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 10 Autopilot/CWS? (Read 9302 times)
lagraf05
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Autopilot/CWS?
Jul 13th, 2012 at 10:43am
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My one gripe with this aircraft is my inability to accurately control it's pitch. To engage the A/P one flicks both the Roll/Pitch bars into the engage position. This is fine.

However, I do not understand the CWS system. It continually fights me and always wishes to return to the previous held pitch. Only by disengaging the pitch hold mode do I get control again, but this bypasses the point of CWS in the first place.

Can somebody explain to me how the CWS and pitch select on the autopilot works? Yes, I have read the manual. But for somebody used to NG's and J41's the steam gauges of the 737 are a world away (in fact I've grown very quickly used to it, just not the pitch commands).

Thanks

Raff
  
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bud7h7
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Re: Autopilot/CWS?
Reply #1 - Jul 13th, 2012 at 2:28pm
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I have the same problem. It usually takes about 5-10 times moving the yoke before it will decide not to fight against me.
Obviously this is without Alt Hold engaged.
  

Bud Estrada i5 2500k @ 4.4 - p67 extreme4 - GTX580 - 16gb RAM - Windows 7/64 - FSX SP2
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CoolP
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Re: Autopilot/CWS?
Reply #2 - Jul 13th, 2012 at 3:16pm
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I guess I can only describe how it works here. I turn it on, it holds the pitch, I pull on the joystick some more, aiming for e.g. 5 degree up and let go again. I can hear the AP trimming to hold the pitch I've established with pulling on the stick. This takes a second or so, one can see the trim wheel spinning.

That's for increasing the pitch, but the decrease works the same way. Force it to a new pitch attitude, let go and see the AP trying to establish the commanded attitude with trimming the plane. When it's done, you will grab the stick and feel that the out of trim forces are gone. You are 'in trim' on the new attitude.

Perhaps the vital part is the pull to new attitude and then let go. But I'm on a FF stick, so I don't have a spring or something forcing my stick to centre no matter what, I just work with or against the real trim of the plane. Don't know if that adds to the problem or not.  Huh Works fine here. Bit of a poor man's FBW.  Grin

lagraf05 wrote on Jul 13th, 2012 at 10:43am:
Can somebody explain to me how the CWS and pitch select on the autopilot works?

Just in case, that pitch select knob is just for the FD. The AP doesn't mind, it just 'looks' at the yokes.
  
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lagraf05
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Re: Autopilot/CWS?
Reply #3 - Jul 13th, 2012 at 3:36pm
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I've managed to figure it out Smiley I give it a small twiddle either up or down, this seems to release the hold the AP has over the elevators, then it allows me full control over the pitch. Works like a charm.
  
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CoolP
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Re: Autopilot/CWS?
Reply #4 - Jul 13th, 2012 at 4:33pm
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Sounds good. Lets call it the twiddle mode.  Cheesy
  
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bud7h7
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Re: Autopilot/CWS?
Reply #5 - Jul 13th, 2012 at 9:18pm
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Southwest Flight 209 crash report summary:

It has been determined that pilot error was the cause of the crash that killed all 126.3 onboard.

Pilot did not twiddle flight control, resulting in the AP CWS maintaining pitch until the aircraft stalled 1.5 minutes after taking off. Only a brief communication between the pilots was recorded:

10:32:01 pm --  Pilot: Bloody hell, this piece of ....

10:32:05 pm -- Copilot: Twiddle, twiddle!

10:32:07 pm -- Pilot: What?

10:32:09 pm -- Copilot: Twiddle. You might need to twiddle. (stall warning horn in background)

. . . . . . .

10:32:18 pm -- Pilot: What?

