What type of icing is this?

[Wolfala]

Thursday night into Friday morning I was doing IFR training with a student. We had been at 7k from San Jose down to Santa Barbara and then got diverted into Burbank because LAX decided to change runways for their arrivals and gave a not so nice EFC time.

So on the way back from Burbank to Hayward, we flew via Santa Barbara to V27 which shoots right up the coastline - over the Pacific and Vandenburg ranges, Hunter MOA and through Big Sur, Monterey, etc.

It was around 4am, where the freezing levels were somewhere between 8-9k, we were at 7k which was right at the MEA. About 5 miles before we hit the Big Sur VOR, over rising terrain suddenly the freezing took a massive **** and became 1 with us. It would've been another 20 miles to get clear of Monterey at 7000 to get out of the stuff - so with the pacific close by we deviated west and headed over the ocean to get clear of the stuff.

Now 90% of the flight was in rain and IMC- this portion was no different. When I took the photos, what caught me was the amount of run back along the wing. Was this freezing rain that we got caught in?

Frenchy?

[lasersailor184]

Cream Cheese icing.

[Rollins]

Huge?

[Tarmac]

I'm no expert, but based on an aircraft icing paper I wrote for a 200 level intro to meteorology class:

   The primary condition necessary for ice to form is, not surprisingly, a temperature below 0° Celsius.  However, the primary method of ice formation on aircraft involves supercooled water – liquid water that is at or below 0°C.  Unknown to many, water often requires a solid surface to freeze on.  Called condensation nuclei, usually airborne pollutants or other tiny solid particles, these are a surface for freezing water drops to adhere to.  It is not until -40°C that ice will form without a condensation nuclei.  If an aircraft flies through a cloud of supercooled water (between 0 and -40°C), it will function as a giant condensation nucleus, and ice will begin to form.  At the 0°C level, there are mostly supercooled liquid droplets.  The higher a plane travels, the more of these droplets freeze, or glaciate, until the aircraft reaches an altitude at which the temperature is -40°C, and all of the cloud droplets are glaciated.  Because the most supercooled droplets are found just below freezing temperatures, about 50 percent of icing cases occur between 5,000 and 13,000 feet.1  

And here's what you probably ran into:

   Even more hazardous to aircraft than supercooled droplets are SLDs, supercooled large droplets.  SLDs, which include freezing rain and freezing drizzle, are much larger than normal cloud droplets.  Cloud droplets are classified as having a diameter of less than 40 microns, while freezing drizzle and freezing rain have diameters of 40-200 microns and over 200 microns, respectively.  SLDs are more hazardous than normal supercooled cloud droplets because they freeze slowly when they make contact with a plane.  The liquid water can run backwards after impact, leaving a trail of ice across a long segment of the wing.  Since most wing de-icing devices are on the leading edge, the ice from these droplets can pose a significant hazard.  In addition, these large drops have a tendency to freeze in a rough pattern, causing greater disruption to airflow than their smaller counterparts.

And as for what type of ice it was:

 

   Conditions for icing dictate when ice forms on an aircraft, and these conditions also affect the type of ice that forms.  There are three main types of ice: rime, clear, and mixed.  Rime ice is jagged and crystalline in appearance.  It forms when small water droplets impact the wing’s leading edge and freeze rapidly.  Rime ice is mostly formed in colder temperatures below -15°C. Rime ice is the most common form of aircraft icing, but is generally regarded as the least dangerous.  It is easily spotted by pilots because of its jagged, milky white appearance; it is easily removed by de-icing equipment because it is brittle and usually forms on the leading edge of an aircraft’s wing.  Clear ice is more dangerous than rime ice.  It forms when water droplets impact on the leading edge of a wing, and then flow backwards, freezing gradually.  Because clear ice must freeze slowly to form, it forms in a narrow temperature range (usually between 0 and -10°C) and is less common than rime ice.  Clear ice is most hazardous when caused by large droplets, because these SLDs often flow for much of the width of an aircraft’s wing before freezing.  However, smaller droplets can also flow backward along a wing.  This flowing makes clear ice extremely dangerous, as air bubbles are worked out during flow, making the ice clear and difficult for pilots to see.  The flowing also causes the ice to form behind the leading edge of the wing, where deicing equipment is usually not present.  Clear ice is stronger than rime ice, making it more difficult for de-icing equipment to remove.  Mixed ice contains both rime and clear ice, giving it properties somewhere between both other types.  It is not as dangerous as clear ice, but more dangerous than rime ice.  Mixed ice is usually caused in areas where an aircraft is experiencing temperature or water droplet size variation.  Since small droplets are likely to form rime ice and large droplets are more likely to form clear ice, a combination of the two sizes can form mixed ice.  

Hope that helps... it will make my entire undergrad career.  

[JB88]

naw.  that's plain old sugar frosting.  if it was cream cheese it wouldn't crystallize like that.

[Angus]

Streaks.

You may have been lucky there....

[eskimo2]

[SFRT - Frenchy]

I'll go for clear ice. I call clear ice whatever runs back along the wing like you have. I call rime ice whatever accumulate on the leading edge and looks white. Freezing rain might be it also.

My policy with ice, and might not be the safest one, is to not freack out as long as it keeps the shape of the wing. If I have 2 inches that still foolow the shape of the wing, my airflow is still alright, and all I have is weight. Even if I carry an insane 300 lbs of ice, I'm rarely 300lb over gross weight.

The only time for me that craped hit the fan is when it's doing the one big flat leading edge of the wing, or zillions of tiny horns like here:
.

 ... or right after the leading edge of the wing with the clear ice, like an airbrake.

Anyway, ATC is always pretty good at giving you the TOP/bottom, and while planing your flight don't forget to browse Pireps. You might also be much safer at 16,000ft without oxygen in the clear than at MEA all iced up.

 Ice is often not too big of a deal. But, in the 402, I entered clouds where I went from clean to not being able to maintain altitude in less than 2 minutes:eek:

Good job on getting out of it.

[Meatwad]

Looks like ginormous ice