Originally Posted by
LOMCEVAK
PDR1,
Firstly, stalling AOA varies quite markedly with both Reynolds number and Mach number, and for a propeller driven aircraft will vary with any propwash over the wings.
Much of the earlier discussion relates to flying an approach, and speed is very important for landing distance considerations.
And it was in the context of those discussions that I made my remarks. And for aeroplanes "on approach" the Re, Mach and blown effect of propwash will be pretty similar (minor variations due to runway density altitude) so the stalling AoA will be within a tightly confined range, whereas stalling
speed will vary by much larger amounts due to differences is weight. I therefore suggest that where an accurate AoA instrument is available it is a better reference. Airspeed is used as a parametric for AoA, but it has no absolute meaning. If you don't believe me try stalling an airfoil in a wind tunnel by reducing the airspeed!
As I said before, using just AOA may not be accurate enough in some aircraft for achieving the required landing speed accuracy criteria,
As I said - there are no fundamental landing speed criteria. There are approach and landing *AoA* criteria whose achievement is measured by monitoring airspeed, but many pilots have lost track of the detail that the airspeed itself is not the fundamentally important parameter - it is a parametric for AoA.
...especially with the potentially dynamic nature of AOA indications in turbulence and attempts to fly the required flightpath under such conditions. I have had an AOA probe stick on an approach in an aircraft whereby a single source AOA indication was the main method of speed control. It was only by cross-checking the standby ASI that I identified this failure.
These are complaints about specific implementations of AoA instruments. (not really relevant, but never mind). If AoA instruments were provided with a standby and with gauging that had similar damping to that we are used to in ASIs we would find them just as usable. You seem to suggest ASI is always available in a reliable form, which is (of course) far from the truth. The history of accidents and incidents due to pitot-static errors, icing, covered ports etc etc is a pretty large book.
I do wonder from your posts whether you have ever actually flown an aircraft where AOA indications are used on the approach; the practicalities are not as simple as straight aerodynamic theory may imply!
Oh right - attack the poster rather than discuss the points, that's gonna work.