10:32:19 pm -- <radio static>

  

Bud Estrada i5 2500k @ 4.4 - p67 extreme4 - GTX580 - 16gb RAM - Windows 7/64 - FSX SP2
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Markoz
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Re: Autopilot/CWS?
Reply #6 - Jul 14th, 2012 at 3:24am
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bud7h7 wrote on Jul 13th, 2012 at 9:18pm:
Southwest Flight 209 crash report summary:

It has been determined that pilot error was the cause of the crash that killed all 126 on board.

Pilot did not twiddle flight control, resulting in the AP CWS maintaining pitch until the aircraft stalled 1.5 minutes after taking off. Only a brief communication between the pilots was recorded:

10:32:01 pm --  Pilot: Bloody hell, this piece of ....

10:32:05 pm -- Copilot: Twiddle, twiddle!

10:32:07 pm -- Pilot: What?

10:32:09 pm -- Copilot: Twiddle. You might need to twiddle. (stall warning horn in background)

. . . . . . .

10:32:18 pm -- Pilot: What?

10:32:19 pm -- <radio static>


Outstanding! Cracked me up completely. LMAO! Grin Grin Grin
  

Mark Fletcher



PC: i7 10700K @3.8/5.1GHz | 64GB DDR4 3200 | 12GB RTX 4070 Super | 32" LCD Monitor | 1TB SSD & 2x2TB SSD | Win 11 Pro - FSX/FSX-SE/P3D3/P3D4/P3D5/P3D6/MSFS2020
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CoolP
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Re: Autopilot/CWS?
Reply #7 - Jul 14th, 2012 at 8:17am
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Grin Told you this guy would be dangerous.

http://www.desipio.com/?p=1746

And I guess those guys just showed how to deal with some situations.
  
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lagraf05
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Re: Autopilot/CWS?
Reply #8 - Jul 14th, 2012 at 9:49am
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From here on in, the CWS shall be renamed the "twiddle steering method."

I feel I may have inadvertently given rise to a new aviation meme. Thanks for the jokes and help everyone Smiley
  
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CoolP
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Re: Autopilot/CWS?
Reply #9 - Jul 14th, 2012 at 11:42am
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Well, as you saw in Bud's post, the technique already is part of any 737 emergency checklist.
Quote:

Loss of control checklist


1) hydraulic pressure > check if present
2) stab trim setting > adjust to typical cruise value
3) twiddle > no matter what
4) re-twiddle if necessary
5) keep on twiddling

That's from an official Boeing doc, trust me.  Cool

They've revised that checklist quite often. The first one just read
Quote:
Slowly apply pressure to .. your FO to handle the situation, dammit!
 Shocked
  
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Markoz
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Re: Autopilot/CWS?
Reply #10 - Jul 14th, 2012 at 4:37pm
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CoolP wrote on Jul 14th, 2012 at 11:42am:
Well, as you saw in Bud's post, the technique already is part of any 737 emergency checklist.
Quote:

Loss of control checklist


1) hydraulic pressure > check if present
2) stab trim setting > adjust to typical cruise value
3) twiddle > no matter what
4) re-twiddle if necessary
5) keep on twiddling

That's from an official Boeing doc, trust me.  Cool

They've revised that checklist quite often. The first one just read
Quote:
Slowly apply pressure to .. your FO to handle the situation, dammit!
 Shocked

STOP! I'm splitting my sides in laughter and it hurts! Enough! Angry


WAIT! No, DON'T STOP. The pain in my sides is not as bad as my usual pain! Joke away! Grin Grin Grin
  

Mark Fletcher



PC: i7 10700K @3.8/5.1GHz | 64GB DDR4 3200 | 12GB RTX 4070 Super | 32" LCD Monitor | 1TB SSD & 2x2TB SSD | Win 11 Pro - FSX/FSX-SE/P3D3/P3D4/P3D5/P3D6/MSFS2020
15.6" Gaming Laptop: i7 7700HQ | 32GB DDR4 | 6GB GTX 1060 | 256GB SSD & 1TB HDD | Win 10 Pro 64bit - FSX-SE/P3D4
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