What is a commonly accepted fact regarding aircraft harnesses?

Harnesses in aircraft are designed to enhance safety and provide restraint to occupants during flight, especially during turbulence or accidents. The statement that none can effectively prevent head flailing captures a significant aspect of aviation safety. In high-impact situations or sudden maneuvering, even the best harness systems may not fully inhibit the movement of the head, particularly if there is a rapid change in direction or a severe jolt. This can lead to potential head injuries, as the head remains vulnerable to unrestrained motion despite the use of a harness.

Other elements of harness functionality support the context for this question. For example, while some harness designs may improve retention during negative G forces or reduce the risk of submarining (where the body slides under the lap belt), these features can vary widely based on the harness type. Moreover, while a well-fitted harness is important for safety, it must be balanced with the physics of impact, where excessive tightness can indeed lead to dynamic overshoot—an event where an occupant's body can move forward beyond a safe limit due to the sudden cessation of motion.