Me 109 leading edge slats

[zetland76]

Hi,
Can anyone give me any info on this. I believe they were deployed automatically. When and what controlled this. I heard they were a bit of a problem in dog-fights.
The more info the better!

Thanks in advance

Mike

 

[Kurfürst]

Simply air pressure / angle of attack of the aircraft.

 

[Trebor]

I noticed that when I downloaded a payware BF-109E (that a buddy of mine gave me for no charge) and whenever I'd pull back on the stick, those slats would expand, and I always wondered what they were for. but thanks for clearing that up!

 

[Kurfürst]

They are high lift devices. The amiunt of lift a wing would generate increases with the angle of attack. After a certain AoA however, the airflow becomes turbulent and ultimately separates, at which point the lift produced actually decreases and the aircraft will stall.

Leading edge slat, when they open at high AoA increase that critical AoA when all this happens (and this way, by definition the maximum lift), therefore they help stall characteristics at say, landing or allow the plane to be pulled harder in turn, ie during turns.

Its also very practical since they only operate when they are actually needed.

 

[billswagger]

Hi,
I heard they were a bit of a problem in dog-fights.

Its not so much that they were a problem in dog-fights, they were actually meant to help the plane in turning but some observations do mention minor aileron snatch and buffeting at lower speeds. They could also be a problem if one slat opened more than the other, but i'm not sure that is possible with out mechanical failure.

Bill

 

[beaupower32]

The 109 Lair- The Online Source for Messerschmitt 109 information


This was off the 109 Lair website. Hopefully this will help. The pictures are on the website, if you want to check them out. Go to Technical Reference, then structures, then wings, then slats.

Over the years, all manner of explanations have been offered about the slats on the Messerschmitt 109 family, some of them fairly accurate and some of them downright ludicrous. This article should help to clarify the operation of the slats, their mounting, and their operation.

First, let's discuss what they are NOT:

- They are not motor-operated.

- The port and starboard slats are not connected to each other.

- They are not fixed in one position.

- When extended from the wing surface, they are not "dropped"- they are extended.

This slat design was first proposed by Sir Frederick Handley Page around 1919 as a way to maintain airfoil efficiency at high angles of attack. As the airfoil pivots at a greater angle from the direction of airflow, the point at which the flow detaches from the upper wing surface moves further and further forward. Eventually, if this condition continues, the airflow "unsticks" completely from the upper surface, and the wing stalls. In order to delay this action, the slat on the 109 extends outwards under aerodynamic pressure, channeling airflow back up and over the wing upper surface, thereby maintaining airfoil effectiveness.

A common question asked regarding the 109 is "Should the slats be in or out when the aircraft is parked?" The answer is "yes". The slats are free-moving devices, and are commonly seen extended in many wartime and contemporary photos; however, if manually pushed back into the wing, the slats would remain there until the aircraft moved, at which time they would extend of their own volition. This action was confirmed by Günther Rall when questioned by Lair visitor Erik Whipple some time back; according to Gen. Rall, it was common practice at their field to push the slats in once the aircraft were secured so that no dust or debris would accumulate in the traveling tracks. Evidently at least one new pilot was lost due to faulty operation of the slats when taking off, which led to this practice. However, as with almost everything else 109-related, if the position of the slats is of serious concern to you when building a static model, consult your references to determine the best configuration.

So, now that we've very briefly covered what they are and what they do, let's take a detailed look at the slat systems of the Bf 109. The manual illustrations below are taken from an official factory manual for the Bf 109E; however, the Friedrich retained a similar design for slat operation as the diagram below will show. It should be noted that two major differences introduced on the F version were a reduction in slat span from 2292.5mm to 1800mm, and the elimination of the inboard to outboard connecting linkage . The basic swing-arm movement, function and operation of the slats remained the same, however.

The Bf109 "E" through "F" used the swing arm parallelogram mechanism to agitate the slats. From the "G" onwards the Me 109's used the roller-track mechanism to guide the slats in and out. It all follows a patent bought by Messerschmitt from DeHavilland just prior to the war. The slats are driven out by means of low air-pressure if the AOA gets higher ( slow flight ) and retract by means of air-pressure when accelerating...

