When should you lower the landing gear when uncoupling a truck-tractor from a semi-trailer?

When should you lower the landing gear when uncoupling a truck-tractor from a semi-trailer?

• A. Before chocking the semi-wheel
• B. After you move the tractor-truck ahead so that the fifth wheel just clears the semi-trailer
• C. Before disconnecting the electrical and air lines and unlocking the fifth wheel
• D. After you move the tractor-truck ahead so that the fifth wheel just clears the semi-trailer

Answer: (C)

The important idea is that the trailer must be supported and stable before you disconnect anything from the tractor. Lowering the landing gear so the trailer rests on its own legs takes the weight off the hitch, which prevents the trailer from dropping or shifting when you release the fifth wheel and disconnect the air and electrical lines. This stability is what keeps uncoupling safe and controlled, allowing the tractor to back away cleanly once the coupling is released.

The important idea is that the trailer must be supported and stable before you disconnect anything from the tractor. Lowering the landing gear so the trailer rests on its own legs takes the weight off the hitch, which prevents the trailer from dropping or shifting when you release the fifth wheel and disconnect the air and electrical lines. This stability is what keeps uncoupling safe and controlled, allowing the tractor to back away cleanly once the coupling is released.