737NUT

Manual N1 limit setting

6 posts in this topic

Ok I admit i've hit a block wall here and need your help.  Using the classic round gauge style engine instruments, on the N1 gauge you have the N1 bug ref.  Push the little knob in and it displays the FMC desired N1 setting and the digital display blanks out.  Pull knob out and you manually set desired N1 and digital display shows the setting as well.  I tried this, set #1 to 77% and left #2 in auto.  Selected an N1 Lvl Change  on MCP, #1 eng went to 77% N1 and #2 went to 88%.  Ok, so it worked, or so I thought.   Since I have the real gauge I wanted to interface this feature.  I have the schematics for the gauge and 2 different POH's for the 737. I searched and searched and found nothing that said when in manual N1bug limit setting what happens.  In fact it says Autothrottle not affected in the real manuals.  If thats the case then why in the ixeg 733 did it the #1 engine not go past my setting?  See there is NO output in the real gauge to tell anything in the plane what you have the N1 bug set to in manual mode.  I reached out to some real 737 pilot friends, they tested in a real sim, said its for reference only.  So what gives here, is the ixeg 733 wrong?  Manuals wrong?  Other pilots wrong?    If my explanation isn't clear let me know and i'll try again.  If the ixeg is correct then could someone please show me where the signal comes from or where it goes or what computer controls that system as it is not in any of my documentation.

Thanks,

Rob

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If I recall correct, the pilots are right.... Jan can probably tell us.

Older topic on similar subject

 

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48 minutes ago, Morten said:

If I recall correct, the pilots are right.... Jan can probably tell us.

Older topic on similar subject

 

If you are correct then that means the ixeg has it wrong on the N1 bug manual setting logic.   No big deal either way but clarification would be great.

 

Rob

Edited by 737NUT
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Maybe it gets confused if you pull just one knob and use A/T? From what I understand pulling the knob disconnects the FMC and you should use manual thrust and not A/T.  So basically just a visual guideline for manual thrust, and you should probably pull both to avoid asymetric thrust.

But better wait for Jan the expert..:)

Edited by Morten
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I am fairly certain that with the manual N1 setting knobs pulled out, the pilot has to set N1 manually with the thrust levers - the autothrottle can only set thrust as commanded by the FMC.

If the autothrottle controls N1 to the manual set values in our simulation then this may be a bug. The manual (the real one) isn´t very clear on this and I have never used the manual bugs in real life...

So either both knobs in or both knobs out.

Cheers, Jan

 

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