Landing Gear Wheel Research Articles

Simulation of the landing situation of an aircraft and the problems of diagnosing anti-skid devices

Safety is ensured, including the safe landing of the aircraft. A short landing run without a skid is achieved by the necessary preparation of the runway, a serviceable braking system, anti-skid automation and take-off and landing devices of the aircraft. Standard operation of anti-skid automatics should be able to cope with constant non-linearity of movement and atmospheric interference on the surface of the runway, as well as adjust the wheel slip coefficient to ensure reliable operation of the braking system. The need to develop technical solutions in the field of expanding the operational capabilities of diagnostic tools for anti-youth automation of the aircraft braking system is determined by regular aviation incidents, related to failures of anti-skid devices, including their incorrect setting before installation on the aircraft landing gear wheel, which leads to serious consequences – increased wear of the wheel tire surface and its possible destruction, including an emergency landing due to loss of control over the aircraft. The purpose of the work is to simulate the youth situation of the aircraft during landing, to study the problem, to increase the efficiency, reliability of the results of diagnosing devices and automata of the aircraft braking system. This article discusses the main external and operational factors affecting the dynamics and nature of the aircraft's run along the runway, the model of aircraft movement with the influence of aerodynamic forces on it, the model of tire friction on the ground, and also proposes a method for diagnosing anti-youth automation of the aircraft braking system.

Dynamic analysis of aircraft towing slip-out system considering vertical wheel constraints

Abstract To analyze the vertical dynamic characteristics of the aircraft towing system under different constraints on the nose landing gear wheels of the aircraft during the towing slip-out mode, a dynamic model of the towing system considering the constraints between the clamping mechanism and the aircraft nose landing gear wheels was established based on the general towing system dynamic model. On this basis, an analysis was conducted to determine whether considering the aircraft wheel constraints affects the vertical vibration acceleration of the towing vehicle and the nose landing gear in low-speed (10 km/h) and high-speed (40 km/h) operating conditions. With the consideration of constraints at both ends of the aircraft wheels, the vertical acceleration of the towing vehicle's center of mass increased by 153% and 172% at low speed and high speed, respectively, compared to not considering the aircraft wheel constraints. Additionally, with the consideration of constraints at both ends of the aircraft wheels, the vertical acceleration of the nose landing gear's center of mass decreased to 20% and 57% at low speed and high speed, respectively, compared to not considering the aircraft wheel constraints. An analysis of the vertical vibration acceleration of the towing vehicle under different wheel constraint conditions found that the RMS value of the vertical vibration acceleration of the towing vehicle's center of mass was minimized when the clamping angles of the clamping mechanism to the nose landing gear wheels were 63° and 64°, respectively. Under this clamping angle, the influence of the clamping forces at both ends of the clamping mechanism on the vertical vibration acceleration of the towing vehicle was minimal. The research results provide valuable reference for the direct constraints between the clamping mechanism and the nose landing gear wheels in the aircraft towing slip-out system.

Experimental research of hydraulic cylinder with the built-in throttle for steering the front landing gear wheel

This paper presents the experimental research method of a hydraulic cylinder used for steering the front landing gear wheel. A mechanical-hydraulic steering system is operated by two interchangeable hydraulic cylinders acting in tandem to rotate the movable sub-assembly that contains the front landing gear wheel. Each hydraulic cylinder is designed with a built-in throttle to equalize the speed of the hydraulic cylinder rod traveling in both directions of movement (extension and retraction). During the experiments, three constructive variants of the built-in throttle will be used to obtain the optimal variant.

Calculation of steering system parameters of a military training aircraft

The mechanical-hydraulic steering system of a military training aircraft is a technical problem for specialized engineers and it must be investigated and solved in a scientific manner using theoretical knowledge, calculus programs such as Mathcad, and CAD applications for design such as CATIA V5 which allows the preservation of practical experience and favors its dissemination for future similar calculation. The scope of this calculus is to demonstrate that the active moment developed by the two hydraulic cylinders is always bigger than the resisting moment opposing the steering action of the nose landing gear wheel generated by the frictional forces between the wheel and the running way.

Simulation of the hydraulic steering device, for a nose landing gear

The hydraulic steering simulation is done with SIMULINK, part of the MathWorks MATLAB® application. All parts, subassemblies, and assemblies that define the nose landing gear (NLG) and nose wheel steering are fully defined in 3D, with CATIA V5 - a computer-aided design software used for modeling, it is possible to carry out simulations that allow preliminary evaluation, theoretically and experimentally. The purpose of this simulation is to confirm the correctness of the steering gear kinematics, that the two hydraulic cylinders have been sized correctly and can overcome the resistive steering moment, and that the steering time complies with design specifications for the nose landing gear of a military training aircraft.

