Indonesian aircraft missing off Jakarta
Psychophysiological entity
Mr Cheese
First, there is that AND word, which an earlier poster suggested, ' . . . AND, and etc., etc.'
Again, wording is so critical. But your main point: while the extent of the trim via the mini-corrections IS variable, (i.e. Mach), for the most part the repeated blips are very similar on the graphs available to us. Although the Mach modification is very small, it does get me wondering what it was doing during the fatal dive.
yes, but limited to 2.5 AND each time - depending on speed and AoA. It appears as though everyone is assuming it trimmed at the max limit each time - and I’m curious where that information is found. How do we know, for example, MCAS didn’t trim 1.3 AND each time, if that’s what speed and AoA called for? Or 0.7 . . .or 2.1?
Again, wording is so critical. But your main point: while the extent of the trim via the mini-corrections IS variable, (i.e. Mach), for the most part the repeated blips are very similar on the graphs available to us. Although the Mach modification is very small, it does get me wondering what it was doing during the fatal dive.
Join Date: Dec 2014
Location: Schiphol
Posts: 475
Likes: 0
Received 0 Likes
on
0 Posts
Rounded estimate of the status of the identification process based on public information - and excluding empty seats:
About 50% of those in front rows have been identified.
About 25% of those in the back rows have been identified.
The cabin apparently had seatrows numbered 1-34 but probably excluded rows 13 and 14 (in spite of 1 passenger mentioned to be in 13).
Standout is seat column F which has the largest percentage missing.
From the data it is not possible to estimate where the 3+3 cabin crew were seated. A guess is that at least 1 in a front folding seat, and 2 at the back galley, with the 3 trainees in row 1 seats DEF.
It suggests a nose down impact and right hand roll (more than 90 degrees would not surprise me).
About 50% of those in front rows have been identified.
About 25% of those in the back rows have been identified.
The cabin apparently had seatrows numbered 1-34 but probably excluded rows 13 and 14 (in spite of 1 passenger mentioned to be in 13).
Standout is seat column F which has the largest percentage missing.
From the data it is not possible to estimate where the 3+3 cabin crew were seated. A guess is that at least 1 in a front folding seat, and 2 at the back galley, with the 3 trainees in row 1 seats DEF.
It suggests a nose down impact and right hand roll (more than 90 degrees would not surprise me).
Join Date: Jul 2009
Location: Not far from a big Lake
Age: 82
Posts: 1,454
Likes: 0
Received 0 Likes
on
0 Posts
MCAS was not introduced to make up for deficient elevator nose down control authority. MCAS is there to improve handling characteristics as proscribed by the FARs at elevated AOA. The pilot has plenty of control power to lower the nose via the column. That is not the issue
FCeng84, could this statement be also interpreted as fixing a non-linearity in control response at high AOA? Is that the type of improvement in handling characteristics being created?
Join Date: Dec 2006
Location: Florida and wherever my laptop is
Posts: 1,350
Likes: 0
Received 0 Likes
on
0 Posts
Mr Cheese
First, there is that AND word, which an earlier poster suggested, ' . . . AND, and etc., etc.'
Again, wording is so critical. But your main point: while the extent of the trim via the mini-corrections IS variable, (i.e. Mach), for the most part the repeated blips are very similar on the graphs available to us. Although the Mach modification is very small, it does get me wondering what it was doing during the fatal dive.
First, there is that AND word, which an earlier poster suggested, ' . . . AND, and etc., etc.'
Again, wording is so critical. But your main point: while the extent of the trim via the mini-corrections IS variable, (i.e. Mach), for the most part the repeated blips are very similar on the graphs available to us. Although the Mach modification is very small, it does get me wondering what it was doing during the fatal dive.
Regardless of wordings in spec, the pitch trim position can be seen to 'ratchet' down in 3 full steps without correction back by the PF who just blips the trim. From the scale on the left of the image the stab trim reached max nose down.
Join Date: Sep 2002
Location: La Belle Province
Posts: 2,179
Likes: 0
Received 0 Likes
on
0 Posts
Something I'd not noticed before on that FDR data - not sure it's been remarked on. At the VERY end of the trace, the stab is seen to apparently move a long way back towards to trim state. Given the compressed scale, it's not possible to see if that is a "final instant" artifact and not "real" or if there's an actual slope to the stab trace. If it's "real" it indicates that the stab remained under the potential for crew control throughout the flight to the very end, and that the ratcheting prior to that was not "uncorrectable".
Join Date: Feb 2009
Location: Seattle
Posts: 379
Likes: 0
Received 0 Likes
on
0 Posts
The issue that MCAS addresses is non-linearity of Cm-alpha stability derivative. The pitching moment generated by the elevator (and thus the column) is much more linear. As I have mentioned in previous posts, it is not a matter of the pilot having insufficient ability to generate pitching moment via the column. The issue is that as AOA increases into a range higher than normal operation (near and beyond the AOA for stick shaker activation), the amount of nose down pitching moment generated by additional increase in AOA is not sufficient to require the FAR mandated increase in column pull to balance.
