Originally Posted by
bsieker
infrequentflyer789, TTail,
thanks a lot for your input. Food for thought.
It would appear that, even without MCAS, there is more to automated trimming on the 737 (even pre-MAX) than meets the eye. I'm quite experienced in reading and interpreting FCOMs and related material, but sometimes this feels like deliberate obfuscation.
I have a feeling Boeing's idea that the pilot has to save the day will fall short of regulators' approval. They can no longer maintain after two accidents (where in the second one the crew almost certainly knew about the first) that any pilot "without exceptional skill" (which is the regulatory requirement, and, if you think about it, is a lot less than "average") will be able to handle it.
Bernd
Dear Bernd,
Have a look at this video of American Airlines pilots talking about the MCAS system after experiencing it at Boeing's 737 MAX simulator:
Pilots talk to King 5 about 737 Max fix (You tube - I am not allowed to post URLs yet)
At 01:25 one of the pilots says, "the natural pilot reaction is to not allow the airplane to become uncontrollable."
Now I understand that having stick shaker on right after Takeoff, IAS disagree and so on is confusing and overwhelming. But there are airspeed unreliable memory items for that scenario and from what I have read in the preliminary report the crew did not carry those out, which would be the first issue already one could look at. Just food for thought: They could have carried out the airspeed unreliable memory items and then used the pitch and power values for flaps extended as there would not really have been a need to retract the flaps as one would want to return to the airfield with the problem at hand anyway. Under those circumstances MCAS would not have activated at all.
Instead they did retract the flaps 2:05 Minutes after Take off. By that time at least the intial surprise factor concerning the stick shaker going off should have been gone. Based on the faulty sensor signal MCAS moved the horizontal stabilizer creating a nose down movement. What happens in the cockpit at that time? The stabilizer trim wheels can be heard and seen as they are moving and the first time MCAS activated they moved for 10 seconds, which would already qualify as a criteria for a stab trim runaway. If understandably due to all the confusion the pilots didn't notice the trim wheels, the pilot flying will still feel on his control yoke that the force required to maintain the desired pitch attitude has become significantly greater. Coming back to the statement of the American Airlines pilot: what is the natural thing to do now? The pilot will pull a little more on the yoke and then he will trim via the electric trim switch to counter the forces felt. This is the most basic aspect of flying the aircraft and even a Cessna pilot will fly a plane in this way. It has nothing to do with superior skills. In fact this is exactly what the pilot flying did:
After the flaps reached 0, the DFDR recorded automatic aircraft nose down (AND) trim active for 10 seconds followed by flight crew commanded aircraft nose up (ANU) trim.
This actually went on for more than 30 times. Tragic to think about is the fact that even this procedure could have saved the plane. It isn't even necessary to think of the stab trim runaway memory items and set the cut out switches to cut out. The pilot can also just continue to counter the MCAS induced horizontal stab trim nose down movement with an equal horizontal stab trim nose up movement until the flaps are retracted again for landing which is when MCAS will stop operating. Nonetheless after 30 times trimming against the nose down trim movement, it is hard to understand why the pilots did not think to set the stab trim cut out switches to cut out. Every 737 pilot knows that doing this will disable any system to move the horizontal stabilizer if there is unwanted movement. Also does it matter if one knows that the MCAS is moving the stab trim wheels in the cockpit? If there is an engine fire -for example- it also doesn't matter what is causing the fire. All that matters is that I shut down the engine via the engine fire memory items. If my stab trim wheels continue to move even though I don't want them to, all that matters it that I stop this from happening via a procedure that all 737 pilots must know. What does this have to do with superior pilot skill?
We have to wait for the official results to come out and in the case of Ethiopian we really do not know yet what actually happened. Also I realize that it is easy to comment on the accident flight when I am sitting at home on my couch. In fact, as a pilot I have already experienced plenty of situations where I did not have the full situational awareness required and I have of course made plenty of mistakes already. Nonetheless, solely based on the official information that is available so far it seems as if the accident could have been prevented by the crew simply flying the aircraft in a way that comes natural to a pilot and by applying the memory items that they were trained for.