver applies the brakes.

Question 4Air Brake System Components and Operation

What does the governor do in an air brake system?

  1. It automatically applies the parking brake when pressure is lost
  2. It limits the maximum pressure in the brake chambers to the application pressure
  3. It controls the compressor's loading and unloading to hold reservoir pressure in a set range Correct answer.
  4. It balances air pressure between the tractor and trailer

Explanation

The governor senses reservoir pressure and signals the compressor to load when pressure falls to cut-in and to unload at cut-out. This cycling keeps supply pressure within the designed operating band. Typical settings hold the system roughly between 100 and 125 psi.

Question 5Air Brake System Components and Operation

What is the function of the slack adjuster?

  1. It stores air for emergency applications
  2. It meters air pressure to the brake chamber
  3. It converts the linear pushrod stroke into rotary motion to apply the brake shoes Correct answer.
  4. It releases air from the chamber when the pedal is released

Explanation

The slack adjuster is a lever arm mounted on the brake camshaft that turns the pushrod's straight-line stroke into rotation of the camshaft. That rotation forces the shoes against the drum. It also provides the adjustment that compensates for lining wear.

Question 6Air Brake System Components and Operation

In a dual-circuit air brake system, what is the main benefit of splitting the service brakes into two separate circuits?

  1. It allows the compressor to run less often
  2. It eliminates the need for spring brakes
  3. It reduces the number of reservoirs required
  4. It provides braking capability if one circuit loses pressure Correct answer.

Explanation

A dual-circuit system divides the service brakes so that a failure in one circuit still leaves a portion of the brakes operable through the other circuit. The foot valve is designed with separate supply and delivery sections for each circuit. This redundancy is the core safety advantage of the split design.

Question 7Air Brake System Components and Operation

What is the purpose of the tractor protection valve?

  1. It closes the tractor-to-trailer air lines if trailer pressure drops or the lines separate Correct answer.
  2. It regulates the compressor's cut-out pressure
  3. It limits the trailer's maximum speed
  4. It prevents the trailer from rolling away when parked

Explanation

The tractor protection valve senses trailer supply pressure and closes the coupling lines when that pressure falls below a safe level or when the lines part. This protects the tractor's air supply and triggers a trailer emergency application. It is a key component of the tractor-trailer interface.

Question 8Air Brake System Components and Operation

What is the role of the quick-release valve in a trailer air brake system?

  1. It rapidly fills the trailer reservoir during charging
  2. It filters moisture from the trailer air supply
  3. It speeds the exhaust of air from brake chambers when the brakes are released Correct answer.
  4. It automatically applies the brakes when pressure is lost

Explanation

The quick-release valve is mounted near the brake chambers and exhausts their air locally when the control pressure is released. This shortens the distance the exhaust air must travel, speeding release and reducing brake drag. Faster release improves brake response and lining life.

Question 9Air Brake System Components and Operation

A driver applies the foot valve and hears air escaping continuously from the treadle area even after the pedal is released. Which condition does this most likely indicate?

  1. A leaking or faulty foot valve Correct answer.
  2. A correctly functioning quick-release valve
  3. An overcharged trailer reservoir
  4. A normal exhaust of applied air

Explanation

Some exhaust is normal as the valve releases, but continuous leakage after release points to a faulty foot valve, such as a worn inlet or exhaust seat. A leaking foot valve wastes air and can prevent the system from holding pressure. It should be inspected and repaired before the vehicle is placed in service.

Question 10Air Brake System Components and Operation

During a static leak test, reservoir pressure drops from 120 psi to 100 psi in five minutes with the engine off and brakes released. What does this most likely indicate?

  1. A correctly operating compressor
  2. A normal pressure drop that requires no action
  3. A properly functioning governor
  4. An excessive leak that should be located and repaired Correct answer.

Explanation

With the engine off and brakes released, pressure should hold nearly steady; a 20 psi loss in five minutes is well beyond acceptable leakage. This indicates a leak somewhere in the system, such as a line, fitting, or valve. The leak should be traced with soap solution or by listening before the vehicle is used.

Question 11Air Brake System Components and Operation

What does the low-pressure warning device do when system pressure falls below a safe operating level?

