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Chuck_Owl
Oct-27-2014, 16:43
We had an interesting conversation about flight models in BoS in a topic that is unfortunately locked. I'm creating this one, but PLEASE: BEHAVE.

Long story short, we wondered if this FM behaviour was "realistic" or not.

https://www.youtube.com/watch?v=-qSuPW24wco

https://www.youtube.com/watch?v=-qSuPW24wco

Well, some folks on the BoS forums wondered the same thing as well. VIKS, a member of 777 dev team, decided to try this very same manoeuver in DCS. The result is quite interesting.

https://www.youtube.com/watch?v=LYFffkW2kBw&feature=youtu.be&list=UUhvs3FK_9UvE7fPaXW5euVA

https://www.youtube.com/watch?v=LYFffkW2kBw&feature=youtu.be&list=UUhvs3FK_9UvE7fPaXW5euVA
https://www.youtube.com/watch?v=Kt2FDPB33TY&feature=youtu.be&list=UUhvs3FK_9UvE7fPaXW5euVA

https://www.youtube.com/watch?v=Kt2FDPB33TY&feature=youtu.be&list=UUhvs3FK_9UvE7fPaXW5euVA

I wasn't quite sure this was possible, but apparently both DCS and BoS show that this weird roll on takeoff and looping at low speed is, in fact, possible. Whether or not that would be true in real life, I couldn't tell. Not unless I could come up with numbers that prove that you cannot do this with these aircraft at any configuration.

Thoughts?

Personally, it brought a sly grin to my face. :D I'm not sure what to think anymore.

Original topic:
http://forum.il2sturmovik.com/topic/12078-whats-bf-109-fm/

Combat Wombat
Oct-27-2014, 17:09
Anyone who fly's/flies in the real world knows this would not be possible Unless using something from the redbull garage and no way would a ww2 fighter come anywhere near that !~ Just think back to any air show you have attended with warbirds and picture that happening ? it's not going to or be possible..

Chuck_Owl
Oct-27-2014, 17:15
I'm pretty sure it's just too dangerous to test IRL, especially with these rare birds. We might never know unless someone really did it with one of these aircraft and lived to tell the tale.

LuseKofte
Oct-27-2014, 17:21
I cannot do this in DCS either, but someone can

Takeoff weight is 3830 kg

https://www.youtube.com/watch?v=Kt2FDPB33TY&feature=youtu.be&list=UUhvs3FK_9UvE7fPaXW5euVA

Takeoff weight is 3339 kg

https://www.youtube.com/watch?v=LYFffkW2kBw&feature=youtu.be&list=UUhvs3FK_9UvE7fPaXW5euVA

ATAG_Headshot
Oct-27-2014, 17:35
I was at an airshow which had a Harvard flight display. Earlier in the show an F-18 did a roll right off of takeoff, and the Harvard pilot decided to show him up. The Harvard did a snap roll immediately after leaving the ground, and low enough that his wing almost hit the runway. The Harvard is a training aircraft and isn't armed and armoured, but it was possible. As for the loop I really have no idea.

LuseKofte
Oct-27-2014, 17:47
14 minutes out

https://www.youtube.com/watch?v=h1qSzCnzXvY

I think I check out, I admit I have no clue and I thought I had. I have watched similar crazy stuff all day. I surrender, it is quite impossible to say wether something can be done or not

gavagai
Oct-27-2014, 18:08
When I tried to do it with the Fw 190D-9 I used 100% fuel and 100% ammo. I'm not surprised Viks had to lose almost 400kg from the loaded mass in order to pull it off.

P.S. 3830kg = full ammo with 10% fuel. (190)

and 3339 is not even possible for the P-51D, only the TF-51D.

DUI
Oct-27-2014, 18:50
The more often I look at those videos the more I think about whether my very first feeling ("this is absolutely impossible!") was correct.

But then I see this video of a Heinkel and be instantely assured: There is something very much messed up with the FM in BoS:


http://www.youtube.com/watch?v=Z0HgbMuUBSo#t=26

Not necessarily to say that the FM of DCS is better in this aspect. Nor do I know how the planes in TFCliffs perform in such a situation. Did someone already try?

P.S. The Heinkel video is supposed to be recorded with full-real settings. In the BoS forum this behaviour was already confirmed by a couple of guys, one of them totally trustworthy to me. They said to have tested it without bomb load and about 10% fuel. You can read the details in this already closed thread (http://forum.il2sturmovik.com/topic/12227-hows-possible/).

Chuck_Owl
Oct-27-2014, 18:53
When I tried to do it with the Fw 190D-9 I used 100% fuel and 100% ammo. I'm not surprised Viks had to lose almost 400kg from the loaded mass in order to pull it off.

