  We introduce Partially Coherent Direct Sum (PCDS) quantum channels, as a
generalization of the already known Direct Sum quantum channels. We derive
necessary and sufficient conditions to identify the subset of those maps which
are degradable, and provide a simplified expression for their quantum
capacities. Interestingly, the special structure of PCDS allows us to extend
the computation of the quantum capacity formula also for quantum channels which
are explicitly not degradable (nor antidegradable). We show instances of
applications of the results to dephasing channels, amplitude damping channels
and combinations of the two.
