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Great flight model!


Kroll

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  • 3 weeks later...

Awesome!

 

When LoMac came out, I was in love. When Flaming Cliffs came out, I was in love even more. When FC2 came out, I was still as much in love as I could be. When the A-10C came out, I didn't think I could be more in love. Yet I was. (I'm going to run out of adjectives soon!)

 

Then came the Huey. OMG, I thought. I'm in heaven. Even in those first few hours of release, the poor thing just tried to kill itself and me along with it. But I was in love more deeply. Soon BST got the flight dynamics right and I have been flying this angel ever since. (As well as all the other Western aircraft, too! Years ago, I was with the 104th Phoenix and had to qualify by three consecutive carrier traps on the K, in an Su-33. Sorry, guys, but I'm too stupid to learn Russian any more than that. :(

 

The Pony was a dream even when it, too, tried its best to kill me on take-off. Today, I fly with pride in the P-51. (The German birds, well, the Mustang still is my favorite.)

 

The Gazelle is very nice but needs a little bit of work yet. (Just my opinion. Or, I could just be too stupid to fly such a light helo.)

 

But, the reason for this post:

 

The Albatros just has to be God's gift to sim pilots! I am totally blotto in love with her. She's not fast, but I don't care. She's not heavily armed, but I don't care. She's not even particularly pretty like the (upcoming) F-5 or the Eagle. But, in this early release of the L-39, I think I can honestly say, she's my favorite to get into and just fly.

 

Thank you so much, ED. She's gorgeous to fly.

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The Hornet is best at killing things on the ground. Now, if we could just get a GAU-8 in the nose next to the AN/APG-65, a titanium tub around the pilot, and a couple of J-58 engines in the tail...

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Albatros is a great learning tool.

 

Sent from my SM-T231 using Tapatalk

AWAITING ED NEW DAMAGE MODEL IMPLEMENTATION FOR WW2 BIRDS

 

Fat T is above, thin T is below. Long T is faster, Short T is slower. Open triangle is AWACS, closed triangle is your own sensors. Double dash is friendly, Single dash is enemy. Circle is friendly. Strobe is jammer. Strobe to dash is under 35 km. HDD is 7 times range key. Radar to 160 km, IRST to 10 km. Stay low, but never slow.

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In my experiences, the L-39 handles like an airliner as to other jets in DCS. She does not like to slow down or get down all too fast - even with speedbrakes. Takes more precise stick and rudder work during maneuvers. She likes to shake. However, quoting doodenkoff, she "is a hoot" to fly for sure. When I first installed DCS back in 2014, I was sure the most fun would be found dispatching tanks and planes alike to their doom. But in all honestly, I find myself just cruising over Nevada in the A-10C and L-39 more than I find myself in combat missions. The L-39 is a must have. Like WildBillKelsoe said, it's a fantastic learning tool and a genuine joy to fly.

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  • 3 years later...

Earlier I've said (tried to quote myself for an answer and it seems that this forum just deleted that message intead): "And now, something went wrong...! As brilliant as it's FM was and how natural the plane was responding and flying when it came out, just try it now once again and pull the plane around in high alpha and beta to see what I mean! Instead of fixing those with big time problems, they've broken those which were good."

 

