Showing papers on "Landing gear published in 2009"

LAGOON: further analysis of aerodynamic experiments and early aeroacoustics results

Abstract: This paper presents early results of an experimental aeroacoustic program recently performed in ONERA’s open-jet anechoic windtunnel CEPRA19 with a generic landing gear configuration. This program is the continuation of steady/unsteady flow measurements achieved in 2007 in ONERA’s F2 aerodynamic windtunnel (closed test section). Both experiments constitute the experimental phase of the LAGOON program (LA nding Gear NOise database for CAA validatiON ), currently supported by Airbus and involving ONERA and DLR (the French and German national aerospace research centres) and Southampton University, with the general purpose of evaluate up-to-date CFD/CAA techniques for airframe noise simulation, validated against an extensive experimental aerodynamic/acoustic database. The first point addressed in the present paper is the flow identification between both facilities, relying on limited aerodynamic measurements performed with a 5-hole probe and with onboard static pressure taps and unsteady pressure transducers. This flow identification was supported by a CFD study of the 3D flows in both windtunnels, performed by DLR. It is shown that there exist tiny differences between both flows. The second addressed point is the “signal-to-noise” ratio, or the ratio of the aerodynamic noise radiated by the model, to the background noise measured in the windtunnel without the model. It is shown that this ratio is globally satisfying, especially since this landing gear model with smooth shape is expected to be more silent than an actual landing gear with the same scale.

A Comparative Study of a 1/4-Scale Gulfstream G550 Aircraft Nose Gear Model

Abstract: A series of fluid dynamic and aeroacoustic wind tunnel experiments are performed at the University of Florida Aeroacoustic Flow Facility and the NASA-Langley Basic Aerodynamic Research Tunnel Facility on a high-fidelity -scale model of Gulfstream G550 aircraft nose gear. The primary objectives of this study are to obtain a comprehensive aeroacoustic dataset for a nose landing gear and to provide a clearer understanding of landing gear contributions to overall airframe noise of commercial aircraft during landing configurations. Data measurement and analysis consist of mean and fluctuating model surface pressure, noise source localization maps using a large-aperture microphone directional array, and the determination of far field noise level spectra using a linear array of free field microphones. A total of 24 test runs are performed, consisting of four model assembly configurations, each of which is subjected to three test section speeds, in two different test section orientations. The different model assembly configurations vary in complexity from a fully-dressed to a partially-dressed geometry. The two model orientations provide flyover and sideline views from the perspective of a phased acoustic array for noise source localization via beamforming. Results show that the torque arm section of the model exhibits the highest rms pressures for all model configurations, which is also evidenced in the sideline view noise source maps for the partially-dressed model geometries. Analysis of acoustic spectra data from the linear array microphones shows a slight decrease in sound pressure levels at mid to high frequencies for the partially-dressed cavity open model configuration. In addition, far field sound pressure level spectra scale approximately with the 6th power of velocity and do not exhibit traditional Strouhal number scaling behavior.

Adaptive landing gear: Optimum control strategy and potential for improvement

Abstract: An adaptive landing gear is a landing gear (LG) capable of active adaptation to particular landing conditions by means of controlled hydraulic force. The objective of the adaptive control is to mitigate the peak force transferred to the aircraft structure during touch-down, and thus to limit the structural fatigue factor. This paper investigates the ultimate limits for improvement due to various strategies of active control. Five strategies are proposed and investigated numerically using a validated model of a real, passive landing gear as a reference. Potential for improvement is estimated statistically in terms of the mean and median (significant) peak strut forces as well as in terms of the extended safe sinking velocity range. Three control strategies are verified experimentally using a laboratory test stand.

