Bf109 flight model issue.

[1PL-Husar-1Esk]

Skills aren't an issue I had over 350 victories in early beta multiplayer after that I quit counting it wasn't unusual for me to have double-digit Victory marks in a single 60-minute session so it isn't skill it's that traditional luftwaffe tactics no longer work in this game boom and zoom fighting is useless because the Yaks can catch you even if you started with the energy Advantage even though I 16 can catch up to the 109 the main issue is that apply model does not represent the historical overpowering ability of the 109 to dominate early War Russian aircraft I understand the need for balance but all they've accomplished is destroying any advantage the 109 had in fighting the tiger turning Russian Fighters and those are speed and high altitude performance

I flown most 109 in begining then switched to Yaks and now back to 109 & 190, i have oposite opinion than you. German planes are far better than VVS planes - there is no magic and no overperforming I-16 or Yak, all is in pilot skill. Btw i feel save in 109 for sure. I have more options and know enemy limitations. Btw i little worried how well i can pusch 109 to get that deflection shot.

[II/JG17_HerrMurf]

The 109 F, G and the 190 will all outclimb the Soviet AC with some minor altitude specific exceptions to the 190. I have yet to lose a simple footrace even when I start at a slight E disadvantage over the last two years and I fly the 190 almost exclusively. Pitch for 300 kph in any German airframe from Co-E or better and you are virtually untouchable. If you are getting caught it is simply because you are zoom climbing too steeply and getting caught by a pilot who knows his aircraft. There are lots of minor problems with all of the AC and I'm sure it will get worked out in time but this relative climb accusation is meritless.

Edited August 19, 2016 by II/JG17_HerrMurf

[Crump]

Energy retention is just plain and simple physics.

Yes but that is not what he is talking about. [edited] JG_13opcode's statement is absolutely correct.

 

In these games, you hear it most often in terms of turn performance. "The aircraft retains energy in the turn". That has no place in either physics or aircraft performance.

 

TE = PE + KE

 

The TE or total energy never changes..... it simply balances between potential for work and the performance of work.

 

Fighter Pilots use the term "Energy Retention" in the framework of theory such as Energy Concepts for Aircraft Performance which has become a modern standard for evaluating maneuvering potential.

 

They are correctly referring to the exchange back and forth of Kinetic Energy to Potential energy and which one they need in the moment for the specific tactical engagement.

Edited August 19, 2016 by SYN_Haashashin
Do not get personal, last warning

[Crump]

"Energy retention" is a meaningless term that sim pilots who lack a complete understanding of aircraft performance came up with. Nobody tested for that historically and there is no agreed-upon definition. There was a guy named TAGERT who posts here occasionally under a different name that came up with a pretty good dive-zoom test, using devicelink to give the exact same control inputs every time. Using that he could get a reasonable idea as to the relative performance of two aircraft in a dive-pullout-zoom scenario. Determining whether or not that counts as "Energy Retention" is left as an exercise for the reader. In either case, there is no historical data to compare it to, so when a person says "the E retention is suspicious" it means "I don't like the way Plane X is modeled". Aircraft performance is in one of two domains: sustained or instantaneous. Either the aircraft can do something until it runs out of fuel (sustained), or it cannot (instantaneous).

 

That is correct.  Additionally, if you do use the correct concepts and theory correctly, you will end up with garbage.  I tried to help that guy Tagert to improve his predictions.  Instead of few minor tweaks to his systems to conform to aircraft performance concepts we ended up in a huge multi-page argument.  Not only did he try to make me look like an idiot for helping him, he was insistent upon not using aircraft performance theory correctly. 

 

That is the danger of not knowing the details.  It is like comparing infinite wing to a full sized aircraft without knowing the Reynolds Number, rate of change, and surface conditions...it is just meaningless gobbledygook without it.

 

Or like the term "service condition".  That has meaning.  Basically it equates to a certain level of mud on the aircraft and bugs smashed on the leading edge.  It is not an airplane delivered from the factory for military service.

