Discuss.

[Motherland]

I have no clue what it means, but it seems to suggest that the 109 should have a good angle of attack due to its wing slats. I honestly cant remember if it does in game (my hands are to ingrained with how far to push it to notice now) but my memory seems to suggest that it does not.

[SgtPappy]

Those slats seem to allow it to turn MUCH tighter than another plane without slats would, given the same wing-loading and similar power-load/drag as the 109.

[Stoney74]

Originally posted by Motherland I have no clue what it means, but it seems to suggest that the 109 should have a good angle of attack due to its wing slats.[/B]

A better way to describe it would be to say "the 109 should have a better angle of attack.  Slats are just another type of high lift device, like flaps, that are used to create more lift for a wing.  Someone else can explain the basis of their use on 109's better than I.

[Motherland]

Originally posted by Stoney74
"the 109 should have a better angle of attack.  

Thats what I meant. Now I cant edit it though...

[Karnak]

The effect of the slats are modeled in AH.

[JimBeam]

Originally posted by SgtPappy
Those slats seem to allow it to turn MUCH tighter than another plane without slats would, given the same wing-loading and similar power-load/drag as the 109.

that chart only shows the increase of the critical Angle of Attack of a wing with slats compaired to a wing without slats.

[gripen]

Well, the Bf 109 slats cover only the tip part of the wing, the rest of the wing stalls at same AoA regardless if the slats are in or out. In other words the slats are there to prevent tip stall.

[dtango]

As Karnak said- as far as I know AH models 109 slats in both categories that they should be modelled: (a) aircraft high-lift device animation, (b) aerodynamically in the flight model.

(A) Aircraft high lift device animation:
Just like other control surfaces (flaps, ailerons, etc.), slats are moving parts and should be represented in animation when they are used.  The interesting thing about slats are that they automatically activate.  As lift increases with angle of attack the leading-edge suction as the result of the changing pressure distribution of the wing becomes large enough to suck the slat open.  When the leading-edge suction reduces the slats automatically are forced closed.  

I haven't flown a 109 recently in AH but the last time I flew one I recall the slats automatically deploying whenever higher angles of attack were reached.  Just listen for them to automatically pop-open or shut in AH depending on the aoa of the aircraft.  They are definitely there on the Me-262.

(B) Slat aerodynamics in the AH FM
As stoney said slats are another form of an high lift device such as the variety of flaps.  Like flaps, slats can improve turn performance by increasing the lift limit and decreasing the flyable airspeed of the aircraft but do so at a lower parasite drag penalty compared to flaps.

The effect of slats is represented in increasing the maximum lift coefficient, Clmax of an airplane (albeit gripen makes an interesting point about the location of the 109 slats and their effect on aircraft Clmax).  Regardless, as such any effect of slats are embedded in the Clmax figure of the 109 which is readily obtained with actual flight tests reports of the 109 in relationship to stall speeds.  Knowing HTC they probably have some pretty credible 109 flight test data that they base the FM from.

Slat Physics
A small point:  the picture depicts the misconception that slats "energize" the boundary layer by introducing higher velocity airflow onto the main wing element.  Actually this doesn't happen at all.  Instead the slats actually reduce the velocity around the leading edge of the main wing element which reduces the leading edge pressure peak allowing the boundary layer to stay attached longer & delaying "stall".

Tango, XO
412th FS Braunco Mustangs

[Motherland]

