F-16 fly by wire stall scenarios
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it is always a bit disapointing to see people refering to some public simplified information like Code One magazine when BMS provides much more detailed explanations
i wonder if people have read our articles ?
You bet we (some) do. And looking forward for the sequel “The Dark Side of the F18 - FLCS” ::D
Honestly, the articles on the FM are highly valued for many, since they are the proof that we are “flying” something really close to the real thing. And they are quite unique to BMS (and highly missed in other simulators which claim high fidelity or even professional flight models… )
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Another dumb question, Is it PRACTICAL to develop a version of the flight model with all the limiters off so that we can jerk around and appreciate what the flcs is doing for us more? (or an interface that let’s as switch on/off limiters).
Also, why wasn’t a g limiter included in the real bird? There must be a sophisticated reason I guess. I t would help a lot us “over loaders” though
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You can just latch MPO -> ON and have at it…but you’ll still have the AOA limiter active, I think…however, you may be able to generate some pitch rates that could break it that way - I haven’t tried that, could be interesting.
Really effective G limiters are difficult, as the limit depends on both GWT and configuration - the problem with measuring GWT is measuring fuel quantity accurately. And making an accurate entry for OWE…between the two there’s always some slop…er…slosh…er…error. So a G limiter can help, but not always “save” and one shouldn’t rely solely on them as a ROT.
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@Master:
Another dumb question, Is it PRACTICAL to develop a version of the flight model with all the limiters off so that we can jerk around and appreciate what the flcs is doing for us more? (or an interface that let’s as switch on/off limiters).
Also, why wasn’t a g limiter included in the real bird? There must be a sophisticated reason I guess. I t would help a lot us “over loaders” though
There is a g limiter in the real aircraft… There is just not one that takes into account stores limitations. I think the super hornet FLCS does take that into account though?
When the F-16 was first developed, they were not even sure if they could make the flight computer work, let alone give it all these complicating factors.
I think it should be quite possible to make an F-16 in BMS which doesnt have a flight computer. The A-10 uses the NFBW module, surely you could make an F-16 version with the same aero data using the NFBW module?
Dont think it would be difficult. It would be hilarious to see folks trying to fly it though.
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You can just latch MPO -> ON and have at it…but you’ll still have the AOA limiter active, I think…however, you may be able to generate some pitch rates that could break it that way - I haven’t tried that, could be interesting.
Really effective G limiters are difficult, as the limit depends on both GWT and configuration - the problem with measuring GWT is measuring fuel quantity accurately. And making an accurate entry for OWE…between the two there’s always some slop…er…slosh…er…error. So a G limiter can help, but not always “save” and one shouldn’t rely solely on them as a ROT.
You will manage nothing with MPO
MPO activates Wow gain only above 29 deg AOA which means you can’t activate it unless in deep stall .
MPO désactivâtes negGlimiter in all cases though so you can easily trigger negG departures
That’s why MPO is spring mounted because it would be dangerous for negGdeparture to fly it “on”
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There is a g limiter in the real aircraft… There is just not one that takes into account stores limitations. I think the super hornet FLCS does take that into account though?
When the F-16 was first developed, they were not even sure if they could make the flight computer work, let alone give it all these complicating factors.
I think it should be quite possible to make an F-16 in BMS which doesnt have a flight computer. The A-10 uses the NFBW module, surely you could make an F-16 version with the same aero data using the NFBW module?
Dont think it would be difficult. It would be hilarious to see folks trying to fly it though.
It’s a 1 line of code to désactivate the FLCS but it’s totally pointless
F16 is totally unstable even at low AOA there is no static stability margin
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Is that line of code in a config file? I mean, can you modify your ACData file to demonstrate it? It would be pointless, but Id love to see someone try to fly it Maybe someone who complains about how limiters are not useful and hinder using the aircraft effectively…
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F16 is totally unstable even at low AOA there is no static stability margin
Makes me think about a nice failure implementation
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The failure being that all 4 FLCS computers suddenly changed their control laws?
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Makes me think about a nice failure implementation
already implemented in BMS 4.33
When FLCS fault, the FLCS switched in SANDBY GAIN , like the real
that means your FLCS is staying in a standard “gain situation” which is visible when flying different speed and altitudes then, the aircraft responds differently
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You will manage nothing with MPO
MPO activates Wow gain only above 29 deg AOA which means you can’t activate it unless in deep stall .
MPO désactivâtes negGlimiter in all cases though so you can easily trigger negG departures
That’s why MPO is spring mounted because it would be dangerous for negGdeparture to fly it “on”
I thought if you were playing with a keyboard you could command MPO ON/OFF by toggle command?
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Makes me think about a nice failure implementation
…one channel at a time, and in accord with damage/collateral/aggravating failures. Would be very nice indeed.
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already implemented in BMS 4.33
When FLCS fault, the FLCS switched in SANDBY GAIN , like the real
that means your FLCS is staying in a standard “gain situation” which is visible when flying different speed and altitudes then, the aircraft responds differently
I got smacked the other day by SA-14 and got FLCS fault. I pressed switch FLCS reset and fault light went away. Did anything change by disappearing fault?
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Because in the FLCS of the F16, a pilot positive G request is written in negative value.
For instance, if you are flying 45deg no stick input
the G’s feedback is feeding the elevator PI with cos(45) - 1 = -0.707 , which equivalent to the pilot stick input asking 0.of 0.707 , so PITCH UP
During the pitch up, the pitch RATE is growing, for instance i dont know +2 deg/s
the Pitchrate loop is therefore injectiing + 2 * 0.334 = 0.67 on top in the eelevator PI
In total, the elevator PI without stick inpu is therfore : 0.67 - 0.707 = -0.037 , that means equivalent to a pilot 0.037 pitch up request.
As you can see the pitchrate loop is slowing down the process. This is why when the G feedback loop is feeding very small values to pitch up, the pichrate building up conterbalance havily this command
So when a positive pitch feedback in added, it counters the pitchRATE.
This is obvious by the way, a FEEDBACK loop is designed to counteract the source of the perturbation.
and i am not talking about the other branches acting in the same time if AOA > 15 for instance.
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As you can imagine, the FLCS is not “just” limiters…it’s a whole paquet of spagetthi and this needs deep study to understand all of it
sorry i should be clearer in my explanations, but i am so used to it…
OK, when we say “command 1g” we really mean “1g if pitch rate is 0.” If pitch rate is not 0 then all bets are off. Pitch rate feedback has dampening effect (nose up rate adds virtual nose down command, partial and vice versa).
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if you read FLCS article available in the article section of benchmarksim site, you will have much more information about the deep stall and FLCS behavior
https://www.benchmarksims.org/forum/attachment.php?attachmentid=1963&d=1267814283
it is always a bit disapointing to see people refering to some public simplified information like Code One magazine when BMS provides much more detailed explanations
i wonder if people have read our articles ?
I remember reading this article when it was first published. it is SUCH a good summary that IMHO it is required reading if you want to understand the WHY of a deep stall. Simply excellent document.
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IMO, required reading if you want to fly BMS… would save us all a lot of explanation time when folks ask about why the aircraft flies in a certain fashion.
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It’s a 1 line of code to désactivate the FLCS but it’s totally pointless
F16 is totally unstable even at low AOA there is no static stability margin
Can you show a gameplay example or maybe a code offset in the binary? It’s interesting in itself, despite FLCS being there for a reason. Maybe we can appreciate the concept of negative static stability, in a way.