[Fern]

Crump, you beat me to it! I was going bring up kinetic and potential energy also. Lets take a jet engine, it's fuel is it's potential energy that it has stored and turns that into it's kinetic energy. They teach this in the Air Force to Jet Engine Mechanics along with Newtons Law and the Bernoulli principle.

 

We are using Potential and Kinetic energy everytime we play this game.

 

Just remember Potential is energy stored: fuel for your engine or your altitude advantage. Kinetic energy is the object or energy in motion. You cant achieve kinetic without the potential.

 

 

Here's some questionable La-5 kinetic energy. Yes, I had wing cannons and yes, I did a steep climb at the end. But how he gained on me after a turn like that is beyond me. I was going atleast 400 km after the pass into the climb.

 

Edited August 19, 2016 by Fern

[Crump]

Exactly Fern, you have to be very careful with definitions and terms in aerodynamics.

 

Let me add to that.  I have found some NACA reports that define "Service Condition" not in terms of surface roughness but in terms of construction.  In this case, it is defined in terms of fairing and surface waviness.  It discusses various manufacturing techniques and how to keep the aircraft with in the design parameters thru proper construction.

 

 

 

Here's some questionable La-5 kinetic energy.

 

 

He has landing flaps deployed it looks like in the zoom?  

[JG13_opcode]

Energy retention is just plain and simple physics. Change of total mechanical energy over time.

Hi JtD, I agree that that's one valid definition, but what I was saying is that the term means different things to different people. For example if someone asked me to define "energy retention" I would say it's the tangent to a curve of excess power vs mach for a particular load factor at a given instant in time. In test pilot school they call it the maneuvering energy rate and it varies throughout the maneuver. Your definition would be more like the secant to that function, integrated over the duration of the maneuver. I'm not saying that either interpretation is more valid than the other, only that the term is overloaded.  

 

... derived from available data, such as speed, climb, turn or glide information. Of course this can be measured in game, and of course it's situation specific.

I'd have to go back and check but I'm quite certain I never said it can't be measured, only that "e retention" wasn't tested historically. Could it be derived from historical data? Perhaps. I've never seen precise figures for entry and exit energy states (speed, alt) from a particular maneuver in any of the historical charts I've ever come across.

 

I'm also a little dubious of the value of "energy retention" as a performance metric.  What does it tell us that's not captured by a doghouse plot of the envelope, and/or plots of excess thrust/power vs mach?

 

I think that you'll have to get used to that catchy and simple, sometimes inaccurate physical concepts will be used

I prefer to rage against the dying of the light 

Edited August 19, 2016 by JG13_opcode

[JG13_opcode]

Here's some questionable La-5 kinetic energy. Yes, I had wing cannons and yes, I did a steep climb at the end. But how he gained on me after a turn like that is beyond me. I was going atleast 400 km after the pass into the climb.

 

 

I dunno, it doesn't seem totally outlandish minus the flap usage.  Hasn't it been shown elsewhere on this board that the flaps ingame have drag issues?

 

Hard to tell from the video but it looks to me like you were only doing about 450 indicated.  You then entered a turning climb as he came back around.  He stayed lower and climbed more steeply, keeping his airspeed longer to zoom up to you.

 

I don't think your energy state was significantly higher than his at the start of the clip - you were doing a lot of turning too.

 

He has landing flaps deployed it looks like in the zoom?  

 

Yeah, not sure what's going on there.  Looks like he pops the flaps to keep the nose stable; you can see right as he hits the 109 that his nose drops.  Right on the edge of the stall as he fired.

[DD_Arthur]

  Not only did he try to make me look like an idiot for helping him, 

 

 

He did make you look like an idiot.

[JtD]

Hi JtD, I agree that that's one valid definition, but what I was saying is that the term means different things to different people. For example if someone asked me to define "energy retention" I would say it's the tangent to a curve of excess power vs mach for a particular load factor at a given instant in time. In test pilot school they call it the maneuvering energy rate and it varies throughout the maneuver. Your definition would be more like the secant to that function, integrated over the duration of the maneuver. I'm not saying that either interpretation is more valid than the other, only that the term is overloaded.

