Originally Posted by takata no.128
Here are the tables of the 36 UAS events declared before the publication of 2nd BEA report; one may see that 12 cases of "suspect" STALL WARNINGS were reported (33%).
Why do you label these stall warnings 'suspect'? BEA has investigated several of these cases and writes in its Interim Report No.2:
Stall warning. Nine cases of triggering of the stall warning were observed. (...) All of these warnings are explicable by the fact that the airplane is in alternate law at cruise mach and in turbulent zones. Only one case of triggering was caused by clear inputs on the controls.
Note: At high altitude, the stall warning triggers in alternate law on approach to the stall. The stall manifests itself particularly through vibrations.
I think there are number of other statements in your post that you may wish to rethink. Alpha-prot is the AoA at which Normal Law changes from an Nz law to an alpha-law. In this connection you are several times referring to speed where the reference should really be to AoA (*). Alpha-prot is only relevant in Normal Law and I doubt it is even calculated in Alternate Law since it has no significance in that law. In Alternate(1) there is a protection called 'Low Speed Stability' that is driven by IAS instead of AoA, and changes alternate law to direct law. It is active from about 5 kt up to about 10 kt above the stall warning speed (*), depending on weight and slats/flaps configuration. Low Speed Stability is lost in Alternate (2) Law.
P.S.:: (*) For given configuration, weight, c.g., and altitude, AoA is a function of Mach
and load factor. V-alphaprot and V-alphamax shown on the speed scale of the PFD are calculated for
1 g from alpha-prot and alpha-max, respectively. V-S/W is calculated for the actual "gee" and the stall warning threshold AoA.