Control Wheel Steering
Control Wheel Steering
Joined: Aug 1998
Aviation Qualifications: ATPL
Posts: 6,623
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From: Ex-pat Aussie in the UK
Have a look at the <a href="http://www.pprune.org/cgibin/ultimatebb.cgi?ubb=get_topic&f=3&t=002385&p=" target="_blank">Control Wheel Steering</a> thread from August last year.
Joined: Jun 2001
Posts: 452
Likes: 0
From: In da north country
CWS kinda makes a joke of hand flying the airplane. The plane supposedly stays in the last position you, the pilot puts it in. It stabilizes the plane while, where as, if it were not on, like me, i would be flying all over the place. Think of it as a stabized raw data hand flying plane.. .Any more questions, ask someone who really knows whats going on!
caio for now!
caio for now!
Joined: Feb 1998
Aviation Qualifications: ATPL
Posts: 1,595
Likes: 0
From: Formerly of Nam
I only use CWS in severe turbulance. Works quite well in assisting to maintain a desired attitude (up to a point of course). Cant understand why the kids insist on using it for hand-flying in perfect conditions.
I speak about Boeings. Airbus aircraft are weird and probabley have CWS as the norm.
I speak about Boeings. Airbus aircraft are weird and probabley have CWS as the norm.
Joined: Mar 2000
Posts: 8,571
Likes: 3
From: Arizona USA
CWS is approved for use in the Lockheed TriStar from brakes release at takeoff to the end of the landing roll (FAA operators, UKCAA slightly different) and indeed quite useful after takeoff if low level turns close in are required by the SID, especially in suspected wind sheer.
Joined: Sep 2001
Posts: 79
Likes: 0
From: uk
One of the things I miss about flying a Fokker 50 (!) is that with CWS you didn't have to disconnect the autopilot when you got a TCAS RA.
Also if the flight director was 'lazy' you could give it a tweak while remaining on automatics.
Good piece of kit I recon.
Also if the flight director was 'lazy' you could give it a tweak while remaining on automatics.
Good piece of kit I recon.
Joined: Feb 2002
Posts: 554
Likes: 0
From: The Sandpit
Technically CWS is an autopilot sub mode (I am talking here about Boeing/late airbus here as I can't talk about other types). It is in essence attitude hold but where the pilot can make inputs into the autopilot via the yoke. A kind of fly by wire even for a/c which have a mechanical i/p to the control surfaces.
Sensors in the yoke (called force transducers) pick up any input force that the pilot may feed into the control column and transmit the resulting electrical signal to the relevant surface actuator to deflect it to produce the desired input. When the yoke is released the autopilot maintains the attitude at which the column was released. . .It is not TCS where the pressing of a button momentarily disengages the control surface servos and them re-engages them when the button is released.
On Boeings it is selected by either a mid detent on the a/p engage paddle or a middle button on the AFCS MCP.
Of course on Airbus it is in use all the time the pilot is 'manualy' flying as it is a FBW a/c.
As for when it is used? Don't ask me, I am only an engineer!
Sensors in the yoke (called force transducers) pick up any input force that the pilot may feed into the control column and transmit the resulting electrical signal to the relevant surface actuator to deflect it to produce the desired input. When the yoke is released the autopilot maintains the attitude at which the column was released. . .It is not TCS where the pressing of a button momentarily disengages the control surface servos and them re-engages them when the button is released.
On Boeings it is selected by either a mid detent on the a/p engage paddle or a middle button on the AFCS MCP.
Of course on Airbus it is in use all the time the pilot is 'manualy' flying as it is a FBW a/c.
As for when it is used? Don't ask me, I am only an engineer!
Joined: Jul 2000
Posts: 179
Likes: 0
From: Denver, Co. usa
I used it in 737's when descending and trying to get a some what constant feet per minute. This was in Alaska where we often descended from FL350 without any level off because we were the only traffic.
On the L1011 I never used it because their we could select the feet per minute for the descent.
I was also told in Alaska that there are those who have and those who will, land the aircraft in CWS. Not that I did it of course.........
On the L1011 I never used it because their we could select the feet per minute for the descent.
I was also told in Alaska that there are those who have and those who will, land the aircraft in CWS. Not that I did it of course.........
Joined: Jul 2000
Posts: 179
Likes: 0
From: Denver, Co. usa
I used it in 737's when descending and trying to get a some what constant feet per minute. This was in Alaska where we often descended from FL350 without any level off because we were the only traffic.
On the L1011 I never used it because their we could select the feet per minute for the descent.
I was also told in Alaska that there are those who have and those who will, land the aircraft in CWS. Not that I did it of course.........
On the L1011 I never used it because their we could select the feet per minute for the descent.
I was also told in Alaska that there are those who have and those who will, land the aircraft in CWS. Not that I did it of course.........
