BTW, after reading a number of NTSB reports I would say a forced landing is any landing required by circumstances outside the normal landing procedures.
Like this one on the Hudson River (not US Airways).
http://www.ntsb.gov/aviationquery/brief.aspx?ev_id=20130128X02957
“Unable to maintain altitude, she made a mayday call and performed a forced landing on the river.”
Unable.
Remember that word.