Landing Gear Research Articles

Shimmy vibration analysis of unmanned aircraft coupled with landing gears

Shimmy vibration analysis of unmanned aircraft coupled with landing gears

The Manufacturing Processes of Airbus A320 Landing Gear Bhushings Using Reverse Engineering Methods

The aviation sector is currently enjoying fast growth, as seen by the manufacture of 8,650 Airbus A320 aircraft. One critical component is the landing gear bushing (P/N 201160616), which provides safety and performance during takeoff and landing. PT. GMF AeroAsiaTbk is having difficulty obtaining these bushings due to low stock, configuration changes, and delivery delays. To address this, PT. GMF AeroAsiaTbk, through PMA Holder GMF Aero Asia, intends to produce bushings independently under the Parts Manufacturing Approval procedure outlined in CASR Part 21 Sub-Part K, with DGCA monitoring. Reverse engineering approaches are utilized to overcome technical information restrictions, allowing high-quality bushings to be produced. The research goals are to collect dimensional and material data, develop optimal production methods, and understand the electroplating process on bushings. The reverse engineering procedure entails taking measurements with a vernier calliper and a Coordinate Measuring Machine (CMM) as well as reviewing the Component Maintenance Manual. Preparation, fabrication, inspection, packing, and marking are all part of the production process. Bright cadmium electroplating is used to prevent corrosion and enhance appearance. The findings are expected to improve production efficiency, decrease downtime, and ensure the availability of dependable spare parts.

Stability Analysis of Nonlinear Models of Nose Landing Gear Shimmy

Stability Analysis of Nonlinear Models of Nose Landing Gear Shimmy

Stress Distribution Analysis using ANSYS of the Nose Landing Gear of STOL Aircrafts Considering Runway Gradient: A Simulation Study

Landing gear failures are a major cause of aircraft failures because they are an integral part of the aircraft's development. According to the Federal Aviation Administration (FAA), 50% of all aircraft failures occur during take-offs and landing. The landing gear of a short take-offs and landing (STOL) aircraft has had its static and dynamic forces analyzed analytically and numerically. SOLIWORKS is used to model the landing gear, and ANSYS is used to perform the numerical simulation results. Following it, the model is examined for stress and deformation with the boundary conditions and computed loads into account. This study uses structural finite element analysis (FEA) to analyze the nose gear's stress behavior and displacement during landing, as well as to assess the effect of the runway gradient. Utilizing a comprehensive numerical simulation, the landing gear of a real material Twin-Otter STOL aircraft has been demonstrated to be subjected to a dynamic force of 3653.26N, a pneumatic pressure of 1.59MPa, a bead pressure of 7.97MPa, and a vertical force of 1672.31lbs on level runways, or runways with no gradient. These findings will increase the level of confidence of aircraft manufacturers to make necessary appropriate design of STOL aircraft’s landing gear. It may can decrease the aircraft accidents and increase human life safety ultimately saving valuable time and resources too.

Design of Bionic Landing Gear with Multi-Link Mechanism for UAVs in Desert Terrain

The terrain in desert areas is rugged and uneven, lacking suitable landing points for unmanned aerial vehicles (UAVs). In addition, sand and dust in the desert can easily damage the internal circuits of propellers through vortexes. To address the high demands for hardness and smoothness of landing sites for vertical takeoff and landing (VTOL) aircraft, as well as the low level of intelligence of traditional landing gear, an optimized biomimetic leg-type terrain-adaptive landing gear based on a multi-link hybrid mechanism was developed for landing in desert areas. First, the design configuration of a single leg was optimized, and the length of each link was calculated accordingly, followed by motion simulations. Secondly, the overall design was developed, and slope landing simulations were conducted on the four-leg mechanism. Research results showed that the optimized multi-link hybrid mechanism terrain-adaptive landing gear was better suited for adapting to desert terrain and could land on sand dune slopes, effectively improving the adaptability of VTOL aircraft in desert areas.