  1. It increases compressor output to restore pressure
  2. It closes the tractor protection valve
  3. It activates a visible and audible warning to alert the driver Correct answer.
  4. It automatically applies the spring brakes

Explanation

The low-pressure warning device alerts the driver through a lamp and buzzer when pressure drops below a threshold, typically around 60 psi. The warning gives the driver time to stop safely before braking ability is lost. It does not itself apply the brakes or change compressor output.

Question 12Air Brake System Components and Operation

How do spring brakes apply when air pressure is lost?

  1. Air pressure pushes the diaphragm to apply the brakes
  2. Mechanical spring force applies the brakes when air pressure is removed Correct answer.
  3. The compressor directly forces the pushrod out
  4. The slack adjuster releases a latch that applies the brakes

Explanation

Spring brakes use a powerful coil spring that is held compressed by air pressure during normal operation. When pressure is released or lost, the spring expands and applies the brakes mechanically. This makes them fail-safe for parking and emergency stopping.

Question 13Air Brake System Components and Operation

A driver must make an emergency stop after a sudden loss of trailer supply pressure. What should the tractor protection valve do to help?

  1. Close the trailer supply line and cause the trailer spring brakes to apply Correct answer.
  2. Increase trailer reservoir pressure to compensate
  3. Keep the trailer service line fully open to maintain control
  4. Vent all tractor reservoir air to the atmosphere

Explanation

When trailer supply pressure falls below the safe threshold, the tractor protection valve closes the supply line to protect the tractor's air. The loss of supply pressure causes the trailer spring brakes to apply automatically. This fail-safe action brings the trailer to a controlled stop.

Question 14Air Brake System Components and Operation

What is the function of the relay valve on a trailer?

  1. It reduces reservoir pressure to the trailer's service line
  2. It stores air for the parking brake
  3. It measures pushrod stroke
  4. It uses reservoir air to apply the brakes quickly when signaled by the control line Correct answer.

Explanation

The relay valve takes a low-volume control signal from the foot valve and delivers a large volume of reservoir air directly to the trailer brake chambers. This shortens application time and reduces lag compared with routing all air through the foot valve. It thus speeds up brake response on long vehicles.

Question 15Air Brake System Components and Operation

An automatic slack adjuster is found to have a pushrod stroke beyond the manufacturer's limit after a brake application. What is the correct action?

  1. Increase reservoir pressure to compensate
  2. Continue operating and check again after several stops
  3. Adjust or repair the brake and investigate why the adjuster is not maintaining stroke Correct answer.
  4. Disconnect the slack adjuster to free the brake

Explanation

Excessive pushrod stroke means the brake is out of adjustment and will have reduced force and longer lag. The cause, whether a worn automatic adjuster, loose mounting, or worn linings, must be found and corrected. Simply continuing to drive is unsafe because braking performance is compromised.

Question 16Air Brake System Components and Operation

What is the purpose of the inversion valve in a spring brake system?

  1. To invert the direction of pushrod travel
  2. To allow a modulated spring brake application when service air is lost Correct answer.
  3. To reverse the flow of air to the compressor
  4. To convert reservoir pressure to electrical signals

Explanation

The inversion valve permits a controlled, modulated application of the spring brakes when service brake pressure is lost. Without it, a pressure loss would cause a full, uncontrolled spring brake application. It thus provides a graduated emergency braking capability.

Question 17Air Brake System Components and Operation

A vehicle with a dual-circuit system experiences a failure in the primary circuit. What should the driver expect from the secondary circuit?

  1. Full braking on all wheels
  2. Reduced but functional braking on the protected circuit Correct answer.
  3. Automatic application of the parking brake only
  4. No braking at all

Explanation

The secondary circuit is isolated from the primary so that a primary failure does not drain or disable it. The driver retains braking on the wheels served by the secondary circuit, though stopping distance will increase. This partial braking capability is the purpose of the split design.

Question 18Air Brake System Components and Operation

What does the safety valve on a supply reservoir protect against?

