So.....how exactly does the fact that the venturi effect caused by the 'slot' created by an open slat which re-energises the boundary layer of air over the wing maintaining smooth flow (sometimes called laminar http://en.wikipedia.org/wiki/Laminar_flow ) prevent you from understanding what I meant?

While we're discussing this so civilly perhaps you could explain to us all this magical phenomenon that prevents a slatted wing from stalling once it has gone beyond its allowable angle of attack?

You are not discussing anything civilly...you are just making insults.

First of all, you do not understand the fundamentals of LE slat aerodynamics.

Quit using wikipedia as your source. It is not credible and in this case is just plain wrong as the author does not understand boundary layer mechanics.

In boundary layer mechanics, we have two portions, laminar and turbulent.

Laminar flow is the last thing you want on the outboard portion in a stall. Laminar flow is low energy. That is why it is low drag AND subsequently, low lift.

Slats work by increasing turbulent flow not laminar flow. Turbulent flow portion of the boundary layer is high energy and high lift!

optfly.iaa.ncku.edu.tw/aftdesgn/lect16.pdf

The laminar flow is not the purpose of the slats, it is the increase in turbulent flow boundary layer which delays the onset of the stall.

No stall = NO SPIN! Hence, the spin resistance found in slats and the reason engineers used them as an early anti-spin device.

http://imageshack.us/a/img856/5310/s...istance.th.jpg

http://imageshack.us/a/img846/4238/s...stance2.th.jpg


They are spin resistant because they allow for control inputs that would normally result in a spin. One can easily see this in the RAE report.

While there are a number of devices that delay the stall, in the end if you push it too far, you will stall.

Of course a stall by itself doesn't result in a spin.

It is very, very rare to find an aircraft of any type that cannot spin. I only have experience of one type of Glider that could fit that bill and am confident that aircraft of the 1930/40 era would have to be specially designed.
The Me 109 isn't one of those aircraft. I don't disagree when people say that it was a difficult aircraft to spin and that the model is wrong, but go to the extream and it will depart.

I am being very civil, if you have taken insult from that then I believe you are a touch over-sensitive......I believe that comes with instability ;)


Now that is an insult. :rolleyes:

Oh come now, that 'Stop using Wikipedia as a source' is too cliche, used as a cheap attempt at discrediting in many internet debates, there is nothing wrong with that article.

http://history.nasa.gov/SP-4103/app-f.htm

I suggest you read this article, it will help you understand boundary layers and the effect of skin friction and subsequent separation due to turbulence.

Extracts from the article......I hope NACA are a more credible source for you rather than wikipedia.


Spin resistance is not anti-spin.....anti would suggest there is complete protection and that is simply not the case.

in case you were doubtfull that slats are a boundary layer control device heres more stuff from NACA..

http://history.nasa.gov/SP-367/chapt4.htm


Vortex generators are using a completely different method, the 'turbulence' they are creating is simply in the form of vortices to draw in energy to a portion of the airflow.

http://www.aerospaceweb.org/question...cs/q0228.shtml

http://www.aerospaceweb.org/question.../generator.jpg







Now hopefully you will be able to explain to us all exactly what are the mechanics involved in complete stall/spin avoidance once a slatted wing has been taken beyond it's maximum angle of attack?

I haven't read Crump literally.

I've read it as:

"Slats are an anti-spin device in that they extend to prevent the wing stalling, thus giving a pilot a chance to avoid a spin when non-operation of the slats would cause a stall and a possible spin. They also slow down the stall so there is a greater chance that the stall does not result in a spin."

Like ABS. It's a device to stop you skidding. It doesn't mean it'll stop you skidding in every situation though.

Who was the Finnish 109 pilot who said they don't know what happened in a stall/spin because they never stalled/spun?

And isn't this getting away from the original topic, which is do they have any effect in this game?

Hood

Slats are or should I say were in the 1930's/40's primarily a device to improve low speed handling qualities and cannot be anti-spin, the only true form of anti-spin is propper handling of the aircraft, slats simply make the behaviour at stall more benign but their effectiveness has a cut-off point beyond which there is nothing to provide these protections, in high speed manouvering the chances of exceeding those limits are much higher.

I believe the relevance of these extended discussions to the original subject is to do with what some people are expecting from the effect of slats, the original question I believe is almost impossible to answer without being able to disable the slats, and that is subject to whether they are actually coded as separate devices as opposed to the FM being modelled with simple wings that reflect performance with slats.

Slats are an anti-spin device. What is so hard to understand about it?

If you have ever flown an aircraft with slats, you can immediately notice the difference in slow flight and stall behaviors.

Here is the slats in my old airplane:

http://www.youtube.com/watch?v=-vbqgfjyW2Q

Slats are NOT an anti-spin device...what is so hard to understand about it?

I have flown aircraft with slats....have you?

Right, now ask someone to make a video of the same aircraft doing high speed stalls taking the aircraft beyond the limiting angle of attack and we can compare the results.

Now your trying to morph the discussion into something else.

You keep confusing "anti-spin" device with a spin resistant airplane.

Spin resistant airplanes employ anti-spin devices such as wing cuffs, LE slats, and slots to build spin resistance.

What you are missing is the ability to put it all together. If we were talking about the entire wing being able to stall at once, then the airplane will enter a spin.

It takes a lot of work to do that in a Bf-109 by design.

First of all, only the outboard portion of the wing receives the benefit of the slats in the Bf-109.

In any airplane, the most desirable stall progression is for the wing root to stall first and the tips to stall last.

This leaves the wingtip unstalled and the ailerons effective.

The next feature of the slats is the automatic deployment. Air pressure operates the slats and they will deploy to exactly the position the wing requires for a given condition. That is why in a skid, they will asymmetrically deploy. For some reason, gamers tend to think "asymmetrical" deployment of the slats is a bad thing, it is not unless there is a malfunction of the slats. Instead, the slats deploy to exactly what the wings need automatically and unless the pilot looks out and is somehow psychologically disturbed by seeing the slats out at different amounts, the airplane skids normally without noticeable effect.

The last feature in the Bf-109 is the elevator control is set up so that with the wing root stalled, the pilot cannot continue to raise the nose. The Socata Rallye is designed that way as are many aircraft.

