Visible Moisture

[Fly91]

That interpretation was rescinded back in late September.

They really shouldn't have, but they can't stop aviation growth. Economics over safety every time, thats the American way and the FAA way.

Thats why I said I make my own rules and over the years I've flown with dozens of pilots, world-wide, part 91 135 and 121, who do it all a little differently. No matter what manufacturers say about visible moisture or known icing, no matter what the FAA says via regulation or AIM recommendations, or what any other pilot says.......there's just to much of a wide range of situations where icing can happen. It happens even when it IS NOT supposed to happen.

So when in doubt, use it. I use it anytime the temp is 10c or less with vis less than 6 and any haze or clouds, thats it. Even when flying in the clear with that temp and vis, its good to just hit the switch. Its free.

 

[FastJP4]

FWIW - our good book states that icing conditions exist in temps of +10 to -40 with visible moisture, to include clouds, rain, snow, sleet, ice crystals, fog and visibilites less than 1sm.

Under the conditions you described (+5C, 3sm, ceiling 3000') I would have the heats on.

I don't have the FAA definition of visible moisture, but I think you can reasonably expect that if the visibility is 3sm - there's a fair amount of moisture suspended in the air in whatever form. Couple that with our temperature definition as it relates to icing - and it would be pretty clear to have the heats on.

Figuring the temp/dew pt. spread or thinking about special VFR at 1sm is too much damn work. Turn the heats on and be done with it - while erring on the side of safety.

 

[TheInsider]

Ok. Here's the question. What is your definition of visible moisture? I just got corrected in the sim because I did not use engine anti-ice.

Conditions were: Visibility of 3sm, temp of +5C, ceiling of about 3000', no precipitation reported. I was shooting a circling approach and had good visual on the runway.


Manufacturer recomendations are to use cowl anti-ice when temps are <+8C and in visible moisture.

I told them I thought the definition of visible moisture was <1sm visibility. Am I wrong? And do you know where to get the FAA or AIM definition?

Under their theory I could not be in a C-172 and fly that day even though it was VFR.

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FAA definition:

VISIBLE MOISTURE – Visible moisture is the presence of any precipitation, or the visibility in fog is less than one mile.

See AC 120-60B and REEVALUATION OF DEICING/ANTI-ICING PROGRAMS N 8000.308

 

[Fly91]

FWIW - our good book states that icing conditions exist in temps of +10 to -40 with visible moisture, to include clouds, rain, snow, sleet, ice crystals, fog and visibilites less than 1sm.

Under the conditions you described (+5C, 3sm, ceiling 3000') I would have the heats on.

I don't have the FAA definition of visible moisture, but I think you can reasonably expect that if the visibility is 3sm - there's a fair amount of moisture suspended in the air in whatever form. Couple that with our temperature definition as it relates to icing - and it would be pretty clear to have the heats on.

Figuring the temp/dew pt. spread or thinking about special VFR at 1sm is too much damn work. Turn the heats on and be done with it - while erring on the side of safety.

Simple as that...just do it.

 

[Fly91]

FAA definition:

VISIBLE MOISTURE – Visible moisture is the presence of any precipitation, or the visibility in fog is less than one mile.

See AC 120-60B and REEVALUATION OF DEICING/ANTI-ICING PROGRAMS N 8000.308

That may be the FAA's definition, but if pilots just used that as a guideline, there would be an increase in icing related accidents. Icing in clear air with better than 1sm visibility happens all the time.

 

[BoilerUP]

That may be the FAA's definition, but if pilots just used that as a guideline, there would be an increase in icing related accidents.

...I seriously doubt that.

If you operate the EAI in a fashion more conservative than the manufacturer and FAA dictates more power to ya...but that doesn't mean someone that uses those limitations as their EAI guideline isn't operating their aircraft 100% safely.

 

[Fly91]

...I seriously doubt that.

If you operate the EAI in a fashion more conservative than the manufacturer and FAA dictates more power to ya...but that doesn't mean someone that uses those limitations as their EAI guideline isn't operating their aircraft 100% safely.

Maybe, and thats a big maybe on the 100% safety question.

But whats for sure is, that "someone" does not fully understand icing and they certainly don't realize that icing can happen at times when there is NO WAY it should happen.

If any pilot thinks they must be in "precip" of in fog with vis less than a mile, to have icing, their days are numbered in aviation. And if/when that day comes up, hopefully they're flying single pilot with no passengers. I've flown with enough different pilots through the years, hundreds of different pilots, they all use anti-ice systems in pure IMC and in the clear with low vis, near freezing temps, smart decisions on both counts.

Flying on the edge is hardly 100% safe operating practices. There's no such thing as 100% safe anyway.

 

[gear_guy]

Maybe, and thats a big maybe on the 100% safety question.

But whats for sure is, that "someone" does not fully understand icing and they certainly don't realize that icing can happen at times when there is NO WAY it should happen.

