Parent & Child Smooth Problem

[nitin-kumar-1]

I made a jet plane in maya but i got a problem in smoothing object because some of my object are parentised to each other and when i apply a smooth on parent object so it gives me a smooth on child object not on the parent object so please if any one know about this problem please help me out ASAP.

[enyon]

This behaviour is still same in Maya 2014

[drblacksnake]

once you unparent, does smoothing works well?