Emil's flap

[Krusty]

I'm not entirely sure that's right... You'll notice the hinge point is outside the physical space the flap occupies.

Also I've seen some photos of the 109 wing undersides pretty close up. There isn't much of a gap between the flap and the wing. It's not as noticable as that drawing leads you to believe.

They're just drop flaps. They have an extension inside the wing that rolls out (you can see this in photos) but that's pretty much it. It's not an air flow slot. It's pretty much flush.

EDIT: After a couple of minutes with Google:

http://www.vintagefabrics.co.uk/images/bf109e_wheel_zips.jpg
You can see at the bottom edge of the picture the gap between wing and flap is noticable, but not so big that air would be flowing up through it and out the top of the flap.

http://www.preservedaxisaircraft.com/Luftwaffe/relics/images/Bf%20109E%20wing%20Tikkakoski.jpg
It does have a curve, but the portion of the flap that extends ahead of the hinge point would roll up and block off any air that would try to get up in front of the flap.


I could be wrong, but it doesn't look like it's slotted to me.

[gripen]

I could not find a good picture of the flaps of the E (except a model seen here). But if you go to see a real one (say the E at Hendon) you will find out that the flaps as well as the ailerons are slotted just like shown in the RAE report.

[gripen]

BTW I have partially measured those particular wings of the E in the FAF museum in Tikkakoski (about 20km from here).

[Krusty]

There's a different between slotted and "have a gap underneath them"...

Slotted involves the airflow under the wing being ducted to the upper surface of the flap in question. That doesn't happen on 109E.

You see slotted flaps on modern airliners, with large gaps between the flaps, so that the air can flow through them properly. Slotted flaps (at least that I've seen) often slide backwards and downwards, more like fowler flaps.

[PanzerIV]

Did the ailerons on the 109 droop when the flaps were lowered, I saw it on Wikipedia, so I just am wondering if this was true or not?

[Krusty]

The ailerons both drooped a small amount (crap, I have it at home, can't remember how much. 10 degrees, I think?) when the flaps were fully deployed. I guess that was to supplement the leading edge slots and prevent tip stall and loss of control.

[gripen]

Originally posted by Krusty

Slotted involves the airflow under the wing being ducted to the upper surface of the flap in question. That doesn't happen on 109E.
 

It does, or why do you think the wing front of the flaps and ailerons is contoured like in the pictures above (including the one you linked) and why do you think the flaps and the ailerons are hinged from well under the wing?

Note that in Mtt documentation flaps of the Bf 109E are called as "Spaltklappe" (ailerons as "Spaltruder") while the flaps of the Bf 109F (and later) are called as "Wölbungsklappe" (ailerons as "Wölbungsklappe mit Nasenausgleich ohne spalt"). "Spalt" means gap or slot etc.

edit: corrected a typo

[Krusty]

"why do you think the wing front of the flaps and ailerons is contoured like in the pictures above"

I think they're contoured so that, as the flaps deploy, they have more surface area on the upper wing. I think they do that so as not to disrupt the flow of air over the wing and down the flap. In-game we just see a sharp corner on the 3D model. That's not very aerodynamic.

The ailerons have a similar shape to a lesser extent. They are much tighter than the flaps, and there's almost no way at all that any air will come through them from underneath. Yet they still have this shape to the wing where they attach. Obviously the ailerons are not slotted/ducted, thus the shape of the wing where they mate must be for reasons other than air ducting.


EDIT: Here's an example:
http://www.aircraftresourcecenter.com/Fea1/301-400/Fea398_Bf-109_Mustafa/images/me-20.JPG

It's a model but it's pretty close to what you see on the real thing (I just pulled a quick reference). You can see where the flap and the wing would join when the flap is fully up (as you could see on the real thing). When the flap drops, the surface under the wing rolls back, and presents a solid wall, to better ensure airflow over that part of the wing as it comes down the flap. There's no air coming up through it.

[gripen]

You see the problem; it does not matter what I say or what ever evidence I bring in, you keep your opinion which is based on your thoughts (you continously say "I think...").

The flaps of the Bf 109E (and earlier) are slotted just like shown and written in the documentation (RAE and Mtt). There is open gap between the wing and flap even when the flap is full down. And yes, I have seen the real thing.

Regarding the ailerons, below is again the plan and sections from the RAE report. Again it can be easily seen that there will be a gap between the aileron and wing when the aileron goes down (measure if you don't believe):

 

[Charge]

If the aileron has ample gap upon deflection then it is a slotted one, if there isn't then it is only a differential aileron. It seems that examining the geometry there is clearly a good gap on flap and a slight gap also in aileron. I'm not sure if it is an actual slotted aileron because the gap is not very big but the unusual hinge point supports that claim that is was actually meant as a slotted aileron. The size of the gap is probably not significant as long as there is a passage way for the pressure to the upper side of aileron. As was tested in Corsair the gap was sealed to prevent the pressure from escaping and that had an effect on aileron effectiveness.

I first thought it was a frise aileron but frise is hinged from upper part of aileron to counter the adverse yaw effect of ailerons.

***

"You see the problem; it does not matter what I say or what ever evidence I bring in, you keep your opinion which is based on your thoughts (you continously say "I think...")."

"Me thinks that the early models up to the E had slotted flaps while the F and later had plain flaps."

Heh, "Me thinks" yet you handily presented pictures of flap configurations and extractions of Mtt docs when your "Me thinks" wasn't taken for granted.  

-C+

[gripen]

Originally posted by Charge

Heh, "Me thinks" yet you handily presented pictures of flap configurations and extractions of Mtt docs when your "Me thinks" wasn't taken for granted.  

Well, one can claim something just out of the memory but that does not mean that there is not some hard evidence available if needed. Generally people tend to minimize the needed effort.

[Krusty]

I'm no aero-engineer, but I do know a thing or two about air flow from practical experience....

The 2 milimeter gap between the flap and the upper wing is NOT enough to count it as "slotted."

To be "slotted" you need enough room for a LARGE amount of airflow at speeds over 100mph, in order that the amount of air flowing through the gap keeps the lift over the flaps in extremely high AoAs.


That's just NOT the case in the 109E. I'm sorry, you're grasping at straws, IMO.

[gripen]

Well, the gap is roughly couple centimeters when the flap is down (slightly less in the ailerons).

[Charge]

"To be "slotted" you need enough room for a LARGE amount of airflow at speeds over 100mph, in order that the amount of air flowing through the gap keeps the lift over the flaps in extremely high AoAs."

I'm not sure if it was the "Aileron effectiveness NACA 868" document which considered the sealing of aileron gap in tested Corsair and according to that document even a slight gap has effect on aileron effectiveness depending of what is the aileron design, but in 109E the gap and low hinge point seem to be there to support its flap function (11 degrees in lowest position?). I'm not at all sure of how big the gap should be to have effect in slow speed.

Otherwise such aileron arrangement was probably not the best considering the stability in aileron maneuvers. Maybe a testflight documentation would have information of how unstable it actually was in rolls and initial turns.

-C+

Ed. http://naca.central.cranfield.ac.uk/reports/1941/naca-tn-808.pdf
Some info on slotted flaps compared to Fowlers.

Ed.2 Furter info on different aileron designs:
http://naca.central.cranfield.ac.uk/reports/1941/naca-report-715.pdf

Here is a doc that has nice pics of pressure changes with different flap designs:
http://naca.central.cranfield.ac.uk/reports/1941/naca-report-718.pdf

[gripen]

The RAE test pilots described the ailerons of the Bf 109E as "an ideal control" at low speeds so apparently there was no particular problems regarding stability.