Destruction due to turbulence when below Va - how?

Capt.Doug wrote:
It depends on the structure. The T-28 Trojan was used by the South
Vietnamese in their conflict for ground attack roles. The pilots were
pulling the wings off much too often and the engineers couldn't understand
because those wings should support a battleship. It turns out that the
horizontal stabilizer was actually the first component to fail. After it
failed, the plane would pitch over with enough force to break the wings off.
This happens in less than a second. Once the engineers understood the
problem and strenghtened the horizontal stabilizer, the problem went away.

T-28 breaking point occurs at 428 kts. (As related to me by a retired
North American engineer many years ago.)