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Recent research shows that braking of vehicles equipped with a front brake light is identified significantly earlier than braking of vehicles without front brake lights. Moreover, the absence of front brake lights leads to more conservative road crossing decisions. These results suggest that front brake lights are able to facilitate the pedestrians' anticipation of dangerous traffic situations, thereby increasing road safety. The present research investigated the effects of front brake lights in the real traffic of the Berlin Tegel Airport airside. A total of 102 vehicles were equipped with front brake lights and circulated in airport traffic for a period of three and a half months. Before and after this test period, 197 staff members were asked about their experiences with and their attitude towards front brake lights. The results show that front brake lights rarely led to misunderstandings, whereas they were significantly more often perceived to facilitate communication avoiding dangerous situations. The attitude towards front brake lights was already positive at the first interview and improved significantly during the measurement period. Overall, a great majority of participants stated that front brake lights improve communication between road users and thus increase road safety. [ABSTRACT FROM AUTHOR]

In this research, a new type of magnetorheological damper for a small-sized aircraft landing gear system is proposed and its performance is evaluated with respect to design parameters of the magnetic core. As a first step, a new configuration of magnetorheological damper for the landing gear system, which consists of orifices, recoil valve, and magnetic circuits, is introduced with working principles. After formulating the governing equations of motion, six different models of magnetorheological damper featuring different number of magnetic core and different pole length are chosen to investigate both the landing stability and the efficiency. Subsequently, the distribution of the magnetic field intensity of each model is analyzed through the finite element method, followed by the calculation of the field-dependent damping force to be used for the landing simulation, which is undertaken by adopting the dynamic model of a half airplane landing gear system. In order to identify the significance of the magnetic core parameters, the landing stability is judged from the sign of the minimum force and the landing efficiency is determined from the energy dissipation during the vertical drop motion. [ABSTRACT FROM AUTHOR]

One of the major subsystems of each airplane is the landing gear system which must be capable of tolerating extreme forces applied to structure during ground maneuver to improve vibration absorbing performance. The traditional landing gear system performs this function well under normal condition, whereas with varying condition of landing and situation of the runway for the airplane, performance of this system decreases noticeably. In this research, for overcoming this problem, the coefficients of controller, the parameters of hydraulic nonlinear actuator added to the traditional shock absorber system, and the vibration absorber are optimized simultaneously by the bee intelligent multi-objective algorithm. As well as, for proving adaptability of this algorithm, this paper presents the sensitivity analysis of three point landing due to the additional payload and the touchdown speed and the robustness analysis of one and two point landings due to the wind conditions as emergency situation on the runway as an innovated work. In order to evaluate the effectiveness and the efficiency of proposed method, the flight dynamic differential equations of an Airbus 320–200 vibrational model during the landing phase are derived and through the numeric technique are solved. The results of numerical analysis for this large-scale airplane model with six degrees of freedom demonstrate that the active shock absorber system in accordance with two types of the bee multi-objective algorithm has good performance in comparison with the passive approach to minimize the bounce displacement and momentum, the pitch displacement and momentum, the suspension travel and impact force in time-domain and frequency-domain by using signal processing, that results in improvement of passenger ride comfort importantly. As well as, enhancement of structure's fatigue life is a likely case as a consequence of study applicable to the industry. [ABSTRACT FROM AUTHOR]

The maximum horizontal impact load experienced by an aircraft's landing gear wheel during landing is an important parameter in the landing gear's safety design and performance analysis. Using a noncontact photoelectric testing method, this paper experimentally obtained the temporally varying data of the instantaneous rotational speed for an aircraft wheel at the instant of its contact with the test platform. Moreover, the kinetic relationship between the transient rotational speed of the aircraft's wheel and the horizontal impact force was established. According to the temporally varying data measured from the transient rotational speed of the aircraft's wheel, the maximum horizontal impact load at the instant the aircraft contacted the platform was calculated. To verify the accuracy of this method in which changes in rotational speed of the aircraft's wheel determine the horizontal impact load, verification equipment without lateral constrains was designed and used for testing. The experimental results showed that the horizontal impact load determined based on the transient rotational speed of the aircraft's wheel are consistent with the results obtained using direct measurements obtained from custom-made equipment free of lateral constrains. This paper provides a new experimental method for measuring the horizontal impact load on the aircraft's wheel. [ABSTRACT FROM AUTHOR]

