USAAMRDL technical report. 74-85. OH-6A propulsion system vibration investigation; final report for period, Nov. 27, 1972-June 15, 1974 [with list of references; by R. J. Sullivan, R. E. Head , G. J. Korkosz, J. R. Neff, S. J. Soltis, and M. A. Gockel].