Originally Posted by
Icarus2001
And what do you think is the reason the use of these is not more widespread? I would assume that the main reasons are: mechanical vanes are straightforward, and a standby instrument can just display a value without any computation.
But what's probably more important: they are robust. The "smart sensors" measure pressures at various holes to compute AoA, and these small holes are much more susceptible to icing and being clogged by dirt, in other words, these probes are much more sensitive to less-than-perfect environmental conditions. A partial obstruction of only one of those holes will (perhaps subtly) alter the value. And while that may be fine for an immaculately polished business jet, it is probably not ideal for commercial line operation.
How do you think any of the known accidents involving AoA probes would have been prevented by "modern" sensors?
- QF 72: A problem with the ADIRU sending wrong data to the flight control computers. Nothing to do with the mechanical properties of the sensor
- XL Airways Perpignan: AoA vane frozen solid because of improper washing procedures: Could just as easily have happened with "smart" vanes. Possibly slightly different failure more, but small orifices can easily ice over or get clogged
- Lion Air: We don't know, but possibly also data processing, or else mechanical damage or improper installation. "Smart" probes will also give undefined/wrong values when damaged or installed improperly
- Ethiopian: quite likely a sheared off vane. Any force that does that would also severely impact a "smart" probe.
So? Just because something is "old style" doesn't mean it's bad, or that newer things are necessarily better. I think AoA sensors without moving parts have not yet proven to be as good as traditional vanes.
Bernd