Slipstream modelling and the 109

[HagarTheHorrible]

I think I read somewhere that the Digital Nature Engine models slipstream ?

 

If this is the case it will be interesting to see if and how it affects the slats on the 109.  I have just read a bit by Eric Brown about the 109 in which he says "Another problem the Bf 109 had was that it could not follow in a steep turn when using a lot of engine power.  If so, the Bf109 would get into your heavy slipstream and as he has slats on the wings of his aircraft, these would tend to come out and snatch as the airspeed varies. And in these turns when the slats open and close unevenly, a rocking motion develops that ruins your shooting.

 

Presumably if slats provide advantages then they should also model any disadvantages ?

[LLv34_Flanker]

S!

 

 Never heard about or read from books by any veteran. Sure can be possible, but I bet more of a rarity than a rule. The more aerodynamical effects you guys want in the more CPU intense the game gets thus less performance.

[HagarTheHorrible]

I assume this problem with slats would effect any aircraft so fitted and not just the 109 ?   I also don't understand why he specifically mentions "when using a lot of engine power".  Maybe somebody can explain ?

[Sokol1]

Nice,  it will a very innovative characteristic in simulator.

 

 

Bob Doe had got ahead of the rest of the Squadron and found himself alone, when he spotted a gaggle of about fifty Bf 109s, probably JG53.

Knowing that numbers were trumped by surprise and that he would be difficult to see, he climbed above them and dived on the rear of the formation in a perfect bounce.
Opening fire at 300 yards, he hit his target, but his target's slipstream hit him and his engine cut.

 

 

Sokol1

[DD_bongodriver]

There must be more to that anecdote, engines don't just cut because of slipstream, maybe a momentary cut from neg g in turbulence but not simply cut permanently.

[II./JG27_Rich]

Go to 9 minutes. It all depends who you ask I guess.

 

 

 

[HagarTheHorrible]

Go to 9 minutes. It all depends who you ask I guess.

 

 

 

 

Very interesting.  It does suppose that the two points of view contradict each other.  

 

I think the first thing to consider is that Eric is talking about a specific set of circumstances, a full power climbing turn in pursuit of a target aircraft and how the slats react to "heavy slipstream" with regards to a firing solution rather than general flying, even to the point of the same manoeuvre but not chasing a target aircraft  ( I think we might consider this type of combat situation to be more common rather than less).  The second point would be that I have a better knowledge of Eric Brown's back history and know that he did extensive testing of German aircraft both during and after the war, carried out fighter to fighter evaluations and last but not least  interviewed, de-briefed and worked with many German pilots and designers after the war, so if I had to go with one persons view over that of another I would have to plump with Eric's for the moment, but again, and I stress, that is to assume that both views are mutually exclusive to one another.

Edited December 4, 2013 by HagarTheHorrible

[Crump]

 

 It all depends who you ask I guess.

 

 

Yes if the aircraft is properly maintained and the slats lubricated/bearings serviceable they should work exactly as described in the video.  They work as required automatically.  I owned an airplane had handley page automatic slats and have several hundred hours flying with them.  The stick would sometimes have a small but sharp bump when the slats deployed under a hard pull.  It never effected the flight path at all.  The airplane did not move.

 

The stick notch was a good indicator the slats had deployed is all.

 

 

 had to go with one persons view over that of another I would have to plump with Eric's for the moment, but again, and I stress, that is to assume that both views are mutually exclusive to one another.

 

 

I think people focus on that stick notch as something that ruins the aircraft.  It is just part of the personality of slat equipped airplanes.

 

 

 so, the Bf109 would get into your heavy slipstream and as he has slats on the wings of his aircraft, these would tend to come out and snatch as the airspeed varies.

 

 

The slats in and of themselves should not induce a rolling moment IF they are functioning properly, they are just providing only the lift required that the wing needs. 

 

 

In order to induce a moment, they would have exceed that force required. 

