Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
incapable [ɪnˈkeɪpəbl] adj (helpless) беспо́мощный*беспо́мощен (unable to)
incapable of sth/doingнеспосо́бный*неспосо́бен на что-н/ +infin
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
Русский: