You are coupling a tractor to a semi-trailer. You have connected the air lines. Before backing under the trailer, you should:

Supply air to the trailer system and lock the trailer brakes.. Section 6.4: Supply air to the trailer, then pull out the air supply knob to

You are coupling a tractor to a semi-trailer. You have connected the air lines. Before backing under the trailer, you should:

ANSWER BREAKDOWN
  • A. Correct. Supply air to the trailer, then pull out the air supply knob to lock the trailer brakes. This ensures the trailer won't move when you back under it.
  • B. Incorrect. "Drive away." is not correct. Supply air to the trailer, then pull out the air supply knob to lock the trailer brakes. This ensures the trailer won't move when you back under it.
  • C. Incorrect. "Disconnect the electrical cable." is not correct. Supply air to the trailer, then pull out the air supply knob to lock the trailer brakes. This ensures the trailer won't move when you back under it.
  • D. Incorrect. "Lower the landing gear." is not correct. Supply air to the trailer, then pull out the air supply knob to lock the trailer brakes. This ensures the trailer won't move when you back under it.