Numerical Study of Influencing Factors of Safety and Stability of Tunnel Structure under Airport Runway

A six-degree-of-freedom mathematical model and mechanical balance equation of a “five-point-contact” aircraft are established in this study. The model and equation are used to investigate the safety and stability of a tunnel structure under the runway of an airport, particularly when aircraft taxi or move on the runway. ABAQUS is used to construct a three-dimensional finite element model of the cooperative deformation of the airport runway–soil–tunnel structure. The analysis focuses on the response and evolution of structural safety mechanical indices from the perspective of three influencing factors: type of aircraft, road surface, and burial depth. The results show that the distribution position of the main landing gear wheel is more concentrated using the dynamic load equation of different aircraft. A rigid pavement is not easily deformed when subjected to aircraft loads, whereas a flexible pavement has an excellent attenuation effect on diffusing forces. The shear stresses on the upper and lower arches of the tunnel structure differ depending on the pavement material. The deformation of the arches under shear stress is more intense than that of other parts. With an increase in burial depth, the tunnel structure withstanding the aircraft load disturbance exhibits an attenuation trend. The disturbance caused by soil stress to the tunnel structure must not be ignored. When the burial depth of the tunnel exceeds 64 m, the tunnel structure ceases to be disturbed by aircraft loads. The research results can significantly guide airport construction and be used as a reference for investigating the safety and stability of substructures under airport runways.

Advanced landing gear fibre Bragg grating sensing and monitoring system

In this paper an advanced optical-based landing gear load sensing and monitoring system is presented. The system measures strains using fibre Bragg grating sensor that are converted into loads and torque at the landing gear wheels and provides this data for use by the aircraft systems for integration with aircraft health monitoring, hard landing detection, flight management, flight controls and ground controls. A complete sensing system was developed in the European Union Clean Sky 2 Joint Technology Initiative Advanced Landing Gear Sensing and Monitoring (ALGeSMo), described herein. This involved: the integration of optical fibres into a composite structure, the development of an optical harness (cabling and connectors) meeting aircraft installation requirements, the readout of the optical fibre sensors with state-of-the-art miniature optoelectronics and the processing and communication of the data. Apart from specific tests on the various components, a bespoke test rig was developed to rigorously test the whole sensing and monitoring system on an A320 main landing gear slider tube to validate the performance of the system. The system-level tests performed on the test rig showed a very good correlation with applied actuator loads and additional conventional strain and temperature sensors. It demonstrates that loads along all three axis of the landing gear and the torque about the wheel axle can be accurately measured. Tests performed at cold and elevated temperatures, however, revealed that the generally applied one-dimensional temperature compensation equation is not accurate enough for this application, due to the non-uniform non-stationary temperature field. The ALGeSMo research activities have advanced the state of the art in several key areas for the deployment of optical sensing systems for safety-critical applications, such as integration of optical fibres into composite material, robust optical connections, avionic-compliant optical interrogator and landing gear load measurement up to technology readiness level technology readiness level 5.

A comparison between off and on-body control surfaces for the FW-H equation: Application to a non-compact landing gear wheel

This work is a contribution to the ongoing debate about the role of quadrupoles in low Mach number flows, studied through the use of solid and permeable surface Ffowcs-Williams & Hawkings (FW-H) integrals for landing gear numerical noise predictions. It rests upon the key idea that the dominance of surface sources over volume sources can only be guaranteed when the compact-source condition is met. We propose here to express this property as a condition on the smallness of the product between the Mach and Strouhal numbers, or formally as MSt < 1. We consider a canonical isolated wheel, that basically consists in a shallow circular cavity inscribed in a coin-like cylinder, thus presenting few different length scales, as compared to a full landing gear assembly. Zonal Detached Eddy Simulations are performed on several gradually refined grids to assess the grid convergence of the numerical result. In particular, important computational effort is put into the accurate resolution of acoustic waves up to Strouhal numbers such that MSt > 1. Overall, determining the real significance of quadrupoles was challenging as numerical errors or misleading effects such as near-field terms, surface discretization, or source domain truncation biased the initial permeable surface results. Even when these sources of bias are removed, non-negligible differences are found between the solid and permeable noise spectra at non-compact St values, while both formulations are equivalent at lower Strouhal numbers. The analysis of these differences is extended to the determination of their impact on frequency-domain noise maps obtained with the DAMAS algorithm fed with far-field signals computed with both FW-H approaches. A tentative interpretation of the wheel noise sources is finally proposed, highlighting the dominant role of the scattering of aerodynamic sources by the cavity downstream edge at low Strouhal numbers, while wake sources dominate at higher Strouhal numbers.