Found some other interesting things, from the same webpage-



In reference to the spitfire's ellptical wings-
The elliptical planform has very small theoretical advantage, but only theoretical, and only valid if the planform is truly elliptical. Spitfire's planform is only approximating elliptical, and what is left has been sold out by the aerodynamic twist it's wing has. It has effect on just one of several factors of wing efficiency, causing a whopping 0.05 improvement in comparison to a trapezoidal planform used in for example Bf 109, that is, IF Spit's wing were truely elliptical...
You also have to take into account the fact that the profile thicknes ratio of Spit's wing is VERY thin, both in maximum and in average. This in turn leads to the small coefficient of lift. This pretty much takes away the advantage of the large wing area.
BTW, ever wondered where did all the elliptical wings go?
If they are so magically efficient, why nobody uses them anymore?
Answer is simple, later aerodynamic research has proven that most of the benefits of elliptical wing were a fallacy created by insufficient or faulty research methods. They simply were not worth the trouble.
Even the developements of Spitfire, Spiteful and Seafang gave up on the elliptic planform and went to normal trapezoid form. Wonder why?
Only thing special in it is the elliptic planform, that dropped of favour just after it, when it was found out that the theoretical benefits of elliptic planform were actually only theoretical, and practical applications did not yield benefits that would justify the almost astronomical manufacturing difficulties and costs.
In Spitfire's case the benefits of elliptic planform (even lift distribution along the span) are nullified by the 2 degree twist (washout) that was needed for at least partially taming the nasty and violent stall behaviour of such wing. In short, the wing twist negated the effect of the elliptical wing. Although the wing was physically elliptical, its lift was not.
Besides, wing aspect ratio has larger effect on the lift/drag characteristics than the Oswald efficiency factor (where the theoretical difference between Spit's and Bf 109's wing is only of magnitude of 0.05), and Bf 109's wing has higher aspect ratio than Spit's...
Spit's wing uses the exactly same NACA 2300 root profile as Bf 109's wing, but with only 13 % thickness ratio, while Bf 109 has 14.2 % thickness ratio. Lower thickness ratio translates to lower Cl max. Bf 109 uses the same NACA 2300 with thickness ratio of 11%, but Spit's wing profile gradually changes along the span to NACA 2200 (more symmetric profile with smaller Cl max) with thickness ratio of only 9 %.
All the above leaves the lower wingloading as the only even theoretical advantage for Spit's wing, but even that is somewhat negated by wingprofile that has less Cl max and Cl in general.
- Pentti Kurkinen, enthusiast


Drop tanks:
The droptank system in every Messerschmitt worked the same way. Fuel to the engine was always drawn from the main tank. The droptank replenished the main tank. This was done with an automatic float controlled device that opened the flow from droptank if the fuel level in main tank dropped. There was no pump driving the fuel from the droptank, it was kept pressurized by bleeding compressed air from the engine supercharger into the droptank.
The plumbing was routed from the droptank to the right upper forward edge of the cabin, and from there along the cabin edge to rear, into the fuel tank. There was a piece of perspex tube at the right side of pilot, from where he could see the fuel flowing. When the tube became filled with air (easy to see from the colour) it was time to release the droptank.
A nice system. If you had to jettison the droptank, you always knew that your main tank was full. And it also did not heed any preliminary actions like turning a feed selection valve or somesuch, just tug the release cord...

"109's controls locked up in high speed."
- Another very mythical subject. Before answering one must be asked: "What model are you talking about?"
- There was large differences between various types in the high speed controls. Each newer version handled better in high speeds, the best being the 109 K series which had flettner tabs for enhanced aileron control - at least in theory, as it is debated whether many Me 109 K-4s actually had those flettners enabled. 109 G series were much better on this regard compared to 109 E, which yet again wasn't such a dog as many claim. 109 test pilots, Russians included, have said that the 109 had pretty good roll at higher speeds - again not as good as the 190s, P-51 or P-47 - but it maintained a good lateral control ability. Recovering from extremerely fast 750-900 km/h vertical dives was the problem - not level flight or even normal combat flying.
- Spitfire and a 109 had equal roll rates at up to 400 mph speeds. Not even the favourite warhorse of the Americans, P-51, exactly shined with its roll rate at high speeds. P-51 pilots have actually said that flying P-51 at high speeds was like driving a truck.
- An often quoted British report made of a Me 109 E talks about the "short stick travel", "due to the cramped cockpit a pilot could only apply about 40 pounds side force on the stick" and "at 400 mph with 40 pounds side force and only one fifth aileron displaced, it required 4 seconds to get into a 45 degree roll or bank. That immediately classifies the airplane as being unmaneuverable and unacceptable as a fighter."
- The report claims that The 109-E needed 37lb stick force for a 1/5 aileron deflection at 400mph. Coincidentally, the Spitfire 1 required 57 lb stick force from the pilot for similar deflection at similar speed. This is a 54% higher stickforce for the Spitfire pilot.
- The British test is taken as gospel by many, while it is just one test, made by the enemy, using a worn out and battle damaged airframe. German flight tests report pilots using aileron forces of over 45 lbs and 109's stick was designed for elevator stick forces of up to or over 85kg, over 180 lbs. Finnish Bf 109 G-2 test revealed that at 450 km/h the stick could be still fully taken to the limit with ~10 kg force (20 pounds). Aileron roll without rudder could be performed to both direction from 400-450 km/h in 4-5 s. This is better than the Spitfire with fabric ailerons, about the same as Spitfire with metal ailerons and slightly below clipped wing Spitfire. So it was more matter of the pilot and the test procedures, than maneuverability of the Bf 109. Several details of that test are suspicious and German chief test pilot Heinrich Beauvais disagreed with it and with Eric Brown. Beauvais tried to get into contact after the war with Eric Brown to discuss the matters, but Brown refused to discuss with him. This being the case, it seems that Brown wasn't willing to listen a pilot who'd flown more on the 109 than he ever had, and was more interested on believing his negative findings of the 109 than being proven wrong by a real expert.

http://www.virtualpilots.fi/feature/articles/109myths/

[Stang]

The slats do give a slight increase in angle of attack in the game.  Very noticeable if you can maneuver it so one slat is out and the other is not.