P.S. 3830kg = full ammo with 10% fuel. (190)

and 3339 is not even possible for the P-51D, only the TF-51D.

This makes sense in a way. The TF-51D doesn't have weapons to carry as it is a recon variant.

Interesting. I tried myself to achieve these takeoff rolls at realistic fuel loads and failed. It is, possible, like Gavagai said, that it can be achieved at 10 % fuel load.

@DUI: I recommend your friend tries the same manoeuver with a fully loaded He-111. He's gonna see a pretty big difference. Fully loaded, the He-111 has about 3500 litres worth of fuel.

I know the Blenheim has some funky aerodynamics sometimes... but not when loaded for a bomb run.

gavagai
Oct-27-2014, 19:20
Yes, I think this is really about people doing wacky stuff with minimum fuel loads. I'm going to bet the 109F and He-111 videos were also made with 10% fuel loads, or something similar.

ZG15_robtek
Oct-27-2014, 19:25
Not to be nitpicking, but the stang and the 190 did have to pick up some speed before the loop.
also the weight /trust ratio might differ from the f4.
Too late for me to calculate now.

Chuck_Owl
Oct-27-2014, 19:32
Most jets have usually much higher Thrust-to-weight ratios in comparison to prop planes anyway. However, that's not always the case for very heavy jets. The Concorde had a T-2-W of about 0.375 according to wikipedia. Most modern combat jets have something around 1.

Kwiatek
Oct-27-2014, 19:36
14 minutes out

https://www.youtube.com/watch?v=h1qSzCnzXvY

I think I check out, I admit I have no clue and I thought I had. I have watched similar crazy stuff all day. I surrender, it is quite impossible to say wether something can be done or not

As you see these Beechcraft 18 pilot after take off make long run above the runway increasing speed then make high pitch up barell roll. Look how he loose alt making such roll - even if it is much smaller and lighter plane then for e.x He111.

Wonder what power have these engines?

Im sure real He111 cant do the same things which could do BOS He111. If He111 would start to make roll imidietly after take off it would surly crashed in the ground. Such big wings heave plane cant make straight roll even with higher speed. He would loose alt and speed a lot in such manuover.




Regarding videos made by Viks from DCS:


D-9 : take off weight - 3830 kg. power ( i suppose MW50 enabled) - 2100 HP - P/W - 0,54 HP/KG


- roll start at 230 kph, loop start at 300 kph - i suppose it is quite probaby it could be done IRL


P-51: take off weight - 3339 kg, power ( 67 inch i suppose) - 1600 HP - P/W - 0,47 HP/KG


- roll start at 205 kph , loop start at 320 kph - P-51 had worse P/W then D-9 so i suppose its need more speed entry to do a loop, dunno about roll casue 205 kph seemed very low to me, wonder what was stall speed of these P-51 type.

DUI
Oct-27-2014, 19:44
@DUI: I recommend your friend tries the same manoeuver with a fully loaded He-111. He's gonna see a pretty big difference. Fully loaded, the He-111 has about 3500 litres worth of fuel.

Still, my gut feeling (I cannot contribute more to this topic) tells me that manoeuvers like that should not be possible at all in a Heinkel - especially, if it just took off. I simply can't imagine that a Heinkel that returned from its sortie with low fuel was able to perform such manouvers. How should such a WW2 bomber have been able to perform a perfect loop with an entry speed of only about 200-250 km/h (right after the roll manoeuver)...

Of course, such situations with extreme conditions are not really relevant in normal flight. But that they are possible tells me that there is something wrong in the FM. Something that probably also affects more-standard manoeuvers to some degree.

1lokos
Oct-27-2014, 19:52
I did similar thing in CloD, Bf 109 E3 with 100l fuel.
The roll is not problem - @ >190KMH, but the looping don't end very straight. Probable someone used do Clod Bf 109 do better. :D

Sokol1

Kwiatek
Oct-27-2014, 19:57
I did similar thing in CloD, Bf 109 E3 with 100l fuel.
The roll is not problem - @ >190KMH, but the looping don't end very straight. Probable someone used do Clod Bf 109 do better. :D

Sokol1

Well 109 E-3 got quite low stall speed - with such fuel load about 110-120 kph - so quite probably to make roll at 190 kph with full power ( expecially with small wings plane with good roll rate - good power to weight ratio and good roll rate (small short wings) dont casue drop too much speed in straight roll )).

What entry speed for loop?

Wonder what could do He-111 in CLOD :P

gavagai
Oct-27-2014, 20:24
I just tried an empty He 111 with 10% fuel in Cliffs. No way can I barrel roll it at low altitude like the BoS video. Roll rates have always been too snappy and efficient with 777's FMs though.

