  Localization properties of random-mass Dirac fermions for a realization of
mass disorder, commonly referred to as Cho-Fisher model, is studied on the
D-class chiral network. We show that a simple RG description captures
accurately three phases: thermal metal and two insulators with quantized Hall
conductances, as well as transitions between them (including critical
exponents). We find that, with no randomness in phases on the links,
transmission via the RG block exhibits a sizable portion of perfect resonances.
Delocalization occurs by proliferation of these resonances to larger scales.
Evolution of the thermal conductance distribution towards metallic fixed point
is synchronized with evolution of signs of transmission coefficients, so that
delocalization is accompanied with sign percolation
