Know Ice vs inadvertant, vs none


Happy New Year.

How about you guys telling me what you think about ice equipment.

I am familiar with TKS systems, and believe that an inadvertant TKS system has only marginal value. I would only see using it in an emergency, but because it is not really reliable, I would not allow it to change my go/ no go one bit. To me, it’s not worth the cash or weight.

OTOH, a known ice version would allow me to fly into conditions where I suspect light ice may become an issue (flying a light plane into “known ice” is really something I would balk at in spite of equipment). If my flying increases, as it looks it might, I may trade up to a plane with Known Ice TKS if I find fear of icing giving me delays.

Lastly, I have never used boots, and my only experience with them is that they are costly whether used or not because they need replacement with time. Any experience on costs with any of the systems would be appreciated. Thanks.



Not sure why you see a big reliability difference between a known ice and not known ice TKS system. The TKS itself is the same, though other systems such as heated fuel vents may be different. The main thing to know about the TKS system is that you only can fly in icing conditions for that amount of time for which you have fluid. For example, a Cirrus has a 30 minute supply. I find TKS to be very valuable in that it gives you another option if you encounter ice and it does change the available flight profile.


The Mooney TKS is certified for ‘known icing’.




The difference between the TKS “known ice” and “inadvertant ice” is based on reliability and amount of fluid. I suspect there is a difference in the level of testing required as well. In fact, I think its the certification costs that make the known ice so much more expensive because the hardware difference doesn’t look all that expensive at all.

Glycol is tough on pumps, like soap is. I am not kidding when I tell you that the reliability of a deice fluid pump is not all that better than than a soap dispenser in a public bathroom (the old refillable kind, not the new cartridge kind).

“Known Ice” installations have no few than two pumps (redundant). Inadvertant usually have one.

Then, there is the amount fluid. Known Ice systems have a LOT more. IIRC, there is about a 5 times difference.

Based on geography, mission, and personal decision making, the inadvertant ones have almost no value to me. If I lived in an area where really thin layers often pop up during certain times of the year and day, I might think differently.


You got me curious, so I called TKS. The only difference between the known ice and the not known ice system is that the known ice system has 2 pumps. I asked them if they could install a second pump on the not known ice and the answer was probably yes, but he knew of zero pump failures so didn’t see that it was worthwhile. The amount of fluid is the same on both systems. The known ice system actually costs less than the ‘not’ system when it is factory installed as the certification costs are part of the plane certification.


Checking the tank sizes for different aircraft suggests otherwise on the amount of fluid. As for failures, I simply don’t believe it. At any rate, are there any instances of a choice of systems being available on any given airframe?


The fluid amounts across different planes is based on the space available for the fluid storage tank. For example, if you get a known ice system on a Mooney or a not known ice system installed as a Mooney after-market system (it is available either way), it has exactly the same tank. If you are skeptical about the pump failure, you could always elect to have a second pump installed. I spoke to Cirrus (a single pump system) and they said that the only cases of pump failure on their aircraft were when the pilot ran the pump for a long time after the fluid was gone. This includes both planes that they service under their 3 year warranty program as well as the general fleet.


Do you know if there is a minimum endurance for the system to be known ice? That Cirrus tank is too small IMO. I am still not comfortable with a single pump, and also not excited about losing the legal coverage of the Known Ice cert. Perhaps I will check with the Mooney group about pump failures. Cirrus hasn’t had a lot of them out there very long.

I doubt anyone ever gets busted for flying into known ice unless they have an accident, but if you do have an accident, you don’t want to have to fight with the insurance company over the claim (or the FAA over YOUR Cert.)


Not that I know of, but call the TKS folks, they’re very helpful.

I have heard second hand (and am only the messenger here) that a certain well known aircraft company tells people that a forecast of ice does not legally constitute “known ice.” Further, they have said that only a pirep constitutes known ice and only for that specific place. I agree with you that you want to understand the legalities before you put anything at risk, but if there is any truth to the statements above the matter would be more about pilot judgment of safety than about the legal risk.

Let me be clear here that I’m not a lawyer, not offering legal advice and not suggesting that you test any legal limits - just passing along some information that you might want to explore.


This is an important subject to me. I live in the frigid Pacific Northwest and will be flying over The Rocks into Montana year ‘round with an MEA of 13000’.

I’m close to ordering a Mooney Acclaim with TKS. Even with TKS I know that I’ll be rescheduling many trips due to ice. I want a new plane for several reasons and I didn’t even consider either the Cirrus or Columbia because of the lack of known ice “certificataion”. While I understand that some people think little of the “certification” process and the legalities associated with it, I happen to believe it is important.

I’m just getting back into flying after many years of absence and it’s interesting to me that the FAA now seems to be ratcheting up their concern over icing – that comes as no suprise. However, as in many things, it’s not the government that one needs to worry about when things go amiss … it’s the insurance company.



I see what you are saying, and am right with you. I have always found that it’s a shame that safety regulations and real safety aren’t as well aligned as I would like.

Forecasts are fine enough to scare me off. Keeping the FAA out of my life is something also to be avoided. I just don’t live under the illusion any longer that acting safely will keep the FAA away. OTOH, I am quite sure that a little mistake can be turned into a federal case.

The FAA has become like the IRS. The Congress has let them take over all three functions of government in order to absolve its members of blame, responsibility, and work. I have met both good and bad FAA guys, and seen the inside politics at work.

If you get tangled up with them, hire counsel, and prepare your checkbook.


