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Originally Posted by gmx
(Post 10323274)
The pilots on lion 610 were in regular contact with ATC and as late as 20 seconds before impact with the ocean they indicated their preferred flight level. This suggests they were not under duress in operating the aircraft until the very end. It is still very much unclear why their successful and consistent NU trim corrections are suddenly insufficient to counteract MCAS.
The question is why the change in flying pilot? The CVR will go a long way in answering this, if it can be found. |
PJ
The stick shaker remained active throughout the flight. PIC advised the controller that the altitude of the aircraft could not be determined due to all aircraft instruments indicating different altitudes and requested to the controller to block altitude 3,000 feet above and below for traffic avoidance. |
And the crew of previous flight also recognized there was a trim problem, but in their case almost immediately disabled the automated trim and trimmed via the mechanical trim wheels. In hindsight, some mention of MCAS in the training material would have been a good idea, but... there's a lot of systems on a modern aircraft, it is unreasonable to expect pilots to have an intimate knowledge every single one of them and how a malfunction affects control. Would knowing of the existence of MCAS make a decisive difference over knowing that there are automated systems that alter trim and that can be turned off if they cause problems? Where Boeing really dropped the ball is in allowing MCAS to continue to mess with the trim when other systems knew that the AoA data it was using was unreliable. |
Originally Posted by Lonewolf_50
(Post 10323904)
PJ
It stands to reason that the maintenance crew won't go out and trouble shoot a problem that is not brought to their attention. Your point on "where's the write up?" will hopefully get answered in due course. It has me puzzled, given the detail provided in the A-SHOR report cited on page 21. (this refers to the previous flight) One thing I found interesting on the timeline was what might have been some trouble shooting by the cockpit crew with the flaps, but that particular report points me toward a compound malfunction; you've got one problem making the pitch control a problem, and another problem presenting both pilots with confusing altitude information. (though if all that meant was "an ALT disagree alert" this might be a red herring). http://knkt.dephub.go.id/knkt/ntsc_aviation/baru/pre/2018/2018%20-%20035%20-%20PK-LQP%20Preliminary%20Report.pdf PAGE 22 The engineer performed flushing the left Pitot Air Data Module (ADM) and static ADM to rectify the IAS and ALT disagree followed by operation test on ground and found satisfied. The Feel Differential Pressure was rectified by performed cleaned electrical connector plug of elevator feel computer. The test on ground found the problem had been solved. At 2320 UTC, (29 October 2018, 0620 LT) the aircraft departed from Jakarta using runway 25L and intended destination Pangkal Pinang. The DFDR recorded a difference between left and right Angle of Attack (AoA) of about 20° and continued until the end of recording. During rotation the left control column stick shaker activated and continued for most of the flight. |
He went to 5,000 ft per the Airspeed Unreliable Checklist (table below). The Alt Disagree Checklist is quick. (Looking at the 737NG-800 QRH) Fly pitch and power as per the QRH. Next figure out why the trim is being stupid and that dumb wheel keeps spinning the wrong way. Keep the wheel in the GREEN if you have to hold the D%#@ thing.
https://cimg7.ibsrv.net/gimg/pprune....f5f9f12839.png |
Originally Posted by silverstrata
(Post 10323341)
And the engines are much more powerful - up to 30 k lb of thrust. All that extra thrust, low down on the airframe, generates a large pitch up moment - especially if the aircraft is slow and the elevator is becoming less efficient. You can actually get to a situation where the aircraft simply goes vertical, or flips over backwards. S This is nothing new - the 737 'Classic' -3/4/500 models had the same max thrust limitations - but it was done mechanically. The 737-3/4/500 models all used the same engine, one the shorter -300 and -500 models, there was a physical stop to how far the throttle could be advanced to prevent excessive power nose-up from becoming an issue. |
People looking for the report a quicker download is possible here:
Lion Air Boeing 737 MAX 8 crashed into Java Sea off Jakarta » JACDEC I believe avherald.com also has it available. |
Originally Posted by GarageYears
(Post 10323867)
I understand the intent here, but as revealed by the FDR traces, the crew of the fated flight clearly understood there was a trim issue, they repeatedly applied trim opposite to that applied by the automation (MCAS) - true, they may not have understand 'what' was applying the trim, but clearly they knew it was happening. The question is why did they not hit the cut off switches?
