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It's hard to trust just a "software update" with your life. I don't believe what Boeing is allegedly trying to do to fix the MCAS problems is sufficient. If the

by ulfw 8y ago

It's hard to trust just a "software update" with your life. I don't believe what Boeing is allegedly trying to do to fix the MCAS problems is sufficient. If they don't read 3 angle of attack sensors, how is this 'software update' going to solve anything. And all they have is 2 sensors (only 1 of which is read now)

hasperdi 8y ago
If they have 2 AoA's and they disagree, they can indicate that with the light AoA disagree, disable MCAS and display on the CDU that MCAS is disabled. So the pilot knows what's happening and take corrective action.
- 7e 8y ago
  That light is an upgrade you need to pay for.
  - wyred 8y ago
    Is Boeing taking DLC advice from EA now?
  - markdown 8y ago
    Not any more. https://www.reuters.com/article/us-ethiopia-airplane/boeing-to-offer-safety-feature-as-standard-in-737-max-software-upgrade-sources-idUSKCN1R20CU https://www.reuters.com/article/us-ethiopia-airplane/boeing-...
- beefield 8y ago
  >So the pilot knows what's happening and take corrective action Except that now we have a plane that behaves differently compared to the plane the pilot actually is trained for (the whole reason to implement MCAS in the first place). So now the plane comes down because it stalls where it should not according to the training of the pilot. Gee, makes me confident to fly...
  - VBprogrammer 8y ago
    Apologies, I keep trying to quash this one but it keeps reappearing. The reason MCAS is needed is because the engine nacelle generates lift at high angles of attack. This meant that there was a lack of positive control required to increase angle of attack. I understand this as if you need to pull with 10KG of force to get a 10 degree angle of attack, then you need to pull with at least 20kg to get to a 20 degree angle of attack. I'm not going to claim that's 100% accurate but I believe it's close enough. This is a generic requirement of part 25. So had the 737 Max been a clean sheet design it would have been a requirement. It's not just a compatibility layer to make it behave the same as old aircraft. It's a fix to make it meet the requirements of certification. Training only came into it at the point that Boeing declined to add it to the difference training, charitably, because they felt the system was covered by existing procedures or, less charitably, because they wanted to downplay any differences to make the aircraft more appealing.
    - beefield 8y ago
      No need to apologize, I am happy to be corrected. But that still means that if you disengage MCAS, you have a plane that flies out of certification specs (and by extension, out of the training), then?
      - VBprogrammer 8y ago
        Absolutely. I feel that the motives which led to the situation are quite important though in the greater scheme of things. To phrase it another way, without MCAS the 737 Max didn't meant the requirements of certification and so wouldn't have gone into production. The alternative wasn't to train pilots into how to handle the new stall characteristics. Of course, the region of flight that MCAS was intended to activate in is also a bit of an edge case. Without MCAS we may have seen an aircraft flown into a stall, most likely around a critical phase of flight (landing or a go-around), but that would have involved a pilot ignoring numerous warnings (stick shaker activation, 'stall stall' oral alerts etc) and you'd be better categorised as pilot error than directly related to the handling characteristics. Unfortunately, due to a terrible system design, MCAS appears to be activating in regions of flight outside of the design intent and with greater authority than it should ever have been given.
ReptileMan 8y ago
Honestly what worries me more is what else is lurking in the plane that we don't know about. MCAS will be fixed and done right. But what other systems the same mindset have enchanced.
nutjob2 8y ago
In case of MCAS malfunction, the software update is going to flash an orange light marked "oh shit."
upofadown 8y ago
The entire concept is nuts. You can't fix a primary control characteristic with a slow trim system driven by a screw jack. If Boeing wants to fix their wonky flight characteristic with software then great, but they actually have to do that.
- VBprogrammer 8y ago
  I think to understand the thought process that lead to this system being implemented you have to understand, or at least see, the layers of fixes and kludges the 737 flight control system has had added over the years. I came across this last night, it made my head hurt: https://www.satcom.guru/2018/11/stabilizer-trim.html?m=1 https://www.satcom.guru/2018/11/stabilizer-trim.html?m=1

by ulfw 8y ago

hasperdi 8y ago

If they have 2 AoA's and they disagree, they can indicate that with the light AoA disagree, disable MCAS and display on the CDU that MCAS is disabled. So the pilot knows what's happening and take corrective action.

