Originally Posted by
Albino
Just to confirm, I'm talking about 'Control airplane pitch manually with control column and main electric trim as needed'
This is pretty basic stuff.
Yes, and I agree. But then you could then argue it shouldn't even be included in the memory items, and all the discussion about step 2 is irrelevant here.
It's not exactly the same situation but, I looked again at Mentour's video that demonstrates the runaway stabilizer memory items. They already have the A/P disconnected when the runaway starts, and the thumb switches are not working at all during the runaway. He does try to use the thumb switches to control the trim, but then so did the Ethiopian crew.
This is how it went (some small details omitted):
17:18 - runaway starts
17:28 - Mentour (PF) - "I'm not doing that"
17:40 - F/O (PM) identifies the issue as a runway stabilizer
17:50 - Mentour asks the F/O to perform the runway stabilizer memory items
17:55 - F/O - "control column: hold firmly"
17:57 - Mentour - "holding firmly"
17:59 - F/O - "auto pilot - disengage"
18:01 - Mentour - "autopilot is disengaged"
18:04 - F/O - "auto throttle - disengage"
18:07 - Mentour - "if you can do that for me please"
18:09 - F/O - "disengaged"
18:11 - F/O - "if it continues, I will go with the stab trim cutout switches"
18:13 - Mentour - "ok, let's evaluate this to see if it's moving"
18:20 - F/O - "memory items for the runaway stabilizer complete"
18:21 - Mentour - "yeah, let's evaluate"
18:25 - Mentour - "I have no authority of the trim at the moment"
18:29 - F/O - "roger"
18:32 - Mentour - "I can't control it manually, so it doesn't really work, so if you can continue with the memory items please"
18:37 - F/O - "memory items - stab trim cutout switches to cutout"
18:40 - Mentour - "Continue"
18:41 - F/O moves the switches to the cutout position
18:42 - F/O: "Cutout"
So, between the start of the runaway and using the cutout switches it takes them 83 seconds to perform the runaway stabilizer memory items. With no additional failures and alarms that can distract them and increase their workload. With that in mind, do you think the stabilizer runaway memory items are adequate for dealing with an MCAS failure induced by an AOA sensor failure?
My guess is the Ethiopian crew was aware they could be dealing with MCAS, so they actually skipped some memory items and other procedures to stop MCAS as soon as possible:
05:40:00 - first MCAS AND trim
05:40:12 - pilot ANU trim
05:40:20 - second MCAS AND trim
05:40:27 - the Captain advised the First-Officer to trim up with him
05:40:28 - pilot ANU trim
05:40:35 - the First-Officer called out “stab trim cut-out” two times. Captain agreed and First-Officer confirmed stab trim cut-out.
05:40:41 - third MCAS attempt to apply AND trim, but it doesn't affect trim anymore
They did all that in under 40 seconds.
It's funny. Until the preliminary report was released many people were arguing that the cut-out switches should be used as soon as possible when you are dealing with an MCAS failure. Now people say that you should first bring the aircraft is in perfect trim before doing it. So basically that you should use the cutout switches in a 5 second interval, not too soon, and not too late, or it's pilot error. I disagree. This is not a fighting video game when you have to mash the right sequence of buttons with the right timing to produce a "combo". That's not OK when the lives of hundreds of people are at stake.