# Spinning an Icon

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#### Topaz

##### Super Moderator
Staff member
Log Member
...As for mooring, can't you moor it at both the sponson and the nose, so it lies with a 45 degree angle towards a pier and you can easily step off the sponson?

Why can't you beach it? Not enough static thrust? Or is it impossible to extend the landing gear while floating?
I think the point that Aircar is getting at is two fold, both related to the forward-hinged canopy:

For one, if you tie up at a dock, even at a 45° like you're saying, the canopy gets in the way of tying up the forward line. For another, if beaching the aircraft, you have to exit over the side, getting your feet wet and dirty. And that counts in both directions - you'll be tracking mud and water into the cockpit when entering, too.

Both of these are reasons that the Osprey II had a rear-hinged canopy. A lesson the Icon folks seem to have ignored.

#### AirSharkII

##### Well-Known Member
I think the point that Aircar is getting at is two fold, both related to the forward-hinged canopy:For one, if you tie up at a dock, even at a 45° like you're saying, the canopy gets in the way of tying up the forward line. For another, if beaching the aircraft, you have to exit over the side, getting your feet wet and dirty. And that counts in both directions - you'll be tracking mud and water into the cockpit when entering, too. Both of these are reasons that the Osprey II had a rear-hinged canopy. A lesson the Icon folks seem to have ignored.
You can dock like in the photo. It's not easy and the wind needs to be just right or none at all. The most secure is to run it up the beach. The Icon with it's tricycle gear will stuggle with this, though. The SeaRey does a better job beaching with it's larger tires and tail wheel configuration. Tracking mud and water into a cockpit is just part of seaplane ops. You fly in sandals and carry lots of towels Most Seaplane pilots fear a forward or rearward hinged canopy when thinking of being upside down in shallow water!

##### Well-Known Member
For one, if you tie up at a dock, even at a 45° like you're saying, the canopy gets in the way of tying up the forward line. For another, if beaching the aircraft, you have to exit over the side, getting your feet wet and dirty. And that counts in both directions - you'll be tracking mud and water into the cockpit when entering, too.
Well, it's clear I'm not very familiar with small boats. Thanks for pointing that out

#### ccg

##### Active Member
. . .wouldn't the outer half of the flaps be too far outward of the prop to be influenced noticeably? It looks like even the root of the flap is already outside of the diameter of the prop.
You might be right. There is no way to be sure unless you know the exact intake flow into the prop. I was thinking that the intake area into the prop is much larger than the prop disk. Particularly with the engine cowl present and a high angle of attack, there would be significant lateral flow component into the prop over the top wing surface. It might extend further out than expected. Its effect would be to delay separation. It's only speculation on my part, but I just wanted to point out that the flow would not correspond to a straightforward planform that you might assume for design purposes.

I noticed that their half section wing tunnel model does not account for prop flow so they must assume its effect is fairly insignificant.

#### Himat

##### Well-Known Member
Isn't it possible to stand on the sponsons?

From the picture it looks like it.

As for mooring, can't you moor it at both the sponson and the nose, so it lies with a 45 degree angle towards a pier and you can easily step off the sponson?

Why can't you beach it? Not enough static thrust? Or is it impossible to extend the landing gear while floating?

Mooring 45 degree to the pier.
That is ok if you can put the wing over the pier and there is enough clearance. If not the wing will be dented, maybe in the moment you step on the sponson and the plane roll to that side.

Steping on the sponson.
Ok if the sponson have the strenght, enough bouyancy to not give an abrubt roll, a no skid surface and you are able to place your foot there. If not egress might be less than graceful.

Forward hinging canopy.
Front hinged and you cant easily walk over the nose of the airplane.
Both front and rear hinged canopies is less than optimal if ditching upside down in shallow water. I do think the "emergency egress" thread pointed at more optimal solutions. To end up upside down under water in an aircraft is no funn. If you think so try the helicopter ditching simulator. (I have tried, it was part of the training when traveling offshore with helicopters in the north sea.)

