Sign in to follow this  
GDex

Auto Time Compression Going Wild

Recommended Posts

Strange thing happened to me yesterday. I was flying the B777-200LRX from LCLK (Larnaca, Cyprus) to CYQB (Quebec City), a 4,774 NM journey. I used Auto Time Compression at 8X (controlled by the chronometer switch) from the time I reached cruise altitude, and kept using it except for the step climbs. Everything went fine until I had about 550 NM to go. I then noticed several abrupt changes in speed and altitude even though the wind direction and speed were constant (I use Opus for weather interface). I went off and on Auto Time Compression a couple of times to stabilize things. Then, when I was about 450 NM from destination, the Auto Time Compression suddenly shot up to a ridiculous number like 128X or more. I immediately paused the flight, and turned the Auto Time Compression off using the FMC. However in the few seconds it took me to pause the flight, the plane went on right past the next waypoint (where it was supposed to do a 19° turn) and travelled about 200 NM. After I had stabilized the aircraft and got going again (without Auto Time Compression), it behaved as expected, i.e. it started turning back towards the waypoint it had bypassed. At this point, I intervened through the FMC and made it go direct to the next logical waypoint (bypassing 2 waypoints) and from then on, the flight carried on normally and I landed at destination without any further problems.

 

 

 

As anyone ever run into that problem? Any ideas as to the cause?

 

 

Gaétan Dextras

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

Hi Gaétan. Hope you are well. I've read your post :-). But I didn't have a good answer. The only thing I could think of was that this ridiculous behaviour was supposed to be corrected in an earlier update. Is your 777 fully updated?

 

Cheers

Lasse Kronborg

Share this post


Link to post
Share on other sites

Hi Lasse. Thanks for replying. The last update of my T7 was the SP1c done on 23 October 2014. I bought the original T7 on 20 Dec 2013, and installed SP1 on 22 July 2014. Looking at the development history in the text note that came with SP1c, I notice that I missed SP1b. Can that be an issue? Or does SP1c include SP1b?

Share this post


Link to post
Share on other sites

I've had similar events but am unable to reproduce. Are you able to reproduce the event?  If so, then please explain how this can be done and put it in a trouble ticket at PMDG product support on line ( support.precisionmanuals.com ).  Keep in mind that I have flown many many more hours in beta than most customers do in normal hobby use; therefore, I believe if I cannot reproduce an event than it was probably not the PMDG simulator but something in my system.

 

A couple of observations, first you do not have to disable auto time compression for step climbs because it automatically goes to x1 for heading/altitude changes. Second, using x8 is the maximum recommended but not always the best to use depending on your system.  The events I experienced were all on my older/slower rig that I rebuilt about a month ago that would go x8 but had to pause for scenery updates. Even now, with a fairly high-end rig I prefer x4 to x8. Just my opinion.

Share this post


Link to post
Share on other sites

Hi Dan. Thanks for responding to my issue. Since the incident occurred, I have done only 1 flight on the T7 and this event did not occur. I would not know how to try to reproduce the event, since the aircraft was flying straight and level in cruise at x8 when it occurred; the wind was steady.

 

 

 

My rig is described under my name in my posts. I believe it is sufficiently powerful to run the PMDG aircraft without any problem. I normally get FPS rates in the thirties.

 

 

 

As I indicated, I am running Opus Software as weather engine, and it has a feature whereby the sim is first slowed back down to a steady x1 rate before the weather is injected, then raises the simulation rate back up to whatever it was before. I am wondering if there could be an interaction between this Opus action and the PMDG Auto Time Compression feature and the FSX Simulation Rate feature. In fact, do you know if the PMDG feature uses the FSX Simulation Rate feature or if it is independent?

 

 

 

One thing I did notice on all my long T7 flights is the aircraft behaviour when running at x8. Initially, everything is smooth and normal. But when about ¾ of the way through the flight, I start getting sudden speed and/or altitude changes. It also starts being “sloppy” in turns: normally, it starts turning a bit before a waypoint and merges smoothly into the new direction. But at some point in the flight, again about ¾ of the way through the flight, it starts overshooting the turn, then overreacting the other way, does this a few times, and finally settles down in the desired direction. It looks like the program (FSX and/or the aircraft) is “getting tired” at the end of a long flight! If I fly in x1 those issues do not occur. Such behaviour was going on when the incident occurred. So I think the “going wild” incident might be related to the behaviour described in this paragraph.

 

 

 

As you said, the solution is probably running at x4 instead of x8, and I’ll just have to choose shorter trips. Nevertheless, it might be interesting for PMDG to investigate these issues and possibly improve their program in the future.

Share this post


Link to post
Share on other sites

 

 


I would not know how to try to reproduce the event, since the aircraft was flying straight and level in cruise at x8 when it occurred; the wind was steady.

 

I was flying a N Pacific route overflying PANC when it occurred, so I tried reproducing by flying the same flight with about the same configuration. To go a step further, one could reuse the same weather as well. I use ASN and it doesn't affect the simulation during weather ' injections ' which one never notices. Maybe OPUS has a roll but I doubt it.

 

Problems with heading/altitude control in LNAV/VNAV mode were addressed in latest SP1C update. I assume you have the latest version, which is easily checked with the Operations Center.