 

 

What will induce a rolling moment is the slipstream.   In this case, the condition is specific in that it occurred only when in a heavy slipstream of another aircraft. 

 

Many airplanes will exhibit Dutch roll in a turn with a quartering wind and some will even experience it in level flight under those conditions.  A tail dragger, especially a short coupled one is also more susceptible to them.  You know a dutch roll is such short period it is hard to detect and correct by control input alone.  Dutch roll will also reach an equilibrium and not dissipate unless corrected or condition of flight changes. 

 

I have no doubt that a strong slipstream striking only a portion of the aircraft would induce a dutch roll.

 

That is what it sounds like to me.  In a turn, under certain conditions, the slipstream is creating a dutch roll. 

 

The Bf-109 initially had strong static/dynamic lateral stability and longitudinal stability but was weaker in directional stability.  This is what made it a flying shooting platform.  Most designers built a maneuvering airplane you had to learn to shoot from while Mtt built a shooting platform you had to learn to maneuver!

 

Those same stability and control characteristics of strong lateral and weak directional are the perfect ingredients for dutch roll.  The airplane would exhibit dutch roll at high speeds until it was corrected by increasing the tail surface and directional stability.

Edited December 4, 2013 by Crump

[BraveSirRobin]

Slipstream is not modeled in MP in RoF.

[DD_bongodriver]

sounds to me what Eric Brown is actually describing is how the turbulence from the slipstream of the aircraft in front will cause the 109's slats to deploy randomly due to the fact they are not in free stream air, it is a well known that flying in turbulence will cause angle of attack to fluctuate, so when in a tight turn and the 109 slats are on the edge of deployment and turbulence is encountered then the slats will pop in and out and will do so asymmetrically and assymetric slat deployment 'will' cause a rolling moment, the mention of high power I think is descriptive of the aircraft in front (it sounds like the narration is being given from the perspective of the leading aircraft) which in this case it is to imply that the high power setting is creating more propwash which will add to the effect of slipstream and make the chasing 109's life more difficult.

[SKG51_robtek]

Pardon me, but the slats are coming out when the lift is reduced on that particular wing( by slipstream, angle of attack or whatever.), and they are retracted when the reason for deployment are gone, here when the wing is producing enough lift again.

> that means that the slats are only correcting a possible problem, not create one.

They will not create more lift than there is lost by the slipstream.

[DD_bongodriver]

No, other way around, if lift is reduced then slats retract, slats deploy when the wing reaches a high angle of attack this by default means as lift is increasing.

 

slats have disadvantages too, it's not all positive magic, asymmetric slat deployment will cause a rolling moment.

Edited December 4, 2013 by DD_bongodriver

[HagarTheHorrible]

I think it was Britain that first looked at and implemented slats in the 1930's, before giving them up, maybe at that time the technology and understanding wasn't ready.  However I can't think of any major Second World War Western Allied fighter that employed them, even though they would have had the opportunity and time to test and implement new designs, so why not if they only had positive benefits ?  It's not as if all, even contemporary German fighters, employed leading edge slats.

 

I suppose the rocking motion doesn't need to be very much, just enough to frustrate an aimed guns solution, rather than it having an overly detrimental effect on the aircraft's flying ability.  The problem would possibly be more obvious because it's a likely natural escape route for the attacked aircraft, to pull and turn.

Edited December 4, 2013 by HagarTheHorrible

[MiloMorai]

Maybe it had to do with the size (area) of the wing? The Germans and Soviets used them but the wing area of them was small.

[HagarTheHorrible]

Maybe it had to do with the size (area) of the wing? The Germans and Soviets used them but the wing area of them was small.

 

So was that of the 190, wasn't it ?

 

I think I read that one of the reasons the Russians stuck them on some of their fighters was because it did away with some of the nasty high speed stall characteristics that made them difficult to handle in combat.