  1. Backflow of air from the trailer
  2. Loss of pressure in the service circuit
  3. Moisture accumulation in the reservoir
  4. Excessive pressure that could damage the reservoir or components Correct answer.

Explanation

The safety valve is a pressure relief device that opens if reservoir pressure rises above a set limit, protecting the tank and downstream components from overpressure. It is a backup to the governor in case the compressor fails to unload. It does not address moisture or circuit isolation.

Question 19Air Brake System Components and Operation

Why must reservoir drain cocks be opened periodically, especially in cold weather?

  1. To reduce reservoir pressure before every trip
  2. To test the compressor's cut-out setting
  3. To calibrate the low-pressure warning device
  4. To release accumulated water and oil that could freeze or corrode the system Correct answer.

Explanation

Moisture and oil that condense in the reservoirs can freeze in cold weather and block lines or valves, or corrode components over time. Draining the reservoirs removes this accumulation. Daily draining, particularly of the wet tank, is a standard preventive practice.

Question 20Air Brake System Components and Operation

What is the correct order of events when the driver releases the brake pedal in an air brake system?

  1. The compressor unloads, then the governor opens
  2. The foot valve exhausts control air, the relay valve exhausts chamber air, and the brakes release Correct answer.
  3. Air is delivered to the chambers, then the relay valve closes
  4. The spring brakes apply, then the service brakes release

Explanation

Releasing the pedal causes the foot valve to exhaust its control signal, which tells the relay valve to exhaust the chamber air locally. As chamber pressure drops, the return spring and pushrod retract and the shoes release. The compressor and governor operate independently of this release sequence.

Question 21Air Brake System Components and Operation

A driver reports that the tractor brakes apply but the trailer brakes do not respond to the foot valve. Which component is the most likely cause?

  1. The tractor's foot valve
  2. The tractor's slack adjusters
  3. The tractor's compressor
  4. The trailer relay valve or its control line Correct answer.

Explanation

The trailer relay valve receives the control signal from the tractor and delivers reservoir air to the trailer chambers. If the relay valve or its control line is faulty, the trailer will not respond even though the tractor brakes work. The tractor foot valve is functioning because the tractor brakes apply normally.

Question 22Air Brake System Components and Operation

Why is it important that the trailer supply line and service line use different coupler shapes?

  1. To make the lines easier to disconnect
  2. To reduce the cost of manufacturing the couplers
  3. To prevent cross-coupling that would defeat the trailer's emergency braking Correct answer.
  4. To allow the lines to carry higher pressure

Explanation

The supply (emergency) line and service line use incompatible couplers so they cannot be connected to the wrong gladhand. Cross-coupling would leave the trailer without a proper emergency air supply and could prevent the spring brakes from applying if the lines separate. The distinct shapes are a deliberate safety feature.

Question 23Air Brake System Components and Operation

An operator notices that the compressor runs almost continuously and reservoir pressure never reaches cut-out. Which combination of causes is most consistent with this symptom?

  1. A properly functioning air dryer purge cycle
  2. A governor stuck in the unloaded position
  3. A leaking system or a faulty governor that fails to unload Correct answer.
  4. A slack adjuster out of adjustment

Explanation

If pressure never reaches cut-out, the compressor keeps running because demand exceeds supply. A significant system leak or a governor that does not signal unload are the classic causes. A stuck-unloaded governor would instead keep pressure low with the compressor not building, and a slack adjuster has no effect on supply pressure.

Question 24Air Brake System Components and Operation

During a pre-trip inspection, the driver applies the service brakes and observes that the pushrod stroke on one chamber is much longer than on the others. What is the best interpretation?

  1. The low-pressure warning device is faulty
  2. The reservoir pressure is too high
  3. This is normal variation between chambers
  4. The affected brake is out of adjustment or has a mechanical fault and should be corrected Correct answer.

Explanation

Uneven pushrod stroke indicates that one brake is out of adjustment or has a mechanical problem such as a worn slack adjuster or broken component. The brake with the long stroke will apply later and with less force, reducing braking performance. It should be adjusted or repaired before the vehicle is operated.

Question 25Air Brake System Components and Operation

What is the function of the check valve installed between the compressor and the supply reservoir?