A Structural Analytical Study on the Design Sensitivity of Skid Landing Gear for PAV

A Structural Analytical Study on the Design Sensitivity of Skid Landing Gear for PAV

Functional degradation reliability analysis for non-uniform wear of multi-rotating joints of mechanical structures

Failure of the aircraft landing gear lock mechanism can result in the inability of the aircraft to take off and land properly, and its failure can cause critical results. The aircraft lock mechanism is characterized by multiple joints. Based on the performance degradation phenomenon of the lock mechanism, a reliability analysis method of the lock mechanism with non-uniform wear of multiple joints is proposed, which takes into account the effect of non-uniform wear of multiple joints on the motion accuracy of the motion mechanism, and investigates the reliability analysis of the degradation of the angle of the lock hook and the calculation of the whole lifetime cycle. Firstly, the lock mechanism lock hook angle degradation eigenvolume model is established according to the functional principle of the lock mechanism. Secondly, the lock hook degradation angle is obtained by establishing the kinetic equations to calculate the non-uniform wear of each joint separately. Finally, the degradation path is fitted by the Wiener process to carry out the reliability analysis and the whole lifetime calculations. The results show that the proposed method is capable of providing maintenance strategies to meet the reliability requirements for the performance degradation of multi-joint kinematic mechanisms of mechanical systems.

Analysis of Taxiing Performance of Single Strut Landing Gear Based on ISD

In this paper, based on the “spring-damper” landing gear (SDLG), the inerter is introduced to form the “inerter-spring-damper” landing gear (ISDLG), and the taxiing dynamic models of both are established. Taking fuselage acceleration, buffer stroke and dynamic tire load as performance indexes, the parameters of ISDLG are optimized by using multi-objective genetic optimization algorithm. In MATLAB/Simulink environment, SDLG and ISDLG are simulated in time-domain and frequency-domain. The results show that compared with SDLG, the values of performance indexes of ISDLG are all reduced, especially at low frequency, which can effectively suppress the low frequency vibration of the fuselage and improve the ride comfort and handling stability of the aircraft when it is taxiing on the ground. In addition, through comparison, it is found that speed and road grade have different influences on aircraft taxiing performance, and road grade has the greatest influence, followed by speed.

Enhancing comprehensive properties of HVOF thermally sprayed WC-10Co coatings using two grain inhibitors

The industry widely uses WC coatings to protect vital machine parts, including industrial gas turbines, ball valves, and aircraft landing gear shafts. To enhance the comprehensive performance of WC-10Co cemented carbide coatings, this study added VC and Cr3C2 grain inhibitors to refine the WC particles. Two novel powder compositions, S1 (WC-10Co-2Cr3C2-2VC) and S2 (WC-10Co-2VC-2Cr) were developed using the spray granulation method, alongside a commercial WC-10Co-4Cr powder as a control. These coatings were applied to 316 stainless steel substrates using the HVOF technique and subjected to XRD, SEM, hardness, friction, and electrochemical analysis. The microstructures, phase compositions, and various properties of WC-10Co-2Cr3C2-2VC and WC-10Co-2VC-2Cr coatings were systematically investigated. The results indicate a significant reduction in decarburization and porosity in S1 and S2 coatings compared to the commercial WC-10Co-4Cr coatings. VC and Cr3C2 suppressed the Ostwald ripening phenomenon, leading to smaller WC particle sizes in S1 and S2 coatings. In terms of performance, WC-10Co-2Cr3C2-2VC exhibited the highest hardness and superior wear resistance, while the WC-10Co-2VC-2Cr coating displayed the lowest corrosion rate in a 5 wt% H2SO4 solution at 25 °C, all while maintaining excellent mechanical properties. This study opens potential directions for the creation of high-performance WC-based coatings.

Effect of clearance position of torque link structure on nose landing gear shimmy

The clearance of the torque link will affect the stability of landing gear shimmy. In this paper, a six-degree-of-freedom mathematical model of dual-wheel nose landing gear shimmy including longitudinal bending and axial displacement of the strut is established. The shimmy characteristics of five different positions of clearance at the central connecting pin of the lower torque link and connection between the lower torque link and the inner cylinder of the strut are analyzed by bifurcation diagram, limit cycle and time history diagram. The results show that: there is a clearance on both sides of the head of the lower torque link, compared with the clearance exists only on one side (left or right), the range of the torsional shimmy of the nose landing gear is larger; when there is a clearance on one side (left or right) near 2 mm at the connection between the lower torque link and the inner cylinder of the strut, the torsional shimmy appears a period doubling phenomenon.