 

I wonder if the power factor that Eric talks about is possibly that the pursuing plane is maybe trying to utilize the engine power to drive the turn rather than the  pure aerodynamic capability of the aircraft and as such it is already at a high angle of attack ?

Edited December 4, 2013 by HagarTheHorrible

[DD_bongodriver]

1919 I think, apart from the roller tracks the principle behind Handley page's automatic slats were unchanged, as you have noted slats were a rarity on fighter designs and they were technically a retrofit on the 109 to tame the harsh low speed handling characteristics of it's highly loaded wing for take off and landing, the benefits they gave during high speed manoeuvring are pretty much coincidental and probably not part of the intended design (did I mention they were a retrofit), once deployed slats create high drag which is not really desirable.

[OBT-Psycho]

I think the general comprehension of what makes a top notch fighter aircraft evolved during the war. As conflicht went on, we went from a best handling to higher top speed. Thus slats were not required anymore as combat happened at speed higher than the speed slats would deploy. So why bother trying to implement this technology if it won't be used during most of the case?

 

and you know...if it ain't broken, don't fix it! so if your spitfire already has superbe cornering capabilities, why try to improve it if all you need is more speed.?

[MiloMorai]

So was that of the 190, wasn't it ?

 

Tank was a better designer than Messerschmitt.

 

Afaik slats were initially for low speed flight. If slats were that great then why didn't USN a/c use them?

[Crump]

 

They will not create more lift than there is lost by the slipstream.

 

 

That is right.  The slats will not create any lift at all.

 

Coefficient of Lift = Lift/[(1/2 density * Velocity^2) * Reference Area]

 

Lift equals weight at a constant altitude.

 

Lets run some simple math to get an idea how the slats work.

 

Fictional airplane

 

weight = Lift generation = 2500lbs

 

Wing Area = 150ft^2

 

Aircraft is equipped with slats with a design coefficient range of 1.42 to a CLmax of 2.1

 

traveling at a velocity of 100fps

 

Coefficient of lift = 2500lbs / [(1/2*.002376sl/ft^3*100fps^2)*150ft^2

 

Units all cancel leaving us with a dimensionless ratio of lifting pressure to dynamic pressure = Coefficient of lift = 1.4 = slats closed (1.42 to 2.1)

 

We slow our velocity down to 90 fps. 

 

Coefficient of lift = 2500lbs / [(1/2*.002376sl/ft^3*80fps^2)*150ft^2

 

Units all cancel leaving us a dimensionless ratio of lifting pressure to dynamic pressure = Coefficient of lift = 1.7 = slats open (1.42 to 2.1)

 

The slats open to increase the coefficient of lift over the wing section by energizing the boundary layer.

 

Our lift force required has remained 2500lbs and never changed at all!!!

 

Here is the effect of slats on coefficient of lift vs angle of attack (lift polar):

 

 

 

Since lift force required does not change that means no moment is created about the CG simply because the slats open or close in normal operation. 

 

The Bf-109 was designed with slats to mitigate the stall behavior of a wing without washout.  A properly designed high aspect ratio wing will stall root first leaving the wing tips un-stalled.  This has the dual effect of leaving some aileron authority and producing a nose down moment at the stall.  Good stall behavior results in  the airplane nose dropping while the wing remains mostly level.  Propeller effects tend to produce a bit of wing drop especially in high performance piston engine aircraft.

 

 

In order to leave our wingtips unstalled and ensure the wing root stalls first designer have a number of tricks. 

 

Commonly, a blended airfoil is used as the 2 dimensional airfoil shape determines when and how the stall occurs.  If we pick a root airfoil section that stalls at a lower Coefficient of lift then our root will stall first leaving out tips un-stalled.  This almost never works without additional help.

 

One method to improve stall behaviors is to add washout.  This is simply twisting the wing so that the root sections will be at a higher angle of attack than the wing tip sections.   This further distances the root stall angle of attack from the wingtip stall angle of attack.  It has the disadvantage of adding additional drag throughout the aircraft's envelope.

