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G-Forces at touchdown


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We've extensively used offset 0x030C to read vertical speed at touchdown; it provides a good clue as to the quality of the landing, but it's not used in the real world AFAIK. I was wondering if it would be possible to add another offset similar to 030C to read G-forces while airborne, then cease updating on touchdown.

I believe the offset to fetch from would be 0x11BA, but only while airborne, much like the relationship between 030C and 02C8.

Cheers!

Luke

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We've extensively used offset 0x030C to read vertical speed at touchdown; it provides a good clue as to the quality of the landing, but it's not used in the real world AFAIK. I was wondering if it would be possible to add another offset similar to 030C to read G-forces while airborne, then cease updating on touchdown.

I believe the offset to fetch from would be 0x11BA, but only while airborne, much like the relationship between 030C and 02C8.

Sounds easy enough. I'll put it on my list for attention in the next increment. Please keep an eye on the Updates announcement. If for any reason i don't do it, I'll post the reason to this thread.

Regards

Pete

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Thanks for adding this into 3.907 so quickly. I did a brief test this evening and it seems to work accurately. I'm wondering, however, if it might be better to get the value at the first frame *after* the aircraft is on the ground, rather than updating while in the air. The latter value (and FSUIPC's current behavior) seems to work well for vertical speed, but I seem to get a sub-one value for G forces, whereas one would expect this value to be >1 on touchdown.

Does this make sense? I recognize that the latter behavior is also significantly more complicated to implement, and I apologize.

Cheers!

Luke

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Thanks for adding this into 3.907 so quickly. I did a brief test this evening and it seems to work accurately. I'm wondering, however, if it might be better to get the value at the first frame *after* the aircraft is on the ground, rather than updating while in the air.

Ernot so sure that won't simply give you a "normal" rather than impact-related value.

The latter value (and FSUIPC's current behavior) seems to work well for vertical speed, but I seem to get a sub-one value for G forces, whereas one would expect this value to be >1 on touchdown.

Hmm. Before I make any changes, please monitor the values and check that FS is indeed doing what you think. I suspect it may not. You can do this by using a little Lua plug-in to read and log to a file the G-force continuously (with, say, a 5 or 10 mSec sleep per loop only, to make sure you don't miss any frames).

Don't you use FSX too? have you checked it there? With SimConnect working asynchronously it may give different results.

Regards

Pete

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Ernot so sure that won't simply give you a "normal" rather than impact-related value.

That might be true. I think we each have the same doubts, just on different sides of impact. :) I suspect I'm getting a normal, rather than impact-related, value.

Hmm. Before I make any changes, please monitor the values and check that FS is indeed doing what you think. I suspect it may not. You can do this by using a little Lua plug-in to read and log to a file the G-force continuously (with, say, a 5 or 10 mSec sleep per loop only, to make sure you don't miss any frames).

Ah, dragging me into Lua kicking and screaming! :) I've suspected that I need to learn how to do this for a bit. I'll dig into it later tonight. Apologies in advance if I come back with a few silly questions.

Cheers!

Luke

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Hmm. Before I make any changes, please monitor the values and check that FS is indeed doing what you think. I suspect it may not. You can do this by using a little Lua plug-in to read and log to a file the G-force continuously (with, say, a 5 or 10 mSec sleep per loop only, to make sure you don't miss any frames).

I downloaded the guides and example LUA plugins and was able to get something basic cobbled together in around 30 minutes. You deserve a hearty "thank you" for making things so easy to delve into from this perspective. So thank you!

Here's the data I logged. I had a 23ms sleep interval, and I'll give you the second I took off, as well as my landing. It's a VistaLiners 727 out of JFK 4L to LGA 31, my standard test flight. The landing is more interesting (but I figured I'd include the takeoff as well if anyone was interested). What's interesting is in both cases (I bounced my landing) the peak Gs don't seem to occur until about 50-75ms after FS detects we're on the ground.

I'll try an FSX run, assuming I can do this with an unregistered FSUIPC4. (I only have FSUIPC3 registered). If you want/need any other data, feel free to let me know.

Cheers!

