Originally Posted by Luc Lion
Why adding a spring ?
There is already an Elevator Feel System (EFS) which is controlled by a calculator, the Elevator Feel Computer module, thus it is controlled by software.
The Elevator Feel Computer in all models of the B737 is a
mechanical computer. It shown in the drawing you posted. It varies elevator feel by using pitot pressure to regulate hydraulic pressure to an actuator which tensions a spring. The faster you fly the stiffer the elevator feels to the pilot. No software involved!
Dave.