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FL CDR Sample Questions Modules 9-15
Actual Exam 2026/2027 – Complete Exam-
Style Questions with Detailed Rationales |
Pass Guaranteed – A+ Graded
[SECTION 1: Air Brakes (Module 9) — Questions 1-20]
Q1: What is the purpose of the air compressor governor in an air brake system?
A. To regulate the air pressure in the air tanks and control when the compressor cuts in and cuts
out.
B. To compress the air and send it to the service brake chambers.
C. To release the spring brakes when the air pressure drops.
D. To filter the air to remove moisture and oil.
Correct Answer: A
Rationale: The governor controls the air compressor by starting it (cut-in) when pressure drops to
about 100 psi and stopping it (cut-out) when it reaches 125 to 130 psi. This prevents the system
from building excessive pressure and ensures a steady supply. Option B is the compressor's job,
not the governor. Option C is the function of the modulator valve or foot valve. Option D is the
air dryer's function.
Q2: In a dual air brake system, if one air system loses pressure (e.g., a leak in the rear), what
typically happens to the other system?
A. The front brakes will also fail immediately.
B. The other system will remain operational, allowing you to use half of the brakes.
C. The governor will fail to cut out, causing an overpressure condition.
D. The tractor protection valve will automatically seal the service line.
Correct Answer: B
Rationale: Dual air systems (primary and secondary) are designed to be independent so that if
one system fails, the other can still provide braking power to at least half of the wheels. While
stopping distance increases, you still have some braking ability. Option A describes a single
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system failure. Option D is incorrect regarding the tractor protection valve's function in this
specific failure mode.
Q3: What is the maximum air loss rate allowed for a combination vehicle (tractor and trailer)
during a static leak test with the brakes applied?
A. 1 psi per minute
B. 2 psi per minute
C. 3 psi per minute
D. 4 psi per minute
Correct Answer: C
Rationale: For a combination vehicle, the maximum allowable leak rate with the brakes applied
is 3 psi per minute. A rate higher than 3 psi indicates a leak in the system that must be repaired.
Options A and B are the limits for tractors or single vehicles respectively. Option D is generally
considered a failure for any vehicle type.
Q4: When should the low air pressure warning signal (light and buzzer) activate?
A. Between 20 and 45 psi
B. Between 55 and 60 psi
C. When the air pressure drops below 10 psi
D. Immediately when the engine is turned off
Correct Answer: B
Rationale: Federal standards require the low air pressure warning device to activate at a pressure
above 60 psi (usually between 55 and 60 psi) to give the driver warning before reaching the
danger zone where spring brakes activate. Option A is the range where spring brakes engage.
Option C is too late for a warning system to be effective.
Q5: Which of the following best describes the proper procedure for a static air brake test?
A. Build pressure to cut-out, shut off the engine, chock wheels, apply brakes firmly, and hold for
one minute.
B. Pump the brakes rapidly to heat them up, then check the governor cut-out.
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C. Drive forward at 5 mph, apply brakes, and measure the stopping distance.
D. Inspect the slack adjusters while the engine is running.
Correct Answer: A
Rationale: The static air brake test (leak test) requires building air pressure to governor cut-out,
turning off the engine to prevent air replenishment, chocking the wheels, and then applying the
brakes fully to measure the pressure drop over one minute. Option C describes a moving test.
Option D is part of the inspection, not the specific air loss test.
Q6: What is the function of the safety valve on the air compressor?
A. To release air from the brake chambers to release the brakes.
B. To prevent the air pressure from rising above a safe maximum (usually 150 psi).
C. To drain moisture from the wet tank.
D. To control the flow of air to the trailer brakes.
Correct Answer: B
Rationale: The safety valve is a fail-safe mechanism set to open at a specific pressure (usually
150 psi) to prevent tank explosions or burst lines if the governor fails to cut out the compressor.
Option A is the function of the relay valve or foot valve. Option C is the function of the drain
valves.
