Ethiopian airliner down in Africa

[threemiles]

Originally Posted by DaveReidUK

You could make the same argument for flaps being classed as primary flight controls, but they aren't either. A stabilator is, though.

https://www.skybrary.aero/index.php/Flight_Controls

Flaps and slats are not controls. Stab trim is an indirect control that is not driven by the yoke (direct control) but by a wheel. Its aerodynamic effect is the same though differently scaled.
Certification of flaps and slats is along the same principles when it comes to an automated aircraft system retracting or driving them.
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