Showing papers on "Landing gear published in 2022"

Development of a typical structural diagram of the hydraulic system of short-haul passenger aircraft

Abstract: The article develops a typical structural diagram of the hydraulic system of short-haul passenger aircraft, obtained on the basis of an analysis of the hydraulic system diagrams of aircraft of this class. This made it possible to carry out a generalized calculation of the required energy characteristics of consumers and the system as a whole for the modes: takeoff, flight and landing, as well as to develop a kinematic diagram and calculate the hydraulic cylinder-lift of the front landing gear. Also in the article, a verification calculation of the cylinder for stability in the supportive position of the rod for compression was carried out.

Simulation of Runway Irregularities in a Novel Test Rig for Fully Electrical Landing Gear Systems

Abstract: The E-LISA research project, under way within the Clean Sky 2 framework, has the objective of developing an innovative iron bird dedicated to executing tests on the landing gear of a small aircraft transport equipped with an electro-mechanical landing gear and electrical brake. Such tests include the simulation of complete landing procedures under different operating conditions such as runway friction, presence of periodical defects along the runway, variable aircraft weight, and approach speed. To this end, the iron bird requires novel solutions in both its architecture and its control scheme. This paper details an innovative solution that is being implemented in the E-LISA iron bird to enable the execution of tests on a landing gear, reproducing the effects of any type of runway irregularity. First, the rig architecture is presented in detail, with particular care toward the hybrid position/force control system that manages its operations. Then, a simulation model is introduced with the objective of verifying the control system stability and the test rig capability to reproduce on the test articles the effects produced on the landing gear leg of periodical runway irregularities. Simulations results are presented, highlighting the stability of the proposed control scheme and providing a preliminary assessment of the system performances.

Predicting the Remaining Useful Life of Landing Gear with Prognostics and Health Management (PHM)

Abstract: Landing gear is an essential part of an aircraft. However, the components of landing gear are susceptible to degradation over the life of their operation, which can result in the shimmy effect occurring during take-off and landing. In order to reduce unplanned flight disruptions and increase the availability of aircraft, the predictive maintenance (PdM) technique is investigated in this study. This paper presents a case study on the implementation of a health assessment and prediction workflow for remaining useful life (RUL) based on the prognostics and health management (PHM) framework of currently in-service aircraft, which could significantly benefit fleet operators and aircraft maintenance. Machine learning is utilized to develop a health indicator (HI) for landing gear using a data-driven approach, whereas a time-series analysis (TSA) is used to predict its degradation. The degradation models are evaluated using large volumes of real sensor data from in-service aircraft. Finally, the challenges of implementing a built-in PHM system for next-generation aircraft are outlined.

Remaining-Useful-Life prognostics for opportunistic grouping of maintenance of landing gear brakes for a fleet of aircraft

Abstract: Several studies have proposed Remaining-Useful-Life (RUL) prognostics for aircraft components in the last years. However, few studies focus on integrating these RUL prognostics into maintenance planning frameworks. This paper proposes an optimization model for opportunistic maintenance scheduling of aircraft components that integrates RUL prognostics and that groups the maintenance of these components to reduce costs. We illustrate our approach for the maintenance of a fleet of aircraft, each equipped with multiple landing gear brakes. RUL prognostics for the landing gear brakes are obtained using a Bayesian regression model. Based on these RUL prognostics, we group the replacement of brakes using an integer linear program. As a result, we obtain a cost-optimal RUL-driven opportunistic-maintenance schedule for the brakes of a fleet of aircraft. Compared with traditional maintenance strategies, our approach leads to a reduction of up to 20% of the total maintenance costs.

Airframe noise predictions using the Ffowcs Williams-Hawkings equation

Abstract: This paper considers potential sources of error when using the Ffowcs Williams-Hawkings equation to make predictions of airframe noise, which entails a relatively low-speed, uniform incoming flow encountering geometry of varying complexity. Numerical simulations are used to investigate several model problems where Ffowcs Williams-Hawkings integration surfaces are placed on solid surfaces as well as in the flow. Comparisons with the pressure obtained directly from the simulations reveal that when solid surfaces are used, the acoustic calculations can produce erroneous results in upstream directions and when scattering bodies block the line of sight from observers to the source. Using solid surface input data implies ignoring all volumetric source effects, which include noise generation as well as flow effects. Nonuniform flow alone, such as is found in a steady boundary layer, was not found to be a significant source of error, so the amplitude and phase changes induced by turbulent eddies in massively separated flow regions is speculated to be the primary cause of the error.