Oleo-damping performance is a key factor affecting the landing gear buffer performance, while the flow discharge coefficient determines buffer damping force. For improving the calculation precision of discharge coefficient estimation method in aircraft design manual, a model for discharge coefficient is established based on pipeline fluid mechanics and damping orifice structure, and a numerical calculation is performed. Computational fluid dynamics (CFD) analysis is also conducted for damping orifice structure using the commercial software FLUNET. The simulation result of damping orifice discharge coefficient correlates well with the theoretical result. On this basis, landing gear drop dynamic response are calculated with the numerical analysis method using obtained discharge coefficient and compared with experimental results. Furthermore, the influences of current discharge coefficient estimation method and simulation method are analyzed and compared on the hydraulic force and the ground reaction force. The study demonstrates that the poor precision of discharge coefficient estimation method in aircraft design manual leads to more than 30 % differences between the drop dynamic estimation results and the experimental results. The method of CFD simulation or theoretical analysis can improve the calculation precision of discharge coefficient by about 17 %. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to investigate the possibilities and determination of hot and warm forging of ultrahigh-strength steel 300M and subsequent quenching with accelerated air. Analysis of microstructure and mechanical properties of forged steel 300M focused on investigation of the effect of processing conditions on final properties, such as strength, impact strength and hardness, taking into consideration temperature gradients and within-part strain nonuniformity occurring in forging and direct cooling of aircraft landing gear.Design/methodology/approach The research involved semi-industrial physical modeling of hot deformation and direct cooling, aided with numerical analysis of both deformation and kinetics of phase transformations on cooling, with process conditions determined on the basis of numerical simulation of industrial process. Examination of forged and quench-tempered samples involved testing mechanical properties (tensile properties, hardness and impact strength) and microstructure.Findings Three major findings were arrived at: first, assessment of the effects of energy-saving method of cooling conducted directly after forging. Second, tensile properties, hardness and impact strength, were analyzed on the background of microstructure evolution during hot-forging and direct cooling; hence, applied temperature and cooling rates refer to actual condition of the material including varied deformation history. Third, the accelerated air cooling tests were carried out directly after forging with accurately measured and described cooling efficiency, which enabled the acquisition of data for heat treatment simulation with use of untypical cooling media.Research limitations/implications The conclusions formulated on the strenght of studies carried out in semi-industrial conditions with the use of model samples, despite strain and strain rate similarity, wait for full-scale verification in industrial conditions. The direct cooling tests carried out in semi-industrial conveyor Quenchtube are of cognitive value. Industrial realization of the process for the analyzed part calls for special construction of the cooling line and provision of higher cooling rate for heavy sections.Practical implications The results present microstructure properties’ relations for good-hardenability grade of steel, which is representative of several similar grades used in aircraft industry, which can support design of heat treatment (HT) cycles for similar parts, regardless of whether direct or conventional quenching is used. As they illustrate as-forged and direct-cooled microstructure and resultant mechanical properties, the studies concerning processing the steel of areas of lower temperature are transferable to warm forging processes of medium-carbon alloy steels. The geometry of the part analyzed in the case study is typical of landing gear of many aircrafts; hence, there is the high utility of the results and conclusions.Social implications The direct heat treatment technologies based on utilization of the heat attained in the part after forging allow significant energy savings, which besides cost-effectiveness go along with ecological considerations, especially in the light of CO2 emission reduction, improving economical balance and competitiveness. The presented results may encourage forgers to use direct cooling, making use of the heat attained in metal after hot forging, for applications to promote environmentally friendly heat treatment-related technologies.Originality/value Direct heat treatment typically seems to be reserved for micro alloyed steel grades and sections small enough for sufficient cooling rates. In this light, taking advantage of the heat attained in forged part for energy-saving method of cooling based on direct quenching as an alternative to traditional Q&T treatment used with application to relatively heavy sections is not common. Moreover, in case the warm-work range is reached in any portion of the forged part, effect of direct cooling on warm-forged material is addressed, which is a unique issue to be found in the related studies, whereas in addition to warm forging processes, the results can be transferable to coining, sizing or shot peening operations, where gradient of properties is expected. [ABSTRACT FROM AUTHOR]

