autopilots should be and are designed to disengage the servos on GA button press.
The King ones remove the power to the servos when the red button is pressed and while it is being held. More info here
That feature is responsible for the premature demise of the red button switch – it is not able to carry the inductive loads and the resultant arcing.
Peter wrote:
autopilots should be and are designed to disengage the servos on GA button press.
The King ones remove the power to the servos when the red button is pressed and while it is being held. More info here
That feature is responsible for the premature demise of the red button switch – it is not able to carry the inductive loads and the resultant arcing.
Are you not confusing CWS with TOGA?
Oh yes.
The King APs don’t disconnect servo power on a TOGA press. The TOGA button is software monitored only. It changes AP modes and flips the flight director to something like a 10deg UP position.
The Cirrus has no CWS, even in the GFC700 version, which is a shame as I find it useful for taking momentary manual control without excessive button pressing.
Apparently, CWS is not possible on the Cirrus sidestick setup, due to the servos operating the trim rather than the main control surfaces. I wonder if they overlooked this implication during the initial design, or just decided that most people never use CWS anyway.
I don’t know of any G1000 that allows coupled missed approaches ie both the Meridian and Mustang pressing TO/GA commands pitch up wings level, changes CDI to GPS mode and disconnects autopilot. You then assuming you want to fly the published missed pitch up, add power, clean up, hit NAV then engage the autopilot then a vertical mode if pitch is not what you want.
The new G3000 in the M600 piper is supposed to allow fully coupled missed approaches so the autopilot doesn’t disconnect. Not sure how I feel about that in aircraft without autothrottles.
I never really use CWS I have to admit. I would be interested in more discussion of when others find it really useful.
I don’t use CWS. Can’t think of a reason why other than I clearly don’t feel the need.
I have found CWS useful for reaching the operating ceiling.
The AP can’t do it alone in PIT mode, let alone the VS mode.
The stall warner is usually going 
FL200-210, less with a full load and ISA+
The version of Garmin Perspective (effectively G1000) with envelope protection will keep the autopilot engaged on TOGA. And will not pitch up to an unsafe airspeed if the throttles aren’t advanced, so I think that is safe enough.
CWS is useful when messing around VFR, eg. to temporarily manoeuvre around conflicting traffic or make a small level change. I’ve seen it used IFR to command a new pitch, but I don’t see what is wrong with using the up/down wheel on the AP control panel for this, unless perhaps if you need to increase rate of descent/climb very quickly (ie you just got something else wrong beforehand!).
With the S-Tec 55x, the CWS is a funny function which had my pilots quite puzzled at first, so hardly anyone used it. By now, I use it quite a lot and love it.
What it does is a bit non standard:
With the CWS button pressed, you can control the airplane by hand to put it into a turn rate and VS you like. When you release the button, it stays in that turn rate (unless it is excessive, which the AP will correct to 90% of a standard rate turn) and maintain that VS. You can further modify the VS while it is in that mode, which is quite practical in certain situations.
For instance, if I am instructed to fly 360ties in position (on a VFR approach this happens for spacing some times) I will press the CWS button, turn the plane to approximately 15° bank and release it, then zero out the VS which displays on the mode control panel. Until I tell it otherwise, the AP will keep the airplane in a 360 turn with constant turn rate and holds the altitude.
GFC700 is the same, I think it’s standard CWS behaviour?
Instructing the autopilot by flying to the attitude/behaviour you want, with a single temporary button press and eyes outside, is sometimes nicer than a bunch of button presses, eyes inside, to reconfigure it after you disconnected it completely.