Gear walk instability caused by brake-disc friction characteristics

A multi-body dynamic rigid-flexible coupling model of landing gear is established to study the gear walk instability caused by the friction characteristics of the brake disc. After validating the model with the experimental results, the influence of the landing gear structure and braking system parameters on gear walk is further investigated. Among the above factors, the slope of the graph for the friction coefficient of the brake disc and the relative velocity of brake stators and rotors is the most influential factor on gear walk instability. Phase trajectory analysis verifies that gear walk occurs when the coupling of multiple factors causes the system to exhibit an equivalent negative damping trend. To consider a more realistic braking case, a back propagation neural network method is employed to describe the nonlinear behavior of the friction coefficient of the brake disc. With the realistic nonlinear model of the friction coefficient, the maximum error in predicting the braking torque is less than 10% and the effect of the brake disc temperature on gear walk is performed. The results reveal that a more negative friction slope may contribute to a more severe unstable gear walk, and reducing the braking pressure is an effective approach to avoid gear walk, which provides help for future braking system design.

A probabilistic approach for acoustic emission based monitoring techniques: With application to structural health monitoring

It has been demonstrated that acoustic-emission (AE), inspection of structures can offer advantages over other types of monitoring techniques in the detection of damage; namely, an increased sensitivity to damage, as well as an ability to localise its source. There are, however, numerous challenges associated with the analysis of AE data. One issue is the high sampling frequencies required to capture AE activity. In just a few seconds, a recording can generate very high volumes of data, of which a significant portion may be of little interest for analysis. Identifying the individual AE events in a recorded time-series is therefore a necessary procedure for reducing the size of the dataset and projecting out the influence of background noise from the signal. In this paper, a state-of-the-art technique is presented that can automatically identify cluster the AE events from a probabilistic perspective. A nonparametric Bayesian approach, based on the Dirichlet process (DP), is employed to overcome some of the challenges associated with this task. Additionally, the developed model is applied for damage detection using AE data collected from an experimental setup. Two main sets of AE data are considered in this work: (1) from a journal bearing in operation, and (2) from an Airbus A320 main landing gear subjected to fatigue testing.

Application of Topology Optimization Method for Unmanned Aerial Vehicle Nose Landing Gear Fork

İniş takımı uçağın en önemli bileşenlerinden biridir. Uçağa gelen yükleri karşılamak, iniş anında darbeyi sönümlemek ve uçağın taksi yapmasına izin vermek iniş takımının görevleri arasındadır. İniş takımı, ana iniş takımı ve burun iniş takımından oluşur. Ana iniş takımı ve burun iniş takımı da kendi içinde alt bileşenlerden oluşur. Bu çalışmada burun iniş takımı alt bileşenlerinden olan çatal parçası için optimizasyon çalışması yapılmıştır. Optimizasyonun amacı, performansı ve tasarımı iyileştirmek, hafifletmek, talaş miktarını ve proses enerjisini azaltmaktır. Çatal parçasının optimizasyon çalışması için gerekli sınır koşulları verilerek, analiz ANSYS Workbench programında gerçekleştirilmiştir. Optimizasyondan sonra, analiz çalışmasında oluşan gerilme ve deformasyonlar optimizasyon öncesi sonuçlarla karşılaştırılarak çatal yapısı doğrulanmış ve yapısal değişiklikler oluşturularak ağırlık azaltılmıştır.

Considering lateral bending and torsion coupling in shimmy analysis of the nose landing gear

This paper focuses on the shimmy damper performance of nose landing gear and aims to establish and amend a five-dimensional dynamic model of nose landing gear. The study compares the shimmy damper performance of nose landing gear whether considering lateral bending and torsional vibrations coupling and concludes that the amended model provides greater accuracy. In addition, the research compares the shimmy performance of passive and active shimmy dampers, finding that the active shimmy damper significantly outperforms the passive one in terms of efficiency. The amended model is also shown to improve the shimmy damper performance of active shimmy damper.

The importance of experimental airframe noise research

Numerical methods progress rapidly in terms of capabilities and efficiency. Accordingly, one could conclude that experimental activities will sooner or later disappear. In this context the paper will exemplify the use of numerical methods for the proper design and conduct of wind tunnel experiments. Examples will cover the research topics on high lift system's aero-acoustic and landing gear noise. Finally, the paper will describe the development of selected noise reduction concepts from their first experimental assessment in wind tunnels up to being flight tested.

Toward Airframe Noise Reduction for Passenger Aircraft

Airframe noise is one of the main noise sources of the latest passenger aircraft during the approach phase. To demonstrate noise reduction technology based on unsteady Computational Fluid Dynamics (CFD) and wind tunnel tests, JAXA conducted flight tests using the JAXA Experimental Aircraft "Hisho" in 2016 and 2017 in cooperation with industries in Japan. The noise data obtained from flyover noise source measurements successfully showed consistent characteristics with the noise reduction designs for the flaps and the main landing gear. The noise measurement data from the flight test 2017 were used to validate the wind tunnel tests and CFD used in the design phase. Subsequently, the research activities proceeded towards the research and development targeting regional jet aircraft, aiming for practical application in passenger aircraft. This paper overviews these research activities toward developing airframe noise reduction technology for passenger aircraft.