7e 8y ago
That light is an upgrade you need to pay for.
- wyred 8y ago
  Is Boeing taking DLC advice from EA now?
- markdown 8y ago
  Not any more. https://www.reuters.com/article/us-ethiopia-airplane/boeing-to-offer-safety-feature-as-standard-in-737-max-software-upgrade-sources-idUSKCN1R20CU https://www.reuters.com/article/us-ethiopia-airplane/boeing-...
beefield 8y ago
>So the pilot knows what's happening and take corrective action Except that now we have a plane that behaves differently compared to the plane the pilot actually is trained for (the whole reason to implement MCAS in the first place). So now the plane comes down because it stalls where it should not according to the training of the pilot. Gee, makes me confident to fly...
- VBprogrammer 8y ago
  Apologies, I keep trying to quash this one but it keeps reappearing. The reason MCAS is needed is because the engine nacelle generates lift at high angles of attack. This meant that there was a lack of positive control required to increase angle of attack. I understand this as if you need to pull with 10KG of force to get a 10 degree angle of attack, then you need to pull with at least 20kg to get to a 20 degree angle of attack. I'm not going to claim that's 100% accurate but I believe it's close enough. This is a generic requirement of part 25. So had the 737 Max been a clean sheet design it would have been a requirement. It's not just a compatibility layer to make it behave the same as old aircraft. It's a fix to make it meet the requirements of certification. Training only came into it at the point that Boeing declined to add it to the difference training, charitably, because they felt the system was covered by existing procedures or, less charitably, because they wanted to downplay any differences to make the aircraft more appealing.
  - beefield 8y ago
    No need to apologize, I am happy to be corrected. But that still means that if you disengage MCAS, you have a plane that flies out of certification specs (and by extension, out of the training), then?
    - VBprogrammer 8y ago
      Absolutely. I feel that the motives which led to the situation are quite important though in the greater scheme of things. To phrase it another way, without MCAS the 737 Max didn't meant the requirements of certification and so wouldn't have gone into production. The alternative wasn't to train pilots into how to handle the new stall characteristics. Of course, the region of flight that MCAS was intended to activate in is also a bit of an edge case. Without MCAS we may have seen an aircraft flown into a stall, most likely around a critical phase of flight (landing or a go-around), but that would have involved a pilot ignoring numerous warnings (stick shaker activation, 'stall stall' oral alerts etc) and you'd be better categorised as pilot error than directly related to the handling characteristics. Unfortunately, due to a terrible system design, MCAS appears to be activating in regions of flight outside of the design intent and with greater authority than it should ever have been given.

ReptileMan 8y ago

Honestly what worries me more is what else is lurking in the plane that we don't know about. MCAS will be fixed and done right. But what other systems the same mindset have enchanced.

nutjob2 8y ago

In case of MCAS malfunction, the software update is going to flash an orange light marked "oh shit."

upofadown 8y ago

The entire concept is nuts. You can't fix a primary control characteristic with a slow trim system driven by a screw jack. If Boeing wants to fix their wonky flight characteristic with software then great, but they actually have to do that.

VBprogrammer 8y ago
I think to understand the thought process that lead to this system being implemented you have to understand, or at least see, the layers of fixes and kludges the 737 flight control system has had added over the years. I came across this last night, it made my head hurt: https://www.satcom.guru/2018/11/stabilizer-trim.html?m=1 https://www.satcom.guru/2018/11/stabilizer-trim.html?m=1