Anti-ice for experimental.

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Alessandre

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I was thinking of viable ways of de-icing for experimental aircraft that excludes the complex and expensive de-icing boots and the anti-icing liquid that cirrus uses (very complex for experimental), leaving only two forms of heat that would be electric and engine heat, in this case direct electric heating from the leading edges using some type of adhesive with electrical resistance or from the hot air system itself for the cabin, a bleed that passes through the leading edges to be eliminated by the wing tips (considering aluminum wing), I don't know if the heated air by the exhaust would generate enough heat for that, I would like to know if something like that has already been tested?
 

Voidhawk9

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Some turbines use bleed-air for this. These are bigger aircraft with a lot of heat energy available. For a small piston-engine machine, I'd say you'd be hard pressed to get enough heat. Maybe if you were liquid cooled and pushed lines of coolant through leading edges, but that would get heavy and complex fast.

What sort of aircraft are you considering this for?
 

TFF

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It’s usually not enough heat to run piston exhaust through the wing. It it is very hot then cools too fast and makes ice worse. If you needed deice, I would make the oozing wing like Cirrus or Mooney.
 

arj1

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@Alessandre, search for (now dead) company called Thermawing - they had a fully electrical solution for GA a/c. But it was for slightly bigger planes (bigger Cirrus, Cessna 400 etc).
 

dave wolfe

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My recollection having been in the bleed air business many moons ago is that the heated leading edges need to evaporate the oncoming ice & snow. This takes a lot of heat. Dont bother trying on a recip. Insufficient heat causes runback and then ice formation behind the heated area which can grow in shapes that can cause a crash
 

Hephaestus

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I don't know about anyone else... But I'm not sure the FAA would let you "try" experimental FIKI. Nor is it something I personally would want to screw around with.

You could absolutely throw heat tape on the leading edges - but calculate the BTU requirement at cruise speed and you'll probably realize you need an expensive and heavy Genset to get even close to that much power.
 

dave wolfe

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If I had a need to fly in the ice once or twice a yr, it'd be in a certified pistton single at a minimum. Regularly? Certified multi recip or turbine single.
 

wsimpso1

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The process of icing is usually one of supercooled droplets striking the skin and freezing instantly. So you have to supply enough heat per unit time to take that ice that is attaching to the surfaces up to freezing, then through the latent heat of fusion, and then enough hotter to prevent the water from refreezing before it runs off the trailing edges.

The amount of energy is pretty high. I would propose that you calculate the energy needed to do this is with outside air at -20C and whatever the expected ice accretion rates are. Figure out what the ice accretion rate would be in say lbs or kg per second, then calculate the heat required to raise the ice from -20 C to 0 C, then go through the latent heat of fusion, then raise it a few degrees above the freezing point. This heat flux plus the flux to raise the boundary layer from ambient to a couple degrees above freezing is your estimate of thermal power required at the outside of the leading edges and inlets. Then whatever temperature you arrive at for the outside skin temp to warm these droplets must be increased some for the inside - stainless steel has significantly lower thermal conductivity than aluminum. You might need a lot of hot flow.

Turbines engines use bleed air for this, and when anti-ice is on, fuel efficiency is reduced significantly because the air is bled from the compressors, and that energy comes from one of the turbine stages. While it may be minor for a turbine engine, our little engines may not have enough waste heat to do this reliably.

One thing you might check out is a turbocharger expressly operated to provide heated air for this purpose. Again, the issue becomes one of can you get enough air that is hot enough, but if you can, it comes almost for free, and you could use cooling exhaust air as the feed to this as a preheater.

All of the basic homework should be done to see if it can work before building it, or a lot of effort and money might just might be wasted.

Billski
 
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Turd Ferguson

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I don't know about anyone else... But I'm not sure the FAA would let you "try" experimental FIKI. Nor is it something I personally would want to screw around with.
There are no prohibitions against operating a homebuilt in icing conditions. Also not aware of any limitations for installing A/I or de-ice equipment on homebuilts, regardless of the source. Agree that your personal observation is probably correct: The self-regulating aspect of doing something like that is adequate; IOW's at present nobody is that stupid.

A heating solution is completely impractical for lightplanes. Dispersing FPD fluid would be the only viable option worth pursuing, minus the propeller.
 

TFF

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The real question is why the need. Amateur flying can usually wait a day or two for ones skin sake. For a world record or something is a different answer.
 

Marc Zeitlin

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There are no prohibitions against operating a homebuilt in icing conditions.
While this is technically correct, there is always 14 CFR Part 91.13

These three articles discuss the issue, mostly with respect to TC'd aircraft:


but the same arguments apply - folks have been violated purely on 91.13 grounds for flights into not only "known" icing, but conditions in which icing MAY have been expected or just possible.