Analytical Study on the Strength of Skid Landing Gear for PAV

Analytical Study on the Strength of Skid Landing Gear for PAV

Analysis of Catapult-Assisted Takeoff of Carrier-Based Aircraft Based on Finite Element Method and Multibody Dynamics Coupling Method

Catapult-assisted takeoff is the initiation of flight missions for carrier-based aircrafts. Ensuring the safety of aircrafts during catapult-assisted takeoff requires a thorough analysis of their motion characteristics. In this paper, a rigid–flexible coupling model using the Finite Element Method and Multibody Dynamics (FEM-MBD) approach is developed to simulate the aircraft catapult process. This model encompasses the aircraft frame, landing gear, carrier deck, and catapult launch system. Firstly, reasonable assumptions were made for the dynamic modeling of catapult-assisted takeoff. An enhanced plasticity algorithm that includes transverse shear effects was employed to simulate the tensioning and release processes of the holdback system. Additionally, the forces applied by the launch bar and holdback bar, nonlinear aerodynamics loads, shock absorbers, and tires were introduced. Finally, a comparative analysis was conducted to assess the influence of different launch bar angles and holdback bar fracture stain on the aircraft’s attitude and landing gear dynamics during the catapult process. The proposed rigid–flexible coupling dynamics model enables an effective analysis of the dynamic behavior throughout the entire catapult process, including both the holdback bar tensioning and release, takeoff taxing, and extension of the nose landing gear phases. The results show that higher launch bar angle increase the load and extension of the nose landing gear and cause pronounced fluctuations in the aircraft’s pitch attitude. Additionally, the holdback bar fracture strain has a significant impact on the pitch angle during the first second of the aircraft catapult process, with greater holdback bar fracture strain resulting in larger pitch angle variations.

Contact resonance atomic force microscopy using long elastic tips

In this work, a new theoretical model for contact resonance atomic force microscopy, which incorporates the elastic dynamics of a long sensing tip is presented. The model is based on the Euler–Bernoulli beam theory and includes coupling effects from the two-beam structure, also known as an ‘L-shaped’ beam in the literature. Here, high-accuracy prediction of the sample stiffness, using several vibration modes with a relative error smaller than 10% for practical working ranges, is demonstrated. A discussion on the model’s capability to predict the dynamic phenomena of eigenmode veering and crossing, as the force applied to the sample increases, is presented. The L-shaped beam model presented here is also applicable for structural applications such as: micro-electro-mechanical systems, energy harvesting, and unmanned aerial vehicle landing gear.

Numerical Study on the Unusual Vibration Load Characteristics and Mechanisms of the Front Landing Gear Compartment

Civilian aircraft can experience noticeable vibrations in the cockpit and cabin due to mechanical faults during flight. To address this issue, a hybrid approach was utilized to investigate fluid-induced vibration load characteristics in the front landing gear compartment under different hatch opening angles. The results reveal that the root mean square (RMS) of cumulative pressure loads on both small and large hatches under different opening angles is largest at a 15°. For all the simulated cases (0°, 5°, 10°, 15°, 20°), the power spectral density (PSD) results of the chosen monitoring points on the inner wall of the large hatch exhibit broadband frequency characteristics, and the peak PSD values for the chosen monitoring points on the outer wall of the small hatch exhibit a significant concentration of energy at approximately 75 Hz. The peak PSD values for the selected monitoring points on the inner wall of the small hatch demonstrate a more uniform distribution of energy. Utilizing the iso-surface of Q-criterion, spatial streamlines, and streamlines at different cross-sections to analyze flow characteristics, the study investigates the fluctuating load mechanisms of the compartments. The results indicate that unsteady loads stem from the blunt edges of the hatches, which induce unsteady flow and spanwise flow. Geometric gaps between different locations cause flow separation, and the flows inside the compartment exhibit characteristics similar to those of a clean cavity. Furthermore, the mutual interference can be described using circulating flow and spanwise flow, resulting in flow unsteadiness. The flow separation zones enlarge and vortex intensity increases with the increase of the hatch opening angle from 0° to 15°; then, their values decrease as the hatch opening angle increases from 15° to 20°. These variations explain the maximum RMS of cumulative pressure loads at 15°.