  1. To signal the governor when cut-out is reached
  2. To regulate the pressure delivered to the reservoir
  3. To drain moisture from the line
  4. To allow air to flow only toward the reservoir and prevent backflow Correct answer.

Explanation

The check valve permits air to flow from the compressor into the reservoir but blocks reverse flow when the compressor unloads or stops. This prevents reservoir air from bleeding back through the compressor. Pressure regulation is the governor's job, not the check valve's.

Question 26Air Brake System Components and Operation

What is the primary function of the air compressor governor in a heavy vehicle air brake system?

  1. It meters the volume of air delivered to the brake chambers during each application
  2. It regulates when the compressor loads and unloads to maintain reservoir pressure between cut-in and cut-out settings Correct answer.
  3. It filters moisture and oil from the air before it reaches the supply reservoir
  4. It limits maximum system pressure by venting excess air to atmosphere

Explanation

The governor senses reservoir pressure and signals the compressor's unloading mechanism to stop pumping at the cut-out pressure and resume at the cut-in pressure. This cycling keeps system pressure within the designed operating band without driver intervention. It does not meter air to the chambers or dry the air.

Question 27Air Brake System Components and Operation

A driver notices that the compressor recharges the reservoirs very slowly and the system pressure climbs only a few psi per minute. Which condition most directly explains a slow build rate?

  1. A relay valve with an internal service-port leak
  2. A spring brake chamber with a slow-release diaphragm
  3. A governor cut-out setting that is too high
  4. A restricted compressor intake or a worn compressor Correct answer.

Explanation

Build rate depends on how much air the compressor can draw in and compress, so a clogged intake or worn rings and valves reduce output. The symptom of slow pressure rise with the compressor running points to a supply-side restriction or compressor wear. Other listed faults affect holding or release behaviour rather than charging speed.

Question 28Air Brake System Components and Operation

What is the purpose of the alcohol evaporator or air dryer desiccant in the air charging system?

  1. To boost reservoir pressure above the governor cut-out point
  2. To reduce moisture in the air so it does not freeze or corrode downstream components Correct answer.
  3. To silence the compressor intake noise
  4. To lubricate the compressor's internal moving parts

Explanation

Moisture carried in compressed air condenses in reservoirs and lines, where it can freeze in cold weather and corrode valves. The dryer or evaporator removes or lowers that moisture content before the air is stored. It plays no role in lubrication, pressure boosting, or noise control.

Question 29Air Brake System Components and Operation

During a brake application the driver hears a sharp exhaust of air from a valve near the rear axle at the moment the brakes release. Which component is most likely producing that sound?

  1. The safety valve relieving excess reservoir pressure
  2. The relay valve exhausting air from the brake chambers Correct answer.
  3. The governor unloading the compressor
  4. The low-pressure warning buzzer venting air

Explanation

Relay valves exhaust the air they had delivered to the chambers when the control signal from the foot valve is removed, producing the characteristic release exhaust at the rear of the vehicle. This is normal operation, not a fault. Governors, safety valves, and warning devices do not vent chamber air on release.

Question 30Air Brake System Components and Operation

What does the application of the parking brake control valve do in a system equipped with spring brakes?

  1. It increases service brake pressure to hold the vehicle on a grade
  2. It locks the foot valve treadle in the applied position
  3. It supplies air to the spring brake chambers to hold the brakes off
  4. It exhausts air from the spring brake chambers so the springs apply the brakes Correct answer.

Explanation

Spring brakes are held off by air pressure and apply when that air is released, so the parking valve works by exhausting the spring brake circuit. Pulling the valve vents the chambers and the stored spring force applies the brakes. It does not add service pressure or mechanically lock the treadle.

Question 31Air Brake System Components and Operation

In a system with a dual foot valve, what happens to the secondary circuit if the primary circuit loses pressure?

  1. The secondary circuit continues to deliver air to its brake chambers, though at reduced total braking effort Correct answer.
  2. The secondary circuit also loses pressure because both circuits share one delivery port
  3. The secondary circuit is isolated until the vehicle stops and the system resets
  4. The secondary circuit is automatically vented to atmosphere to prevent drag

Explanation

A dual foot valve has separate supply and delivery sections so that a failure in one circuit still allows the other to apply its brakes. The driver retains partial braking, typically on a separate axle group, along with the spring brakes. The circuits do not share a single delivery port, and the healthy circuit is not vented or locked out.

