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Visible Moisture

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gear_guy

Well-known member
Joined
Jun 16, 2004
Posts
438
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.
 
Oh yeah, you probably already know this but ambient temps drop around the inlet (due to camber - air acceleration) as the speed of the air increases and creates a drop in temperature.
 
Oh yeah, you probably already know this but ambient temps drop around the inlet (due to camber - air acceleration) as the speed of the air increases and creates a drop in temperature.
I agree with this too, but there has to be a limit. I am sure you don't shoot approaches in VMC with 10sm visibility with the anti-ice on. Or do you?
 
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.

What was the humidity?
 
Last edited:
If by that you mean temp/dewpoint spread, it was +5C/-1C

I would have had anti-icing "on" throughout approach and landing.

The FAA now deems any "area" that you are flying in that has high relative humidity is "known icing conditions."

You're right about not being able to fly with a C-172, any general aviation aircraft without anti-ice protection couldn't fly.
 

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