If any pilot thinks they must be in "precip" of in fog with vis less than a mile, to have icing, their days are numbered in aviation. And if/when that day comes up, hopefully they're flying single pilot with no passengers. I've flown with enough different pilots through the years, hundreds of different pilots, they all use anti-ice systems in pure IMC and in the clear with low vis, near freezing temps, smart decisions on both counts.

Flying on the edge is hardly 100% safe operating practices. There's no such thing as 100% safe anyway.

Ok, I think I understand now. Disregard the manufacturer reccomendations and make my own rules. Got it!

Ok just kidding. But my real question was not whether it was a conservative choice, but rather was it operating out of the reccomendations of the manufacturer. I think I have my answer. Yes it is conservative and would'nt hurt, but it was not required per FAA or manufacturer.

 

[svcta]

I have to side with the folks here that operate exactly as the book gives guidance. My understanding of Icing Conditions are consistent with what has been posted here regarding the Fog with Vis less than one mile (the jets that I have flown all share that definition in the AFMs).

I think it's folly to call us "unsafe" or to claim our days are numbered because we know and follow the operating instructions that came in the box. I occurs to me that the "fog with vis. less than one mile" exists only to cover the amount of humidity present. Other than that what possible reason would we be concerned with the Vis? If it's raining or snowing you might as well be able to see 1000 miles; you would still run the A/I. The vis is a measure of just how much moisture there is when it's not actively precipitating.

The original poster is not looking for our opinions, however, but a hard-and-fast definition of "icing conditions". It's seems as if we have our answer.

Visible moisture in the form of precipitation or fog with visibilities less than one mile. The temperature range seems to vary a bit from manufacturer to manufacturer. Consult your manuals in any case. My opinion is that if you operate by them you'll be just fine.

Beyond this, you are making your own rules. I flew with a guy once who pissed and moaned about people who didn't fly by the company profile but then he would operate completely outside of the company climb profiles because he thought it was more conservative. He didn't like it when I pointed out that it was still a deviation from the company profile. I digress........

 

[avbug]

That may be the FAA's definition, but if pilots just used that as a guideline, there would be an increase in icing related accidents. Icing in clear air with better than 1sm visibility happens all the time.

This on the basis of what, then?

Icing in clear air happens all the time? No.

Icing in the presence of large supercooled water droplets happens all the time? Yes. However, large, supercooled water droplets aren't found in clear air. They're found in condensation, and in visible moisture.

Do we know the cause of the reduced visibility in the case in question? Reduced visibility of three miles in smoke...causes icing?

You can factually state that an increase in "accidents" will occur based on not using engine anti-ice when operating in accordance with the manufacturer guidelines and intructions? Whereas the manufacturer (and the regulatory agencies that over see the manufacturer) operate on the basis of extensive experimentation and research, and more than a significant database, what's the platform for your own research that dictates otherwise?

If any pilot thinks they must be in "precip" of in fog with vis less than a mile, to have icing, their days are numbered in aviation. And if/when that day comes up, hopefully they're flying single pilot with no passengers. I've flown with enough different pilots through the years, hundreds of different pilots, they all use anti-ice systems in pure IMC and in the clear with low vis, near freezing temps, smart decisions on both counts.

We're discussing a circling approach in three miles visibility with a temperature above freezing.

We're now to believe that the basis for making up your own policies and rules (as well as apparently statistics) is that you've flown with "hundreds of different pilots." Setting aside that your own obvious lack of experience from your language and statements tends to devalue your baseless assertions, your basis for making these statements is what you've seen others do...not what you do, and not what you do based on acceptable or approved data. Enlightening.

Flying on the edge is hardly 100% safe operating practices. There's no such thing as 100% safe anyway.

Perhaps you should get out of aviation then. Even the practical test standards require that you complete any maneuver with the outcome never in doubt. If you have doubt, and believe that no operation can be made safely, then it would appear you're the one placing yourself and your alleged passengers at risk.

You really believe that flying a circling approach in 3 miles visibility is "flying on the edge?" I have to wonder if you've ever seen the "edge." I've spent a great deal of my career operating right about where the edge is, and on many sides of the "edge," and I can tell you that flying a circling approach in 3 mile visibility isn't it.

Our AOM uses 10 degrees C Total Air Temperature as the temperature base for use of anti-ice in flight, be it nacelle anti-ice or wing anti-ice. Out TAT probe isn't sampling only ambient temperature, but ram air temperature rise, too. Icing conditions are 10 deg C TAT with visibible moisture of any kind: clouds, fog with visibility of one mile or less, snow, rain, sleet, or ice crystals.

I too fly with hundreds of pilots, right here, and every one uses the aircraft operating manual as the guidance by which anti-ice is applied. As do I. Perhaps you believe that my time in aviation will be short, as a result...you've not provided any rational basis for that statement, but you can believe whatever you want. The airplane has been operated for many years, a number of decades now, and hundreds of thousands of flight hours, on this basis...and will continue to be operatedon this basis...whether you agree or not.