  Using direct numerical simulation of hydrodynamic turbulence with helicity
forcing applied at all scales, a near-maximum helical turbulent state is
obtained, with an inverse energy cascade at scales larger than the energy
forcing scale and a forward helicity cascade at scales smaller than the energy
forcing scale. In contrast to previous studies using decimated triads, our
simulations contain all possible triads. By computing the shell-to-shell energy
fluxes, we show that the inverse energy cascade results from weakly non-local
interactions among homochiral triads. Varying the helicity injection range of
scales leads to necessary conditions to obtain an inverse energy cascade.
