3 ms·

Looking at one component and saying it’s safe (qualified with ‘if you know what’s going on’) misses the point. In fact it’s an engineering style response becaus

by jarym 8y ago

Looking at one component and saying it’s safe (qualified with ‘if you know what’s going on’) misses the point. In fact it’s an engineering style response because it shows some myopia. Safety in an aircraft means getting passengers to their destination without injury or loss of life. Boeing failed here - blame lack of training, single sensor dependence or software if you like but there was certainly a failure. Now no one really cares if MCAS is problematic - any solution needs to resolve the underlying fault.

salawat 8y ago
The underlying fault unfortunately isn't 100% a Boeing problem. There are airworthyness regulations that specify how a passenger plane is to behave near stall that have had a precedent set where non-compliance can be remedied through flight envelope driven interlocks. (See stick-pushers and other piloting aids). Engineeringwise, the airframe was still not compliant; the airframe would still manifest aberrant behavior, but the action on the controls combined with a type certified pilot was considered enough to mitigate the problematic aerodynamics. This practice, fortunately or unfortunately depending on who you ask, effectively normalized deviance, and short-circuited the protection offered by that airworthyness regulation. It went from being clearly spelled out to "or equivalent level of safety" which opens the door to all sorts of workarounds. The alpha vanes need to be a high-priority maintenance item. They may also need to be redesigned/augmented such that they can be hardened against typical failure states, or subjected to in-flight remediation/diagnostics and graceful failover. That isn't easy from my understanding. Doing something like hardening vs. freezing would require some form of heating element, which would potentially effect the calibration of the sensor while active, and increase maintenance complexity. Adding some sort of self contained calibration unit to the sensor could work too, however, the more complexity built into that, the more costly it becomes. There is a point of diminishing returns, and I do think the plane can be rendered safe with MCAS and pilot retraining. Unfortunately, that will still come bundled with an aircraft losing its airworthyness rating on Stab Trim cutout.

by jarym 8y ago

salawat 8y ago

The underlying fault unfortunately isn't 100% a Boeing problem. There are airworthyness regulations that specify how a passenger plane is to behave near stall that have had a precedent set where non-compliance can be remedied through flight envelope driven interlocks. (See stick-pushers and other piloting aids). Engineeringwise, the airframe was still not compliant; the airframe would still manifest aberrant behavior, but the action on the controls combined with a type certified pilot was considered enough to mitigate the problematic aerodynamics. This practice, fortunately or unfortunately depending on who you ask, effectively normalized deviance, and short-circuited the protection offered by that airworthyness regulation. It went from being clearly spelled out to "or equivalent level of safety" which opens the door to all sorts of workarounds. The alpha vanes need to be a high-priority maintenance item. They may also need to be redesigned/augmented such that they can be hardened against typical failure states, or subjected to in-flight remediation/diagnostics and graceful failover. That isn't easy from my understanding. Doing something like hardening vs. freezing would require some form of heating element, which would potentially effect the calibration of the sensor while active, and increase maintenance complexity. Adding some sort of self contained calibration unit to the sensor could work too, however, the more complexity built into that, the more costly it becomes. There is a point of diminishing returns, and I do think the plane can be rendered safe with MCAS and pilot retraining. Unfortunately, that will still come bundled with an aircraft losing its airworthyness rating on Stab Trim cutout.