A 120-volt D-C aircraft electric system

The practicability of using 120-volt d-c power in large airplanes has been a subject of discussion for some time. This paper describes the 120-volt d-c system and the equipment used on the Navy flying boat Mars, the service requirements, and the problems incidental to development and design of the components of the system. Calculated weights for several arrangements of generating equipment including the installed system are tabulated for comparison and the weight of the installed 120-volt d-c system is compared with the weight of the 28.6-volt d-c system. A summary report on flight tests and service operations provides the basis for conclusions relative to the practicability of 120-volt direct current for large aircraft.