 vibrat isol aircraft power plant vibrat isol aircraft power plant vibrat aircraft structur trace vibratori forc origin power plant forc transmit aircraft wai 1 action air forc surfac aircraft adjac slip stream propel 2 direct transmiss unbalanc forc power plant engin mount caus preponder disturb vibratori stress induc engin mount structur occasion produc fatigu failur associ part shorten life entir aircraft structur psycholog physiolog effect continu vibrat attend nois passeng crew major sourc rapid fatigu intim associ fly desir drastic reduc vibrat question paper limit consider directli transmit forc consid power plant rigid bodi attach flexibl aircraft consid rigid bodi larg mass limit case engin engin support structur axial symmetri radial engin method emploi easili extend case 