Hi,
Owain Glyndwr
Don't you think that the problem might be both more subtle and more complex than just the amount of heat applied?
Certainly is for both FR and US probes
Why did it seem to be almost limited to one particular design of probe? (well by about 10:1 anyway)
Both probes showed limitations. My feeling is:
FR, probably many factors, like you put (geometry, etc)
US, less critical and probably requiring a little bit more heat when facing conditions near limit.
Look, i am trying to simplify (not always possible) because the AS probe principle of operation is VERY SIMPLE. What you need:
-A "certain geometry" (Henri Pitot invention)
-Heating above a certain threshold when facing conditions near limit.
-Other characteristics derived from the environment (moisture, heat, need to drain, etc.)
The short duration of the "failures" suggest that:
The heating may be near the required amount or not being applied fast enough due thermal inertia due geometry, geometry of the "heater" or a combination of aspects related to thermal characteristics.
I am anxious to analyze deeply the 30+ UAS cases to look for:
AUTO or ON mode selected and recorded (consistent) data during the transitory.
I understand the valid information is not recorded during the incidents like AS SIMPLY not measured in AF447.
I don't know - does anybody else?
My feeling is, we are near the required heat. Statistically based and considering AS probes (simple devices) did not fail. Just a brief erratic output.
Did the crystals melt and refreeze? Are the internal diameters critical? Or the radius at the corner of the 'L'? Or the actual location of the drainhole? Would the distribution of the heating along the length of the 'horizontal' bit of tube be important?
Good questions. I don't know.
In normal law any further THS nose up movement is inhibited when alpha protect switches in. I can't for the life of me see why this logic was not carried over to Alternate and stall warning respectively.
Thank you for direct answer!
Rgds,