Steve Wittman had leading edge FLAPS (not slats) on his Buttercup.
Buttercup is a predecessor to the Wittman Tailwind.
That was back in the early '50s?

Anyway, the idea is to have a thin wing for high speed cruise and
recontour it into an undercambered thin wing to slow down for landing.

Thin airfoils tend to have low CLmax while recurred thin airfoils
can have amazingly high CLmax.

Taken to an extreme, the "sail" type single surfaced ultralight wings
show a CLmax of over 4(!)

Leading edge flaps are always(?) deployed in conjunction with trailing
edge flaps of some kind. Even if it is a simple split flap.

Otherwise, the CP would move way forward, and the chord line suddenly
goes the wrong way.

Earl Luce built the first replica Buttercup (and sells plans fo it too).

Earl said Buttercup lands in the low 40s with the flaps down.
Or over 70 (with a lot of skipping and skating) without them.

I did a little browsing at the NACA server and found a lot of info on
leading edge flaps. But it all seemed more applicable to supersonic and
high subsonic heavies.

To date, Buttercup is the only light plane I know of that has leading
edge flaps.

Richard


Peter Dohm wrote:

Brock wrote:

I feel there is a real advantage to the use of slats and flaps in
order to have things happen slowly during landing and yet still have a
good cruise speed. Of course the problem is in the complexity and the
extra weight. For rails I was thinking about something like standard
kitchen drawer rails or perhaps a tube within a tube design. I
wouldn't think their would be a lot of force on the slat at low
takeoff speeds so the structure wouldn't have to be bullet proof,
their would probably be a lot more force on the flaps though. I
haven't been able to find information if the necessary airplane
hardware is available commercially, perhaps it would have to be custom
made. Any ideas on how to go about building something like this?

Brock

Whereas the Helio Courier and Morane Rallye (among others), and their
slats, are discussed elsewhere in the thread; I'll just mention that all
of the high wing Cessna aircraft with which I am familiar have single
slotted Fowler flaps. I have no idea how much performance you would
gain with double slotted Fowler flaps, and doubt that they would add
much weight; but believe that they would be a real pain in the neck to
build s the dimensions would need to be held closely in order for the
slots to have the correct proportions and the additional surfaces would
need to be finished.

Peter