Aircraft landing gear assemblies comprise of various subsystems working in unison to enable functionalities such as taxiing, take-off and landing. As development cycles and prototyping iterations begin to shorten, it is important to develop and improve practical methodologies to meet certain design metrics. This paper presents an efficient methodology that applies high-fidelity multi-disciplinary design optimization techniques to commercial landing gear assemblies, for weight, cost, and structural performance by considering both structural and dynamic behaviours. First, a simplified landing gear assembly model was created to complement with an accurate slave link subassembly, generated based of drawings supplied from the industrial partner, Safran Landing Systems. Second, a Multi-Body Dynamic (MBD) analysis was performed using realistic input motion signals to replicate the dynamic behaviour of the physical system. The third stage involved performing topology optimization with results from the MBD analysis; this can be achieved through the utilization of the Equivalent Static Load Method (ESLM). Lastly, topology results were generated and design interpretation was performed to generate two designs of different approaches. The first design involved trying to closely match the topology results and resulted in a design with an overall weight savings of 67%, peak stress increase of 74%, and no apparent cost savings due to complex features. The second design focused on manufacturability and achieved overall weight saving of 36%, peak stress increase of 6%, and an estimated 60% in cost savings. [ABSTRACT FROM AUTHOR]

In this paper, a new methodology supporting the design of landing gears is proposed. Generally, a preliminary step is performed with simplified FE model, usually one-dimensional, to achieve the reaction forces involving each component during all aforementioned aircraft operations. Though this approach gives a valid support to the designer, it is characterized by several problems, such as the related approximations. So, it is important, by a numerical point of view, to develop an isostatic FE model equivalent to the real one. In fact, if the landing gear is modelled as hyperstatic, the static equilibrium equations are insufficient for determining the internal forces and reactions on each sub-component; so, the modelled material properties and geometries assume an increasing importance, which gets the model too approximating. The proposed methodology consists of achieving the reaction forces by means of multibody simulations, by overcoming such problems, since each component is modelled as rigid. In this paper, also a FE model for the investigation of the structural response is proposed. Aimed to Certification by Analysis purposes, the developed multibody and the FE models have been assessed against an experimental landing gear drop test carried out by Magnaghi Aeronautica S.p.A., according to the EASA CS 25 regulations. [ABSTRACT FROM AUTHOR]

The Ground Based Augmentation System (GBAS) is a landing system for aircraft based on differential corrections for the signals of Global Navigation Satellite Systems (GNSS), such as GPS or Galileo. The main impact on the availability of current single frequency systems results from the necessary protection against ionospheric gradients. With the introduction of Galileo and the latest generation of GPS satellites, a second frequency is available for aeronautical navigation. Dual frequency methods allow forming of ionospheric free combinations of the signals, eliminating a large part of the ionospheric threats to GBAS. However, the combination of several signals increases the noise in the position solution and in the calculation of error bounds. We, therefore, developed a method to base positioning algorithms on single frequency measurements and use the second frequency only for monitoring purposes. In this paper, we describe a detailed derivation of the monitoring scheme and discuss its implications for the use in an aviation context. [ABSTRACT FROM AUTHOR]

Shimmy vibration is the oscillatory motion of the fork–wheel assembly about the steering axis. It represents one of the major problem of aircraft landing gear because it can lead to excessive wear, discomfort as well as safety concerns. Based on the nonlinear model of the mechanics of a single wheel nose landing gear (NLG), electromechanical actuator and tire elasticity, a robust active controller capable of damping shimmy vibration is designed and investigated in this study. A novel Decline Population Swarm Optimization ( P D SO ) procedure is introduced and used to select the optimal parameters for the controller. The P D SO procedure is based on a decline demographic model and shows high global search capability with reduced computational costs. The open and closed loop system behavior is analyzed under different case studies of aeronautical interest and the effects of torsional free play on the nose landing gear response are also studied. Plant parameters probabilistic uncertainties are then taken into account to assess the active controller robustness using a stochastic approach. [ABSTRACT FROM AUTHOR]

