False TAT temperature indication with PMDG MD-11

[ailchim 206]

I'm having what looks like a previously reported problem, whereby at altitude, the TAT being picked up by my aircraft swings suddenly from a negative temperature to plus 40 or 50 degrees C. This appears to cause the aircraft to adjust EPR for hot & high conditions with a reduction in available power, which makes it impossible to maintain speed & altitude.The problem usually clears itself eventually but of course the flight is ruined by then. It has happened to me on at least 3 separate flights.I'm using ASA Build 433 with FSX SP2 under Vista 32 bit. FSX is running under FPS Limiter.The specific plane in question is the PMDG MD11, although I see no related posts on their support forum. The previous reporting of this error appears to relate to the PMDG B744.I'm using a fully registered version of FSUIPC to smooth turbulence which otherwise throws the MD-11 all over the sky. The only other add-ons I'm using of any note are Ultimate Terrain X and Fs2Crew, which I can't imagine have any bearing.Attachment 1 shows that I have TAT of +51 degrees at >FL300. This has dropped the CRZ EGT to 1.09, Attachment 2 shows the Nav Log for the area I'm in - the base figure is a uniform minus 43 degrees. Please note that I had step-climbed above the planned cruise alltitude of FL310 before the problem developed and I do this quite often, so that could be a factor.Attachment 3 shows I'm back to a TAT of -8 degrees and although SGT of 1.43 plus the low speed protection desecnt rate of 3,500 fpm have put me into overspeed, effectively I'm back to normal.I have a suspicion - although no definite evidence - that this may be connected with saving and restarting a flight - the weather in the restarted flight is then not as it was when it started, although of course I don't know how that might contribute to a incorrect TAT. The only reason for thinking this is that I only seem to have the problem with restarted flights, although that may be just conincidence.I have discovered how to fix this problem if not what causes it. If I go to FS World Weather & select Flight Simulator weather rather than User Defined, let the standard weather load then go back & select User Defined again, it seems to clear the +ve TAT, which put the engines back to the correct EPR.Before you ask, I haven't used any of the the default FSX aircraft since I opened the box.

[ailchim 206]

Could I have some advice on this? Even if to say it's not your product, in which case I'll take it up on the PMDG forum.Thanks in anticipation

[JSkorna 137]

Hi,With nothing to compare to, I would suggest a post at their forum. Please be ready when they ask about what happens in a default plane in these situations.Thanks,

[ailchim 206]

Thanks

[Joe L 62]

I have the same issue. Wondering if ASA could have an enhancement to limit temperature, say at the US Flight Levels (18k) or above? I am not sure what the real world variation can be at altitude, but what if there was an optional limit of STD +/- a limit (20 deg ??) Just a thought. I do have FSUIPC, but the limit temp change option doesn't seem to help for me, as the temps still climb to down right balmy at altitude (albeit slower). I am not saying this is the fault of either product, as I would rather fly that troubleshoot this issue (its hard to repeat for me, since it can be hours into a flight before it happens). It seems to happen in more remote areas over land for me, and less over water.Thx,Joe

[ailchim 206]

What aircraft are you getting the problem with? Is it only when you resume a saved flight?This isn't a question of normal fluctuations: at an original altitude above FL350, it clearly ought to be pretty cold wherever you are!And +51 degrees C is awfully hot even at noon in the desert.I'm afraid I'm too dim to know the difference between SAT & TAT but the ASA log says the SAT at my location & altitude should be -44 degrees (although I'd step climbed above the original route altitude of FL310). That doesn't convert to a TAT of PLUS 51 degrees.No, this is bad data from somewhere (most likely) or a bug in BOTH the PMDG 747 and the MD-11 (most unlikely).I will update this post if I get any feedback from the PMDG forum.

[Bob Scott 7,716]

I recommend the next time you see this, if you're running FSUIPC, go into the logging tab, put "34A8" into one of the offset boxes, select "FLT64" in the corresponding type dropdown box, and then check "FS Window"...this will put the current ambient temp at the acft in a window in FS. If it's abnormally high, then it's not a PMDG problem...it's the panel acting on a bad temp reported by FSX. If the OAT is normal, but you see TAT +51 on the panel, then the panel is at fault.If it's not the panel, then the next question is whether that abnormally high temp is the result of an FSX problem, or if it was written there because of an ASA problem. If you have a few gigs of disk space to play with, you can log all the SimConnect calls as Pete Dowson describes here:http://forums.simflight.com/viewtopic.php?f=54&t=58095When the temp anomaly occurs, shut down the sim, open the (very large) log file, and do a text search (starting at the end and working backwards) for the string "WeatherSetObservation" and you should find lines like this:

> 24.47553 [63, 113]WeatherSetObservation:Seconds=30, szMETAR="GLOB 231553Z 00000KT&D457NM 00000KT&A914OG 00000KT&A1829OG 00000KT&A2743NG 00000KT&A3658OG 00000KT&A5486NG 00000KT&A7315OG 00000KT&A9144NG 00000KT&A10363NG 00000KT&A11887NG 00000KT&A13411NG 00000KT&A14935NG 16KM&B-2000&D30000 1CU129&CU000FNVN000N 6CU209&CU000FMVN000N 15/13 15/10&A914 15/09&A1829 15/06&A2743 15/M05&A3658 15/M18&A5486 15/M31&A7315 15/M49&A9144 15/M59&A10363 15/M68&A11887 15/M76&A13411 15/M77&A14935 A3002"

The interesting part of this long string is at the end...the "A3002" at the end is the altimeter setting, it's the series of temp layers preceding that which we are looking at:

&A914 15/09&A1829 15/06&A2743 15/M05&A3658 15/M18&A5486 15/M31&A7315 15/M49&A9144 15/M59&A10363 15/M68&A11887 15/M76&A13411 15/M77

This is a series of temp layers...the "&A" means that it's an FS extension to the METAR, the next number is the base altitude of the layer in meters, and then you have the temp/dewpoint.So "&A914 15/09" means a layer beginning at 914m (1000 ft) with temp 15 and dewpoint 9 deg C. Likewise, "&A13411 15/M77" means a temp layer beginning at 13411m (44000 ft MSL) with temp 15, dewpoint -77.ASA sets all the temp layers the same based on acft altitude...notice that in the example above the temp is 15 deg C so all the temp dewpoint pairs are "15/something." So if you're at FL 350 on an ISA day, the temp should be -53 deg C at all levels. If it's high...i.e. 24/M79, then ASA is writing bad temps to the sim. If all the temps are OK back several minutes, then FSX is the culprit.I also note that in my example above, at the end of the string, the temps for the last layer (14935m/49000 ft) are missing from the METAR string, which makes me wonder if that could be part of the problem...the "&A14935" has no matching temp/dewpoint. Might be worth checking that one out, HiFiGuys.RegardsBob ScottColonel, USAF (ret)ATP IMEL Gulfstream II-III-IV-VColorado Springs, CO

[aguthrie 0]

I am experiencing the exact same problem with the Level-D 767. At FL350 the SAT reported by FSUIPC using the trick above was +15 and my TAT was 45-50. The plane was unable to maintain speed and altitude. I am using B435 and running ASA on a networked computer.

[Bob Scott 7,716]

I am experiencing the exact same problem with the Level-D 767. At FL350 the SAT reported by FSUIPC using the trick above was +15 and my TAT was 45-50. The plane was unable to maintain speed and altitude. I am using B435 and running ASA on a networked computer.

OK, so that means the problem is not the Level-D panel...it's that the OAT in the simulation is crazy high. The next question is whether this is the fault of ASA, and for that you need the SimConnect log file to determine what ASA is sending to the sim.Just out of curiosity, where were you flying when this happened?And for Jim/Damien--does ASA have any kind of sanity-checking in the code that would prevent writing data to the sim that's outside the bounds of reason (like a temp of +15 at FL350)? It seems that an option to limit ASA from writing out temps outside the range of ISA +/- 20 would be helpful.RegardsBob ScottColonel, USAF (ret)ATP IMEL Gulfstream II-III-IV-VColorado Springs, CO

[ailchim 206]

Thanks again for all this chaps! You seem to be getting closer. I'm still interested in this but unfortunately still haven't to make any time for flying. Hopefully this weekend and maybe I'll be able to contribute too. No sport on the box this weekend after all!

[aguthrie 0]

Just out of curiosity, where were you flying when this happened?

I was flying in South America from SLLP - SAWH, but the problem existed all the way down from Canada.I will look into the SimConnect logs.Thanks,Adam

[JSkorna 137]

Hi All,Bob: no, but we can look into a data check/filter if it is shown that this is an ASA data issue.I still would like to know what happens in a default plane? In the PMDG thread about this issue, some feedback was given that even with default FSX weather this can happen as well. This would point to a sim issue and not an ASA issue.Thanks,

[ailchim 206]

I suspect there would be no impact on a default plane. The PMDG & Level D offerings model the effect of TAT on engine performance, so when TAT goes to plus 50 degrees at high altitude, alarms go off, thrust drops to zero and the altimeter sets off towards zero at an alarming rate!Thus the occurence has a very obvious impact. In a default aircraft, I suspect nothing would happen at all. Is the TAT even displayed I wonder? That's going to make it a tough thing to pin down just to prove what happens with a default plane: firstly the default plane probably doesn't react when the problem occurs and secondly, we are effectively trying to prove a negative (i.e. that it doesn't happen and that the bug is in the PMDG or LDS aircraft) when it is at best an intermittent problem anyway. We could fly the default aircraft for days and not prove anything one way or the other.It's not surprising to me therefore that the people reporting these problems, whatever they are, are using top-end add-on aircraft. In fact, I'd hazard a guess that not many of your customers use the default planes. I didn't get any indication in the PMDG forum that the same thing had been seen with default aircraft. One poster did say they's seen the same problem with default FS weather. Is there a common link somewhere?I will repeat my remark that I think (NB think) I only get the problem when I restart a saved flight. I may be wrong and that may have nothing to do with it but some conceptual thoughts as to whether any vestige of the "old" weather could interfere with the "new" weather might be a helpful start.I completed a shortish but unsaved flight (1 hour 15 minute) flight in the MD-11 yesterday with no problems, so I can't add any hard information.

[Fritz Bayerlein 0]

I am having idential problems in the PMDG MD-11, FSX. On two separate occasions now the TAT has spiked to nearly 50C at high altitude, causing the aircraft to lose speed and power. It has actually caused a stall in flight at one point.This is a serious issue, almost as bad as the S-turning that ASA makes the MD-11 do. Can we get some more investigation on this? It has only started occuring with the latest update/build.

[aguthrie 0]

An observation.I just ran the same departure twice departing from SLLP using the LDS 767. The first time I followed my normal procedure which includes loading the flight plan into ASA. Sure enough, climbing through FL310 the SAT increased to 15 and stayed there.The second time I didn't load the flight plan into ASA and I am currently at FL390 with a SAT of -52 and no hint of any fluctuations.Maybe this helps?Adam