Icon Aircraft, the company that’s making the Icon A5 LSA amphibian, has put out a video explaining and demonstrating what their design can do. It’s impressive.
A while back I wrote a blog that was critical not of Icon’s laudable efforts at aerodynamic progress but of the fact the company was unclear in explaining exactly the relationship between its airplane, an LSA, and Part 23 certification.
Sadly, the video we hope you watch from Icon again does not make it clear: The A5 is not a Part 23 certificated model, and as an LSA the testing that Icon does on spin resistance is purely voluntary and not validated by the FAA. If you believe what Icon is telling you, and I’m strongly persuaded by the video, then that’s your call. I just wish that Icon would say directly that what they are calling a spin resistant design is Icon’s determination and not the FAA’s. It’s an easy thing to explain and I’m baffled as to why they don’t just come right out and say it. It detracts nothing from the company’s impressive work.
In the video the A5 essentially does a fly-off against a Cessna 150, the classic training airplane and a great airplane (when properly outfitted and under proper supervision) in which to learn spins. The video is gorgeous, Icon’s explanation of what’s happening aerodynamically is crystal clear, and the results are startling. Check it out.
As far as the spin resistant claims are concerned: as I said, I’m strongly persuaded. The A5 appears in the video to mush instead of departing controlled flight. Icon says the rate of descent is 1,000 fpm, a survivable rate even if nothing else were done to arrest the descent.
This level of spin resistance, if it’s as good as it seems, might not be the holy grail of light aircraft design, but it’s a huge development. Loss of control at low altitude represents a big part of the fatal accident pie; creating a design that’s largely immune to loss of control under the most common flight scenarios would be a huge feather in Icon’s cap.
As I’ve told the folks at Icon, I can’t wait to fly the airplane.
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Impressive, but I can't help but wonder...this makes me think the A5 has ZERO rudder authority when near a stall. How else is there almost no yaw movement when they put in full rudder?
The way you design a spin resistant airplane is to limit control effectiveness to the point the wing won't reach the critical angle of attack. It was done this way in the 30's with the Aircoupe, the Stinson Voyager and others. The Piper Cherokee, a late 50's design and contemporary of the Cessna 150, is spin resistant for the same reasons. That's what they've done with this one too, look at the amount of rudder deflection, maybe 12 degrees. Will this eliminate stall spin accidents at low altitude in this airplane? I seriously doubt it. Roll this thing into a bank add full aft stick, top rudder and full power, that's the scenario for an approach to landing stall spin, not the generic spin entry they demonstrated here. I'm guessing the outcome, while perhaps not a fully developed spin, won't be so benign.
B
Sent from my iPad
They do not limit the control authority to make it spin resistant. This method of spin resistance is based upon the NASA work in the late 70's and early 80's where a notched leading edge cuffed airfoil is used to maintain flight control in stalled flight. Since an unbalanced moment is needed to create the spin this does not occur and any rolling moment can be easily controlled by the ailerons. I have flown airplanes so configured at NASA (with an emergency spin chute just in case) and they just mush with good aileron control.
Actually the Cirrus has such a notched leading edge. I am not sure, however, that it is spin resistant, but I suspect that it might be. So I am not sure why the company keeps saying they are the first ....
In any case, this configuration does not limit control authority, it is remarkably docile in separated flight, but with moderate sink rate. The trade-off is performance since the notched leading edge detracts a knot or two from top speed and adds a bit to the fuel consumption at each speed.
I do not share Goyer's concern about declaring whether the test procedure was performed by an FAA inspector vs. a company test pilot. In fact, in most FAA certification the tests are done by the company and documented and then the FAA reviews the paperwork and participates or observes a sampling of the tests. The criteria is clear enough and if the company says it satisfied the criteria who cares who conducted the test?
Dear Mr. Goyer
I can't be the only loyal Flying reader who hates those annoying, full-page pop up ads for vaccum cleaners every time I try to look at your website.
Doesn't Bonnier Corp make enough off ad sales?
Banners and thumbnails, fine. Giant, intrusive pop ups are in poor taste by contemporary web marketing standards.
Sorry for the thread hijack. I didn't know how else to make my opinion known.
Bart, you mention two points of concern that I'll try to address.
1) Spin resistance is achieved by limiting control authority.
Well, yes that's a way. There are two requisites for a spin:
a) A stall (no stall = no spin), AND
b) An asymmetric stall that causes a great loss of lift and a huge increase in drag in one of the wings (compared with the other), enough to overcome the control authority.