To provide taxi capability without the use of engines or tractor, electric landing gear drive is considered as a potential system add-on. Driving torque and nose wheel steering angle controller are established which are verified by civil aircraft examples. Quasi-steady method is applied to calculate tire forces and moments. The ground steering response of aircraft is simulated, and then different taxi conditions including powered nose wheel mode and powered main wheel mode are compared. Two conclusions are obtained: Electric taxi system helps the aircraft turn on the spot and the turning radius is smaller than the aircraft using engines; differential powered main wheel mode has the minimum turning radius while turning-circle with uniform velocity, and it has smaller difference between two vertical loads of main landing gear than powered nose wheel mode. [ABSTRACT FROM AUTHOR]

Existing high-strength low-alloy steels have been in place on landing gear for many years owing to their superior strength and cost performance. However, there have been major advances in improving the strength of high-performance corrosion-resisting steels. These materials have superior environmental robustness and remove the need for harmful protective coatings such as chromates and cadmium now on the list for removal under REACH legislation. A UK government-funded collaborative project is underway targeting a refined specification Custom 465 precipitation hardened stainless steel to replace the current material on Airbus A320 family aircraft main landing gear, a main fitting component developed by Messier-Bugatti-Dowty. This is a collaborative project between Airbus, Messier-Bugatti-Dowty, and Carpenter Technology Corporation. An extensive series of coupon tests on four production Heats of the material have been conducted, to obtain a full range of mechanical, fatigue, and corrosion properties. Custom 465 is an excellent replacement to the current material, with comparable tensile strength and fracture toughness, better ductility, and very good general corrosion and stress corrosion cracking resistance. Fatigue performance is the only significant area of deficit with respect to incumbent materials, fatigue initiation being often related to carbo-titanium-nitride particles and cleavage zones. [ABSTRACT FROM AUTHOR]

The multi-copter UAV landing gear is used for ground station and shock damping for landings. The materials used in the construction of landing gears are selected by using a simple criterion: minimal mass versus maxim resistance at shocks. Article contains an evaluation of a kinematics mechanism quadrilateral landing gear is mounted on a multicopter. [ABSTRACT FROM AUTHOR]

In this paper, in order to reduce a landing gear vibration two adaptive control systems are designed considering the landing and taxi phases. For this purpose, 6 degree of freedom equations of motion of the landing gear and the related transfer functions are extracted. A reduced order model of the overall transfer functions are given as a result of complicated dynamic model. A Lyapunov based model reference adaptive control is designed to absorb the vibration of front wheel of the landing gear at touchdown. In addition, a minimum variance adaptive controller is designed and implemented on the system to reject the band level disturbances during the taxi phase. The band disturbances are modeled as a colored Gaussian noise and the system parameters as well as noise characteristics are estimated using extended least square approach. Both control systems are investigated to assess the best performance. Numerical simulations of the system in Matlab/Simulink environment show the preferences and satisfactory performances of the proposed vibration control systems. These results are calculated against various inputs including model reference adaptive control and minimum variance approaches [ABSTRACT FROM AUTHOR]

The article focuses on the landing gear design and maintenance analysis for shimmy during takeoff and landing. It describes a concise method for the analysis of nonlinear shimmy and uses it to suggest guidelines for landing gear design and maintenance. The nonlinear analysis consists of harmonic balance (HB) and perturbation methods.

A paper which explored the corresponding aeroacoustic measurements of a scaled rudimentary landing gear (RLG) model that was used as the benchmark data for the second American Institute of Aeronautics and Astronautics (AIAA) Benchmark Problems for Airframe Noise Computations workshop (BANC-2) is presented. Topics covered include model design and fabrication, and linear microphone array distance scaling and directivity.

The main advantages of magneto-rheological buffer system for aircraft landing gear are adjustable damping force, simple structure and independent of external energy. A kind of magneto-rheological damper structure for aircraft landing gear was presented in this paper. The state equation was established and the landing buffer system control strategy was designed based on self-made magneto-rheological landing impact platform. Integrating with model predictive control, a semi-active control method was studied and used it in realizing the adaptive magneto-rheological buffer system landing process. It has been proved in practice that the proposed control method fully considered the boundless of output damping force. The problem of balancing between landing and taxiing, which is caused by un-adjustable passive damping force in the working process of oleo-pneumatic buffer system, is solved. [ABSTRACT FROM AUTHOR]

This paper presents a steady-state concept model for studying the thermal behavior of a greased aircraft landing gear lower slider bearing. Structural damage has been reported as a consequence of excessive heat generated by the high loads induced by rough runways on the bearings, and by the high sliding velocities of the piston. The goal of the model is to enable fundamental understanding of the frictional heat generation. The governing equations are adapted for grease flow and special attention is given to the underlying algorithm of the developed numerical framework used to efficiently solve the governing equations. The developed numerical code is validated against existing results. Numerical results indicate fundamental differences in fluid flow behavior between greased and oil-lubricated bearings. [ABSTRACT FROM AUTHOR]

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The landing dynamic modeling technology for aircraft landing gear is based on accurate evaluation of the landing gear landing performance. Aiming to study the post landing gear, a model for dynamic analysis of the gear is established based on the analysis of the structure mechanical features and the characteristics of landing dynamic performance. The landing dynamic analysis of strut landing gear is conducted by using LMS Motion software. According to the comparative analysis between simulation and drop test, the dynamic modeling method is accurate and reasonable. To obtain the load distribution of each landing gear, a full aircraft model of multi-strut landing gear is built, and then the dynamic simulation analysis is carried out in different landing process. The study shows that the rear main landing gear bears the highest proportion of load. The initial pitch angle influences load distribution of each landing gear. A lateral force is exerted on the main landing gear tire, when the plane is landing asymmetrically. With landing condition becoming stable, the lateral force is eliminated. [ABSTRACT FROM AUTHOR]

A model of a three-dimensional dual-sidestay landing gear mechanism is presented and employed in an investigation of the sensitivity of the downlocking mechanism to attachment point deflections. A motivation for this study is the desire to understand the underlying nonlinear behavior, which may prevent a dual-sidestay landing gear from downlocking under certain conditions. The model formulates the mechanism as a set of steady-state constraint equations. Solutions to these equations are then continued numerically in state and parameter space, providing all state parameter dependencies within the model from a single computation. The capability of this analysis approach is demonstrated with an investigation into the effects of the aft sidestay angle on retraction actuator loads. It was found that the retraction loads are not significantly affected by the sidestay plane angle, but the landing gear's ability to be retracted fully is impeded at certain sidestay plane angles. This result is attributed to the landing gear's geometry, as the locklinks are placed under tension and cause the mechanism to lock. Sidestay flexibilities and attachment point deflections are then introduced to enable the downlock loads to be investigated. The investigation into the dual sidestay's downlock sensitivity to attachment point deflections yields an underlying double-hysteresis loop, which is highly sensitive to these deflections. Attachment point deflections of a few millimeters were found to prevent the locklinks from automatically downlocking under their own weight, hence requiring some external force to downlock the landing gear. Sidestay stiffness was also found to influence the downlock loads, although not to the extent of attachment point deflection. [ABSTRACT FROM AUTHOR]

Under certain conditions during takeoff and landing, pilots may sometimes experience vibrations in the cockpit. Because the cockpit is located right above the nose landing gear, which is known to potentially be prone to self-excited vibrations at certain velocities, an explanation for those vibrations might be oscillations of the landing gear feeding into the fuselage. However, the fuselage dynamics itself may also influence the dynamics of the landing gear, meaning that the coupling must be considered as bidirectional. A mathematical model is developed to study a coupled nose-landing-gear-fuselage system, which allows to assess the overall influence of the coupling on the system dynamics. Bifurcation analysis reveals that this interaction may be significant in both directions and that the system behavior depends strongly on the modal characteristics of the fuselage. [ABSTRACT FROM AUTHOR]

