The so call powder it is the residual anti/de ice fluid that dries up and then becomes powder or in other cases somehow very dense material more known as GEL.
In all 3 cases the desent, approach and landing were rather interesting. Even circling at lower altitudes didn't help. All the crews involved landed only with trim input, and 2 out of 3 the trim was partial....
The post flights inspections of the elevator found the elevetor control block by the upmentioned material that somehow expanded and frozen up.
It is not uncommon for other aircraft but I'm specifically looking for E-145 cases
cheers