Re:Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Be...
by inferiorhuman on Tuesday March 19, 2019 @11:23PM
(#19438631)
That procedure wasn't sufficient
Winner, winner, chicken dinner. The existing runaway stabilizer trim checklist does not fit the MCAS failure to a T. The procedure dictates that you stop if the trimming action stops when you counter it with the switches (MCAS pauses when you do this). Unfortunately when you're taught to only think inside the box, you'll go as far down that checklist as you need to and no further.
Beyond that, just after takeoff is one of the busiest part of the flight. In fact, if you look at the graphs you'll see that the stick shaker on the left side was going crazy almost immediately after takeoff (and before MCAS kicked in as a result of retracting the flaps). The pilots of flight 610 were able to reign in MCAS with the trim buttons and almost certainly continued to do so in order to focus on the other failures and their relevant checklists (stick shaker, unreliable airspeed, elevator feel system non-op).
[One thing I've been wondering: somehow the pilots were able to bring the nose back up... it was only (apparently) after multiple nose downs that they eventually failed to recover the plane. What was going on there? It's as if they understood how to correct the stabilizer trim, but weren't aware of the cut-off switches.]
Yep, to me, that looks an awful lot like some sort of hardware failure. Something to look for in the subsequent and final reports.
Winner, winner, chicken dinner. The existing runaway stabilizer trim checklist does not fit the MCAS failure to a T. The procedure dictates that you stop if the trimming action stops when you counter it with the switches (MCAS pauses when you do this). Unfortunately when you're taught to only think inside the box, you'll go as far down that checklist as you need to and no further.
Beyond that, just after takeoff is one of the busiest part of the flight. In fact, if you look at the graphs you'll see that the stick shaker on the left side was going crazy almost immediately after takeoff (and before MCAS kicked in as a result of retracting the flaps). The pilots of flight 610 were able to reign in MCAS with the trim buttons and almost certainly continued to do so in order to focus on the other failures and their relevant checklists (stick shaker, unreliable airspeed, elevator feel system non-op).
[One thing I've been wondering: somehow the pilots were able to bring the nose back up... it was only (apparently) after multiple nose downs that they eventually failed to recover the plane. What was going on there? It's as if they understood how to correct the stabilizer trim, but weren't aware of the cut-off switches.]
Yep, to me, that looks an awful lot like some sort of hardware failure. Something to look for in the subsequent and final reports.