Gord Beaman wrote
Really?, I'd have thought that the 707 (and maybe DC-9 too) would
have had powered controls?...

Rudder...yes, Ailerons and Elevator...no.
In fact, the two elevators were not connected to each other. It was
not unusual to see a taxing 707 with one elevator up and the other
one down. Each positioned by a control tab, the left one by the left
yoke and the right one by the right yoke. The two yokes were connected
under the cockpit by a coupler that would slip if forced. Airflow
would cause the tabs to "fly" the elevators to the commanded position.
The ailerons operated in a somewhat similiar fashion.

Bob Moore
ATP B-707 B-727
PanAm (retired)