Landing gear failures connected with high-pressure hoses and analysis of trends in aircraft technical problems

Abstract: Reliability and maintenance analysis in aviation industry focused on a main objective of the accident and incident investigations what are help to better understand the causes of accidents. In the article suggested the underlying concept by scorecard of situations what lead to aviation accidents. In the present research, the aviation accident connected with a landing gear and a problem of failure to follow maintenance instructions during a maintenance on aircraft landing gear hydraulic drive was under an investigation, on an example of root cause analysis of the failure of hydraulic flexible highpressure hoses. The approach presented in this research of experimental measurements, based on fluid pressure measuring, high-pressure hoses vibration measuring and frequency’s analysis. By spectrum analyses was found that high-pressure hoses are most susceptible to deformation at frequencies to the response of the fluid within, as well as at hoses material resonance frequencies. The compact version of hoses is more deformational on the resonance points than a standard version of hose. In final according to analyses, was established that disrespect of the frequency conditions was leaded to causes irreversible degradation changes of the hose inner structure and occurrence of material defects inside layers contact what lead in final step to hose failure.

Flow Control and Passive Low Noise Technologies for Landing Gear Noise Reduction

Abstract: This paper examines the use of both flow control and passive low noise technologies to reduce the aerodynamic noise radiated from a modified LAGOON landing gear, as tested in the EU funded H2020 collaborative research project: INVENTOR, InnoVative dEsign of iNstalled airframe componenTs for aircraft nOise Reduction. At approach to landing, landing gear noise is still a significant contributor to environmental noise in the vicinity of airports. Progress is being made with ambitious projects which aim to develop significantly reconfigured aircraft architectures to reduce airframe noise. The current project examines noise abatement measures which could be retrofit to existing landing gear configurations. Flow control in the form of low TRL "air curtains" which form a fluidic shield or virtual fairing are examined. Amongst the most interesting passive solutions are a selection of higher TRL porous materials in the form of wire mesh, perforated plates and 3D materials. In order to provide a simplified baseline landing gear mock-up on which to test the low noise technologies, the LAGOON NLG is modified with the addition of a torque-link and brakes and is called the "LAGOON-SLG". The porous materials are assessed experimentally in the A-Tunnel aeroacoustic facility in TU Delft, the Netherlands and the air curtains are examined in DLRs AWB aeroacoustic facility in Braunschweig, Germany.

Structural FEM Analyses of a Landing Gear Testing Machine

Abstract: The “Electro-mechanical Landing gear system Integration for Small Aircraft” (E-LISA) research project has the objective of developing an innovative “iron bird”, a testing facility dedicated to executing tests on an innovative landing gear of a small aircraft. This document presents the structural analyses of this complex testing machine performed with the Finite Element Method (FEM). Key purposes of these numerical simulations were the quantifications of the stress and displacement fields under the loading conditions foreseen for the machine. A modal analysis was performed with the aim of calculating eigenvalues and eigenvectors useful to provide an assessment of the structural dynamic response. The most critical mode shapes and the related frequencies were calculated, and the potentially critical rotational speeds were quantified. Finally, the Peak Stress Method (PSM) was adopted to quantify the fatigue resistance of the most critical weldments and an infinite fatigue life was assessed for the most critical one. The design of the machine, which is currently under manufacturing, was validated by the structural analyses presented here.

Health Assessment of Landing Gear Retraction/Extension Hydraulic System Based on Improved Risk Coefficient and FCE Model

Abstract: The health of the landing gear retraction/extension(R/E) hydraulic system may be assessed using fuzzy comprehensive evaluation (FCE), however the traditional FCE method depends solely on human assessment by specialists, which is excessively subjective. To address the issue of excessive human subjective variables in the assessment, an improved FCE model based on enhanced risk coefficient is provided, which includes four consideration indexes: failure probability, failure severity, failure detection difficulty, and failure repair difficulty. To reduce subjective human judgment errors entirely due to expert experience, the improved FCE takes into account the likelihood of failure using a statistical method, the severity of failure using a fault simulation analysis based on the LMS Imagine.Lab AMESim simulation platform, and the difficulty of fault detection and repair using the aircraft manufacturer’s professional maintenance information. As part of the evaluation model, the range of health assessment values and accompanying treatment methods are included, making it easier to implement on a daily basis in aircraft maintenance. As a final step, the simulation is evaluated, and the simulated faults are calculated.

