D-C arc interruption for aircraft

Cyril G. Veinott (Westinghouse Electric and Manufacturing Company, Lima, Ohio): Quill and Rader have presented some valuable experimental information which should be of appreciable assistance not only to builders of switches but also to users of them. While there is no apparent reason to doubt the accuracy of their data on arc interruption and no apparent reason to challenge their general qualitative conclusions, there is reason to discuss their method of reproducing altitude conditions. They state that they have reproduced the standard National Advisory Committee for Aeronautics pressure at altitude but not the temperature. Arc-interruption phenomena are a function of density of the air, not pressure alone; hence, the standard NACA air density at altitude should have been reproduced instead of merely pressure. Since temperature is not of itself important, the authors were justified in not taking the additional trouble to reproduce the standard NACA temperatures, but their results should have been plotted as a function of density altitude, not pressure altitude.