So, yeah - there's no explicit rule preventing an E-AB aircraft from flying in conditions in which icing may occur, but it's clear that the FAA believes that without approved FIKI, 91.13 is the catchall that they can use (and have used) to violate a pilot (assuming they're still alive).

Given the complexity in getting FIKI approval, well, it's just not going to happen on E-AB aircraft - no one's going to do it for a one-off. So that route is effectively shut off.
 

Turd Ferguson

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While this is technically correct, there is always 14 CFR Part 91.13
Ya, a stand alone 91.13 infraction is exceedingly rare and I would challenge anyone to find such an enforcement action regarding flight in icing. Anyone that flies IFR will encounter structural icing at some point. The number of airplanes equipped with some kind of ice protection equipment but not approved for flight in icing is evidence of that. When law makes reference to the nebulous "reasonable person" that's the kind of plane they own. 😁
 
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jedi

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If the experimental is Roadable you can operate in or on known ice.

Who wants to fly light GA aircraft into known ice. Even birds don’t do that. Flying in iceing conditions? That is a whole different issue.

It is probably better to fight this issue on paper, in the reg’s, than in the shop.

What is “known ice” is a good discussion point.

Known ice is something to avoid in a Boeing. It can and has taken down airliners.

There is wind and then there are tornados and hurricanes. You need to define what limitations you want to put on “known ice”.
 

BJC

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If the experimental is Roadable you can operate in or on known ice.
Kevlar chains for the tires (to drive on ice) are lighter than the typical steel chains. Harder to find, and cost more, though.


BJC
 

Alessandre

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This was a subject I was totally unfamiliar with, I came from a country where ice only exists at the altitudes of commercial flights, so I have never heard about worrying about ice when making a cross country flight in a GA reciprocating aircraft, only the conditions for formation of storm and visibility were what I worried about, but now living in Michigan the freezing has become a matter of concern as it makes the operation dangerous in the winter months, unlike where I came from where I would rather fly in the winter months than in the summer because the air was free from turbulence.
But based in comments I can see why cirrus SR22 uses liquid instead of heat for dealing with ice or king air uses boots. Living and learning :)
 

Heliano

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Flying into icing conditions takes more than wing ice protection. If it is a piston engine: you have to make sure the cooling air inlet does not get blocked by ice; propellers without ice protection go unbalanced and produce a lot of vibration when ice accumulates on them; windshield needs defrost or you would be in big trouble if the ice remains on it by the time of landing; needless to say that pitot and static port heating must be powerful enough to do away with any ice/frost accumulation; horizontal tail ice protection may be necessary for certain CG conditions or you run the risk of losing longitudinal control.
There are two wing solutions: deice and antiice. Deice are basically boots, which require little energy to inflate them every, say, 40 seconds. Normally inboard and outboard sections are alternatively inflated in a symmetrical way. Antiice is heating. It requires a huge amount of heated air. To illustrate this: turboprops in general do NOT have enough bleed air to heat the whole wing leading edge. Some jets do not have enough air either (examples: Gulfstream 200, Cirrus Jet). Turbofans have enough bleed air hot enough to eliminate ice (high stage bleed air from most turbofans is in the vicinity of 600F). The ice flows through a pipe with many tiny holes. This pipe is called piccolo tube.
Windshield, engine inlet, propeller can have electric heating. But can your alternator/generator deliver that additional load? You have to do a electrical load assessment.
Now: the worst flight levels as far as icing is concerned are around freezing temperatures with freezing rain/drizzle. It is deadly. There are some types of icing against which NO aircraft is protected: icing with SLD (Supercooled Large Droplets).
Icing is no simple matter. If you can do without it, it is much safer.
 

jedi

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Assendree,

Check your personal messages.

The above post #15 about your experience explains a lot. You need some good flight related discussion.

My worst ice incounter was in a Cherokee 140 in CAVU conditions. I had maybe 800 pounds of ice when I landed. I have been in similar conditions in Michigan but at above freezing temperatures.
 

Turd Ferguson

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but now living in Michigan the freezing has become a matter of concern
I live in MI as well and people don't park their planes all winter long. Just like convective weather, you'll need the proper training so you can recognize and escape hazards if any inadvertent encounter occurs.
You can also take a hint from Cirrus folks and others, many planes have various ice protection systems installed but they are NOT approved for flight in icing conditions.
 

jedi

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The best anti ice for the typical EAB is a big round leading edge radius. The smaller the radius the quicker it will pick up ice.

If you have a laminar flow wing, as in a Cirrus, you do not want any ice.
 
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