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Are AOA sensors really so prone to failure that they caused the downing of two airplanes?
by sixothree 8y ago
Are AOA sensors really so prone to failure that they caused the downing of two airplanes?
- Xixi 8y agoLike all sensors out there in the atmosphere, icing is an issue. So not only are they error prone, but failures are sometimes not independent. Airbus planes from the A320 family have three such sensors, but it so happened that on November 5th, 2014, an A321 had two sensors freeze in the wrong position during flight. Two sensors against one win, so the flight envelope protection system kicked in and the aircraft started to nose dive. It lost 4000 feet in altitude before the crew regained control... Details of the flight if you want to do some research: Lufthansa Airbus A321-200, registration D-AIDP, performing flight LH-1829 from Bilbao, SP (Spain) to Munich (Germany) on November 5th, 2014.
- ams6110 8y agoNormally no, from what I have read they are very reliable. And the sensors are the same ones used on all 737s. So it seems that there is some other problem with the MAX that is leading to the a false "nose high" indication.
- linuxftw 8y agoI wouldn't think so. My personal theory is AoA is sending valid data to one of the flight computers, that flight computer is sending invalid data to the MCAS, or the MCAS has a software problem. I suspect AoA is sending signed data, computer expects unsigned data, or possibly LSB/MSB conversion problem. Or it could just be faulty logic somewhere.
- salawat 8y agoThe sensors on Lion Air were 10+ degrees out of calibratiom IIRC. Critical AoA is somewhere in the realm of 17 to 20 degrees. That doesn't leave much room for where MCAS wouldn't be a problem. Also, AoA sensors are not normally safety critical. The MAX is the first 737 airframe for which this is the case.