LuseKofte
Oct-28-2014, 02:56
I cannot do it in BOS, so I do not know , I guess this is done with the simplified fm. There are just nowhere in hell I can get even close to that.

VO101_Tom
Oct-28-2014, 06:23
The video what Dui posted is not simplified FM! Sadly.
Some guy on hungarian forums claimed too, that this video is BS, fake, because He can not repeat it... it must be easy settings, or something other cheat...
So i had to try flying the same (expert settings of course, so there is no external view).
Please note, I airborne little earlier and gain speed, but the guy take off later, they run at full speed till the end of RWY. I started the maneuvers only little later. The speed difference can not be too much, but If my speed is higher than His, it's only worsening the case. Which mean that you don't need even a 250 kph IAS for this maneuvers...

The key is the stall. Pull the stick full back, kick the rudder and full aileron. When the plane in invert pos, push the stick full forward. It will stabilize the invert flight, then you can finish the rolling. Other weird thing that the bomber is able to fly a nicer and much easier looping than a LaGG-3... Needless to say, the RL planes don't behave this way, especially an 9-10 tons bomber with 0,082 kW/kg power/mass ratio...


https://www.youtube.com/watch?v=AoDQ54UXARg
(It's me, just my nick in BoS is different)

Hood
Oct-28-2014, 06:34
I just tried an empty He 111 with 10% fuel in Cliffs. No way can I barrel roll it at low altitude like the BoS video. Roll rates have always been too snappy and efficient with 777's FMs though.



https://www.youtube.com/watch?v=y8-96ayyQcg#t=75


I'd love to know the entry speeds into all of these manoeuvres. Someone (Viks maybe) suggested >300km/h.

Funnily enough I can't see anyone spamming the DCS or CLOD forums about their FMs. I think it's sensible not to.

Hood

ps I also like that JW is now biting back.

LuseKofte
Oct-28-2014, 06:48
I flown the 111 in bos a lot, it perform very well and simulate the lightness after bomb drop great, you got this famous bounce upward that is very well described in many books and interviews. I am puzzled this can be done, but it is still not a killer for me. I find the BOS 111 in many ways more authentic and in other ways less. I feel they have simplified the engine settings because people over revved it too often.
It is how you look at it

ZG15_robtek
Oct-28-2014, 11:52
Roll rate He111 3s/360 ??????

Combat Wombat
Oct-28-2014, 12:29
I have not got my x-plane installed at the moment So if anyone has the latest x-plane running it sure would be interesting to see what the flight physics thinks about this debate even given the limits of Our computers.

Mysticpuma
Oct-28-2014, 12:46
Apparently fixing the flight models is going to cost customers features, Han just responded:

GOAPotenz, on 28 Oct 2014 - 13:22, said:



So now we can tell that the loop issue that made most of us freak out (me included)

it is not that unbelivable like it sounds at first, and it is in all sims.



I have to be honest, i though that was a huge mistake in the FM's, but now seems

that's not the case.



Great news.



Regs



Potz

Han said:

There are many videos with loops, rolls, emmm... abrakadabras and so on from MSFS on birds like B-747, for example. But I don't think we need to find and post it here. It's all obvious enough even now, I'm think...


ONLY one sad news here - we have spent MANY work time on attempts to proof you that we're developers but not camels.



Now, when someone will ask me: "where my f...n FM feature which I have waited for a long time!?" - than I'll respond - "It's stollen by guys in this thread", and I'll post a link to this thread.



I've told you guys before - we can't proof every digit, we have no time for it. We can only show that we're competent enough to allow you to trust us without re-checking and claiming on every digit.



I've tryed it here:



http://forum.il2stur...claims-respond/



And I and VikS tryed it in this thread. Our engeneers have spent their work time on assisting in proofs.



I'M SURE that after one week someone of you will arise with a new "SUPER-PROBLEM", we again will spent much time on proofs that we're not camels, we WILL have a success, but CUSTOMERS will loose features because we will spent time on these proofs.



Guys, don't you understand that YOU'RE killing the project and genre? No? Think on that, guys.

---------------

:(

The thread:

http://forum.il2sturmovik.com/topic/12078-whats-bf-109-fm/page-6

Otyg
Oct-28-2014, 12:55
i really hope that's a translation thing.. but i dont think so.. im f...ing ashamed to bought the game.. what a bunch of dicks.

Chuck_Owl
Oct-28-2014, 13:05
Yeah, Otyg... you said it.

Gee, we're probably the worst, most terrible human beings that ever lived.

ATAG_Bliss
Oct-28-2014, 13:11
https://www.youtube.com/watch?v=y8-96ayyQcg#t=75


I'd love to know the entry speeds into all of these manoeuvres. Someone (Viks maybe) suggested >300km/h.