 

 

The Bf-109 wing uses the first technique of a blended 2 dimensional  airfoil section just like the Spitfire and most other World War II designs.  To avoid creating additional drag at cruise and high velocity, the wing is not twisted to add washout in the Bf-109. 

 

Instead the designer choose to use handley page automatic slats over the aileron and wingtip section.  This has the effect of dramatically increasing the section coefficient of lift ensuring our wing root stalls well before our wingtips.  With enough of the wing root section stalled, the elevator will not provide enough authority to easily induce a spin making it more spin resistant than an aircraft with simple washout.

Slats out, the airplane simply mushes around until the angle of attack is lowered enough to unstall the root section as noted in the RAE trials.

[Crump]

If our entire wing stalled at the same time, the stall characteristics would be horrible btw.  The wing would loose lift all at once and the airplane would free-fall without control or worse yet, invert from propeller effects. 

[Chill31]

I would be tremendously impressed if they modeled slip stream/wake turbulence! When you hit the wake of an 1100 hp fighter, it is a big deal absolutely throws off your aim. In fact, I won a dogfight when my adversary hit my wake at low speed which rolled him in the opposite direction he wanted during scissors. That small delay let me get in the saddle for a shot.

[Crump]

 

think I read that one of the reasons the Russians stuck them on some of their fighters was because it did away with some of the nasty high speed stall characteristics that made them difficult to handle in combat.

 

That is the main reason for slats.  They give you fantastic stall/slow flight capability without the additional drag at cruise/high speed of washout.

I think it was Britain that first looked at and implemented slats in the 1930's, before giving them up, maybe at that time the technology and understanding wasn't ready.  However I can't think of any major Second World War Western Allied fighter that employed them, even though they would have had the opportunity and time to test and implement new designs, so why not if they only had positive benefits ?  It's not as if all, even contemporary German fighters, employed leading edge slats.

 

I suppose the rocking motion doesn't need to be very much, just enough to frustrate an aimed guns solution, rather than it having an overly detrimental effect on the aircraft's flying ability.  The problem would possibly be more obvious because it's a likely natural escape route for the attacked aircraft, to pull and turn.

 

 

The rocking is not from the slats, it is from the slipstream.  It is more noticeable because the slats are deploying/retracting asymmetrically in a reaction to the slipstream.

Edited December 5, 2013 by Crump

[DD_bongodriver]

The rocking is from the slats opening asymmetrically, why else would it have been specifically noted as such, Brown was explicit in explaining it was the slats causing it and not referring to a phenomenon that is common to all types, another important fact to note is than nobody ever bothered to keep slats in mind for subsequent fighter designs obviously realising the benefits are far outweighed by the disadvantages, the only reason the 109 had them was in anticipation of the adverse low speed handling qualities of such a highly loaded wing.

[Crump]

 rocking is from the slats opening asymmetrically

 

 

Feel free to demonstrate that in the math.

 

The slats work automatically and only provide the lift required. 

 

They are not magic and do "create" lift to induce an asymmetrical lift situation. 

 

The only way the physics allows for asymmetrical lift production to occur is if one slat malfunctions either not opening as it should or not closing as designed.

 

nobody ever bothered to keep slats in mind for subsequent fighter designs

 

Slats are very common on modern fighter designs.

 

Even the first generation Jets had them like the F-86 Sabre.

[DD_bongodriver]

Feel free to demonstrate that in the math.

 

I don't need to, all I have to do is show how you talk in circles......such as.

 

The slats work automatically and only provide the lift required.

 

Followed by

 

They are not magic and do "create" lift to induce an asymmetrical lift situation.

 

But you seem to forget that slats 'DO' produce drag, now you don't really expect anybody to believe that asymmetric drag won't have an effect do you?, think about it, 1 slat pops then that wing drags producing yaw.........now principle of flight basics 101 here, what does yaw produce as a secondary effect?........yep that's right it's roll, and that means the aircraft will roll in to the deployed slat.