Actually, same definition, different words. Excess power is change of energy over time. W = J/s. We're not even trying and still mean the same thing.

 

I'd have to go back and check but I'm quite certain I never said it can't be measured, only that "e retention" wasn't tested historically. Could it be derived from historical data? Perhaps. I've never seen precise figures for entry and exit energy states (speed, alt) from a particular maneuver in any of the historical charts I've ever come across.

No, you didn't say it can't be measured. But you said that claiming e-retention is wrong equals an I don't like that plane statement. But since you can quantify both historical and in game performance, you can also make a qualified statement. Certainly no one tested e retention a such, but excess power or thrust certainly were used in calculations, which were validated in tests.

 

I'm also a little dubious of the value of "energy retention" as a performance metric.  What does it tell us that's not captured by a doghouse plot of the envelope, and/or plots of excess thrust/power vs mach?

Because in game impressions / tests don't necessarily give you a full set of data to produce a set of plots. And even if you do, you don't necessarily know it's drag or thrust or some odd bit of code that is off. You just realize that an aircraft maintains or loses speed, altitude or whatever in an odd/unexpected way, or more qualified in a way that doesn't match historical data.

 

I prefer to rage against the dying of the light.

Good luck with that!

[Fern]

I was just thinking after the pass he makes the turn which he should of loss some energy, but instead starts to gain on me quickly. Granted I started the climb which helped him gain, but he also had to climb. I thought I would have enough separation to start a climb. I didnt make any crazy maneuvers after the pass until my steep climb at the end. His max speed is 507 or 537 with WEP/G2 is 527 at 0 to 2000m, according to klauss.. i was going 450 knots after pass into the climb which he gains on me into the climb? I lose speed,but he gains? Pretty mind blowing acceleration I think.

 

Criticize my flying, I don't care. I thought the only error I made was towards the end with the steep climb. I was just amazed at that point that he caught up to me.

Edited August 19, 2016 by Fern

[Fern]

You can't blame anything but yourself. You made big mistakes there. This is precisely why every time you are going to complain about FM, it is extremely important that you provide a track. I'd go as far as to say that 99.9% of the FM complaints are just piloting errors. I have a totally crazy idea: What if instead of blaming the Fm, the devs etc after getting shot down, people would just watch their tracks and try to learn what to do better next time. How about that?

You proved nothing. You just said I was a bad pilot. How about you analyze and explain from the video instead of being [Edited]?

 

Please refrain from making personal comment of this nature.

Edited August 21, 2016 by Bearcat

[Crump]

 

 

 What does it tell us that's not captured by a doghouse plot of the envelope, and/or plots of excess thrust/power vs mach?

 

 

 

Nothing.....which is why it is not an aircraft performance parameter.  

[Crump]

 

 

He did make you look like an idiot.

 

That was his style, to insult anyone who he thought threatened him.

[JtD]

Fern, on your video - I'd say he caught on you because of your extended right hand turn back towards him, not because he gained altitude much quicker than you did. Less of a turn, steeper climb would probably have saved you, because he wouldn't have gotten into firing range. He's clearly slower than you are at all times, up to when he gets lucky, and it appears to be down to geometry not performance that he's gotten close enough in the first place.

 

We can argue about how well the prop wash in game allows us to control the aircraft at lowest speeds, which clearly helped the guy to control his La-5 very well down to the stall. But this is not an issue of energy retention through turns or climbs. In that regard, I didn't see anything that couldn't be explained by a low fuel load and Forzash.

[JG13_opcode]

Actually, same definition, different words. Excess power is change of energy over time. W = J/s. We're not even trying and still mean the same thing.

I'm talking derivatives, whereas if I understand you correctly, you're talking deltas. Close but still distinct, and such was my point

 

But you said that claiming e-retention is wrong equals an I don't like that plane statement. But since you can quantify both historical and in game performance, you can also make a qualified statement.

Ah, but my experience has almost exclusively been people doing the former, not the latter.

 

Certainly no one tested e retention a such, but excess power or thrust certainly were used in calculations, which were validated in tests.

Agree.