Funnily enough I can't see anyone spamming the DCS or CLOD forums about their FMs. I think it's sensible not to.

Hood

ps I also like that JW is now biting back.

That video is the vanilla version of the game. Anyone could change the FM in about 20 seconds to a spitfire if they wanted to. Try the same in the TF version if you are trying to use this as some sort of comparison.

PFT_Endy
Oct-28-2014, 13:11
Funny, Yoyo from ED always seems to find the time to talk about FMs and aerodynamics in various DCS forum threads and doesn't complain it costs features taken away from customers... Better time management I guess.

RAF74_Buzzsaw
Oct-28-2014, 14:48
https://www.youtube.com/watch?v=y8-96ayyQcg#t=75


I'd love to know the entry speeds into all of these manoeuvres. Someone (Viks maybe) suggested >300km/h.

Funnily enough I can't see anyone spamming the DCS or CLOD forums about their FMs. I think it's sensible not to.

Hood

ps I also like that JW is now biting back.

I've had a look at the CoD Heinkels, and their max CL and induced drag in inverted flight is mismodeled... a leftover from the vanilla version which will be fixed next patch we release. They can perform elevator related maneuvers at 10% fuel and no ammo which they should not be able to accomplish. Rollrates are correct.

DUI
Oct-28-2014, 14:56
:thumbsup: :salute:

Chuck_Owl
Oct-28-2014, 14:57
I've had a look at the CoD Heinkels, and their max CL and induced drag in inverted flight is mismodeled... a leftover from the vanilla version which will be fixed next patch we release. They can perform elevator related maneuvers at 10% fuel and no ammo which they should not be able to accomplish. Rollrates are correct.

Out of curiosity, how do you "tweak" a flight model in a video game? I heard that they use lookup tables, but I didn't have the chance to check the game's source code so I can't really tell.

I did code some flight models at university in MatLab, but we only had it coded for a flight without aileron nor rudder input for a Takeoff-Climb-Cruise-Descent-Landing mission.

Something like that
http://www.stpaulairlines.com/spa-training/Images/to_profile.gif

RAF74_Buzzsaw
Oct-28-2014, 15:06
Out of curiosity, how do you "tweak" a flight model in a video game? I heard that they use lookup tables, but I didn't have the chance to check the game's source code so I can't really tell.

I did code some flight models at university in MatLab, but we only had it coded for a flight without aileron nor rudder input for a Takeoff-Climb-Cruise-Descent-Landing mission.

Something like that
http://www.stpaulairlines.com/spa-training/Images/to_profile.gif

Depends on the game. In CoD they have a section in the flight model (.fmd) called "Polares" which manages the aerofoil polars. And of course, many other things... plus there are files for the engine, prop, weapons, damage, etc.

1lokos
Oct-28-2014, 19:55
AI Fw 190 like do this trick:


http://www.youtube.com/watch?v=kGGtHCJePTQ

1C can import CloD Su-26 to BoS, will be nice do aerobatics in this engine. :)

TWC_Target
Oct-28-2014, 20:21
Real life experience. I once lived in western Ohio and as it was farm country it wasn't unusual for some farmers to fly things. From the fan powered parachutes to bi-planes. Its the bi-plane owned by a farmer down the road from me that this story is about. One day I heard the distinct sound of an engine going from the top of it's power band to the bottom. So I went outside to see what was going on, the day was overcast (10/10 as we use for weather reports in the CG) with a low ceiling. I searched towards the area where the engine sound was coming from, at the time it was struggling. I thought I found the place, the land is totally flat so the sound doesn't have anywhere to hide, if you know what I mean. The sound drew my eye to the sky just down the road. Still nothing to see, until the engine seemed to quit its struggle and in a few seconds, as the engine drone said the RPMs were going up, this bi-plane exits the overcast. He's in a dive and as he comes down I'm thinking I'm about to witness a disaster. Just as he gets closer to the ground than I think he should be, he pulls up and climbs back up into the clouds. And does it again, and again, and again. Of course it's a bi-plane so the consecutive loops that I witnessed and those that came before I got outside shouldn't be a great surprise. What mesmerized me was the fact that he was flying half the loops blind. By the time he exited the clouds he had no room for error. I could have thought he actually landed on the bottom of his loops.
I would've thought there was something wrong with his idea of a good idea, but this was an area where some guys thought it was a good idea to take a cutting torch to an empty gas tank. No water, just the tank.

To the thought on the sims abilities? It's a game unencumbered by the facts of gravity, like the guy in the bi-plane must've thought he was.

vranac
Oct-28-2014, 20:34
AI Fw 190 like do this trick:


1C can import CloD Su-26 to BoS, will be nice do aerobatics in this engine. :)

All together with a weapons that Su-26 can carry in CloD :whacky4: