To resolve issues starting MATLAB on Mac OS X 10.10 (Yosemite) visit: http://www.mathworks.com/matlabcentral/answers/159016
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You can use a 3 dof block from the Aerospace Blockset to get started. From there, you can find a number of papers that detail the aerodynamic force buildup of the helicopter in the body axis. You can simply add the aerodynamics and the environment blocks from the aerospace blockset with the 3-dof for a good model.
This file exchange submission may also be of help.