Are slats shy ?
 

Each time I try to slat turn, they are just popping out before retracting banking over my plane no matter how hard I try to keep the ball centered.

On the weird list, If I do use a bit of flap (somthing btw 10 to 15 deg down) the Slats won't pop out at all.

I hve always been flying near the stall as an anti Spit device (IL2). What I am gonna do now (invoking the CoD's deities ) ? !! :confused:

Pls note that many Experteen used to mention the use of a bit of flap as a reg practice in slow turn fight.

In real use, the slats on the Me109 are deployed automatically once the speed is reduced beyond a certain level and that activation speed is higher than the aircraft stall speed. So I would expect them to deploy.

It sounds as if they are doing what they were designed to do

The activation of the slats has nothing to do with keeping the ball centered.

The ball is all abt not falling in a spin (or a bank over). What I want to tell is that as soon as the slat are deployed the plane is entering in a spin. My guess is that there is a bug here ;)

I'm unsure if the graphics match the FM (i.e. seeing or not the slats deployed currently makes any difference).
Anyway, I noticed yesterday that while powering up the 109, the slats started to pop out and in, out and in (no pun intended).
Since they move relative to the air speed, the slats should be out when the plane is in a stopped state on the ground which seems not to be the case.

To be pedantic slats are not speed dependant and work solely as a function of AOA :) though in 1g flight AOA and IAS are intrinsicly linked.
Not having the ball centred could easily result in different AOA on each wing and hence result in asymmetric slat deployment ... as can aileron input.

The Slat animation in CLOD at the moment is imo out of whack with what they should be doing. They should be coming out and staying out a lot earlier than they are at present. There is some discussion with the Devs on this going on using RAE test reports to come up with better more realistic operation. Not exactly sure when will actually see this.

The RAE data has 1G IAS (since they wernt recording AOA) slat deployment values for both the 109 and 110. These values can be used to extrapolate values for slat deployment at other G values. The essence being that AOA for slat deployment will always be the same, whilst IAS v G will change in a similar way to accelerated stall speeds v 1g stall speeds ie. Vstall X SQR G

Pls no RAE. They were lagging in viscous fluids (all abt RAE test pre-1945 is inviscid for what I hve seen or read) .

NACA shld be Ok - Karman being there on the late 30's

(source) :

Yes but NACA didnt have 109E's and 110's to test and record data on :) ... so its the best data available at present.

Whooot Not even you can find it ???? Damn we are doooomed :rolleyes:

I did pay attention to that. May I suggest you to hit the break before a full stop while watching closely at the slats ?

(this Sim is really great)

All those indiscretions in your soon to be expunged life :)

How can she be shy if she is a slu..

Oh.. wait one..

slats!

My bad.. thought you were talking about something else! ;)

109 E plane description says they should extend at 180 km/h.

Here are the values the RAE determined in Flight test Source AVIA 6/2394 BF109E Evaluation

http://img824.imageshack.us/img824/7522/raeslats.jpg

These are 1G values. So slat deployment under G will be Whatever number you use (ASI or trailing) from these x SQR of the G

There is plenty of Mtt data on it.

So how about posting some here for us to peruse. The more data we have the better. Ideally Slat development AOA's .

This is Bf-109E-3 V24 WNr 1929 from April 1940. The report is titled, "Drag and Measurements" and this polar is the aircraft in "normal" condition.

"Normal" by RLM definition means it was a little worse than the finish of an aircraft just off the production line and is intended to representative of an operational aircraft in mid-life. Sort of like the USAAF's "combat weight" (~60% fuel/oil) is intended to depict an operational aircraft encountering the enemy during the target portion of the mission profile.

The polar gives excellent agreement with the RAE measurements. It takes the Clmax out a few decimal places from the RAE report (~1.45), refines the opening CL(~.84), and gives you the 2D AoA(~17.5 degrees). The slats begin to open at about 8 degrees and are fully deployed by ~11.5 degrees. The wing is stalled at ~17.5 degrees with the body angle of course being the induced AoA + Angle of incidence.

http://img33.imageshack.us/img33/8166/v24windk4.jpg

It should help considerably.

