Aviation Daily 20 October 1971 tells about test flights of a 10 passenger Turbo Mallard between BOS, the East River in NY, and "both the Potomac River and National Airport". Doesn't say where it docked in NY. The interesting item: "Last phase of flight testing will involve evaluation of the Talar IFR system installed out in the East River on the end of a dock."
Anybody heard of Talar? Where was the NY setup? What visibility did it need?