A flight control system is provided with one or more modal sensors that
are each configured to measure the rate and possibly acceleration for a
flexible body mode of the flight vehicle. The modal sensor's rate and
suitably acceleration are subtracted from the rate and acceleration
measured by the IMU such that the values provided to the flight
controller more closely represent only the rate and acceleration of the
flight vehicle's rigid airframe component. A piezoelectric modal sensor
is capable of sensing a particular flexible body mode over variations in
the modal frequency without inducing additional phase loss in the control
loop in order to maintain suitable phase and gain margins. Sensors are
suitably provided for at least and possibly only the 1.sup.st lateral
bending modes in the pitch and yaw channels.