Dumb questions re slats (slots)

[Tilt]

Originally posted by VO101_Isegrim

BTW, what type of slat operation the Lavochkin series had ? Swingarm or rollers?

 

Swing arms however I can personally attest to the fact that the motion was rigidly parrallel to the wing...........


see picture above...............

[HoHun]

Hi Gripen,

>I am just pointing out physical reasons why slots does not work simultaneously at speeds where they come out

I'm not suprised by the slats deploying unevenly, but that is just a transitional effect that shouldn't affect sustained turns.

The British report quoted by Badboy suggests that this makes it impossible to tighten the turn, and I don't see the physical reasons for that.

Regards,

Henning (HoHun)

[joeblogs]

Slots were invented and patented by Handley Page in UK and almost simultaneously by a researcher in Germany, who obtained a patent in that country. A very profitable cross licencsing agreement was reached.

HP came up with the idea of the automatic leading edge slat and used them on large passenger planes in the early to mid 1920s. As has been mentioned, the slats deployed when air pressure over the front of the wing reached a certain point.

The EFFECT of the slat is to allow a plane, holding constant its air speed, to attain a higher angle of attack before a stall sets in. In a turn that would mean that more elevator can be applied...

This in contrast with certain types of flap which lower a plane's stall speed, holding constant its angle of attack. This is done by increasing the camber of the wing (imagine bending a plastic straw more and more). In principal, this would allow a plane to engage in a sustained turn at a slower speed and thus a tighter turn...

Other flaps simply increase drag, increasing the rate of descent of planes on approach.

In fighters, well designed slots are preferred to combat flaps because they significantly increase the performance envelope with less drag. But, as has been pointed out, the slots might not deploy or retract in exactly the same instance...

-Blogs

[Badboy]

Originally posted by HoHun
Hi Gripen,

>I am just pointing out physical reasons why slots does not work simultaneously at speeds where they come out

I'm not suprised by the slats deploying unevenly, but that is just a transitional effect that shouldn't affect sustained turns.

The British report quoted by Badboy suggests that this makes it impossible to tighten the turn, and I don't see the physical reasons for that.

Regards,

Henning (HoHun)

Hi HoHun

The claim made in the report was that since the slots opened unevenly there was a "flick" and "slowing down of the rate of turn" I can only assume that the effect was severe enough to warrant those comments.

However, I must agree that it should have only been a transient effect, and once the slots were open, the aircraft should have flown normally for the changed wing configuration. A configuration that should have enhanced the turn, not degraded it.

But there is the possibility, that after the "flick" and subsequent reduced rate of turn mentioned above, an inexperienced pilot may have momentarily reduced the back pressure on the stick, reducing the angle of attack allowing the slots to close again, so that when the pilot tried to tighten the turn again, the whole process would have simply repeated, which would have destroyed the benefit of the slats, and the validity of the test.  But of course that is pure speculation on my part.

Badboy

[gripen]

Isegrim,
The difference between the slotted and the frise type aileron is that  slotted type aileron let airflow go through the gap all the time and some airflow is actually directed to the gap, therefore any kind change in the airflow around wing will affect to it. In the frise type aileron gap is nearly closed when aileron is centered and no airflow is directed to it so changes in the airflow affect less.  Mechanical differences between slots of the Bf 109E and later models had quite little to do with uneven opening of the slots. Otherwise I don't know if you are a right person to talk about surrealism.

Tilt,
I have no idea how to contact them, my friend got those VHS tapes from a local modeling shop here in Finland. Try google. IIRC that serie contained also types like Li-2, Il-2 and Fw 189 and some more but can't remember.

HoHun,
As quoted above, the RAE report concluded that when slots were out the Bf 109E behaved well in the turns and also in stalls. Badboys's quote appears to be opinion of one pilot (possibly unexperienced on type) and RAE results do not support his view. "Even in a very tight turn the stall was quite gentle, with no tendency for the aircraft to suddenly flick over on it's back and spin".

gripen

[gripen]

Tilt,
Look here

gripen

[VO101_Isegrim]

Gripen, I am very well aware of the difference of Frise and plain type aileron`s centre of rotation and their effect. The effect however is gradual, and should not completely cease the described phenomenon. I guess it`s just another case when you have set your mind into stone, and outright dismiss and ignore anything and everything else. Speaking of surrealism, I am a bit surprised that you actually believe the Tempest could actually outturn the Bf 109G-2/trop, whereas it could not show any real advantage in turns vs. FW 190A-4 in the same tests... I guess tunnelvision has it`s own negative effects to get the whole picture.

[gripen]

Isegrim,
The Bf 109E had slotted type ailerons, later models had frise type. AFAIK none production Bf 109 had plain type ailerons.

And please do not  make assumptions on my opinions about  AFDU tests, so far I have not presented any comments on them. If you want to find some kind of surrealism, check your own theories on aileron snatch above.

gripen

[Tilt]

Originally posted by gripen
Tilt,
Look here

gripen

Thanks:aok

[VO101_Isegrim]

Originally posted by gripen

And please do not  make assumptions on my opinions about  AFDU tests, so far I have not presented any comments on them. If you want to find some kind of surrealism, check your own theories on aileron snatch above.

