It really depends on if you want to ignore the rigidbodys mass, You should read up on it and maybe do some experimentation to see what forcemode looks best.

http://unity3d.com/support/documentation/ScriptReference/ForceMode.html

I did a quick search with Google (a great search engine that finds great answers if you use it)

I searched for what I thought you asked: "unity tutorial helicopter physics"

It looks like this: http://www.google.com/search?q=unity+tutorial+helicopter+physics

Second link on the search result page linked to this: http://www.gotow.net/andrew/unity/HelicopterTutorial.pdf

I think you should take a look at that and tell me if that solved your problem :o)

(and no, I am not trying to tease you, merly helping you :o) )