Dear All,

I am scratch building a Feiseler Storch using Uncle willies Plans. I fully understand the function of the leading Edge Slats. As the front opening, of the slats are wider than the rear end, the incoming air is pushed towards the trailing edge of the wing there by assisting to maintain the boundary layer.

But according to the plan it seems that the front opening of the Slats which are mounted on the under side of the Elevator, is narrower than the rear opening.(which is not the same as the Leading Edge Slats.)

I would like to know the function of the Elevator Slats.

Any advice is very much appreciated.

Edward Perera.
Sri Lanka.

Hello Edward,
Can't answer your question but.......Slats move, slots are fixed. I have never heard of a slot as you describe it. A divergent duct ( what you described) would slow down the airflow rather than accelerating it and increase the pressure at the exit. Is this slot on the elevator leading edge or the horizontal stab leading edge. A photo of the plans would be helpful.
Brad

The idea is to create lower pressure along the path the air is flowing between the slat and the elevator -
this encourages the air to flowalong that path. (air flows from higher to lower pressure areas.)
Those planes were waaaaaay ahead of anything we had on this side of the pond

Hi, It sure would be very helpfull to have the plans to see this slot. But I've saw the F-4 Phantom has leading edge slots and thinking of the function of the slots I rather think those are to avoid a tail stall at a hard maneuver. Sorry, this maybe is not too much but sounds logical for me....
good luck with your proyect, send some photos.

Hi, It sure would be very helpfull to have the plans to see this slot. But I've saw the F-4 Phantom has leading edge slots and thinking of the function of the slots I rather think those are to avoid a tail stall at a hard maneuver. Sorry, this maybe is not too much but sounds logical for me....
good luck with your proyect, send some photos.

The stork flew at VERY low speeds and were extremely well designed for slow flying and pinpoint landing.
the slats were designed to extract the most lift at lowest speeds
The Bush Cubs are the present day versions of this kind of flying

It might be simply that the plan is wrong. The fixed portion ahead of the wing (or tailplane) leading edge is the slat, and it should form a convergent duct of about 2:1 between itself and the wing (or tailplane) leading edge. As suggested, the Storch was a STOL airplane, and the slat on the 'wrong side' of the tailplane was to prevent tailplane stall at high AOA's, and slow airspeeds when the pilot had the stick right back in a tailplane 'negative lift', airplane nose high situation. Which is why the tailplane slat appears to be on the wrong (bottom) side of the surface. Some of the modern Cessna's have a similar fixed slot in the tailplane, for the same reason, to prevent tailplane stall before the main wing.
Evan, WB #12.

Never seen th Stork up close - but the idea of the slats was to decrease pressure on upper surface of wings and lower surface of stab thru controlled flow.at high angles of attack
said differently - increase pressure differences.
sounds as tho the drawings are correct.
These were not like the English spring loaded thingys -were they
That design gave me the willies

I had not realized that Fiesler Storch's had an elevator slat until today either. The drawing at http://www.paoloseverin.it/download/files/Fi156.jpg shows a slat or whatever you'd call it surface attached to the elevator or stabilizer on the lower side.

This photo clearly shows this lower surface slat or sub slat or sub slot or whatever it would be called;



Yet photos of other Storchs do not show this lower side slat on the elevator. So perhaps it was an early or late feature?

three views show the slats on the stabs. I can't help think that they were aerodynamic assists to lessen stick loads.
und-foto

Allways thought slat theory said that it accelerated the air through the slot, enabling the air to 'stick' to the upper surface at angles greater than the normal stalling angle for the rest of the wing. Hence a convergent duct idea. That aside, those bits attached to the elevators are not slats, as Dick says they might be a pilot assist for the large elevator movements needed at high angle, slow speed flight.
Evan, WB #12.

Looking at the photos I have to agree. That doesn't look like any kind of slot I've ever seen. It looks like a Junkers flap but I don't know why one would be attached to an elevator. It must be a destabilizer, albeit a large one, much like those used on the modern aerobatic aircraft. The difference in size may be due to the difference in speeds. I would think that at higher cruise speeds there might be some scary snatch when moving to up elevator though!

Hi All,

Thank you so much for the prompt and encouraging replies. The leading edge slats and elevator slats are permanently attached to the leading edge of the main wing and to the elevator.

For further clarification, I have attached two images from the plans.





Thanks.