The designer uses control design to keep the pilot safe by limiting the moment the elevator can produce about the CG. This way, the wing tips remain effective throughout the stall. Cessna does this in a C-172 as well. Again, it is a common feature in a properly designed aircraft.
Now, Mtt did have to demonstrate spin entry and normal recovery in the Bf-109. They did this by adversely loading the aircraft to its rearward CG limit and modifying the slats to be pilot controlled. In other words, the airplane was at its rear most CG limit and the pilot could lock the slats so they did not deploy.

:confused:

That is my airplane and I am at controls in the film.

:rolleyes:

if you say so, hardly evidence though is it, a medium level turn pumping the elevator to make slats deploy.

I'm pretty sure I'm not the confused one in this discussion.....anyway...carry on.

Can I stop you here again....sorry but anti-spin would mean spin proof, resistance implies it's not proof, you know like waterproof vs water resistant, none of those devices can be considered a proof against spinning.

and here finally (in bold) is the first bit of credible understanding you show, but subsequently you have exposed the real protection in this case to come from blanking the elevator, you do realise you have just excluded the slats completely from the equation, given that you could design an aircraft without slats that puts the elevator into the turbulent flow and it would have exactly the same pitch limiting effects, the side effect of that is you seriously limit the manouverability......is this starting to make sense or what?

wait a minute...MTT had to lock the slats but still had to put the CoG back too? why bother with the CoG? sounds to me like there was some crazy black magic going on with that aircraft and spin resistance had nothing to do with slats.....more and more NZTyphoons recently deleted comedy poster is making sense.

The logical result of your position is that aircraft with slats cannot spin as they are anti spin devices. Are you really sure that is what you are saying?

As a CFI you cannot seriously say that is a fact. The slats are a device that delay the stall, but pushed too far will stall. It doesn't stop a spin.

The Glider I flew that cannot be spun is a K21, it doesn't have slats, but it certainly could be stalled. If anyone is interested we used K13's for spin training.

from my paragliding lessons i learnt an stall is not an spin but falling like a rock due to lose of dynamic sustentation by going to slow

in the past someone would say that with stalls off the game is more realistic(il246) which is an interesting point

Salute

For whatever reason, this is a pattern which we see again and again on these boards.

With the same protagonist on one side.

I believe Crrump has some valid points, however the insistence on an 'all or nothing' argument is not useful.

For the record, I understand the following. Feel free to correct me.

1) The low wing area, hence high wing loading on the 109 was an attempt by the designer to reduce weight and drag to increase overall speed and climb. This fit with the most important goal listed by the RLM, ie. an interceptor which was light enough to climb to altitude quickly, and fast enough to catch the modern stressed skin monoplane bombers which were beginning to arrive in the early '30's. Turn capability was very much of secondary importance. At the time of the competition, newer bombers were faster than the existing generation of biplane fighters which were common at the time. A secondary preferred requirement of the competition was a fighter which could be easily transported by rail. The removable wings on the 109 were a design feature intended to satisfy this requirement. At the same time, these removable wings created another issue, that being the requirement to attach the undercarriage to the fuselage, with the result being the off camber wheels, with their inherent instability in landing. This instability would be exacerbated in high speed landings.

2) As a result of the small wing area the aircraft, if equipped with standard slat-less wings, and without the modern flaps which were an innovative part of the 109, would have had a very high stall speed. The stall speed for a 109 without slats and flaps can be estimated as roughly the speed at which the slats on the historical aircraft open without the flaps down. In the case of the 109E3, the RAE test showed with flaps up, the slats opening at 120.5 mph, 25 mph higher speed than the 95.5 mph actual stall speed. With flaps down, slats opened at 100.5, 18.5 mph faster than the 88.5 mph stall speed with flaps down. A landing at 120.5 mph would by the standards of 1934, be unacceptably high. Especially with the wheel instability issue. Messerschmidt obviously understood the issues of high speed stall brought with his high wingloading, hence the installation of the slats and modern design flaps, with their improvements to low speed stall performance.

http://www.kurfurst.org/Tactical_tri...s/image011.jpg

The primary goal of the slats and the flaps was to reduce stall speed to a manageable low speed, and thus allow safe controllable landings on the off camber undercarriage.

A secondary benefit was the improved low speed maneuverability, and lowered stall speed the slats gave with landing flaps up. This was not the primary goal of the devices, it was welcome additional benefit.

To suggest the primary design goal of the slats was a 'spinless' aircraft is stretching the point considerably, and is not supported by the historical documentation.

At the same time, there is no doubt the slats did give much more benign stall characteristics to the 109 than many other aircraft. Under the control of a pilot who reacted appropriately to a stall, there was very little chance of a spin occurring. Under the control of a pilot who ignored the requirements for stall recovery, the aircraft was undoubtably capable of entering a spin. Spinless?? I don't think so. Easy to recover from a stall? Yes.

Finally, this entire thread has gone so far off track in order to satisfy the viewpoints of posters that it is missing the original point.

Does the game 109 replicate the characteristics of the historical aircraft?

No, it clearly doesn't. Among other mismodelled characteristics, the tendency of the 109 to easily enter, and be difficult to recover from, spins, is clearly wrong.

First is an abridged lecture given by Frederick Handley Page describing the operation of what are, in fact, called automatic slots - the slats are simply the moving airfoil sections.

http://i91.photobucket.com/albums/k3...1-page-001.jpg

http://i91.photobucket.com/albums/k3...2-page-001.jpg

and, from 1939:

http://i91.photobucket.com/albums/k3...page-001-1.jpg
http://i91.photobucket.com/albums/k3...page-001-1.jpg

Operative words "the slot could be made to open at a pre-determined angle of incidence....make the wing stable at a large angles of incidence and so ensuring that, although the aircraft would stall, it would not "drop a wing" and go into a spin."

Therefore, automatic slots are not fully effective at all AOAs at low speeds, let alone combat speeds - which, BTW, have not been mentioned - until the wing has reached a certain, pre-set angle of incidence. What was the pre-determined angle of incidence for the 109? And at what speeds did the slots open?

