NACA issues initial report on the analysis of ground resonance
Friday, July 30, 1943
Ground resonance is an interaction between the rotor and the airfame, when on the ground, that can lead to catastrophic failure.
R.P. Coleman of NACA documented the early analysis that would lead to an understanding of ground resonance for rotorcraft.
The reference is provided below,
(Note: Only the month and year of the report are valid)
It should be noted that there is evidence to suggest that the fundamental understanding of ground resonance had already been developed by the german mathematician Gigling who was working under Heinrich Focke (see " Gottinger Monograph N: A Historic Document is Back", Berend van der Wall, DLR, paper presented at AHS Forum 72, West Palm Beach, FL, May 2016, Page 16).