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'But the FAA said that other civil aviation authorities had not "provided data to us that would warrant action".' Pretty sure the data is that two planes crash

'But the FAA said that other civil aviation authorities had not "provided data to us that would warrant action".' Pretty sure the data is that two planes crashed in five months in perfect weather conditions, killing everyone on board. Statistically, that's sufficiently improbable that it warrants investigation.

renholder 8y ago
Most would even say statistically significant enough to order the planes grounded in their own countries...
buboard 8y ago
> Statistically, that's sufficiently improbable Is it?
- kickopotomus 8y ago
  Yes, it is. The 737 NG (700 series, 800 series, etc) has a hull loss rate of 0.27 per million departures[0]. I am having difficulty finding the exact number of departures for the MAX but 737s average about 3-5 departures per day[1]. Only 350 MAXs have been delivered and the first one was delivered on May 6, 2017[2] (676 days ago). So even being generous and supposing that all 350 aircraft were delivered exactly on May 6, 2017 and that each plane made 5 flights daily, that would be a total of 1,183,000 flights. Therefore the MAX line has a best-case hull loss rate of 1.69 per million departures. I.e. the MAX generation has a hull loss rate 6.25 times that of the NG line. [0]: https://en.wikipedia.org/wiki/Boeing_737#Accidents_and_incidents https://en.wikipedia.org/wiki/Boeing_737#Accidents_and_incid... [1]: https://www.researchgate.net/publication/274782362_Characterization_of_the_Frequency_and_Nature_of_Bleed_Air_Contamination_Events_in_Commercial_Aircraft https://www.researchgate.net/publication/274782362_Character... [2]: https://en.wikipedia.org/wiki/Boeing_737_MAX https://en.wikipedia.org/wiki/Boeing_737_MAX
  - buboard 8y ago
    the question is if this difference is statistically significant
    - kickopotomus 8y ago
      You are taking a commercial flight. You have the choice between 2 different aircraft which are essentially identical but you are more than 50 times more likely to crash in one of them. Which do you take? EDIT: I have learned that I was far too generous with the flight numbers. The MAX series has only logged ~150K flights. Therefore it's hull loss rate is roughly 13.33 per million making it almost 50 times more dangerous than the NG line. Yes, the difference is statistically significant.
cesarb 8y ago
> Pretty sure the data is that two planes crashed in five months in perfect weather conditions Not only that, but the data we have so far from the second crash (ADS-B data showing irregular vertical speed, see https://www.flightradar24.com/blog/flightradar24-data-regarding-the-crash-of-ethiopian-airlines-flight-302/ https://www.flightradar24.com/blog/flightradar24-data-regard...) is consistent with both accidents having a similar cause. Grounding all airplanes from the same model until preliminary data from the (already recovered) flight recorders can confirm or discard that hypothesis is prudent.
- Recurecur 8y ago
  If it was a "similar cause", it is absolutely pilot error. The MCAS system, at fault in the first crash, may be disabled via a cockpit control. In other 737s, moving the stick was sufficient to disengage it. For some reason, this was changed in the Max, and you must use the other control. However, any competent pilot would know every control in the cockpit. The captain of the latest flight to crash allegedly had 8,000+ hours of flight time. If an aircraft begins behaving incorrectly, the first thing a flight crew should do is disable automation and try and fly it manually. That wasn't done if MCAS caused the crash. This was an emergency that developed over minutes, not seconds, and there's really no excuse.
  - julianlam 8y ago
    Unless I am mistaken, the regular 737s do not have the MCAS installed,just the MAXs (https://theaircurrent.com/aviation-safety/what-is-the-boeing-737-max-maneuvering-characteristics-augmentation-system-mcas-jt610/ https://theaircurrent.com/aviation-safety/what-is-the-boeing...) Additionally it has been suggested that documentation for this physical switch is not well laid out or presented in the manual because Boeing was confident that it would simply stay out of the pilot's way during flight. Assuming pilot error would seem to be premature if these points are in fact true.
    - mjburgess 8y ago
      Either way "pilot error" is defined with reference to some "reasonable level" of competence with the aircraft. If multiple pilots are making the same error the issue is with the aircraft changes, not the "reasonable competence". Ie., its redesign hasn't been thought through properly

renholder 8y ago

Most would even say statistically significant enough to order the planes grounded in their own countries...