Bifurcation and Stability Analysis of Aircraft Turning on the Ground

Abstract: During ground maneuvers a loss of lateral stability due to the saturation of the main landing gear tires can cause the aircraft to enter a skid or a spin. The lateral stability is governed not only by aspects of the gear design, such as its geometry and tire characteristics, but also by operational parameters: for example, the weather and taxiway condition. In this paper, we develop an improved understanding and new presentation of the dynamics of an aircraft maneuvering on the ground, ultimately aimed at optimization and automation of ground operations. To investigate turning maneuvers, we apply techniques from dynamic systems theory to a modified version of a nonlinear computer model of an A320 passenger aircraft developed by the Landing Gear Group at Airbus in the United Kingdom. Specifically, we present a bifurcation analysis of the underlying solution structure that governs the dynamics of turning maneuvers with dependence on the steering angle and thrust level. Furthermore, a detailed study of the behavior when lateral stability is lost focuses on how the tire saturation at different wheel sets leads to qualitatively different types of overall behavior. The presented bifurcation diagrams identify parameter regions for which undesirable behavior is avoidable, and thus they form a foundation for defining the safe operating limits during turning maneuvers.

Aircraft landing gear arrangement and a nose landing gear assembly

Abstract: An aircraft landing gear arrangement comprises a nose landing gear assembly and at least one main landing gear assembly. The nose landing gear assembly has a nose landing gear wheel with a high energy brake apparatus therein. The main landing gear assembly has a main landing gear wheel with a high energy brake apparatus therein and a main landing gear wheel with a motor therein. The motor is used for driving the main landing wheel during taxiing of the aircraft.

Performance evaluation on vibration control of MR landing gear

Abstract: This paper is concerned with the applicability of the developed MR damper to the landing gear system for the attenuating undesired shock and vibration in the landing and taxing phases. First of all, the experimental model of the MR damper is derived based on the results of performance evaluations. Next, a simplified skyhook controller, which is one of the most straightforward, but effective approaches for improving ride comport in vehicles with active suspensions, is formulated. Then, the vibration control performances of the landing gear system using the MR damper are theoretically evaluated in the landing phase of the aircraft. A series of simulation analyses show that the proposed MR damper with the skyhook controller is effective for suppressing undesired vibration of the aircraft body. Finally, the effectiveness of the simulation results are additionally verified via HILS (Hardware-in-the-loop-simulation) method.

Aircraft Electrical Landing Gear Actuation Using Dual-output Power Converter with Mutual Power Circuit Components

Abstract: This paper describes the design, construction and testing of a dual-output power converter concept where only the large components, such as the DC link capacitor and heat-sink, are shared between two actuators which are used sequentially in the deployment of aircraft landing gear This mutual component approach combines the advantages of dual-use power converters with the flexibility of one power converter per application Practical results of the converter operating are presented for a range of test conditions in order to validate the simulation study

Multifunctional electromechanical device for landing gear

Abstract: The invention relates to a multifunctional electromechanical device for aircraft landing gear, comprising at least: a first shaft (10) rotatably mounted onto the aircraft around a rotational axis (R) substantially parallel to a hinge axis (X) of the landing gear on the aircraft; a second telescopic shaft (20) rotatably mounted onto the landing gear while descending along the latter until in proximity with the wheels present on the latter; a transmitting means (19) for transmitting a rotational movement of the first shaft to the second shaft; a transmitting means (21) for transmitting a rotational movement of the second shaft to at least one wheel present on the landing gear; a braking means (30) being specific to one of the shafts in relation to the landing gear if the wheel is not provided with a brake; and a motor means (11, 15) for turning the first shaft.

Tire pressure augmented aircraft weight and balance system and method

Abstract: A weight and balance system for accurately determining gross weight of an aircraft. The present invention integrates tire pressure measurements with strut pressure measurements to overcome the problem associated with the friction in the strut seals, and simultaneously overcome the problem with the large number of variables associated with using tire pressure measurement to determine load (weight on wheels). An example system includes a plurality of strut pressure sensors that generate strut pressure data for landing gear struts of the aircraft and a plurality of tire pressure sensors that generate tire pressure data for tires of the aircraft. A processing device that is in data communication with the strut and tire pressure sensors determines gross weight and center of gravity of the aircraft based on the received strut and tire pressure data.

