I love the BMS flight model
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@frapes45 said in I love the BMS flight model:
@Mav-jp cos (phi) ? Isnt φ the roll axis?
It would be very interesting if it actually accounts for roll angle.
Okay please read nasa TP1538
https://www.cs.odu.edu/~mln/ltrs-pdfs/NASA-79-tp1538.pdfPage 2 , définition of An
And page 37 appendix B which gives you how this is computed
As you can see it takes both pitch and roll angles into account (with accelerations on all axis for dynamic )
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@Mav-jp not only that, An is also dependant on pitch acceleration among other things
φ is the euler angle for roll.
It is also not as simple as Z axis reading 0g as you mentioned initially.
Dont want to sound rude or insulting at all.
I will keep looking. Obviousely I am not in a position to know if and how the bms flcs is precision engineered.
Kind regards
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@frapes45 said in I love the BMS flight model:
@Mav-jp not only that, An is also dependant on pitch acceleration among other things
φ is the euler angle for roll.
It is also not as simple as Z axis reading 0g as you mentioned initially.
Dont want to sound rude or insulting at all.
I will keep looking. Obviousely I am not in a position to know if and how the bms flcs is precision engineered.
Kind regards
Thank you I think I know what the Euler angles are
BMS flight models includes An that is described in the nasa TP1538 , including all rates p,q and Wdot
My comments earlier was a simplified approach to make you understand the effect of pitch and bank on the flcs response which explains why the FLCS commands pitch up when banked at 90deg
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@frapes45 said in I love the BMS flight model:
@Mav-jp not only that, An is also dependant on pitch acceleration among other things
φ is the euler angle for roll.
It is also not as simple as Z axis reading 0g as you mentioned initially.
Dont want to sound rude or insulting at all.
I will keep looking. Obviousely I am not in a position to know if and how the bms flcs is precision engineered.
Kind regards
BMs flcs is not engineered, it’s a copy paste of the real
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@Mav-jp me so sorry for starting this all
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@Mav-jp said in I love the BMS flight model:
BMS flight models includes An that is described in the nasa TP1538 , including all rates p,q and Wdot
My comments earlier was a simplified approach to make you understand the effect of pitch and bank on the flcs response which explains why the FLCS commands pitch up when banked at 90deg
Yes, I understand.
A lot of interest lies on pages 99-104 on the document showing how An varies accordingly to the euler angles in diagrams when various maneuvers are perfomed including 70 to 70 degree bank to bank. It would be nice if we could compare that data to the BMS flight model for FM evaluation.
At first glance there is no change on θ even with An changing to positive number. That means the plane will not turn by the computer and it would not require to push down the stick
There is my proof that something is going wrong with bms when banking
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@frapes45 said in I love the BMS flight model:
@Mav-jp said in I love the BMS flight model:
BMS flight models includes An that is described in the nasa TP1538 , including all rates p,q and Wdot
My comments earlier was a simplified approach to make you understand the effect of pitch and bank on the flcs response which explains why the FLCS commands pitch up when banked at 90deg
Yes, I understand.
A lot of interest lies on pages 99-104 on the document showing how An varies accordingly to the euler angles in diagrams when various maneuvers are perfomed including 70 to 70 degree bank to bank. It would be nice if we could compare that data to the BMS flight model for FM evaluation.
At first glance there is no change on θ even with An changing to positive number. That means the plane will not turn by the computer and it would not require to push down the stick
There is my proof that something is going wrong with bms when banking
You do realize that BMS IS the NASA model right ?
Nothing , absolutly nothing can compensate the An commanded feedback in the flcs
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By the way long time ago I flew with cos(phi) inhibited in the FLCS for testing purpose , it’s very very weirdo
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@Mav-jp said in I love the BMS flight model:
By the way long time ago I flew with cos(phi) inhibited in the FLCS for testing purpose , it’s very very weirdo
xD So its not inhibited as of now?
