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CRJ900 PRO busting FCP Altitude


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Hello

 

Some moments ago the autopilot did not capture FCP ALT (37.000ft) and just blew past it. ALTS was armed submode.
Shouldn't PITCH mode be able to transition into ALTS ?

Had I not intervened, the aircraft would've just continued to climb.

 

Has this happened to anymore else than just me?

 

Thanks in advance

 

 

 

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In what flight mode did you climb to your flight level?
I normally climb in speed mode (CLB280), but even with vertical speed mode (VS1.4) I never had any problems with the flight level not being maintained.
I'm also wondering how you managed to display the pitch in the PFD.

 

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Wolfgang

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You have been climbing in PITCH mode which is a manuel mode where you can set the FD via the VS wheel and the AP will regulate the pitch. This mode is not suitable to make a level off at desired altitude. You need to be in SPEED or VS mode, as these are the two modes the AP has authority to switch over to ALTS.

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1 hour ago, metzgergva said:

You need to be in SPEED or VS mode, as these are the two modes the AP has authority to switch over to ALTS.

This is not correct.

Real autopilot treats ALTS as follows:

 

"Altitude preselect mode is automatically selected upon selection of any vertical mode, except glide-slope capture or overspeed" 

 

So PITCH mode should not cause an overshoot.

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3 hours ago, Hoffie3000 said:

I'm also wondering how you managed to display the pitch in the PFD.

 

It's the basic AP pitch mode. You have three ways of manipulating the aircraft in climb / descent:

  • V/S
  • IAS / MACH hold
  • PITCH hold 

 

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PITCH is the “default” vertical mode, which will be active if no other vertical mode (SPD, IAS or VS) is selected.

 

The aircraft should capture an armed altitude from PITCH mode, just as it does for the other vertical modes - but it is really not the correct or ideal vertical mode to be using in a cruise climb. SPD or VS would be more appropriate.

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