3 ms·

It needs three AoA sensors, like Airbus planes have. Two isn't enough for such a safety-critical system. When one malfunctions, you still need to know what the

It needs three AoA sensors, like Airbus planes have. Two isn't enough for such a safety-critical system. When one malfunctions, you still need to know what the correct value is.

konspence 7y ago
Three AoA sensors is still not enough to generate a confident consensus to allow an autopilot system capable of crashing the plane to function On Lufthansa 1829, two of the three AOA sensors on an A321 erroneously agreed, causing a system similar to MCAS to kick in[1] The sensors can fail due to being frozen, or also be damaged by birds traveling in flocks [1] Third bullet point under the A321 heading: https://en.wikipedia.org/wiki/List_of_accidents_and_incidents_involving_the_Airbus_A320_family#A321 https://en.wikipedia.org/wiki/List_of_accidents_and_incident...
- gomijacogeo 7y ago
  The thing is 1829 didn't crash, the pilots got an alert, figured out the problem, took manual control, and flew the plane. Defense in layers. It would be ideal to use different technologies for the AoA sensors to help minimize common-mode failures. Integration and crosschecking against other systems (IMU, radar altimiter, DGPS, an open-loop model of the plane based on engine settings and control surface positions, etc) could give the pilots and flight envelope protection systems a better understanding of their situation. Also, the signature of a failed/frozen vane-type AoA sensor is pretty obvious and I'm surprised the software doesn't take that into account. Good writeup on LH-1829: http://avherald.com/h?article=47d74074 http://avherald.com/h?article=47d74074
gomijacogeo 7y ago
It depends on what the flight characteristics of the Max8 really are - something I've not seen a good writeup on. If the plane really can get away from pilots, then you're likely right (i.e. it really needs a proper flight envelope protection system - and the Max8 is dead). If it's just that the plane flies differently from other 737's, then 2 + subtype training is probably sufficient.

It needs three AoA sensors, like Airbus planes have. Two isn't enough for such a safety-critical system. When one malfunctions, you still need to know what the correct value is.

konspence 7y ago

Three AoA sensors is still not enough to generate a confident consensus to allow an autopilot system capable of crashing the plane to function On Lufthansa 1829, two of the three AOA sensors on an A321 erroneously agreed, causing a system similar to MCAS to kick in[1] The sensors can fail due to being frozen, or also be damaged by birds traveling in flocks [1] Third bullet point under the A321 heading: https://en.wikipedia.org/wiki/List_of_accidents_and_incidents_involving_the_Airbus_A320_family#A321 https://en.wikipedia.org/wiki/List_of_accidents_and_incident...

gomijacogeo 7y ago
The thing is 1829 didn't crash, the pilots got an alert, figured out the problem, took manual control, and flew the plane. Defense in layers. It would be ideal to use different technologies for the AoA sensors to help minimize common-mode failures. Integration and crosschecking against other systems (IMU, radar altimiter, DGPS, an open-loop model of the plane based on engine settings and control surface positions, etc) could give the pilots and flight envelope protection systems a better understanding of their situation. Also, the signature of a failed/frozen vane-type AoA sensor is pretty obvious and I'm surprised the software doesn't take that into account. Good writeup on LH-1829: http://avherald.com/h?article=47d74074 http://avherald.com/h?article=47d74074

gomijacogeo 7y ago

It depends on what the flight characteristics of the Max8 really are - something I've not seen a good writeup on. If the plane really can get away from pilots, then you're likely right (i.e. it really needs a proper flight envelope protection system - and the Max8 is dead). If it's just that the plane flies differently from other 737's, then 2 + subtype training is probably sufficient.