A pretty good match with the simple statement in the 109E description, all things considered.

Regardings Crumpps chart, "Spaltklappen" and "Spreizklappen" are two different types of flaps, not leading edge slats. The slats don't open gradually. But from that polar and the RAF test, it should be easy to derive the AoA of ~ 8° at which they bang open.

Who cares and totally irrelevant to anything I posted. I know that and anyone who reads German knows it as well.

Neither of those polars is even in the discussion nor included in the values presented.

Baloney.

The slats open as required and the amount can be precisely controlled by the pilot. From open to close in the Bf-109 is ~2.5 degrees of angle of attack. A pilot can move through than little amount of angle so fast it would seem that they either open or closed. The reality is a pilot can control them and they will only open the amount required. If you knew how to read a polar, you would know that as the shape of the curve would depict it if the slats could only be fully open or fully closed. Simply put, there would be a shift in the polar and not a smooth transition.

Just how many hours do you have flying an aircraft equipped with slats? I can tell you, you have NONE as you don't know how they work at all. You have never been up in an airplane equipped with them either. Stop presenting erroneous information as fact.

I have about 400 hours flying a plane equipped with slats that work just like the Bf-109's.

It is called a "stick" and it is there for the pilot to command the airplane. This is me piloting my airplane a few years ago.

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

Is the radiator and intake flaps, btw....

Polar represents landing flaps at 60 degrees and the influence of the radiator and intake flap settings.

Are you sure? I think Spreizklappen are slotted trailing edge flaps whereas spaltklappen are split flaps. I understood these polars to be from tests of an E-3 for evaluating different alternatives to be included on the F-series as components (in this case different flap designs).

Image for those not familiar with different types of flaps

Not everyone around here speaks German, and given that the chart is labelled with Spalt- und Spreizklappe, and the legend contains it as well, it is useful information for everyone to understand the chart.

You presented a value from flaps extended polars, as you say the stall happens at ~17.5°, which is only the case with flaps extended. Good to know it wasn't intentional.

Slats open as chosen by the designer. It is absolutely possible to give them progressive characteristics so that they indeed bang open. This is reported by many pilots in case of the 109, and while I haven't flown one, I trust their word over yours.

I also have no clue how much simplified the polar is, it can contain everything or nothing. The information that can definitely be taken out is the one you and I agree on, the AoA the slats open at.

You're welcome to educate everyone on how you extract the other information.

No, in addition to what CaptainDoggles wrote, the cooler flap is set at 60°.

I think the "banging open" behaviour is from novice pilots yanking the stick and rapidly traversing through the range of angles of attack at which the slats actuate. Or perhaps debris in the tracks causing it to stick for an instant.

I doubt very much that the slats were an "either fully open or fully closed, nothing in between" type of system. They're like a drawer in your kitchen. If you pull it out rapidly it'll bang once it hits the end of the track, but it's still possible to open it half-way.

IIRC they also went from a pivot-arm type of mechanism on the early models to a roller-track mechanism on later variants (I think starting with the Gustav). Possibly the early models were more prone to sudden/violent actuation than the roller track mechanisms on the later aircraft.

Good Lord. Experts run amok....

The designs for the radiator flaps of the F series were tested as well during this investigation. In fact the aircraft, for those test's the aircraft was fitted with an F series cowling (intake), wheel well covers, and the various radiator flap designs being considered.

A little digging will uncover the fact the radiator flap ended up being a split flap on the production aircraft.

None of that has anything to do with the baseline polar determined from WNr 1929 in standard Bf-109E-3 configuration.

Wannka Wannka Wannnka....:rolleyes:

JtD is correct on the cooling flaps being at 60 degrees. There would be a camber change over flaps up configuration if the landing flaps were down.

:-|

Figure it out yourself. You have no clue how to read a polar and I am not going to teach you.

