I believe that, if you research the topic (NYC knife laws are a popular subject, and the statutes are often posted for reference), you will find that carrying a fixed blade in the City is heavily restricted.
My interpretation is that, if one chooses to do so, it should be completely concealed at all times...unless one of the exceptions are met.
Personally, I prefer fixed blade carry; and I won't bring one if I have to go to the City.