Development of hydraulic transmission for implementing an active drive of the landing gear wheels of modern transport aircraft

AnnotationAn active drive of the wheels of the chassis is necessary on the take-off and run with reduced coupling characteristics of the airplane on an unpaved or icy runway in crosswind conditions to reduce lateral drift from the axis of the strip. The hydraulic transmission has been developed for the active drive of the wheels by aircraft chassis. At using a control system, that regulates the moment wheels characteristics and includes an adaptive circuit with neural network, it is possible to reduce the lateral drift of the aircraft about 30–40 %. The output parameters of the hydraulic motors intended for the landing gear wheels of aircraft weighting 21 tons are determined.

Determining Wheel Forces and Moments on Aircraft Landing Gear with a Dynamometer Sensor.

This paper describes airfield measurement of forces and moments that act on a landing gear wheel. For the measurement, a wheel force sensor was used. The sensor was designed and built based on strain gage technology and was embedded in the left landing gear wheel of a test aircraft. The sensor is capable of measuring simultaneously three perpendicular forces and three moments and sends data to a handheld device wirelessly. For the airfield tests, the sensor was installed on a PZL 104 Wilga 35A multipurpose aircraft. The aircraft was towed at a “marching man” speed and the measurements were performed at three driving modes: Free rolling, braking, and turning. The paper contains results obtained in the field measurements performed on a grassy runway of the Rzeszów Jasionka Aerodrome, Poland. Rolling resistance of aircraft tire, braking friction, as well as aligning moment were analyzed and discussed with respect to surface conditions.

Cavity Resonance Suppression Using Fluidic Spoilers

This paper examines experimentally the use of a fluidic spoiler to suppress the resonance within a partially closed cylindrical cavity subject to a grazing flow. The relative movement of aircraft and high-speed land-based vehicles through air often results in structural cavities in these vehicles being subject to shear-layer-driven resonance. This can lead to high-amplitude pressure fluctuations within the cavity volume, causing damage to stores or equipment found within landing-gear wheel or weapon bays, for example, or else significant discomfort to the passengers of cars or trains. This large-scale buffeting can also cause vehicle stability problems and can increase drag. This work presents a novel method, in which passive flow control consisting of an upstream fluidic spoiler is used to redirect the upstream flow so that the cavity orifice is shielded. As a result, the grazing flow can no longer detach from the upstream leading edge of the cavity, and thus, vortex shedding is suppressed. The scope of the study includes an examination of higher-order azimuthal acoustic modes excited in the cylindrical cavity: modes which have received little attention in the literature, but which can be readily excited for many flow configurations for partially covered cavities.

A method for determining the horizontal impact load based on the rotational speed of the aircraft's wheel in a landing gear drop test

ABSTRACTThe 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.

The noise generated by a landing gear wheel with hub and rim cavities

Wheels are one of the major noise sources of landing gears. Accurate numerical predictions of wheel noise can provide an insight into the physical mechanism of landing gear noise generation and can aid in the design of noise control devices. The major noise sources of a 33% scaled isolated landing gear wheel are investigated by simulating three different wheel configurations using high-order numerical simulations to compute the flow field and the FW-H equation to obtain the far-field acoustic pressures. The baseline configuration is a wheel with a hub cavity and two rim cavities. Two additional simulations are performed; one with the hub cavity covered (NHC) and the other with both the hub cavity and rim cavities covered (NHCRC). These simulations isolate the effects of the hub cavity and rim cavities on the overall wheel noise. The surface flow patterns are visualised by shear stress lines and show that the flow separations and attachments on the side of the wheel, in both the baseline and the configuration with only the hub cavity covered, are significantly reduced by covering both the hub and rim cavities. A frequency-domain FW-H equation is used to identify the noise source regions on the surface of the wheel. The tyre is the main low frequency noise source and shows a lift dipole and side force dipole pattern depending on the frequency. The hub cavity is identified as the dominant middle frequency noise source and radiates in a frequency range centered around the first and second depth modes of the cylindrical hub cavity. The rim cavities are the main high-frequency noise sources. With the hub cavity and rim cavities covered, the largest reduction in Overall Sound Pressure Level (OASPL) is achieved in the hub side direction. In the other directivities, there is also a reduction in the radiated sound.

SHIMMY ANALYSIS OF LIGHT AIRPLANE MAIN LANDING GEAR

A method of shimmy analysis of the main landing gear non-swiveling wheel without a shimmy damper based on the use of free vibration frequencies and modes of a gear leg at the wheel axis is proposed. The finite-element method is suggested to find the free vibration modes of the gear leg. The proposed method allows more precise modeling of the wheel/airplane elastic link to be used. The application of the method is illustrated by light-airplane main landing gear shimmy analysis.