A little basic knowledge and anyone can tell you are "out der FLAPPIN" as we used to say in the Army when somebody was completely wrong. In this case, it is quite ironic you are FLAPPIN over flaps!!

:)

The effect of trailing edge flaps is to increase the camber of the wing.

What is the effect of a camber increase on a lift polar??

It shifts the whole polar to the right! That means it LOWERS our Angle of Attack!! You cannot have the same Angle of Attack flaps up as you do flaps down....

Check out figure 5:

http://adg.stanford.edu/aa241/highli...liftintro.html

It is not physically possible with TE flaps to have the same general CLmax presented by the RAE in clean configuration with a polar with the TE flaps down at the same Angle of Attack.

Which incidentally also matches the 2D data from the NACA family of airfoils.

BTW you can see the data point Mtt plotted for the plain airfoil and for the slats on the polar. The Bf-109 did not have full length LE slats so it did not get a dramatic CLmax increase.

Sheesh, was just asking for clarification.

Cool, thanks for the info

I think you think I'm attacking/disagreeing with you.

:?

- Could the pilot control the leading edge slats?

;)

Some interetsting info about Bf 109 slats from my bookmarks:

http://www.virtualpilots.fi/feature/...09myths/#slats

http://109lair.hobbyvista.com/techre...lats/slats.htm

You are welcome.

Not at all. It was supposed to be light hearted and not serious. I guess I blew it on that count.

:o

Geez....

look at the video....

Do you see me hitting the "slat button" or pulling the "slat lever".....

NO!!

Just like the finnish ace you quote but misinterpret his reply....

They work by air pressure at a specific angle of attack! Watch the video again and Guess how the pilot can control that air pressure??

I actually filmed the amount of stick movement required in that aircraft between slats fully opened and closed. Admittedly I did a horrible job at it as the camera moves all over the place but the last 5 seconds is intended to show the amount of stick travel required.

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

Here is the first part of your pilots quote....

http://www.virtualpilots.fi/feature/...09myths/#slats

Look at that, same control I used in my aircraft! No slat button or lever though!!

You can easily control the amount of slat you deploy with some practice. That being said, my first solo flight I almost jumped out of my skin when they deployed on approach. If you are not used to it and you move the wing rapidly through the AoA required to open the slots, they can open with a bang. I thought something fell off the aircraft at first.

Inertia makes them open on the grd.

Oh I do, pal. ;) What I don't understand is your ego. ;) You ruin every potentially interesting conversation by your aggressive 'fu, I know it all' attitude. :-P:-P

Let's try again - you can control the AoA, you can control the speed, but you can't actualy control the bloody slats. They pop in or out as a result of the above and you can predict it if you're not diff - just as you can predict that the aerial on your car will bend when you reach say 120mph - but you don't bend your aerial, it bends because you drive fast. :o You can make a video of yourself driving a car on the motorway with your foot on the pedal and the aerial bending but that's its design and general physics. Look - aerial control. As you can predict its behaviour you can take advantage of it, shall it come to that. Please don't ask me why have I come with bizarre example like this :D

And yes I know what you ment, we're not retarded here dude.

Oh yeah and tell us how you control your altimeter as you move the nose of your aircraft up and down.

Need video of slats at an intermediate position.

As a dedicated piloting task controlling slat position with fine stick (AOA) control is a straight forward and good experiment. however in the hussle and Bustle of combat I suggest AOA changes would generally result in the slats being either in or out ... hence the pilots description of them "banging" in or out.

Crummp I too am confused by your "Wannka Wannka Wannnka" bit... can I assume you have spelt it correctly ? Is it a US term or are you referring to some basic Brit slang ?

Look at the Bf-109E polar I posted, it is only ~2.5 degrees of AoA between the slats beginning to open and fully deployed. That is not much to work with.

I did not say it was easy or did not take practice to control them. You are right in that it is not something a pilot is likely to master in his first few hours. They take some getting used too. The airplane will shift when they deploy. If you watch the video, you can see some of the changes in radius in that turn. The slats can make loud startling noises.

