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If the HS is ever free to move about it's pivot point (ie sans jackscrew) it will align itself with the oncoming air (weathervaning), not slam to one or the other stop. It's takes the path of least resisitence."
If the jackscrew lower trunnion fails, the HS may initially align itself to the dominant airflow, but the remainng
JS may then jam ( especially if the PF tries to correct a sudden change in pitch) on some part of the supporting structure and cause the HS to create max upthrust on the tail.
Rather like accidentally switching off your car ignition key, causing the lock to operate and jam the steering wheel unless you wiggle it to release the lock.)
Witness marks of the end of
JS having flailed around might support that suggestion, however unlikely a 'cheese hole' it might be.