Sorry! I rectify what I've said! I haven't tried it after a long while and now I've noticed something that I didn't like at all, something that I most likely haven't noticed (didn't test enough) the last time I've tried it some years ago!. It seems that they haven't changed anything at all in fact, but I've just noticed intriguing stuff very late. Above critical AoA (18 AoA for this aircraft) and up to almost 25 AoA and some more, any roll command that you give to the L-39 while trying to keep the Beta near zero (a full corresponding rudder direction should bring you closer to zero sideslip), will have your aircraft roll like there is no stall over the ailerons at all! Now I understand that it has been having this problem since it appeared and remained like this! How could this be? The people's answers here make me believe that very few to none actually understand what must happen (more or less, all the known planes are affected the same way)! In reality, for elevon and also non-elevon planes, the greatest rolling moment and rate (for no side slip condition) that you can achieve is near null lift AoA. It's generally around 0 AoA, but at somewhat negative AoA (usually no greater than -5) for cambered airfoils wings. For both elevon and conventional elevators planes, the greater the AoA (positive or negative) gets, the rolling moment and trimmed rate will start to slightly and constantly decay! As the AoA continues to grow, usually over between 50-70% of the critical, the rolling moment will start to become 0 more and more rapidly as you approach the stall AoA, even if you can still hold a zero Beta angle (sideslip) to denying the adverse yaw due to roll (at positive AoA). Still holding a zero Beta above the critical AoA, the realistic rolling moments and rates will become very low, normally less than 1-3% of the maximum attained at zero lift AoA. Above 30-50 AoA (the lower limit AoAs for non-elevon and the higher limit AoAs for elevon), on a real aircraft, no more rolling inputs and moments should ever occur. At that AoA they have already become zero. Indeed, for the DCS L-39, above some 30-40 AoA, the ailerons deflection don't give any rolling moments anymore, but between stall at around 17-18 AoA and up to almost 30 AoA (only above 25 it starts to diminish), the DCS L-39 rolls with no problem and this ruins a correct simulation quite a lot. You'll simply get something very wrong instead of the expected behavior if, for example, you apply cross controls at some 20AoA (2 degrees above wings stall). Instead of throwing itself into a spin towards the rudder input, it throws itself into a spin towards the aileron input! With the DCS L-39, if you go past the critical AoA and one wing drops (very realistic for this), you can just simply correct the wing drop by applying aileron in opposite direction to the drop tendency. Very wrong! In reality, that would rapidly send your already stalled wing into deeper stall and eventually into a spin. This doesn't happen in this game.

 

Another problem is that the roll due to yaw isn't becoming opposite from a low enough negative AoA. For instance, the L-39 has nearly symmetrical airfoils, if not symmetrical. Any negative AoA value (let's say higher than -1) should have your aircraft start rolling to the opposite side of the rudder input with no aileron input (just pitch). On the DCS L-39, only after going beyond -15 AoA the roll eventually starts to develop in opposite direction to the rudder input. Again, you cannot perform a real maneuver that you would perform in the real L-39 with this issue. I don't even need to confirm that the real L-39 has to start rolling by itself opposite to the rudder input above some relatively low negative AoA. Even on highly cambered, zero dihedral and zero sweep (the dihedral and sweep angles matter a lot), when going beyond -5 AoA, the plane starts rolling opposite to the the rudder or otherwise said, in the same direction as the generated Beta. These things should get fixed before they become forgotten like other FM issues of other aircraft!

 

Sadly, the A-10s also don't simulate stall on ailerons between stall AoA (16-17 for A-10) and up to 30 and even above, but..., at least the A-10s, although having quite some positive wing dihedral, it still starts simulating an opposite roll due to rudder above -12 AoA. It's still quite too high though because the DCS A-10C is simulated with symmetrical airfoils (utterly wrong), confirmed by having a zero G-load at zero AoA..., just that dumb!

 

Only the Su-25 (among these ground attack planes) is actually correctly simulating the ailerons stall. Just above 17-18 AoA, the ailerons only produce greater drag with almost zero lift. Perfectly done. That's how a correctly simulated rolling response to ailerons and AoA should look like. But..., the Su-25 is also plagued from the too high negative AoA above which the roll will eventually start to develop opposite to rudder. Everything about these issues can be seen in the following track file. Yes, the subject is about the L-39, but I don't have much time to start making topics allover the place to point out the issues. The developers can see the problem from 3 references now:

 

L-39 and A-10C (both aircraft), wrong rolling moments with AoA and aileron inputs.trk

 

Please abstain your answers until later and don't waste my time unless you are an ED flight model developer or someone who correctly understands what I wrote! You have my respect! Thanks!


Edited by 85th_Maverick

Good knowledge and common sense make the absurd run for defense.

Flying has always been a great interest for mankind, yet learning everything about it brought the greatest challenge!

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What? I took her up for a short while yesterday and didn't notice anything out of ordinary. Or at least the plane still stalls at high enough AoA, no idea if something else is amiss though.