 

 

And even if you do, you don't necessarily know it's drag or thrust or some odd bit of code that is off. You just realize that an aircraft maintains or loses speed, altitude or whatever in an odd/unexpected way, or more qualified in a way that doesn't match historical data.

Sure, but then we get into the rabbit hole of trying to discern between a bug in the flight model (i.e. using "model' in the conceptual/flowchart/UML sense) vs a bug in the implementation of the flight model (i.e. using "model" in the sense of the code that actually gets written).  It's been my experience that the implementation of code often differs dramatically from both the drawing board model and from what's written in the documentation, and consumer flight sims are not subject to the same degree of formal analysis/validation as safety-critical code in, say, avionics control systems or what have you.

 

We as the community can either spend effort debating whether something is a flaw in the model (as in, the simplified model that the sim uses produces invalid Cl/Cd values) or if something is a flaw in the implementation (as in, someone somewhere put an extra 0 or called a function with the wrong arguments or missed a decimal place, etc.) 'til the cows come home but it's counterproductive IMHO.  

 

Again IMHO, far better to just document and point out problems, and let the experts figure out if their virtual DB605 produces too few horsepower or if it's just that the lapse rate of their virtual atmosphere is wrong (as a made up example).

 

edit: misread something

Edited August 19, 2016 by JG13_opcode

[JtD]

Again IMHO, far better to just document and point out problems, and let the experts figure out if their virtual DB605 produces too few horsepower or if it's just that the lapse rate of their virtual atmosphere is wrong (as a made up example).

Agree with all of the above. In response to the quoted part I would like to point out that there's also a FM bug report topic buried somewhere on this board. Imho, for actual reports, that should be used. In here, it's far more liberal - where'd be the point in discussing things if the case was closed with the opening post? Edited August 19, 2016 by JtD

[DD_Arthur]

That was his style, to insult anyone who he thought threatened him.

 

He did have a certain style,  thats very true.  I'm not quite sure whether he felt threatened by you but he certainly did think you were an idiot.   

[Crump]

 

 

you don't necessarily know it's drag or thrust or some odd bit of code that is off.

 

It is very easy to compare performance in the game with what the aircraft should be able to do.

 

A given amount of force will result in given performance within reason.  

 

In fact, that is the entire basis of Total Energy Concepts for Aircraft Performance and all Aircraft Performance Math.  Specific Excess Power (Ps) is that reasonable expectation maneuvering potential of an aircraft.

 

So in other words, if the performance math does not equal the in game performance within reason.....there is something wrong with the FM.  It is not something is flawed with standard aircraft performance math predictions or aircraft do some undiscovered "trick" of physics.

 

 

 

 

 

We as the community can either spend effort debating whether something is a flaw in the model (as in, the simplified model that the sim uses produces invalid Cl/Cd values) or if something is a flaw in the implementation (as in, someone somewhere put an extra 0 or called a function with the wrong arguments or missed a decimal place, etc.) 'til the cows come home but it's counterproductive IMHO.  

 

Absolutely....that is for the Devs to find out.  

 

The players just need to be concerned with the end product. 

[Crump]

He did have a certain style,  thats very true.  I'm not quite sure whether he felt threatened by you but he certainly did think you were an idiot.   

 

 

He thought everybody but him was an idiot...including you!! 

 

Usually those kind of people have other issues.  Like those who jump into conversation with nothing real to add except dragging other down.

[DD_Arthur]

Usually those kind of people have other issues.  Like those who jump into conversation with nothing real to add except dragging other down.

 

Thats very true.  People can sometimes be...so cruel.    Anyway, back to the OP.  

 

So how do you find the BoS '109 FM Crump?

[Crump]

 

 

Excess power is change of energy over time. W = J/s. We're not even trying and still mean the same thing.

 

There are some very simple test's that can be used to gather data points to determine an aircraft's specific excess power.  There is no need to reinvent the wheel.

 

Simple saw tooth climb schedules will give all the data needed to evaluate the Ps of each aircraft.  That can be evaluated against measured flight data quite easily.

[JG13_opcode]

There are some very simple test's that can be used to gather data points to determine an aircraft's specific excess power.  There is no need to reinvent the wheel.