Hull design.
As far as I can see the Icon is a traditional design with traditional shortcommings and traditonal plus sides. I would have done it different as I tried to show in the "Alternative take on hull design" thread.

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#### Pat Brett

##### Member
The NACA 2412 uncuffed and cuffed:

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#### Aircar

##### Banned
Firstly-I spent many years working on the rear prop driveshaft problem (and corresponded with Molt Taylor, Hanno Fischer and locally the designers of the FSRW1 amphibian which had dual shaft and belt driven props --and went through something like 30 different drive system evaluations plus studied the work of over 60 previous tailprop designers as far as the literature covered such things --also was personally in contact with john hart smith was was intimately involved with the Learfan development (and also through the local 'dealers' Transectutive whose aircraft I used to look after and upgrade for sale etc ) it maybe I could help but you might equally have taken a different tack and have the engineering sorted out beyond what I had done . In the great spectrum of airplane configurations the roadable field is the one that just about demands remote drive in at least one mode and also is least suited to conventionality in all other respects -- a tinkerer's or inventor's dream or nightmare depending on how you look at it ..

With respect to entry and exit from water -- I do not like the rear pivotted clamshell option (eg Pierea Osprey -helped a bit on one ) because it prevents access to the engine on the water amongst other things (or at best requires a hands and knees crawl at some risk) --the forward pivot is simpler but the way the Icon is set up gives a too short opening to slide the legs in easily and anyway loses the possibility of a panoramic forward view --one of the real pluses for a rear engine aircraft .

On the Opal I had a broad nose with enough volume to allow stepping through the nose without swamping and the canopy was side hinged -from both sides . --as in some sailplanes where you have spring loaded for and aft moving hinge/retaining pins that can be used together to jettison or allow stepping in from either side . the instrument panel had two 'wings' hinged vertically that just rotated horizontally to give a clear path forward (centre stick ) --and easy access for maintenance . Anyway you get unimpeded access to the rear for engine access and troubleshooting etc (with the overwing cover easily removed on the water even for the mid engine -oil check etc ) I'll see if I can scan one of the old cutaway drawings . If you have done a bit of kayaking or small boat ('duck punt' type) messing around the niceties of getting in and out from a river bank or muddy shoreline without tramping mud are known to you --for a kayak we got the nose pointed down and 'rowed' into the water where possible pushing off with the paddle on the grass or mud and beaching a flat bottom boat with walking forward to jump out or push off is much the same idea as with a small amphib .

#### Rick McWilliams

##### Well-Known Member
I fly a Mermaid amphibian. It has the general layout of a Lake Buccaneer, mid wing and a high cruciform tail. The wing is right at dock level so the docking "option" is at the corner of a dock. The ICON sponson looks better for docking. Tricycle landing gear works well for beaching. The steerable nose gear gives some steering control at first contact. The comparatively large tires and low gross weight work fine on sand. Static thrust will push it up a very steep ramp. I try to have room to turn around for an easy departure.

#### Aircar

##### Banned
The NACA 2412 "cuffed and uncuffed" profiles sure don't look like they are --I cannot read any of the text or figures but it seems to miss the point about the leading edge extension concept ( which is similar in principle to the Rao slot,Vortilon,Dogtooth,fence, etc ) which is a 'three dimensional' thing using a chordwise vortex or discontinuity together with the drooped nose . Orion made a comment about the Icon embodiment not being effective a little while back which he might like to expand upon (?) --

I don't know when the first use of a stepped leading edge was but it goes at least as far as the Supermarine swift and I would not be surprised if it was a German WW2 innovation (of course the Ailua (sic) 'bastard wing' as it is sometimes called on a bird's wing is essentially doing the same thing and the external claws on a Pteranodon probably served the same purpose -also the Archeopteryx had the claws still as does the South American leaf eating bird (can't recall the name) and bats --some whales have an 'undulating' leading edge that seems to improve maximum lift by delaying separation and that was mooted to be under consideration for wind turbines and helicopter rotors (the British "BERP" tip already does some of it as does the Cartercopter delta type tip with jog ) It is surprising how long it can take for well established inventions elsewhere in aviation to filter down to light aircraft and then be described as new --vortex generators are the latest revival fad of this kind.

