  The establishment of global helicopter linear model is very precious and
useful for the design of the linear control laws, since it is never afforded in
the published literatures. In the first principle approach, the mathematical
model was developed using basic helicopter theory accounting for particular
characteristic of the miniature helicopter. No formal system identification
procedures are required for the proposed model structure. The relevant
published literatures however did not present the linear models required for
the design of linear control laws. The paper presents a step by step
development of linear model for small scale helicopter based on first-principle
approach. Beyond the previous work in literatures, the calculation of the
stability derivatives is presented in detail. A computer program is used to
solve the equilibrium conditions and then calculate the change in aerodynamics
forces and moments due to the change in each degree of freedom and control
input. The detail derivation allows the comprehensive analysis of relative
dominance of vehicle states and input variables to force and moment components.
Hence it facilitates the development of minimum complexity small scale
helicopter dynamics model.
