And they recognized it as such and completed the runaway trim checklist, but they couldn't use manual trim (as advised) to recover from the situation, because aerodynamic forces acting on the stabilizer overpowered them.
Two Swedish pilots demonstrated this scenario in a 737NG simulator: https://youtu.be/aoNOVlxJmow?t=606 Ethiopian pilots were in even more stressful situation, because they also had broken AOA sensor with unreliable airspeed indication, active left stick shaker, occasional terrain proximity warnings and overspeed clicker.
No procedures or training existed for the situation they were in. Pilots of early 737s were taught the so-called rollercoaster maneuver to temporarily relieve the load to allow manual trimming, but that was scrapped decades ago.
Thank you for the reference.
Having it repeatedly come on and run is runaway trim. Trying to interpret the meaning of "continuous" makes for great courtroom drama, but is unhelpful when you're faced with a crisis. Besides, if the runaway trim was caused by an intermittent electrical short, would you dismiss that as well, too? Or would you turn the sucker off and save your life and let the mechanics sort it out on the ground?
> it's impossible to isolate automated systems without losing all electric assist.
The column electric trim switches override all other trim inputs. That's why the procedure is as follows:
Boeing Emergency Airworthiness Directive
"Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT."
https://theaircurrent.com/wp-content/uploads/2018/11/B737-MA...