Without both a) and b) happening together, the spin never starts.
The Ercoupe used a). It was STALL resistant, a thing that exists in the FARs since a lot of years ago. While stall resistance ensures spin resistance (based on (a) ), spin resistance requirements were added at a much later time in the FARs (corresponding to the NASA tests mentioned by rocketSMS) and stall resistance is not a requisite for it, because it can be addressed avoiding b).
In this last case, If you don't apply the needed control inputs, the airplane might roll inverted, or yaw into a sideslip of 45°, but won't spin. Not that crashing inverted and into a 45° skid is much better than doing so in a spin, of course (the plane is spin resistant, not crash resistant). But the point is that the control inputs needed to prevent this from happening in the first place, and to recover from that if that happens, are the usual control inputs used in normal flight: Control roll with ailerons, control skid with rudder, control pitch with the elevator. You don't need a specific spin recovery that requires not to correct roll with ailerons, close the throttle, push down on the yoke to the stops, apply full anti-rotation rudder, and hold until the plane recovers (or something like that).
2) The spin scenario demonstrated in the video is too benign, and the plane will probably spin if in more aggressive flying.
Icon claims to have followed the FARs requirements for spin resistance (again, that's what Icon claims and the FAA has nothing to do with that). They claim to have tested the full spin entry matrix, as required by the FARs. That matrix includes full power / idle, full rudder left / right, full ailerons pro-ruder / anti-rudder, no flaps and full flaps, accelerated / not accelerated, climbing / descending, CG max forward / max aft, and all the combinations of all those. That's dozens, maybe hundreds of scenarios.
rockerSMS,
The Cirrus is not spin-resistant certified. In fact, the FAA accepted "fire the chute" as an acceptable requirement to an "aerodynamic" spin recovery procedure (and it is as such in the POH). As far as I know, no airplane has been ever certified as spin resistant, and the Icon wont be either because, as an SLA and not a part 23 plane, it will all end in something that the company claims and nobody certifies.
I could write a small essay on aircraft properties and configurations and dig out my book of aircraft design and aircraft structural calculations (puts the best of insomniacs to sleep) but flying consistantly safely is a mixture of self discipline, self criticism and fun. In that order. Keep to these simple rules which makes sure the prods in the arm from your instructor stay with you, which doubles your smile when taxi home proud of your flying and enjoyed it too.
Oh yeah. I would rather be spinning the Cessna as long as it is an aerobat, which I can't see from the grainy movie, being used to the checkered paint job and windows in the roof of the "bats" I have flown and been in. Then again thats some time ago.
May 30, 2012 - ICON Aircraft announced earlier this year that it successfully completed spin resistance testing of its A5 amphibious light-sport aircraft to FAA Part 23 standards.
http://airsoc.com/articles/view/id/4fc6c85fc6f8faa003000015/icon-highlig...
Gabriel, you are right of course about the effect of the cuffed leading edge, it works exactly the same as the fixed slots on the Stinson, Swift and several other airplanes of that era. The Stinson will not stall conventionally either in the landing configuration because with one notch of flaps, plaqarded in the airplane for landing and takeoff, up elevator travel is limited. The Stinson L 5 used a similar system and so did the Luscombe Sedan if memory serves. There are no computer aided flyby wire devices on this airplane so the only means of preventing a stall is to limit control effectiveness. To a point this will work, but it won't stop stall/spin accidents and I'm confident that will be demonstrated when these airplanes are being used by pilots of below average skill, which is the target market of LSA airplanes. Regarding the Cirrus, how's that parachute thing working out for you as a means of preventing accidents caused by lack of skill and judgement?
Is there a trade-off in maximum crosswind landing capability due to the apparent reduced rudder effectiveness? Comparing the Icon to the Cessna, it seems like you could get the Cessna to sideslip more than the Icon.
Well ya know, of course, that the Ercoupe, a sixty plus year old plane, was the first, and until now, only plane to be designated by the FAA to be spin proof. I own one and it responds EXACTLY like the Icon in a stall.
Of course they do add that the Icon is the only “standard configuration” aircraft to be so disignated … and since the Ercoupe has a split tail I guess they are technically right.
Nice plane the Icon and someday I’ll trade the Ercoupe in for one.
