NTSB Announces Detailed Criticism Of Ethiopia’s Max 8 Accident Findings


Almost a month after releasing comments criticizing the Ethiopian Aircraft Accident Investigation Bureau (EAIB) for its final report on the March 2019 fatal accident of a Boeing 737 Max 8, the U.S. National Transportation Safety Board (NTSB) today (Jan. 24) released new comments challenging the Ethiopians. Today’s comments offer details involving the EAIB’s conclusion as to the source of faulty angle-of-attack data and “insufficient attention to the human performance aspects of the accident.”

While the board’s Dec. 27, 2022, statement acknowledged the role of the Max 8’s much-criticized Maneuvering Characteristics Augmentation System (MCAS) in the accident that killed all on board Ethiopian Airlines Flight 302 shortly after takeoff, the NTSB now says that the EAIB’s report unfairly blamed the manufacturer for electrical problems that caused erroneous angle-of-attack output.

Today’s NTSB statement read, in part, “The EAIB wrote electrical anomalies that existed since the time of the accident airplane’s production [italics added] caused the AOA sensor heater to fail, which resulted in the AOA sensor providing erroneous values that caused MCAS to repeatedly pitch the nose of the airplane downward until it struck the ground.

“But the NTSB found the erroneous AOA sensor output was caused by separation of the AOA sensor vane due to impact with a foreign object [italics added], which was most likely a bird. During the accident investigation, the NTSB provided the EAIB with evidence supporting this finding, but that evidence was not included in the final report.”

The board further wrote, “The AOA sensor vane heater’s function is to prevent ice formation that could restrict vane movement. The conditions present at the time of the accident were above freezing temperatures with no moisture present (that is, ice could not form regardless of the heater’s operational status). Thus, a loss of electrical current through the vane heater at any time during the accident flight would not explain the event because the loss of electrical current would have had no effect on the AOA sensor output.”

The NTSB also cited as “misleading” the EAIB’s findings on Boeing’s alleged lack of documentation for flight crews regarding the correct procedures in the event of a failed sensor causing the MCAS system to induce nose-down autopilot flight commands. “Boeing had provided the information to all 737 Max operators four months before the Ethiopian Airlines crash,” according to today’s NTSB statement.

Mark Phelps
Mark Phelps is a senior editor at AVweb. He is an instrument rated private pilot and former owner of a Grumman American AA1B and a V-tail Bonanza.

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  1. Ethiopia’s institutions are shaky, just ending (suspending?) a war within its own borders, and generally allergic to strong relationships with the US and Europe. It doesn’t come as much of a surprise that they may not have the bandwidth or professional capabilities to conduct an investigation at a fully professional level. Isn’t this the crash where the FO had 280 hours TT? Pity the captain.

  2. Here is the inept NTSB trying to tell someone else how to perform an accident investigation, when NTSB can’t even handle their own. They are guessing at what caused the failure, so don’t try to criticize others until you get your own house in order.

    • Well, they may be actually inept. But in this case, the NTSB simply said the output data pattern was consistent with, not absolutely, with a sudden impact (of something). For example, if the sensor output rose or fell with an angle spread over say, 500 msecs before the failure, it could mean the sensor was deflected by something before total failure. An electrical failure of the sensor circuit itself would have a different, more vertical electrical signal profile. Or simply and end to the data with no electrical transition at all. Regardless, they correctly stated the heater circuit the Ethiopians blamed was uninvolved in the sensor data. Nothing else the NTSB said was absolute.

  3. One might also ask why a critical-to-flight system (MCAS) was fed data from a single AOA vane. Seems like a triumph for the bean counters and a potential death sentence waiting to be imposed on a marginally-trained crew and their unsuspecting pax.

    • THIS.
      I was and am still shocked at how Boeing didn’t design the system with redundancy. There should be 3 AOA vanes, but anything less than 2 is downright stupid. Really really dumb, IMHO.

      • There was an option for a second AOA vane. American Airlines opted for it. If the vanes disagreed, MCAS wouldn’t activate.

        • That’s incorrect. The option was for an AOA display on the screens, not for a second system. All of the 737 have a left and right AOA vane. The version 1.0 of MCAS only looked at one of them. Version 2.0 looks at both and also does a reasonableness test which is basically as good as a third sensor.

    • This question has been asked myriad times since the first crash, and it was indeed an inexcusable design flaw. It cannot be ignored, however, that the symptoms of the failure were those of an electric trim runaway, and any competent airline pilot would immediately recognize an uncommanded trim input and know the solution. The same exact symptom of repeated uncommanded nose down trim could be the result of a typical electric trim runaway, the MCAS system’s idiotic design just made that type of failure more likely.

  4. After watching “Downfall”, and observing the politicization of our countries previously venerated agencies I find myself suspicious of the NTSB’s findings and criticisms of the EAIB.

  5. The NTSB fails to mention the captain’s failure to take the most remedial action of reducing power. He became a passenger when he let it all go with takeoff thrust. A major reduction in thrust combined with the runway trim procedure would have almost certainly saved the day.

  6. Ironically, the FO (who was reported as only having 200 hours) had the solution- “Stab Trim Cutoff”, which would’ve deactivated the MCAS function. The captain overrode his advice, and continued the ride to hell…

    • Yes indeed. He obviously got the message in type training. But, cutoff switch also needed a large power reduction.

  7. I started as a civilian pilot 62 years ago as a gasboy taking flying lessons. Progressed through military, flight test and 35 years as an airline pilot. Worked many years in military aircraft design, as an accident reviewer and consultant. The above comments are very valid – there are many problems with various countries investigations of aircraft accidents – mostly due to political and economic concerns or perhaps lack of competency. This includes the USA.

    Very disturbed about all the hype and poor videos on the failures of this system and lack of training. It is definitely the same type of system installed on Boeing and other aircraft – mostly T-tailed jets – only it is now computer controlled. Comments on failure to train on upsets is certainly valid. I flew and instructed for a decade on B-727 aircraft that all had stall warning and stick pusher systems (almost identical to the operation of MCAS) and never was given any instruction on “recovery” or actions if inadvertent activation of the system occurred – which was essentially what happened to the 737 max. Although the installation of the MCAS was to prevent rapid pitch up with excessive thrust and not to prevent “deep stall”.

    • We come from the same era. I had more time in the 727 than any other of the four jet transport airplanes I flew. I believe the correct reaction to a false stick shaker would have simply been: fly the airplane. Not nearly as bad as a runaway trim.

  8. This seems like piling on by the NTSB. I don’t think anyone in the aviation world thought they were going to gain new insight into the MAX crash by reading the Ethiopian report on the accident. It’s naive to think there isn’t political pressure and influence on the EIAB members just like there is on the FAA and NTSB. The NTSB made their objections, to the report, known a couple of weeks ago, it’s time to move on.

  9. The usual dirty corp.-govt. relationship, covering their failed hands-off oversight policy.

    Impossible to ignore Boeing’s own internal messages:

    “I’ll be shocked if the FAA passes this turd.”
    “This is a joke. This airplane is ridiculous.”
    “This airplane is designed by clowns, who in turn are supervised by monkeys.”
    “Would you put your family on a MAX aircraft? I wouldn’t.”
    “Jesus, it’s doomed.”

    The EAL captain had 8,122 flight hours, including 4,120 hours on the Boeing 737, and the airline flies to multiple U.S. cities, i.e., FAA certified.