buboard 8y ago

> Statistically, that's sufficiently improbable Is it?

kickopotomus 8y ago
Yes, it is. The 737 NG (700 series, 800 series, etc) has a hull loss rate of 0.27 per million departures[0]. I am having difficulty finding the exact number of departures for the MAX but 737s average about 3-5 departures per day[1]. Only 350 MAXs have been delivered and the first one was delivered on May 6, 2017[2] (676 days ago). So even being generous and supposing that all 350 aircraft were delivered exactly on May 6, 2017 and that each plane made 5 flights daily, that would be a total of 1,183,000 flights. Therefore the MAX line has a best-case hull loss rate of 1.69 per million departures. I.e. the MAX generation has a hull loss rate 6.25 times that of the NG line. [0]: https://en.wikipedia.org/wiki/Boeing_737#Accidents_and_incidents https://en.wikipedia.org/wiki/Boeing_737#Accidents_and_incid... [1]: https://www.researchgate.net/publication/274782362_Characterization_of_the_Frequency_and_Nature_of_Bleed_Air_Contamination_Events_in_Commercial_Aircraft https://www.researchgate.net/publication/274782362_Character... [2]: https://en.wikipedia.org/wiki/Boeing_737_MAX https://en.wikipedia.org/wiki/Boeing_737_MAX
- buboard 8y ago
  the question is if this difference is statistically significant
  - kickopotomus 8y ago
    You are taking a commercial flight. You have the choice between 2 different aircraft which are essentially identical but you are more than 50 times more likely to crash in one of them. Which do you take? EDIT: I have learned that I was far too generous with the flight numbers. The MAX series has only logged ~150K flights. Therefore it's hull loss rate is roughly 13.33 per million making it almost 50 times more dangerous than the NG line. Yes, the difference is statistically significant.

cesarb 8y ago

> Pretty sure the data is that two planes crashed in five months in perfect weather conditions Not only that, but the data we have so far from the second crash (ADS-B data showing irregular vertical speed, see https://www.flightradar24.com/blog/flightradar24-data-regarding-the-crash-of-ethiopian-airlines-flight-302/ https://www.flightradar24.com/blog/flightradar24-data-regard...) is consistent with both accidents having a similar cause. Grounding all airplanes from the same model until preliminary data from the (already recovered) flight recorders can confirm or discard that hypothesis is prudent.

Recurecur 8y ago
If it was a "similar cause", it is absolutely pilot error. The MCAS system, at fault in the first crash, may be disabled via a cockpit control. In other 737s, moving the stick was sufficient to disengage it. For some reason, this was changed in the Max, and you must use the other control. However, any competent pilot would know every control in the cockpit. The captain of the latest flight to crash allegedly had 8,000+ hours of flight time. If an aircraft begins behaving incorrectly, the first thing a flight crew should do is disable automation and try and fly it manually. That wasn't done if MCAS caused the crash. This was an emergency that developed over minutes, not seconds, and there's really no excuse.
- julianlam 8y ago
  Unless I am mistaken, the regular 737s do not have the MCAS installed,just the MAXs (https://theaircurrent.com/aviation-safety/what-is-the-boeing-737-max-maneuvering-characteristics-augmentation-system-mcas-jt610/ https://theaircurrent.com/aviation-safety/what-is-the-boeing...) Additionally it has been suggested that documentation for this physical switch is not well laid out or presented in the manual because Boeing was confident that it would simply stay out of the pilot's way during flight. Assuming pilot error would seem to be premature if these points are in fact true.
  - mjburgess 8y ago
    Either way "pilot error" is defined with reference to some "reasonable level" of competence with the aircraft. If multiple pilots are making the same error the issue is with the aircraft changes, not the "reasonable competence". Ie., its redesign hasn't been thought through properly