Q7: Automatic slack adjusters should be checked to ensure:
A. The push rod travel is within the manufacturer's specified range (usually 1/2 to 3/4 inch).
B. They are fully tightened and locked with zero play.
C. They are disconnected during a pre-trip inspection.
D. The brake drum is cold to the touch.
Correct Answer: A
Rationale: Slack adjusters maintain the correct clearance between the brake lining and drum.
There must be a specific amount of push rod travel (usually indicated by a marking or lines on
the slack adjuster); if the travel is too long, the brakes are out of adjustment. Option B is
incorrect because brakes need some free play. Option D is irrelevant to adjustment.
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Q8: Why do air brakes take longer to stop a vehicle than hydraulic brakes?
A. Because air brakes require more physical force from the driver.
B. Because of the "lag time" it takes for air to flow through the lines to the brake chambers.
C. Because air brakes only work on the rear wheels.
D. Because air compressors are slower than hydraulic pumps.
Correct Answer: B
Rationale: There is a delay (lag time) of roughly half a second for the air to travel from the foot
valve through the lines to the brake chambers, unlike hydraulic fluid which acts instantly. This
requires drivers to brake sooner than they would with hydraulic brakes. Options A and C are
factually incorrect regarding the mechanics.
Q9: What happens if the air pressure drops to around 20-45 psi?
A. The low air warning device will turn off.
B. The spring brakes (parking/emergency brakes) will automatically engage.
C. The service brakes will lock up.
D. The air compressor will start working faster.
Correct Answer: B
Rationale: When air pressure drops to this low range, the spring brakes are designed to
automatically apply to stop the vehicle, as the service brakes cannot be held reliably by the low
air pressure. This is a critical safety feature known as the "emergency brake" portion of the
spring brake system. Option A is incorrect as the light stays on or the engine stops.
Q10: Which type of brake is commonly found on the front wheels of tractors to help prevent
skidding?
A. S-cam brakes
B. Wedge brakes
C. Disc brakes
D. Drum brakes
Correct Answer: C
FL CDR Sample Questions Modules 9-15
Actual Exam 2026/2027 – Complete Exam-
Style Questions with Detailed Rationales |
Pass Guaranteed – A+ Graded
[SECTION 1: Air Brakes (Module 9) — Questions 1-20]
Q1: What is the purpose of the air compressor governor in an air brake system?
A. To regulate the air pressure in the air tanks and control when the compressor cuts in and cuts
out.
B. To compress the air and send it to the service brake chambers.
C. To release the spring brakes when the air pressure drops.
D. To filter the air to remove moisture and oil.
Correct Answer: A
Rationale: The governor controls the air compressor by starting it (cut-in) when pressure drops to
about 100 psi and stopping it (cut-out) when it reaches 125 to 130 psi. This prevents the system
from building excessive pressure and ensures a steady supply. Option B is the compressor's job,
not the governor. Option C is the function of the modulator valve or foot valve. Option D is the
air dryer's function.
Q2: In a dual air brake system, if one air system loses pressure (e.g., a leak in the rear), what
typically happens to the other system?
A. The front brakes will also fail immediately.
B. The other system will remain operational, allowing you to use half of the brakes.
C. The governor will fail to cut out, causing an overpressure condition.
D. The tractor protection valve will automatically seal the service line.
Correct Answer: B
Rationale: Dual air systems (primary and secondary) are designed to be independent so that if
one system fails, the other can still provide braking power to at least half of the wheels. While
stopping distance increases, you still have some braking ability. Option A describes a single
,2
system failure. Option D is incorrect regarding the tractor protection valve's function in this
specific failure mode.
Q3: What is the maximum air loss rate allowed for a combination vehicle (tractor and trailer)
during a static leak test with the brakes applied?
A. 1 psi per minute
B. 2 psi per minute
C. 3 psi per minute
D. 4 psi per minute
Correct Answer: C
Rationale: For a combination vehicle, the maximum allowable leak rate with the brakes applied
is 3 psi per minute. A rate higher than 3 psi indicates a leak in the system that must be repaired.