Back to the Icon sponsons and getting in and out -- standing on a sponson doesn't really help with avoiding the tidal zone muddy area or places like hydro power lakes that have a 'dead zone' and the situation on a lot of rivers that have banks where being able to nose in and walk out through the nose is the only option ( I seem to recall that the SeaBee and Spencer aircar had side tilting front canopy sections for this reason and perhaps the Riviera -- some of old flying boats had a mooring station right up front also .

#### Pat Brett

##### Member
The black line is the NACA 2412 and the red line shows the NACA 2412 with a cuff. It was run in XFOIL. It shows that the cuffed section maintains the same zero lift angle, but can reach a higher stall angle, improving the stall of the outboard wing. The zero lift angle is maintained because the drooped LE increases the camber but also decreases the angle of attack.

At greater then Cl = .6 the cuffed section makes less drag. The cuffed section also increases the Cm by about 30%.

The discontinuity in the cuff is an important feature. At high lift the vortex made by the cuff creates a "wall" between the inboard wing and the outboard wing. The outboard part of the wing performs like a low aspect ratio wing, and is able to fly to higher angles of attack.

#### orion

##### R.I.P.
Cuffs, leading edge extensions or the classic dog-tooth leading edge are all fixes for either a poorly designed wing or an attempt to control an unforeseen behavior. Extensions as seen on the Cirrus and here on the ICON are designs that are more commonly applied to swept wings where the discontinuity in the leading edge line, combined with a span-wise flow common to swept wings at high aoa, create a vortex flow that stabilizes the boundary layer and flow over the ailerons, thus enabling improved roll control into stall.

For straight wings meeting the control requirement is a bit more difficult - here the goal is to configure the cuff in such a way so as to maintain a stable boundary layer to higher angles of attack through the use of improved geometric gradients. In essence, the purpose of the cuff is to approximate the same behavior we would have with an aerodynamic twist, where the boundary layer control is tailored through the use of different sections at the root and the tip (straight wings have little or no span-wise flow, even at higher angles of attack, so the vortex flow effect of the extension does not come into play). This control can be achieved several ways when first designing the wing but is much tougher to realize if you're working off (fixing) a given planform. The aforementioned Grumman program was an excellent example of this fix in that the NASA configuration worked very well. The modification for the two place aircraft was relatively simple in that in worked off of the existing 65-415 section of the Yankee by extending forward a level tangent from the bottom surface and intersecting an extrapolated leading edge gradient from the top. Where the two met a radius was incorporated similar to that of a 2412 (there was a bit more to this but I no longer have the published papers so cannot reference). The result was sort of a combination of an aerodynamic twist combined with a small amount of physical wash-out and resulted in full roll control well into stall.

It looks like the ICON's configuration is closer to the shape developed by NASA, as opposed to the one developed for the Cirrus wing, although it does not seem to modify the geometry far enough to achieve increased positive control (of course I'm guessing here but it does look to be measurably different from the original NASA work). The new section looks to be nothing more than a simple offset off of the base section with little or no change in shape or chord line. It seems fatter and the gradient is a slight bit different but I really don't see a significant improvement over the original wing line. I'm sure there is some benefit but possibly not to the level they might have hoped for.

I think an improvement would've been a new, better designed wing or a continuously changing extension from root to tip, similar to that seen on STOL modified 185s.

#### Pat Brett

##### Member
This is one of the NASA papers:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19800004771_1980004771.pdf

