Analysis of Landing-Gear Behavior
01 Jan 1953-
TL;DR: In this article, a theoretical study of the behavior of the conventional oleo-pneumatic landing gear during the process of landing impact is presented in a general form and treats the motions of the landing gear prior to and subsequent to the beginning of shock-strut deflection.
Abstract: This report presents a theoretical study of the behavior of the conventional type of oleo-pneumatic landing gear during the process of landing impact. The basic analysis is presented in a general form and treats the motions of the landing gear prior to and subsequent to the beginning of shock-strut deflection. The applicability of the analysis to actual landing gears has been investigated for the particular case of a vertical landing gear in the absence of drag loads by comparing calculated results with experimental drop-test data for impacts with and without tire bottoming. The calculated behavior of the landing gear was found to be in good agreement with the drop-test data.
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12 Aug 2013
TL;DR: The major focus of the paper was to summarize work documented from the previous decades and to highlight the latest efforts in solving these problems, as well as try to highlight a new trail in designs of auxiliary shiplanding device.
Abstract: For carrier-based aircrafts, high sink speed, the complex environment of deck-landing and design requirement of overload to be 6 or even 7 have brought a big burden to carrierbased aircraft designers. Apart from a large vertical overload created by high sink speed, carrier-based aircrafts also withstand a huge heading overload due to limited deck length. In order to increase the understanding of these problems, a literature survey was performed. The literature survey discussed improvements to aircraft carriers or auxiliary equipments, landing dynamics and shock absorption methods. The major focus of the paper was to summarize work documented from the previous decades and to highlight the latest efforts in solving these problems, as well as try to highlight a new trail in designs of auxiliary shiplanding device.
3 citations
TL;DR: A coupled sequential simulation strategy is proposed and experimentally verified, and this approach divides the complex landing problem into two separate domains, namely a dynamic domain, ruled by a multibody model, and a structural domain, which relies on a finite element model (FEM).
Abstract: Maximum loads acting on aircraft structures generally arise when the aircraft is undergoing some form of acceleration, such as during landing. Landing, especially when considering rotorcrafts, is thus crucial in determining the operational load spectrum, and accurate predictions on the actual health/load level of the rotorcraft structure cannot be achieved unless a database comprising the structural response in various landing conditions is available. An effective means to create a structural response database relies on the modeling and simulation of the items and phenomena of concern. The structural response to rotorcraft landing is an underrated topic in the open scientific literature, and tools for the landing event simulation are lacking. In the present work, a coupled sequential simulation strategy is proposed and experimentally verified. This approach divides the complex landing problem into two separate domains, namely a dynamic domain, which is ruled by a multibody model, and a structural domain, which relies on a finite element model (FEM). The dynamic analysis is performed first, calculating a set of intermediate parameters that are provided as input to the subsequent structural analysis. Two approaches are compared, using displacements and forces at specific airframe locations, respectively, as the link between the dynamic and structural domains.
3 citations
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01 Jan 2014
TL;DR: An introduction to the general characteristics of commercial jet transport landing gear is presented in this article, where requirements for the size and location of the landing gear and associated ground handling characteristics are discussed.
Abstract: An introduction to the general characteristics of commercial jet transport landing gear is presented Requirements for the size and location of the landing gear and the associated ground handling characteristics are discussed Operational factors considered include quasi-static loads on landing gear, dynamic loads in landing, and stability considerations in determining the location of the main gear and the nose gear Also treated are ground clearance requirements in takeoff and landing, positioning the landing gear, maneuverability in ground operations, and powered wheel-drive systems Methods for the selection of aircraft tires and wheels based on load requirements are covered Landing gear configurations, shock-absorbing landing gear struts, and methods for properly sizing such struts, and dynamic landing gear analysis are discussed Landing brake system design and sizing approaches are described
3 citations
TL;DR: In this paper, a nature-inspired optimization technique was used to solve an inverse problem represented by the identification of an aircraft landing gear model, in which the objective function represents the difference between the measured characteristics of the system and its model counterpart.
Abstract: This work deals with the application of a nature-inspired optimization technique to solve an inverse problem represented by the identification of an aircraft landing gear model. The model is described in terms of the landing gear geometry, internal volumes and areas, shock absorber travel, tire type, and gas and oil characteristics of the shock absorber. The solution to this inverse problem can be obtained by using classical gradient-based optimization methods. However, this is a difficult task due to the existence of local minima in the design space and the requirement of an initial guess. These aspects have motivated the authors to explore a nature-inspired approach using a method known as LifeCycle Model. In the present formulation two nature-based methods, namely the Genetic Algorithms and the Particle Swarm Optimization were used. An optimization problem is formulated in which the objective function represents the difference between the measured characteristics of the system and its model counterpart. The polytropic coefficient of the gas and the damping parameter of the shock absorber are assumed as being unknown: they are considered as design variables. As an illustration, experimental drop test data, obtained under zero horizontal speed, were used in the non-linear landing gear model updating of a small aircraft.
3 citations
Cites background from "Analysis of Landing-Gear Behavior"
...The air compression process inside the shock absorber is based on the polytropic compression law for an ideal gas [6]....
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...Besides the hydraulic resistance and gas-oil compression effects, the damping due to the shock absorber bearing friction force is also relevant in the dynamic behavior of the landing gear [6]....
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TL;DR: An elite re-optimized hybrid genetic algorithm is designed, which combines the merits of a genetic algorithm and pattern search to avoid being trapped by a local optimum, but also improves the precision of results and saves on the time for trimming.
Abstract: Trimming aircraft on the ground is an absolutely necessary for flight simulators. In order to carry out this task, the aircraft-runway dynamic model is analyzed, and then an elite re-optimized hybrid genetic algorithm for trimming the model is designed, which combines the merits of a genetic algorithm and pattern search. It does not only avoid being trapped by a local optimum, but also improves the precision of results and saves on the time for trimming. Because this trim method requires only in-out information of the dynamic model, it is a universal tool and can be used on different trim works of different simulated aircraft. Its efficiency is then validated in a flight simulator, which reveals its engineering significance.
2 citations
References
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01 May 1948
5 citations
"Analysis of Landing-Gear Behavior" refers background or methods in this paper
...In addition to the total fo,'ce on the upper mass, figure 4 Ca) presents calcLdatcd time histories of the hydraulic and pneumatic components of the shock-strut force, as determined from equations (2) and (3), respectively....
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...Equation (2) can be nlade applicable to both tile compression and elongation strokes by introducing tlle factor 7; to indic....
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