A study is made into the occurrence of shimmy oscillations in a dual-wheel main landing gear. Nonlinear equations of motion are developed for the system, and various effects are considered, including gyroscopic coupling, nonlinear tire properties, geometric nonlinearities, and fluid shock damping. Of particular interest in this study is the presence of freeplay: this is introduced as a lateral play at the apex of the torque link joints. Using bifurcation analysis methods, the dynamics of this system are explored as the forward velocity and loading force acting on the gear are varied. For the zero freeplay case, the system is found to be stable over its physical operating range with shimmy oscillations appearing only for extreme loading forces and speed. However, with the introduction of freeplay, shimmy may be observed over more typical operating conditions, and the resulting oscillations are found to scale linearly with freeplay magnitude. The parameter plane of forward velocity and loading force is then further subdivided into areas of different types of dynamics. With the inclusion of freeplay one observes the appearance of low-frequency and high- frequency shimmy oscillations, bistable behavior, and stationary solutions of nonzero yaw. Considering the desirable case in which no shimmy occurs, the set of allowable freeplay profiles that satisfy a conservative stability criteria is defined. [ABSTRACT FROM AUTHOR]

Longitudinal deck motion causes the variation of the height of ideal touch down point, which is a main factor affecting the safety of carrier landing. In order to decrease the influences of longitudinal deck motion on carrier landing, a method of deck motion prediction and compensation is proposed. Deck motion compensator based on lead network and deck motion predictor based on particle filter are designed. The deck motion signal is first processed by the predictor and compensator and then connected to the longitudinal automatic carrier landing system, which helps the carrier aircraft track the deck motion accurately in the final stage of landing and decreases the influences of deck motion on carrier landing. The designed compensator and predictor are examined and compared with other method through simulation experiments in different sea states. Simulation results show that the designed deck motion predictor and compensator can effectively compensate for the landing error caused by deck motion and can significantly improve the safety and accuracy of carrier landing. [ABSTRACT FROM AUTHOR]

Full-wave EM simulation techniques such as finite-difference time domain (FDTD) are generally used for the calculation of lightning-induced current redistribution on complex 3-D geometries. For slow lightning waveforms, such techniques are not compatible with sensitivity analysis due to heavy preprocessing and calculation constraints. As an alternative, this paper presents an equivalent electric circuit method in which the 3-D geometry is described by conductive segments only on which resistance, self-inductance, and mutual inductance are calculated with analytical formulas. Here, this method, once known as “stick model” method, has been applied for the calculation of the lightning-induced currents on an A320 aircraft landing gear. The results have been compared with an FDTD simulation and with laboratory measurements. They demonstrate that the overall simulation cost is extremely reduced compared to FDTD while they maintain the same degree of accuracy. This paper shows how this equivalent circuit method is appropriate for design processes in which parametric calculations performed in a reasonable time are required. [ABSTRACT FROM PUBLISHER]

Modern tailless delta wing aircraft is built for high performance with light weight leading to structural flexibility. During landing, high vertical sink rate of aircraft causes peak transient loads in and around the landing gear attachment locations. These reactions forms the load cases for local sizing of airframe and its responses determine the overall integrity. This paper describes the co-simulation approach to carry out the dynamic landing analysis on a flexible tailless delta wing aircraft and examines the responses at certain critical locations such as the tip of wings, fin and nose for nominal landing conditions. The reactions are obtained from the Landing gear supplier through MSC Adams multi-body dynamic simulation of full aircraft with non-linear stiffness and damping models of Nose and Main landing gear systems. The landing response analysis is carried out on a flexible aircraft using industry standard MSC Nastran as transient dynamic problem with base enforced motion. It is observed that the regions that are farther located such as wing, fin and nose tips are susceptible to get excited at their inherent modes thereby picking up intense responses. This co-simulation approach of solving the transient dynamic analysis from the force response of multi-body simulation provides the specifications very early in the design process and aids in structural dynamic checks before getting validated from the full fledged flight test. [ABSTRACT FROM AUTHOR]

