"He had set the autopilot to descend to 100 ft (30 m) and accelerated the speed of the descending aircraft several times thereafter." Is that something that wo

"He had set the autopilot to descend to 100 ft (30 m) and accelerated the speed of the descending aircraft several times thereafter." Is that something that would be used during normal operations, or in an emergency landing? If not, why is it a permitted action?