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Maintaining altitude


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5 replies to this topic

#1 captdini

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Posted 04 September 2013 - 10:51 PM

Hi Team,

First off, let me congratulate you on a magnificent airplane. PMDG just gets better and better with every release. I am really enjoying the 777 but unfortunately have been able to spend only about 15 minutes so far. One thing I did notice was the AP losing 100 feet when it starts a bank, then recovers to maintain altitude in the turn. While rolling out, it climbs to 100 feet above the MCP altitude and then slowly recovers back to maintain the required Altitude. The second thing I noticed was when rolling out on a heading there is a mild overshoot and a slight rocking back and forth a few times before settling down to maintain the MCP heading. These were in no wind conditions at a low altitude of 3000 feet and flaps at 15.

Are these 'real life quirks' of the 777 or does the AP need a bit of tuning up for a future fix?

Regards,

Dinshaw Parakh

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#2 captdini

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Posted 05 September 2013 - 01:31 AM

Forgot to mention I am using the Saitek yoke calibrated in FSUIPC. In the NGX, I dont get this issue

 

Dinshaw Parakh



#3 scandinavian13

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Posted 05 September 2013 - 06:40 AM


One thing I did notice was the AP losing 100 feet when it starts a bank, then recovers to maintain altitude in the turn. While rolling out, it climbs to 100 feet above the MCP altitude and then slowly recovers back to maintain the required Altitude.

 

You do realize that when you roll into a turn you're losing a lot of your vertical component of lift as it translates into both horizontal and vertical, right?  This is NOT the NGX.  It's several times larger and heavier, and those wings have to work harder because of it.  Heck, you even have to add back pressure in a Cessna...

 


The second thing I noticed was when rolling out on a heading there is a mild overshoot and a slight rocking back and forth a few times before settling down to maintain the MCP heading. These were in no wind conditions at a low altitude of 3000 feet and flaps at 15.

 

Having flaps down makes it a bit more difficult to turn, but it shouldn't be causing too much of a noticeable issue.  How big of an overshoot is considered "mild?"  What was your speed?



#4 captdini

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Posted 05 September 2013 - 07:22 AM

You do realize that when you roll into a turn you're losing a lot of your vertical component of lift as it translates into both horizontal and vertical, right?  This is NOT the NGX.  It's several times larger and heavier, and those wings have to work harder because of it.  Heck, you even have to add back pressure in a Cessna...

 

 

 

 

Having flaps down makes it a bit more difficult to turn, but it shouldn't be causing too much of a noticeable issue.  How big of an overshoot is considered "mild?"  What was your speed?

 

Hi Kyle,

 

First off, thanks for the reply. I am sorry, but maybe my statement was a bit misleading and ambiguous to you. I alluded to the AP as in Auto Pilot. Maybe you mistook it as a typo for AC? :lol:

 

The height loss, gain, etc that I noticed was with the Auto Pilot engaged. I was not hand flying. Heck, I would not be writing this if I were hand flying and expect the aircraft to maintain altitude without any back pressure! 

 

Regarding the heading overshoot, my guess would be 3-5 degrees. Like I said I was in Flap 15 configuration and the speed was at F15 maneuvering speed. AFDS was in HDG SEL and the bank angle selector was not in Auto, I moved it to 25 degrees. I will try and replicate it later tonight. For whatever its worth, my weight was just below MLW at 221 Tons. 

 

Like I mentioned all the maneuvering was with the AP engaged and not while hand flying :)

 

Regards,.

 

Dinshaw Parakh



#5 scandinavian13

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Posted 05 September 2013 - 07:33 AM


I alluded to the AP as in Auto Pilot. Maybe you mistook it as a typo for AC?

 

Nah, I assumed because you mentioned calibrating your stuff through FSUIPC.  This shouldn't matter when you're on AP (though I'm sure it's interfered before on some system out there).

 

Not sure about the rest.  I can't say if that's normal or not.  I'm not really seeing it here, though.



#6 olli4740

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Posted 05 September 2013 - 07:39 AM

Maybe frame rates were an issue? Low fps and FBW/autotrim don't combine well.





   
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