Faro From Egypt, joined Aug 2007, 1443 posts, RR: 0 Posted (5 years 9 months 6 days 16 hours ago) and read 12698 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.
SlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 71 Reply 1, posted (5 years 9 months 6 days 15 hours ago) and read 12699 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.
Faro From Egypt, joined Aug 2007, 1443 posts, RR: 0 Reply 2, posted (5 years 9 months 6 days 15 hours ago) and read 12696 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.
Jetlagged From United Kingdom, joined Jan 2005, 2452 posts, RR: 17 Reply 3, posted (5 years 9 months 6 days 14 hours ago) and read 12676 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.
SlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 71 Reply 5, posted (5 years 9 months 6 days 9 hours ago) and read 12613 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.
113312 From United States of America, joined Apr 2005, 537 posts, RR: 1 Reply 8, posted (5 years 9 months 6 days 7 hours ago) and read 12567 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.
411A From United States of America, joined Nov 2001, 1826 posts, RR: 9 Reply 9, posted (5 years 9 months 6 days 6 hours ago) and read 12562 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.
Speedracer1407 From United States of America, joined Dec 2004, 333 posts, RR: 0 Reply 10, posted (5 years 9 months 6 days 6 hours ago) and read 12553 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.
Jetlagged From United Kingdom, joined Jan 2005, 2452 posts, RR: 17 Reply 11, posted (5 years 9 months 6 days 3 hours ago) and read 12514 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.
MD11Engineer From Germany, joined Oct 2003, 13334 posts, RR: 64 Reply 12, posted (5 years 9 months 5 days 15 hours ago) and read 12438 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...
9VSIO From United Kingdom, joined Dec 2006, 642 posts, RR: 2 Reply 13, posted (5 years 9 months 5 days 13 hours ago) and read 12404 times:
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...
ThePinnacleKid From United States of America, joined Feb 2005, 672 posts, RR: 9 Reply 17, posted (5 years 9 months 4 days 6 hours ago) and read 12219 times:
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.
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.
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