What do you mean by "sustainabilty"?
Aircraft sustainability is:
the ability of an a/c to remain viable under current current social, economical and environmental constraints.
In other words the a/c has to be competitive by addressing the 3 things above.
An example would be: taking out old steam gauges and replacing them with a glass cockpit with integrated systems etc. I will not list all the benefits. I'm sure you get what I mean. Obviously with avionics its easy. But with control surfaces there is only so much I can think of...
How about a torque tube so that at low speeds the control input directly moves the control surfaces but at high speeds it moves a servo tab which then displaces the control surface.
Sounds very interesting. Could you please elaborate a little bit on that if you can so I can describe the system in a little more detail. And what benefits it would have etc. Thanks again.