icing

FlyBoyJae

FlyBoyJae

New Member
I was just browsing through the weather reports and this is taken from currect Duats.com

FRZLVL...
WA...SFC-030.
OR...SFC-040.
NRN CA...SFC-040 SHASTA/SISKIYOUS/NERN CA. SFC-050 NRN
SIERNEV. 040-050 RMNDR.
CNTRL CA...SFC-070 SRN SIERNEV. 050-090 RMNDR.
SRN CA...090-110.

ok, so my question is this...

normally, I find that freezing levels are beyond the capabilities of those small planes that I fly around in. But lets say that today I happened to be in a area where freezing level is as stated above...from Surface to 3000 feet.
Would this mean that I shouldn't take off at all? I normally look for pireps to make certain of the icing situation. And I believe that two requirements must be met for icing to occur; freezing temperature and visible moisture.

Given the situation, should I attempt to take off if I do not see any visible moisture knowing that the temperature is below freezing?

any suggestions?
 
Well? What would you do? Think about it... whats the safest thing to do?

Is it going to rain? Might it rain? Might there be moisture at altitude, but not detectable at the ground? Lots of questions. If I can't answer them myself, and theres no PIREP, I'm not going to take any chances.
 
It's best to be safe, first. When you decide to go, make sure you have a way out. Here's why:

Let's say you depart into IMC with a freezing level (1000 ft) above your cruising altitude and you start taking on ice at cruise. Turns out the forcast wasn't accurate. In a smaller airplane you have to decide early whether to climb above the ice (isn't always feasable) or descend out of it. Make sure you can do that.

Second, in my opinion a forcast for visible moisture near or below freezing is good enough for ice. You just never know.
 
You answered your own question Jae: There's no visible moisture!
There's no such thing as clear-air icing. No moisture, (clouds, snow, rain, mist, etc.) no ice.
If it's not clear, blue, and a million though, have a look at where the clouds sit and what the weather's going to do.
Have fun!
 
You know, you're going to get 1000 people with their personal interpretations of the regs, and nobody will be 100% correct.

It can all depends on so many things. I'll use a flight that I made yesterday as an example. It was a simple round-robin IFR flight from my airport down to KMQY. Conditions were 300 SCT, 800 BKN, 1300 OVC, -RA, BR, 7 SM with a spread of like 6/3. We were right on the edge of a cold front, and we kind of suspected that the front had already passed up. The temp had dropped about 6 degrees Celsius in the last 45 minutes, and the wind had made it's usual shift. Several PIREPS in the area, none reported any ice. FD said the temp at 6000 would be -2, so interpolation showed that ice shouldn't be a problem. That was backed up by the PIREPS and the FS briefer's info.

So, we picked up an IFR, and launched south. Went into the clouds, never got between layers. Stayed at 3000 for vectors onto an ILS 31 at MQY. Constantly in the rain, temperature hovering between 0 and 3, then started spiking up to 5 or 6 as went went further south. This was accompanied by some turbulence, so I suspected we were crossing back ahead of the front.

Did an ILS at MQY and started getting vectors back up to JWN for a straight-in GPS to Runway 20. On the downwind, don't you know it - started with just a bit of trace. OK, no biggie, 20 miles from the airport. Within about 10 minutes, we were getting a steady accumulation of rime, light-moderate. By the time we were turning onto a 10-mile final, we had a pretty good build-up or rime. You should have seen Lindsey's face as we started throwing ice on short-final!!! :)

Had ice been forecast, or if there had been PIREPS of ice, I'd not have gone. Had I been in cruise and started accumulated ice like that with no change, I'd be landing someplace. However, the ice wasn't forecast, it wasn't building at a rapid rate, and I was already in the process of getting out of the ice. And if there's no visible moisture, you can fly in the cold all you want - there's no way you can get ice!!!

Moral of the story? It's all situationally dependant!
 
Would you not consider visible moisture at an altitude where the temperature will be below 0 icing conditions by definition? The whole flight into icing conditions, versus forcast icing leaves a lot to interpretation when it comes to a/c not certfied for flight into "known" icing. It all comes down to pilot judgement and experience, and as mtsu demonstrated above, a little luck of the draw.
 
NASA has developed a very good course on inflight and ground icing which can be accessed here:

http://aircrafticing.grc.nasa.gov/index.html

Click on "Courses"

I think that it can also be purchased from Sporty's on a CD, but I got mine for free by writing to NASA. Unfortunately, I don't have that link anymore.

Buller?

MTSU, just because it's below the freezing point doesn't mean that you're good to go. SLD (super-cooled large droplets) can remain in their liquid state for quite some time below freezing... You just might become the first one to make a PIREP! ;)

If I thought that there was even a chance that I might see ice, there's no way I'd go flying around in a GA airplane with no anti/de-ice equipment.
 
mtsu_av8er said:
And if there's no visible moisture, you can fly in the cold all you want - there's no way you can get ice!!!
Click to expand...

That is very true, but you still need to be carful. I was flying over a series of lakes once with the temp right around 0. Every time we flew over a lake (I think we were 4500AGL or so) we would start to pick up trace ice. As soon as we were across the lake it would melt off. Strange stuff.
 
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