And the crew of previous flight also recognized there was a trim problem, but in their case almost immediately disabled the automated trim and trimmed via the mechanical trim wheels. - GY
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td #1815 So if the thrust has not changed and the revised engine mount might not contribute a significant pitching moment, then why introduce MCAS. Perhaps higher engine wt and changed location - the cg effect messed with the long stab, particularly approaching the stall; thus ‘augmentation’ was required. If this is not the issue, then the MAX handling would be essentially the same as previous models. Or did someone think that MCAS was a good idea given previous accident history. MickG0105 ‘a prepared plan is probably the enemy’ :ok: … in lieu of the absence of manufacturer’s advice, drills, and fault finding - absence of any reference to MACS. |
Four operators have reported instances of excessive stabilizer trim system coasting (stabilizer trim wheel continues to rotate) after the control wheel stabilizer trim switches have been activated and released. The reports indicate that when the pilot released the trim switches, the stabilizer trim wheel coasted up to 40 turns (four units of trim). In some instances the trim wheel stopped moving in the commanded direction and then rotated up to 40 turns in the opposite direction. |
Ian W #1794
For some reason they didn't switch the auto stab trim off. I would really like to know where that flying spanner was, as this looks like a fault finding exercise gone wrong rather than set the systems safe and land. Mad (Flt) Scientist. MCAS appears designed to give assistance to using the elevator to recover from a high AoA condition. Likely the scenario for which it is implemented also includes some combination of high thrust (causes nose-up moment) and stab trimmed to abnormally nose-up position. Both 737NG and, I think, at least one AB variant have had high pitch angle upsets in very similar conditions, and the concern for such a scenario has been the subject of more general discussions. It is still very much unclear why their successful and consistent NU trim corrections are suddenly insufficient to counteract MCAS. |
"The engineer performed flushing the left Pitot Air Data Module (ADM) and static
ADM to rectify the IAS and ALT disagree ..." which is another bag of worms opened...perhaps a translation issue? |
Originally Posted by CONSO
(Post 10323963)
THIS REPORT ??
The PIC also reported the flight condition through the electronic reporting system of the company A-SHOR. The event was reported as follows: Airspeed unreliable and ALT disagree shown after takeoff, STS* also running to the wrong direction, suspected because of speed difference, identified that CAPT instrument was unreliable and handover control to FO. Continue NNC of Airspeed Unreliable and ALT disagree. Decide to continue flying to CGK at FL280, landed safely runway 25L. Note: STS = Speed Trim System At 23:31:09 UTC, the LNI610 PIC advised the ARR controller that the altitude of the aircraft could not be determined due to all aircraft instruments indicating different altitudes. The pilot used the call sign of LNI650 during the communication. The ARR controller acknowledged then stated “LNI610 no restriction”. |
Originally Posted by underfire
(Post 10324015)
Not only a Lion Air problem.
Number: FLR-6(FR) Issue Date: August 10, 2012 |
Originally Posted by glad rag
(Post 10324026)
"The engineer performed flushing the left Pitot Air Data Module (ADM) and static
ADM to rectify the IAS and ALT disagree ..." which is another bag of worms opened...perhaps a translation issue? |
Originally Posted by safetypee
(Post 10324013)
td #1815 So if the thrust has not changed and the revised engine mount might not contribute a significant pitching moment, then why introduce MCAS. Perhaps higher engine wt and changed location - the cg effect messed with the long stab, particularly approaching the stall; thus ‘augmentation’ was required. If this is not the issue, then the MAX handling would be essentially the same as previous models. Or did someone think that MCAS was a good idea given previous accident history. All that being said, my educated guess is that your comment about it being 'a good idea given previous accident history' is probably pretty close to the mark. |
Originally Posted by tdracer
(Post 10324104)
I only know that the max thrust didn't change significantly on the MAX (no pun intended) - others have postulated that the positioning and size (diameter)/weight of the engine made things worse but I'm not in a position to comment. I wasn't close enough to the MAX program to know what drove the requirement for MCAS - my involvement on the MAX was basically limited to participating in some propulsion design reviews.
All that being said, my educated guess is that your comment about it being 'a good idea given previous accident history' is probably pretty close to the mark. A former Boeing executive, speaking on condition of anonymity because discussion of accident investigations is supposed to be closely held, said that Boeing engineers didn’t introduce the change to the flight-control system arbitrarily. He said it was done primarily because the much bigger engines on the MAX changed the aerodynamics of the jet and shifted the conditions under which a stall could happen. That required further stall protection be implemented to certify the jet as safe. |
Originally Posted by safetypee
(Post 10324013)
So if the thrust has not changed and the revised engine mount might not contribute a significant pitching moment, then why introduce MCAS. Further explanation, with pretty graphics: https://leehamnews.com/2018/11/14/bo...to-the-pilots/ |
Salute!
i don't know about you other pilots, but I would be very interested in a change to my plane that involved some aerodynamic characteristics and then a kludge mechanism that used an existing system ( that I also did not like) to 'help" me from staliing the plane and then fail to tell me about it! GASP! This is gonna be a lawyer fest, and I can also see a flight crew concern that must be dealt with by Boeing. Gums opines... |
Originally Posted by DaveReidUK
(Post 10323683)
The Preliminary Report, although it reproduces Lion Air's Safety Instruction (Appendix 5.2) which explicitly refers to "one Engineer on board", also makes it clear that he/she was included in the 181 passenger count (which, added to the two pilots and six F/As, gives the published total of 189 fatalities).
That would seem to indicate deadheading/positioning and imply a seat in the cabin, though there's no evidence offered either way for that. |
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