 

Simple saw tooth climb schedules will give all the data needed to evaluate the Ps of each aircraft.  That can be evaluated against measured flight data quite easily.

 

I prefer the dive-decelerate method in-game, mostly because my gear is [Edited] and I can't maintain the +/- 1 kt standard for a sawtooth climb.

Edited August 21, 2016 by Bearcat
Profanity

[Crump]

I prefer the dive-decelerate method in-game, mostly because my gear is shitty and I can't maintain the +/- 1 kt standard for a sawtooth climb.

 

Most of the Total Energy data reduction flight schedules I have seen are based off level acceleration or constant airspeed saw tooth climbs.

 

Any series of constant speed climbs to a specific altitude gain (usually 1000feet) will work as long as the speed is constant in the climb and the altitude gain recorded.  The saw tooth just gives you multiple data points to gather a mean in order to reduce pilot induced error in the math.

[Crump]

You simply start from constant state level flight at the target airspeed, add power and climb at that airspeed to the set altitude.  Record the time.

 

Level acceleration is starting in steady state level flight from a start speed and accelerating to the end speed.  Record the time.

The more data points you gather under the same conditions, the more accurate the prediction.  Five flight schedules would give you a good base and reasonable return.

[Crump]

You can bounce that data off specific points on the L/D curves, Thrust Required, and Power Required curves found in the Operating instructions for the aircraft.  If those points do not equate to the same points in your FM...then you FM is not representative.

[Venturi]

I dunno about all this stuff about TE=KE+PE "and that's it, it's all physics." Sounds simplistic to me. There is definitely meaning in the term, "retained energy in a turn." As far as I can tell, TE=KE+PE equation is only a snapshot of the airplane at one moment in time. What we are looking for when talking about a turn is more along the lines of the calculus: 

 

[the change in Total Energy (TE) - chagne in heat] of the aircraft over time. 

 

And that is complex stuff and definitely can vary from aircraft to aircraft. 

 

Because in a turn, an aircraft's KE is being scrubbed into air turbulence and heat by the wings, which is why you slow down in a turn to begin with. That is a complex dynamic dealing with wing drag and behavior at different angles of attack.

 

To put it simply, there will be less turbulence and heat, thus less energy loss and greater KE and/or PE with an aircraft whose wing performs better in a turn, than with an aircraft which is scrubbing more because it's wing performs less well in a turn.

 

No aeronautics degree, but I did sleep at a holiday inn express last night.

Edited August 19, 2016 by Venturi

[Venturi]

The amount of drag imposed on a wing in a turn as the boundary layer separates along the upper surface will change based on the wing profile. Thus different wings will generate different amounts of drag at different angles of attack.

 

I don't have a degree in aeronautics but the concept seems very straightforward to me.

Edited August 19, 2016 by Venturi

[Crump]

 

 

As far as I can tell, TE=KE+PE equation is only a snapshot of the airplane at one moment in time.

 

 

Nope, with a few data points you can determine the entire envelope of the aircraft.

I don't have a degree in aeronautics 

 

Thank you for your input, anyway!  

[Venturi]

Really? You can determine how a wing will behave at all angles of attack with a few data points?

 

Interesting, so which data points do you need then?

Edited August 19, 2016 by Venturi

[Crump]

 

 

eally? You can determine how a wing will behave at all angles of attack with a few data points?  

 

 

Not what I said.  I can tell you the performance envelope from a few data points.  Aircraft behaviors is different math.

[Venturi]

Oh, I was curious as to the fluid dynamics of the medium! I wanted to know how your calcs could determine wing drag at different angles of attack from a couple of data points!

 

Thanks!

[Crump]

 

 

Oh, I was curious as to the fluid dynamics of the medium! I wanted to know how your calcs could determine wing drag at different angles of attack from a couple of data points!   Thanks!

 

You can determine drag.  That is a different question.

[JG13_opcode]

Most of the Total Energy data reduction flight schedules I have seen are based off level acceleration or constant airspeed saw tooth climbs.

