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ymb1
ymb1
8:32 AM
I don't think this question can be answered factually. — Federico ♦ 7 mins ago
 
Federico
Federico
yeah?
 
ymb1
ymb1
@Federico I didn't see your comment while typing my answer, if you think it's better to delete it and put the Q on hold, let me know
takes time to type no? :P
 
Federico
Federico
don't know. I would not say that yours is really answering the question, it's a bit more lengthy comment.
if you could extract some significant statistical numbers, it might answer the question
 
ymb1
ymb1
0 accidents for the -900
 
Federico
Federico
over how many flight hours? is that statistically significant for a commercial plane?
one thing is having 0 accidents with 3 flight hours, another is with 20 millions
 
ymb1
ymb1
8:38 AM
compared to?
that's the issue, I've deleted it
 
Federico
Federico
I would compare it to the early 737s probably, as those are around since a while. the problem is that I don't know how to measure statistical significance, I would need to go and ask on Cross Validated
 
 
6 hours later…
FreeMan
FreeMan
2:41 PM
I don't know enough about the 2 recent 737 MAX 8 crashes, but I do know that questions about ongoing investigations are verboten, so I'll ask here.
Are there enough similarities between the 2 incidents that there could possibly be a common, design or software related issue that caused them both?
I'd have to assume so since EASA has temporarily banned them from Western Europe, but, as I said, I've not read enough about the two to know.
 
Dan Hulme
Dan Hulme
3:23 PM
well, there's not enough known about the Ethiopian one to rule anything out
 
FreeMan
FreeMan
thanks @DanHulme. I believe that's the 2nd crash? Sounds like it was shortly after take off. Not sure what happened with the Lion Air crash.
Just wondering. I'll leave speculation to the professionals.
 
Dan Hulme
Dan Hulme
3:40 PM
some information is available with the Lion Air one, and it's significant that Boeing, who is involved with the investigation, has chosen to release a software update to MCAS to change its behaviour in the case of a faulty AoA sensor
The Ethiopian one is just an unexplained dive into terrain, at this point. That's in common with the Lion Air one, and they're both the same type.
as always, avherald has a summary of the good info, as long as you don't read the comments
 
FreeMan
FreeMan
I noticed the comments on a different crash were a bit... volatile...
 
 
4 hours later…
Federico
Federico
8:19 PM
holy moly
> Boeing has grounded its entire global fleet of 737 Max aircraft
 
Rory Alsop
Rory Alsop
8:58 PM
@Federico that's pretty damn scary
 
Federico
Federico
9:22 PM
not sure scary is the word I'd choose, tbh. I think that they need to run for cover since the coverage of the accident is putting quite some fear in the wider public (cue the swath of questions/new users in the last 2 days here, we doubled visitors w.r.t. a normal day). it is for sure a bit concerning, maybe not unexpected at this point.
professionally, I am pissed that two aircrafts full of people were lost apparently in cimilar circumstances, and that the company making them initially reacted with a "nothing to see here"
 
ymb1
ymb1
9:59 PM
it's too early I know, but I'm more concerned with the certification requirements, presuming it's the MCAS, how on Earth does inconsistent voting not render the system disabled, airbus with its fancy envelope protections throws in the towel for most protections when the ADIRU's disagree
regardless of the pilot's supposed ability to override the system
I don't want to ask this question yet [on the site], but do jetliners really need AoA sensors? from Boeing's Aero:
 
TomMcW
TomMcW
10:32 PM
@ymb1 How else would the stall warning be triggered? Or are you really asking if they need an AoA indicator in the cockpit?
 
ymb1
ymb1
via computed weight, like Airbus does when there is a disagreement
looks good enough since airspeed and Mach are primary as that info graphic reads
if pitots are blocked, then still adjusted GPS speed to altitude and weight and pitch, they seem to be more reliable
plus plenty of planes don't have AoA probes, I don't know the largest that doesn't, but the small ones certainly don't (unless it's an after market addition)
 
TomMcW
TomMcW
11:05 PM
@ymb1 Afaik, until FBW, AoA probes were just connected to the stall warning. Some Cessna's have a little AoA tab on the leading edge to trigger the stall warning. The FBW system prob needs it for the control laws, etc.
Obviously, a long as they are working, AoA vanes are the most accurate way to detect a stall. They just revert to the other systems when the vanes are not working. I can't explain why Boeing would have an automatic system move control surfaces when both probes don't agree. Seems like that defies common sense.
 

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