Aircraft landing gear compression rate monitor and method to increase aircraft landing weight limitation

Abstract: A system for use in monitoring, measuring, computing and displaying the rate of compression of aircraft landing gear struts, experienced while aircraft are executing either normal or hard landing events. Further by measuring the vertical compression rate of the landing gear strut, thus with aircraft hull angle correction to horizontal, determining the vertical sink-rate of the aircraft, as it comes into initial contact with the ground. Accelerometers are attached to opposing sides of a compressible landing gear strut, monitoring and measuring parallel data streams; then identifying differential acceleration data streams, which computed through mathematical algorithms measure the collapse rate of the landing gear strut. Pressure sensors are attached to the working pressure within the landing gear strut, so to monitor in-flight landing gear strut pre-charge pressure, until such time as the pre-charge pressure suddenly increases, to detect the aircraft has come into initial contact with the ground. A method of operating an aircraft at an increased maximum landing weight limitation.

Landing gear with noise reduction fairing

Abstract: An aircraft noise reduction apparatus is provided which includes an aircraft landing gear assembly and a noise reduction fairing 12 . The landing gear assembly comprises a landing gear 10 arranged to be moveable between a stowed position and a fully deployed position. The noise reduction fairing 12 may comprise a wrap-around fairing which, when the landing gear 10 is in its fully deployed position, wraps around the landing gear 10 and extends along the majority of the length of a landing gear leg 11 . A landing gear bay door assembly 16, 17 comprising at least one door may also be provided. The fairing 12 may have a recess 24 for accommodating one of landing gear bay doors when the door 16 is in its fully open position.

Computational aeroacoustic analysis of a ¼ scale g550 nose landing gear and comparison to nasa & ufl wind tunnel data

Abstract: In conjunction with the NASA-Gulfstream and Gulfstream-University of Florida wind tunnel testing of a generic nose landing gear model, Computational Aero-Acoustics research was conducted at Gulfstream using the commercial Navier-Stokes Finite Volume CFD solver STAR-CCM+. The simulation modeled the ¼ scale G550 nose landing gear mounted in the NASA Basic Aerodynamics Research Tunnel (BART) wind tunnel test section. The model was run at the 0.166 Mach Number condition on the simplified nose landing gear with the gear cavity closed. Prior to simulation execution, dynamic pressure probes were inserted onto the surface of the model at the exact locations of the dynamic pressure transducers on the nose landing gear wind tunnel model. Delayed Detached Eddy Simulation (DDES) (1) was run with a 58 million cell unstructured grid on 47 3.0 GHz quad-core processors for approximately two weeks to obtain a total of 0.05 seconds of statistically limit-cycled pressure data was processed. Results of the simulation were compared to data from the NASA BART and University of Florida anechoic wind tunnel results at both surface mounted steady and unsteady pressure transducers. The simulation showed good agreement in comparisons of power spectral density up to 5 kHz at mesh/time step dependent frequencies at all locations captured. In addition, the simulation was in somewhat good agreement with the measured mean turbulence levels at the wheel hub height and good agreement at static pressure taps located on the starboard wheel.

Lateral Stability of Aircraft Nose-Wheel Landing Gear with Closed-Loop Shimmy Damper

Abstract: Shimmy of aircraft nose-wheel landing gear is a coupled lateral and torsional dynamic instability that may occur during take off, taxi, and landing. The potential for shimmy is often discovered when the aircraft undergoes taxi (runway) tests. At this stage the options available to the designer are limited, often to introducing a damper in the steering degree of freedom. This paper presents modeling and analysis of shimmy of a 3 degrees-of-freedom linear nose-wheel landing gear model with a closed-loop shimmy damper mechanism attached to its hydraulic steering. A typical control law is considered for representing the closed-loop hydraulic control in the steering rack and pinion system. The stability of the system is studied using root locus plots. The results for critical velocity obtained for different values of gain in the closed-loop shimmy damper show that it can be simulated by an equivalent open-loop shimmy damper with appropriate value of damping. This suggests that an equivalent open-loop shimmy damper model can be used in place of the closed-loop shimmy damper to simplify the modeling of integrated airframe— landing gear dynamics.