Effectiveness v basic airfoil:

http://i91.photobucket.com/albums/k3...-page-001a.jpg

Most of the questions you are asking have been answered by the chart in the post above yours.

The chart you have provided showing effectiveness vs basic aerofoil is quite dated, and I am not sure it can be taken as effective.

NACA did a later, more comprehensive study of wing lift devices, including leading edge slats, I have a copy somewhere in my files, and there should be a link at the NACA site.

The intention is to show some of the literature that was around at the time the H-P slot was invented. The table dates back to 1933 so, of course it predates the NACA data, but it was the type of material that would have been available at around the time that the Bf 108 and 109 were under development.

What I should have asked is at what combat speeds were slots effective? The data shows they opened at speeds ranging between 90-120.5 mph, but I doubt that a 109 in combat slowed to those speeds.

Afaik the deployment of the slats is dependent on the aoa, not the speed, so the slats might very well deploy in a tight turn at combat speed.

Yes robtek is correct here, slats operate as a function of AoA and that remains a fixed quantity but there is means of calculating what speeds slats would open under certain loads.

At any time Lift(L) equate Weight (mg)

Hence during a turn at X nbr of g the total lift of the plane is L=Xmg

Let's assume the simple flows theo of thin wing with no camber (flat wing) where CL=2Pi()Alpha where CL is the coef of Lift (L/0.5roV²) with V the speed of the air and ro the volumic mass of the air

Then Alpha=Xmg/(2Pi()*0.5roV²) and V(alpha)== SQRT(2Xmg/Pi()roAlpha)

hence for a given alpha at (let's say) 1.5 stall speed and 1g, the speed at witch slats will deploy is augmented as the square of the G ratio.

hence at 4G the speed is the double. AT 8g, teh speed is three time more.

Etc.. etc..

Regarding the 109:

-Slats are deployed in front of the ailerons in order to keep ctrl at stall conditions. No wing drop (and full airflow around the pouter portion of teh wing), no asymmetric stall . Hence no spin. This is why Crumpp refer it as an anti-spin device. So Crumpp was right (again...)

-The 109 undercarriage was not build that way to facilitate it's shipping via train (at least not only - but this is the first time I think that I have to read it). It was made to make assembly easier with the wing being plugged onto the fuselage. Remind that Bf (and not Mtt at the time ;) ) did not have the production facilities that would be needed for such a big order by the RLM. Many parts were subcontracted (heinkel etc...) and had to be moved from one facility to another. Having the fuselage "crated" by its own undercarriage as soon as possible facilitate the production and made the wing stronger for a given weight (and Mr Messer was addicted to weight reduction as any good eng shld be!).

- Providing early 1930's document is a bit risky to prove a given argument in aero term. As I hve alrdy said many time there was a revolution in 1935. And this flow slowly ard the globe from Germany then USA and all obver the globe after 1945.

Humm forgot the wing surface above. As it is a cte in the relation V=f(alpha) there is no impact on the overall result.

And it seems I was way too short in my explanation abt the revolution in aero theo in 35. For one time NZ, don't bounce me too hard on tht one :rolleyes:

Wurster slowed down, pushing back the throttle to idle. As the Bf 109V2 slowed, the automatic leading-edge slats deployed and the warning horn sounded in the cockpit. The controls gently shuddered. The plane was now on the edge of a stall. With both the rudder and ailerons ineffective, the control stick going forward towards the instrument panel, he pushed the nose about ten degrees below the horizon. The left wing dropped and the aeroplane went into a spin. (...)

V2!

Same wing, same slats.

Excellent story....

Might want to do some background research on the design.

;-)

Nope....

I am not saying 'identical', I am aware of the small differences of earlier and even later models but the slats are slats - they do have same function and effect, have they not? Were the early 109s V-2 including not 'spin-resistant' even when they had the (same) slats? :o

Comparsion of the V-2 and E-3 wings:

https://dl.dropbox.com/u/10668862/misc/109w.jpg

Crumpp
What do you tell your students about leading edge slots? Do you tell them:-

a) That they are devices that delay the stall or
b) That they are anti spin devices

Just wondering

Its funny isn't it, when they're arguing about the wings the V2 is different beyond all measure to the E3, but when they were talking about the top speeds, they were identical.

:rolleyes:

Then why is washout not automatically considered an anti-spin device? it has exactly the same function, to prevent the outer portions of the wing from stalling and maintain aileron effectiveness during the stall and prevent assymetrical stall, if you do consider washout an anti-spin device then what makes it inferior to slats?

so why is it that 2 aircraft with 2 solutions to the same problem (Spit/109) apparently have totally different behaviours? is it really because of the elevator design on the 109 which prevented the use of pitch at stalling angles? or perhaps the design was too stable (see RAE report) which meant there was not enough elevator authority?
either way it seems you get 2 choices here, either the 109 was able to turn well (and possibly suffer a spin if overdone) or you have limited elevator authority which impedes manouverability.

Washout does not energize the boundary layer....

neither do slats once they have gone beyond maximum angle of attack and stalled........

Still Wondering

Crumpp
What do you tell your students about leading edge slots? Do you tell them:-

a) That they are devices that delay the stall or
b) That they are anti spin devices

Just wondering

The section of the wing close to the wing roots have alrdy stalled at that time (pls refer to the diag that has been alrdy posted on another similar topic). Hence the stall has alrdy occured before the slotted portion of the wing has stalled!!!

It's all abt having such device.

Washout is good but produce a lot of drag. Accetable for a GA aircraft but not good for a fighter! It's one of the raison why the Spitty was so slow!

Right, they don't fly to the moon either despite being an anti-spin device.

What that has to do with anything, I don't know. Maybe it is significant in your mind?

What they do is energize the boundary layer by increasing the high energy turbulent portion so that stall is delayed significantly compared to plain airfoil.

Twisting on the otherhand, simply moves the angle of incidence a few degrees.

Go back a few pages and look over the definition of "spin resistant airplane".

Maybe the light bulb will come on for you and maybe not?

I have seen several sources which say the requirement for train transport was listed by RLM in the competition. Yes, Bayerische Flugzeugwerke was compelled to outsource many of its manufacture, but that did not require a design which had the undercarriage mounted as it was.

