If my memory is serving me right then I think that Helical Interpolation is an Option on your control, that will mean that the Parameter to enable it will be one of the 9000 Parameters, I think it is Parameter 9930 Bit 3 that needs to be changed, usually costs money for Fanuc to do it
That would look something like 9930 00001000. Parameters count from the right and begin with 0 not 1 so Bit 8 from the right is actually numbered 7, hope that helps
Sorry, that`s all I`ve got
P.S. Just found this, have a look here for yourself
https://www.scribd.com/doc/273845264...Parameter-9900
Regards
Rob