Electrically activated aircraft landing gear control system and method

Abstract: An electrically activated landing gear control system is provided. A processing module of landing gear control system is provided with landing gear control system software that receives data relating to the position of a landing gear lever. Proximity sensors positioned at landing gear and wheel well areas of the aircraft are coupled for communication with the processing module. The proximity sensors provide the landing gear control system software with position data relating to the landing gear. The landing gear control software converts the data received from the landing gear lever and the data received from the proximity sensors to command signals to control electrically activated valves associated with landing gear components. The command signals may be sent simultaneously to remote power distribution units and remote data concentrator units to energize or de-energize solenoid coils of the electrically activated valves.

Fuzzy PID control for landing gear based on magneto-rheological (MR) damper

Abstract: Landing gear of aircraft is the key component. The magneto-rheological (MR) damper applied to landing gear can ensure stability and safety during the process of takeoff, landing and rollout. Because of landing gear is a nonlinear, multivariate and multi-degree of freedom system. The traditional PID control can't obtain ideal control effects. Based on the advantages of fuzzy control theory do not need a precise mathematical model, fuzzy PID control is proposed in this paper by combining PID control and fuzzy control. The models of landing gear are simulated and analyzed under passive control, PID control and fuzzy PID control. The simulation results indicate that fuzzy PID control can effectively lower the amplitude of fuselage vibration acceleration and improve the ride quality and safety of aircraft. It has an important influence in the optimal control of the landing gear system.

Top-Down Cracking Predictions for Airfield Rigid Pavements:

Abstract: Recent full-scale testing of airfield rigid pavements has demonstrated the possibility of top-down cracking in concrete slabs. The objective of this study was to identify critical gear positions that produced the maximum tensile stress on the top of airfield rigid pavements, given no initial curling. Three individual aircraft gear geometries (dual, dual tandem, and triple dual tandem) and four aircraft types—considering all their main landing gears (B-777, A-380, MD-11, and B-747)—were analyzed for several slab configuration, pavement geometry, and material assumptions. The two-dimensional finite element analysis results showed that consideration of the entire main landing gear of the aircraft was necessary if the top tensile stresses were to be predicted accurately, except for the B-777. The A-380 and MD-11 had the greatest top-to-bottom tensile stress ratios for the full-gear analysis (critical tensile stress at the transverse joint) when the body gears were placed on the same slab for the no-load trans...

Ancillary device with an air turbine for taxiing an aircraft on the ground

Abstract: Device for driving at least one wheel of an aircraft landing gear, which includes at least one turbine machine incorporated into the landing gear of the aircraft. Advantageously, the turbine machine is a pneumatic turbine.

Aircraft landing gear steering system

Abstract: An aircraft landing gear steering system comprising a turning member that is operably coupled to a landing gear leg through a harmonic drive mechanism. The landing gear steering system may be electrically driven. Additionally, the landing gear system has various advantages, including the provision of a safe failure mode should the harmonic drive mechanism fail.

Over-speed, rough loads and hard landing detection system

Abstract: A system, apparatus and method provide a means for indicating an overload condition has occurred during aircraft operation. The occurrence of an overload condition is automatically determined and an indication output thereof. Based on the indication received by the cockpit, avionics, maintenance, etc., further action may be taken to correct the effects of the overload condition on the tires and/or landing gear.

Non-linear analysis of a typical nose landing gear model with torsional free play:

Abstract: One of the problems faced by the aircraft community is the landing gear dynamics, especially the shimmy. Non-linear behaviour of landing gear makes the evaluation of the shimmy phenomenon more complex and its prediction more difficult. Notably the non-linearities in landing gear torsional free play tend to destabilize the landing gear, whereas the frictional non-linearity dissipates energy and thus increases the landing gear stability. This article presents the study of the shimmy instability of a typical nose landing gear model developed based on the Li formulations with torsional free play. Finally, the study has been performed to postpone the dynamic instability by introducing magneto rheological fluid-based damper.

Landing gear noise reduction assembly

Abstract: An aircraft noise reduction apparatus including an aircraft landing gear assembly ( 10 ) and a noise reduction fairing ( 12 ) is described. The landing gear assembly comprises ( 10 ) a landing gear bay having an aperture ( 14 ), a landing gear moveable between a stowed position and a fully deployed position, and at least one landing gear bay door ( 16 ) moveable to close and open the aperture. The noise reduction fairing ( 12 ) is positioned fore of the landing gear bay door assembly. The noise reduction fairing ( 12 ) is moveable between a stowed position and a fully deployed position such that in the fully deployed position, the noise reduction fairing ( 12 ) acts to reduce noise that would otherwise be generated by the interaction of the landing gear assembly when deployed and the air flowing past it.

