 gyroscop rigid rotat propel engin wing vibrat mode gyroscop rigid rotat propel engin wing vibrat mode wing vibrat analys account flexibl mount engin reason vibratori gyroscop flexibl rise propel whirl engin mount thought horizont beam cantilev wing horizont vertic flexibl beam infinit rigid horizont vibrat gyroscop moment induc propel result pitch motion axi produc propel axi yaw engin-mount later stiff tical stiff gyroscop effect plai role propel axi undergo pitch vibrat cantilev engin mount purpos paper investig role assumpt propel rigid disc paper divid part 1 deal classic gyroscop theori 2 present engin vibrat mode studi-experiment photograph techniqu model gyroscop mount end cantilev beam 3 present theori coupl motion elast wing gyroscop mount simul engin-propel system airplan 4 consist exampl theori 3 thought reason paramet show whirl rigid propel materi affect wing normal mode shape frequenc 