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Control Wheel Steering  
User currently offlineFaro From Egypt, joined Aug 2007, 1548 posts, RR: 0
Posted (7 years 1 month 6 days 9 hours ago) and read 16683 times:

Does anyone know why the Control Wheel Steering mode in autopilots is going out of fashion? I may be wrong but I believe the 737 series is the only airliner in production which still offers it.

Thanx


The chalice not my son
18 replies: All unread, jump to last
 
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 1, posted (7 years 1 month 6 days 9 hours ago) and read 16687 times:

Well, maybe because nobody ever uses it. I can only recall one occasion when the guy I was flying with used it. It was such an amazing event that we had a thirty minute conversation about it. Turns out he really only uses it because nobody else does. It is good for starting a conversation.

As a philosophical matter I'm not sure it is even a good idea to have it. It can produce an illusion that someone is flying the airplane when no such thing is true. CWS only "points" the airplane. It will cheerfully fly beyond your clearance limit, into restricted airspace, into another airplane or into a mountain. All with the pilot hands-off and thinking he's got it under control. Truth is, it does little more than trim does in a Bonanza.

Most of us prefer to actually fly the airplane unless we are in fully automated flight. CWS is like the worst of both: You don't get to fly and nobody is flying.

When in automated flight, I think most of us prefer to have both lateral and vertical modes engaged.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineFaro From Egypt, joined Aug 2007, 1548 posts, RR: 0
Reply 2, posted (7 years 1 month 6 days 9 hours ago) and read 16684 times:

lol Slam, sounds like a case of not eating the cake you didn't have in the first place...

I was intrigued because the thing was used cinematographically once way back, in Airport '75. They had the terror-stricken stewardess slowly turning big fat bank dial on the 747's CWS to make it turn to avoid hitting a big bad mountain top...

I wonder whether it had a historical utility once, maybe on the piston-driven airliners of old.



The chalice not my son
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2556 posts, RR: 24
Reply 3, posted (7 years 1 month 6 days 8 hours ago) and read 16664 times:

In many ways, a FBW Airbus in Normal Law is like a non-FBW aircraft in CWS mode, only it's a much more pleasant experience.

I recall jump-seating in a 747-200 where the F/O was being checked out. The Capt made the F/O fly a few minutes in CWS just so he got the feel of it. Then words to the effect of "that's probably the first and last time you'll ever want to do that in a 747". Having tried it in the simulator I know exactly what he meant.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineS.P.A.S. From Liechtenstein, joined Mar 2001, 967 posts, RR: 2
Reply 4, posted (7 years 1 month 6 days 3 hours ago) and read 16610 times:

How does this system work, by the way?

In my, perhaps wrong, understanding the crew makes AP inputs via the control yoke.

RS



"ad astra per aspera"
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 5, posted (7 years 1 month 6 days 3 hours ago) and read 16601 times:

Quoting S.P.A.S. (Reply 4):
crew makes AP inputs via the control yoke.

Pretty much it. It provides stability in pitch and roll. If you release the yoke with less than about 6 degrees of roll it will roll wings level and fly that way. You can arm an altitude while in CWS pitch and it will capture and hold that altitude with a change in annunciation status (it will show "alt hold")

I think it might also be possible to arm a lateral nav intercept in CWS roll mode. Been a long time since I flew it or taught it and I don't want to dig up my out-of-date manual just to make the post look more authoritative. If someone is current on a Boeing with the system they can correct me.

[Edited 2007-08-19 23:34:05]


Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineWILCO737 From Greenland, joined Jun 2004, 9041 posts, RR: 76
Reply 6, posted (7 years 1 month 6 days 2 hours ago) and read 16591 times:
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The MD11 uses continously Roll CWS during manual flying... it is kind a helpful if you get used to it once. But only in ROLL mode...

WILCO737 (MD11F)
 airplane 



It it's not Boeing, I am not going.
User currently offlineFaro From Egypt, joined Aug 2007, 1548 posts, RR: 0
Reply 7, posted (7 years 1 month 6 days 2 hours ago) and read 16584 times:

Thanx to one and all for your comments and insight.

Faro



The chalice not my son
User currently offline113312 From United States of America, joined Apr 2005, 572 posts, RR: 1
Reply 8, posted (7 years 1 month 6 days 1 hour ago) and read 16555 times:

Actually, when Karen Black dials in a heading, that is NOT CWS. That is regular autopilot command HDG mode. In CWS, the autopilot actuates the control surfaces and the control wheel/column tells the autopilot to pitch up/down and bank left, right or level the wings.

User currently offline411A From United States of America, joined Nov 2001, 1826 posts, RR: 8
Reply 9, posted (7 years 1 month 6 days ago) and read 16550 times:

Older piston airliners with Bendix or Sperry autopilots did not have CWS.

CWS in the Lockheed TriStar is quite useful for low altitude turns such as were required at the old ATH airport, for noise abatement....especially when one is having a bad hair day.

With the TriStar, CWS could be selected when on the ground, ready for action when airborne...except on those select airplanes that were on the British (or associated) register (BA, GF etc....quite likely a UKCAA requirement, just like scarfed pitot tubes and reduced Mmo, not forgetting recovery speed brakes, of course.


