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John Williams

Managed Descent Bug (Very Rapid Descent)

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Hello!
First off, sorry if this has already been answered. I searched the forums and found people reporting similar issues, however, I have not seen any with a solution. (It appears most of the time the OP stops responding to requests for information).

 

I am having an issued with both the A318/319 and A320/321 in P3D V4. Simply put, it appears the simulation is not calculating a proper descent path, resulting in an 8,000+ foot per minute decent being commanded by the autopilot to keep up with the descent path. I even start the descent well before the predicted top of descent, only to watch the descent path suddenly plummet off the scale with no time for me to react. It has literally been impossible to keep up with the descent path on every flight I have performed in the aircraft, even with maximum spoilers. I have a flight plan with a STAR loaded each time, usually RNAV, and have the wind data uplink successfully set. I am running the latest version of the Airbus Professional on Windows 7. 

 

I am assuming I'm doing something wrong, however, I can't figure out what it is after about 10 flights of trying different things. I uninstalled and reinstalled, as one thread suggested, however, that had no impact whatsoever. I am flying with FS2Crew if that makes any difference.


Let me know what information you need to help resolve this issue and I will certainly provide it.

 

Thanks!

John

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PONCT-JFUND2 ends up in Boston KBOS........

 

My personal opinion about this STAR must be RADAR VECTORING to actual runway in use to avoid step turns and steep descent

 

 

 

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Hello John,

What version of the Airbus you are using? When the dive happens, are you in managed descend mode? Also does your speed increase beyond the upper magenta speed limit?

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8 hours ago, AAC47 said:

PONCT-JFUND2 ends up in Boston KBOS........

 

My personal opinion about this STAR must be RADAR VECTORING to actual runway in use to avoid step turns and steep descent

1

 

You're correct, I meant KBOS. Sorry, it was late. That STAR was just an example, I've had various different STAR's of different types and the problem persists on all of them. Furthermore I just did a test with no STAR, instructing the aircraft to just cross a VOR at a certain altitude. I still ended up with a more than 8K FPM descent to follow the descent path.

 

3 hours ago, Secondator said:

Hello John,

What version of the Airbus you are using? When the dive happens, are you in managed descend mode? Also does your speed increase beyond the upper magenta speed limit?

 

1.2.3.0 and yes, in managed descent mode. I select the altitude I want to descent to and left click the altitude knob once, resulting in the circle appearing next to it and "DES" appearing on the screen. (Sorry for the lack of proper terms, I just started flying Airbus and am much more familiar with Boeing). The speed will increase beyond the upper magenta speed limit until the computer gives up on the descent and starts a standard 1k FPM descent rate. If I drop the spoilers, that's when I get the 8000 FPM descent rate until, again, the computer realises it's speeding up too much and reduces to 1k FPM.

 

I see there is a new experimental version released of 1.2.3.1 and 1.2.3.2. One of the listed fixes in 1.2.3.1 is "Better prevention of Stuka dives" so I'm updating now and about to do a test flight. I will advise in a couple hours if this resolved the issue.

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14 minutes ago, John Williams said:

I see there is a new experimental version released of 1.2.3.1 and 1.2.3.2. One of the listed fixes in 1.2.3.1 is "Better prevention of Stuka dives" so I'm updating now and about to do a test flight. I will advise in a couple hours if this resolved the issue.


Yeah. I believe the update will solve this issue for you. Sounds extremely familiar with what I experienced when I was investigating this issue before the fix was implemented. Let me know how it turns out :)

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Unfortunately, it looks like one of the updates broke the FMGC. If I click the top row of buttons to open the menu to load state, fuel/payload, options, etc the screen is blank. I'm troubleshooting now.

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1 minute ago, John Williams said:

Unfortunately, it looks like one of the updates broke the FMGC. If I click the top row of buttons to open the menu to load state, fuel/payload, options, etc the screen is blank. I'm troubleshooting now.


Please restart your PC. That should fix it.

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13 minutes ago, Secondator said:


Please restart your PC. That should fix it.

 

That resolved it, thanks. Test flight in progress.

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Unfortunately, the rapid descent issue has NOT been resolved. I did a flight from KIAH to KMEM, during which I flew the HOBRK3 arrival. I was cruising at FL370 and verified the crossing restrictions were properly entered into the flight plan, and that the wind uplink was in place. I activated managed descent mode approximately 15 miles prior to the planned TOD, which was near the OTIS waypoint. Upon nearing OTIS, the descent path suddenly plummeted past me, resulting in a 4000 FPM+ descent trying to keep up with it until the computer gave up and defaulted back to 1000 FPM. 

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Please post your flightplan, I'll try to fly it

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Have You made a test without wind uplink and with wind uplink have you checked if there is a change of wind speed during descent.....??

