Icing Part 2  

Posted by y. 源

Generally, Icing is divided into two types:
1) Opaque Rime (or Rime Ice)
2) Clear Ice (or Glaze Ice)



















Opaque Rime
This type of icing that forms on aircraft skin is brittle because it normally happens when small Supercooled Water Droplets (SCWD) strike on the aircraft skin and become frozen immediately and thus trapping pockets of air inside it. Rime ice is easily removed and lighter than Clear Ice.























Clear Ice
Clear ice is normally associated with large SCWD. During impact with aircraft skin, only a small portion of the droplets freezes, while the remaining portion flows back over the surface and freezes gradually as a smooth solid sheet of ice. It is much harder to removed and heavier as compared to Rime Ice.





Effects of Icing on aircraft:
1) Increase stalling speed and decreases stalling angle
2) Increase total weight of aircraft
3) Increase drag
4) Decrease top of climb
5) Decrease rate of climb
6) Controls may frozen up
7) Lift is reduced.
8) Windscreen become blurry - Visibility is reduced.
9) Pitot head and static vent may be blocked - Pressure-related instruments will become useless.
10) Engine flame out.

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Icing  

Posted by y. 源

To those who have watched Ironman, I am sure you noticed that when Ironman and the bad guy (forgot his name) flew high up into the sky, both of them has ice particles accumulated on their armor suits.

Obviously, that is a phenomenon termed as Icing. Icing happens mainly due to Supercooled Water Droplets (SCWD) being held in suspension in the air. SCWD, as its name suggests, means that water droplets (not water vapour) are cooled down to below 0 degree Celcius and it still maintain its liquid form and not solid form.

Yes, I know you are thinking that it is impossible to have water remain in liquid form even below 0 degree Celcius.

Trust me. This is possible. And, there is reason for it. I will put it in a very simple way for you to understand.

For water vapour to condense to liquid, it needs hygroscopic nuclei. And for liquid to undergo sublimation to change its form into solid ice, it needs ice nuclei. However, when water vapour is cooled to below its freezing point and there is no ice nuclei around, that means only condensation can take place and hence water droplets are formed. These particles are what we called as SCWD and they are very unstable, mind you. They are in the air, awaiting any ice nuclei to come and form ice with them immediately.

Now can you tell me what is the biggest ice nuclei in the air?








Answer: Aeroplanes. The moment these SCWD touches the aircraft's skin, ice forms straightaway on it. Just like what you see in some of the scenes in Ironman (suit testing scene where he pushed the armor suit to the limit by flying high high up into the sky; the fighting scene where he lured his enemy to the same place too).

For icing to happen to an aircraft, there are conditions that need to be present:
1) Aircraft skin temperature is below zero and SCWD are present in the atmosphere; or
2) Outside air temperature is below zero and SCWD are present in the atmosphere.

In temperature band between 0-10degree Celcius, the air contains mainly large SCWD. Between 10-40degree Celcius, mainly mixture of small SCWD and ice crystals present. While temperature below 40degree Celcius contains only of ice crystals. Ice crystals are harmless.



For the next post, when I am free, I will post about types of Icing. And probably some of the icing consequences to an aircraft too.


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Well well  

Posted by y. 源

Thursday got back Instrument second progress test paper and I only scored 80%. Yesterday did Meteorology progress test two also and on that day itself I got back my result which is merely 80%. Damn. Next Tuesday the third progress test for Meteorology. This weekend is full of homework to do too, like, Navigation Plotting, Flight Planning calculation of fuel for climb, cruise, descend, and diversion, and also have to do the Instrument exercises.

The course is getting tougher. Damnit.

Anyway, today the bloody school cut our electricity again on this beautiful Saturday morning. With no lights on, I can't study at all man. The room is dark even though I opened the door and window. Tell me to go to the common room to study? Even there also no electricity. And they still go the cheek to tell us to study everyday. BullS**t. There is not even a conducive environment for the students to study at all. This time the reason they gave is more ridiculous than ever before. They said a big shot is coming to the school today so they have to switch off the current until he goes back. Damn a$$ right?? What kinda a$$y reason is that?? Just in case you don't know, this big shot is the one who runs this school with his money.

The only reason I could think of is that the big shot wanna cut cost to the max. We here are being deprived of many things. You know, the amount of money that we pay for this course does not represent the services and facilities that we should get! Come on, students here are the customers! I won't be surprised if he decides to open this crewroom during weekend only.


Three days ago went to watch Ironman. Not a bad movie. 4 out of 5 stars. To those who plan to watch it, don't hesitate and go ahead. It's sure worth your money.

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