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Evan Reiter

Flying PMDG's 737 NGX May Produce Communciation/Radio Lag

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There has been a great deal of forum activity surrounding the release of PMDG's 737 NGX product which was recently released. My personal opinion of PMDG is that its aircraft tend to be top-of-the-line, and all releases prior to this one have been compatible with multiplayer.


For the past several months, the FSX multiplayer community has been aware that communication issues are almost exclusively caused by a "bad" (for want of a better term) aircraft. The aircraft does not have to be on a specific frequency or even be powered; the simple presence of the aircraft in the server can cause the communication fidelity to drop. We have observed this behavior with a handful of add-on aircraft, of which most have created patches that resolve the issues. You can find more information about the phenomenon at viewtopic.php?f=5&t=1725. According to one poster, the issues are caused by "incorrect" and "very ineffecient XML (& C) programming".


BVA is now investigating the possibility that the PMDG 737 NGX consistently or intermittently causes communication issue within our server. The consensus seems to be that there is an issue with the aircraft but that it does not always affect the session. It is therefore possible that some users might be able to fly the aircraft without negatively impacting others' experience.


The good news is that, despite the original response, PMDG has indicated that they have resolved this issue and plan to address it in the first service pack or patch they release (http://forum.avsim.net/topic/341571-pmd ... ng-thread/). The bad news is that, until the patch is available, anyone flying the PMDG 737 NGX in our session may be subject to ejection in the event that the server communications begin to lag with that aircraft online. You will, of course, be sent a PM before being ejected. For this reason, BVA advises members not to purchase the PMDG 737 NGX until the patch is confirmed to resolve multiplayer issues, and those members who have purchased it to be prepared to cut flights short in the event that communication issues appear. Additionally, BVA will ask for the support of those who have purchased the aircraft in evaluating the impact of the patch of the performance of the aircraft on communications.


My opinion, having not used the aircraft, is that it is worth the money and something I will buy once the issues are resolved. PMDG has a great reputation for quality aircraft and to my knowledge, none of its other aircraft cause issues in multiplayer. I really hope they address this issue quickly and effectively so they can maintain it.



Evan Reiter

Community Director
Administration Team

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Guest Brandon Carter

In addition to what Evan said, we've determined that one of the primary issues is with the coding behind the Spoilers.


Basically, the gauges of the aircraft are written in C++, however, due to some irregularities in the code, deploying the spoilers can result in a much higher than normal number of UDP packets to be sent to the server, causing the "flooding" issues. This can ultimately build up enough and result server issues, for example comm lag on all frequencies.


Still, however, there is other code in the aircraft that causes constant packet flooding, however these packets remain local, and they do not affect other players' or the server's performance, so they aren't as much as an issue in multiplayer.


If you choose to fly the 737 NGX in the server before PMDG issues the first service pack (as Evan linked to in the previous post), try to avoid using the Spoilers as they seem to be the source of the flooding issues.

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