Maybe this is a question more appropriate for airliners.net, but since I'm not a member over there, I thought I would pose the question here.  On the MD-11 you have the longitudinal stability assist, which also includes an attitude hold feature within some pitch limits.  I've noticed that real MD-11 pilots, in discussion of Control Wheel Steering are keen to point out that the MD-11 has optional CWS in the Roll axis ONLY, which some operators have disabled, because they consider it a pain.  Yet for all practical purposes, couldn't an airplane that automatically holds a pitch attitude using automated elevator and trim inputs, be considered to have Pitch CWS.  You point the nose up or down and the automation will hold it there.  Is this just splitting hairs, or is there a specific reason why, from the pilot's perspective, the LSAS+att.hold function would be considered much different than plain old Pitch CWS?

CWS is an autopilot mode. You use it to make a temporary change to whatever the autopilot is doing. Whereas this LSAS+att.hold sounds like assisted manual flying. Not unlike manual flight on fly by wire aircraft.

CWS is an autopilot mode. You use it to make a temporary change to whatever the autopilot is doing. Whereas this LSAS+att.hold sounds like assisted manual flying. Not unlike manual flight on fly by wire aircraft.

 

You would think that LSAS just makes a few tweaks to keep things stable, but in fact LSAS comes with Attitude Hold as one of it's functions, and you can't turn just that function off without disabling LSAS entirely.  So from the pilot's standpoint, regular pitch control in the MD-11 is almost exactly the same as flying the NG(X)  with Pitch CWS engaged.  They both allow you to point the nose with the yoke, and it stays there, due to automated control inputs and/or automated trim.  Both give the illusion of neutral stability about the CG.  Still don't really see the distinction why one is considered CWS and the other isn't.

Ok, let me try again. CWS is an interruption mode. By pressing down the cws button, you interrupt whatever the autopilot is doing and allow you to freely move the yoke. If not holding down the cws, the autopilot is in full control and the yoke cannot be freely manipulated by the pilot. Whereas any kind of SAS is something which helps an already freely and manually controlled yoke to control the plane easier.