747 'control problems'

[Wing Nut]

Boy, they make this sound so non-chalant, but you know they had to clean the seats after this one...  ;)

NTSB Report

[OTTOL]

Not that big a deal really!  
Water ran down into the forward main spar area and froze, limiting but not completely disabling roll control. Scenarios just like this are frequently practiced in the Sim during recurrent training.