 

The only way the physics allows for asymmetrical lift production to occur is if one slat malfunctions either not opening as it should or not closing as designed.

 

you completely forget that the case in point being discussed is how the slats behave in turbulent air, even in free stream air there is an element of asymmetric deployment when in a turn, you have noted it many times yourself by explaining the 'notching' which only comes from the asymmetric deployment, if they deploy in perfect synch then nothing is felt at all, nothing to do with malfunctions or any other weird theories.

 

Slats are very common on modern fighter designs.

 

Not really, sure a few types reintroduced the automatic slat but not common at all, but the point I was making is that during WWII nobody really found the need to introduce slats to piston engine aircraft.

 

Even the first generation Jets had them like the F-86 Sabre.

 

'A' first generation jet aircraft, not all first gen jets, but while we are on the subject it would be interesting to hear the characteristics of them, somebody like an ex A-4 driver would be handy to contribute here, I heard the asymmetric opening

 most certainly produced a roll motion on a A-4.

[Sternjaeger]

so first slats don't produce lift, then they do... Crump, what sort of magic dragon are you flying exactly? How do you manage to contradict yourself within a few posts? It's amazing...

 

Please note that HP-like slats are meant to enhance lift on the wing at high AoA, like the whole aeronautical world says. 

 

Another thing to note: on aircraft like the Tiger Moth, the slats are installed on the top wing, which has no control surfaces, so the benefit is just to enhance lift; on monoplanes like the Bf109 and La5, the slats are installed right in front of the ailerons, providing enhanced lift AND control authority at AoAs.

[HagarTheHorrible]

Maybe the rocking is less a rolling motion and more of yawing effect as the slats pop in and out increasing the drag asymetrically on each wing, even if momentarily, causing oscillations that the pilot can't predict or react quickly enough to.

[Sternjaeger]

yep, it's a combination of forces which is not applicable to all aircraft, hence it's probably something to do with the design of the wing and speeds involved.

[MiloMorai]

Even the first generation Jets had them like the F-86 Sabre.

 

And then got rid of the slats, replaced the 6-3 wing.

[Crump]

 

most certainly produced a roll motion on a A-4.

 

Low Aspect ratio wing prone to tip stall. 

 

It is not the slats that produce that rolling motion, it is just a characteristics of swept low aspect ratio wings.  They tip stall especially in High G turns.  The tip stall will produce a rolling motion.

 

The slat will not produce a rolling moment without a malfunction.  Do the math.

 

 

What's a sensible twist/wash-out for a swept back tapered wing (given sweep, taper, profile data, etc.)?

This depends on what your goal is. If you want to get an elliptical lift distribution it gets very complicated. If all you want to do is prevent tip stall, it gets a little easier but still complicated.

 

http://www.djaerotech.com/dj_askjd/dj_questions/sweepwash.html

 

 

Disadvantage over straight wing

 

 

1. Tip stall from wing sweep and taper

 

http://navyflightmanuals.tpub.com/P-1287/P-12870074.htm

[DD_bongodriver]

Leading edge slats prevent the stall up to approximately 30 degrees incidence (angle of attack) by picking up a lot of air from below, where the slot is large (Figure 3), accelerating the air in the funnel shaped slot (venturi effect) and blowing this fast air tangentially on the upper wing surface through the much smaller slot. This "pulls" the air around the leading edge, thus preventing the stall up to a much higher angle of incidence and lift coefficient. The disadvantage of the leading edge slat is that the air accelerated in the slot requires energy which means higher drag. As the high lift is needed only when flying slowly (take-off, initial climb, and final approach and landing) the temptation for the designer is to use a retractable device which closes at higher speeds to reduce drag.