Gripen,

Yes indeed you have commented on the AFDU tests, and critized me for calling them surreal. Just let`s see:

Isegrim :

Certainly such an unfamiliarity on the part of British test pilots with the plane`s major asset for horizontal manouveribilty contributed to such surrealistic result such as :

Turning Circle

The Tempest is slightly better, the Bf.109G being embarrassed by its slots opening near the stall.

and Gripen`s comment on that:

Otherwise I don't know if you are a right person to talk about surrealism.

And now:

If you want to find some kind of surrealism, check your own theories on aileron snatch above


OK, let`s put it straight as it is: stupid, primitive insult of destructive nature as a response to a comment. So I guess that means you on your hand don`t find the AFDU turning circle results surreal, or otherwise why the response that sounds like this comment hit a nerve ? Or is it just your usual self ? Having seen some of your replies, I tend towards the latter, it`s always the same pattern: Gripen tells the One and Only Truth, To Which There Are No Alternatives, then if any conflicting opinion is presented, the reaction is :
a, insulting the poster
b, ignoring, dismissing everything else
c, parrotting endlessly the same until everyone bored of it and leaves it alone... Which is sad IMHO, you have a lot of information at your hands, it`s only that tunnel vision and inability to discuss it in a constructive manner that prevents very interesting discussion to happen. Over and out.

[gripen]

Isegrim,
The AFDU tests have quite little to do with the subject (slots). I'm just pointing out that only surrealistic part of this thread is your theories on aileron snatch. Stay on subject please. Your last post contained nothing on subject, it's just a personal attack.

gripen

[VO101_Isegrim]

Gripen,

I do not wish to waste my time on such silly exchange of words. Mind you, I didnt start it...

Now, please tell why aileron snatching could not possibly a result of uneven extension of a leading edge slat that changes the airflow assymetrically over the aileron area.

[gripen]

Isegrim,
Well, you announced a BS theory on aileron snatch so basicly you started this.

The aileron snatch means that force balance between ailerons (say left and right, other combinations are also possible) somehow suddenly changes. When combined with control input the pilot gets a feeling that ailerons "snatch" ie ailerons try to reach new balance point which might be higher or lower deflection than current input by pilot (which can be anything between full and none). In the case of Bf 109E  this is reported to happen when slots came out uneven ie airflow around other aileron suddenly changes. If a slot comes out  somehow uneven along it's span the result will be just a bit softer snatch because airflow change is not as sudden as in the case of even opening of a slot. In reality a slot came out fast so even if there is some sort of  "uneven extension" the result was hardly noticeable. Basicly your theory is total nonsense and when combined with your comments  on plain type ailerons (which had nothing to do with the Bf 109) I can only conclude that you have no idea what you are talking about. BTW differences between Bf 109 slotted and frise type ailerons are presented in one of your regular sources.

gripen

[VO101_Isegrim]

Isegrim,
Well, you announced a BS theory on aileron snatch so basicly you started this.

So let`s see, I presented an alternate opinion, which fact alone is just soooooo damned unacceptable for you (HOW DOES HE DARE TO DISAGREE WITH [bME ?!!!!!), that you see it as valid reason to insult me being "surrealistic" (3 times), and my theory "BS", "total nonsense", yada-yada-yada. Massively ridiculus to blame it others, when the problem is with your attitude..    



The aileron snatch means that force balance between ailerons (say left and right, other combinations are also possible) somehow suddenly changes. When combined with control input the pilot gets a feeling that ailerons "snatch" ie ailerons try to reach new balance point which might be higher or lower deflection than current input by pilot (which can be anything between full and none). In the case of Bf 109E this is reported to happen when slots came out uneven ie airflow around other aileron suddenly changes. If a slot comes out somehow uneven along it's span the result will be just a bit softer snatch because airflow change is not as sudden as in the case of even opening of a slot. In reality a slot came out fast so even if there is some sort of "uneven extension" the result was hardly noticeable.

Did you just say/admit that in some truly miraculus way, there might be aileron snatching because of uneven opening of one slat along the leading edge?

You are definietely wrong in this, I have just read from someone who knows all and better then everyone that it`s a surrealistic, total nonsense, bull***** idea. Completely impossible, even in it`s smallest details...


Basicly your theory is total nonsense and when combined with your comments on plain type ailerons (which had nothing to do with the Bf 109) I can only conclude that you have no idea what you are talking about.

LOL, your typical self.

I would like to express that I fully agree with you. Yes, I have no idea of what I am talking about, and I would like to add, nobody else here other than You have. You are the light that leads us in our eternal darkness.
That`s what you want to hear, isn`t it ? Fine, there it is. Pleased now?

And for the note, I never said plain type ailerons had anything to do with the 109. That`s your own little surrealistic version, which you keep parrotting like mad, peppered with some derogratory comments. An attitude/behaviour I do not wish to comment on.


BTW differences between Bf 109 slotted and frise type ailerons are presented in one of your regular sources.

And the point?

[gripen]

Isegrim,
Well, if your theory is nonsense should I not tell it to you?

The form of opening of a slot (even or what ever) did not  cause snatching phenomena.

Why did you start to talk about plain type ailerons?

The point in the source for data on frise/slotted type ailerons is that it's available. There is no need for theories like you presented above.

gripen