4 ms·

I'm not downvoting you, but I think this is a kind of problem that seems solvable on the surface, but is very, very difficult to get right. You will always have

by gnaffle 15y ago

I'm not downvoting you, but I think this is a kind of problem that seems solvable on the surface, but is very, very difficult to get right. You will always have situations where all speed indicators fail in a similar way leading the software to believe that the speed is correct. With all the erring on the side of caution that aircraft makes have used, we've had a couple of cases where the software "decided" something and caused incidents. Studies in N-version programming (such as used in Airbus planes) show that software written by different teams often fail in the same corner cases (with differing outputs). Eventually you might have software with "situational awareness" that can be trusted to make fewer mistakes than humans, but we're not there yet.

apaprocki 15y ago
I agree it will take a long time to develop automated systems that can be trusted. It took 26 years for tech to develop from the first ILS assisted passenger landing to the first fully automated ILS landing. If you were to take this specific speed sensor issue, I'm more concerned there aren't different types of systems being used to try to cross-validate the numbers. The pitot-static system has its own backup on the plane, but if there is an inherent weakness of that particular system (e.g. ice), there is no other way to measure speed that is not susceptible to icing. Surely that particular problem is within our reach, no?
- gnaffle 15y ago
  To measure airspeed I guess something has to have air flowing through it or past it, and that something would be susceptible to icing. That said, current pitot have very good ice protection, and AF447 was an extreme example with a known problematic type that Air France were in the process of exchanging. Perhaps GPS ground speed data with previous wind estimates could at least help with establishing that "something must be wrong with the airspeeds".
  - apaprocki 15y ago
    That is what this captain suggests: http://travel.usatoday.com/experts/cox/story/2011/05/Ask-the-Captain-Questions-about-Air-France-flight-447/47447562/1 http://travel.usatoday.com/experts/cox/story/2011/05/Ask-the... Something scary from a Boeing pilot in the comments: Loss of all airspeed indications is not something we train for. It's always assumed in transport category aircraft that redundancies built in will always give us at least attitude, heading, and airspeed.
  - caf 15y ago
    There are meterological radars that use doppler shift to measure wind speed, I wonder if you could use the same basic idea to construct a radar airspeed indicator?

by gnaffle 15y ago

apaprocki 15y ago

I agree it will take a long time to develop automated systems that can be trusted. It took 26 years for tech to develop from the first ILS assisted passenger landing to the first fully automated ILS landing. If you were to take this specific speed sensor issue, I'm more concerned there aren't different types of systems being used to try to cross-validate the numbers. The pitot-static system has its own backup on the plane, but if there is an inherent weakness of that particular system (e.g. ice), there is no other way to measure speed that is not susceptible to icing. Surely that particular problem is within our reach, no?

gnaffle 15y ago
To measure airspeed I guess something has to have air flowing through it or past it, and that something would be susceptible to icing. That said, current pitot have very good ice protection, and AF447 was an extreme example with a known problematic type that Air France were in the process of exchanging. Perhaps GPS ground speed data with previous wind estimates could at least help with establishing that "something must be wrong with the airspeeds".
- apaprocki 15y ago
  That is what this captain suggests: http://travel.usatoday.com/experts/cox/story/2011/05/Ask-the-Captain-Questions-about-Air-France-flight-447/47447562/1 http://travel.usatoday.com/experts/cox/story/2011/05/Ask-the... Something scary from a Boeing pilot in the comments: Loss of all airspeed indications is not something we train for. It's always assumed in transport category aircraft that redundancies built in will always give us at least attitude, heading, and airspeed.
- caf 15y ago
  There are meterological radars that use doppler shift to measure wind speed, I wonder if you could use the same basic idea to construct a radar airspeed indicator?