Question 32Air Brake System Components and Operation

What is the function of the two-way check valve often installed in a dual-circuit system feeding a spring brake valve?

  1. It divides supply pressure equally between the two circuits at all times
  2. It drains condensate from the spring brake circuit
  3. It allows the higher of two control pressures to pass while blocking backflow to the other source Correct answer.
  4. It prevents the spring brakes from applying when the service brakes are released

Explanation

A two-way check valve compares two incoming signals and delivers whichever is higher while sealing off the lower-pressure side. This lets either circuit provide a control signal without losing air back into the failed circuit. It does not equalise supply, hold off spring brakes, or drain water.

Question 33Air Brake System Components and Operation

Which statement correctly describes the function of the tractor supply line in a tractor-trailer combination?

  1. It provides electrical power to the trailer ABS module
  2. It carries the service brake control signal from the foot valve to the trailer relay valve
  3. It returns exhausted air from the trailer chambers to the tractor
  4. It charges the trailer reservoirs and signals the tractor protection valve to stay open Correct answer.

Explanation

The supply line, often called the emergency line, charges the trailer's reservoirs and maintains the control pressure that keeps the tractor protection valve open during normal operation. The service line, by contrast, carries the brake application signal. The supply line does not return exhaust air or carry electrical power.

Question 34Air Brake System Components and Operation

A technician finds that the compressor cut-out pressure is 150 psi on a system whose safety valve is rated at 150 psi. What is the main risk of this setting?

  1. The low-pressure warning will activate during each cycle
  2. The safety valve may open during normal operation, venting air and masking a fault Correct answer.
  3. The compressor will short-cycle and overheat
  4. The spring brakes will release too slowly

Explanation

The safety valve must be set above the governor cut-out so it stays closed during normal charging. If cut-out equals or exceeds the safety valve setting, the valve vents air in routine operation, which wastes capacity and makes it useless as a fault indicator. Cut-out pressure does not govern compressor cycling speed, spring brake release timing, or low-pressure warning thresholds in this way.

Question 35Air Brake System Components and Operation

What is the purpose of the front axle limiting valve (front brake pressure limiter) on some heavy vehicles?

  1. To hold the front spring brakes off during parking
  2. To balance reservoir pressure between the front and rear circuits
  3. To reduce front brake pressure during hard applications to help maintain steering control Correct answer.
  4. To prevent the front brakes from releasing until the rear brakes release

Explanation

A front limiting valve caps the pressure delivered to the front chambers during hard stops, which reduces the chance of front wheel lockup and loss of steering control. It acts on the service application signal, not on release sequencing or reservoir balance. Front axle parking hold-off is not its function.

Question 36Air Brake System Components and Operation

Which component converts the driver's pedal force into a pneumatic control signal in a typical air brake foot valve?

  1. The relay valve piston
  2. The slack adjuster cam
  3. The compressor unloading mechanism
  4. The treadle and its internal graduating valves Correct answer.

Explanation

The foot valve treadle acts through a plunger and graduating valves that admit or exhaust air to produce a control pressure proportional to pedal travel. That signal is then relayed to the chambers. Relay valve pistons respond to the signal, slack adjusters are mechanical, and the unloading mechanism belongs to the compressor.

Question 37Air Brake System Components and Operation

A driver reports that the spring brakes will not release after the parking valve is pushed in, but the service brakes work normally. Which fault best fits these symptoms?

  1. A misadjusted automatic slack adjuster
  2. A blocked or leaking spring brake hold-off (emergency) circuit Correct answer.
  3. A leaking service brake chamber diaphragm
  4. A failed quick-release valve in the service circuit

Explanation

Spring brakes release only when hold-off air reaches their chambers, so a blockage or leak in the emergency/hold-off circuit keeps them applied even though the service circuit is healthy. The normal service brakes indicate the foot valve and service delivery paths are intact. Service chamber leaks, slack adjusters, and quick-release valves do not prevent hold-off air from releasing the springs.