In a fighter equipped with them, that shifting would make aiming more difficult. Once you learn what they can do though, the low speed maneuvering is fantastic. I won an ultralight Short Landing contest with a 4000lb airplane because of those slats. I could hang that airplane on the propeller all day long. In fact, clean, it would not break in the stall. With full length LE slats, the plane would nose up, hang on the propeller, and gradually enter a 900 fpm descent. You were stalled when the airplane was nose up and descending. The stall angle was so steep, I used to put a pencil on the glare shield to impress FAA examiners and it would fall straight back to the luggage compartment over the top of all the seats without hitting them.

The real maneuvering fight would not begin for a Bf-109 pilot until those slats where out. That is exactly how I felt about my aircraft. Once those slats deployed, it was time get busy if I wanted to maneuver.

http://www.virtualpilots.fi/feature/...09myths/#slats

As I see it based on my experience and knowledge:

Slats Pro's

- Low speed handling / maneuvering improvement
- very benign stall
- immune to spinning (read the RAE trials)

http://kurfurst.org/Tactical_trials/...ls/Morgan.html

Slat Con's
- Opening moment reduces effectiveness as a gun platform.
- Asymmetric deployment is normal. A mechanical malfunction is not. If a slat becomes stuck due to mechanism failure, the pilot has a real control problem if the other deploys.
- noise form a hard opening is startling.

Much of what you are asking depends on the specific stability and control of the aircraft in question. I will try to convey the general effect of the slats outside of specific stability and control.

You can definitely feel when the slats deploy. It moves the trim point and the stick pushes back against your hand trying get to that point.

The slats energize the boundary layer. What does that mean? They create turbulent flow over the wing. Turbulent flow is high energy flow and that means it has energy to convert that flow to lift. That is not turbulence as in buffeting. Buffeting is caused by flow reversal which means the boundary layer separates from the wing stalling that portion.

A boundary layer has two types of flow, Laminar and turbulent. Watch a cigarette in an ashtray sometime as it burns. The straight smoke is laminar and where it becomes wavy is turbulent. Laminar is low drag and low energy. Turbulent flow has more energy and more drag. The higher energy means it can meet the lift force required at a lower dynamic pressure.

The effect is best described as the airplane responds like it is flying at a much higher speed. It does not feel mushy or like it is struggling in slow flight. You can maneuver more precisely than you could when the slats were not out. As you get closer to CLmax and the dynamic pressure drops in 1G level flight, that feeling will diminish.

Is that clear or confusing?

That makes a little bit of sense, as the chart explicitly states "Spreizklappen innen" - "slotted flaps inwards". Which probably means they only changed the part around the radiator.

I'd think they move to the left, i.e. proving more lift for the same AoA...but I don't see how the trailing edge flaps suddenly became the issue.

That's interesting and impossible to know from just looking at the chart - these dots carry no designation and could be anything, in particular as the same dots cannot be distinguished in the flaps extended polars. So thanks for telling.

Of course not....that would mean you spouted off without knowing the context or details, posting something to discredit whatever I said.
:rolleyes:

It does move to the left when TE flaps deploy. A camber change shifts the lift curve reducing the AoA CLmax for the airfoil occurs.

In this case though you claimed that the top polars were different designs of TE flaps deployed and their effect. They were different designs of radiator flaps as I stated in my first reply of too many to you.

Therefore, the curve in question on the bottom would be shifted to the right if that was the case. You started posting about the language used on the polar out of context and without the details.

JtD your focus is never on the topic at hand. It is only to discredit anything I say in any way that you can.

I have nothing further on this topic or any other topic for you. You can work whatever angle you dream up to claw at this conversation but I wish you good luck in your life.

For the readers, asymmetric deployment is normal. As the slat works as required, it does not effect the flight of the aircraft at all compared to symmetrical deployment.

It only becomes a problem when if the slats experience a mechanical malfunction and one slat cannot meet the force required.

