777 Pitch down and dive

[jgoggi 65]

 

 

What you say makes no sense. If it doesn't recover the lost airspeed at 2-3000 ft/min down and increases to 10,000 ft/min how does it end up overspeeding? It must have passed through the target speed long before that and so started pitching up again.

 

Unfortunately what I say makes sense, since the aircraft behaviour in this case is not correct. See the video I made, you can clearly see that the aircraft realizes that it has reached the target speed again much later than it should, and not recovering in time with that rate of descent (10000 fpm!) means going into overspeed. I did a lot of testing, even with zero wind, and I had it happening several times. Whatever, the real airplane will never go down with 10000 fpm!

[spesimen 135]

The A/P starts diving in order to regain the lost speed, but it would just need 2-3000 ft/min *and* until the speed is again the scheduled one, then the airplane should increase pitch and resume normal rate of descent. What the PMDG 777 does in a buggy way is diving up to 10000 ft/min (without a reason) and then, of course, it has difficulties in recovering, thus reaching overspeed. I already submitted a ticket about that, but it looked like they were reluctant to aknowledge the bug... 

 

well the reason is that you are entering throttle hold mode by commanding vnav descent some 20nm before the intended vertical profile, but the throttles stay at cruise thrust. they should be reduced significantly at this point, with letting the auto throttle handle it you will reduce to 250knots or so in a shallow dive and then it will tip over and follow the vnav path when you reach it eventually. maybe check that you aren't manually overriding the autothrottle if you aren't sure what it is trying to do for you. basically you're commanding that crazy dive and then wondering why it can't recover from it! on how the different throttle modes work (the clue is the changes on the FMA in front of you) it will hopefully make more sense if you read about it in the manual or check this thread which has a lot of info...http://forum.avsim.net/topic/445253-autothrottle-hold-mode/  .... i'm not an expert myself so i can't really explain it in full detail. i think you will find if you leave the altitude set to what you want without commanding a change then when you hit the t/d it will descend like you expect. alternatively if you must reduce altitude before the profile, then use v/s mode and set your speeds and descents where you want them (also look at the DES NOW command in the fmc)..

anyway cheers and good luck

-andy crosby

It's definitely something similar to that. Couldn't find another one diving, but it does happen quite frequently which is why I don't think it was an updraft.

 

And here is another freeze.

https://youtu.be/kSO5peHj9h8?t=1h57m34s

 

also to the original poster, did you try enabling the pre-loading of sounds, it is somewhere in the FMC menus (the install manuals have pretty specific info about this) but that was to solve the freezing that happens when it tries to load the landing sounds on touchdown. it will eat VAS as the tradeoff. i don't know what capture setup you are using but a problem like that could be exacerbated if you are for example recording to the same drive as your fsx install and by having stuff that is going on using a lot of file bandwidth already. just a suggestion!

cheers

-andy crosby

[kevinh 409]

Unfortunately what I say makes sense, since the aircraft behaviour in this case is not correct. See the video I made, you can clearly see that the aircraft realizes that it has reached the target speed again much later than it should, and not recovering in time with that rate of descent (10000 fpm!) means going into overspeed. I did a lot of testing, even with zero wind, and I had it happening several times. Whatever, the real airplane will never go down with 10000 fpm!

My 777 doesn't do what you describe or what your video shows. Descend Now results in a 1000 ft/min descent until the flight path meets the originally planned descent path.

 

Are you retarding your thrust levers to idle after commencing descent? This is recommended by PMDG due to the way A/T hold mode works in the sim. The only times I've had descent problems in the 777 I've forgotten to do this.

[777simmer 117]

That first video...with the totally insane pitch down attitude while still climbing is simply not possible.

 

Unless...

 

Unless you were caught in a severe thunderstorm, being sucked up in a 10.000ft/min updraft.

(something that sometimes realy ruins the day for glider pilots I am told)

 

So, this has nothing to do with FMC modes or Autopilot misbehavior.

 

It can only be a corrupt install or ASN in my opinion.

[SuperCell 10]

Okay thanks everyone. I'll try out the sound fix for the freezing. VAS isn't an issue for me. I'll reinstall ASN and the 777 too. Does anyone want to suggest what maximum updraft/downdraft and maximum cloud/wind turbulence they use? Mine is just maxed out. I'll report back on Friday.

 

 

i don't know what capture setup you are using but a problem like that could be exacerbated if you are for example recording to the same drive as your fsx install and by having stuff that is going on using a lot of file bandwidth already. just a suggestion!

 

I use OBS to stream/capture which is on my other drive and it takes a lotttttt of bandwidth.

[skelsey 765]

 

 

I'll reinstall ASN and the 777 too. Does anyone want to suggest what maximum updraft/downdraft and maximum cloud/wind turbulence they use? Mine is just maxed out. I'll report back on Friday.

 

I don't think you need to reinstall ASN, just wind the sliders back. I'm not at home at the moment, but mine are around 30% from memory. Any more than that and even the lightest of chop results in being bounced around all over the shop with intermittent stick shaker activation -- certainly not realistic.

[777simmer 117]

Just watched the second video of the OP.

 

The freezes would support the thought of a corrupt install but to be honest it looks more like he is asking too much of his system.

 

As in high scenery load + high FSX settings? + PMDG complex aircraft + weather program = possible performance problems.

 

You need a well tuned high performance system to run all that at once!

 

To the OP:

What hardware (CPU/memory/GPU) do you have?

 

Try reducing FSX settings (especially AI Traffic puts a high load on FSX) and try not to use scenery and clouds with HD textures.

