It has happened again. Another catastrophic crash of a Boeing 737 Max 8 albeit with a different airline.
The MCAS feature is like those garage door sensors. Trying to mitigate a scenario that is possible but not likely (stall). However, it has lot of false positives. Detects obstructions all the time and kicks back the garage door for no reason. Unintended consequences. Assuming that what this is. Another false trigger of stall logic triggering MCAS steep dive.
Tragic ☹️ Hope this helps. My thesis on Lion Air. https://t.co/dkostNKpY3
— Shaker Cherukuri (@ProcessISInc) March 10, 2019
The previous incident with Lion Air Flight 610 is detailed here:
New York Times is reporting that there were changes made to the control algorithm. Not sure what the reference is to. Original MCAS algorithm or some changes since the Lion Air Crash?
What changes were made to the control system? Was the MCAS turned off yet?
— Shaker Cherukuri (@ProcessISInc) March 10, 2019
I sure hope the MCAS algorithm was turned off at the least.
Updated Statement by Boeing:
Hope this helps: https://t.co/dg2NsvcgL6 Will be updating it. Glad to provide assistance to your technical team.
— Shaker Cherukuri (@ProcessISInc) March 10, 2019
Reuters article on this:
Here we are again Jamie. Any idea what unstable vertical speed entails? Updating my blog as we go btw
— Shaker Cherukuri (@ProcessISInc) March 10, 2019
Flight Radar 24 Tweet/blog info:
Adding this to my blog post about this incident. https://t.co/dg2NsvcgL6
— Shaker Cherukuri (@ProcessISInc) March 10, 2019
Stakes are high here for Boeing, the Airlines and passengers.
Time to accelerate those fixes in the works assuming this incident is also related to MCAS algorithm.
— Shaker Cherukuri (@ProcessISInc) March 10, 2019
New York Times is reporting that all Chinese Airlines have stopped using the Boeing Max 8 effective immediately.
Confirmation from WSJ that China is grounding all Boeing 737 Max 8.
What is SouthWest Airlines in the US going to do? Can they turn off the MCAS algorithm effective immediately?
Something to think about though. Given service bulletin’s were sent to all Boeing 737 Max 8 pilots with details on how to override the MCAS.
https://twitter.com/processisinc/status/1104946625938669571?s=21
Indonesia follows China and grounds Boeing 737 Max 8 fleet. More to follow?
Just came across this interesting Seattle Times article. Concurs with my thesis.
FAA evaluates a potential design flaw on Boeing’s 737 MAX after Lion Air crash https://t.co/tzbXQaSEzr via @seattletimes @dominicgates just came across this in the comments section of wsj article. Concurs with my thesis. ET302 Pilots should have had the bulletin though.
— Shaker Cherukuri (@ProcessISInc) March 11, 2019
FAA will not ground the Boeing 737 Max in the US. Mandates software fix to MCAS by end of April. However,
Limiting the downward push mitigates the steep dive due to false trigger perhaps? However does it serve it purpose in case of a real stall? Those are the trade offs. Plus other unintended consequences of any design change.
— Shaker Cherukuri (@ProcessISInc) March 11, 2019
FAA statement and Continued Airworthiness notification to international community (CANIC). Design change is three pronged for MCAS algorithm.
- Activation enhancement
- Signal strengthening, and
- command limit.
The activation enhancement and command limit can and should be Engineering calibrations.
Signal strengthening requirement implies this is believed to be S/N deterioration issue.
https://twitter.com/processisinc/status/1105252844028997634?s=21
It appears the signal enhancement/strengthening might be requirement to use inputs from both AOA sensors in tandem and modify the algorithm to accommodate all inputs to arrive at a best best possible value for AOA instead of just assuming the worst input as true. This is my educated guess. Since I do not have any inside information.
https://twitter.com/processisinc/status/1105537415412887553?s=21
Updated statement from FAA below. Might revisit the Boeing 737 Max decision if Ethiopan Airlines flight ET302 data shows anything new.
Did the @flyethiopian #ET302 have the AOA mismatch indicator light? Did it ever come on? Like it did with @lionairlines #JT610 several times & the fatal flight? If not, unlikely to be the same issue? Will know soon enough. Adding this to my running blog https://t.co/dg2NsvcgL6
— Shaker Cherukuri (@ProcessISInc) March 13, 2019
Few questions to consider:
1) Did ET302 have the AOA sensor light? Did it ever come on?
2) JT610 did not have the light.
3) It appears SouthWest and American Airlines have the light
4) what are the airlines doing differently?
5) MCAS does not need the light. It knows there is a mismatch between the two AOA sensors. Needs to figure out the best possible course of action. Being addressed via the Software update in April (see above CANIC)
Grounded!
Unfortunately I was proven right on this eventually. Since the Lion Air crash. It isn’t just MCAS design issue. How did this get through FMDEA reviews is the question. Details https://t.co/dg2NsvcgL6 see lion Air post as linked in this post. Who is the lead on this? ☎️
— Shaker Cherukuri (@ProcessISInc) March 13, 2019
Ethiopian Airlines has chosen to send the black boxes to BEA in France. Interesting development given that Air France Flight 447 crash investigation by BEA led to the following fixes in Airbus:
- Stall “Alarm” algorithm logic redesign and new software
- Pitot tubes redesign and new supplier
- Cockpit protocol changes
- Pilot training
The Boeing 787Max issue is now linked to its MCAS algorithm which is an anti stall system!!
Interesting development. Given the fix for #AF447 #Airbus was new Stall logic, new pitot tube design & supplier, new protocols in cockpit and #JT610 #ET302 crashes flying #Boeing737Max linked to anti stall #MCAS algorithm. adding this to my blog post https://t.co/dg2NsvcgL6
— Shaker Cherukuri (@ProcessISInc) March 14, 2019
To be continued…
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