Within the aerospace industry there is a desired paradigm shift to move aircraft maintenance towards offering maintenance programmes with predictive, rather than purely preventative, capabilities, which would utilise health monitoring technologies. This maintenance revolution will not just incorporate new technologies into key aircraft systems such as engines, wing/fuselage structures and landing gear, but would result in aircraft maintenance packages tailored towards individual customer requirements. The difficulties with incorporating health monitoring into systems do not just extend to the technical, but also require clear identification of a clear commercial business need. It is identified that the development of aerospace health monitoring systems offers a variety of often overlooked commercial challenges, which are required to be addressed to enable integration into often well-defined business practices. This paper provides a digest of recent research into the commercial challenges associated with the integration of health monitoring products into electromechanical actuation systems for aircraft landing gear. Discussions on current aircraft maintenance practice and how a move towards a predictive philosophy built upon health monitoring systems is likely to affect future maintenance operations are used to develop the business case for health monitoring within this application. Three proposed pricing strategies, which are aimed at formulating part of a business strategy, are reviewed, highlighting the need to carefully consider the impact of the new technology on business strategies before adopting them. These considerations of how a landing gear manufacturer would incorporate health monitoring systems integrated into their products are a fundamental part of health monitoring systems' integration and development. [ABSTRACT FROM AUTHOR]

A method of investigating quasi-static mechanisms is presented and applied to an overcenter mechanism and to a nose landing gear mechanism. The method uses static equilibrium equations along with equations describing the geometric constraints in the mechanism. In the spirit of bifurcation analysis, solutions to these steady-state equations are then continued numerically in parameters of interest. Results obtained from the bifurcation method agree with the equivalent results obtained from two overcenter mechanism dynamic models (one state-space and one multibody dynamic model), while a considerable computation time reduction is demonstrated with the overcenter mechanism. The analysis performed with the nose landing gear model demonstrates the flexibility of the continuation approach, allowing conventional model states to be used as continuation parameters without a need to reformulate the equations within the model. This flexibility, coupled with the computation time reductions, suggests that the bifurcation approach has potential for analyzing complex landing gear mechanisms. [ABSTRACT FROM AUTHOR]

A control system for the landing gear is described in terms of complex dynamic stiffness. An analysis of the shimmy boundaries using values of complex dynamic stiffness and taking into account the maximum possible perturbations permits finding the necessary parameters of the control system (such as dry friction) for the prevention of shimmy at low amplitudes. The universal description of the control system in terms of complex dynamic stiffness, easy and convenient analysis, and the possibility of analytic estimation and experimental determination of complex dynamic stiffness are indicative of practicability of this canonical description [ABSTRACT FROM AUTHOR]

Abstract: High speed flows inside cavities are encountered in many aerospace applications including weapon bays of combat aircraft as well as landing gear. The flow field inside these cavities is associated with strong acoustic effects, unsteadiness and turbulence. With increasing emphasis on stealth operation of unmanned combat air vehicles and noise concerns near airports, cavity flows attracted the interest of many researchers in aerodynamics and aeroacoustics. Several attempts were made using wind tunnel experimentation and computational fluid dynamics analyses to understand the complex flow physics associated with cavity flows and alleviate their adverse effects via flow control. The problem proved to be complex, and current research revealed a very complex flow with several flow phenomena taking place. With the aid of experiments, CFD methods were validated and then used for simulations of several cavity configurations. The detached-eddy and large-eddy simulation methods proved invaluable for these studies and their application highlights the need for advanced turbulence simulation techniques in aerospace. The success of these methods and a summary of the current status of the experimental and computational progress over the past twenty years is summarised in this paper. [Copyright &y& Elsevier]

The landing gears are systems of the aircrafts, designated to support the airplane when they rest on the ground, and provide the movement in takeoff, landing, and taxiing on the airfield. The paper presents a systematisation of these mechanisms, depending on its complexity. They can be simple mechanisms (one-loop); the compound obtained by the simple with addition of a dyad and complex, consisting of three or more contours. Such systematisation allows development of a method of a structural-kinematics synthesis of retractable landing gear mechanisms. [ABSTRACT FROM AUTHOR]