Hi IvanK,

I hve been thinking at the solution you wrote over the night and I hve some doubt of the solution proposed: V_SlatOut = VstallxSQR(G)

At first I understand that this is similar to old IL2 and thus is a satisfactory solution for all. However my point here is that it cld be improved.

Slat deployment on the 109 was governed by the air pressure on the leading edge (LE) and the hinged mechanism weight and frictions forces.

a. Frictions forces are cte (K)
b. Weight effect is dependent on G (P=mg)
c. Dyn Pressue acting on the slat is a function of the speed of the plane (V) and the AoA (alpha) with Pdyn = 0.5roV²S*cos(alpha)

Hence we have V_SlatOut = f(G, Pdyn) + K

At 1G, the speed being known, as is the AoA we have the resulting value of the Weight and friction of the mechanism given that we make the calculation of the projected surface of the slat

We can now choose to consider the friction of the mechanism negligible given tht the slat were known to be retractable only by the application of one finger (and much attention were required to keep the slat close on the ground to protect the mechanism from ingesting dust, sand and small objects).

So basically we will hve V_SlatOut = f(G, Pdyn) tht result in the programmed law :

If V<= V_Stall*SQR(G) and If Pdyn>=mg (m being the resulting balancing mass calculated at the 1G condition) Then Slats Out.

The good thing is that by this way you hve an independent behaviour for both slat that can result in asymmetric deployment ;)

Pls note tht the Weight I am talking abt is not really a mass per G. It's the seen mass by the system combining all efforts in the mechanism that result in the deployment of the slat minus the friction. I am pulling away the frictions forces as they are not dependent of the G and are basically negligible if the system is functioning optimally.

EDIT:

Sry Crumpp I did delete my post as I needed to check my info. Here it is right as before.

I checked the deployment principles here http://109lair.hobbyvista.com/index1024.htm

just a small vid i just made to spice this interesting thread up..

http://www.youtube.com/watch?v=cewk7t_gN-w

Then why do you say the opposite, first?
The Messerschmitt engineers referred to them as trailing edge flaps, but since the radiator flap was part of the trailing edge flap, I don't even understand what point you're trying to make now?
The curve on the bottom would shift to the right if wing camber increased? It wouldn't. In case I misread you, can you please post a little bit more coherent (leaving out the "u suck I rule" stuff would help)?

You could still explain how you see that the slats deploy within the 2.5° between 8 and 11.5° AoA as you said. From where I am standing, it is not on the chart.

No problem and I wasn't trying to correct you. Sorry if it came across that way.

No problem at all. I hope it helps.

Thanks for posting that.

Can you make one and stall the aircraft in 1G level flight and then stall it left/right in a level turn please? Also deploy the slats in turn by pulling the stick back and retract them by releasing it like I did on my aircraft to see what level of control you have.

My practical experience with 109 slats (actually, Buchon, so late version and no, I haven't flown them - lol) is that on the ground they're very definitely either up or down. The mechanism doesn't seem to hint at any kind of balance anywhere in between, it's all up or all down. They do seem rather secure in the up position while on ground but I could imagine with a plane bumping around on the grass during takeoff they would likely pop down, but there would be contributing air loads going on as well, obviously.

It also struck me while I was fiddling with them that it might take a little less AoA to pop them back in that what popped them out. If so, that would reduce the chance of having them banging back and forth if one happened to be riding the magic AoA.


--- Let me know when I can groundloop a 109 (or anything else, for that matter - lol) in game. ---

That's the beauty of the design. They work automatically, allowing the pilot to maintain control at higher angles of attack without devoting mental effort to it.

Thx for sharing Zip.

I understand here that friction wld be negligible as supposed.

I agree. The point being that the slats work as required AND if they are correctly modeled, the pilot can precisely control their deployment.

It is a function check not a combat tactic. :)

It's hard to ctrl the amplitude of the slats opening.

Once the slats start to deploy, the gap btw the slat and the LE (leading edge) is the path of the accelerated flow that will impart the equilibrium tending to accelerate any tendency either of opening or closing.

I never had any trouble, although what you are saying makes sense. It is however balanced by the weight of the aircraft such that the slat only open as required.

