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RaffaeleFiore

777...erratic inflight behavior

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After a long thinking between CS and PMDG 777, I decided to buy PMDG, convinced to buy the best product on the market.

After 'getting into confidence' with cockpit's countless functions on the ground, then came the time to fly.

The first flight was a short test hop, and everything run flawlessly.

But, during the first long haul flight (LFPG-ZSPD), i noticed something strange. At first I thought to a temporary bug, but, when the same thing happened in the second flight too (OMDB-LFPG), I realized that must be something wrong in the way this bird flies.

Coming to the issue itself, the a/c, in the cruise phase, seems to be unable to keep its track in presence of turbulences, both in LNAV and in HDG SEL modes, a thing I never experienced before with any addon aircraft (and I'm simming since FS98 times), including former PMDG products.

When flying through a turbulent area, the a/c starts uncommanded turns with considerable bank angles, bringing it out of its track up to 2 NM left or right, then turns towards its correct track again, crosses it and then turns back again, and again, until the turbulence is leaved behind. At first I thought it was a bug related to the 4x sim rate, but unfortunately this erratic behavior happens at 1x too. In a case the a/c even started a turn that brought it to deviate 60 degrees right respect to its track, and only in HDG SEL mode was possible to command it back (I have to assume the a/c would have continued to turn right undefinitely?).

The erratic behavior in cruise flight I described above is a thing that shouldn't happen at all, moreover in an high end product like the PMDG 777.

 

Is there something the PMDG staff plans to do to solve the described inflight erratic behavior?

 

Raffaele Fiore

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Hi,

 

Your answer may be found in the "PMDG 777 Introduction" PDF document provided in the Operations center on page 27 and from page 157 where PMDG explain quite extensively how the turbulences are handled in FsX and interract with the flight model.


Romain Roux

204800.pngACH1179.jpg

 

Avec l'avion, nous avons inventé la ligne droite.

St Exupéry, Terre des hommes.

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What weather add-on are you using to inject weather into the sim? As the post above mentions, the 777 intro manual discusses this problem, and explains why it happens, not just in PMDG, but in other complex add-ons.

 

I can say from personal experience that you should not have this problem if you use ASN for weather injection. It is one of the few injectors that appears to have completely solved this issue with add-ons


Jim Barrett

Licensed Airframe & Powerplant Mechanic, Avionics, Electrical & Air Data Systems Specialist. Qualified on: Falcon 900, CRJ-200, Dornier 328-100, Hawker 850XP and 1000, Lear 35, 45, 55 and 60, Gulfstream IV and 550, Embraer 135, Beech Premiere and 400A, MD-80.

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I had this issue with Active Sky X and the NGX. You can read more about it in the PMDG manual. I eventually cut my losses and moved to FS Global Real Weather and find it works much better with complex addons. 

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Hello,

I was not sure where to post this. I have read of many issues with the 777 vnav problems. My problem is kind of similar but also different in some ways. Last night, i was flying a hop from NZAA - YPPH. Everything went flawlessly. Inhave planned my descent a 100nm from TOD and set my MCP altitude to a lower altitude. When the aircraft reached TOD it would pitch up the nose 5 degrees, the speed would run down to idle and the aircraft would get stuck here for about 10 seconds or so. It then pushes the nose over and starts descending with a descent rate of 3500-5000fpm and the speed goes all over the place and then the engines and hydraulics will fail. Service based failures are turned off. Cam someone please tell me what to do to fix this problem? This is a brilliant plane but also not the first time it has done this, in fact, it has done this since my first install. This was a lot of money to pay for an add on that does not seem to work as it should. Please help....

 

Core i5 3Ghz

16GB RAM

Nvidia GTX650

Windows 8.1 64-bit (have the same problem with Windows 7)

Microsoft FSX

 

Kind regards,

Chris Homes

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Problem solved, as far as it seems.

I repeated the same flight (OMDB-LFPG), encountered the same turbulent area above the Iran/Turkey border, but this time the PMDG 777 kept its track firmly and straight. It flown exactly as one expects it to do.

FSX default weather (no weather add-on installed at this time).

I realized I had the "Disable effect of turbulences on the aircraft" option unticked in the FSX weather settings, has been enough to have it checked and here we go.

Thanks Budbud for the tip. I read the introduction manual but I forgot this 'detail' (it's so extensive!).

 

By the way: on short final at LFPG 09L I had wind 021/09, but this seems has been enough to make the A/P unable to land in Autoland mode. The A/T struggled to keep the ref speed (what it wasn't doing before the FSX weather modification above) and in some way succeeded in that, but the touchdown was a bit too rough anyway.

Is there something more I can do in order to avoid this sim's behavior?

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Thanks Budbud for the tip. I read the introduction manual but I forgot this 'detail' (it's so extensive!).

 

By the way: on short final at LFPG 09L I had wind 021/09, but this seems has been enough to make the A/P unable to land in Autoland mode. The A/T struggled to keep the ref speed (what it wasn't doing before the FSX weather modification above) and in some way succeeded in that, but the touchdown was a bit too rough anyway.

Is there something more I can do in order to avoid this sim's behavior?

 

Hi,

 

No problem, it's easy to miss such info in so many documents.

 

Regarding the autoland, it is certified up to 25 knots crosswind so it shouldn't be an problem to use autoland in these conditions except if you encounter windshear. Maybe you did and had no alert? I don't remember if the windshear alert is triggered with ASN installed and weather radar operating only or in any case... 

However, I use ASN for weather injection so I won't be of any help with FsX default weather engine. 


Romain Roux

204800.pngACH1179.jpg

 

Avec l'avion, nous avons inventé la ligne droite.

St Exupéry, Terre des hommes.

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