Final minutes of Lion Air LT601 (accident flight).
It is true, if proper procedure was followed, then the PIC handed control over to the SIC at a peaceful moment when the airplane was reasonably good trim. Maybe things did happen like that, and the SIC made a mess of a perfectly flyable situation. However, there is not a lot of data in the FDR traces to confirm that the proper procedure was followed.
I agree that the altitude and airspeed of LT601 during the five minutes the PIC was flying do seem to be steadier than in the Ethiopean mishap. But a couple of trends can be detected in the FDR traces.
1. The airspeed gradually increases during the period the PIC was in control.
2. The swings in altitude get progessively greater during the period the PIC was in control.
3. The pitch trim position gradually worsens during the period the PIC was in control.
4. Two minutes before he handed over control, the PIC advanced the throttles. He did this in response to a fall in altitude. He returned the throttles to their previous position after about a minute of additional thrust. (See the fuel flow traces.) It was about a minute after that that he turned over control.
It is possible that the favourable changes in altitude which occurred as a result of the throttle push gave the PIC confidence that the airplane was controllable, and could be made to go up and down even if the trim was acting up. His decision to turn things over to the SIC would then have been a natural follow-up, to give himself the time to think or investigate. That is possible, but by no means a certainty.
I expect that the CVR will help sort this out.
YYZjim