:-)

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

TomcatViP,

To clarify..

If you compare the initial opening of the slats and controlling them from the open position, you are correct.

The initial opening is much harder in comparison. It is still controllable but the level of skill required is much higher.

Yes that's what I mean.

Never had to fly with slats until now so it is just my view of how it shld works.

Note = Modern slats on fighters are power ctrled so we can't make any comparison. Tht's why your vid is interesting to watch.

And there should be a bang nose isn it ?

Only if they open violently, i.e you go from low to very high AOA in a short amount of time. It's basically just like a drawer in your kitchen. If you yank it open it'll slam into the end of its track. If you open it smoothly it won't.

Agree. It'd probably be more like a tactile sensation through the controls.

In that case the noise of the shock will travel inside the wing just to be amplified by the vast empty space of the fuselage (resonance) where there is the pilot. I think that the Bang (if there was one ever) wld be audible above the eng noise (just like AP bullets impact etc...).

Reading modern account of private pilot flying the 109 E shld give the answer.

I don't think this word means what you think it means.

I checked on a dic but I still might be wrong.

It might be tht the word "reverberation" was more expected here :rolleyes:

I think you used the word absolutely correctly (with all due respect, Doggles) and it makes perfect sense. Would be great to have that accoustic side modelled as well.

Anytime the 109 slats are mentioned from pilot-reports they deploy with a loud "Bang".

From the way that they are working i'd imagine that there is a definite hysteresys between deploying and returning, so controling that might be a wee bit difficult and not the optimal aoa.

No they will only bang out if you jerk the stick and rapidly transgress the deployment angle of attack.

There is no reason for the pilot to control it. The slats work automatically. What I showed is that properly modeled, a Bf-109 should be able to control them.

Controlling them is not something though that is useful in terms of flight. It is just a function check for your games modeling, understand?

The current il2CoD bf-109 flight model files include the following entry:

LeadingEdgeSlats Mechanical Automatic Move 0.1 sec ResponseRange 15.0 to 15.01 deg

(personal note: when the BF109E stands on the ground, the AoA is 16 deg.)

Following the entry, the slats should function manually and/or automatically.

Looking at the current 15.0 to 15.01 deg AoA, the flaps should not work seriously.

Happy landings

Varrattu

For me it only means that they were not satisfied with the result and blocked it without cancelling the code (for a latter revue ?)

Nice found Varra - a bit scary but nice

Slat operation (or lack of early enough operation) has been snagged with the devs a while a go. That find in the FM probably explains why we are seeing what we are.

i dunno about slats,but sluts sure aren't................

I made an offline test with an E4 today (long time I did not hve tried) and the slats seems to function on that model. I was able to turn 360 with the slats opened.

The E4 is also much easier to handle in high G moves. It might be that the last patch has introduced some significant changes.

Varra in what plane's FM did you found those lines of Codes ?

"Hand off the throttle, select FLUG on the undercarriage selector, The mechanical indicators motor up very quickly, and you feel and hear a "clonk, clonk" as the gear comes home. A quick look at the wings, and you can see that the slats - fully out - are starting to creep in as the airspeed increases and the angle of attack is reduced"

'Flying the Bf109' - by Mark Hanna, "Fighters, the Best of Flight Journal:, Summer 2001.

From all I've read, I believe that the slats on the 109E should be free to move through intermediate positions, just like its currently modelled in IL-2.

The ONLY references I've ever heard to slats "banging in and out" involve either hard maneuvering of the aircraft (thus rapidly transitioning through AoA) or getting in the slipstream of a large bomber (also large AoA transitions).

Gentle movements of the stick in a turn, or holding pitch constant whilst increasing airspeed (thus slowly decreasing AoA) should have the slats moving/creeping in and out.

Bf-109E-3.fmd


Bf-109E-4.fmd

Thx Varra. It seems that as there is no diff I might hve been the victim of my own convictions. :grin:

A Bf-109E-1.fmd does not exist ...