To perform the pre-trip inspection of the air brakes, which of the following should you do first?
- Fan (pump) the brakes.
- Drain the air tanks.
- Start the engine.
- Block (chock) the wheels. ✓
Answer: D. Block (chock) the wheels.
First, block (chock) the wheels to secure the vehicle before you begin the air-brake inspection.
Why this is the answer
The Air Brake Handbook says to conduct the inspection on level ground, apply the spring brakes and put wheel chocks or blocks in place to secure the vehicle. It also warns that some air-brake inspection steps are done with the parking brakes released, so the vehicle must be secured against movement first. Among the choices given, blocking the wheels is the safety step that comes before running brake tests or handling the air system.
Why the other answers are wrong
- A. Fan (pump) the brakes. — Fanning the brakes is part of testing the system, and the passages say to secure the vehicle with chocks before procedures that may require the parking brakes to be released.
- B. Drain the air tanks. — Draining the air tanks is not the first safety step; the handbook first calls for parking on level ground and securing the vehicle against movement.
- C. Start the engine. — Starting the engine is wrong here because the inspection precautions say to turn off the engine and keep it stopped during the inspection.
Remember it
Think park, set, chock: get the vehicle level and secured before you touch the brake tests.