SGI SGI Air Brakes Endorsement 1 — Questions and Answers
Question 1: What is the minimum air pressure required before a driver can move an air brake-equipped vehicle?
- 100 psi (Correct answer)
- 60 psi
- 50 psi
- 120 psi
Correct answer: 100 psi
The air pressure must build to at least 100 psi before the vehicle is safe to move, ensuring adequate braking pressure is available.
Question 2: What does the low air pressure warning device activate at?
- 60 psi or below (Correct answer)
- 100 psi
- 80 psi
- 40 psi
Correct answer: 60 psi or below
The low air pressure warning (buzzer or light) activates when reservoir pressure drops to 60 psi or below, alerting the driver.
Question 3: What happens if air pressure drops below approximately 20–45 psi in a spring brake system?
- The spring brakes apply automatically (Correct answer)
- The service brakes apply automatically
- Nothing happens until the driver brakes
- The air dryer activates
Correct answer: The spring brakes apply automatically
Spring brakes apply automatically when reservoir air pressure drops too low, preventing the vehicle from moving without adequate brake pressure.
Question 4: What is the purpose of the air dryer in an air brake system?
- To remove moisture and contaminants from compressed air (Correct answer)
- To increase brake pressure
- To cool the air reservoirs
- To power the spring brakes
Correct answer: To remove moisture and contaminants from compressed air
The air dryer removes moisture and oil from the compressed air before it enters the reservoirs, preventing corrosion and freeze-ups.
Question 5: During a pre-trip inspection, what should the static air leakage test measure?
- Air pressure drop over one minute with engine off and brakes applied (Correct answer)
- Air pressure at full engine speed
- Time for pressure to build from 0 to 100 psi
- Pressure at each individual wheel
Correct answer: Air pressure drop over one minute with engine off and brakes applied
The static leakage test checks that pressure does not drop more than 4 psi per minute (single vehicle) with brakes applied and engine off.
Question 6: What is brake fade, and when does it occur?
- Reduction in braking effectiveness due to heat build-up from overuse (Correct answer)
- Sudden brake failure due to moisture
- Increase in brake pressure at high speeds
- Vibration in the brake pedal
Correct answer: Reduction in braking effectiveness due to heat build-up from overuse
Brake fade occurs when repeated or prolonged braking generates excessive heat, reducing the friction material's ability to slow the vehicle.
SGI SGI Air Brakes Endorsement 1
What is the minimum air pressure required before a driver can move an air brake-equipped vehicle?