Originally Posted by
BOAC
[...]we appear to have a similar manouevre induced by the FCS and not the crew, resulting a (co-incidental) 'arrival' at FL380 after a 6000fpm zoom during which the IAS decayed below Vls. OK, I'm easily swayed by these things, but???????
[...]
I do not understand why the alpha reached 'alpha-prot' all on its own?
[...]
I am struggling to see, through my ignorant eyes, why this is not relevant to 447? I know, different type and 'history', but is there not an Occams Razor lurking here?
There is no indication so far the the 447 zoom climb was induced by the FCS, while there
is knowledge of PF nose-up input prior to the climb. If invoking Occam, why would you add an FCS law change as cause of climb when there is already a known nose-up input from PF ?
In the other incident, my understanding would be alpha reached alpha prot due to severe turbulence causing fluctuations in speed etc., followed by (I think) crew reducing speed after momentary overspeed warning (hence next downward fluctuation in speed maybe takes alpha momentarily over alpha prot, and engages the law).
The other difference is that the other incident is in normal law, while 447 was in alternate, which doesn't
have the alpha prot law.
[ Note: I know there are some posts on a theory that maybe 447 was still in normal law through one of the PRIMs, and therefore the climb oculd have been a protection doing the wrong thing - I think there is a fundamental flaw with that theory, which is that in normal law the FCS would never have allowed the a/c t exceed alpha max, which it clearly did. ]