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Tony747-400

Questions on CWS Autopilot Mode

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Hi Guys. Could someone please explain to me what the CWS Autopilot is, what it is used for, and what phase of flight should I be using it at? I have read FCOM V2 4.10.17/18 but the description seems very brief, also I am a bit confused with the displays on the FMA of CWS-P & CWS-R.I get the indication sometimes when the APP button is pressed and I have no active Roll Mode shown on the FMA. Also to my knowledge this feature is only fitted on the B737 and no other Boeing aircraft,could someone also explain why that is, I know its alot of question guys,but any help would be appreciated. Thanks Tony


Tony Simpson

 

FLYING FROM EGKK, The worlds busiest single runway Airport.

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From PMDG 737NG - AOM "What is Control Wheel Steering?:CWS can be used to control pitch and or roll of the aircraft. CWS provides full control authority to the pilot and pitch and roll can be changed by applying pressure to the yoke. When pressure is released, the autopilot will maintain the pitch and roll attitude established by the control inputs. CWS Mode can be entered in three ways:1) Pressing a CWS autopilot engage button on the MCP.2) Application of sustained pressure on the controls while the autopilot is engaged in CMD mode.3) Engage the autopilot with no previously selected pitch/roll modes. When the AFDS enters CWS mode, CWS P and/or CWS R will be displayed on the FMC and the current pitch and roll attitude will be maintained until changed by control pressures, or selecting an alternate pitch/roll mode on the MCP" Also see this:http://forum.avsim.net/topic/118507-cws-mode-for-hand-flying-the-737/


"Military Intelligence is a contradiction in terms"

Paul Yates

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To activate the roll mode, you must press the cmd B button after estabilishing on the ILS, then the both cmd buttons illimunate.And both freq must filled in. Also both runway course must be set (captain and FO). And at least both FD must be on.I dont know how the CWS works, never tried...but good to learn it. I will follow this topic to learn.


Volkan

 

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Hi. So does CWS-P CWS-R mean Pitch and Roll Modes? I have seen the display when I toggle the APP Button between ILS And FMS mode. The normal Autopilot/FMS starts to fly the Approach,but If I press the App Button again to switch to ILS mode when no ILS signal is being received its then I that I get the CWS-P/R display. Tony


Tony Simpson

 

FLYING FROM EGKK, The worlds busiest single runway Airport.

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To activate the roll mode, you must press the cmd B button after estabilishing on the ILS, then the both cmd buttons illimunate.And both freq must filled in. Also both runway course must be set (captain and FO). And at least both FD must be on. I dont know how the CWS works, never tried...but good to learn it. I will follow this topic to learn.
I think you are getting confused with autolanding rollout. CWS-R is a mode where the A/P will hold the roll that the pilot selects. CWS-P mode will hold the selected pitch.

Paul Smith.

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CWS is basically the same as Airbus' Fly By Wire. Its an autopilot mode that lets you controlt he pitch and roll using your yoke


Johan Pettersen

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I dont know if this is something that done in actual world but I use the cws for take off... I arm it and take off and always have a perfect departure... Carlitos Colon

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If you engage an autopilot for the first time with NO pitch and roll modes,CWS P and CWS R are the default pitch and roll modes.


Frederic Steiner.

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I think you are getting confused with autolanding rollout. CWS-R is a mode where the A/P will hold the roll that the pilot selects. CWS-P mode will hold the selected pitch.
yeah i'm realy getting confused....I don't understand this CWS Hmmmph.gifIs anyone in state to make a youtube video for example to explain, that makes it easier!

Volkan

 

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To try and explain it myself, if you have CWS mode engaged and you point the plane at e.g. 5 degrees pitch up, 20 degrees right roll, the plane will stay like that indefinitely. The autopilot will effectively trim the plane on both the pitch and the roll axis to hold that particular attitude and it will keep doing that every time you change the attitude by moving the control column. My own question is, operationally when is this mode used?

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To try and explain it myself, if you have CWS mode engaged and you point the plane at e.g. 5 degrees pitch up, 20 degrees right roll, the plane will stay like that indefinitely. The autopilot will effectively trim the plane on both the pitch and the roll axis to hold that particular attitude and it will keep doing that every time you change the attitude by moving the control column. My own question is, operationally when is this mode used?
From what I've read, CWS mode is used by some pilots while climbing or descending to set pitch attitude. Apparently, the climb established from this approach is smoother as the aircraft does not change attitude much, when using vnav or fpm the attitude may change more due to atmospheric conditions.

"Military Intelligence is a contradiction in terms"

Paul Yates

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I would imagine its also used if a TCAS situation warranted such action and the PIC having to overide the AP


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Chris Ibbotson

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From what I've read, CWS mode is used by some pilots while climbing or descending to set pitch attitude. Apparently, the climb established from this approach is smoother as the aircraft does not change attitude much, when using vnav or fpm the attitude may change more due to atmospheric conditions.
So I have to fill the things in MCP and than activate the CWS? Or must I do this in FMC??

Volkan

 

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So I have to fill the things in MCP and than activate the CWS? Or must I do this in FMC??
No. These modes are not about getting you to a certain point in space, they are about maintaining the planes attitude. If the A/P is on in LNAV mode, the A/P will make the adjustments necessary to try to fly to the next waypoint. If it is in heading mode, the A/P will make the adjustments necessary to try and fly on that heading. If it is in CWS-R mode, the A/P will attempt to fly at the roll the pilot selects. The clever bit, and the reason it is used, is if the A/P is in VNAV or HDG mode, and the pilot wants to go left for a while, the pilot moves the stick left, after a certain amount of effort (to prevent accidental activation) then the A/P will switch to CWS-R mode and the pilot can release the controls. The plane will maintain the left roll until the pilot decides to do something else. There was a fatal accident once when a pilot let their child move the stick and did not notice that the roll control mode had changed until it was too late to correct.

Paul Smith.

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