Share this post


Link to post
Share on other sites

I do have SP1C installed, but it certainly did not resolve the heading/altitude control in LNAV/VNAV mode  issues when in x8. I will do some testing during the holidays and let you know the outcome.

Share this post


Link to post
Share on other sites

Gaetan-

 

I beg to differ with your categorical statement on what was or was not resolved- especially since I have quite a bit more data to work with than you do.  :P

 

Rather than delivering a dictum here on what you think we didn't do, or insisting that we "improve our program" it might be more helpful to take a tone of cooperation- and suggest ways that one of us or our beta members (such as Dan- who offered to help you earlier) might reproduce your problem.

 

I am going to go out on a limb and suggest that it is highly likely that the problem is local to your machine, as if we had a problem with the airplane in the wild- we would be overrun with similar reports.  (You can see this happen in real time if you are here in our forums post release...  a problem that exists- tends to become quite visible...)

 

So- let us know if you find a way to reproduce the problem and we will evaluate with you.

 

In the mean time- I strongly recommend that you perhaps run the updates again- as we have seen a few cases where some users managed to set READ ONLY permissions on their dlls, and this allowed the patch installer to update the config files but not the dlls...

 

Good luck, and keep us informed.

Share this post


Link to post
Share on other sites

Robert

 

I have checked the dlls in the dll folder under the PMDG folder, and in all of them, the read-only box was clear. I nevertheless ran again the SP1C update (although it gave me a message to the effect that I was reinstalling the same version). I will find out in my next flight if that worked and let you know one way or the other. Incidentally, my FSX program is located directly in the C drive, not in a program folder. When I install any EXE file, I start by turning off the UAC and my anti-virus.

 

I felt that the first problem that I reported (Auto Time Compression Going Wild) was just a unique anomaly, but I thought I should report it anyways in case it could help someone in the future.

 

Then in the subsequent exchange with Dan (he was very cordial and helpful), I mentioned this other problem (heading/altitude control in LNAV/VNAV mode) because I thought it might be related to the first problem, and it occurs on every flight.

 

It was in the same post that I wrote “Nevertheless, it might be interesting for PMDG to investigate these issues and possibly improve their program in the future.” This statement is very different than “insisting that we "improve our program"”. It was just a suggestion.

 

The fact that the problem kept occurring after the installation of SP1C led me to state “it certainly did not resolve the heading/altitude control in LNAV/VNAV mode issues when in x8”. It was not “delivering a dictum here on what you think we didn't do”. I just made a plain observation of what I saw.

 

You mentioned “it might be more helpful to take a tone of cooperation” – that was my exact intent in making this post in the first place. I certainly did not expect such a blast in return. Now I am really sorry that I made this post.

 

Regards

Share this post


Link to post
Share on other sites

Gaetan, don't regret anything (see Gibbs rule #6).  The problems in x8 might just be that x8 is unstable on your rig, regardless of fps there's more going on behind the scenes. For example, I cannot fly the PMDG 737NGX at x4; both x2 and x8 are fine but not x4.  This certainly is not a PMDG problem. Happy contrails.

Share this post


Link to post
Share on other sites

Dan, I had never heard of Gibbs rules (my TV watching is usually limited to news and hockey games). Read up on them and found them interesting. However, when I wrote that sentence, I did not mean it as an apology, but rather as in "I'm sorry I ate too much". You're probably right about x8. Since that first flight I referred to when I started the topic, I did another (SBGR to CYYZ) in x8 and had the same heading/altitude control in LNAV/VNAV mode problem, however no Auto Time Compression Going Wild problem. I will redo LCLK-CYQB in x8, but when it starts going funny, I'll reduce to x4. I'll post the outcome.

Share this post


Link to post
Share on other sites

Dan, I finally got around to re-flying LCLK-CYQB. I used the exact same flight plan as the first time. Flight distance: 4774 NM. Flight duration: 11:44 hrs (2nd time). Both times, I flew in real weather as introduced by Opus. Average wind at cruise altitude: 1st flight: 274°, 38 Kts. 2nd flight: 269°, 73 Kts. So the wind was pretty much from the same direction, but much stronger the 2nd time. With such a headwind, the 2nd flight took longer than the 1st.

 

The “Auto Time Compression Going Wild” problem did not occur. There was no case of overshooting in turns. However there were 12 instances of abrupt speed/altitude changes. Each time, I paused the sim and recorded the time and distance from departure. All of these occurred at cruise altitude (FL320 initial, then FL340, then FL360). The first occurrence was at 1:25 hrs into the flight, then at varying intervals, however, there was a stretch of 2 hours where there was an instance every half-hour, +/- 2 minutes. After 8 hours in the flight, I had to pause the sim for about 4 hours. When I resumed the flight, it took about one hour before an instance happened, at 9:04 from departure. This was followed by 2 more instances at 9:33 and 9:46. After that, I was nearing the TOD point, so I went back to x1 and had no further instances; the flight completed without any other hitch.

 

I don’t know if this data can be of any use to PMDG. I could make it available in an Excel spreadsheet if they are interested. My conclusion for the future is I plan to use x8, but if I run into problems, I will scale back to x4.

Share this post


Link to post
Share on other sites

 

 


I plan to use x8, but if I run into problems, I will scale back to x4.

 

Good plan.  Maybe Opus has a forum where you can check to see if other users of this product have weather shift problems, which would give about the same indications and described.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this