Yea the interval is actually 20 seconds which is a really long time to a pilot thinking he is in an emergency. If you look at the period of the ups and downs of

Yea the interval is actually 20 seconds which is a really long time to a pilot thinking he is in an emergency. If you look at the period of the ups and downs of the Ethiopian flight they roughly correspond to that 20-second interval. Just when he thinks he's fixed it, it strikes again and again, taking a more aggressive nose down attitude each time.