Suggesting an aero revolution occurred only in Germany, and spread from there is not accurate. In fact, modern designs were being created in many other countries at the same time as the 109, some of which could be called further advanced, some less.

And further, many of the design elements of the 109 were taken from many other aircraft, i;ncluding those from outside Germany. To suggest these elements originated only in Germany again is inaccurate.

Aircraft design in the early '30's, as it is today, was a process of osmosis, with ideas and innovations rapidly circulating and moving from one location to another.

The drag profile for the Spitfire showed the majority of the drag was a function of its radiator placement, not the washout.

And are you suggesting slats don't produce drag? Any device this size extended into the airstream below the wing is obviously going to produce a very large amount of drag.

Even when the slats are not extended there was drag.

And the 109 wing's tendency to early compressibility was partially a function of the slats being present.

If you haven't seen it, then time to look at the following analysis, by an engineer who was on the Messerschmidt design staff:

http://www.wwiiaircraftperformance.o...ner-Me_109.pdf

when it comes to defining resistant I think you provide the perfect example.

Heres a really nice and simple way to illustrate this for you...you have pitched up in your 109....inboard section of the wing begins to stall and the lovely slats have deployed keeping you nice and safe....you keep pulling and your angle of attack is still increasing (even for the magic outboard section of the wing).....now you have pitched so much that you have stalled the outboard section of the wing because you have gone beyond the maximum angle of attack the slats allow.......please explain from this point what magic force is in place to prevent a spin.

Now if you are sticking with the 109 elevator being unable to provide enough force to pitch beyond that point then you have:

1. eliminated the slats from actually being the main protection.
2. just highlighted exactly why the 109 was inferior in turn performance.

I see that not even NACA managed to educate you on the real mechanics behind boundary layers.....go back a few pages and you will see how they completely contradict your theories.

now what washout does is because of the physical twist in the wing putting the tips at lower incidence, the outboard sections of the wing remain unstalled when the inboards are stalled because the outboard sections are at a lower angle of attack.....which means the boundary layer is still adhereing to outboard section ofthe wing (because they are NOT stalled), airflow is still flowing over the ailerons making them effective...pretty much all the same conditions that are applying to the 109.....now if only there was some way of preventing pitching beyond critical angle of attack my Spit would be unspinnable.......no stall = no spin remember.

Trust me...my lightbulb is on AND I'm home too.

C'mon a lot of modern fighter use slat and are supersonic. I don't see any link.

More over when you hve 1000hp in front of your airplane you don't care that much abt low speed drag (but to weight).
Washout are draggy during cruise (range) and when you attend your max perf range.

Ok enough of this especially after your argument abt going into the stall after your plane is shaking during a fight (but no mention here from you abt stick travel and af Cg huh).

Don't you mean drooping leading edges.

Let me fix that for you as it the highlighted portion is the source of your confusion on this issue.


Why don't you schedule some flying lessons and explain to the instructor how the elevator can increase angle of attack AFTER the wing is stalled.

As are the rest of us..

But I suspect Crump will avoid answering this question because any atemp in doing so will only highlight how silly his position is on the matter.

Really? that's the best you've got? instead of answering the question you just keep playing the 'why don't you go take flying lessons because I don't need to because the movie TOP GUN was all about me'?

Heres a nice link to some material us actual flying instructors use..

That bit again..

taken from GAPAN (Guild of Air Pilots and Air Navigators)..

www.gapan.org/file/666/teaching-stalling.pdf

Home website..

https://www.gapan.org/

I should remind you that slats deploy before the main wing has actually stalled which makes my original text quite correct thanks.

While were at it perhaps you could educate us all on exactly what phenomenon takes place that renders elevators inoperative when the wing is stalled? I'm pretty sure if there is airflow over the elevator then it has something to create a pitch force with

Heres my ORIGINAL question without ammendment as it's the one that makes sense and highlighted in BOLD is the part I'd like to know more about.

please, no more cheap insults or suggestions I need to educate myself, that stuff gets old real quick, just answer my question.

Thanks in advance.

If I ask the flying instructor the following what do you think the reply will be:-

What do leading edge slots do, do they:-

a) Delay the stall or
b) Are they anti spin devices

Just wondering if my flying instructor give the same reply, that you who has told us is a CFI would give.

My money is on (A) what do you think?

Modern slats may be intended to achieve improvements in lift at low speeds in the same way as the 109's slats, but they are not all the same design as the 109's. Gaps are almost imperceptible in comparison to the 109's when not deployed, when deployed, they move forward almost seamlessly, there is nothing in the way of the large open gaps displayed by the 109's slats when deployed. Modern leading edge flaps are a completely different system. These modern leading edge flaps are also computer controlled, with a degree of sophistication in their deployment which makes the 109's slats appear crude at best.

Slats of the 109 era do confer some benefits, but they also impose penalties.

To deliver spark to an engines combustion chamber, we use a "spark plug"! Does it plug up the spark? NO, it is just the name of the device used to provide an ignition source.

When we design a spin resistant airplane, we use anti-spin devices to build that spin resistance.

Because folks do not understand the technical terminology, which I been nice enough to explain which is unfortunately lost in the zeal to prove me wrong by a small select portion, the community ends up with all these pointy-tin foil hat theories that have nothing to do with the spin resistant design of the Bf-109.

:confused:

You must be trolling in this reply.

LE flaps are completely different in the aerodynamics from slots or automatic slats.

LE flaps change the camber of the wing and slots/automatic slats energize the boundary layer.

Do you know what a camber change means and how it looks on the polar? A camber changes shifts the entire polar to the left. This has the effect of producing the same coefficient of lift at a lower angle of attack. TE flaps are also camber changers and this is the primary reason we use them on landing. It allows the nose to be lowered so the pilot can see the runway without sacrificing coefficient of lift. Depending on the design, the flap can also raise the maximum coefficient of lift but this too will shift to the left on the polar.

While they are both high lift devices, you are comparing apples and oranges so your post makes no sense at all.