Question 38Air Brake System Components and Operation

What is the correct function of the trailer emergency relay valve (spring brake control valve) when supply pressure is lost?

  1. It vents trailer service chambers to prevent overheating
  2. It applies the trailer spring brakes automatically as supply pressure falls Correct answer.
  3. It maintains trailer service brake pressure so the trailer can be towed
  4. It releases trailer spring brakes so the wheels can roll freely

Explanation

The trailer emergency relay valve monitors supply pressure and, when it drops below a threshold, exhausts the spring brake hold-off air so the trailer parks itself. This protects against a breakaway or lost supply line. It does not preserve service pressure for towing, release the springs, or vent service chambers.

Question 39Air Brake System Components and Operation

Why are brake chambers mounted with the pressure port oriented so that moisture and oil can drain away from the diaphragm?

  1. To allow condensate and oil to escape the chamber instead of pooling against the diaphragm Correct answer.
  2. To permit the spring to be installed without a cage bolt
  3. To reduce the pushrod stroke required for a given pressure
  4. To increase the effective diaphragm area and braking force

Explanation

Contaminants that collect against the diaphragm can degrade the rubber and cause leaks or sluggish operation, so chambers are installed with the port positioned to let moisture and oil drain. Orientation does not change diaphragm area, pushrod stroke geometry, or spring installation requirements.

Question 40Air Brake System Components and Operation

A vehicle has automatic slack adjusters, and the driver notices the parking brake will not hold on a grade even though the spring chambers are applying. Which cause is most consistent with this symptom?

  1. The governor cut-in pressure is set too low
  2. The slack adjusters are not maintaining correct pushrod stroke, leaving excess free travel Correct answer.
  3. The air dryer purge valve is stuck open
  4. The low-pressure warning switch is faulty

Explanation

Spring brake holding force reaches the foundation brakes through the pushrod and slack adjuster, so excess free travel or a stroke beyond the limit reduces the force at the shoe. Automatic slack adjusters that are not adjusting leave too much travel and weak parking hold. Governor settings, warning switches, and dryer purge faults do not reduce mechanical holding force in this way.

Question 41Initial Terminal Brake Tests (Class I / Class II / Class III)

Under the Class I initial terminal brake test, what air pressure must be present in the brake pipe before the test can begin?

  1. At least 90 psi Correct answer.
  2. At least 110 psi
  3. At least 60 psi
  4. At least 75 psi

Explanation

A Class I initial terminal brake test requires the brake pipe to be charged to a minimum of 90 psi at the rear of the train before the test sequence starts. This charge ensures every car's auxiliary and emergency reservoirs can fill and the brakes will set reliably. Lower pressures cannot guarantee full reservoir charging across a long train.

Question 42Initial Terminal Brake Tests (Class I / Class II / Class III)

On a train receiving a Class I initial terminal brake test, the brake pipe leakage must not exceed what rate?

  1. 5 psi per minute Correct answer.
  2. 8 psi per minute
  3. 10 psi per minute
  4. 3 psi per minute

Explanation

The maximum allowable brake pipe leakage for a Class I test is 5 psi per minute, measured after the system is fully charged and the angle cock is closed at the rear. This limit confirms the brake pipe and connections are sound enough to sustain pressure for the trip. Leakage above this rate indicates defective gaskets, hoses, or piping needing repair.

Question 43Initial Terminal Brake Tests (Class I / Class II / Class III)

During a Class I initial terminal brake test, how long must the brakes remain applied during the leakage test observation period?

  1. 30 seconds
  2. 5 minutes
  3. 1 minute Correct answer.
  4. 2 minutes

Explanation

After the brake pipe is reduced and the leakage test is performed, the brakes must be observed in the applied position for at least one minute to confirm they set and hold. This observation period verifies that no car releases prematurely or fails to apply. A full minute gives the inspector time to detect creeping or sticking brakes.

Question 44Initial Terminal Brake Tests (Class I / Class II / Class III)

What brake pipe reduction is typically used to set the brakes during a Class I initial terminal brake test?