SUMMARY OF RESULTS
Flight tests have been conducted to determine the effect of wing-leading-edge modifications on the stall/spin characteristics of a light, single-engine,low-wing, general aviation airplane. From the flight data and pilot observa-tions, the following results have been obtained:
i. Stall behavior of the test airplane with outboard leading-edge droop(without a fairing at the airfoil discontinuity) was much improved over that of
the airplane with no leading-edge modification.
2. Regardless of the entry technique employed, the spin mode of the air-plane with this outboard leading-edge droop was characterized by a steep, slow,
spiral-type motion from which recovery was effected immediately by relaxingprospin controls.
3. A tapered fairing to eliminate the airfoil discontinuity at the57-percent semispan location did not alter the improved stall characteristics,
but eliminated the improvements in spin characteristics realized with the dis-continuity present.
4. Full-span leading-edge droop resulted in markedly poorer spin charac-teristics: the airplane would readily enter a fast flat spin from which norecovery was possible with the normal controls.
5. The stall/spin characteristics obtained during the flight tests sub-stantiated the results predicted from the radio-controlled model flight testsconducted for the same configurations.
Langley Research Center
Hampton, VA 23665November 19, 1979

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#### orion

##### R.I.P.
That was the paper I was referring to - nice find. Thank you.

One interesting thing that came out of this work was that contrary to my statement above, this particular low aspect ratio wing on the Grummans did actually see a surprisingly high level of span-wise flow at high angles of attack. It apparently surprised the investigators also - they concluded that this was unique to the Grummans due to their particular geometry. No other airplane they tested demonstrated this phenomenon, not to this level anyway.

##### Well-Known Member
After the recent downright hilarious battle over a weight exemption (Icon wants 200 lbs higher MTOW for a "stall-proof" wing, must be heavy cuffs...), they've completed another "final round" of investors, bringing the total investment to considerably over 100M US$: A final round of fundraising has netted Icon Aircraft$60 million in investment capital to support “regulatory compliance” and ramp up production of the new A5, the Los Angeles-based company announced June 20.

“We are thrilled to have the support of such a distinguished and passionate group of investors,” said founder and CEO Kirk Hawkins in a news release. Icon raised those dollars from investors in North America, Europe, and, for the first time, Asia, the company noted. While not naming names, Icon reported the Asian investor is a multibillion-dollar conglomerate well established in China’s general aviation industry.

There has been no word, yet, from the FAA on Icon’s request for an exemption to the light sport aircraft weight limits. Icon cited safety benefits including a spin-resistant design in seeking a 250-pound increase to the LSA limit for amphibious aircraft. A competitor’s complaint to Speaker of the House John Boehner (R-Ohio) has meanwhile triggered a congressional inquiry into the weight exemption request.
Icon has collected nearly 1,000 deposits on the A5, and Hawkins thanked those early buyers for their patience amid delays, according to the news release.
“This has been a longer and more challenging journey than even we had anticipated; that said, ICON is now in a great place,” Hawkins wrote. “For everyone who has kept the faith, remained a great wingman, and waited patiently for the A5, you’re going to get the most amazing sport aircraft ever created.”
Icon raises $60 million to produce A5 - Aircraft Owners and Pilots Association How on earth can it take 10 years and 100+ Million US$ to design a plane that's not appliceable to unchanged regulations, while they can hardly get it to spin safe at all. Sounds awfully close to some other "revolutionary" planes...

#### topspeed100

##### Banned
After the recent downright hilarious battle over a weight exemption (Icon wants 200 lbs higher MTOW for a "stall-proof" wing, must be heavy cuffs...), they've completed another "final round" of investors, bringing the total investment to considerably over 100M US$: Icon raises$60 million to produce A5 - Aircraft Owners and Pilots Association

How on earth can it take 10 years and 100+ Million US$to design a plane that's not appliceable to unchanged regulations, while they can hardly get it to spin safe at all. Sounds awfully close to some other "revolutionary" planes... I wonder that too.....FlyNano is testing again their new model..but in total secrecy. #### cheapracer ##### Well-Known Member Log Member How on earth can it take 10 years and 100+ Million US$ to design a plane that's not appliceable to unchanged regulations, while they can hardly get it to spin safe at all. Sounds awfully close to some other "revolutionary" planes...
Simple business calculations for returns is $45K per unit, divide that by a profit over time margin of 3 for them as their advertising investment is high profile, so round it off at$20K nett profit for each unit giving a bit of leway their way.

