There's a C206 Amphib parked on the ramp at my airport.
It has a leading edge cuff, looks like probably a Sportsman (no wing fences), and VG's.
It also has fences at the inboard end of the ailerons, never seen these before.
I haven't been able to meet up with the owner to ask him about them,
so thought I'd ask the gang here about them.
Here's a pic:

Hmmm, interesting.

There's a fair amount of spanwise flow on a wing. I know a guy with an experimental supercub that put fences that go above and below the outboard edge of his flaps. Says it increased his roll authority and lowered his stall speed. That's kind of anecdotal. I'd love to get my hands on it and do some with/without back to back testing.

Never seen them on a certified Plane either. Be curious to know if they were STC’d with the other mods.
Got fences on both ends of my experimental ailerons. because of differential throw to deal with adverse yaw , most planes get more throw up than you do down. I’m sure most know that fences work like a box blade, (for those of us who mess around on the farm) . Unlike a straight blade it ,captures everything and keeps it from having any spillover , Making it more effective when it is deflected.

Those were added to the U-206 with the H model, after production resumed. I'm not sure of their function, but it appears they prevent spill off the end of the ailerons. None of the earlier models have them. The H model was a re-certification, and eventually went to 3800 pound GW, at least on some of them. They're also the only 206s with Lycoming engines.....same company owns Lycoming and Cessna.....

MTV

Even with a rectangular wing, flaps increase spanwise flow to ailerons when in use. This can increase aileron authority to a point. But as the stall is approached, the boundary layer gets larger, diminishing the effectiveness of the ailerons. The fence typically stagnates the spanwise flow, and the boundary layer tends to be thinner on the outboard side, improving aileron effectiveness. The data for impacting actual stall speed is pretty mixed/nonexistent, but it can at least sometimes yield benefits for aileron effectiveness deeper into a stall, even with a rectangular wing. The benefits are much larger for swept wings.

mtv wrote: Those were added to the U-206 with the H model, after production resumed. ….

Googling the tail number, this one appears to be a 1967 U206B.

It is a standard part on the 206H, listed in the parts catalog. There are several small subtle changes in the H model. However a gross weight increase is not one of them, if you look on Type Certificate A4CE, which covers the 206H and all its brethren, there are none that go over 3,600 lbs.

I like stall fences, I have had them on my 185 with Robertson, a 206 Soloy, Twin Otter and such. I am surprised that most of the STOL kit makers do not use them more, they actually help. According to one of my friends that used to work in the Cessna Test Program. Cessna goes out and buys a bunch of different STOL kits. They try them under controlled conditions in instrumented aircraft that they have very accurate baseline information on. According to Scott, many really didn't do much of anything, some helped but most did not do much that would warrant any design changes that would have made much of marketable difference, without necessitating re-flying the certification deeply. When they found something that really did something, they did the Microsoft thing and incorporated it in the design, re-did the TC. The cuffed leading edge for example.

When they did the engine change, you have to spin certify the cowling, which is different. So these where probably added for either spin, which is a weird spin mod, or when re-certifying performance at gross weight at full forward or full aft CG. Rules have changed since the G model came out for certifying both regimes. This certainly was an inexpensive mod ($124, my price) and did the trick.

hotrod180 wrote:

mtv wrote: Those were added to the U-206 with the H model, after production resumed. ….

Googling the tail number, this one appears to be a 1967 U206B.

Maybe the float STC requires these, but only place I’ve seen them is on H models. Take a picture of the cowling and post it.

MTV

Definitely not an H model.

Aerocet floats, and I’ve no experience with the 206 on them, maybe a requirement? Or maybe a set of H model wings on an early airframe.

Who knows.

MTV

Like I said.....

hotrod180 wrote: Googling the tail number, this one appears to be a 1967 U206B.

Data plate on fuselage concurs.

Perhaps not a Sportsman STOL cuff - I did not see the requisite aileron gap seals?

Talked to the owner of the 206 today,
he bought the plane as is (except for the beautiful new paint job,
courtesy of Upper Valley Aviation in Chilliwack).
He thought maybe it was part of the Sportsman kit.

And I'm pretty sure it's a sportsman kit--
it's definitely an add-on cuff (you can tell by looking at the landing light opening)
and the sportsman is the only one I'm aware of that doesn't incorporate wing fences.

pilot wrote:Perhaps not a Sportsman STOL cuff - I did not see the requisite aileron gap seals?

Stenez website sez no aileron gap seals on the 206/207 kits.

hotrod180 wrote:

pilot wrote:Perhaps not a Sportsman STOL cuff - I did not see the requisite aileron gap seals?

Stenez website sez no aileron gap seals on the 206/207 kits.

Ahhh. Looks like Sportsman in the pics too.

pilot wrote:Perhaps not a Sportsman STOL cuff - I did not see the requisite aileron gap seals?

Can you (or someone) post a photo of the sportsman aileron gap seals? Thanks.

No pic - sorry. Aileron gap is sealed with a strip of .025 with about a 1/4" downturn trailing edge. Drill out rivets along trailing edge, the "gap seal" strip is inserted between wing top and bottom skin and adjusted to an .020 gap when aileron is up. Drill, cleco and re-rivet - usually after removing aileron.

Can you (or someone) post a photo of the sportsman aileron gap seals? Thanks.[/quote]

Thanks MIke.