Let's call them fish blankets instead, that should avoid any confusion :rolleyes: we are after all all talking about the same device, but just out of interest are you really saying that anti-spin is somewhat of a mislabeling for their actual function?.....or in essence admitting your own pointy tin foil hat zeal to claim the 109 as unspinnable is flawed?

Salute Crrump

You clearly haven't read the post which I was responding to.

I do not say the 109 era slats were equivalent to modern era LE flaps, that claim was put forward by Tomcat. In fact I was pointing out the big differences between these devices.

On the issue of 109's entering spins: It's clear your insistence, against all the evidence presented, that the 109's slats made the aircraft "spin proof", is simply not factual. Do they lessen the chance of a spin? Yes, I doubt anyone here would disagree.

However, this does not seem to be enough for you.

We are now in the usual counterproductive and meaningless back and forth which always seems to occur when you enter a thread.

Whether or not other posters agree partially with your arguments seems to make no difference, you seem incapable of accepting the central concept of healthy debate, that being differing viewpoints allow an arrival at a conclusion which may not agree with either side's starting position.

Without any apparent willingness on your part to consider other viewpoints, there is point to further discussion.

Taildragger can you explain what reducing the angle of attack to prevent a stall has to do with your claim of raising the nose on the BF-109 with the elevator to completely stall the energized boundary layer of the tips while the rest of the wing is stalled?

I don't see the connection.

It is not my confusion, Taildragger.

Like I said, it is not the first time that terminology has been explained in this thread.

He is right, many modern fighters do use automatic slats. What is the issue??

Look Buzzsaw, the act of spin proofing an airplane by the application of anti-spin devices builds a spin resistant design. Are you confused by the terminology??

http://forum.1cpublishing.eu/showpos...2&postcount=67

That was page 6 and you never answered my question on why you leaped in spouting the same exact thing I said!!

I asked you in your first post Buzzsaw to clarify what you think I exaggerated which is your claim and to point out exactly your point of contention.

I have asked you several times. Do that and we will clear it up.

There won't be any conflict just be honest and let's get the facts out.

It is pretty obvious most posters in this thread do not know the terms and confused them.

Do you actually read the posts people respond to you with? It is apparent you have great difficulty grasping the context of many of them, so I will need to explain my perfectly clear and highlighted in bold quote was saying the elevators remain effective in the stall, did you get that? The elevators remain effective in the stall......now if you have effective elevators you have the ability to pitch beyond critical angle of attack, now are going to stick with the theory that the 109 had some form of pitch inhibition?

Ok taildragger,

Do you understand that the basic effect of the slats is to add energy to the boundary layer and delay seperation?

On the lift polar, the slats have the effect of extending the lift polar increasing both maximum co-efficient of lift tied to that, available angle of attack. This is a completely different effect from increasing camber, btw.

The wing stalls at a higher angle of attack with the slats deployed.

The plain airfoil cannot reach that same angle of attack and is stalled while the tips continue to fly. When the plain airfoil, which makes up the majority of the Bf-109's wing is stalled, the pilot does not have enough control to raise the nose and stall the tips which do gain the benefit of the slats.

Study the diagram below and explain to me how the plain airfoil can continue to fly and reach the slated portion CLmax??

Under normal operating conditions

Now is pulling hard turns in combat 'normal operating conditions'?

OK....:confused:

Come on and let's do some stalls.

You try to keep the nose up with elevator!!!

:-P

You understand the aerodynamic center in a normal stable airplane is behind the Center of Gravity. When our wing produces less lift, the reduction in aerodynamic force on the aerodynamic center causes the nose to drop. It is not hard to size the elevator appropriately. In fact, the forward CG limit is defined by our inability to raise the nose at landing velocity (not Vref, flare).

No, you explain to me what the phenomenon is that prevents the still effective elevator from allowing you to pitch beyond the slatted portion of the wings maximum angle of attack.

:confused:

For a fighter, yes!!

Read the RAE report, guy!

I have explained three times already. It just does not sink in!

You haven't explained why there is no authority for a start, now can you explain to us the phenomenon that allows a 109 to maintain a tight turn in combat despite apparently it's elevator being rendered ineffective as soon as the inboard section of the wing is stalled?

So you are basically disagreeing with GAPAN?

No, you are!!

:-)

The elevator can certainly reduce the angle of attack. That is pushing down, taildraggernut NOT pulling the nose up.

Once the angle of attack is reduced, Pitch + Power = Performance and our speed increases which allows us to use the elevator to RAISE the nose once we have some speed.

What that has to do with your claim of raising the nose with the elevator at the stall, I cannot imagine.

Wow you just don't get it, if the elevator is EFFECTIVE then you can control pitch both ways, what you just don't appear to grasp is the actual reason an aircrafts nose drops once the wing is completely stalled, that is simply because once stalled there is no pivot for elevator forces to act upon, all the time there is even the slightest portion of the wing still flying then the elevator has effect, only once the wing is FULLY stalled does the elevator run out of authority, once a wing is FULLY stalled inboard outboard and slats what is the protection against spinning?

Taildraggernut, if the elevator is so effective in a stall, why do power on stalls sometimes result in a nose up attitude descent??

Take a wild guess!

As highlighted by my example of the K21 glider, which you can easily check, it is possible to have an aircraft that cannot spin but can stall.

There is of course a world of difference between a spin and a stall. The leading edge slats delay the stall and give the pilot greater control resulting in an aircraft that is more difficult to spin.

The leading edge slats DO NOT STOP THE AIRCRAFT FROM SPINNING.

When teaching the stall I used to fully stall the glider then encourage the student to do what they liked with the controls for a few seconds and nothing would happen. Soon gravity would take over the nose would drop and authority is regained.

The period where the controls have no authority is very brief. One of the most dangerous events in a glider is a cable break on a winch launch at a low altitude say 100ft. The forces on the glider tend to 'throw' the nose up and without immediate action, its possible to be almost vertical with no momentum. As a result a serious quite probably fatal accident is basically certain. Students are taught that as soon as the cable breaks to immediately push the stick forward to its max before releasing what is left of the cable from the glider.
I mention this as it shows the controls are effective for all but a few seconds while the wing is fully stalled. However swift action when there is any airflow over the wings normally stops this happening. Even if the wing does fully stall and the conrols lose their effectiveness, then the momentum gained in the immediate actions prior to losing authority ensure a safe recovery.