The DCS Mi-8MTV2. The best aviational BBW experience you could ever dream of.

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In my mind this is probably the most realistic plane to fly in DCS. Lots of videos in YT and written text about real l39 and ours seems to be pretty spot on for most parts.

 

Then again this is probably the more easier plane to model in terms of FM. Subsonic jet, relatively shallow speed regime, lack of spinning propeller creating forces to the airframe and control surfaces etc.

 

Only gripe from me is the full flap behaviour. The autotrim event indeed is realistic but as we often use poor self-centering sticks, the experience is wrong, afaik irl l39 there is very little pitch change when applying full flaps. I wish there was a special tab option for alternative flaps behaviour, that would be less realistic aerodynamically but more realistic from how pilot experiences.

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  • 2 weeks later...
...that would be less realistic aerodynamically but more realistic from how pilot experiences.

 

What are you saying there? So the real pilots get an "unrealistic" real plane behavior? That's what it sounds like what you've just said!

 

Yes, every type of positively (usually positive, only gliders have it negative) deflected flaps will give different natural pitch down moment (what we normally call the pitching moment coef within the aerodynamic center). For example, the real plain flap types give the least pitch down for a given deflection, while multiple slotted fowler flaps give the greatest pitch down of all. The L-39 with a single slotted fowler, should be somewhere in between a plain flap's generated downward pitching moment and that of a tripple slotted fowler (from my knowledge, it should be closer to the tripple slotted fowler anyway). In DCS, the L-39 has a very abnormal pitching moment versus flaps behavior and it makes me wonder how ED (the makers) have managed to make the L-39s flaps give you hilarious/ridiculous pitch up moment during the extension period and then find just a very slight pitch down moment after it has fully extended, while the F-18 has a crazy abnormal pitch down with flaps out which even makes the F-18 jump in negative deep stall like thrown from a giant spring, spring which also holds it there tight (at around -50..-60 AoA) until you rise your flaps and start flying again! Makes no sense and there will never be none!

 

In order to have a relatively good reference of how the pitching moment behaves with flaps (not necessarily need to calculate/know the pitch down moment itself, but only the tendency and up to some degree, determine if the resulted moment is abnormally high or low) you can simply trim your aircraft to a reference AoA (use only the pitch trim, leaving the stick released) and see how that AoA evolves with flaps. For the L-39, I've used 10 positive AoA and after I've extended the flaps, the AoA started climbing to 13.5, then went back to about 9. =))).

 

Here's a track if someone wants proof:

L-39 wrong Cm versus flaps deflection function indeed.trk

 

That has nothing to do with reality and if you meant about that, you're perfectly right my friend! I didn't bother to see what happens at negative AoAs, although for a correct simulation, the differences should be about the same as what happens at positive. From my general experience (both a pilot (I fly gliders and GA) and aerospace engineer/aerodynamicist), after the flaps have reached their extended position for this kind of single slotted fowler, by not having any pitch control altered (trim or stick), the resulted AoA should decrease with at least 3 degrees, leaving you at around 2, if were flying at 5 AoA with them retracted. The function of pitching moment versus flaps deflection and AoA is non-linear, in such that as the AoA gets higher, the pitch down given by the flaps reduces more and more (due to the stalled/reversed flow on the lower pressure side of the flaps surface), but until the stall occurs, this type of fowler should give you anywhere between 2 to 4 degrees of lower AoA from an initial positive, or the same amount higher negative if starting from a negative one. Speaking of witch, the flaps, especially the fowler should also drastically decrease your critical AoA. The tripple slotted folwer of airliners decreases the stall AoA by as much as 5 degrees or more (depends on wing sweep and aspect ratio). Here, except for the Su-25 which is the only aircraft in DCS which does simulate different critical AoA versus leading edge and trailing edge devices, no other aircraft does it. This is a big, big failure on a simulator that brags to be realistic!

 

Cheers!


Edited by 85th_Maverick

Good knowledge and common sense make the absurd run for defense.