I thought bms follows the nasa model…
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@Mav-jp said in I love the BMS flight model:
it’s very very weirdo
And you are judging based on how many flight hours ?
Please look the pages I mentioned.
Look for the bank to bank diagram.
θ angle remains the same no matter what bank angle you are at. ( 70 to 70 degrees)
I doubt thats the case on bms as of now.
BTW No hard feelings…
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@frapes45 said in I love the BMS flight model:
@Mav-jp said in I love the BMS flight model:
it’s very very weirdo
And you are judging based on how many flight hours ?
Please look the pages I mentioned.
Look for the bank to bank diagram.
θ angle remains the same no matter what bank angle you are at.
I doubt thats the case on bms as of now.
BTW No hard feelings…
As a matter of fact, maybe you should have a look of what phi theta and psi means , because it seems you are a bit confused on the matter (BTW no hard feelings…)
In the NASA document the euler angles are the angle of the aircraft versus the fix referential of earth.
Phi is roll
theta is angle from horizontal
Psi is angle headingExample of description here:
https://en.wikipedia.org/wiki/Euler_angles#/media/File:Plane_with_ENU_embedded_axes.svg
So , in the manoeuver bank to bank, illustrated Figure 56
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theta stays stable as airracft is not really pitchin up or down compared to horizon
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what you need to look at is PSI angle which reveals the heading motions :
AS you can see, lets analyse first bank , the pilot is executing the first bank from +5 seconds to 15 seconds.
Phi angle is maximum at around 12.5 seconds and stays there until around 15 seconds
Pay attention that during this period FLongN is a bit positive which means the pilot still gives some input therefore the analysis will be biaised
During this time, the PSI angle (heading) has built up to 50 degrees deviation,
you can also see that the pitch rate (q) is also building up while rolling, which is due to both FLCS commanding pitch , pilot input AND inertia coupling
As a matter of fact, this test has been performed in order to test the Roll limiters systems (A , B, C ) and to measure their resistance on the inertia coupling during those manoeuvers
So , your “proof” is actually only a proof that you misinterpreted the meaning of theta angle.
as this test is performed with pilot stick input, we cannot demonstrate really anything on the matter.
the only thing we know is that the FLCS commands 1G pitch up all the time, and particularly when rolled at 90 deg, which provokes heading deviation
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When you look at the knife edge pass :
you can see in the HUD the G meter is readin close to 0
In order to achieve 0G in the F16 there is only ONE WAY : to push on the stick , the FLCS does NOT command 0G when banking, the FLCS of the F16 ALWAYS commands 1G with no pilot input, no matter what.
That’s a basics of the F16 FLCS, now you are entirely free to not accept this fact, but there is nothing more i can tell you to explain.
I’m out
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the FLCS of the F16 ALWAYS commands 1G with no pilot input, no matter what.
This statement is very absolute and so not true. You said it yourself An commands the FLCS not the G force.
It seeks 1G it doesnt mean it always commands 1G.
The hud G reading is only indicative and its absolutele normal for it to show values near 0 when banking with such sharpness.
I am telling you its not the same on real viper simulator I have tried myself. Feel also free to believe what you want.
Also you falsely claim that ψ is the true indicator of heading change when banked.
This is completely wrong. If that was the case we should see 50 degrees heading deviation when banking 70 degrees according to the chart…As of now it changes way to much heading when banking
Does GCAS also command 1g lol
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@Mav-jp said in I love the BMS flight model:
what you need to look at is PSI angle which reveals the heading motions :
I am sorry but that statement is totaly incorrect.
Ψ angle when banked at 70 degrees doesnt show heading change at most. It mostly shows you are heading either towards the sky or the ground.
It seems you have difficulty understanding the dynamic of the euler angles. When banked 90 degrees θ will show you if yοu change heading not ψ
You also seem to base your theory on the hud feeding g sensor which is seperate and different in location than the one FLCS uses.
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@frapes45 said in I love the BMS flight model:
@Mav-jp said in I love the BMS flight model:
what you need to look at is PSI angle which reveals the heading motions :
I am sorry but that statement is totaly incorrect.
Ψ angle when banked at 70 degrees doesnt show heading change at most. It mostly shows you are heading either towards the sky or the ground.
It seems you have difficulty understanding the dynamic of the euler angles. When banked 90 degrees θ will show you if yοu change heading not ψ
You also seem to base your theory on the hud feeding g sensor which is seperate and different in location than the one FLCS uses.
i feel ashame for you now , sorry.
have a good time
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@Mav-jp cmon man. No need to fight.
Instead, i suggest we focus on getting to the bottom of this.
Perhaps I can setup a way to measure the angles and save them to a text file so I would be able to chart them and see how close to the diagrams bms is.
I need to study tp1538 more to know all the exact parameters.
I will keep looking.
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said in
Pay attention that during this period FLongN is a bit positive which means the pilot still gives some input therefore the analysis will be biaised
During this time, the PSI angle (heading) has built up to 50 degrees deviation,
you can also see that the pitch rate (q) is also building up while rolling, which is due to both FLCS commanding pitch , pilot input AND inertia coupling
As a matter of fact, this test has been performed in order to test the Roll limiters systems (A , B, C ) and to measure their resistance on the inertia coupling during those manoeuvers
So , your “proof” is actually only a proof that you misinterpreted the meaning of theta angle.
as this test is performed with pilot stick input, we cannot demonstrate really anything on the matter.
the only thing we know is that the FLCS commands 1G pitch up all the time, and particularly when rolled at 90 deg, which provokes heading deviation
I have been further studying tp1538…
I have reached some conclusions.
First of all, Do you even realize that TP1538 uses aerodynamic data derived from a wind tunnel testing of a scaled down model?’
To add to this, the report is dated from 1979, so old that from then till today there have been numerous updates to F16 FLCS in different blocks. Not to mention that the study uses three different control systems we are not even sure if they are actually exactly the same as the ones used by the real aircraft ( we only assume that control system A mentioned might be the type that the Viper uses) the report is also only valid to mach 0.6 and the alpha is limited but that is of little concern.
That means we are actually discussing approximations…
However, if we put all this aside. we can still perhaps reach some possible conclusions.
Concerning Bank to Bank task mentioned in the document.
You support that Flong is positive (data is biased)
I partly agree, but that means that he actually pulls the stick not that he pushes. Also if you look at the key moments of interest, for example at the 8-10 sec, the exact moment test reaches 70 degrees of bank Flong is near 0… ( Figure 56, Page 198 or 202 in PDF’s numbering)
What is also more important is δhor which doesn’t seem to change very much besides negligible fluctuations of little importance. That means FLCS is actually still keeping the plane stable and is partly ignoring Pilot input
Now, if you understand that θ (Thi) is the true indication of heading change when an aircraft is banked, I am sure you will arrive at a revelation…
As a matter of fact, I am in the process of making a BMS evaluation data chart recording, to compare the results.
It is difficult though as TacView has limited telemetry data and I am still at the process of figuring this out.I ignore all the insults you have mentioned, for the scope of perhaps achieving a better flight model. Actually I have learned a lot from this and I actually thank you
PS: next week I will have again the chance to visit the Lockheed Martin simulator. I am sure I can make a video of myself attempting knife edge. Are you interested at all?
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@frapes45 said in I love the BMS flight model:
@Mav-jp said in I love the BMS flight model:
Pay attention that during this period FLongN is a bit positive which means the pilot still gives some input therefore the analysis will be biaised
During this time, the PSI angle (heading) has built up to 50 degrees deviation,
you can also see that the pitch rate (q) is also building up while rolling, which is due to both FLCS commanding pitch , pilot input AND inertia coupling
As a matter of fact, this test has been performed in order to test the Roll limiters systems (A , B, C ) and to measure their resistance on the inertia coupling during those manoeuvers
So , your “proof” is actually only a proof that you misinterpreted the meaning of theta angle.
as this test is performed with pilot stick input, we cannot demonstrate really anything on the matter.
the only thing we know is that the FLCS commands 1G pitch up all the time, and particularly when rolled at 90 deg, which provokes heading deviation
I have been further studying tp1538…
I have reached some conclusions.