This can be done in different ways: The slats can be mounted on roller rails so that at high angles of attack they are automatically pulled out by the airstream around the leading edge, and in cruise (at lower angle of attack) they are pushed in. This is a relatively simple system and not too heavy to design, but it has one big disadvantage: in gusty weather only one wing slat may be drawn out while the other stays in, creating a potentially major problem for the pilot who now needs full aileron just to keep the airplane level…!

 

This is from the website of an aircraft manufacturer and are the words of the designer, who presumably attended some form of college to study stuff like this, maybe even has some credentials in the world of aircraft design and aerodynamic studies. http://www.zenithair.com/c-heintz.html

 

http://www.zenithair.com/stolch801/design/design.html

Edited December 5, 2013 by DD_bongodriver

[HagarTheHorrible]

I think that it might be quite simple and in some ways obvious.

 

The attacking aircraft, with slats, charges in to attack target. The victim, surprised, does the natural thing, he pulls and turns. The attacking aircraft try's to follow using his engine power to drive the turn and overcome the excess momentum . The attacker now finds himself in a full power, high angle of attack turn, not quite enough to deploy the slats but not far off. The slipstream coming from the target now complicates things because the air now comes in odd directions making the slats think that the Wing is at an even higher angle of attack causing them to deploy at the wrong time and unevenly as the slipstream moves the air around. A specific set of circumstances but probably a not uncommon situation.

[Zoring]

It's the first time i've heard of it, though it sounds vaguely possible. I remember reading (sorry for not quoting my sources, I would have to find it) one German pilot saying that a lot of new pilots were frightened by the slats (they made a loud noise when deploying apparently) and that you needed to become confident with them to make the 109 most effective, the veteran pilot said that he could turn inside a spitfire with the slats deployed.

[DD_Squawk]

Here's another thought to ponder.

 

With an aircraft in a climbing turn, the wing on the outside of the turn is in fact at a higher angle of attack then the 'inside' wing.   A stall in a steep climbing turn often results in the outside wing stalling first and the aircraft "falling out of the turn" as it were.

 

So... If slats are activated by 'AoA' alone, wouldn't the slats activate asymetricaly in a hard climbing turn, with the 'outside' slat going first, even regardless of slipstream?

 

 

And before we get too deep into 'slipstream'.  It really isn't slipstream that is the problem, but wake turbulence.   Slipstream is the disruption of smooth air from the action of the propeller, while wake turbulence (the real killer) is a vortex generated from the wingtips of aircraft and is most prevalant in high lift low speed configurations.  Think tiny tornado's  extending backwards from the wing tips.

 

These vortex's will definately induce an uncommanded rolling moment, should you be unlucky and get caught in one large enough to effect your aircraft.

Edited December 5, 2013 by =69.GIAP=GRACH

[69th_chuter]

I think I read somewhere that the Digital Nature Engine models slipstream ?

 

If this is the case it will be interesting to see if and how it affects the slats on the 109.  I have just read a bit by Eric Brown about the 109 in which he says "Another problem the Bf 109 had was that it could not follow in a steep turn when using a lot of engine power.  If so, the Bf109 would get into your heavy slipstream and as he has slats on the wings of his aircraft, these would tend to come out and snatch as the airspeed varies. And in these turns when the slats open and close unevenly, a rocking motion develops that ruins your shooting.

 

Presumably if slats provide advantages then they should also model any disadvantages ?

 

 

Actually, if you're following a target aircraft in a tight turn AND in the target aircraft's slipstream you probably don't have guns on target.  For a firing solution you would most likely be turning inside the target aircraft.  The Messerschmitt "slat problem" as I understand it was that you'd be at or near slat AoA ready to or actually firing and rudder corrections, inducing a slip or skid, would pop out (or retract) the odd slat.  You wouldn't have to have slats to have your aircraft upset by wake turbulence (which drift outside the turn anyway).