In normal parlance an Anti Spin device is one that makes the recovery from a spin easier such as an anti spin strake, or a recovery parachute. They don't stop the aircraft spinning, they help with recovery.

Something that helps the aircraft maintain control such as a leading edge slat help delay the stall. again the two are not the same.

Which brings us back to the question which you refuse to reply to in simple terms.

Do you tell your students that the leading edge slats:-

a) That they delay the stall or
b) That they are anti spin devices.

Delaying a stall is not an anti spin device unless it helps the recovery from a spin.

Which brings me to a second question. Why does someone who says that they are a CFI need to be told something as basic as this?

PS don't try to impress by including a copy of a licence. I can understand not wanting your licence no or name to be broadcast, but why delete the expiry date when its only recently been issued?

Well one of the most OBVIOUS reasons is because you have POWER ON you are creating PROPWASH which acts on the ELEVATOR making it even more EFFECTIVE, now can you tell me why even in a POWER OFF stall some aircraft can 'mush' down in a NOSE UP DESCENT?

I'll save you the bother as I don't think you actually could answer it without consulting google.

when you have made a smooth and progressive decceleration down to the aircrafts 'minimum' stall speed in level flight you will find you are using 'maximum' deflection of 'up elevator' to maintain attitude, because your airspeed is so low and you have used up all elevator travel you run out of pitch authority but the aircraft has found equlibrium with the EFFECTIVE elevator at max deflection holding the aircraft at it's maximum angle while the minimum airspeed is still sufficient to maintain the elevators EFFECTIVENESS to hold the attitude, the nett result is you hold the aircraft in a stall with a constant pitch moment about the lateral axis thanks only to an elevator which is still EFFECTIVE, now here is the really salient part, it's thanks to things like washout, slats, slots etc etc that ensure the outboard sections of the wing stalls last that prevent the aircraft from making a complete departure and entering a spin, even a Spitfire should be able to carry out that excercise due to it's washout maintaing that lateral stability.

Heres our dear old friends the NACA to explain it all to you.

Spitfire MkV handling trials........I wonder if these have been shown before? :rolleyes:

https://docs.google.com/viewer?a=v&q...hUeuiqgiZzKi2g

please forgive typos in my quote as I am cutting and pasting text from a PDF image.

Again..

I should really come back to some qualities of the 109 here from this quote from the RAE report..

The part in bold is describing a stall with the incipient stages of a spin, so in this case the evidence shows that slats have absolutely failed in prevention of the condition, the BIG factor here is that the slats DO make facility for an almost instantaneous recovery almost of an automatic nature.

Yes the propwash gives just enough elevator force to balance the AC keeping the nose up, however as an airplane control, it is NOT effective.

It is one of the cautions pilots should be aware of in a power on stall and accidents have occurred as pilots did not realize they were stalled, experiencing a loss of control until impact with the ground.

http://www.langleyflyingschool.com/Pages/Stall.html

Why would a designer allow a pilot to take an aircraft someplace it cannot fly anyway??

The information is blanketed so my personal details do not become privy to the internet.

There is no such as thing as "not recently issued" CFI license, Glider. The certification is only good for two years in the US and is re-issued at that time.

Notice it has a separate certificate number and is only good when accompanied by my Commercial certificate. You have to carry both and cannot fly with the CFI certificate alone.

The rest of your stuff is just a repeat of the same question I have answered so I have to conclude you are only trolling at this point. Obviously, you cannot accept the answer I have given you twice already. That is your problem and not mine.

As they say, you can lead a horse to water but you cannot make them drink.

http://img854.imageshack.us/img854/1...esistance4.jpg

http://img259.imageshack.us/img259/1...esistance3.jpg

http://imageshack.us/a/img856/5310/s...istance.th.jpg

http://imageshack.us/a/img846/4238/s...stance2.th.jpg

LOL, you very conveniently emphasize only the facts that fit your world without considering the final conclusion of the RAE.


Yes it does describe the conditions a spin should result in!!

Thank you for recognizing that!!
However your conclusion is not correct.

As evidenced by the RAE report:

Which is the normal effect of Handley Page automatic slats....

No the propwash allows you to make excessive pitch input due to increased effectiveness of the elevator and preventing the natural tendency of the aircraft to drop it's nose and recovering, this is why power on stalls give a greater chance of wing drop because you are able to hold the aircraft attitude beyond critical angle of attack.....it also answers this question of yours...

because in this case if a designer didn't wan't to give you the ability to go beyond the flight regime he wouldn't have put an engine in and for that matter he might not have given you facility for 'any' control of the aircraft as it also gives you the chance to screw up, so why did the designer even bother with wings?

it's amazing you can say this yet clearly understand none of why it is so.

http://www.langleyflyingschool.com/Pages/Stall.html

From your own source......whoever Langley flying schools are.

Describing a POWER OFF stall.

Now if as you suggest that during a power off stall the elevator has become completely ineffective how exactly is the pilot expected to use such purposeful and smooth recovery inputs? shouldn't it be the case the elevator input is now redundant according to your theory? you can only purposefully operate an effective control, if it is not effective then you may as well be moving a toilet plunger attached to the floor.

No I simply emphasised a FACT (thanks for recognising that) any convenience is coincidental.

How can it be?

it describes clearly:

1. there is still elevator authority enough to take the aircraft beyond stall of the slatted portion of the wing.
2. the aircraft stalled despite having slats.......amazing.
3. a wing dropped......clearly the beginnings of the incipient stages of a spin.
4. slats failed completely to prevent entering into that.
5. the quote makes no suggestion of a continued pitch input to delay recovery, this leaves it open to speculation as to what would happen should the pilot not ease off on the stick.
6. given that the evidence has now proved there is enough elevator authority to take even the slated portion of the wing beyond critical angle of attack and maintain that condition...(or have you forgotten theres an engine giving you thrust which affects the elevator?) what is the phenomenon that prevent the 109's magic wings from behaving like any other plain wing once all of its slats usefullness has run out? are you really saying that a slatted wing can pitch infinitely without penalty? so a 109 can actually do a Pugachev's cobra?

