Questions on CWS Autopilot Mode

[Big_Les 1]

What's the difference between CWS A and B?

Functionally, with no failures, nothing. There just different semi autonomous systems for safety.

[Spin737 102]

What's the difference between CWS A and B?

There's two autopilots, and you can choose the A or B autopilot in the CMD mode or the CWS mode. In CMD, the selected autopilot is following the flight director. In CWS the autopilot is following your inputs. CMD mode is the usual mode for LNAV, approaches, the usual stuff. CWS is good if you want to, say, do a nice smooth circle around Denali on your way from Anchorage to Fairbanks. Cruise at FL240, leave the jet in ALT HOLD, but put the plane in a nice 15 degree bank with CWS-R and around you go.

[Tony747-400 44]

Getting to understand CWS now,so it basically holds Pitch and Roll to the same amount of pressure you put on the control coloum. Do any other Boeing aircraft have CWS or is it built into the normal Autopilot? Haven't noticed this on the 747-400 Tony

[Big_Les 1]

So I have to fill the things in MCP and than activate the CWS? Or must I do this in FMC??

Please note this depends on:Thrust setting (N1%)weightSpeedAir pressure (height) and probably a bunch of other stuff I can't be bothered to look up..... It works something like this if you want to use it in a climb: 1. Set a pitch angle to achieve 1800 fpm climb (depends on speed, altitude etc) using the control column with cmd A VNAV selected flying straight and level (should then auto switch to CWS A)2. Hold pitch angle until stabilized3. Set climb power (92% N1 ish...)4. CWS A should now be active and hold the established pitch angle Note it will hold the pitch regardless of your actual climb rate, you need to keep an eye on speed and set power and/or alter pitch (by manual intervention on control column) in order to keep within the flight envelope. I haven't actually tried this myself but may do so tonight to see if it works as I think it should and according to the documented logic.

[Cras 6]

I havent tried it since HF3, but when I was messing about CWS, it didnt function 100% correctly. Pressing CWS A locked out my ability to change the attitude of the aircraft. The froze the aircraft in the current attitude. When getting CMD to fall back into CWS P or CWS R, this does resemble correct CWS. CWS P does take a bit of a work around, but it is supposed to automatically go back to CMD ALT HOLD when you approach the MCP altitude. In the NGX, I need to cycle the V/S button to get that to work. CWS R mode works very well when I used it to intercept the localizer. After getting clearence for approach, I turned off HDG SEL and CMD falls back to CWS R. I then press VOR/LOC and it will arm. Then I hand fly the turn and CWS works perfectly to hold the attitdue. CWS R also works great in that when I roll out of the turn to within 5 degrees, CWS R will automatically level the wings. Then after flying towards the localizer final approach course, VOR/LOC mode activates and takes over. So CWS I find to be a very useful tool, but I think it still needs to kinks ironed out in its implementation in the NGX.

[Spin737 102]

Getting to understand CWS now,so it basically holds Pitch and Roll to the same amount of pressure you put on the control coloum.Tony

It just holds the pitch and/or bank when you let go of the controls. 6 or less degrees of bank and it'll go wings level, any more and it'll hold that bank.

[kevinh 409]

Getting to understand CWS now,so it basically holds Pitch and Roll to the same amount of pressure you put on the control coloum. Do any other Boeing aircraft have CWS or is it built into the normal Autopilot? Haven't noticed this on the 747-400 Tony

CWS holds the attitude you fly it to, not the control force applied. Some 747 classics had CWS instead of AP Manual mode (with pitch and roll control knobs). It isn't available on the 747-400. Can't think of any other Boeings with CWS. Kevin Hall

[Vollie 11]

I've tried it with putting in the MCP and then using CWS, but doesn't work! Must I fly the plane manually without using A/P?

[DrumsArt 270]

I havent tried it since HF3, but when I was messing about CWS, it didnt function 100% correctly. Pressing CWS A locked out my ability to change the attitude of the aircraft. The froze the aircraft in the current attitude. When getting CMD to fall back into CWS P or CWS R, this does resemble correct CWS. CWS P does take a bit of a work around, but it is supposed to automatically go back to CMD ALT HOLD when you approach the MCP altitude. In the NGX, I need to cycle the V/S button to get that to work. CWS R mode works very well when I used it to intercept the localizer. After getting clearence for approach, I turned off HDG SEL and CMD falls back to CWS R. I then press VOR/LOC and it will arm. Then I hand fly the turn and CWS works perfectly to hold the attitdue. CWS R also works great in that when I roll out of the turn to within 5 degrees, CWS R will automatically level the wings. Then after flying towards the localizer final approach course, VOR/LOC mode activates and takes over. So CWS I find to be a very useful tool, but I think it still needs to kinks ironed out in its implementation in the NGX.

Hi Scott, Have look there : http://forum.avsim.net/topic/343621-cws-seems-dont-react-like-expected-in-this-case/page__fromsearch__1 I noticed the problem with CWS P. I submited a ticket. It seems it's partially solved since the hotfix no 2 and 3. Partially, because if the pitch override works like a charm now applying POSITIVE pitch (pull the yoke), it DON'T works applying NEGATIVE pitch (push the yoke), in this last case the altitude stays locked. Regards, Richard Portier

[Cras 6]

I am aware of that thread, and its good that CWS is getting some treatment, but there a still a few things that need some working out. As far as I understand it, the same thing is supposed to work with the HDG setting on the MCP, that CWS R is supposed to automatically go to HDG SEL mode when reaching the HDG set on the MCP, much like how it works with the VOR/LOC, which works like a charm. I believe it is also suposed to fall out of CWS P when the G/S is captured as well, although I admit I have not tried that particular thing. I am going to try on my next flght arming CWS on the ground for take off. I have tried pressing the CWS after take off, about the same time I would normally turn on CMD, but the control stick locks out. I have not tried it since HF3, but I did notice the improvements in HF2, so my next flight I will do a bunch of CWS stuff to see how it is currently behaving.

[RYR738 9]

Example ! You are flying in autopilot with HEADING SELECT as the roll mode and ALT HOLD as the pitchmode.SPEED is the autothrottle mode.** The Autopilot is controlling pitch and roll ** With CWS, YOU the pilot are controlling pitch and roll. The FD is still giving you guidance with the pitch and roll bars.

[Cras 6]

Here then is a question, in the NGX, when CWS P or CWS R is on, the corresponding FD indicator goes away, is this normal? I assume that when CWS is on instead of CMD, as opposed to CMD on and it falling back into CWS mode, the FD is still displayed? The Manuals also suggest that when the CWS A or B button is pressed, both CWS P and CWS R are to be displayed onthe PFD as well, yet this was not the case last time I tried.

[RYR738 9]

Here then is a question, in the NGX, when CWS P or CWS R is on, the corresponding FD indicator goes away, is this normal? I assume that when CWS is on instead of CMD, as opposed to CMD on and it falling back into CWS mode, the FD is still displayed? The Manuals also suggest that when the CWS A or B button is pressed, both CWS P and CWS R are to be displayed onthe PFD as well, yet this was not the case last time I tried.

That is correct !! So for example if you do not see CWS R it just means you don't have a roll mode selected ( Heading Select )

[Cras 6]

Excellent, thanks for the info!

[RYR738 9]

Excellent, thanks for the info!

You are very welcome !! Enjoy the NGX. Fred.