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Cpt_Piett

PMDG 737 altitude restrictions

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Has anyone else noticed that the plane does not respect the FMC flight plan altitude restrictions when descending in VNAV mode? 

 


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“Intensify the forward batteries. I don’t want anything to get through”

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Yes, and I've also found it to be VERY lazy about airspeed restrictions in some cases.


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Yes, I have noticed this as well. Really waiting on that updated LNAV and VNAV logic.


Dan Scott

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33 minutes ago, Cpt_Piett said:

Has anyone else noticed that the plane does not respect the FMC flight plan altitude restrictions when descending in VNAV mode? 

 

Yup, it either misses them too high or decides it needs to get down to the next restriction miles and miles away resulting in a staircase descent.

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It seems very buggy at the moment. Doing some testing between VHHH and VMMC. Descending on the STAR it didn't meet the restrictions. There was a restriction at 11,000ft and I had set the target altitude for 3000ft. It completely disregarded the 11,000ft restriction.

I did a touch and go at Macau then tried to reconfigure for an approach into Hong Kong Intl. As I was setting up for new destination in the RTE page, then tried to select a new STAR and APPR in the DEP/ARR page, everything just froze. FMC is completely unresponsive. I cannot change the heading (or anything else on the MCP). Also I cannot change NAV frequencies. The plane keeps flying, but...

I'd expect better than this at $69.99...

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“Intensify the forward batteries. I don’t want anything to get through”

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15 minutes ago, Cpt_Piett said:

It seems very buggy at the moment. Doing some testing between VHHH and VMMC. Descending on the STAR it didn't meet the restrictions. There was a restriction at 11,000ft and I had set the target altitude for 3000ft. It completely disregarded the 11,000ft restriction.

I did a touch and go at Macau then tried to reconfigure for an approach into Hong Kong Intl. As I was setting up for new destination in the RTE page, then tried to select a new STAR and APPR in the DEP/ARR page, everything just froze. FMC is completely unresponsive. I cannot change the heading (or anything else on the MCP). Also I cannot change NAV frequencies. The plane keeps flying, but...

I'd expect better than this at $69.99...

Make sure it's not paused at top of descent 

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I haven't observed this problem so far. So long as one is in VNAV mode, altitude restrictions should be obeyed unless one has pressed the ALT INTV button on descent. Also what are the FMA indications during descent?


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I was descending in VNAV and LNAV, didn’t use ALT or SPD intervene.


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“Intensify the forward batteries. I don’t want anything to get through”

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Just now, Cpt_Piett said:

I was descending in VNAV and LNAV, didn’t use ALT or SPD intervene.

Did they change the VNAV code for the MSFS version? I was under the impression it was the same code, which would be strange since I've flown the NGXu in P3D a lot and don't recall ever having seen it bust a restriction.

VNAV PATH or SPD? Was that a hard restriction or maybe a below restriction?

Edited by threegreen

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VNAV PTH IICR. I didn’t make any changes in the FMC. I’ll do more testing to see if it was an isolated incident or if it persists.

Edited by Cpt_Piett

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“Intensify the forward batteries. I don’t want anything to get through”

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2 hours ago, somiller said:

Yes, and I've also found it to be VERY lazy about airspeed restrictions in some cases.

Hard waypoint restrictions or target speed? Because in VNAV PATH there is a certain margin (10 or 15 kts, selectable in the FMC) that the aircraft will accept below or above the target speed. Also when the A/T is in arm mode you have to manually adjust thrust as needed until it goes back into FMC SPD or another speed mode.


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1 hour ago, threegreen said:

Hard waypoint restrictions or target speed? Because in VNAV PATH there is a certain margin (10 or 15 kts, selectable in the FMC) that the aircraft will accept below or above the target speed. Also when the A/T is in arm mode you have to manually adjust thrust as needed until it goes back into FMC SPD or another speed mode.

It disregarded the restriction at HAZEL and continued descending to the set altitude of 3000ft.

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“Intensify the forward batteries. I don’t want anything to get through”

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11 minutes ago, Cpt_Piett said:

It disregarded the restriction at HAZEL and continued descending to the set altitude of 3000ft.

FMC navdata base updated to the current cycle I guess?

Edited by threegreen

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Haven't seen that. It undershoots ALT sometimes by a couple of 100fts, but I've never seen it ignore restrictions. I'd say it's a GIGO error, probably old/faulty navdata. Did you double check charts vs FMC?

However since it's generally buggy for you (frozen cockpit), I'd say it's probably something else. Better open a ticket.

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