6 ms·

Instrumentation on an aircraft is usually designed with a pilot and copilot set. Everything down to the pitot tubes which feed the information is unique to that

Instrumentation on an aircraft is usually designed with a pilot and copilot set. Everything down to the pitot tubes which feed the information is unique to that side of the aircraft. This harks back to the day when it was the only sensible solution when your guages are actually just directly reading airpressure differences. Clearly these signals can be cross connected, because that's the solution Boeing are testing at the moment, but it's outside the normal design of aircraft systems.

myth2018 8y ago
Uhm.. I don't know.. I'm aware this is the case of airspeed indicators and many others, but, for instance, the autopilot is fed with readings of Pitot tubes from both sides and it disengages when the sensors disagree beyond sensible thresholds. Besides, such issue is brought clearly to the knowledge of pilots. In the MCAS case, however, we are speaking about a computer which not only interferes in the flight controls, but also does that in a way impossible to override and it's too difficult for the pilots to spot the root cause.
- VBprogrammer 8y ago
  To be clear, I think MCAS was a massive engineering failure for Boeing, I'm just pointing out why I think they didn't automatically say "hey, we've got two sensors, lets compare the readings before we act on it". However, for the autopilot example, I don't think you are quite right. Typically there are multiple autopilots (2 or 3 is quite common), and each is driven by a different set of flight data. In some scenarios multiple autopilots are engaged at same time, for example during CATIII auto-landings but as far as I'm aware that is the exception rather than the rule. It's true that the autopilot may disconnect if there is a warning like 'IAS Disagree', I suspect this is driven by a separate monitoring process though, rather than being an integral part of the system.

myth2018 8y ago

Uhm.. I don't know.. I'm aware this is the case of airspeed indicators and many others, but, for instance, the autopilot is fed with readings of Pitot tubes from both sides and it disengages when the sensors disagree beyond sensible thresholds. Besides, such issue is brought clearly to the knowledge of pilots. In the MCAS case, however, we are speaking about a computer which not only interferes in the flight controls, but also does that in a way impossible to override and it's too difficult for the pilots to spot the root cause.

VBprogrammer 8y ago
To be clear, I think MCAS was a massive engineering failure for Boeing, I'm just pointing out why I think they didn't automatically say "hey, we've got two sensors, lets compare the readings before we act on it". However, for the autopilot example, I don't think you are quite right. Typically there are multiple autopilots (2 or 3 is quite common), and each is driven by a different set of flight data. In some scenarios multiple autopilots are engaged at same time, for example during CATIII auto-landings but as far as I'm aware that is the exception rather than the rule. It's true that the autopilot may disconnect if there is a warning like 'IAS Disagree', I suspect this is driven by a separate monitoring process though, rather than being an integral part of the system.