Joined: Apr 2001
Posts: 182
Likes: 0
From: a fence in the sun
Now, careful with CWS chaps...
On the F50 it's a means of re-datuming the FD, and provided that you have armed the altitude capture mode, you will still level off where you should.
In the Boeing, it takes away some workload, and thus reduces arousal. So, you're climbing or descending to cleared level, in CWS. As you approach the cleared level, you'll get all the usual indications (800ft to level chime/'c' chord) and light, but the aircraft will sail through the level unless you do something. There's a danger that you won't do anything because of the relatively low arousal. You'll know about this when you get the altitude alert passing 200/300ft the wrong side of the level. By then, of course, it's too late.
So, I don't use CWS other than in significant turbulence or if hand-flying and I need to put a chart away quickly or whatever. In the latter circumstances, I never leave it in longer than a few seconds. It's also handy when you've been hand-flying with raw data, and you're about to put the automatics back in, because engaging CWS legitimises use of the MCP without having to call for everything.
On the F50 it's a means of re-datuming the FD, and provided that you have armed the altitude capture mode, you will still level off where you should.
In the Boeing, it takes away some workload, and thus reduces arousal. So, you're climbing or descending to cleared level, in CWS. As you approach the cleared level, you'll get all the usual indications (800ft to level chime/'c' chord) and light, but the aircraft will sail through the level unless you do something. There's a danger that you won't do anything because of the relatively low arousal. You'll know about this when you get the altitude alert passing 200/300ft the wrong side of the level. By then, of course, it's too late.
So, I don't use CWS other than in significant turbulence or if hand-flying and I need to put a chart away quickly or whatever. In the latter circumstances, I never leave it in longer than a few seconds. It's also handy when you've been hand-flying with raw data, and you're about to put the automatics back in, because engaging CWS legitimises use of the MCP without having to call for everything.
Joined: Feb 2000
Posts: 1,995
Likes: 512
From: UK
One further point re. CWS. On the L1011, it was able to capture and maintain the dialled-up Alt/FL. That being so, it became a useful tool in turbulence for holding patterns since it had a higher bank angle limit than the A/P - (from memory) 38 degs as against 25.. .It also, of course, was part responsible for the Everglades crash, coupled with the lack of Alt deviation warning.
Joined: Dec 2002
Posts: 11
Likes: 0
From: Porto Alegre (RS) Brazil
Pitch Trim in CWS Mode
Dear friends
While in CWS mode, when a pitch change is commanded by the pilot, does the autopilot will trim the horizontal stabilizer or just keep the elevator on the commanded position?
Thank you!
Best regards
Vicente
While in CWS mode, when a pitch change is commanded by the pilot, does the autopilot will trim the horizontal stabilizer or just keep the elevator on the commanded position?
Thank you!
Best regards
Vicente
Joined: May 1999
Posts: 1,846
Likes: 4
From: Bristol, England
We used to use the roll channel in CWS with the pitch channel in CMD and ALT when refuelling fighters. It gave us smooth roll control for the formation combined with a good height lock. Don't know if it is still an approved technique.
Joined: Mar 2001
Posts: 4,563
Likes: 35
From: I wouldn't know.
In the 737 Classic the aircraft will capture any MCP selectect altitude, level out and automaticly enter ALT HLD mode out of CWS. Additionally the AT will try to maintain the selected speed as much as possible so that CWS is a nice tool to limit your pitch if you plan to release the girls early (ever tried to push a trolly through the cabin at 12° pitch up?). Apart from that i normally don't use it, flying raw data in my company means you're flying completely manual except for AT which is supposed to be in ARM.
Joined: Dec 2004
Posts: 733
Likes: 2
From: Andalucia
Post #15 "Pitch Trim in CWS"
As far as I am concerned Pitch trim is part of basic Autopilot function in All modes.
The Autopilot always trims the Stabilizer to null the standing elevator deflection.
Not being one of the Chosen few L1011 experts, that may be a bit different due to the lack of elevators.
As far as I am concerned Pitch trim is part of basic Autopilot function in All modes.
The Autopilot always trims the Stabilizer to null the standing elevator deflection.
Not being one of the Chosen few L1011 experts, that may be a bit different due to the lack of elevators.
Joined: Jan 2006
Posts: 454
Likes: 3
From: Georgia, USA
Post #15 "Pitch Trim in CWS"
As far as I am concerned Pitch trim is part of basic Autopilot function in All modes.
The Autopilot always trims the Stabilizer to null the standing elevator deflection.
Not being one of the Chosen few L1011 experts, that may be a bit different due to the lack of elevators.
As far as I am concerned Pitch trim is part of basic Autopilot function in All modes.
The Autopilot always trims the Stabilizer to null the standing elevator deflection.
Not being one of the Chosen few L1011 experts, that may be a bit different due to the lack of elevators.