User currently offlineSpeedracer1407 From United States of America, joined Dec 2004, 333 posts, RR: 0
Reply 10, posted (7 years 1 month 6 days ago) and read 16541 times:

Despite the explanations above, I'm still unsure exactly what CWS is. If you're using the control wheel, how is that autopilot? What exactly is the form of automation that occurs in CWS?


Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2556 posts, RR: 24
Reply 11, posted (7 years 1 month 5 days 21 hours ago) and read 16502 times:

It's basically attitude (pitch and bank) hold. You use the control wheel to adjust the pitch and bank angle. When the control wheel is released the autopilot holds that attitude.


The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently onlineMD11Engineer From Germany, joined Oct 2003, 14027 posts, RR: 62
Reply 12, posted (7 years 1 month 5 days 8 hours ago) and read 16426 times:

Quoting WILCO737 (Reply 6):
The MD11 uses continously Roll CWS during manual flying... it is kind a helpful if you get used to it once. But only in ROLL mode...

WILCO737 (MD11F)

On the UPS MD11s it was deactivated.

Jan


User currently offline9VSIO From United Kingdom, joined Dec 2006, 717 posts, RR: 2
Reply 13, posted (7 years 1 month 5 days 7 hours ago) and read 16392 times:
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Quoting Jetlagged (Reply 11):
It's basically attitude (pitch and bank) hold. You use the control wheel to adjust the pitch and bank angle. When the control wheel is released the autopilot holds that attitude.

Sounds rather Airbus-y to me!



Me: (Lining up on final) I shall now select an aiming point. || Instructor: Well, I hope it's the runway...
User currently offlineWILCO737 From Greenland, joined Jun 2004, 9041 posts, RR: 76
Reply 14, posted (7 years 1 month 5 days 3 hours ago) and read 16361 times:
AIRLINERS.NET CREW
HEAD MODERATOR

Quoting MD11Engineer (Reply 12):
On the UPS MD11s it was deactivated.

Didnt know that, we still use it and its not bad once you get used to it...

WILCO737 (MD11F)
 airplane 



It it's not Boeing, I am not going.
User currently offlineTroubleshooter From Germany, joined Feb 2005, 423 posts, RR: 5
Reply 15, posted (7 years 1 month 4 days 14 hours ago) and read 16288 times:

Quoting Faro (Thread starter):
I may be wrong but I believe the 737 series is the only airliner in production which still offers it.

The EMB135/145 have CWS installed.



This job sucks!!! I love this job!!!
User currently offlineQslinger From India, joined Apr 2006, 261 posts, RR: 0
Reply 16, posted (7 years 1 month 4 days 2 hours ago) and read 16235 times:

Quoting Faro (Thread starter):
Control Wheel Steering

Here is a question for u guys, What is a CWS??? What does it look like? 

[Edited 2007-08-22 00:06:11]


Raj Koona
User currently offlineThePinnacleKid From United States of America, joined Feb 2005, 725 posts, RR: 8
Reply 17, posted (7 years 1 month 4 days ago) and read 16207 times:

Quoting Troubleshooter (Reply 15):
The EMB135/145 have CWS installed.

It is referred to as TCS on the ERJ's... "Touch Control Steering"

it does the following:

- Allows manual maneuvering of the airplane without disengaging the autopilot. The airplane may be maneuvered to any desired pitch attitude while the TCS button is pressed. When the button is released the following occurs:
1. Primary servos reengage.
2. The computer synchronizes itself to the new pitch attitude and vertical mode and maintain it.
3. Lateral control is returned to the previously selected lateral mode (return to the later mode is filtered to prevent rapid maneuvers).
- After glide slop capture in APR (approach) mode with the autopilot engaged, if the TCS button is pressed and released, the autopilot will resume the controls and turn the airplane to the ILS center beam.



"Sonny, did we land? or were we shot down?"
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2556 posts, RR: 24
Reply 18, posted (7 years 1 month 3 days 10 hours ago) and read 16131 times:

Quoting Qslinger (Reply 16):
Here is a question for u guys, What is a CWS??? What does it look like?

Here's what Control Wheel Steering looks like:


View Large View Medium
Click here for bigger photo!

Photo © Juan Carlos Guerra - APM



Look at the autopilot engage "paddles" on the glareshield mode control panel. AP B is in CMD (command) mode, under that is CWS position, then OFF. Moving the paddle down to CWS engages this mode. The paddle will also automatically trip to CWS under certain conditions, for example: the command mode is invalid.

Basically CWS is an alternative to AP Manual mode. The pilot uses the control wheel rather like when hand flying, pull or push the column to adjust pitch angle, turn the wheel to adjust bank angle. When the desired attitude is achieved, the pilot releases the control wheel and the AP maintains the current attutude. However when bank angle is close to zero when it controls to wings level, on the assumption that that is what is required.

AP Manual is similar except rather than using the control wheelas the input, a separate manual pitch and turn control is installed. Both AP Manual and CWS are attitude hold modes, the only difference being how the attitude is adjusted.

The picture below shows a 747-200 which has manual AP controls, though some 747-200s had CWS. The turn knob is on the centre pedestal, just aft of the throttle quadrant. There is a pitch wheel either side of the turn knob. Note the autopilot MCP engage paddles are labelled CMD/MAN/OFF in this case.


View Large View Medium
Click here for bigger photo!

Photo © Andrea Buzzacchi



Many modern autopilots do not have CWS or manual modes. The basic modes in such cases are usually vertical speed and heading.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
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