[Stoney74]

Originally posted by Motherland
Found some other interesting things, from the same webpage-



In reference to the spitfire's ellptical wings-

So what's his point here?  The effort to produce the elliptical wing was done so because of faulty NACA research done before the war.  Everyone in the aerodynamic field thought the same thing as the Supermarine engineers did.  Heck, the idea for the wing design came from a German aircraft.  Look at all of the horizontal and vertical tail surfaces on a lot of the early WWII aircraft--they have elliptical planforms for the same reason.  Taper ratio is the key, as a .45 taper ratio from root to tip actually achieves almost ideal spanwise lift distribution.  I don't know what the Spit or 109 had for taper ratios.  The elliptical wing actually has a reference planform from which you can derive the taper and make a comparison.    Regardless, revisionist aerodynamics doesn't help his argument.  Only a wind tunnel and some fairly well controlled test flying can properly demonstrate some of his arguments.  Don't know if wind tunnel data exists, and the existing test flight data is surely suspect, at least in comparison, or at least, hotly debated as to its precision.

But, he starts getting carried away in the second paragraph.  Airfoil thicknesses can't be judged better or worse out of the context of the rest of the wing.  A very light aircraft can be a highly maneuverable plane, even with a low Clmax merely because of the wing loading.  Interestingly enough, a majority of WWII fighter aircraft used the same 23000 series NACA airfoil, Axis and Allied.  They even used practically the same thickness distributions.  So, there must be more to the difference between aircraft performance aside from airfoil Clmax.  He alludes to the wingloading as being the only remaining factor between the turn performance of the aircraft.  Well, if that's the case, it must have been a huge factor, as the Spit out turned the 109--that's not debatable by anyone, regardless of theoretical aerodynamics or actual test data.

If he's merely trying to get some credibility for the 109 as a successful WWII fighter--I don't think anyone with a knowledge of WWII aviation would state otherwise.  There exists much myth, legend, and folklore surrounding WWII aircraft.  Emotions, mis-read or faulty test data, nationalistic tendencies--all of these have played a part in skewing our perception of these aircraft some 60 years after the fact.  If you consider quality in the same light that most manufacturers do today, it is a matter of "suitability to purpose".  When examined in that light, you could judge the value of each aircraft with respect to its intended purpose, and how well the design performed with respect to that purpose.  Its success or failure on the battlefield is a entirely different matter, as there are many other factors involved.

I'm a P-47 fan boi, but I don't think it was a panacea aircraft.  It did what it was designed to do very well.  It also did some things it was not designed for very well.  The same could be said for the 109 and the Spit.  Not having a plane designed to excell at 30K feet is a lack of foresight, not poor design.

[gripen]

Well, the problem with this kind of sources is that these are just as or more selective than the sources they try to downplay. In other words, the outcome is creation of new myths instead busting the old myths.

[SgtPappy]

Don't think it's been said...
The main reason the elliptical wing was stuck on a Spitfire was not really its theoretical aerodynamic efficiency (may have been a factor in choosing, but it was not the main factor). The main factor was the need for a very thin wing that could cram what was needed inside. I.e. MG's, gear, rad/oil coolers etc.

[Motherland]

Originally posted by Stoney74

If he's merely trying to get some credibility for the 109 as a successful WWII fighter--I don't think anyone with a knowledge of WWII aviation would state otherwise.  

I dont think that this was the purpose of what he wrote- most of the stuff on the webpage is from many different sources- when this was written its possible that he had nothing about the 109 in mind- notice that the 109 was never mentioned in the excerpt- and he was just trying to debunk the 'uber elliptical wing' myth. And that it was put into the webpage for the obvious reason that the Spitfire was a big competitor to the 109.

[Karnak]

The Spitfire's wing made it harder to build and gave it a distinctive image.  The eliptical shape was not the reason for its success in combat, but it is likely that it played a substantial part in the Spitfire's media success.