737-800 CWS... Anybody using it?

[sagrada737]

Question using the CWS (control wheel steering) function with the 737-800 flight model (Sim-Avionics or other)...

If I understand the utility of the CWS function correctly, it is used to allow manual override (forced pitch and roll) via manual control inputs by the Pilot using the aircraft Yoke system. 

In my Sim (Sim-Avionics flight model), when cruising at altitude in A/P mode on the MCP (CMD selected), when I press CWS (CA side), the CMD indicator goes OFF (seemingly disconnecting the A/P?) and the CWS indicator comes ON.  At that point, I have the ability to manually maneuver the aircraft in pitch and roll. 

In this mode, the AutoPilot does NOT seem to turn OFF - rather dis-engaged, and there are no alarms that sound.  When I desire to go back to flying on the AutoPilot, I then sequentially 1. re-engage CMD and 2. re-engage LVL CHG.  It also seems that changing to CWS in VNAV mode will cancel VNAV, so it has to be re-engaged.  In addition, CWS does NOT seem to affect the A/T function.

Is that your understanding of how CWS works, or how this function should behave?  Also, what is the practical use of CWS in the various phases of flight in the 737-800, eg. Cruise, Approach, etc. ?

Anyone care to offer feedback on the above?  Thanks.

Mike

[KyleH]

Hi Mike


Look at page 38 of this document for a brief description of CWS:

http://www.smartcockpit.com/aircraft-ressources/B737NG-Automatic_Flight.html

Basically CWS keeps the A/P engaged and you direct the lateral and vertical path of the airplane using the yoke rather than the knobs on the MCP panel. When you release the yoke, the A/P holds the existing attitude and roll or heading depending on the amount of bank.

Kind of sounds like the way the Airbus side stick works when flying manually.

[sagrada737]

Hi Kyle,

Thanks for the info...   I will test some of these functions later today.  Do you find yourself using the CWS function, and if so, in what manner?  I'm always looking to improve my understanding of the 737 flight deck.

The SmartCockpit site is very interesting.  Thanks for the link.

Also, let me know when the new PCB is ready.  Thanks again.

Best Regards,
Mike

[ETomlin]

Hi Mike, that is the same way that it works for the LJ45 so as far as I can see your description is pretty well on to what the concept of CWS allows the crew to do- maneuver via control wheel vs. button pushing and encoder spinning.

[KyleH]

I don't use the CWS mode as the LevelD doesn't simulate it. Early 767's had CWS, but I don't think many later ones had it installed.

I did play around with it a bit on the PMDG 737, but that was a while ago.
I just use the MCP for autopilot functions, and hand fly when I hand fly.

[sagrada737]

Hello Kyle, Eric,

Thanks again for the feedback on CWS.  I have had a chance to further test this mode, and it does indeed maintain the last control input.  That is...   

When you engage CWS, the aircraft will allow manual control inputs via the Yoke for both pitch and roll.  When you stop control input, eg. stabilized turn and climb/descent, the AutoPilot regains control and keeps the aircraft in that flight configuration.  Modifications to Yoke inputs will cause the aircraft to respond accordingly.  When CMD is re-engaged the aircraft will once again follow the MCP settings.

This follows what was stated in the PDF document Automatic Flight you mentioned.  Thanks again for the feedback.  Now...  I just have to figure out ways that using CWS might make life easier in the flight deck for various aspects of a flight.

Mike