FDL-B 131/1A. Waffen Handbuch

The Fernbedienbare Drehlafette FDL 131 remotely-controlled gun turret system, used as a forward-mount dorsal turret on the He 177A, used two MG 131s for dorsal defense, with the experimental Hecklafette HL 131V manned aircraft tail turret design, meant to be standardized on the never-built A-6 version of the He 177A.