Originally Posted by Turbine D
So I think with proper design parameters, proper mating with the aircraft and proper testing requirements pitot probes from any manufacturer can be designed that work throughout the flight envelope.
Originally Posted by RR NDB
But i love a good design. When possible, why not to have it?
Sorry to say chaps, but such a faith in our ability to totally comprehend the atmosphere and design solution to every problem it throws at us is excessively optimistic.
Icing conditions that AF447 encountered a couple of minutes before its destruction are very rare and seldom cause trouble. Being elusive, we can't analyze them as much as we would want. All we know about them that they usually occur near "deep convections" and unlike every other known type of icing, they need the surface they hit to be heated or they won't stick, so they clog heated probes and engine compressors. I am exaggerating here but if we approach the problem narrow-mindedly, there is obvious design solution: cut heat to probes as they pick-up ice. That would make probes resilient to exotic high level ice crystals but would make them more vulnerable to every other icing condition there is and that's a lot of problems created for just one particular solved. In real world, there are no designs without downsides and designing solution for problem one doesn't even know what it is can be successful by pure chance.
Order for replacement of Thales probes was based just on empirical evidence (which is more than enough when dealing with high hazard activities such as aviation) that they are ten times more susceptible to getting blocked by high level ice crystals than rival ones. We have no idea what is in the design of probe or complete installation that makes Goodrich probe ten times less likely to get blocked than Thales but we can be sure that different performance was completely unintended. Also Goodrich probes are not completely immune and we better make sure the pilots know what to do when they lose airspeed information, like keep on flying regardless.
Originally Posted by Paull
I know that prior to AF447 the pitot-icing had already been identified and there were steps in place to change the sensors, but was any action taken to introduce this scenario into sim. flights so that we could assess what proportion of pilots would get it right?
Probably not. 30something crews got it right in the real life even without resorting to prescribed procedures. Some of them were AF.