That is the key condition in the NACA report, btw.

Uncover the gun ports and the NACA found the same stall characteristics as noted in all the early mark Spitfires Operating Notes.

So, does the game model a Spitfire without weapons available or one that is fighting??

:grin:

:rolleyes:

Taildraggernut, why don't you squash all your theories with some experience? Get in an airplane and try to raise the nose at the stall to see what happens. Make sure you have plenty of altitude and an instructor with you. Don't want to see you get hurt.

Read the RAE report too. Look for the words "Stick back to the stops".

In otherwords, the stick was all the way back at the stall point in the Bf-109 by design.

That is normal for many properly designed aircraft.

Now think very very carefully what you have said here.......take your time, you may eventually understand that if you really had to deflect elevator fully to the stop in a high speed stall then you are probably flying an aircraft with elevator controls the size of trim tabs.....is it sinking in yet?

I really wouldn't be saying any of this stuff unless I had the experience, anyway this constant questioning of actual real life experiences is completely redundant, I don't know who you are or what you are boy/girl/slimy green tentacled monster or actually a real flying instructor.
all I can say for sure is the stuff you are pumping out on here is absolute garbage, i just can't figure out why someone would do that.

Taildraggernut,

It will be more useful for you to seperate pre-stall behaviors from stall behaviors. You keep confusing and blending the two. They are very different conditions of flight.

In the Bf-109, the main wing is stalled when the wing drops. The slats remain effective preventing spin entry and the aircraft experiences loss of elevator control to raise the nose further. That loss of elevator control prevents the pilot from increasing angle of attack beyond the stall point of the slatted portion of the airfoil.

The RAE is not discussing pre-stall behavior, they are talking about the accelerated STALL of the aircraft:

No, the wing drops when one of the outboard sections of the wing stalls, this can only happen if the slot had run out of puff and stalled itself.

now about that loss of elevator control, what causes it?

When you take off in this game, your Spitfire's gun ports are indeed covered.

Now when you know the wing and slats of V2 were the same, would you care to comment on the spin test report I quoted a couple of pages back?

I agree the stall characteristics of the 109 in game are incorrect but I believe you're equally wrong with you claims about 'non-spinnable design' and 'devices'.

You can even get a C152 to spin, but you have to work for it, same with the 109, it seems, you can get it to spin, if you work at it, but it is very difficult to get the spin without forcing the plane to spin.
That is how i read it.

Not quite, what it really means is the 109's behaviour in the stall is relatively forgiving and gives ample opportunity to recover before things get too far out of shape, the fact remains that slats simply delay onset of a stall and not prevent it completely, if you keep pulling back on the stick after the slats have become ineffective then you increase your chances of entering a spin, the severity of which is subjet to debate but likely to be quite easy to deal with, the key point is once you have been forced into recovery technique during a combat turn you have effectively left the engagement and you are vulnerable.

If you reduce it to that, the key point is that the 109 is controlable all the time, even in a high speed stall, and its adversaries aren't, which is a great achievement by itself and should be represented in game.

I'm not sure why you get that impression of it's adversaries, the NACA report on the MkV (which was the worst Spit in terms of stability) was actually quite good, the 109 is not in control all the time, if an aircraft is stalled it has technically lost control and the reports show the 109 could stall with an uncomanded wing drop, an uncomanded motion is by definition not in control, what should be represented in the game is something close to reality and that reality is that both 109's and Spits had very desireable stall handling qualities with both aircraft being pretty benign and in the Spitfires case having particularily good stall warning, I might add that if you were to believe Crumpp then the 109 also loses elevator control.

I am struggling to find an aspect in that report saying the Spitfire should spin wildly out of control

I guess you was typing to fast and that charcters outrun your mind.

Hve a look to an F4E wing (or an A4). ;)

As usual the answer is only refering with evidence that is supporting the posters opinion and hair-splitting.
1. Did the 109 recover from a high speedstall with only minimal control input? The RAE report says so. Hardly a uncontrolled flight situation then, i'd say.
2. Did the early Spitfire depart from controlled flight in a high speed stall with a flip over and a following spin? Afaik all sides so far have admitted that.

There is no dispute that the controlled stall in the Spitfire was not hard to manage, but then, that was not asked for.

Please, can I respectfully ask that you don't descend into this mad poo flinging fest that arises every time someone simply has a different oppinion and shows evidence to back up why they have that oppinion.

I merely reminded of the good qualities of the Spitfire handling after you had basically claimed otherwise..

Both the 109 and Spitfire had this quality.

I don't admit to this, as far as I'm concrned the MkV was the worst Spitfire for longitudinal stability, earlier Spits by default will have had better qualities.

I am still waiting on Crump's to tell us what he tells his so called students..

As in what does he tell them the purpose of leading edge slats are..

1) The purpose of leading edge slats is to reduce the chance of a stall
2) The purpose of leading edge slats is to reduce the chance of a spin

I think most agree the purpose of leading edge slats is to reduce the chance of a stall

Where as it appears that Crump is saying the purpose of leading edge slats is to reduce the chance of a spin

I think it would be interesting, and telling, to have Crump explain this line of reasoning..

Especially in light of the fact that there are many accounts of how leading edge slats CAUSED spins!!

Where, for what ever reason, the leading edge slats did not deploy evenly and thus induces (CAUSE) the plane to spin..

Not to mention the accounts of the leading edge slats POPPING out suddenly such that they 'changed' the aerodynamics such that the pilot had to quickly adjust his controls.. In essence startling the pilot such that he may have over compensated and CAUSE the plane to stall or even spin

In summary

It appears this is another cause of Crump cherry picking Luftwaffe attribute..

Where here only talks about the PROS of a certain attribute and totally ignores the CONS of a certain attribute

AoA with such a name you shld know that it is both. And then with logics in mind it's the 2nd arguments tht is the most valid

In the absurd an anti spin decice IS a device reducing the chance of a spin to occur

You know, flight manuals are full of such simplification. A pilot is not a always a Phd holder in physics. It can eitherbe a carpenter, a greedy politicians or a nightclub hotess!

So using your logic..

The purpose of the breaks in my car are NOT to stop my car..

