  The PrandtlPlane aircraft has been recently considered as a possible
candidate to foster the ambition of a greener aviation. Despite the relevant
amount of research carried out in the last years, several aspects of this novel
configuration still need further insight to pave the way to future
applications. Among them, the coupled flight-dynamic and aeroelastic response
is addressed in this work by means of a dedicated in-house framework. For the
evaluation of the aerodynamic forces, an enhanced Doublet Lattice Method, able
to take into account terms typically neglected by classic formulations, is
employed. First, flight-dynamic aspects are considered, showing how effects of
interaction between Short Period or Dutch Roll with elastic modes remarkably
deteriorate the flying qualities. Then, focus is on the aeroelastic stability
of the aircraft. As observed also in previous literature efforts on this
configuration, flutter onset is considerably different when considering the
aircraft being free in the air or fixed in space. Thanks to the adopted
formulation it is shown how, for this PrandtlPlane, the aerodynamic coupling of
elastic and rigid modes has a beneficial effect on flutter onset. However, the
different modal properties, consequence of the diverse boundary conditions,
when switching from fixed-in-space to free-flying aircraft, also play a
relevant role in determining the occurrence of flutter. Whereas for the
longitudinal case both effects contribute increasing flutter speed, for the
lateral-directional case the variation in modal properties has a detrimental
and dominating effect, leading to a flutter speedwell within the flight
envelope.Finally,the work discusses the contributions of the additional terms
modeled by the enhanced Doublet Lattice Method, showing how they induce a
considerable effect when modeling the flight dynamics of the flexible aircraft.
