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Old 7th June 2009 | 23:16
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safetypee
 
Joined: Dec 2002
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From: UK
Re: “…the heating in the TAT probes, at times, may be insufficient & lead to the probe icing up followed by the ice rapidly heating up giving false TAT & SAT indications”.

See the thread http://www.pprune.org/tech-log/37578...ml#post4963257 and technical links, some of which describe the conditions associated with TAT probe icing. Note the number of incidents at the edge or beyond the icing certification envelope and their association with adverse weather as describe in the incident.
TAT probe icing most probably accounts for reports in several posts (R&N) describing a ‘rapid’ rise in TAT, or TAT near zero. The limits of atmospheric physics makes the ‘hot air’ bubble theory most unlikely.

A point of interest is to consider if the reported airspeed speed changes originated from coincident pitot tube icing, or if the ADC uses TAT in a Mach computation, which is corrupted, causing a change in the indicated Mach and hence changing the EFIS airspeed.
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