Join Date: Jun 2014
Location: Chocolatetown
Age: 63
Posts: 83
Likes: 0
Received 0 Likes
on
0 Posts
What remains to be seen is how ambiguity in the QRH, distraction, lack of training, a flying spanner, CRM, or perhaps even crew competency factor in as possible contributing causes.
"We study and discuss accidents so we don't become the subject of a thread on PPRuNe."
I am with gums on this one, in terms of "if something moves the flight control surfaces, the pilots need to be aware that it exists and how it helps them, and thus some training/education is required." Also needed for safe operations is "what turns it on or off" if it moves the flight control surfaces.
That quoted "executive" needs a talking to from the pilot's union.
Anything that is built can break, anything with computer code or electricity involved can malfunction.
Question on the MEL: is one AoA sensor INOP a downing discrepancy? I'd assume so, but I've been surprised before.
That quoted "executive" needs a talking to from the pilot's union.
Anything that is built can break, anything with computer code or electricity involved can malfunction.
Question on the MEL: is one AoA sensor INOP a downing discrepancy? I'd assume so, but I've been surprised before.
Join Date: Jul 2008
Location: Skating away on the thin ice of a new day.
Posts: 1,116
Received 13 Likes
on
8 Posts
CT with all due respect... I don't see anyone disputing that Boeing's MCAS system ran the nose down and crashed the jet killing 189 people, but it is noteworthy that two switches may have prevented this tragedy.
What remains to be seen is how ambiguity in the QRH, distraction, lack of training, a flying spanner, CRM, or perhaps even crew competency factor in as possible contributing causes.
"We study and discuss accidents so we don't become the subject of a thread on PPRuNe."
What remains to be seen is how ambiguity in the QRH, distraction, lack of training, a flying spanner, CRM, or perhaps even crew competency factor in as possible contributing causes.
"We study and discuss accidents so we don't become the subject of a thread on PPRuNe."
Join Date: Sep 2002
Location: La Belle Province
Posts: 2,179
Likes: 0
Received 0 Likes
on
0 Posts
B-737-8/9 MMEL on FAA website (rev 1, Jan 2018) only mentions AOA heater as related MMEL option; AOA sensor itself does not appear on MMEL. (Based on a few search terms)
Join Date: Mar 2014
Location: WA STATE
Age: 78
Posts: 0
Likes: 0
Received 0 Likes
on
0 Posts
from this SLF- when ONE faulty sensor input allows " hal " to override manual control AFTER correction by the pilots without warning or deliberate reset, without notice, or mention, the " chain of command" which allowed/approved/designed such a process to be incorporated needs to be held responsible.
Psychophysiological entity
Well yes, but the majority of the thread is leaning towards the stabilizer not being disabled. Something is nagging away in the back of my mind. Stabilizer runaway memory actions are so fundamental that the thread's detective logic changed quickly to looking at the ~5 second delay adding to the confusion of an already chaotic flight-deck - causing a radical diversion from old established SOPs.
The relatively calm ATC and the prolonged period of approximate hight holding, coupled with the huge handful of power in the last moments, is leaving me with a mind that's wide open.
The relatively calm ATC and the prolonged period of approximate hight holding, coupled with the huge handful of power in the last moments, is leaving me with a mind that's wide open.
Join Date: Apr 2018
Location: KDCA
Posts: 26
Likes: 0
Received 0 Likes
on
0 Posts
It's not even clear that the previous crew diagnosed a "runaway"
EDIT: climber314 pointed out that the preliminary report says they followed the Runaway Stabilizer NNC. Hopefully we get more specifics on this later.
Last edited by Roger_Murdock; 7th Dec 2018 at 01:14.
Join Date: Jun 2014
Location: Chocolatetown
Age: 63
Posts: 83
Likes: 0
Received 0 Likes
on
0 Posts
Join Date: Dec 2018
Posts: 48
Likes: 0
Received 0 Likes
on
0 Posts
While it does not present itself as continuously running run-away automatic stabilizer motion, with the airplane flying at a relatively steady flight condition repeated instances of the system moving the airplane away from the trim condition that the pilot has established manually should be recognized as improper automatic stabilizer operation and disabled via the cutout switches.
As far as we can tell, MCAS is intended to provide a more consistent and predictable handling response in incipient stall conditions.
How does an intermittent and unadvertised control input, of complex algorithmic intensity, every 5 seconds, provide that?
Join Date: Apr 2018
Location: KDCA
Posts: 26
Likes: 0
Received 0 Likes
on
0 Posts
Join Date: Jun 2014
Location: Chocolatetown
Age: 63
Posts: 83
Likes: 0
Received 0 Likes
on
0 Posts