109G/la-5/7 and the slats

[GScholz]

What are you babbling about? The slats deploy before the wings stall, with a safe margin too. Unless the pilot doesn't notice that only one slat has deployed there is no problem. All he have to do is keep the plane fast enough so the wing doesn't stall.

[niklas]

the main purpose of slats is to make the aileron section stall later than the inner wing section, and nothing else. So you can keep aileron / airplane control.

In rough turns the effect may come to late so the aircraft stalls before you can benefit of the slats. Or they pulled the aircraft so much that it get stalled in the outer section even with slat effect. I wouldn´t give too much on pilots opinion why the aircraft did spin out of a turn. Fix the slats in closed position and let them fly it again, i´d like to hear their opinion now!

Cessnas have to be cheap. And when takeoff distance is always longer than landing distance due to the low power output and a fixed prop with poor efficiency at takeoff, there´s absolutly no necessarity to lower landing speed even more. Imo it´s low enough. Do there many landing accidents happen with Cessnas?

niklas

[GScholz]

As for the types, dunno exactly. The top one looks like a Curtis design. The red and blue one is French I believe and the two others are Czech.

[GScholz]

Btw. didn't mean to be rude Angus. Sorry.

[Angus]

Hey Scholzie, NP mate

As for the Pilots opinion, I asked Rall whether he heard of any pilots fixing their slats. He said "NO"
I asked him if he would rather not have had them, he said they were necessary, without them the landing speed would have been too high. (?!)
He added "But I did not like them in combat"

[Angus]

Oh, and for Niklas:
"Cessnas have to be cheap. And when takeoff distance is always longer than landing distance due to the low power output and a fixed prop with poor efficiency at takeoff, there´s absolutly no necessarity to lower landing speed even more. Imo it´s low enough. Do there many landing accidents happen with Cessnas? "
I wonder, do you fly?
Anyway, those aircraft piss me off a bit, for you have something rather light in your hands with very little power, It stalls at roughly the same speed as a 3 ton WW2 fighter!!!
I live beside a countryside runway, some couple of years back a Piper used all 800 m. of runway without getting airborne. Well, it was actually a pilots mistake, but there was not much margin for cancelling anyway.
I have to disagree with you about the landing speed. Just 10-20 kts make a heck of a difference. Can't remember the exact figure, but an educated-from-memory guess is that the difference between a 50 kts and a 70 kts crash is a double one in fatality.
So, those slats at low speed are really worth their weight!
Sometime ago I posted a pic of a Dornier private aircraft, post war. I think it is a 6 seater. It has slats (fixed perhaps?). It stalls at 27 kts! Now that is something for security.!!
I'll try to find a pic of it to post, - one beautiful bird in LW colours.
(BTW, the owner is an old skipper from the DC-4 and DC-6 days. He survived from smashing into a glacier on full cruise in 1954 or something near that)
So, goodnight gents.

[niklas]

Imo a very slow aircraft is more vulnerable to wind turbulences than a faster one, because realtion wind speed to aircraft travel speed becomes higher. And imo wind effects are the main cause for accidents during landings. So imo it´s not too desirable to land at very low speeds.  For example, when front wind of 30mph suddenly becomes zero and your landing speed is 60mph, you lose suddenly 75% of lift. When you land at 90mph you lose only ~55% of lift. The same principle applies generally to the effectiveness of the control surfaces.

i did fly around with a Cessna once, got also the control. We did some manoevers, kind of wingovers and also tried to stall it. Absolutly no problem and very gentle at low speeds

niklas

[Angus]

You have this the wrong way around.
On a short field especially, low stalling speed is worth a lot.
Low landing speed is good, that's why pilots land at almost as low speed as possible.
Do you fly?

[niklas]

You don´t understand my logic.

The landing distance of the airfields we talk about is always long enough because takeoff distance is the critical distance. An airfield that is so short that you can land but not takeoff is useless, agreed?

