Turbulence Values at 0x0E98

[pilotjohn]

I was trying to determine the values for LGT, MDT, SVR, EXTRM turbulence as read at 0x0E98.

I launched at KTTN, and simply changed the turbulence setting on the default wind layer with a 10KT wind.

Reading the values at 0x0E98 worked for LGT and MDT (128, 192 respectively) but would return only 0 for SVR and EXTRM, despite all weather readings showing the H and S for the setting.

Any suggestions as to why? And what those values are? Can these be relied upon?

1711611 Weather Received (type 4 request, Interpolated): "????&A0 201638Z 35910KT&D609MG 100KM&B0&D4572 CLR 14/04 Q1013
1714794 Weather Received (type 5 request, Nearest): "KTTN&A64 201628Z 35910KT&D609MG 100KM&B-64&D4572 CLR 15/05 Q1013 "
1717961 Weather Received (type 1 request, AtStation): "GLOB&A0 201628Z 35910KT&D609MG 100KM&B0&D4572 CLR 15/05 Q1013 "

  1719521 LUA: Cloud Type: 0
  1719552 LUA: Cloud Cover: 0
  1719583 LUA: Cloud Icing: 0
  1719614 LUA: Cloud Turbulence: 0
  1719645 LUA: Precipitation Rate: 0
  1719677 LUA: Precipitation Type: 0
  1719708 LUA: Wind Speed: 10+0
  1719755 LUA: Wind Direction: 358.40148925781+0
  1719786 LUA: Wind Turbulence: 192

747650 Weather Received (type 5 request, Nearest): "KTTN&A64 201628Z 35910KT&D609HG 100KM&B-64&D4572 CLR 15/05 Q1013 "
750988 Weather Received (type 1 request, AtStation): "GLOB&A0 201628Z 35910KT&D609HG 100KM&B0&D4572 CLR 15/05 Q1013 "
763172 Weather Received (type 4 request, Interpolated): "????&A0 201632Z 35910KT&D609HG 100KM&B0&D4572 CLR 14/04 Q1013 "

   763562 LUA: Cloud Type: 0
   763593 LUA: Cloud Cover: 0
   763624 LUA: Cloud Icing: 0
   763656 LUA: Cloud Turbulence: 0
   763687 LUA: Precipitation Rate: 0
   763718 LUA: Precipitation Type: 0
   763749 LUA: Wind Speed: 10+0
   763796 LUA: Wind Direction: 359.00024414063+0
   763827 LUA: Wind Turbulence: 0

839113 Weather Received (type 4 request, Interpolated): "????&A0 201633Z 35910KT&D609SG 100KM&B0&D4572 CLR 14/04
Q1013 "
842296 Weather Received (type 5 request, Nearest): "KTTN&A64 201628Z 35910KT&D609SG 100KM&B-64&D4572 CLR 15/05 Q1013 "
845603 Weather Received (type 1 request, AtStation): "GLOB&A0 201628Z 35910KT&D609SG 100KM&B0&D4572 CLR 15/05 Q1013 "

   861484 LUA: Cloud Type: 0
   861515 LUA: Cloud Cover: 0
   861546 LUA: Cloud Icing: 0
   861577 LUA: Cloud Turbulence: 0
   861609 LUA: Precipitation Rate: 0
   861640 LUA: Precipitation Type: 0
   861671 LUA: Wind Speed: 10+0
   861702 LUA: Wind Direction: 359.00024414063+0
   861733 LUA: Wind Turbulence: 0

A similar thing seems to happen for cloud turbulence as well.

Also, do the values between cloud and wind supposed to be the same for the same level of turbulence?

FSUIPC 4.749f

[Pete Dowson]

FSUIPC 4.749f

There were changes in this recently. Have you checked 4.753?

Is there a discrepancy between what you find in those newly populated offsets and the regular NWI or AWI readouts? Have you checked with the readouts in WeatherSet2? Because the source of the data is the same for both. And you need to log the aircraft altitude as well, please, because the values in those new offsets are dependent on that.

[LATER]

Hey, there's an error in the way FSUIPC decodes and encodes the turbulence. I think the METAR format definition changed sometime between the original FSX Betas and the releases, because I have them dpcumented as:

N - None (default), O - Light, L - Moderate, M - Heavy, S - Severe

I seem to remember I thought they were odd at the time, but maybe it was an early bug in FSX which was later corrected, presumably before release. The correct values I see now are:

N - None (default), O - Light, L - Light, M - Moderate, H - Heavy, S - Severe

which, apart from the two alternatives for "Light" make much more sense.

What I can't understand why no one has noticed this before, or, rather, they have but assumed like I did recently that the discrepancies were results of buggy FSX weather implementation.

The fix is really very easy. I shall upload FSUIPC 4.754 within the hour.

Regards

Pete

[pilotjohn]

There were changes in this recently. Have you checked 4.753?