Options A and B are the limits for tractors or single vehicles respectively. Option D is generally
considered a failure for any vehicle type.
Q4: When should the low air pressure warning signal (light and buzzer) activate?
A. Between 20 and 45 psi
B. Between 55 and 60 psi
C. When the air pressure drops below 10 psi
D. Immediately when the engine is turned off
Correct Answer: B
Rationale: Federal standards require the low air pressure warning device to activate at a pressure
above 60 psi (usually between 55 and 60 psi) to give the driver warning before reaching the
danger zone where spring brakes activate. Option A is the range where spring brakes engage.
Option C is too late for a warning system to be effective.
Q5: Which of the following best describes the proper procedure for a static air brake test?
A. Build pressure to cut-out, shut off the engine, chock wheels, apply brakes firmly, and hold for
one minute.
B. Pump the brakes rapidly to heat them up, then check the governor cut-out.
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C. Drive forward at 5 mph, apply brakes, and measure the stopping distance.
D. Inspect the slack adjusters while the engine is running.
Correct Answer: A
Rationale: The static air brake test (leak test) requires building air pressure to governor cut-out,
turning off the engine to prevent air replenishment, chocking the wheels, and then applying the
brakes fully to measure the pressure drop over one minute. Option C describes a moving test.
Option D is part of the inspection, not the specific air loss test.
Q6: What is the function of the safety valve on the air compressor?
A. To release air from the brake chambers to release the brakes.
B. To prevent the air pressure from rising above a safe maximum (usually 150 psi).
C. To drain moisture from the wet tank.
D. To control the flow of air to the trailer brakes.
Correct Answer: B
Rationale: The safety valve is a fail-safe mechanism set to open at a specific pressure (usually
150 psi) to prevent tank explosions or burst lines if the governor fails to cut out the compressor.
Option A is the function of the relay valve or foot valve. Option C is the function of the drain
valves.
Q7: Automatic slack adjusters should be checked to ensure:
A. The push rod travel is within the manufacturer's specified range (usually 1/2 to 3/4 inch).
B. They are fully tightened and locked with zero play.
C. They are disconnected during a pre-trip inspection.
D. The brake drum is cold to the touch.
Correct Answer: A
Rationale: Slack adjusters maintain the correct clearance between the brake lining and drum.
There must be a specific amount of push rod travel (usually indicated by a marking or lines on
the slack adjuster); if the travel is too long, the brakes are out of adjustment. Option B is
incorrect because brakes need some free play. Option D is irrelevant to adjustment.
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Q8: Why do air brakes take longer to stop a vehicle than hydraulic brakes?
A. Because air brakes require more physical force from the driver.
B. Because of the "lag time" it takes for air to flow through the lines to the brake chambers.
C. Because air brakes only work on the rear wheels.
D. Because air compressors are slower than hydraulic pumps.
Correct Answer: B
Rationale: There is a delay (lag time) of roughly half a second for the air to travel from the foot
valve through the lines to the brake chambers, unlike hydraulic fluid which acts instantly. This
requires drivers to brake sooner than they would with hydraulic brakes. Options A and C are
factually incorrect regarding the mechanics.
Q9: What happens if the air pressure drops to around 20-45 psi?
A. The low air warning device will turn off.
B. The spring brakes (parking/emergency brakes) will automatically engage.
C. The service brakes will lock up.
D. The air compressor will start working faster.
Correct Answer: B
Rationale: When air pressure drops to this low range, the spring brakes are designed to
automatically apply to stop the vehicle, as the service brakes cannot be held reliably by the low
air pressure. This is a critical safety feature known as the "emergency brake" portion of the
spring brake system. Option A is incorrect as the light stays on or the engine stops.
Q10: Which type of brake is commonly found on the front wheels of tractors to help prevent
skidding?
A. S-cam brakes
B. Wedge brakes
C. Disc brakes
D. Drum brakes
Correct Answer: C
