Some basic training is amiss! Using roll control to counteract to correct the situation was a mistake. The rudder should have been the primary control input to correct the situation. Even if the unresponsive engine was at idle thrust there should have been more than enough rudder to keep the aircraft flying straight at flight level (this was a Boeing not an Airbus) or maybe a slow decent to three engine flight level. One would need the charts to confirm what the allowable three engine flight level would have been. I doubt that it could have maintained FL 410, all dependent on temperature and weight. A quick think back tells me that the two engine FL would have been most likely either side of FL 210, or maybe a bit lower. Retarding the other outboard was a big mistake. With two engines producing thrust and two at idle the aircraft will have to start descending. Check the drift down chart for what the target speed would be and adjust as altitude drops and the aircraft will level off on its own when that FL has been reached.
I have not read the full report, but using the autopilot with altitude hold and lots of roll control only compounded the problem.
One of the other problems comes from all of our cultures. The senior officer (oldest) is always right. This happened a long time ago, and maybe we have all learned that each crew member has an input and all suggested should be considered.
Last edited by mustangsally; 20th Feb 2019 at 13:28.