Originally Posted by
oggers
... it doesn't speak to me of an issue with the stick shaker interfering with the operation of the electric trim switch.
If you look closely at the FDR traces, the Lionair captain who faithfully trimmed back up umpteen times did loose the trim switch ever now and then. There are off-blips in almost every long nose-up trim command. Therefore, I do believe, that the ergonomics of the yoke with shaker and high feel forces can make it difficult to actuate the thumb switch continuously. Maybe they had to cradle the column for prolonged high force, hands not in standard position.
Try thumb typing on your phone after you attached a 50 pound brick, while a friend is rattling it...