Quantitative Assessment of Dynamic Stability Characteristics for Jet Transport in Sudden Plunging Motion

The main objective of this article is to present a training program of loss control prevention for the airlines to enhance aviation safety and operational efficiency. The assessments of dynamic stability characteristics based on the approaches of oscillatory motion and eigenvalue motion modes for jet transport aircraft response to sudden plunging motions are demonstrated in this article. A twin-jet transport aircraft encountering severe clear-air turbulence in transonic flight during the descending phase will be examined as the study case. The flight results in sudden plunging motions with abrupt changes in attitude and gravitational acceleration (i.e. the normal load factor). Development of the required thrust and aerodynamic models with the flight data mining and the fuzzy-logic modeling techniques will be presented. The oscillatory derivatives extracted from these aerodynamic models are then used in the study of variations in stability characteristics during the sudden plunging motion. The fuzzy-logic aerodynamic models are utilized to estimate the nonlinear unsteady aerodynamics while performing numerical integration of flight dynamic equations. The eigenvalues of all motion modes are obtained during time integration. The present quantitative assessment method is an innovation to examine possible mitigation concepts of accident prevention and promote the understanding of aerodynamic responses of the jet transport aircraft.

Simulation of Landing and Take-Off Noise for Supersonic Transport Aircraft at a Conceptual Design Fidelity Level

The German Aerospace Center has launched an internal project to assess the noise impact associated with supersonic transport aircraft during approach and departure. A dedicated simulation process is established to cover all relevant disciplines, i.e., aircraft and engine design, engine installation effects, flight simulation, and system noise prediction. The core of the simulation process is comprised of methods at the complexity and fidelity level of conceptual aircraft design, i.e., typical overall aircraft design methods and a semi-empirical approach for the noise modeling. Dedicated interfaces allow to process data from high fidelity simulation that will support or even replace initial low fidelity results in the long run. All of the results shown and discussed in this study are limited to the fidelity level of conceptual design. The application of the simulation process to the NASA 55t Supersonic Technology Concept Aeroplane, i.e., based on non-proprietary data for this vehicle, yields similar noise level predictions when compared to the published NASA results. This is used as an initial feasibility check of the new process and confirms the underlying methods and models. Such an initial verification of the process is understood as an essential step due to the lack of available noise data for supersonic transport aircraft in general. The advantageous effect of engine noise shielding on the resulting system noise is demonstrated based on predicted level time histories and certification noise levels. After this initial verification, the process is applied to evaluate a conceptual supersonic transport design based on a PhD thesis with two engines mounted under the wing, which is referred to as aircraft TWO. Full access to this vehicle’s design and performance data allows to investigate the influence of flight procedures on the resulting noise impact along approach and departure. These noise results are then assembled according to proposed Federal Aviation Agency regulations in their Notice of Proposed Rulemaking, e.g., speed limitations, for Supersonic transport noise certification and the regulations from Noise Chapters of the Annex 16 from the International Civil Aviation Organization in order to evaluate the resulting levels as a function of the flight procedure.

Morphing Winglet Design for Aerodynamic Performance Optimization of the CRJ-700 Aircraft. Part 1 – Structural Design

This study aims to design a morphing winglet structure for the CRJ-700 regional transport aircraft. The morphing technology is applied on winglets to demonstrate a significant increase of the aerodynamic performance of aircraft. From the aerodynamic data of the LARCASE Virtual Research Simulator VRESIM, the aerodynamic benefits in the cruising phase were obtained through a study on the ParaView software. The morphing winglet design was drawn using CATIA V5; this new concept included several structural components, as well as a simple and light mechanism allowing to orientate the winglet angles between 90° and -90° of inclination. The structural model was exported to HyperMesh structural analysis software. Maximum stresses were obtained, and the model demonstrated its resistance to maximum aerodynamic loads as well as load factors of -2G to 7G.