  1. A 10 psi reduction
  2. A 5 psi reduction
  3. A 30 psi reduction
  4. A 20 psi reduction Correct answer.

Explanation

A 20 psi brake pipe reduction is the standard service application used to set the brakes for inspection during a Class I test. This reduction produces a full service brake application so the inspector can verify that every car's brakes apply and release properly. Smaller reductions may not fully set all brakes, and larger ones are unnecessary.

Question 45Initial Terminal Brake Tests (Class I / Class II / Class III)

Who is authorized to perform a Class II initial terminal brake test on a train being assembled?

  1. Only a certified car inspector
  2. Only the locomotive engineer
  3. A qualified mechanical or train service employee designated to perform the test Correct answer.
  4. Only the train conductor

Explanation

A Class II initial terminal brake test may be performed by a qualified mechanical or train service employee who has been designated and trained to conduct the test. The test does not require a certified car inspector in every case, but the person must be qualified. This flexibility allows terminals to complete tests without delaying trains.

Question 46Initial Terminal Brake Tests (Class I / Class II / Class III)

What is the primary purpose of an initial terminal brake test before a train departs its originating terminal?

  1. To measure the fuel consumption of the locomotive
  2. To check the wheel profile of each car
  3. To verify that the brake system is functioning properly on every car before departure Correct answer.
  4. To confirm the train's tonnage and length

Explanation

The initial terminal brake test confirms that the air brake system on each car applies and releases correctly before the train leaves its originating terminal. It is a safety function ensuring the train can be controlled and stopped en route. Tonnage, fuel, and wheel profile are separate inspections unrelated to the brake test.

Question 47Initial Terminal Brake Tests (Class I / Class II / Class III)

Which document records that a Class I initial terminal brake test was completed and the train is authorized to depart?

  1. The crew hours-of-service log
  2. The fuel and water report
  3. The brake test record or train consist documentation Correct answer.
  4. The locomotive daily inspection report

Explanation

Completion of a Class I initial terminal brake test is documented on the brake test record or in the train consist documentation, showing the test was performed and the results. This record provides accountability and a reference if the test is later questioned. Other reports cover different inspections and do not certify the brake test.

Question 48Initial Terminal Brake Tests (Class I / Class II / Class III)

When a Class III initial terminal brake test is performed, what distinguishes it from a Class I test?

  1. It applies only to single cars or cuts of cars moved short distances Correct answer.
  2. It eliminates the need to observe brake application
  3. It requires no brake pipe charge at all
  4. It requires a longer observation period than Class I

Explanation

The Class III test is a limited brake test applied to single cars or cuts of cars that are moved only short distances within a terminal or yard. It uses a simpler procedure than the full Class I test because the movement is limited. It does not eliminate the need to charge the brake pipe or observe brake application.

Question 49Initial Terminal Brake Tests (Class I / Class II / Class III)

After setting the brakes during a Class I test, the inspector releases the brake pipe and observes the brakes. What must be confirmed during the release portion of the test?

  1. That every brake releases fully and the brake pipe recharges Correct answer.
  2. That the brake pipe pressure drops to zero
  3. That the locomotive throttle is advanced
  4. That the hand brakes remain applied on all cars

Explanation

During the release portion of the Class I test, the inspector confirms that every car's brakes release fully and the brake pipe recharges to the required pressure. A brake that fails to release can cause dragging equipment, overheated wheels, or a flat spot. Confirming recharge also verifies the system is ready for service.

Question 50Initial Terminal Brake Tests (Class I / Class II / Class III)

An inspector performing a Class I test finds brake pipe leakage of 6 psi per minute. What is the correct action?

  1. Accept the train because leakage under 10 psi is allowed
  2. Release the brakes and depart immediately
  3. Repair the leakage before the train departs Correct answer.
  4. Reduce the brake pipe pressure and retest later

Explanation

Leakage of 6 psi per minute exceeds the 5 psi per minute maximum, so the defect must be found and repaired before the train can depart. Allowing the train to leave with excessive leakage risks losing brake pipe pressure en route. The inspector must locate and correct the leak, then retest.