The stabilizer trim switches enable/disable the electric stabilizer trim. There's a wheel with a foldout hand crank to manually control the stabilizer trim. Based on the preliminary report, the copilot was unable to turn the wheel which is why they turned the electric stabilizer trim back on.
One hypothesis is that because the pilot was fighting the extreme nose down stabilizer with nose up elevator the jackscrew that moves the stabilizer was so heavily loaded that the co-pilot didn't have enough strength to manually turn the trim wheel which is connected to the jackscrew by cables.
Another theory is that it was possible, but requires both pilots to turn their cranks together -- not possible if one is pulling back on their yoke and unable to let go without that being deadly.
Comments
The stabilizer trim switches enable/disable the electric stabilizer trim. There's a wheel with a foldout hand crank to manually control the stabilizer trim. Based on the preliminary report, the copilot was unable to turn the wheel which is why they turned the electric stabilizer trim back on.
One hypothesis is that because the pilot was fighting the extreme nose down stabilizer with nose up elevator the jackscrew that moves the stabilizer was so heavily loaded that the co-pilot didn't have enough strength to manually turn the trim wheel which is connected to the jackscrew by cables.
Another theory is that it was possible, but requires both pilots to turn their cranks together -- not possible if one is pulling back on their yoke and unable to let go without that being deadly.