Originally Posted by
Fursty Ferret
In normal law it's always in trim so why would you want feedback? If you want to fly at the edge of the envelope or below VLS, you'll have to apply continual back pressure on the stick, which is quite a lot of force to hold (or it is for my spaghetti noodle arms).
I think this thread is about the A220/C-series and their different control laws which apparently (I’m not on type) have speed stability baked in now? Maybe someone who is rated could comment more authoritatively?
The 777 and 787 use springs and cam-roller mechanisms to provide pitch feel. At higher airspeeds, the feel and centering mechanism increases the forces by increasing the preload on the springs. The backdrive actuators are active only when the autopilot is engaged or when flight envelope protections are active. The springs are never overridden.
It's possible to measure the column force regardless of how the feel and centering is accomplished. The force transducers are in series between the controls and the feel and centering mechanisms. Control forces are required FDR parameters since 2009 (IIRC). That means that 767s and 737s have to measure it as well. Even aircraft from the 60s have force transducers; they're needed for the control wheel steering mode of the autopilot.
So to comparing with the Airbus implementation it is somewhat dissimilar in that a) the ‘neutral point’ is variable, controlled by actuators and b) the force required to move the controls is also variable and is mostly speed related. Similar flight control laws but very different user interface?