A fw-190 jabo pilot wrote in his memories that his squadron leader forgot to use flaps during landing. He overshot and disappeared in a fireball. THIS is a short airfield, where no flaps make you overshoot the runway! Well those powerful ww2 fighter maybe needed less takeoff distance than landing distance (have to check sources). For Cessnas it´s inverted.
Furthermore i´m sure that airfields are only cleared for special aircraft types if they offer plenty of safety distance, except we talk about some lost places in the rain forest...

In normal cases you want to land as slow as possible, nevertheless i´m convinced that a very low landing speed is more critical during gust wind than a reasonable high one. I don´t want to say that Cessnas should land with 150mph! Nevertheless: The higher your speed is compared to wind speed the more safe you are against changes in wind speed, logically!

And once more, the landing speed of a Cessna is already so low AND the approx. rectangular wing design let the outer wing section naturally flies at a lower lift coefficient than the inner section (see pic) that slats are not necessary at all!



niklas

[Angus]

Not quite agreeing although I see your point.
Cessna's, no matter what you say, don't stall too well. They dip a wing, and there is no problem provoking a spin.
A Cherokee is however the opposite, it just plonks down at the stall.
Landing distance for those little ones is if anything somewhat lower than takeoff distance, it quickly turns around with some more speed and power.
If higher landing speed is safer, a lower stalling speed is still positive. You want the stalling speed to be lower than your landing speed, yes?
If not, what are slats good for anyway? I asked Rall whether he would have had his slats shut for he did not like them in combat, and he said NO, without them the 109's landing speed would have been unacceptably high.

[Kurfürst]

Originally posted by Angus
If not, what are slats good for anyway? I asked Rall whether he would have had his slats shut for he did not like them in combat, and he said NO, without them the 109's landing speed would have been unacceptably high.

If Rall thinks the only reason the slats were there on the 109 and others to improve landing characteristics, then he is simply wrong. He is no engineer after all, just a pilot, and probably won`t go into a lenghty in detailed discussion lasting hours just on slats when somebody asks the same question the 1345th time..

The moral of the story ? Rall didn`t like slats, while others like Stiegler did like them. Any progress made? No. Unless one consider Rall the one and only source for everything, like angie does.

[niklas]

Originally posted by Angus
[BCessna's, no matter what you say, don't stall too well. They dip a wing, and there is no problem provoking a spin.
A Cherokee is however the opposite, it just plonks down at the stall. [/B]

I was flying in a Cessna where the pilot provoked a stall and it was very gentle and controllable. He said however that he wouldn´t do it with a low wing design (Cherokee?). So i can´t follow your points.

In case of a rectangular wing slats don´t really delay the stall. Stall happens there in the inner wing section first see pic. Assuming slats would give you even more angles in the outer section: What´s worth a stalled situation where you drop like a stone because lift has broken down completly in the innersection, but you still can keep the least amount of control in the outer section? It´s not desirable that pilots enter such a situation, if the airplane begins to shake they should know to drop the nose rather than pulling even more.
Full wing slats would be something different. The fieseler storch repliqua i saw at an airshow did almost fly like a heli.

Does the Cessna has some kind of boundary layer fences on the top? Way simpler, also very effective. Not as good as slats though.

niklas

[Angus]

Oh, the points:
"I was flying in a Cessna where the pilot provoked a stall and it was very gentle and controllable. He said however that he wouldn´t do it with a low wing design (Cherokee?). So i can´t follow your points. "

My point is that the i.e. C172 or even the 152 will with a power off stall dip a wing and enter a spin.
The Piper will just dip itself. Been at it some times, the thing is rather unwilling to enter a spin at all. In one case it just dropped, in another, which was a rather rough one, it just fell nose down with hardly any bank at all, then recovered quite quickly.
The person in the back seat was not buckled and not aware of this, - she hit the roof quite heavily!
BTW, in my rides on those, we always land on the BUZZ.
I'd love to land with 10-20 kts yet to go to the buzz if you see what I mean.
That Dornier I mentioned is a beauty. I'm trying to find an online picture of it. You'll love it
Stalls at 27 kts.

[Angus]

Here is that pretty Dornier I was referring to

[Angus]

Oh, no.
Try this link:
[url]http://www.islandia.is/aeroweb/islenski_flugvefurinn/mulakot