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Aileron

About: Aileron is a research topic. Over the lifetime, 1697 publications have been published within this topic receiving 14023 citations.


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Journal ArticleDOI
TL;DR: In this paper, a point-function relationship between the local pressure on the surface of a wing and the normal component of fluid velocity produced by the wing's motion is predicted, and the computation of generalized forces in aeroelastic equations, such as the flutter determinant, is then reduced to elementary integrations of assumed modes of motion.
Abstract: Representative applications are described which illustrate the extent to which simplifications in the solutions of high-speed unsteady aeroelastic problems can be achieved through the use of certain aerodynamic techniques known collectively as "piston theory." Based on a physical model originally proposed by Hayes and Lighthill, piston theor}^ for airfoils and finite wings has been systematically developed by Landahl, utilizing expansions in powers of the thickness ratio 8 and the inverse of the flight Mach Number M. When contributions of orders 8/M and 8/M are negligible, the theory predicts a point-function relationship between the local pressure on the surface of a wing and the normal component of fluid velocity produced by the wing's motion. The computation of generalized forces in aeroelastic equations, such as the flutter determinant, is then always reduced to elementary integrations of the assumed modes of motion.

599 citations

Journal ArticleDOI
TL;DR: In this article, a new approach for analyzing nonlinear and high-a dynamic behavior and stability of aircraft is presented, which involves the application of bifurcation analysis and catastrophe theory methodology to specific phenomena such as stall, departure, spin entry, flat and steep spin, nose slice, and wing rock.
Abstract: A new approach is presented for analyzing nonlinear and high-a dynamic behavior and stability of aircraft. This approach involves the application of bifurcation analysis and catastrophe theory methodology to specific phenomena such as stall, departure, spin entry, flat and steep spin, nose slice, and wing rock. Quantitative results of a global nature are presented, using numerical techniques based on parametric continuation. It is shown how our methodology provides a complete representation of the aircraft equilibrium and bifurcation surfaces in the state-control space, using a rigid body model with aerodynamic controls. Also presented is a particularly useful extension of continuation methods to the detection and stability analysis of stable attracting orbits (limit cycles). The use of this methodology for understanding high-a phenomena, especially spin-related behavior, is discussed. RENDS in fighter aircraft design over the past few decades have resulted in configuration s noted for their high speed and performance capability. The cost of achieving this capability has been a drastic, often fatal loss of positive control of the aircraft as the pilot operates at or near the extremes of the flight envelope. This is especially true for aircraft motion at high angles of attack (a), where large deviations both in the state and control variables limits the application of the usual linearized analysis techniques. There is a conspicuous lack of techniques for analyzing global stability and large maneuver response of aircraft. While certain phenomena (e.g., roll coupling) have been analyzed in an isolated manner, there exists a clear need for a unified approach to analyze systematically global aircraft behavior at high a.

205 citations

Journal ArticleDOI
TL;DR: In this article, the effects of nonlinear structural terms on the flutter of a wing capable of bending and twisting and, also, of a system including a control surface are investigated, including free play, a hysteresis loop, and cubic variations.
Abstract: This paper presents some effects of nonlinear structural terms on the flutter of a wing capable of bending and twisting and, also, of a system including a control surface. Several type , of nonlinearities in the stiffness are investigated, including free play, a hysteresis loop, and cubic variations. These are introduced in the torsional degree of freedom of the wing and in the aileron stiffness in the three degree of freedom system. Calculations have been made on an analog computer. A wind-tunnel investigation of one case having free play in the torsional degree of freedom has been made, and good correlation between theory and experiment is shown. The results indicate that the stability of a nonlinear system is highly dependent on the magnitude of initial displacements of the system from equilibrium. I t is shown that in many cases the flutter speed is decreased by increasing the initial disturbance. The results also indicate that when a nonlinear system becomes unstable its flutter may become self-limited.

197 citations

Journal ArticleDOI
TL;DR: A natural-Iamina r-flow airfoil, the NLF(1)-0115, has been recently designed for general-aviation aircraft at the NASA Langley Research Center as mentioned in this paper.
Abstract: A natural-Iamina r-flow airfoil, the NLF(1)-0115, has been recently designed for general-aviation aircraft at the NASA Langley Research Center. During the design of this airfoil, special emphasis was placed on experiences and observations gleaned from other successful general-aviation airfoils. For example, the flight lift-coefficient range is the same as that of the turbulent-flow NACA 23015 airfoil. Also, although beneficial for reducing drag and producing high lift, the NLF(1)-0115 airfoil avoids the use of aft loading, which can lead to large stick forces if utilized on portions of the wing having ailerons. Furthermore, not using aft loading eliminates the concern that the high pitching-moment coefficient generated by such airfoils can result in large trim drag if cruise flaps are not employed. The NASA NLF(1)-0115 airfoil has a thickness of 15% chord. It is designed primarily for general-aviation aircraft with wing loadings of 720-960 N/m2 (15-20 lb/ft2). Low-profile drag as a result of laminar flow is obtained over the range from c, = 0.1 and R = 9 x 106 (the cruise condition) to c, = 0.6 and R = 4 x 106 (the climb condition). While this airfoil can be used with flaps, it is designed to achieve a c,,max of 1.5 at R = 2.6 x 10 6 without flaps. The zero-lift pitching moment is held to c,H,0 = -0.055. The hinge moment for a 20% chord aileron is fixed at a value equal to that of the NACA 632-215 airfoil, CH = — 0.0022. The loss in cAmax due to leading-edge roughness at R = 2.6 x 10 6 is 11% as compared with 14% for the NACA 23015.

193 citations

Journal ArticleDOI
TL;DR: Bifurcation theory has been used to study the nonlinear dynamics of the F-14, and a simple feedback control system was designed to eliminate the wing rock and spiral divergence as mentioned in this paper.
Abstract: Bifurcation theory has been used to study Ihe nonlinear dynamics of the F-14. An 8 degree-of-freedom model that does not include the control system present in operational F-14's has been analyzed. The aerodynamic model, supplied by NASA, includes nonlinearlties as functions of the angles of attack and sideslip, the rotation rate about the velocity vector, and the elevator deflection. A continuation method has been used to calculate the steady states of the F -14 as continuous functions of the elevator deflection. Bifurcations of these steady states have been used to predict the onset of wing rock, spiral divergence, and jump phenomena that cause the aircraft to enter a spin. A simple feedback control system was designed to eliminate the wing rock and spiral divergence instabilities. The predictions were verified with numerical simulations.

147 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202340
202288
202135
202047
201964
201879