I have, and the same issue is present. The aircraft altitude above was on the ground at 66 meters.

Is there a discrepancy between what you find in those newly populated offsets and the regular NWI or AWI readouts? Have you checked with the readouts in WeatherSet2? Because the source of the data is the same for both. And you need to log the aircraft altitude as well, please, because the values in those new offsets are dependent on that.

I don't have a quick NWI Lua to check with, but using WeatherSet2 a similar problem appears. When turbulence is set to Heavy, WeatherSet2 shows 0 for Turb, even though the METARs (Interpolated, AtStation, and GLOB) in the logs show the H turbulence value (weather using GLOB or "" ICAO). Severe appears to show in WeatherSet2 but not the offset.

The values for Turb in WeatherSet2 seems to be off by 1 below H (they show up as 0 for None, 2 for Light, 3 for Moderate, 0 for Heavy and 4 for Severe). The offset shows 0 for anything above Moderate. The cloud turbulence offset value does not agree with the the wind values. Moderate cloud shows 216 instead of 192, and light shows 144 instead of 128.

It seems there's something quite screwy going on.

The progression 128 192 224? 240? would seem to make sense for L M H S, but I'm not sure how 144 216 252? 270? would be used for cloud.

[Pete Dowson]

It seems there's something quite screwy going on.

Please see my previous reply. I amended it as you were posting your reply.

The progression 128 192 224? 240? would seem to make sense for L M H S, but I'm not sure how 144 216 252? 270? would be used for cloud.

The numbers are meant to emulate the encodings which were available since FS98 days. The offsets being used (0Exx) are part of the FS98 offsets, so I made them the same for consistency. The wind turbulence is basically 64 * N (N = 0 to 4). I seem to recall that the cloud turbulence in FS98, FS2000 and, I think, FS2002 only had 4 values, not 5 and went 0, 72, 144, 216. The top value i added for Severe should be encoded 252 not 270. I think it does that for the FS98 offsets. I'll check why it's not so limited in the newer "at aircraft level" offset.

[LATER]

Checked. There's definitely no way it should ever get 270. It's 72 * N with a max imposed of 252.

Regards

Pete

[Pete Dowson]

The fix is really very easy. I shall upload FSUIPC 4.754 within the hour.

Okay, get 4.754.

Last now till at least January 6th 2012. Have a Happy Christmas!

Regards

Pete

[pilotjohn]

The numbers are meant to emulate the encodings which were available since FS98 days. The offsets being used (0Exx) are part of the FS98 offsets, so I made them the same for consistency. The wind turbulence is basically 64 * N (N = 0 to 4). I seem to recall that the cloud turbulence in FS98, FS2000 and, I think, FS2002 only had 4 values, not 5 and went 0, 72, 144, 216. The top value i added for Severe should be encoded 252 not 270. I think it does that for the FS98 offsets. I'll check why it's not so limited in the newer "at aircraft level" offset.

Ok... so /64 for wind and /72 for cloud. Perhaps these transforms can be added to the offset documentation. Merry Christmas to you too.

[Pete Dowson]

Ok... so /64 for wind and /72 for cloud.

Except that won't work for the 252 value unless you round up.

Perhaps these transforms can be added to the offset documentation.

Well, yes, if you want straight numbers I suppose. They are only fiddled like that to make them look a bit like FS98-FS2002 values, all in the name of continuous compatibility for programs written in those times.

Regards

Pete

[pilotjohn]

Seems to work... thanks!

[Pete Dowson]

Seems to work... thanks!

I've just withdrawn it. I'll upload another in a few minutes. Please destroy that one, else I'll have ot increment the version number again.

The FS98 compatible values for wind turbulence in FSUIPC1,2 and 3 was 0, 64, 128, 192, 224 and 255 -- 6 values. Because FSX only had 5 I tried to apply those to get the same sort of 'feel' as in FS2002 and before, so used 0, 64, 128, 192 and 255., just missing out the 224. However, I just realised i'm multiplying by 64 but not checking for > 255, so I've had to fix that -- many programs will assume it fits in a byte (though documented as 2).

So, the "proper" version 4.754 will give *64 but limited to a max of 255.

Pete

[pilotjohn]

I've just withdrawn it. I'll upload another in a few minutes. Please destroy that one, else I'll have ot increment the version number again.

The FS98 compatible values for wind turbulence in FSUIPC1,2 and 3 was 0, 64, 128, 192, 224 and 255 -- 6 values. Because FSX only had 5 I tried to apply those to get the same sort of 'feel' as in FS2002 and before, so used 0, 64, 128, 192 and 255., just missing out the 224. However, I just realised i'm multiplying by 64 but not checking for > 255, so I've had to fix that -- many programs will assume it fits in a byte (though documented as 2).

So, the "proper" version 4.754 will give *64 but limited to a max of 255.

Pete

I saw that and had the issue, but re-read the documentation which stated 2 bytes, so I didn't complain. :)