A New Method for Determining Horizontal Impact Load Based on Rotational Speed of Aircraft Wheel in Landing Gear Drop Test

The maximum horizontal impact load experienced by the aircraft landing gear wheel during landing is an important parameter in landing gear safety design and performance analysis. Using a non-contact photoelectric testing method, this paper experimentally obtained the dynamic data of the instantaneous rotational speed for an aircraft wheel when it contacts the platform. Moreover, the kinetic relationship between the transient rotational speed of the aircraft wheel and the force of horizontal impact was established. According to the change data measured from the transient rotational speed of the aircraft wheel, the maximum horizontal impact load at the instant of aircraft contact with the platform was calculated. To verify the accuracy of this method, in which changes in rotational speed determine the horizontal impact load, verification equipment without lateral constrains was established to test the horizontal impact load of the aircraft wheel. The experimental results showed that the horizontal impact load determined by the transient rotational speed of aircraft wheel is consistent with the results obtained by self-built measurement equipment without lateral constrains.

Vorticity amplification near the stagnation point of landing gear wheels

The vicinity near the forward stagnation point of landing-gear wheels has been found to support a mechanism for oncoming streams of weak vorticity to collect, grow, and amplify into discrete large-scale vortical structures that then shed with a distinct periodicity. To the authors’ knowledge, such a flow phenomenon has never been reported before for landing gear wheels, which are in essence finite (three-dimensional) cylinders. To gain further insight into this phenomenon, a detailed experimental study has been undertaken employing the hydrogen bubble visualization and Particle Image Velocimetry techniques. A very thin platinum wire, similar to those used in hydrogen bubble visualization applications, was placed upstream of the wheel model to produce two streams of weak vorticity (with opposite sign) that convected toward the model. As the vorticity streams enter the stagnation region of the wheels, significant flow deceleration and vorticity stretching act to collect, grow, and amplify the incoming vorticity streams into large-scale vortical structures. Experiments were performed at a fixed Reynolds number, with a value of 32 500 when defined based on the diameter of the wheel and a value of 21 based on the diameter of the vorticity-generating upstream wire. First, to establish a baseline, the natural flow field (without the presence of an upstream wire) was characterized, where experimentally determined values for the stagnation boundary-layer thickness and the velocity profile along the stagnation streamline were both found to agree with the values provided in the literature for two-dimensional cylinders. Subsequently, the dynamics of vorticity collection, growth, amplification, and shedding were studied. The size, stand-off distance and the shedding frequency of the vortical structures forming near the stagnation region were all found to strongly depend on the impingement location of the inbound vorticity on the wheel. A simple relationship between the non-dimensional characteristic size and the non-dimensional shedding frequency was found to hold over the entire range of locations where vorticity amplification and shedding were observed. Penetration of the vortical structures into the stagnation boundary layer was observed for specific locations of inbound vorticity impingement.

Canonical description of the control system in the shimmy problem for the landing gear wheels of an aircraft

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

Investigation of landing gear wheel shimmy taking into account damper frequency characteristics

A mathematical model and a technique for calculating the rolling motion stability of the damper-equipped landing gear wheel are presented; the dependence of dynamic damper rigidity on frequency found experimentally is used in the investigation. The results of calculating the shimmy boundaries with and without regard for the dependence indicated are given.

Fatigue analysis of a P180 aircraft main landing gear wheel flange

A piece of inner wheel flange separated from the main landing gear (MLG) right wheel of a Piaggio Avant P180 aircraft during taxing on the runway. The wheel was a 2014-T6 aluminium alloy and had been in service 22 years. Morphological observation of the fractured surfaces indicated fatigue was the cause of failure. The crack grew to approximately 8 cm in length and 5 cm in deep before the final catastrophic failure and was due to a corrosion pitting promoted by fretting from the tyre bead and the tube well, thus causing the removal of the protective coating. The fatigue life assessment also provided an estimation of the number of flight cycles to failure supported by the wheel during the crack propagation confirming those accumulated since its last inspection. It was recommended the inspection interval be reduced one-third of its original one as well as a proper maintenance procedure to be introduced in order to verify the integrity of the coating, to remove eventually corrosion and re-protect the component.

Investigation into cadmium embrittlement of landing gear wheel axles

There are two landing gear wheel axles, called, respectively, 1# and 2#. Axle 1# was not carried through cadmium stripping prior to stress annealing, and the repair process of axle 2# had cadmium stripping before stress relieving. In order to confirm if there is cadmium embrittlement in the landing gear wheel axles, a series of experimental analyses were carried through and some conclusions were obtained. There is no cadmium diffusion in 1# and 2# axles and risk of cadmium embrittlement can be excluded. High compressive stress exists on surface of 1# and 2# axles and shot peening is effective. Cadmium layer was oxidized approximately 0.35 μm from outer surface, but the oxidized layer has not attacked the base material. The prerequisites of cadmium embrittlement were studied. The three prerequisites of cadmium embrittlement are cadmium, a certain tensile stress and a certain temperature. Disappearance of any one of the prerequisites can avoid cadmium embrittlement as verified by our experiments.