Also try reducing ASN settings so it reduces the load on your system (I dont use ASN, but from what I understand you can reduce the number of cloud layers, etc)

 

Anything you can think of that reduces the load FSX puts on your PC might help get rid of freezes and strange aircraft behavior (dive).

Your problems might all be caused by the system not being able to keep up with all the calculations.

[SuperCell 10]

You can't be serious? Given the circumstances, most systems would run it as laggy as this. Everything I have is completely optimized... no ai. 1024 textures. 60nm cloud draw, cloud layers=4, vector disabled, other scenery disabled. I use a 3570k @4.2, 8 gigs of ddr3 gskill sniper series @1600 or so mhz idk off the top of my head...and a 1 gig 7850. It does just fine. Keep in mind that I was streaming and that dumbs down performance profoundly. It freezes like that regardless if I'm getting 45 or 5 fps and fsx never ooms either

 

Here it's smooth with no freezing. 

 

 

Smooth with freeze: (ignore the guy talking)

 

More smoothness:

[skelsey 765]

Have you run an adware/spyware scan on your PC lately?

 

I recall way back in the FS2000 days a chap saying that he had a similar issue -- generally smooth performance with micro freezes every now and then -- which cleared up after he ran an Adaware scan and got rid of a load of little pieces of junk that had accumulated.

 

Not guaranteeing this is the cause, but just a thought.

[vr-pilot 11]

Regarding the "nose down pitch" thing:

I would also say that there is some heavy (audible) updraft annoying your T7...

(IMO maybe "realistic" but more a kind of "maxed out force of nature dimension"; or just "normal weather" for your region of flying in terms of BEA AF447 report :blink:   Greetings go to "kevinh"...)

 

Regarding the "freezes":

your videos compare a daylight NGX approach into ENBR (Bergen/Norway) being fluid with a sunset T7 approach into EGLL (London Heathrow/UK) being temporarily freezing.

So there are three elements that make the comparison quite "problematic":

time of day (texture changes, GPU), aircraft flown (add-on complexity, CPU) and location used (scenery complexity, CPU+GPU).

In addition to that I always hear some "nice" tire squeaks (after your freezes) on touchdown.

Is it possible that there is an add-on running other soundfiles or something similar?

Trying default soundfiles (or even "better" the PMDG 22kHz versions) in combination with the already mentioned T7 FMC sound files preload option "ALL" (instead of "selective" or "off") could help here.

 

Always happy landings! B)

[777simmer 117]

You can't be serious? Given the circumstances, most systems would run it as laggy as this.

Serious about what?......that you might be asking too much of your hardware or FSX?

Sure I am......I did not know what hardware you were using so I thought I would ask.

I did not mean it as an insult but as something to consider before you start reinstalling things.

 

Anyway....so you think the freezes you have are normal then?

I thought you posted the freeze video because you wanted it fixed.

I dont mean that sarcasticly.....it could well be that it is normal to have these freezes if one is trying to make videos of FSX.....I wouldnt know, I never made an FSX video.

 

But In that case I dont understand why you posted the freezes video.

 

EDIT:

I just watched your latest videos and I see what you mean.

The 737 is definately doing better than your 777.

But like Claus mentioned....the two flights are not compareable.

 

To compare apples with apples you have to do two flights that are the same,..... same airport, same approach, same weather, same time of day etc etc.

Even then, no two flights will ever be the exactly the same (clouds are never at the same place) but it will be closer.

 

Maybe I missed it, but what is your 777 performance like when you do not video your flight?

Still freezes/stutters and violent pitching?

[SuperCell 10]

Yeah, it's still the same with the freezing and VNAV thing just slightly higher fps when I'm not 'filming'... Yeah, I guess my response was pretty hostile. Didn't really mean that... I just typed what came to my head. And Claus, it's the default PMDG 777 sound. I think I still have the autosave from that flight, so I might try to reenact it this weekend. The longer I fly, the worse performance I get (obviously) and my computer was on pretty much that entire weekend running FSX so....yeahhh maybe that contributed to it. I run malwarebytes sometimes, and nothing really ever comes up .

[777simmer 117]

Yeah, it's still the same with the freezing and VNAV thing just slightly higher fps when I'm not 'filming'... Yeah, I guess my response was pretty hostile. Didn't really mean that... I just typed what came to my head. And Claus, it's the default PMDG 777 sound. I think I still have the autosave from that flight, so I might try to reenact it this weekend. The longer I fly, the worse performance I get (obviously) and my computer was on pretty much that entire weekend running FSX so....yeahhh maybe that contributed to it. I run malwarebytes sometimes, and nothing really ever comes up .

Autosafe....mmmmm....did you delete all those saved panel states that are saved with each flight?

Otherwise you end up with hundreds of panel states inside the PMDG folder and who know what that does to performance.

 

Definately reboot your PC after a few flights.

You want to elliminate all posiible factors that could affect FSX performance.

 

And one more thing I have to ask.

Since you have an overclocked system.....is there a chance that you installed the PMDG777 or the latest update for it while the PC was still overclocked?

That could cause problems as well if the overclock is not 100% stable.....(which is hard to tell for most of us non PC techies).

If you did install or update overclocked, then I definately recommend a reinstall with the bios at default settings.

[Sam 68]

So I have been reading trough the topic and I can't figure out why you don't disable the weather engine as an attempt to isolate the problem..

 

Every possible symptom has been suggested, and the behavior of the aircraft is correct as stated multiple times.

 

Try it so we can isolate weather being an factor or not

[777simmer 117]

Yes, that too, lol :-)