Luke

msecs,timeL,ias,onGround,takenOff,G

45563,17:48:27,154,1,0,0.976

45578,17:48:27,154,1,0,0.976

45610,17:48:27,154,1,0,0.976

45641,17:48:27,154,1,0,0.974

45656,17:48:27,154,1,0,0.974

45688,17:48:27,154,1,0,0.974

45703,17:48:27,154,1,0,0.974

45735,17:48:27,154,1,0,0.973

45750,17:48:27,154,1,0,0.973

45781,17:48:27,154,0,0,0.854

45797,17:48:27,154,0,1,0.854

45828,17:48:27,154,0,1,0.741

45844,17:48:27,154,1,1,0.762

45875,17:48:27,154,1,1,1.091

45891,17:48:27,154,1,1,1.091

45922,17:48:27,155,1,1,1.411

45938,17:48:27,155,1,1,1.235

45969,17:48:27,155,1,1,1.008

45985,17:48:27,155,1,1,1.008

46016,17:48:27,155,0,1,0.922

46031,17:48:27,155,0,1,0.870

46063,17:48:27,155,0,1,0.858

46078,17:48:27,155,0,1,0.858

46110,17:48:27,155,0,1,0.877

46125,17:48:27,155,0,1,0.896

46156,17:48:27,155,0,1,0.915

46172,17:48:27,155,0,1,0.915

46203,17:48:27,155,0,1,0.931

46219,17:48:27,155,0,1,0.947

46250,17:48:27,155,0,1,0.963

46266,17:48:27,155,0,1,0.963

46297,17:48:27,156,0,1,0.979

46313,17:48:27,156,0,1,0.994

46344,17:48:27,156,0,1,1.006

46360,17:48:27,156,0,1,1.006

46391,17:48:27,156,0,1,1.019

46406,17:48:27,156,0,1,1.032

46438,17:48:27,156,1,1,1.045

46453,17:48:27,156,1,1,1.045

46485,17:48:27,156,1,1,1.123

46500,17:48:27,156,1,1,1.123

46531,17:48:27,156,1,1,1.125

46547,17:48:27,156,1,1,1.125

297766,17:52:38,125,0,1,1.046

297797,17:52:38,125,0,1,1.046

297813,17:52:38,125,0,1,1.046

297844,17:52:38,125,0,1,1.046

297860,17:52:38,125,0,1,1.046

297891,17:52:38,125,0,1,1.046

297906,17:52:38,125,0,1,1.045

297938,17:52:38,125,0,1,1.045

297953,17:52:38,125,0,1,1.045

297985,17:52:38,124,0,1,1.045

298000,17:52:38,124,0,1,1.045

298031,17:52:38,124,0,1,1.045

298047,17:52:38,124,0,1,1.045

298078,17:52:38,124,0,1,1.045

298094,17:52:38,124,0,1,1.043

298125,17:52:38,124,0,1,1.043

298141,17:52:38,124,0,1,1.043

298172,17:52:38,124,0,1,1.043

298188,17:52:38,124,0,1,1.043

298219,17:52:38,124,0,1,1.043

298235,17:52:38,124,0,1,1.043

298266,17:52:38,124,0,1,1.043

298281,17:52:38,124,0,1,1.042

298313,17:52:38,124,0,1,1.042

298328,17:52:38,124,0,1,1.042

298360,17:52:38,124,0,1,1.042

298375,17:52:38,124,0,1,1.040

298406,17:52:38,124,0,1,1.040

298422,17:52:38,124,0,1,1.040

298453,17:52:38,124,0,1,1.038

298469,17:52:38,124,0,1,1.038

298500,17:52:38,124,1,1,1.037

298516,17:52:38,124,1,1,1.037

298547,17:52:38,124,1,1,2.224

298563,17:52:38,124,1,1,2.224

298594,17:52:38,124,1,1,3.259

298610,17:52:38,124,1,1,2.266

298641,17:52:38,124,1,1,1.037

298656,17:52:38,124,1,1,1.037

298688,17:52:38,124,1,1,0.878

298703,17:52:38,124,1,1,0.878

298735,17:52:38,124,1,1,0.880

298750,17:52:38,124,1,1,0.880

298781,17:52:39,124,0,1,0.880

298797,17:52:39,124,0,1,0.878

298828,17:52:39,124,0,1,0.877

298844,17:52:39,124,0,1,0.877

298875,17:52:39,124,0,1,0.875

298891,17:52:39,124,0,1,0.875

298922,17:52:39,124,0,1,0.874

298938,17:52:39,124,0,1,0.874

298969,17:52:39,123,0,1,0.874

298985,17:52:39,123,0,1,0.872

299016,17:52:39,123,0,1,0.872

299031,17:52:39,123,0,1,0.872

299063,17:52:39,123,0,1,0.872

299078,17:52:39,123,0,1,0.874

299110,17:52:39,123,0,1,0.874

299125,17:52:39,123,0,1,0.874

299156,17:52:39,123,0,1,0.874

299172,17:52:39,123,0,1,0.875

299203,17:52:39,123,0,1,0.877

299219,17:52:39,123,0,1,0.877

299250,17:52:39,123,0,1,0.877

299266,17:52:39,123,1,1,0.877

299297,17:52:39,123,1,1,0.875

299313,17:52:39,123,1,1,1.586

299344,17:52:39,123,1,1,1.510

299360,17:52:39,123,1,1,1.189

299391,17:52:39,123,1,1,1.189

299406,17:52:39,123,1,1,0.973

299438,17:52:39,123,1,1,0.955

299453,17:52:39,123,1,1,0.955

299485,17:52:39,123,1,1,0.992

299500,17:52:39,123,1,1,1.003

299531,17:52:39,123,1,1,0.992

299547,17:52:39,123,1,1,0.986

299578,17:52:39,123,1,1,0.986

299594,17:52:39,123,1,1,0.992

299625,17:52:39,123,1,1,1.002

299641,17:52:39,123,1,1,1.008

299672,17:52:39,123,1,1,1.008

299688,17:52:39,123,1,1,1.010

299719,17:52:39,122,1,1,1.008

299735,17:52:39,122,1,1,1.008

299766,17:52:39,122,1,1,1.008

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What's interesting is in both cases (I bounced my landing) the peak Gs don't seem to occur until about 50-75ms after FS detects we're on the ground.

Hmmm. So if you want the peak I'd need to keep changing the offset when on ground until it decreases, leaving the hiughest value I saw?

I'll try an FSX run, assuming I can do this with an unregistered FSUIPC4. (I only have FSUIPC3 registered)

Lua facilities, like Macros and assignments, need a registered copy. Sorry. Show me your Lua program (to save me time) and I'll run it here when I get a chance.

Regards

Pete

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... I'd need to keep changing the offset when on ground until it decreases, leaving the highest value I saw?

I've implemented this now for you to try. If you please download these updated versions:

http://fsuipc.simflight.com/beta/FSUIPC3908.zip

http://fsuipc.simflight.com/beta/FSUIPC4508.zip

and let me know if these work for you, both in FS9 and FSX.

Regards

Pete

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  • 2 weeks later...
and let me know if these work for you, both in FS9 and FSX.

Sorry I have not gotten back to you sooner, Pete. It's been chaotic here. The FS9 implementation certainly works "correctly" in 3.908, and I think the FSX does. My memory is giving out.

Cheers!

Luke

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