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In-Flight Icing

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http://www.skybrary.aero/ipbforums/index.php?showtopic=27

This is a big subject! But just to add two further potential hazards from in flight ice accretion - forward visibility (windscreen heating systems can and do fail!) and ice within on-wing engine cowlings which can impede the free movement of 'legacy' aircraft engine controls (due to cowling seals not being fully serviceable or effective).

Longstanding practical experience has also taught me that the most significant stratiform icing can be expected near to the (usually fairly smooth) cloud layer tops.

I also feel that it would be appropriate to further emphasise the longstanding leadership in Europe and beyond of the AEA Ground De/Anti Icing Working Group mentioned under "Further Reading" in reliably keeping everyone up to date with the latest thinking on this subject - everything, not just the latest holdover times! It is a well-used source for all Operators who want to keep up with the latest safety standards in this field and for many years in the 1990's was way ahead of a lot of the State Regulator guidance on this particular subject - it may still be!--Chris.stewart 16:34, 21 January 2008 (CET)

As the previous comment says, this is a big subject! Could I suggest that one of the real issues for flight crew is the matter of what "certified for flight in icing conditions" really means. This phrase appears in some if not many current Aircraft Flight Manuals. I have been flying long enough to have realised that the lack of qualification - severe/moderate/light - seems to have more to do with a tacit acceptance of the subjectivity of perception than any claim about exactly what conditions an aircraft is certified for. Perhaps when the section on Certification is developed, this aspect could be specifically covered?

Could I also just add that I think it would be helpful to mention in this entry that under 'solutions' one of the most common ways of anti icing airframe leading edges (wing and tail) is engine bleed air. Although this is still very common, it dates back to at least the Vickers Viscount - although in that case, I remember that by the time the air got to the tailplane, it wasn't hot enough to do the job in descent unless some power was left on....which had caused some loss of control accidents and incidents in the days before I got my hands on one.--Joe.scott 17:42, 22 January 2008 (CET)

A couple of points: (1) Re Effects, any aircraft cleared for flight in icing conditions should have more than one fully heated pitot/static feed with the heater electric power coming from a non-shed source so that loss of vital instrument readings due to icing up is an almost unheard-of event except in cases where light aircraft have been operated beyond their limits. (2) Re Solutions, leading edge hot air systems are anti icing systems rather than de icing systems--John.Milner 02:25, 27 February 2008 (CET)

ice types

It might be worth mentioning that 'clear ice' is sometimes called 'glaze ice'. Also that rime ice and clear ice are actually extreme forms of icing in which a lot of the icing we see on airframes tends to one form or the other but is often a bit of both. This 'blend' used to be referred to as 'cloudy' or 'mixed' ice. The tendency to clear ice is, as it says here, greatest with large supercooled droplets but also when near to 0deg C - so it's worst if both these conditions prevail. Similarly, pure rime ice is, as it again says here, most likely with small droplets, but also at very low temperatures, so is at its worst if both conditions prevail.--Peter.Blackstone 22:52, 18 March 2008 (CET)