 

Any series of constant speed climbs to a specific altitude gain (usually 1000feet) will work as long as the speed is constant in the climb and the altitude gain recorded.  The saw tooth just gives you multiple data points to gather a mean in order to reduce pilot induced error in the math.

 

Yeah, I just do the dive-decelerate method because I am super lazy and don't want to do the level acceleration method because it takes too long.

Edited August 19, 2016 by JG13_opcode

[Fern]

Holy crap, I just looked up the sawtooth climbs test methods and that looks like a bunch of work Crump. Would be awesome if you could get it done.

 

https://books.google.com/books?id=IdWmOwceEtIC&pg=PA129&lpg=PA129&dq=sawtooth+climb+schedule&source=bl&ots=3KHHSYfoNT&sig=LwV4I0tz_A3L_LTTuE0RFcGxfa4&hl=en&sa=X&ved=0ahUKEwjIoMumrc7OAhVFiywKHbQkDqgQ6AEILzAD#v=onepage&q=sawtooth%20climb%20schedule&f=false

[JG13_opcode]

Oh, I was curious as to the fluid dynamics of the medium! I wanted to know how your calcs could determine wing drag at different angles of attack from a couple of data points!

 

Thanks!

Have a look at the wikipedia article for the drag coefficient.

 

Cd = Drag / q * S 

Given speed and density (altitude), you can estimate Cd with only the reference area (usually planform area). In a turn, your Drag quantity is a function of load factor.

 

I dunno about all this stuff about TE=KE+PE "and that's it, it's all physics." Sounds simplistic to me. There is definitely meaning in the term, "retained energy in a turn." As far as I can tell, TE=KE+PE equation is only a snapshot of the airplane at one moment in time. What we are looking for when talking about a turn is more along the lines of the calculus:

It may seem simplistic, because it is a succinct summation of a lot of things. Energy conservation is a fundamental principle of physics, and while calculating total energy is a snapshot, what I believe JtD was getting at is that you take a snapshot and the beginning and end of the maneuver, and the difference could be considered your "energy retention" expressed as the amount of energy dissipated by the maneuver against the air via drag.

 

Since you seem to prefer calculus, consider it this way:

 

If TE is a function describing the total energy of the airplane at a given snapshot (i.e. a derivative), you can integrate TE in the time domain to get a summation of the energy states throughout the maneuver.

Edited August 19, 2016 by JG13_opcode

[Venturi]

The point is that at some point turbulence generated drag (IE, loss of TE) at high angles of attack is no longer easily calculated except empirically or by approximation. 

[JG13_opcode]

The point is that at some point turbulence generated drag (IE, loss of TE) at high angles of attack is no longer easily calculated except empirically or by approximation.

That's not really correct. You can calculate the effects on the aircraft's energy quite easily, because you know the beginning and end states.

 

Look at it this way: you are in your car doing ~40 m/s when you see a police car. You slam on the brakes to get to 27 m/s. If your car weighs 1000 kg, then your delta energy is 0.5*1000*(40^2 - 27^2).  Do you care how hot your brakes get when you hit the pedal?  Do you care what the turbulent flow over the roof of your car is doing?  No, you still know how much energy you lost.  Your braking caused 435500 Joules to be dissipated in some form or another.

 

edit:  units lol

Edited August 19, 2016 by JG13_opcode

[Crump]

Listen Venturi....listen.  

[Venturi]

That's not really correct. You can calculate the effects on the aircraft's energy quite easily, because you know the beginning and end states.

 

 

And you know exactly what an aircraft's energy state is at the end of a turn, because.... why??? Because it is what the sim spit out?

 

How did you get the amount of drag from turbulent airflow which caused the aircraft to slow down??? Therefore how do you know the aircraft slowed down enough (or too much) in the sim?

 

So how do you know the end energy state is correct at the end of the turn which all your suppositions are based upon?

 

If you use data points of real aircraft turning, to estimate end point energy losses, do you then know the angle of attack that the wing is experiencing throughout the turn? Howabout half way through the turn as the plane has slowed?

 

You maybe see my point.

 

Anyways, carry on  

Edited August 19, 2016 by Venturi