Steve
it is simple aerodynamics method to avoid stall-spin with the use of drooped leading edge in front of ailerons. Another more imposing leading edge device is the full span slotted leading edge, because this also improves lift coefficient and critical angle of attack.But this aerodynamics wing solution is one of the sufficient solutions for good stall-spin recovery characteristics.Look at the cessna spin in the video that rudder is fully deflected this caused the continuous spin during the stall. If the A5 rudder deflected during the stall it would have spinned. Otherwise the cessna's wing has washout from the root to tip and this is also causes good stall-spin recovery.
All of ya'll need to go back and watch the video again. There's been quite an erudite discussion here but the simple fact is: if you watch the A5 closely at the moment of the "stall" you will see that they simply limited the elevator authority. watch it closely. My first question after seeing that was; is there enough elevator authority to overcome an inadvertent aft cg landing.
I am impressed with this implementation of the NASA and related designs but the claim to "first ever" is exaggerated in some ways.
I am most familiar with the stall control characteristics on the C400 and DA40. On the Da40, many pilots attempting to enter a spin have given up in failure. I understand that the aircraft has been spun in test situations by manipulating the load and balance but it is difficult and recovery involves nothing other than letting go of the controls. I am very familiar with the C400 and DA40's control in a deep stall. Aileron control is mushy in the DA40 mushy (almost crisp in the C400) but definite and turns are easily accomplished. There is no "break" only a mushy settling descent. I have entered this full stall situation on many occasions. In the DA40, with one SOB and 30 gallons of fuel, the descent rate is less than 1,000 FPM.
All good stuff. I only object when one brand tries to claim exclusivity when many manufacturers are taking advantage of new, safer designs.
I'm curious - after reading a majority of these comments - as to what exactly spawned the need for rebuke or slander against the achievements of the Icon group?
The plane is being designed to be a safer aircraft for all of us. Icon has chosen to accomplish this, no-less-than-grand, feat by following the specifications laid out in the FAA Part 23 standards (as stated by #johnysmith and explained by #Gabriel). This success has never been achieved before, hence the statement, "first ever", which would make it an appropriate statement.
No one claimed in the video, or the article, that flying ANY aircraft does not require discipline, skill, and common sense. So since it doesn't correct a moron pilot, it's a scrapped idea? Please tell me how that works? OH wait, I see, because if you really-really-really-really-really tried to get the plane to spin, it would.... Thank you Sherlock... The spin resistance that they created is for...wait for it... NORMAL FLYING CONDITIONS!
Some advice to possibly assist some of you with a brighter future:
When someone in our field reaches out, creates something to further advance aviation, making aircraft of safer design in more of our "normal" flying conditions - instead of pissing and moaning about what you think you know... don't! Just because they're marketing this achievement and others don't, IS NOT their foul!
I, for one, am very excited about the advancements that the Icon team has made, and believe that this design will save lives, instead of take them. Which I cannot say for many of the "old dog" ways of doing things. Maybe it's time to give up the guff, and get on board.
Who gives a flying rat fart if they want to boast about their achievements. Good for them!! They should ABSOLUTELY celebrate successes of this nature and claim all the damn credit!!! At least they're not sheep following the herd - again, something I cannot say for the others.
You support people that have love for aviation, and making it better. You don't belittle their achievements, and point your nose to the sky. You are not smarter than they are. You are not better than they are. If more of you would get that attitude out of your heads, we'd all be a lot better off.
There's my 2 cents...
@ Archammer - I don't detect the same degree of venom in the comments here that you have. I'm hearing healthy scepticism rather than unreasonable cynicism. "Slander"? Cummon. I'd call it a reasonable examination of Icon's public utterances by a bunch of interested, knowledgeable aviation-types. I still want one and I feel like I've learned something by reading the comments.
This means little to me. When I used to teach spins to instructor candidates in C172s, I would often have the CG so far forward that airplane couldn't spin with power off, full back elevator and the stall horn blaring. Very much like the video above.
What I want to see is how this A5 handles power-on stalls. That's the real test. Show me that video. Anything less is not enough.
Well, there are examples of spin-proof aircraft. The ASK-21 glider needs a spin-kit to be able to spin. The recepit for spin-resistant aircraft is not particularly difficult - docile stall characteristics (which usuallty means ample washout) and CG far in the front.
Of course, this comes at the cost of reduced efficiency. CG far ahead means that more downforce from the stabilizer is necessary.
