39 ms·

To be fair, I don't think the "disagree" light would've helped those pilots any. Knowing that the AoA sensors disagreed isn't going to help them troubleshoot a

To be fair, I don't think the "disagree" light would've helped those pilots any. Knowing that the AoA sensors disagreed isn't going to help them troubleshoot a system they are not aware exists. It's just one more warning to troubleshoot while fighting the aircraft. If anything, it's MCAS that needs to be heeding the AoA readings disagreement. Instead it's more than happy to only rely on the reading of one of the sensors.

lallysingh 8y ago
Or, you know, train the pilots. Boeing is trying to get the blame off their backs. It can go to the airlines now.
- Someone1234 8y ago
  MCAS wasn't in the training materials provided to airlines. Even some US pilots have complained that they had no knowledge of it before the Lion Air crash.
  - lallysingh 8y ago
    I didn't know that the materials weren't provided. How do they add a new system and not provide training materials?!?!
    - deleted 8y ago
      [deleted]
    - danso 8y ago
      Because part of the advertised appeal of the MAX was that it would not require new training, despite a different aerodynamic profile: > Since MCAS was supposed to activate only in extreme circumstances far outside the normal flight envelope, Boeing decided that 737 pilots needed no extra training on the system — and indeed that they didn’t even need to know about it. It was not mentioned in their flight manuals. > That stance allowed the new jet to earn a common “type rating” with existing 737 models, allowing airlines to minimize training of pilots moving to the MAX. https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/ https://www.seattletimes.com/business/boeing-aerospace/faile...
- ajnin 8y ago
  The whole point of that system is that it would alter the plane controls so that it behaves the same as the older models, so that pilots wouldn't need to be retrained. It was one of the main selling points of that aircraft.
matt4077 8y ago
I seem to remember reading about an incident recently where pilots noticed divergent sensor reading and aborted take-off. It would seem that AoA disagreement would be the very first symptom of the failure that lead to these crashes. Since pilots are likely not to immediately notice this (hence the indicator), this feature may well have given them additional time to sort out a response. Depending on how this failure progressed, it may have even been discovered on previous flights or before take-off.
- Someone1234 8y ago
  That's a really good point. The AoA disagree could go off as soon as the nose is lifted, which still may give pilots just enough time to abort take-off or immediately request landing.
  - VBprogrammer 8y ago
    > which still may give pilots just enough time to abort take-off Airliners are committed to takeoff by the point of rotation. Typical ops manuals would abort for any warning before 80kts, at a speed known as V1 they are committed (even in case of engine failure) this typically occurs 10-20kts before rotation speed where the pilot initiates lifting the nose.
- stanski 8y ago
  Given that the warning is optional, it would suggest that the AoA sensors are not components that are critical to a safe flight. Well... or so they thought anyway. It's questionable if most pilots would abort a take off because of an AoA sensor discrepancy, especially if they didn't know it controls MCAS or that MCAS exists in the first place. But yeah - good point about it potentially triggering further diagnostics prior to the flight altogether.
ajnin 8y ago
There's not only a light, the article mentions that the MCAS will also take readings from both sensors and be disabled if they disagree too much.
- tyingq 8y ago
  That's not how it currently works, but could be part of a proposed fix.
pegasus 8y ago
My understanding is there's a good chance that those sensors were malfunctioning for a while before the day of the crash (during the post-crash investigation they found that previous flights were showing dubious readings). In which case, a disagreement alert could have potentially saved all those lives.

lallysingh 8y ago

Or, you know, train the pilots. Boeing is trying to get the blame off their backs. It can go to the airlines now.

Someone1234 8y ago
MCAS wasn't in the training materials provided to airlines. Even some US pilots have complained that they had no knowledge of it before the Lion Air crash.
- lallysingh 8y ago
  I didn't know that the materials weren't provided. How do they add a new system and not provide training materials?!?!
  - deleted 8y ago
    [deleted]
  - danso 8y ago
    Because part of the advertised appeal of the MAX was that it would not require new training, despite a different aerodynamic profile: > Since MCAS was supposed to activate only in extreme circumstances far outside the normal flight envelope, Boeing decided that 737 pilots needed no extra training on the system — and indeed that they didn’t even need to know about it. It was not mentioned in their flight manuals. > That stance allowed the new jet to earn a common “type rating” with existing 737 models, allowing airlines to minimize training of pilots moving to the MAX. https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/ https://www.seattletimes.com/business/boeing-aerospace/faile...
ajnin 8y ago
The whole point of that system is that it would alter the plane controls so that it behaves the same as the older models, so that pilots wouldn't need to be retrained. It was one of the main selling points of that aircraft.

matt4077 8y ago

I seem to remember reading about an incident recently where pilots noticed divergent sensor reading and aborted take-off. It would seem that AoA disagreement would be the very first symptom of the failure that lead to these crashes. Since pilots are likely not to immediately notice this (hence the indicator), this feature may well have given them additional time to sort out a response. Depending on how this failure progressed, it may have even been discovered on previous flights or before take-off.

Someone1234 8y ago
That's a really good point. The AoA disagree could go off as soon as the nose is lifted, which still may give pilots just enough time to abort take-off or immediately request landing.
- VBprogrammer 8y ago
  > which still may give pilots just enough time to abort take-off Airliners are committed to takeoff by the point of rotation. Typical ops manuals would abort for any warning before 80kts, at a speed known as V1 they are committed (even in case of engine failure) this typically occurs 10-20kts before rotation speed where the pilot initiates lifting the nose.
stanski 8y ago
Given that the warning is optional, it would suggest that the AoA sensors are not components that are critical to a safe flight. Well... or so they thought anyway. It's questionable if most pilots would abort a take off because of an AoA sensor discrepancy, especially if they didn't know it controls MCAS or that MCAS exists in the first place. But yeah - good point about it potentially triggering further diagnostics prior to the flight altogether.

ajnin 8y ago

There's not only a light, the article mentions that the MCAS will also take readings from both sensors and be disabled if they disagree too much.

tyingq 8y ago
That's not how it currently works, but could be part of a proposed fix.

pegasus 8y ago

My understanding is there's a good chance that those sensors were malfunctioning for a while before the day of the crash (during the post-crash investigation they found that previous flights were showing dubious readings). In which case, a disagreement alert could have potentially saved all those lives.