With the growing importance of helicopters to the national air transportation system, a demand is developing for more IFR (virtually all-weather) helicopter capability. At the same time, it is essential that helicopters be able to take advantage of their unique features and operate within the common ATC system without conflict to or from conventional fixed wing air traffic. A 'test bed' operation was established progressively by the FAA in cooperation with the HAA during the period 1975-1978 to develop real world applications of these and other helicopter operational concepts in the Northeast Corridor (NEC) of the United States. During mid-1979 to early 1980 a nine month controlled NEC test and evaluation project was carried out jointly by the HAA and the FAA. This HAA report describes the methodology and procedures followed, results obtained during the controlled test period, and conclusions and recommendations reached. The complementary FAA Technical Center report referred to in item 15 above will be issued separately. (Author).