The purpose of the breaks in my car are to prevent me from getting speeding tickets..

Hmmm..

Sorry but no sale!

Ill stick with the intended purpose of the breaks in my car and not the multitude of what if's purposes the breaks in my car can be associated with to try and make a point..

Nice try though! You and Crump get a gold star for effort!

Sorry AoA, but with such arguments you are soo far out, that you will find it hard to see the objective, imo, of course.

And Taildraggernut, you are promoting the theory that the Spitfire didn't flip over and started a spin if pulled too hard in a high speed turn?? Really???
Afaik this was used by experienced pilots as a last ditch maneuvre to escape from a 109 on their tail.

Are you suggesting that Spitfire pilots had to exploit a lateral instability as opposed to deliberately entering the spin by actually making pro-spin inputs? really?

putting an aircraft into a spin is a technique available to any pilot in any aircraft as a deliberate manouver.

Don't be sorry

In that I fully expected you and yours standard off topic reply in an attempt to take the focus off what I said..

Not to mention how you and yours totally ignored the points I brought up about the historic accounts of the Bf109 slats causing more spin issues than they solved..

Now there you have to bring some proof that the assymetric action of the flaps, which was intended, was causing spins.

And the points you've brought are as usual black and white with no room for intermediate.

Isn't this thread about SLATS?

This is a fundamental misunderstanding which comes up again and again in the course of discussions re. the 109's 'controllability'.

An aircraft in a stall is out of control by the very definition of the word 'stall'.

It is no longer in flight. It has ceased to be anything but a falling object. Maybe the 109 will fall in a predictable and logical fashion, but it is still falling.

A 109 in a stall is out of control. No if's, and's or but's.

Can a 109 be recovered fairly quickly?

Yes, but a recovery requires the standard stall recovery procedure, ie. centered or slightly forward controls, allowing the aircraft to gain speed and lift, and gentle application of controls only after the normal conditions for flight have been re-acquired.

A stall in a 109 like any other aircraft is going to result in loss of control and height. Perhaps the stall can be recovered fairly quickly, but recovery is still a requirement. While the aircraft is out of control, it cannot be flown in any normal sense. Any attempt to 'fly' a stalled aircraft is going to increase the severity of the stall, and prolong the time the aircraft will remain in a stall. Want to put a 109 in a spin? Continue to try to 'fly it' after it has entered a stall.

To quote again the RAE report on LOW speed turn stalls:

Note the requirement for the stick to be eased forward (brought forward GENTLY) to allow the aircraft to regain speed and lift. Standard stall recovery. Any attempt to use the controls to do other than stall recovery would result in a prolonged stall.

As has been mentioned several times on this board, the Spitfire's stall was very easy to read and anticipate. Even rookie pilots were capable of learning this, and even in a high speed situation:

I can quote quite a number of other examples.

The Spitfire's 'judder' or shudder or buffet happened before the stall, and it was quite possible to ride this edge for maximum turn rate.

Only those who were ham-handed or completely inexperienced would not know how to use this indicator.

Yes, if pushed beyond this, the Spitfire would flick over on its back and spin, but given the fact its stall speed was lower than the 109's, and it turn circumference was smaller, there was no need to for a pilot to take it that far.

Notice also in this description the 109 'flick' referred to. This is mentioned in many combat accounts, and tells us clearly that in an accelerated stall condition, there was the potential for a wing drop on the 109 if the stall indications are ignored and controls continue to be over-applied.

From the Spitfire Mk II Operating Handbook. The same warning appears in all early mark Spitfires:

http://img835.imageshack.us/img835/3...tinghandbo.jpg

Roll instability near the stall as noted the NACA agrees with the Operating Note warnings:

http://img405.imageshack.us/img405/3...allwarning.jpg

That help?

Thanks for providing that documentation to bolster my comments.

"The Spitfire possessed GOOD stall warning in the form of buffeting....
...the stick could be moved well back before lateral instability occurred"

"...rolling instability was noted AFTER an unmistakeable warning in the form of buffeting occurred."

Of course the Spitfire's capability of entering a spin off a high speed stall has nothing to do with the 109's slats.

However, I guess this thread has established two things which are incorrectly modelled in the game:

1) The 109's tendency to enter spins easily and the tendency for recovery from spins to be difficult.

2) The lack of modelling of the Spitfire's pre-stall buffeting.

The game Spitfire will clearly enter a spin out of a high speed stall through the path of a flick onto its back.

I agree.

The pre-stall buffeting of the Spitfire and its effects should be modeled.

Yes, except maximum turn rate occurs in smooth airflow not buffeting. The buffet is often used to find this point and then backing off to smooth air.

If you turn in the buffet, your rate will decrease and your radius increase.

The more high energy the buffet, the greater the effect.

Of course Crumpp fails to point out the pre-conditions noted in the NASA report, steeply banked turns with open gun ports; nor does the report state that the instability was actually dangerous, and it does not explain how all of this affected the Spitfire in combat or as a combat aircraft. Nor does Crumpp explain that the Spitfire's stall behaviour was more often praised than slated by NACA, in this and in another report on the Spitfire's stalling characteristics.

And, of course, this is not about the Spitfire anyway - Crumpp has obsessively chased this subject already in other threads - but as to modelling this pre-stall buffet, perhaps, crumpp could develop a program which will allow all gamers to feel this buffeting, either through their joysticks, or the seat of their pants?

For once a posting that I totally agree with.

As to how to replicate the buffet in the game, I suggested once that in the ideal world everyone would have a feedback controller which would vibrate. However we have to recognise that this will not be the case so I suggested a visual cue where the cockpit view would vibrate.

Now back to the question yet to be replied to

Crumpp
Do you tell your students that leading edge slats :-
a) are a device that delays the stall or
b) Is an anti spin device.

Do you agree that the correct solution is (a)?

Yeah, so only 'AFTER' the Spitfire has actually fired it's guns does it begin to suffer any form of lateral instability, just got to make sure the first burst counts then.
Like NZtyphoon says, Crumpp completely ignores the 95% of positive report on the Spitfire but emphasises the negative 5%, NACA summaried their report saying the Spits stalling characteristics were it's redeeming feature.