Why is using the trailer hand brake not advisable when trying to straighten out a jackknifing trailer?

The use of the trailer hand brake when attempting to straighten out a jackknifing trailer is not advisable primarily because it makes the situation harder to control. When a trailer is in a jackknife position, the angle between the truck and the trailer creates instability and risks of losing control. Engaging the hand brake applies force specifically to the trailer wheels, which may exacerbate the angle or load on the trailer, potentially causing it to swing even more sharply. This can lead to an increased risk of further jackknifing or even a complete loss of control.

The other choices touch on aspects that might occur in certain scenarios, but they do not capture the overarching principle that the act of engaging the trailer brakes at a critical moment of instability mainly complicates the driver’s ability to regain control. Maintaining balance and managing the pivot point is crucial in such situations, making it critical to use engine power and steer rather than applying the trailer brakes.