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> They're already changing it to take data from both sensors, and there's been talk of requiring a third for voting logic. So the "real fix" is treating a safet

> They're already changing it to take data from both sensors, and there's been talk of requiring a third for voting logic. So the "real fix" is treating a safety critical sensor as a safety critical sensor. Not according to the press release. https://boeing.mediaroom.com/news-releases-statements?item=130402 https://boeing.mediaroom.com/news-releases-statements?item=1... Interconnects like that are quite unusual. For example the autopilot is typically driven from either the same data source as pilot or the co-pilots system. There are some exceptions, for example in full auto-land mode both systems are engaged. But that really is an exception, only a fraction of the worlds runways have CATIII certification and they require special ground operations to support them. There are procedures designed to ensure the systems agree on certain critical data, for example the 'pilot not flying' will usually call out 80 knots and cross check that the speed agrees between both sides.

Someone1234 8y ago
> Not according to the press release. Questionable conclusion, the press release doesn't go into details either way. To quote this NYT article: > Boeing is updating the software to require data from both sensors for the system to kick in, according to pilots at several major airlines and two lawmakers briefed on the matter. https://www.nytimes.com/2019/03/15/business/boeing-ethiopian-crash.html https://www.nytimes.com/2019/03/15/business/boeing-ethiopian... > Interconnects like that are quite unusual. Not in aviation, for example the Airbus A330 has triple redundant Pitot tubes, the B737CL (Boeing 737 "classic") has four, the B737NG has three (737 Next Gen), etc. So this "quite unusual" system appears on the very airplane we're discussing for the Pitot-Static System, a safety critical sensor.
- VBprogrammer 8y ago
  On the 737NG 3 pitot tubes are pilot, co-pilot and the elevator control feel input. They aren't averaged, voted upon or compared in any way. I don't know much about the Airbus pitot system, except one ended up at the bottom of the Atlantic due, in part, to a frozen pitot tube.
  - Someone1234 8y ago
    > On the 737NG 3 pitot tubes are pilot, co-pilot and the elevator control feel input. They aren't averaged, voted upon or compared in any way. You're mistaken. To quote Boeing themselves: > The most modern systems today use an air data inertial reference unit (ADIRU), which incorporates the best information from three pitot and static sources and provides a single set of data to both pilots. An ADIRU receives information from air data modules, which are located close to the pressure sources. This is used on, at least the Boeing 757, 737 and Airbus A319, A320, A321, A330, & A340.
    - VBprogrammer 8y ago
      I believe your source is unreliable. For example read this report: https://assets.publishing.service.gov.uk/media/578df0f5e5274a0da3000176/Boeing_737-86N_EI-FHG_08-16.pdf https://assets.publishing.service.gov.uk/media/578df0f5e5274...
      - Someone1234 8y ago
        This is the second time you've linked to something without having read it (or understood it) first. And your own link disputes your point: > The Boeing 737 NG series are fitted with pitot probes mounted on the left and right of the fuselage just aft of the radome. The aircraft are also fitted with an auxiliary probe on the right side of the forward fuselage and two ‘elevator pitot probes’ on the fin. The triple redundant system initiated a "IAS and ALT disagree master caution." Which is exactly what a safety critical sensor is meant to do. As an aside I'm done conversing with you on this topic. You keep on saying incorrect things, link to bad citations that don't support your previous statements, and when that fails moving the goalposts to something else entirely. It isn't a good faith way to have a discussion. Keep in mind half a dozen posts ago you claimed no aircraft used triple redundancy or voting logic (which the 737 does, as I've shown and your own citation shows). Now your argument has shifted to some kind of pedantic one about which exact systems consume what data or similar.
        VBprogrammer 8y ago
mannykannot 8y ago
According to Dominic Gates, with MCAS classified by Boeing as having a 'hazardous' risk level, it should not have been dependent on a single sensor. 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...
- VBprogrammer 8y ago
  Don't get me wrong. The system as designed is completely reprehensible and most likely initiated a chain of events which lead to the dealths of more than 300 people. However, the point I started with is displaying the AoA in the cockpit is unlikely to have helped any of that. It's not really a safety feature except in quite specific scenarios (where the pilot is trying to extract maximum performance from an aircraft). The other point I was making is that it's unlikely that they'll fit an extra sensor or cross connect the inputs. There are few systems which receive data from both pilots and co-pilots sources.
  - mannykannot 8y ago
    I was just wondering how Boeing could avoid the single-source prohibition that Gates writes about, but on reflection, I suppose it could take MCAS out of the hazardous class, and maybe limiting the degree to which it can change the trim will do that.