The most interesting thing about this is that there are clearly several significant differences between the Friedrich and Gustav wings, despite their outwardly identical appearance. The radiator ducting and the slat mechanism are both different

 

[davebender]

Most modern fighter aircraft like the F-22 and Eurofighter Typhoon utilize leading edge slats. That tells me leading edge slats are a good feature on fighter aircraft. They were probably cutting edge technology when introduced on the mass production Me-109.

 

[schwarzpanzer]

Hi zetland,

You may be interested in this, which I posted a while back:

http://www.ww2aircraft.net/forum/other-mechanical-systems-tech/me109-slats-6636.html

 

[VALENGO]

There is an old training film about Me 262 (not Me 109, but take for sure is the same functionality of the slats) where you can see a man that raises a slat and leaves it fall again. This test was a routine check to be sure that the device was not jammed and could freely move.

 

[zetland76]

This web site is great!

Thanks for all the replies. I'll be reading them for some time I guess

Thanks

Mike

 

[vanir]

Hiya davebender, on modern fighters the items you're referring to are leading edge flaps rather than slats, more about stall speed at low AoA. They're actively controlled by the flight computer along with a small amount of rear flaps and change the shape of the airfoil, unlike slats which are a boundary layer control used for achieving high AoA.

The whip thin airfoil of supersonic a/c gives them very high stall speeds, up around 300kmIAS or more and that was a problem in the old 2nd generation days. Even if you could raise the AoA safely it's not going to bring such a figure down significantly enough to be very useful. Swing wing was one solution but even these generally have a leading edge flap system to get reasonable landing speeds out of a supersonic fighter. The modern approach is double deltas and body lift with the system, flight processors have changed the game a bit so a modern warplane is probably easier to fly through normal manoeuvres than anything from WW2.



zetland, I remember Gen.Rall mentioning he had troubles with the Emil in tight turns, with one slat snapping open through the turn and inducing a stall if you weren't ready for it. Someone else told me the rail system in Gustavs onwards fixed this, I think it was Kurfürst actually.

 

[Milosh]

Most modern fighter aircraft like the F-22 and Eurofighter Typhoon utilize leading edge slats. That tells me leading edge slats are a good feature on fighter aircraft. They were probably cutting edge technology when introduced on the mass production Me-109.

The Ol' Stringbag, the Fairey Swordfish, had leading edge slats on the upper wing.

 

[ppopsie]

Swordfish! Patent for the automatic slats still held by Handley Page. Was the Bf109 affected by this patent? or was it expired?

One more question; did the Swordfish have slat locking mechanisms like the one in the Tigermoth?

 

[billswagger]

I've had a question about the rate of roll for the various 109s, particularly since its been said that high speeds the Emil was too stable, difficult to roll, yaw or pitch.

I wondered what sort of improvements were made to help deal with those issues, particularly in the F and G series. Being they improved wings, i would think they also had improved aileron effectiveness, but the information on roll rates is cloudy.


Bill

 

[FLYBOYJ]

The F-86 had L/E as did the Lysander...

To claim patent rights I believe the system has to be built exactly like the patent holder. If there are different components and the basis of operation of slightly different, there's no basis for patent infringement.

 

[Shortround6]

The F-86 had L/E as did the Lysander...

To claim patent rights I believe the system has to be built exactly like the patent holder. If there are different components and the basis of operation of slightly different, there's no basis for patent infringement.

there was an German WW I pilot who was a co-holder of the patent with Handley-Page and they wound up being good friends. These slats were fitted to quite a number of aircraft during the 30's but experience showed that they were only useful at rather high angles of attack and a lot of later aircraft dropped them and the related letter box slots. As a for instance it is reported that only the first 50 Handley-Page Halifaxes were fitted with slats.

 

[Milosh]

The F-86 had L/E as did the Lysander...

To claim patent rights I believe the system has to be built exactly like the patent holder. If there are different components and the basis of operation of slightly different, there's no basis for patent infringement.

Were not the slats eliminated with the 6-3 wing?

 

[FLYBOYJ]

Were not the slats eliminated with the 6-3 wing?

Yes