Journal of Aerospace Engineering

This paper presents an approximate three-dimensional elasticity solution for an infinitely long, cross-ply laminated circular cylindrical shell panel with simply supported boundary conditions, subjected to an arbitrary discontinuous transverse loading. The solution is based on the principal assumption that the ratio of the thickness of the lamina to its middle surface radius is negligible compared to unity. The validity of this assumption and the range of application of this approximate solution have been established through a comparison with an exact solution. Results of classical and first-order shear deformation shell theories have been compared with the results of the present solution to bring out the accuracy of these theories. It is also shown that for very shallow shell panels the definition of a thin shell should be based on the ratio of thickness to chord width rather than the ratio of thickness to mean radius.

Physical and numerical experiments on flow developments around an NACA-0012 airfoil were conducted to explore the possibility of enhancing the airfoil's aerodynamic performance by vortex lift augmentation. The paper focuses on the effects of the separated flow and subsequent vortex formation, generated by backward-facing steps on pressure distributions and corresponding flow occurrences around the airfoil. Various step configurations are examined to determine their effect on lift and on lift-to-drag ratios. A discussion of the effects of main geometrical parameters of upper and lower surface steps on the airfoil performance, based on computational and physical flow visualization experiments, are presented. The results suggest that incorporation of backward-facing steps on the lower surface that are located at the midchord and extend back to the trailing edge with 50 depth of the airfoil chord may lead to considerable enhancements in lift coefficients and lift-to-drag ratios. The data produced may serve as a reference for future studies on the possible use of separated vortex structures in enhancing the aerodynamic or hydrodynamic performance of vehicles and structures.

This paper presents preliminary results of the development of a virtual flight data recorder (VFDR) for commercial airliners. Federal Aviation Administration (FAA) regulations, currently being revised, mandate the recording of 11 dynamic parameters, not including the control surface deflections. The absence of these data can be critical for crash investigation purposes. This paper proposed the introduction of a VFDR based on a neural network simulator (NNS) and a neural network reconstructor (NNR). The NNS is trained, using flight data for the particular aircraft, to simulate any desired control surface deflections (or any other parameter of interest not recorded by the FDR), minimizing a cost function based on the differences between the available data from the FDR and the output from the NNS. The VFDR scheme has been introduced, tested, and validated with flight data from a Boeing 737-300 with an FDR with extended recording capabilities showing accurate reconstruction of the control surface deflections' time histories. The VFDR can be considered a tool for crash investigations where control surface failures are believed to be a factor.