Unreliable airspeed occurrences: does it happen more often now (e.g. past year), or merely the problem it is now getting more attention? If it does happen more often, why? Is it because some component(s) (Pt probe, transducer, etc) have degraded? Or can it be due to software changes?
I mentioned this several weeks ago, suggesting that increased frequency of severe weather conditions may be taking the probes beyond their original time of certification design limits.
The system design should ensure that no set of redundant components can degrade to a single point of failure, yet this is exactly what appears to be happening in the case of the probes. For a function that is so critical in terms of other systems that depend on it's data, why has this problem not been fixed ?. An engineering design issue that needs only the will and resources to find a solution. ie: If there's not enough probe heat at limit, redesign with more effective heating, perhaps with better insulation on the outer surfaces to prevent heat loss. If the probes are corroding due to excessive heat on the ground, redesign the probe heat controller to prevent this. If the drain holes are blocking, redesign. If there is a need to make the drain holes bigger, correct for this in the adc lookup tables etc.
The crew may recover in most cases, but should never be placed in a situation where they need to if the problem can be engineered out. After reading this thread for several weeks now and getting a feel for the status quo, the apparent industry complacency about this issue just beggars belief, imnsho…
Chris