Definitely not a slot. Most likely designed to assist by reducing up elevator forces. The divergent angle it is mounted at is probably to negate any effect until the elevator is moved significantly away from neutral. This device will be completely unnecessary on your Storch as long as your servo is strong and the linkage is tight (normal stuff).......which means you can just make it look good and not worry about the shape or angle!
Brad

These are apparantly like the spades used on some modern aerobats.
The EXTRA designs and YAKS use em-A friend who has time in the EXTRAS, said that rolling maneuvers are two finger - no matter what the speed.
The angles on those are supercritical! If the plans are correct (and they look plausible) the panels are simply large "spades " which made low speed control with high power , much easier to do. I never saw these used on any prewar stuff but apparantly the Stork was way ahead of it's time
In reading up on it - at the closure of WW11, Allied brass grabbed these planes and used em for their own flights around the Germany/France etc..
The low speed performance was said to be far superior to anything the US or Brits had .
No surprise that. The Allies figured that overwhelming production would do the job and spending time developing new stuf was not part of the plan. So the planes were pretty much lightly reworked prewar civilian types. The present crop of reworked Super Cubs- used for bush flying are much the same performance -and probably a lot cheaper to produce than the Stork design .

Maybe these were for little Hanna Reich In her biography she also had trouble handling the Gigant. Maybe it should have had them too.

Maybe - at any rate they were a giant step ahead of US designers

Hi All,

My sincere thanks to all of you for your kind cooperation. Now I can go ahead with the construction of my Stork according to the details given on the plan. As this is special model the added feature under the elevator will attract so many enthusiasts, and now I could explain them the correct purpose of having it installed.

As the construction progresses I will post photos ( under the scratch building heading) of my home built Landing Gear, the modified grass trimmer Engine and much more....

Thanks again.

Edward
Sri Lanka.

What is the wing span Edward?

Looks like a consensus has already been reached on this, but here's my 2 cents. It may be a re-hash of what has already been said to this point, maybe I just didn't follow everything.

When a low-speed aircraft like this is operating at an extremely high angle of attack it is possible for airflow over the elevator itself to be completely blocked by the horizontal stab. It looks like the function of the slat in question is to get more surface area of the elevator out of the way of the horizontal stab. The aerodynamic counterbalances already perform that function to an extent, but perhaps testing proved more surface area was needed due to poor elevator response at extremely low speeds. Looks like a very effective way to achieve this without major reworking of the stab structure (probably would have been a real pain during war time!). It would only be required on the bottom unless you were planning to do a low-speed short takeoff or landing inverted.

In some ways, sure. But does it make sense to use a lot of resources to produce a huge, complicated liason plane rather than painting Piper Cubs green and enlarging the windshields? The Storch has nine linkages between the stick and the elevator; the Cub has a cable. The Storch was hard to fly and needed a skilled pilot who could otherwise have been in fighters; the Cubs could be flown by guys who had washed out of flight school. And which one do you want to fix in a hurry in a desert or snowstorm? It was (among other things) overengineered machinery like this that lost the Germans the war. Great designs that were too expensive and complex for mass production and tricky to maintain in the field. The Russians made simple, cheap planes (like the Yak 3, with plywood wing skins), but they made a lot of them. Sometimes being a step ahead is not an advantage.

Sorry mjfrederick, it must have been the other way around. Even the prototypes have the elevator slat (see [link=http://www.youtube.com/watch?v=VDcB0pSUYOI]here[/link]). The drawing linked in post #9 shows the cambered cross section of the slats quite well (just enlarge the side view), and the Italian comment next to the bottom view says "omitted in the last versions". Information is scarce but says just that and that the first prototype had both too little elevator effect and too much elevator stick force. Don't know if they later modified the whole stab.

I agree that the Storch is overengineered compared to American types, but these linkages were quite common in German aircraft. Again, there have been built not that much Storks, only for special tasks. There were other, simpler or faster liason aircraft.

Interesting, UStik, thanks for the insight. Always good to get insight from someone a little closer to the source.

Plenty of opinions as to who did what the best
When the war was over - Both the US and the Soviets raced to see who could grab the German scientists and hardware which related to rockets and advanced aircraft. That is a cold hard fact- we grabbed all we could and so did the Ruskies
It wasn't the german machinery designs which lost em the war -equipment wise, they had just about all the advanced stuff.
I can't find any referrences to STOL stuff, prior to the Stork.
By the way- if you look at the video of th demo flight an dnote the actual angle of flight plus th angle of th e elevator and "spade", you will see a pretty close correlation.
NASA did somestudies I remember which showed that stabilizing extreme angles of flight worked best , when the angle of the tailplane and the angle of descent were the same - but then that just makes sense.

Actually the allies often commandered serviceable Storch's, even Monty had one. So they were quite appreciative of the types capabilities...
evan, WB #12.