Someone1234 8y ago

> Not according to the press release. Questionable conclusion, the press release doesn't go into details either way. To quote this NYT article: > Boeing is updating the software to require data from both sensors for the system to kick in, according to pilots at several major airlines and two lawmakers briefed on the matter. https://www.nytimes.com/2019/03/15/business/boeing-ethiopian-crash.html https://www.nytimes.com/2019/03/15/business/boeing-ethiopian... > Interconnects like that are quite unusual. Not in aviation, for example the Airbus A330 has triple redundant Pitot tubes, the B737CL (Boeing 737 "classic") has four, the B737NG has three (737 Next Gen), etc. So this "quite unusual" system appears on the very airplane we're discussing for the Pitot-Static System, a safety critical sensor.

VBprogrammer 8y ago
On the 737NG 3 pitot tubes are pilot, co-pilot and the elevator control feel input. They aren't averaged, voted upon or compared in any way. I don't know much about the Airbus pitot system, except one ended up at the bottom of the Atlantic due, in part, to a frozen pitot tube.
- Someone1234 8y ago
  > On the 737NG 3 pitot tubes are pilot, co-pilot and the elevator control feel input. They aren't averaged, voted upon or compared in any way. You're mistaken. To quote Boeing themselves: > The most modern systems today use an air data inertial reference unit (ADIRU), which incorporates the best information from three pitot and static sources and provides a single set of data to both pilots. An ADIRU receives information from air data modules, which are located close to the pressure sources. This is used on, at least the Boeing 757, 737 and Airbus A319, A320, A321, A330, & A340.
  - VBprogrammer 8y ago
    I believe your source is unreliable. For example read this report: https://assets.publishing.service.gov.uk/media/578df0f5e5274a0da3000176/Boeing_737-86N_EI-FHG_08-16.pdf https://assets.publishing.service.gov.uk/media/578df0f5e5274...
    - Someone1234 8y ago
      This is the second time you've linked to something without having read it (or understood it) first. And your own link disputes your point: > The Boeing 737 NG series are fitted with pitot probes mounted on the left and right of the fuselage just aft of the radome. The aircraft are also fitted with an auxiliary probe on the right side of the forward fuselage and two ‘elevator pitot probes’ on the fin. The triple redundant system initiated a "IAS and ALT disagree master caution." Which is exactly what a safety critical sensor is meant to do. As an aside I'm done conversing with you on this topic. You keep on saying incorrect things, link to bad citations that don't support your previous statements, and when that fails moving the goalposts to something else entirely. It isn't a good faith way to have a discussion. Keep in mind half a dozen posts ago you claimed no aircraft used triple redundancy or voting logic (which the 737 does, as I've shown and your own citation shows). Now your argument has shifted to some kind of pedantic one about which exact systems consume what data or similar.
      - VBprogrammer 8y ago

mannykannot 8y ago

According to Dominic Gates, with MCAS classified by Boeing as having a 'hazardous' risk level, it should not have been dependent on a single sensor. 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...

VBprogrammer 8y ago
Don't get me wrong. The system as designed is completely reprehensible and most likely initiated a chain of events which lead to the dealths of more than 300 people. However, the point I started with is displaying the AoA in the cockpit is unlikely to have helped any of that. It's not really a safety feature except in quite specific scenarios (where the pilot is trying to extract maximum performance from an aircraft). The other point I was making is that it's unlikely that they'll fit an extra sensor or cross connect the inputs. There are few systems which receive data from both pilots and co-pilots sources.
- mannykannot 8y ago
  I was just wondering how Boeing could avoid the single-source prohibition that Gates writes about, but on reflection, I suppose it could take MCAS out of the hazardous class, and maybe limiting the degree to which it can change the trim will do that.