The analysis of shimmy instability of a typical nose landing gear using active torsional magneto-rheological damper:

Abstract: Shimmy is an oscillation in the nose landing gear (NLG) of an aircraft that may occur during taxiing, take-off or landing. Increasing emphasis on reducing the weight of landing gear systems in modern aircraft has, in many cases, induced shimmy problems and active vibration control has gradually been used to suppress vibration. The objective of the current investigation is to introduce an active torsional magneto-rheological (MR) fluid-based damper for shimmy vibration control of a typical NLG. In the present study, the shimmy model is developed based on the formulation of G. X. Li, to study the self-induced dynamic instability at the critical forward taxi velocity. The effect of various parameters on the shimmy behaviour is also studied. The study has been performed to postpone the dynamic instability by introducing MR fluid-based damper as a semi-active device and also a closed-loop feedback control scheme is employed to control the landing gear instability of an aircraft.

Numerical Analysis of Steady Flow around a Landing Gear Noise Measurement Model

Abstract: It is well known that landing-gear noise is one of the dominant noise sources during the approach phase of a civil airplane. Therefore, it is important to understand the noise generation mechanism and reduce the noise from a landing gear. In this study, steady-state flow analysis around a landing gear model is reported using unstructured-mesh method. To predict the landing gear noise directly, unsteady flow analysis is necessary. However, even from the steady-state analysis, information related with the noise generation could be gained by focusing on the accelerated region or wake interference. From these preliminary results, basic flow field information is obtained to understand the flow physics around the complicated landing gear geometry.

Fatigue Life Estimation of Helicopter Landing Probe Based on Dynamic Simulation

Abstract: This paper develops a framework of dynamic simulation driven fatigue life analysis of a landing probe system for a typical 12-ton tricycle landing gear helicopter for embarked operations on the typical frigate. By integrating a novel dynamic helicopter/ship interface simulation with the rainflow cycle counting method, fatigue spectra, including all possible probe load cases under the wide range of operating and environmental conditions, have been developed with a confidence level of greater than 99.9%: otherwise, they would be practically unobtainable, even by limited sea trial testing. Furthermore, the fatigue stresses of the probe assembly were obtained by the finite element method, and the cumulative fatigue damage analyses were conducted by monitoring the fatigue life of the critical locations on each component of the probe assembly using the Palmgren-Miner rule against the design life requirement. This new approach provides an innovative and efficient design tool, through virtual prototyping, that can speed up the design process and reduce cost.

Magneto-Rheological (MR) Damper for Landing Gear System

Abstract: Depending on the different sink speeds, angles of attack and masses; aircraft landing gears could face a wide range of impact conditions which may possibly cause structural damage or failure. Thus, in hard landing scenarios, the landing gear must absorb sufficient energy in order to minimize dynamic stress on the aircraft airframe. Semi-active control systems are the recent potential solutions to overcome these limitations. Among semi-active control strategies, those based on smart fluids such as magneto-rheological (MR) fluids have received recent attraction as their rheological properties can be continuously controlled using magnetic or electric field and they are not sensitive to the contaminants and the temperature variation and also require lower powers. This thesis focuses on modeling of a MR damper for landing gear system and analysis of semi-active controller to attenuate dynamic load and landing impact. First, passive landing gear of a Navy aircraft is modeled and the forces associated with the shock strut are formulated. The passive shock strut is then integrated with a MR valve to design MR shock strut. Here, MR shock strut is integrated with the landing gear system modeled as the 2DOF system and governing equations of motion are derived in order to simulate the dynamics of the system under different impact conditions. Subsequently the inverse model of the MR shock strut relating MR yield stress to the MR shock strut force and strut velocity is formulated. Using the developed governing equations and inverse model, a PID controller is formulated to reduce the acceleration of the system. Controlled performance of the simulated MR landing gear system is demonstrated and compared with that of passive system