Originally Posted by
ursine1
Meanwhile, affected aircraft are still flying, and at the present there are no plans to ground them or even correct the actual technical issue.
I'm not a pilot, so help me out here. What would be the possible justifications for not immediately grounding these planes? (Legitimate question.)
AFAIK, the actual technical issue hasn't been nailed down yet. It appears that the AOA sensor was replaced between some of the 4 flights where anomalies were reported, which suggests that the flaw wasn't in the AOA sensor itself, but in some other aspect of various systems that all rely AOA and other air system inputs. The bulletin to reinforce a flightcrew's awareness of the importance to "RTFM" as far as NNR (non-normal recovery) procedures to deal with a potential repeat of the situation seems prudent, until a definitive culprit can be identified and corrected.
You may recall the cases of the UA 737 accident at COS, and the US 737 accident at PIT. Occurring some months apart, the leading suspects at the time were a horizontal wind rotor cloud in the lee of the Rockies in the COS case, and an encounter with the wingtip vortices of an aircraft ahead of 427. Data eventually showed that a rudder hardover was possible in a certain airspeed range, and a similar Ops Manual bulletin and AD went out mandating corrective speeds until rudder PCUs could be re-designed and installed.
Not all accident causes are clearly evident at the outset. I'm personally wondering if there might be a bad line of computer code somewhere in the system.