Kentucky CDL Air Brakes Practice Test (KY) 2

5 out of 5 (44 votes)
80% Passing score
20 Questions
4 Mistakes allowed
Welcome to our KY permit practice test for air brakes, a no-pressure way to prepare for your CDL air brakes endorsement. This test, written and reviewed by seasoned driving instructors, offers a thorough review of all necessary topics to ensure you are ready for the real thing. You'll encounter 20 multiple-choice questions on components, operation, safety inspections, and stopping distance calculations. As any Kentuckian knows, the Bluegrass State's diverse driving conditions-from the winding Appalachian roads to the bustling streets of Louisville-demand a solid understanding of your vehicle's air brake system. Our Kentucky permit test practice delves into essential facts, like the use of dual air brake systems, which provide a backup if one system fails, enhancing your safety on KY's varied terrain. This Kentucky CDL air brake practice test is designed to be comprehensive and user-friendly. With each question, you'll gain deeper insight into critical air brake operations and safety protocols. The end-of-test summaries are particularly beneficial, offering a detailed review of your performance, pinpointing any mistakes, and providing correct answers to aid in your learning process. In KY, the weather can be unpredictable, with frequent rain and occasional snow affecting road conditions. Our CDL air brakes practice test includes questions that address these real-world scenarios, ensuring you're prepared to handle any situation. With a passing score of 80%, or 16 out of 20 questions, you'll feel confident in your knowledge and ready to tackle the official CDL test. Whether you're navigating the scenic byways of the Daniel Boone National Forest or hauling goods through the state's agricultural heartland, having a thorough understanding of air brakes is crucial. Our Kentucky DMV air brake test provides the perfect environment to master this knowledge without the stress of the actual test day. So, take your time, absorb the information, and utilize the end-of-test summaries to fine-tune your understanding. Our practice permit test is your key to acing the CDL air brake endorsement and driving safely across KY's diverse landscapes.
FREE CDL Practice Test App
Pass your Kentucky CDL Air Brake test with the NextDoorDriving app. Real questions and answers—100% free and ad-free.
Download on the App Store

Sample Kentucky Air Brakes Test Questions

Question 1

A visible low-air-pressure warning must activate before tank pressure falls below:

  1. A 40 psi
  2. B 50 psi
  3. C 55 psi
  4. D 90 psi

Correct answer: C – 55 psi

The Kentucky CDL manual requires the visible low-air warning to activate before tank pressure drops below 55 psi. Federal equipment rules likewise specify a continuous audible or visible warning at 55 psi and below for covered air-brake systems. Spring brakes generally begin applying later, when pressure falls into the manufacturer’s specified 20-to-45-psi range.

Source: Kentucky Commercial Driver’s License Manual — § 5.1.11, “Low Air Pressure Warning”, 49 CFR § 393.51(c) — Warning signals, air pressure and vacuum gauges

Question 2

What is the function of an air compressor governor?

  1. A It controls when the compressor pumps air into the storage tanks
  2. B It determines how much braking force the pedal applies
  3. C It measures brake lining thickness
  4. D It regulates engine speed during braking

Correct answer: A – It controls when the compressor pumps air into the storage tanks

The governor starts and stops the compressor’s air-pumping cycle according to tank pressure. The Kentucky CDL manual identifies approximately 100 psi as the cut-in pressure and 125 psi as the cut-out pressure. Brake application pressure is controlled through the brake pedal, not by the governor.

Source: Kentucky Commercial Driver’s License Manual — § 5.1.2, “Air Compressor Governor”

Question 3

The S-cam drum brake is the most common type of foundation brake on air-brake vehicles. True or false?

  1. A True
  2. B False

Correct answer: A – True

Foundation brakes are located at the wheels, and the S-cam drum design is the most common type. Air pressure moves the pushrod and slack adjuster, rotating the S-cam. The cam forces the brake shoes against the inside of the drum to create friction and slow the vehicle.

Source: Kentucky Commercial Driver’s License Manual — § 5.1.8, “Foundation Brakes”

Question 4

Before leaving an air-brake vehicle parked and unattended, how must it be secured?

  1. A Leave the transmission in neutral without applying any brakes
  2. B Apply the parking brakes or use wheel chocks when conditions require them
  3. C Wait for low air pressure to apply the spring brakes automatically
  4. D Hold the service brake pedal down

Correct answer: B – Apply the parking brakes or use wheel chocks when conditions require them

The Kentucky CDL manual says never to leave a vehicle unattended without applying the parking brakes or chocking the wheels. Parking brakes should normally be used whenever the vehicle is parked. Wheel chocks are used when very hot brakes must cool or when wet brakes could freeze, because applying the parking brakes under those conditions may cause damage or prevent movement later.

Source: Kentucky Commercial Driver’s License Manual — §§ 5.1.15 and 5.4.6, “Parking Brake Controls” and “Parking Brakes”

Question 5

Which additional factor increases the total stopping distance of an air-brake vehicle?

  1. A Perception distance
  2. B Driver reaction distance
  3. C Brake lag distance
  4. D Tire inspection distance

Correct answer: C – Brake lag distance

Air brakes do not act immediately when the pedal is pressed because compressed air must travel through the lines to the brake chambers. This delay is called brake lag. Total stopping distance for an air-brake vehicle includes perception distance, reaction distance, brake lag distance, and braking distance.

Source: Kentucky Commercial Driver’s License Manual — § 5.4.4, “Stopping Distance”

Question 6

Which condition can reduce the effectiveness of both service brakes and spring-operated parking or emergency brakes?

  1. A A low hydraulic-fluid level
  2. B Brakes that are out of adjustment
  3. C An illuminated ABS malfunction lamp alone
  4. D Normal governor cut-out pressure

Correct answer: B – Brakes that are out of adjustment

Spring-brake effectiveness depends on proper brake adjustment. When brakes are not adjusted correctly, the regular service brakes and the emergency or parking brakes may not work properly. An ABS malfunction does not eliminate normal braking, while hydraulic fluid is not part of a full air-brake system.

Source: Kentucky Commercial Driver’s License Manual — § 5.1.14, “Spring Brakes”

More Kentucky CDL Practice Tests
Other CDL Endorsements