Double Hybrid Tailsitter Unmanned Aerial Vehicle With Vertical Takeoff and Landing

Abstract: We propose a new double-hybrid concept and architectural design of a tailsitter unmanned aerial vehicle with vertical takeoff and landing capability. Basically, it consists of a modified flying wing with a single combustion powertrain set and a multirotor with 2 powertrain sets with electric motors. With the electric propellers fixed at the leading wing edge, the tailsitter has two standard surfaces for elevation control and two vertical stabilizers that are used to give the necessary direction on vertical takeoff and landing. We have designed, built, and tested a prototype based on this new double-hybrid concept, which spends less energy on vertical taking off and landing and also on horizontal flight, thus maximizing flight endurance and travelled distance. We performed several experimental tests starting with the aircraft on the ground in vertical positioning. These tests include executing vertical takeoffs and landing, transitions from vertical to horizontal flight modes and transitions back (from horizontal to vertical), and hovering, which were carried out successfully. Transitions fourth and back from combustion to multirotor are inherent to some of those flight mode transitions, which have also been performed smoothly. We also performed tests (in bench) to estimate the maximum flight duration, which has demonstrated about 32 minutes of endurance. To this end, the proposed and currently built double-hybrid prototype has proven to be functional as an effective hybrid UAV system.

Crashworthiness Analysis on Multiple Styles of Skid Landing Gear

Abstract: The skid landing gear is widely used in rotorcraft with advantages over wheeled landing gear. Crashworthiness is critical for protecting crews from injury in an emergency landing and landing gear plays a considerable important role in crashworthiness because it is the first structure hitting the ground. Hence the crashworthiness of four styles of skid landing gear with various thicknesses of the crossbeam or struts were numerically analyzed by using the finite element code LS-DYNA. The results show Bow style has the best comprehensive crashworthiness performance while the Strut style and Arc style have fair crashworthiness performance, but the Oct style has the largest weight, acceleration peak, and the lowest energy absorption ratio, which shows the worst crashworthiness. Also, further optimization with a tapered crossbeam design was conducted and evaluated, finding that the weight can be significantly reduced with the same level of crashworthiness.

Landing Gear Noise Mitigation by an upstream installed Fairing

Abstract: The time resolved flow and acoustic fields around a simplified two-wheel nose landing gear configuration featuring brakes, torque link, and a detachable fairing are investigated by numerical and experimental means. The flow field is computed by a lattice Boltzmann method with a collision step based on countable cumulants. Numerical near field flow predictions are validated by experimental results from Delft University of Technology. The comparison shows the quality of the applied computational setup and methodology. The favorable noise mitigation properties of the installed fairing are discussed.

Selection Methodology of Composite Material for Retractable Main Landing Gear Strut of a Lightweight Aircraft

Abstract: The design and development of high-strength and low-weight composite landing gear struts is still a challenge in today’s world. In this study, a selection methodology for fiber-reinforced composite material for retractable main landing gear struts for specified lightweight aircraft up to 1600 kg mass is proposed. Four different fiber-reinforced composite materials, two each from the glass-fiber and carbon-fiber families, including E-glass fiber/epoxy, S-glass fiber/epoxy, T300 carbon fiber/epoxy, and AS carbon fiber/epoxy, were considered for analysis. For the design and analysis of a main landing gear strut, maximum landing loads for one point and two point landing conditions were calculated using FAA FAR 23 airworthiness requirements. Materials were categorized based on their strength-to-weight ratio and the Tsai-Wu failure criterion. Landing gear struts meeting the Tsai-Wu failure criterion, and having a maximum strength-to-weight ratio, were then modeled for performance under a collision detection test. This research concludes that T300 carbon fibre/epoxy is a recommended material for the manufacture of landing gear struts for specified lightweight aircraft.

Preliminary Assessment of an FBG-Based Landing Gear Weight on Wheel System

Abstract: Weight-on-Wheels (WoW) systems are aimed at indicating if the aircraft weight is loading onto the landing gear and its wheels, even partially. These systems are an integral part of the actuation system for safety-critical applications and shall provide reliable information on the actual operational status of the LG. That information reveals if the vehicle is in flight or on the ground. In this way, several kinds of accidents may be prevented, relating for instance, to the incorrect deployment of the landing gear, or even manoeuvres to a certain extent, therefore protecting the aircraft from dangerous damage. There are different architectures that have been proposed in the bibliography, some of them based on strain gauges deployed on the structure, or on proximity sensors installed on the wheels. Being this device and considered critical for safety, it is convenient to couple it with complementary measurements, recorded and processed by different sources. In general, it can be stated that such an intelligent sensor network may be seen as a fundamental support for proper landing gear deployment. The presented paper reports the results of a preliminary investigation performed by the authors to evaluate the possibility of deploying fibre optics on the landing gear structure as part of a WoW system to retrieve the required information. This choice would have a remarkable effect in terms of significant cabling reduction (a single array of sensing elements could be deployed over a single line), and cost abatement from both a manufacturing and operational point of view. There are many other benefits also when referring to an optical instead of a standard electrical sensor system. Due to its small size and ease of integration into different families of materials, it could be considered a system for monitoring the operating status of most actuators on board modern aircraft.