Now divide $20K into$100 million and there's 5000 units that have to be sold in short time before profitable returns, hell give them the bebefit of the doubt and they make a clear $30K per unit still leaves 3300 units to be sold, again, that's before profits start coming back and only if everything goes smoothly and you sell enough units constantly - and this is all for a very niche low volume market, come on, seriously, how stupid are people ????????? What you will see is constant "Wow!!" factors like the "No Spin!!" and other amazing innovations announced constantly, this is a ploy used to keep investors excited and to look like the company is always moving forward and on top of things. Did I mention sca, errr, scheme? Sadly it's by far from the first time or the last and it's especially sad to see Pensioners chuck their life savings into these things and I know that from personal experience. #### PTAirco ##### Well-Known Member I think maybe there is hope, after I read about the Thielert engine guy getting arrested for deceiving investors. It ought to happen more, which is not a good thing. If investors start hearing about these futile aviation start-ups that do nothing except produce promises and suck up money, it will hurt all those with a genuinely good business idea. It's hard already - it has always been hard - to convince people to put money into any aviation product - I can only see it getting worse. If you look at the kit industry as a whole, almost all those who began with fanfares and getting investors and R&D and marketing teams etc, have gone belly-up. What is left out there is usually those companies where one guy had a good idea for an airplane and started in his garage and grew from there. What I want to know is how investors can be so gullible?$100,000,000 ??? I swear, you could give me $1,000,000 and I'd give you a couple of flying prototypes with all the problems sorted and paperwork done. Another couple of million for tooling and a factory. Somebody point me at these "investors", PLEASE! #### PTAirco ##### Well-Known Member Did I mention I have an amazing idea for making ANY airplane "virtually" spinproof? It's called an elevator stop.... #### autoreply ##### Well-Known Member If you look at the kit industry as a whole, almost all those who began with fanfares and getting investors and R&D and marketing teams etc, have gone belly-up. I don't seem to recall a single company that started with the fanfare and actually turned out a success? 0% success is a pretty strong argument against all those publicity stunts :speechles What I want to know is how investors can be so gullible? I guess the same things that killed all those docters in the Bonanza and now in the Cirrus. Being rich might give a feeling of superiority and invincibility, such that by definition they know it better than the common engineer. Listening to the stories about Adam, Grob and Saft (Dreamliner), all those failures where predicted years ago by engineers that worked there. Reading the older stories about the Starship for example, the more outspoken engineers simply get removed and replaced by yay-sayers... Well, it's comforting to see that the ones that actually achieve something (Van Grunsven, Musk, Pelton, Monnett) are modest and welcome criticism... What I want to know is how investors can be so gullible?$100,000,000 ??? I swear, you could give me $1,000,000 and I'd give you a couple of flying prototypes with all the problems sorted and paperwork done. Another couple of million for tooling and a factory. Somebody point me at these "investors", PLEASE! Start here: http://cbsg.sourceforge.net/cgi-bin/live #### Holden ##### Banned A few words about spinning, not the marketing type of spin, but the fun type. If you look side ways to the ICON and imagine it dropping into the flow post stall with an AOA of 40-60 degrees, what do you see? I see the "sponsons" blocking the tail surfaces. I see the rear tail boom blocking the flow into the vertical tail. I see the tail swept back and nearly parallel to the flow making the fin useless. How can a fin on the tail create a force counter to the rotation when the flow is going nearly spanwise and not chordwise? Houston, we have a problem that is plain to see...except for people with$100 mil to burn.

To make an airplane do deep stall, the tail needs to be from the top and swept DOWN and back, not as the ICON does it, and it needs to not be blocked by the body. A twin boom with verticals going DOWN and back would solve their spin problem.

Looks wise my concept would not get the go ahead, but functionally it would work.

As for spins, every fun airplane should be able to enter and exit a spin by command. Spins are a lot of fun, especially when they are fast! An airplane that cannot spin is like a muscle car that can't do spin outs and smoke tires. All hat no cattle. Why bother? Not sexy. Just a waste of money. If you want to take a lady for a "spin" in your airplane, you at least should start with a real airplane spin. All real pilots know how to spin and recover. Then she will know you are able to perform, as it were. :ban:

Holden