Edited December 5, 2013 by chuter

[Kurfurst]

The rocking is from the slats opening asymmetrically, why else would it have been specifically noted as such, Brown was explicit in explaining it was the slats causing it and not referring to a phenomenon that is common to all types, another important fact to note is than nobody ever bothered to keep slats in mind for subsequent fighter designs obviously realising the benefits are far outweighed by the disadvantages, the only reason the 109 had them was in anticipation of the adverse low speed handling qualities of such a highly loaded wing.

 

 

 

 

 

 

 

 

 

 

[DD_bongodriver]

WOW.....I stand so corrected you found a few aircraft with slats........and there is me thinking that the 109 was the only one, there you go folks, thanks to the discovery of 8 types covering WWII to the cold war we can conclude everybody wanted slats thanks to the 109.

[HagarTheHorrible]

I see you've included a Me 410 in the list of photographs of aircraft with slats.  Eric Brown said some very unpleasant things about the flying qualities of the 210/410 and despite the fact that it has slats he still said "  they made every mistake they could.  It would go in a spin if you mishandled it in the least - it was that sort of aircraft. And it made you feel you were on a knife edge all the time.  And the Me 410 was supposed to be an improvement on it, but I can assure you it was minimal"

 

Here is a pic of the aircraft that Eric probably tested while he was at RAE Farnborough in 44 (The top one obviously)  I don't know why but the British example just looks a little flaccid compared to the Soviet one

 

 

I think the slats on later Soviet fighters were added to an established wing design to cure unpleasant behaviour, maybe the 109 was the same, rather than designed like that from the outset, it wasn't so much a question of "Hey this will make our aircraft brilliant" rather than "Maybe if we strap this to the front edge of the wing it might stop the damn thing from falling out of the sky quite so often".

 

Just thinking out loud, would a jet wash have the same slipstream effect on leading edge slats as prop wash ?

 

While I was thinking about this whole slipstream thing it got me wondering about the nature of the BoS engine.  Let's imagine for a moment that Eric Brown is correct and that one of the downsides of slats is this problem of following another aircraft in a climbing turn.  Now lets imagine that while not a serious problem it is another complication for the pilot to consider, in much the same way as aircraft fitted with carburettors had to roll inverted in order to dive without starving the engine of fuel (that is until Ms Shilling showed everyone her orifice).  We obviously know that our computers can't simulate all the vagaries and complexities of flight so we have a simplified set of calculations that our computers can handle.  RoF and BoS are unusual in how they model flight in that they use a physics based engine rather than simply using a set of numbers.  What if the simplified physics calculations didn't adequately differentiate between different aircraft and you end up with a the only differences being  the basics such as speed, climb, roll etc, imagine if the cutting out of an early Merlin engine was physics based and the physics calculations weren't complex enough or detailed enough to differentiate between injectors and carburettors.  The whole folk law of the BoB wouldn't be adequately represented.  I appreciate that, that is a daft example but hopefully it illustrates the point.  If it were the case that the physics engine wasn't complex enough to differentiate between the minutiae of good and bad behaviour do the Dev's have to add in non physics, table based characteristics to support the physics engine ?

Edited December 5, 2013 by HagarTheHorrible

[DD_bongodriver]

Just thinking out loud, would a jet wash have the same slipstream effect on leading edge slats as prop wash ?

 

Not really, prop wash is more disruptive because it rotates the air like a corkscrew, jetwash is more a problem in terms of air density, hot jet gasses have a lower density and will reduce the efficiency of anything aerodynamic entering it, but you'd have to bury your nose in the jetpipe to really be affected, I'm guessing the military pilots in this forum could shed more light on that issue as encountering jetwash is probably more of an issue for them (of course we all learned how flying through jetwash will cause a flameout and send you into a flat spin from Top Gun  ), all aircraft leave a slipstream (wake vortex) which is the most significant problem, it's never a great idea to fly into somebody elses wake, it can get quite rough, it still surprises me how much of a jolt you can get flying through your own wake doing a 360 degree level turn.

[Sternjaeger]

I can confirm that: I once ended up in the slipstream of a Canadair with a Kitfox. It was not fun at all.