Owain:
I went back to sketch, and yes, I should have been looking more like 300 or more. Came back to your post, thanks for the 400.
By lost control authority I meant 'move your flight control X amount' (by telling the Flght Control computers to move it as far as it will go) and get less response than what will change your pitch, or get no change.
Go to full deflection (or largest allowed command) and get less change than needed, or none.
That to me is loss of control authority. I may be using the term in a non standard way.
Part of what was in the back of my mind as I typed that was that each knot lost costs you lift/force as the square of the velocity lost, roughly. I move the stick and expect a response, don't get one, so keep moving the stick more to try and get it to respond at all ... mind goes back to the old slow flight demonstrations, and how "sloppy" the control responses are compared to cruise flight.
Rudder travel limits are a built in control authority limit. (To avoid damage to tail). That's an intentional limit to control authority. What I was thinking about was inadvertent loss of control authority in the pitch channel due to loads/forces being insufficient for the amount of force needed to change pitch.
Also in the back of my mind as I wrote that is a
loss of control authority problem in helicopter tail rotors, where you put controls to full deflection but are unable to overcome the torque due to limitations on control surface travel (or tail rotor blade stall). In that case, your authority over your nose, (yaw) is lost, since it goes one way while you are trying to get it to go the other way, or just stop it from moving.
As I said in that earlier posting, without significant and continued up elevator application, even with the THS at -13 deg, you won't get any nose up pitch from the back end above about 26 deg AoA. Well maybe I didn't actually SAY that, but it is implicit in my argument. 26 deg is more than enough to stall the aeroplane of course, but AF447 has been linked to much larger values of AoA that, IMHO, can only be achieved with up elevator. I will leave it to others to argue whence came that up elevator.
Thanks for the clarification.