Not to put too fine a point on this, but the primary issue is what you, as pilot in command, consider safe for flight. You wouldn’t want to abdicate that authority to anyone else. If you do that correctly, there will be no issues with the FAA or insurance. If not, there may be people second guessing your decision. No matter what system you choose, there can be icing conditions more severe than your aircraft can handle.

If you haven’t already, I suggest that you view the FAA video on icing posted on their web site. There are examples they cite of large commercial turbine aircraft that get into icing conditions more severe than they can handle, and they have speed/friction in addition to hot bleed air deicing systems. The other thing that would be well worth your while is to fly with someone in icing conditions who has the experience and equipment to teach you safely.


Rumor has it that Cirrus is working on a “new” plane, the SR24 which will have FIKI and 350 horsepower normally aspirated, 5 seats, and the Garmin panel as an option.


I get your point CA. What I am saying is that I judge what is safe for myself, and it is usually far stricter than regs.

Let me sharpen another good point.

I ALSO judge what will keep me away from regulatory action - SPECIFICALLY. In other words, just because it’s safe, doesn’t mean it won’t get you busted by some poor slob unfortunate to work in a FSDO where he is judged by creation of documents rather than by keeping us all safe.

Case in point: I recently flew all the way around the Crawford TFR when I could have gone through the extended section. I had a valid plan filed, and was in contact with ATC, but I requested a path a long way out of my way just to avoid the whole matter.

Another: During flight training, I took off solo in the rain. This created panic at the school, and generated a call to my instructor who - knowing me - told them all to relax. He knew I wasn’t up to trouble. I took off because the rain was only over the first 200 feet of runway and the north end of the field. The rest of the field was under blue skies and the lonely rain cloud was moving north. I had two other fields to choose from if it reversed direction, but it was only a mile in diameter. We had a good laugh after that, but the kid instructors still persisted in calling me “Rain Man”. It was legal for me to take off because of excellent visibility (we had a smoke stack visible 6 miles south of the school), yet an overzealous FAA inspector could have had a field day with that.

Third: This one is not aviation, but helps make my point. I got a ticket for going 35 in a 25 that was a school zone. A grandstanding mayor had recently tripled lots of fines to bolster his support while quietly pressuring ticket quotas on to the police to raise money. The cop that gave me the ticket did so by simply waving me over and writing me up. He used no radar gun, and I was not yet in the school zone when he started waving me over. When I left, I went around the block and observed him doing this to 2 more cars. Then I found out he put the wrong day on the ticket. I paid a lawyer to get the ticket dismissed, and later learned about the quotas and bad morale from another officer who apologized and also pointed out that the guy had likely taken the day off by writing a bunch of tickets with the wrong dates. This officers behavior was overboard, but I can understand how the environment had helped him rationalize it.

It’s like buying insurance. You don’t buy the insurance to keep you safe, you buy the insurance to avoid bad consequences. Flying by the reg’s is like buying insurance to me. I don’t believe it keeps me safe, just out of trouble.

THEREFORE - Known Ice would have a value that inadvertant ice would not. Even if inadvertant kept you safe, it wouldn’t keep away the FAA.


So you raise an interesting question (and I have no idea what the answer is). How many times has the FAA taken action against a pilot when they landed safely after flying through icing conditions in a plane not certified for known icing? I will say that I don’t think that the FAA is anything like the local police department in a small town.

You are also touching on one of my favorite aviation topics: where is the border between acceptable and unacceptable risk in flying. For example, it is an unacceptable risk for you to fly through a legal TFR corridor while in contact with ATC on a valid flight plan, acceptable risk to fly in known icing conditions in a certified single engine airplane and unacceptable risk to fly the same conditions in a plane with the same equipment (but uncertified). Many pilots might fly the TFR corridor and not be willing to fly icing conditions in any single engine airplane, certified or not. I’m not debating who is right or wrong here, but am constantly amazed how subjective the risk measures are in flying.


I am fascinated with the whole risk assessment thing as well. Especially how to teach it to pilots and youngsters. One thing I have noticed is that too many pilots think that if its legal, it must be safe. Also, that if its safe, it must be legal.

As for the icing, I don’t know how they enforce that.

However, I have been the subject of unwarranted FAA action, at least my plane was. It was grounded for 3 days without proper authority because a FSDO employee noticed a problem with the plane that he thought was unacceptable. A SB addressed the issue, and stated that it was not a saftey concern, but the operator of the flight school was not going to risk his business to rent out my plane. The FSDO rep had ZERO authority to ground my plane (especially without proper procedures). Why did it happen? Because the FSDO had been taken over by a new leader who wanted to make his mark. While they were screwing around creating paper work for everyone, people were dying due to poorly maintained aircraft.

Lastly, that was no small town I was talking about, it was Houston. The ticket quota problem has been raging across the country, and in Canada where the Calgary police chief very publicly told his mayor it wouldn’t happen under his watch. Gotta love that guy :smiley:


Here is a good article about how pilots should consider safety, and THEN consider regulation:

Especially the last paragraph. I see I am not the only one who is afraid these days.


N60NL - if you have the scratch to order a new TKS Bravo, you likely also have the resources to afford a PC12 or a Meridian JetProp - whether you have the experience and insurability is another Q. However, a turbo prop may be your best choice since all them are certified into ice. There are also several twins in the $150k range that are ice certified . . .


Not sure how you come to that conclusion. A PC12 is multiples of the Mooney price as well as multiples of it’s operating and maintenance costs. A Meridian isn’t quite as expensive as a PC12, but well more in both acquisition, operting and maintenance than a Mooney.