The transport aircraft experience frequently higher loads than what are
designed for, in particular, in unusual flight conditions, such as
encountering severe atmospheric turbulence, sudden evasive motion in
avoiding air collision, and hard landings. The structural damage, fatigue
cracking, or non-typical structural deformation may be caused by these high
loads. This paper will present a method based on the concept of aeroelastic
effects on stability and control derivatives to indirectly determine the
structural integrity of transport aircraft. Aerodynamic models are
established through fuzzy-logic modeling (FLM) of the flight data extracted
from quick access recorder (QAR). Stability and control derivatives with
static aeroelastic effects are then estimated by using these aerodynamic
models. Qualitative evaluation of the aeroelastic effects on the wing and tail
is based on the second derivatives of normal force and pitching moment
coefficients with the angle of attack and dynamic pressure, respectively. A
twin-jet transport aircraft encountered severe atmospheric turbulence with a
sudden plunging motion in revenue flight as the study case. The
comparative analysis of aeroelastic effects for this twin-jet transport before
and during severe atmospheric turbulence will be illustrated in this paper.