what is importance of doing IRLF

sir/madam...

i m little bit confused about doing inerta relief command analysing free free model...such as aircraft....

i have an quey that.. if command IRLF,1 used in ansys for static analysis... but model is in dynamic ?

what will be the the displacement and stress plot using IRLF,1 command....will these simmulate the correct model??

please guide me in this regards..

Dileep