4 ms·

It doesn't really matter if the airspeed is slightly incorrect. What matters is that the aircraft is telling you the airspeed is unreliable, because that distr

It doesn't really matter if the airspeed is slightly incorrect. What matters is that the aircraft is telling you the airspeed is unreliable, because that distracts from the actual problem you face. https://aviationweek.com/awincommercial/safety-official-lion-air-737-had-unreliable-airspeed-readings https://aviationweek.com/awincommercial/safety-official-lion...

sokoloff 8y ago
Ah. Thanks! I misread your previous as "unreliable (airspeed indication)" rather than as "(unreliable airspeed) indication".
mannykannot 8y ago
We can see from the data that the left stick shaker is running almost continuously, while the right one is not. That is nominally saying that the airspeed is dangerously low. I assume that asymmetry is also a consequence of the faulty sensor, and I wonder if pilots are taught that this asymmetric stick-shaker response is a sign of equipment failure (and would it be clear to the pilots that this asymmetry is happening?) Of course, if you don't know about MCAS, you won't know that it could also be messing with the trim. While trim runaway, at least when considered in isolation, seems straightforward to detect and stop, the pilots were trying to make sense of a set of not-clearly-related symptoms. I am curious as to how the pilot training and certification requirements are presented - for example, are they required to demonstrate handling a trim runaway, or to recognize and handle the various consequences of a given system component failure? It might be argued that there are vastly too many variations of the latter to be covered, but if so, that might be indicative of a broader issue, as real problems don't always present themselves like an exercise in responding to one specific symptom.
- sokoloff 8y ago
  The stick shaker is driven from the angle-of-attack system, not airspeed, because that's the least difference between physical world (the wing stalls at an angle of attack, not an airspeed). In this case, the differential stick shaker may have provided an additional clue to the crew. While I'm generally critical of the crew training and performance, particularly the Ethiopian Air crew, even I can't reasonably hang missing the differential shaker indication on the crew. Your last paragraph raises an excellent point, and one which points to the need to put fully trained, but equally importantly fully seasoned, crews into large transport aircraft in passenger service. (some) People in aviation cried about the implementation of the 1500 hour requirement to get an ATP (Airline Transport Pilot) certificate after the Colgan Air crash in Buffalo. To me, these two accidents [and others outside of US/Western European carriers] show the wisdom in that decision, especially the most recent one. I have right on either side of 1500 hours (all but 20 in piston airplanes, about 4 hours in 737 level D sim) over a 21 year span. If I went to and passed a type rating school now, I'd hold myself barely qualified to do the walkaround when it's raining, sit right seat, run the radios, carry the captain's bag, and eat whichever meal she didn't want. 350 hours is not an appropriate time (IMO) to have a front-seat position in a transport jet flying passengers.

sokoloff 8y ago

Ah. Thanks! I misread your previous as "unreliable (airspeed indication)" rather than as "(unreliable airspeed) indication".

mannykannot 8y ago

We can see from the data that the left stick shaker is running almost continuously, while the right one is not. That is nominally saying that the airspeed is dangerously low. I assume that asymmetry is also a consequence of the faulty sensor, and I wonder if pilots are taught that this asymmetric stick-shaker response is a sign of equipment failure (and would it be clear to the pilots that this asymmetry is happening?) Of course, if you don't know about MCAS, you won't know that it could also be messing with the trim. While trim runaway, at least when considered in isolation, seems straightforward to detect and stop, the pilots were trying to make sense of a set of not-clearly-related symptoms. I am curious as to how the pilot training and certification requirements are presented - for example, are they required to demonstrate handling a trim runaway, or to recognize and handle the various consequences of a given system component failure? It might be argued that there are vastly too many variations of the latter to be covered, but if so, that might be indicative of a broader issue, as real problems don't always present themselves like an exercise in responding to one specific symptom.

sokoloff 8y ago
The stick shaker is driven from the angle-of-attack system, not airspeed, because that's the least difference between physical world (the wing stalls at an angle of attack, not an airspeed). In this case, the differential stick shaker may have provided an additional clue to the crew. While I'm generally critical of the crew training and performance, particularly the Ethiopian Air crew, even I can't reasonably hang missing the differential shaker indication on the crew. Your last paragraph raises an excellent point, and one which points to the need to put fully trained, but equally importantly fully seasoned, crews into large transport aircraft in passenger service. (some) People in aviation cried about the implementation of the 1500 hour requirement to get an ATP (Airline Transport Pilot) certificate after the Colgan Air crash in Buffalo. To me, these two accidents [and others outside of US/Western European carriers] show the wisdom in that decision, especially the most recent one. I have right on either side of 1500 hours (all but 20 in piston airplanes, about 4 hours in 737 level D sim) over a 21 year span. If I went to and passed a type rating school now, I'd hold myself barely qualified to do the walkaround when it's raining, sit right seat, run the radios, carry the captain's bag, and eat whichever meal she didn't want. 350 hours is not an appropriate time (IMO) to have a front-seat position in a transport jet flying passengers.