The paper presents a recent effort to explore tilt-rotor aeromechanica
l phenomena with an emphasize on aeroelastic stability in forward flig
ht (airplane mode). A general tilt-rotor model has been developed and
implemented using a numerical technique that preserves symbolic exactn
ess of the equations of motion. The stability study is based on an eig
envalue analysis about a nonlinear periodic trim solution. The present
method enables both high resolution periodic response, and clear trac
ing of the instability drivers by providing the exact partial derivati
ves of the involved degrees of freedom in each one of the associated e
quations of motion. In addition to the common way of identifying trend
s and sensitivities by parametric study, the present approach supplies
information about the effectiveness of possible mechanisms that are n
ot included in the baseline model. The present results demonstrate the
ability of the method to provide such unique insight into the aeromec
hanical phenomena in forward flight. illustrative indications regardin
g required tilt-rotor design features that will postpone the instabili
ty phenomena are discussed. (C) 1998 Elsevier Science Ltd. All rights
reserved.