Adaptative Friction Shock Absorbers and Reverse Thrust for Fast Multirotor Landing on Inclined Surfaces

Abstract: Small multirotors are not capable of landing in complex situations, such as on inclined surfaces, in wind gusts or at high impact velocities. This paper explores the use of lightweight friction shock absorbers, combined with rapid thrust reversal, to increase the landing envelope of a quadrotor. The friction shock absorbers serve to dissipate the drone’s kinetic energy and the reverse thrust increases the maximum slope inclination at which it can land. A landing gear prototype was designed and implemented on a DJI F450, and a model was created to generate landing maps to evaluate its benefits. Finally, the technology was tested in real outdoor conditions. The overall system enables drones to safely land on surfaces of up to 60° and at vertical speeds of up to 2.75 m/s, thus increasing the landing envelope by a factor of 8, compared to traditional multirotors.

Propulsion Airframe Aeroacoustics and Aircraft System Noise Flight Test on the Boeing 2020 ecoDemonstrator program

Abstract: A joint Boeing/NASA noise flight test was conducted as part of the 2020 Boeing ecoDemonstrator program on a 787-10 Etihad Airways airplane. The objective was to acquire unique data to advance the understanding and modeling of aircraft system noise sources and engine installation effects or propulsion airframe aeroacoustics. Individual noise sources and their interactions with the airframe, which includes shielding and reflection effects, were measured with several arrays of Kulites on the airplane as well as a large set of acoustic microphones and a phased array on the ground. The airplane was repeatedly flown over the ground instrumentation while power settings and airplane set-up, such as flaps, gear position and speed, were uniquely varied. At the same time, data was collected on board from the Kulite sensors and an engine tachometer signal. High level results showcase the successful execution of the test conditions as well as the full functionality of all data systems demonstrating a very high level of acoustic data quality for robust prediction tool verification and advancement.

Full-Cycle Design and Analysis of the Switchblade Reconfigurable Unmanned Aerial System

Abstract: Previous work has been done on the conceptual design of the 'Switchblade' reconfigurable unmanned aerial vehicle, laying the foundation to the more advanced design and analysis discussed here. In utilizing the ANSYS suite, Refined CFD analysis was performed to obtain better predictions on aerodynamic coefficients of four geometric configurations. The inclusion of winglet and motor nacelle is analyzed, and their effect is more pronounced in the higher aspect ratio wing. CFD results in the form of pressure data are used as inputs to the FEA analysis of the wing, which will be manufactured using a commercial carbon-reinforced nylon. The use of such anisotropic material demands use of more suitable failure criteria in structural analysis, where Von-Mises would not be able to accurately predict failure, therefore Tsai-Wu failure criterion is explored with regard to composite materials that may be examined similarly to anisotropic materials. Wind tunnel experiments are planned and a setup is manufactured and assembled to validate CFD results, and to test trimming and control surface performance of the flying wing design, as well as power consumption in cruise flight conditions.

Stability analysis of Mars soft landing under uncertain landing conditions and two landing strategies

Abstract: Purpose The purpose of this paper is to study the landing performance of the Mars lander considering uncertain landing conditions under two landing modes. Design/methodology/approach A dynamics analysis model for the legged Mars lander is established for landing simulation, where the nonlinear large-deformation flexible buffer rods are equivalently modeled with a rigid-body mechanism with external forces and movement limit. Sensitivities of the landing stability to various landing conditions are analyzed using the Quasi–Monte-Carlo-based Sobol’ method and computer-aided landing simulations. Moreover, based on the results of sensitivity analysis, sensitive parameters are selected for estimating the safe boundaries for stability indices of rotation and clearance. Findings It can be concluded from this study that the lander has excellent ability against overturning. The shutdown-before-touchdown strategy helps to maintain than landing pose, and the shutdown-at-touchdown strategy helps to prevent the nozzle from colliding with the surface of Mars. Practical implications This study provides a theoretical reference to choose the better landing strategies for Mars landers considering uncertain landing conditions. Originality/value A parameterized dynamics Mars lander model and a simplification method are proposed to simulate the landing on Mars. Uncertain landing conditions are parameterized and considered in the dynamics model. Sensitivity analysis and safe boundary methods are used to compare the landing performances with two landing strategies.