First of all, Do you even realize that TP1538 uses aerodynamic data derived from a wind tunnel testing of a scaled down model?’
To add to this, the report is dated from 1979, so old that from then till today there have been numerous updates to F16 FLCS in different blocks. Not to mention that the study uses three different control systems we are not even sure if they are actually exactly the same as the ones used by the real aircraft ( we only assume that control system A mentioned might be the type that the Viper uses) the report is also only valid to mach 0.6 and the alpha is limited but that is of little concern.
That means we are actually discussing approximations…
However, if we put all this aside. we can still perhaps reach some possible conclusions.
Concerning Bank to Bank task mentioned in the document.
You support that Flat is positive (data is biased)
I partly agree, but that means that he actually pulls the stick not that he pushes. Also if you look at the key moments of interest, for example at the 8-10 sec, the exact moment test reaches 70 degrees of bank Flat is near 0… ( Figure 56, Page 198 or 202 in PDF’s numbering)
What is also more important is δhor which doesn’t seem to change very much besides negligible fluctuations of little importance. That means FLCS is actually still keeping the plane stable and is partly ignoring Pilot input
Now, if you understand that θ (Thi) is the true indication of heading change when an aircraft is banked, I am sure you will arrive at a revelation…
As a matter of fact, I am in the process of making a BMS evaluation data chart recording, to compare the results.
It is difficult though as TacView has limited telemetry data and I am still at the process of figuring this out.I ignore all the insults you have mentioned, for the scope of perhaps achieving a better flight model. Actually I have learned a lot from this and I actually thank you!@Mav-jp
PS: next week I will have again the chance to visit the Lockheed Martin simulator. I am sure I can make a video of myself attempting knife edge. Are you interested at all?
First : BMs does not use tp1538 flcs but the real loockeed Martin one . Should you read my articles you would know .
Second : your interpretation of Euler angles is wrong therefore all your so called “analysis” are wrong.
Psi represents heading from a fixed referential (earth) . Phi angle does not change the convention because aerospace Euler convention uses 3-2-1 convention as explained here
So Nasa document uses 3-2-1 convention , Psi always represents the azimuth of the aircraft therefore during bank to bank the heading variation is around 50 degrés
You are confusing bank , elevation , azimuth used in Nasa document a with roll , pitch , yaw
That’s a fact , period
The FlongN is significant during the manoeuver because the pilot has been instructed to keep level flight as demonstrated by theta staying null.
Because the lift cos (phi) not compensating the gravity anymore he had to pull to maintain altitude
Deltah variation is small because at those speeds only a few degrees are necessary to act effictiently. At those speeds you can’t therefore analysis deltah to draw conclusion especially when deltah is commanded by muliple input including pilots input , normal force feedback , aoa feedback and aoa limiter
Now i understand I can’t convince you about your mistakes so there is no need to continue discussion.
As I know my temper pretty well and for the sake of politeness toward you and the other readers , I’m blocking you so I don’t have to read you again.
Thank you for your understanding
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@Mav-jp Sorry pal,
Even If my euler angle understanding is wrong… which is not,
the bank to bank data you keep bringing as proof isnt even a knife edge maneuver… to begin with.I am offering to make a video recording of me flying the real sim next week. I will attempt knife edge without any pitch input and bring this as proof.
Personally, I know what the correct behavior is and what is not as I have witnessed it myself…
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said in
bank to bank the heading variation is around 50 degrés
Wow do you really believe this?
I mean 50 degrees 50
no plane on earth changes 50 degrees of heading when banking 70 degrees on a matter of 3 sec… with stick longitudinal input virtually being near 0