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14 hours ago, mopperle said:

Please post your flightplan, I'll try to fly it

 

KIAH to KMEM: LURIC6 HAWES ELD HOBRK3 at FL370

 

I really don't think the flight plan has anything to do with it, as I have tried various different flight plans with and without STARS to different airports, but maybe I'm missing something.

 

12 hours ago, AAC47 said:

Have You made a test without wind uplink and with wind uplink have you checked if there is a change of wind speed during descent.....??

 

I've done it with a wind uplink, without the uplink, with a headwind, with a tailwind, with no wind... It happens no matter what the wind is doing.

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I show the same with the high descent rate and have to fly the STAR in vertical speed mode. It happens on every STAR I fly and the altitude restrictions are properly entered. It's diving to chase the green dot at +5000FPM. I remember we had the same issue on the old FSX version a long time ago and it was fixed. 

 

Anyone else out there experiencing this on the A318/A319 or A320/A321?

 

Thank you

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Cant remember to have had this with the FSX version. And it was already solved with the P3Dv4 version. Il try to make the flight today evening, but need the exact flightplan, something like above is not enough, as e.g. HOBRK3 got different versions depending on the rwy.

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Below are two of my latest routes when it happened. It dived steeply on initial descent and stabilized after the last altitude contraint was met. One constraint was manually entered on the HILEY7 for Milsy at 280 and 16,000.

 

Descent was in managed mode with no speed brakes deployed or overspeed. MCDU Winds were entered from ASP4 but also happens with no winds imported. Weather was clear with no joystick or null zone issues when hand flying.

 

A321 - FL340 - CI 30

KLGA to KMIA

RWY 31 - WHITE J209 SBY KEMPR DIW AR22 JORAY HILEY7 to RWY 12

 

A321 - FL210 - CI 30

KDCA to KLGA

RWY 01 - DOCTR4 AGARD KORRY4 to DIALS for RWY 31 Visual

 

Thank you

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13 hours ago, mopperle said:

Cant remember to have had this with the FSX version. And it was already solved with the P3Dv4 version. Il try to make the flight today evening, but need the exact flightplan, something like above is not enough, as e.g. HOBRK3 got different versions depending on the rwy.

 

-KIAH RWY 33R LURIC6.HAWES ELD.HOBRK3 KMEM RWY 18R, cruise altitude FL370

-KSLC RWY 34R DEZRT1.MVA.MOD8 KSFO RWY 28L, cruise altitude FL380

-ATL RWY 08R SMKEY2.BOBBD HUCHH SUG KAVL RWY 16, cruise altitude FL230

 

These are just 3 of the flights I've done recently. As I said, it's happening on literally EVERY flight I do.

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Ok, did just this flight: KIAH LURIC6.HAWES HOBRK3.ELD DWSON KMEM

- Airbus 320 CFM v. 1.2.3.6

- no weather

- highest descent rate 3400 ft/min at the beginning of the descent

- all speed and alt cstrs met without any problem

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My descent ball bounces at each waypoint. Once I reach a waypoint the ball starts back on top and dives while the aircraft pitches down to chase it at high rate. I noticed the ball is green instead of the magenta we see IRL, does that have anything to do with it? If not, anything else we can try?

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17 minutes ago, blindfinder said:

I noticed the ball is green instead of the magenta we see IRL

IRL both colours are possible ;)

19 minutes ago, blindfinder said:

If not, anything else we can try?

- doing a flight without weather

- which variant of the Bus and which revision

- numbers about load etc.

- which navdatabase used

- telling us at which point it actually happened (maybe taking a video)

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Does the aircraft every go beyond the upper magenta speed limit. A small dive is still possible as aircraft chases the green vertical deviation dot and dips the nose down until it reaches the upper magenta speed limit. This is normal behaviour and once it reaches this limit, it will rise the nose up to prevent speed increasing beyond the limits.

Cost index could also play a role here. Higher cost index means higher descend rate.

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Aircraft is always on speed within the magenta bracket. The dive is exaggerated at greater than  +4000FPM. The green ball is all over the place but the altitudes in MCDU are correct. I will try again without weather and a few other things later on.

 

BTW Nav data is also current but I did update it before running the A321 for the first time, maybe that effected it somehow, don't know.

 

I use a cost index of 30.

 

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On 4/11/2019 at 3:00 PM, Secondator said:

Does the aircraft every go beyond the upper magenta speed limit. A small dive is still possible as aircraft chases the green vertical deviation dot and dips the nose down until it reaches the upper magenta speed limit. This is normal behaviour and once it reaches this limit, it will rise the nose up to prevent speed increasing beyond the limits.

Cost index could also play a role here. Higher cost index means higher descend rate.

 

I've continued to test this issue, during which I've noticed the aircraft does not go above the upper magenta speed limit. What happens is the plane dives to keep up with the extremely steep descent angle until reaching the upper limit, then it raises the nose and "gives up" trying to follow the descent path. I have used cost indices between 5 and 75, with the same issue occurring (though of varying severity). 

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