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Old 25th May 2011, 16:57
  #2377 (permalink)  
takata
 
Join Date: Jun 2009
Location: Paris
Posts: 691
Originally Posted by Graybeard
Maybe one reason for not testing the pitot for icing at high altitude is the lack of an objective test. Airframe, and presumably pitot, icing testing is performed at lower altitudes by following a plane that sprays droplets.
They use also wind-tunnels, but their capacity for simulating "cruise conditions" (speed, temp, particles etc.) are actually too limited. Nonetheless, such tests are showing that probes don't freeze at the same rate as it is a very chaotical process.
The other factor, in fact the primary factor, is to identify (then modeling) the threat in order to address any probe/sensor design flaw: it is probably an ice crystal which size is about a flour grain but may be encountered in very high density ratio in particular conditions. Nobody is able to recreate it in lab and there is no means for taking a sample back into the lab (as no atmosphere sample can survive out of its environment!). This issue need to be studied in situ (into those specific tropical clouds)... and if such phenomenom exist, it is far from being a frequent one.

Originally Posted by Graybeard
Takata, what is the source of your info that pitot icing in light General Aviation "is one of the main accident cause."?
You should be able to retrieve it by googling for "pitot+ice": I don't have it here but I think it is taken from a symposium (around 2007) which was addressing those pitots issues, and more generaly those icing problems. There was a dedicated site with several dozens of very interesting papers made by scientists working on such problems for years (this is far from being new, this issue affects everybody in the industry).
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