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  #1  
Old 05-22-2022, 05:57 PM
ChiefPilot's Avatar
ChiefPilot ChiefPilot is offline
 
Join Date: Jan 2005
Location: Twin Cities, MN
Posts: 1,588
Default Cloud Residue - Beware!

Even though it's mid May, there might still be some "cloud residue" waiting for the unsuspecting. Pireps reported negative ice. Even though it wasn't forcast, the conditions were certainly present and when given the descent, I considered my options before starting down. In this case, it was of only minor concern since the cloud layer was verified to be less than two thousand feet thick and I'd be in a descent the entire way down. Once out, there was over 7000 feet of warmer air between me and the ground. Still, I picked up this much cloud residue in about two minutes coming down at about 1000fpm and 150kts:



Remember, flying in air temperatures of even a few degrees *above* freezing can result in the accumulation of airframe icing. Before penetrating any visible moisture when the OAT is less than 10C, I check the following:

1) What are my options? I.e. can I stay out of the clouds longer, can I find some clear airspace, how thick is the layer, what is the temperature below/where is the freezing layer, and so on.
2) Pitot heat is anti-ice, meaning it's designed to prevent the formation of frozen contaminants. Mine comes on prior to entering visible moisture any time the OAT is less than 10C.
3) Stay fast. I have test data for my aircraft that shows that 3/8" of rime ice increased the stall speed by 3 knots. But that was only really valid for that particular day, since ice can form in numerous different shapes and have associated effects. What I really learned from re-running the test card after picking up the ice during an IFR descent was that a tailplane stall was a definite possibility. If you have contamination on the wing, choose a long runway, land fast, and avoid the use of flaps if possible.

Above all, avoid it if you can. The work airplane has bleed air anti-ice for the wings and tail, and I've been in conditions there where the unprotected surfaces had a measured six inches of ice accumulation in the time it takes to do an approach (i.e. about 15 minutes). Days like that are much better spent hangar flying :-)
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  #2  
Old 05-22-2022, 07:15 PM
David Z David Z is offline
 
Join Date: Aug 2010
Location: Thunder Bay Ontario
Posts: 904
Default

Been flying the work plane a lot recently too. It has pneumatic wing deice boots. They've been rather "crusty" as of late too. By crusty, I mean ice bits that aren't entirely removed by the boot cycles.

A nicely equipped IFR RV is actually a VFR airplane below +5c.
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  #3  
Old 05-24-2022, 05:49 AM
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olyolson olyolson is offline
 
Join Date: Dec 2009
Location: St Louis, MO
Posts: 1,172
Default Ice

Picked up some windscreen ice on a 45 degree cloudy day at 3,000 feet. I wasn’t anywhere near the clouds or the precip in the area but I was evidently close enough to pick up the ice. Soon as I turned around and backtracked it dissipated pretty quickly. Buyer beware!

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Last edited by olyolson : 05-24-2022 at 05:55 AM.
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  #4  
Old 05-24-2022, 07:56 AM
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Jvon811 Jvon811 is offline
 
Join Date: Mar 2014
Location: GA80 Whispering Pines Airpark
Posts: 238
Default Cloud residue "testing"...

A few years ago, on a perfect mid-winter day in Michigan (note the sky in the attached picture, plenty of options to escape icing), I was curious as to exactly how my RV-4 would act with above average amounts of cloud residue.

The Airplane flew just fine, control wise, but I lost about 10mph airspeed, 150rpm at a constant MAP (FP prop) and was getting the vibrations of ice on the prop. That's when I discontinued and landed at the airport right below me. Hard to tell in the pic, but at its thickest, the ice was maybe 1/8"-3/16". Again, it flew just fine, but noticeable. I also lost my Pitot system later, but that was to be expected. Not a bit deal. Pitch, power, etc...

The takeaway I got was that I couldn't see this on my leading edge and didn't know exactly how much I had accumulated. I obviously could see it on the canopy in front of me, but this ice was too far down the leading edge for me to see from the cockpit. Just a reminder to myself of, "When you think it's fine, it might not be."

Not to mention, the tail was covered, the gear legs, the wheelpants, the spinner, the prop, etc etc etc...
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