Flying has always been a great interest for mankind, yet learning everything about it brought the greatest challenge!

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What are you saying there? So the real pilots get an "unrealistic" real plane behavior? That's what it sounds like what you've just said!

 

Everything that i say falls into "AFAIK" category, so bear that in mind.

 

AFAIK in real L39 there is (dedicated?) another trim tab that actuates when FULL flaps are deployed (Wikipedia: An automatic trimming system was present, the flaps and the trim system being connected in order to counteract the potentially large pitch changes that would otherwise be generated by vigorous movements of the flaps), so that the plane, in real life, will have very little pitch change. (According to POH). In DCS i think this tab is modeled, which is realistic, but makes us trim alot against it because our regulart sticks are always trimmed at neutral position due to springs. So, AFAIK, in real life the full flaps is "not much happening" , but for us with regular sticks it is violent-ish pitch-up we have to deal with, that is "unrealistic" because real life pilot does not encounter that.

 

I hope you got what i mean and someone who knows better should participate.

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  • ED Team
What are you saying there? So the real pilots get an "unrealistic" real plane behavior? That's what it sounds like what you've just said!

 

Yes, every type of positively (usually positive, only gliders have it negative) deflected flaps will give different natural pitch down moment (what we normally call the pitching moment coef within the aerodynamic center). For example, the real plain flap types give the least pitch down for a given deflection, while multiple slotted fowler flaps give the greatest pitch down of all. The L-39 with a single slotted fowler, should be somewhere in between a plain flap's generated downward pitching moment and that of a tripple slotted fowler (from my knowledge, it should be closer to the tripple slotted fowler anyway). In DCS, the L-39 has a very abnormal pitching moment versus flaps behavior and it makes me wonder how ED (the makers) have managed to make the L-39s flaps give you hilarious/ridiculous pitch up moment during the extension period and then find just a very slight pitch down moment after it has fully extended, while the F-18 has a crazy abnormal pitch down with flaps out which even makes the F-18 jump in negative deep stall like thrown from a giant spring, spring which also holds it there tight (at around -50..-60 AoA) until you rise your flaps and start flying again! Makes no sense and there will never be none!

 

In order to have a relatively good reference of how the pitching moment behaves with flaps (not necessarily need to calculate/know the pitch down moment itself, but only the tendency and up to some degree, determine if the resulted moment is abnormally high or low) you can simply trim your aircraft to a reference AoA (use only the pitch trim, leaving the stick released) and see how that AoA evolves with flaps. For the L-39, I've used 10 positive AoA and after I've extended the flaps, the AoA started climbing to 13.5, then went back to about 9. =))).

 

Here's a track if someone wants proof:

[ATTACH]234762[/ATTACH]

 

That has nothing to do with reality and if you meant about that, you're perfectly right my friend! I didn't bother to see what happens at negative AoAs, although for a correct simulation, the differences should be about the same as what happens at positive. From my general experience (both a pilot (I fly gliders and GA) and aerospace engineer/aerodynamicist), after the flaps have reached their extended position for this kind of single slotted fowler, by not having any pitch control altered (trim or stick), the resulted AoA should decrease with at least 3 degrees, leaving you at around 2, if were flying at 5 AoA with them retracted. The function of pitching moment versus flaps deflection and AoA is non-linear, in such that as the AoA gets higher, the pitch down given by the flaps reduces more and more (due to the stalled/reversed flow on the lower pressure side of the flaps surface), but until the stall occurs, this type of fowler should give you anywhere between 2 to 4 degrees of lower AoA from an initial positive, or the same amount higher negative if starting from a negative one. Speaking of witch, the flaps, especially the fowler should also drastically decrease your critical AoA. The tripple slotted folwer of airliners decreases the stall AoA by as much as 5 degrees or more (depends on wing sweep and aspect ratio). Here, except for the Su-25 which is the only aircraft in DCS which does simulate different critical AoA versus leading edge and trailing edge devices, no other aircraft does it. This is a big, big failure on a simulator that brags to be realistic!

 

Cheers!

 

L-39 has automatic trim compensator for the flaps.

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

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