View Full Version : 737 - CWS switch.

29th Aug 2004, 01:24

Can anyone provide an idiots explanation for what the CWS button on a 737 glareshield is for? Two of them live just underneath the A/P buttons.

Also, what is the very small dial in the top right of the PFD for?

Thanks in advance from an interested amateur!

Gin Slinger
29th Aug 2004, 01:59
CWS - makes it fly like an Airbus. Is that idiotic enough? Basically, the autopilot 'remembers' the pitch/bank you set it at and flys it until told otherwise.

Not exactly sure which dial you mean. Plse provide further description.

29th Aug 2004, 14:02
Thanks for the CWS answer.

There is a small dial displayed in the top right of the PFD, just left of the top of the altitude tape. Seen flightdeck pictures in Airliners.net, and this dial is present only some of the time.
It has no scale, just a number updating as the needle swings round. Think the range is in single figures with one decimal place.

Just curious...

Gin Slinger
29th Aug 2004, 14:14
Still not sure what you mean. It's been a while since I flew the NG, plus airlines can have the displays programmed differently. If you post a link to a picture I could probably tell you what it is.

Regarding CWS, it stands for Control Wheel Steering. It's a very rarely used feature - our SOPs state it's only for use in severe turbulance.

29th Aug 2004, 14:34
I think you are referring to the Radio Altimeter. On some NGs - but not all - the RA changes from a digital to a combination digital and dial below 1,000' AGL. There is a small indicator on the dial showing the RA minimums which have been set. The display also turns amber when below minimums.


Gin Slinger
29th Aug 2004, 14:37
I think LOKE is has got it.

29th Aug 2004, 14:41
Thanks folks,

All makes sense now...

29th Aug 2004, 19:09
The dial on the PFD is most likely the Angle of Attack (AOA) indications.
Here is a short extract from AERO Boeing Oct 2000:
"The AOA indicator on the PFD shows an analogue and a digital display of the AOA. When landing flaps are selected a 3 degree wide green band is visible, it is centered at an AOA equivalent to Vref+5 (assuming nominal gross weight, mid CG, no sideslip, a stabilized 3 degree glide skope-thrust level and no system error). Normally the band accounts for expected variations."

29th Aug 2004, 23:02


You can see the small dial in this picture. Top right of the PFD, beside the top end of the altitude tape.

Seems to range from -1 to +6 or thereabouts.

30th Aug 2004, 11:03
You can see the small dial in this picture. Top right of the PFD, beside the top end of the altitude tape.
In the B737NG FCOM (AOM) Vol.2 chapter 10 it is stated:
"Analog Needle (white)
Indicates analog AOA value.
- needle travel is limited to a range of -6 degrees and +21 degrees
- fixed at 0.0 degrees when on the ground and ground speed is less than 80 knots."

The angle of attack indications display ADIRU (Air Data Inertial Reference System) aircraft body angle of attack.

31st Aug 2004, 08:12
top right PFD:
Radio altitude-Round dial:
*digital display from 2500 to 1000 ' AGL
*round dial displays below 1000' AGL
*pointer indicates selected radio altitude minimums
*the circumference of the dial is added to,or taken away from,to depict the a/c radio altitude

737NG FCOM 10.11.15

There is no AOA pointer on the PFD,except maybe the FPV,which displays flight path angle relative to horizon line and drift angle relative to display centre.
Noak,maybe all this differ from a/c to a/c depending on first buyer requests. Can you tell me the page in FCOM where you found that,and also where would be the Radio altitude indicated on your NG. (is this aoa by any chance only on the 800 series?)

31st Aug 2004, 16:26
The little "dial" at the top right is indeed an AOA indicator. It's one of the many display configuration options available with the Honeywell cockpit. AA uses it and the Rad Alt is in the bottom center of the PFD.

31st Aug 2004, 18:54
The description is in FCOM 10.11.11 and we have the AOA indicator on all our 6/7/800's.

31st Aug 2004, 20:29
thks. on our planes,on that particular position is the RAlt. We don't have the AOA indicator :(

31st Aug 2004, 23:06
I would make sense if it was an AOA indicator. As AA use them and a few of the Qantas 737-800's are Ex-AA orders.

Shaka Zulu
3rd Sep 2004, 15:59
I use CWS if i am stuck at let's say an intermediate level with cloud ahead with possible turbulence. advance thrust levers and CWS pitch to play with the rate of climb and speed just to skim over the cloud if climb clearance is given.
Works much quicker than the slow LVL Change adjustments in pitch and power

5th Sep 2004, 09:52
Shaka : are you doing that with pax on board? I find hard to believe you're flying a 737 ,in uk,actually I believe you're flying it on FS2000.No real airline pilot will do the trick you've just described.
LVL CHG slow? Try engaging it and reducing comanded speed at the same time. Gee..I'd like to have you on my plane,sitting on the last row while I'll perform the 'avoiding wx' maneuvre you've just described.

Shaka Zulu
6th Sep 2004, 11:34
Can you not make an insult like that?
I happily fly the aircraft in CWS (all 737's!), it's a quite natural maneuver, I'm just saying instead of tweaking the speed all the time, you now just play with the pitch as required to come over the top whilst keeping an eye on the speed...

What's so hard for you to believe alexban and I do appreciate it if you just stop being such a prejudice, for one I didn't ask for it!