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Noel

Is it possible to turn the plane with the autopilot engaged?

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Doesn't appear to be possible and I couldn't find anything in the documentation but if you know--thanks in advance.

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I'm not sure what you mean Noel. If you mean turn on the ground with AP on, don't know why you would do that.

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Hi Noel,

 

Assuming you are flying with LNAV engaged, all you need to do is turn the HDG SEL knob to the direction (degrees) you want to turn and press it. This engages Heading Select mode while the autopilot remains engaged but LNAV mode is disengaged. To revert to LNAV you just press the LNAV button.

 

Regards

Mervyn

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With the autopilot engaged, a vertical, and horizontal mode will be engaged too. These are likely to be some kind of intelligent navigation mode (like LNAV/VNAV) or a direct control mode (like Heading Select, or Vertical Speed).

 

There may also be an approach mode selected (APP/LOC). APP can't be 'downgraded' to another mode without passing through Go Around, or having the Flight Directors turned off to clear all autopilot and guidance modes of any selection.

 

If you have the autopilot engaged, one will assume you have one of these modes selected (as the Autopilot cannot be "on" and "doing nothing")

 

If I wanted to turn the aircraft left or right while flying and the Autopilot was in LNAV following a flightplan from the FMS and F/D, I would ensure the Heading Select window was alligned roughly to the direction I was flying, then press the "Select" button that's in the middle of the heading select knob. The Flight director would command a turn toward the position of the Heading Selector. Rotating the knob left and right will select a compass bearing. The autopilot would bank to turn the aircraft to that compass bearing.

 

You press the button "in the middle" of the selector knob. This is different to the 737NGX where you press a "HDG SEL" which illuminates when active.

The 777's indication of being in HDG Select is on the PFD, and there is no light on the MCP to indicate Heading Select mode being on or off.

 

To complete the turn, the Autopilot of course, has to be on, and the aircraft has to be flying, and above the minimum Autopilot engagement altitude.

Remember, you can't select HDG mode if you are currently in APP mode (Active, not armed). You'd have to press TOGA (to initiate go around) or turn off both flight directors to disengage the mode, then reselect them so as to be able to engage the new mode.

 

Selecting Heading Select from any other mode (other than APP) will result in the autopilot immediately initiating a turn toward the selected compass heading (or continuing straight ahead if the selected heading is the same as where you are currently pointed)

 

 

  • the 737 has a "HDG SEL" button under the rotating Heading selection knob. When this is pressed the 737 will turn to that heading

 

  • The 777 has a "HOLD" button under the rotating Heading selection knob. When this is pressed the 777 will maintain it's current heading.

HDG SEL and HDG HOLD are not the same thing

 

The 777 and the 737 are not the same

 

Aerosim10.jpg

SEL button in the middle of the rotating knob. NOT "HOLD"

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As Noel is an experienced simmer...

 

I doubted he was referring to basic operation of a Boeing. :smile:

 

Must be pressing the centre of the heading knob that foxed him.

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Thanks you guys but I guess I didn't frame the question correctly.  The question should have been:  when the AP is engaged it is indeed possible in some planes, including the NGX, to leave vertical climb/hold  controlled yet disengage lateral control (heading or LNAV) so that the pilot can operate ailerons freely while retaining vertical control.  I don't see this in the T7 which is the question I'm asking about.  So yes, I do know how to operate LNAV and heading knobs to affect turning but just checking to see if I've missed a way to allow manual turning by the pilot when the AP is engaged.

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just checking to see if I've missed a way to allow manual turning by the pilot when the AP is engaged.

 

Nope.  No comparable mode exists on the 777.  Let the computer handle it all, or handle it all yourself.

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Nope.  No comparable mode exists on the 777.  Let the computer handle it all, or handle it all yourself.

Ahh, ok thanks for that Kyle.

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Ahh, ok thanks for that Kyle.

 

Welcome.  Gotta love the consistency of all of the different models, eh?  Heck, even the Diamond 40 I fly has form of CWS.

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I believe the main reason the 737NGX has the "CWS" function is that the 737-200's with Sperry 77 type autopilots "ONLY" had CWS vertical modes. Ie you could either have the autopilot MAINTAIN the CURRENT altitude, or be in CWS, or have the autopilot off. No "Vertical Speed Climb" or "FLCH" or anything.

 

And because the operators want all 737's to be exactly the same type rating from 1965 to 2013, CWS has to be there, and the other things are just "extra features thanks to computers".

 

777 didn't have any such type rating commonality issue. Started over from scratch. No CWS.

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