Showing papers on "Landing gear published in 2013"

Influence of Variable Side-Stay Geometry on the Shimmy Dynamics of an Aircraft Dual-Wheel Main Landing Gear ∗

Abstract: Commercial aircraft are designed to fly but also need to operate safely and efficiently as vehicles on the ground. During taxiing, take-off, and landing the landing gear must operate reliably over a wide range of forward velocities and vertical loads. Specifically, it must maintain straight rolling under a wide variety of operating conditions. It is well known, however, that under certain conditions the wheels of the landing gear may display unwanted oscillations, referred to as shimmy oscillations, during ground maneuvers. Such oscillations are highly unwanted from a safety and a ride-comfort perspective. In this paper we conduct a study into the occurrence of shimmy oscillations in a main landing gear (MLG) of a typical midsize passenger aircraft. Such a gear is characterized by a main strut attached to the wing spar with a side-stay that connects the main strut to an attachment point closer to the fuselage center line. Nonlinear equations of motion are developed for the specific case of a two-wheeled M...

A finite element based tool chain for structural sizing of transport aircraft in preliminary aircraft design

Abstract: This paper introduces a fully parameterized finite element based tool chain for the structural sizing of transport aircraft. The chain consists of two model generators, a coupling module, a loads module for the computation of aerodynamic, fuel, landing gear and engine loads as well as a structural analysis and sizing algorithm. The finite element models of the wing and the empennage are created by the ELWIS multi-model generator, while the corresponding fuselage model is created using the TRAFUMO model generator. The structural coupling comprises the detailed modeling of all key structural elements of the center fuselage area including a keelbeam, bulkheads, sideboxes and lateral panels. The empennage coupling structure includes a reinforcement framework, reinforced frames and a mounting structure for the horizontal tail plane trim device. To establish suitability in preliminary aircraft design, a knowledge-based approach is chosen that enables a fully automatic model generation and coupling on a minimum set of required input parameters. As a central data format for input and output the DLR aircraft parameterization format CPACS is used. Therefore, the chain can be easily embedded in a wider MDA/MDO approach for overall preliminary aircraft design. Finally, first static sizing results are discussed and different validation methods for the static sizing algorithm are presented, including a comparison with a validated analytical method.

Rotorcraft Slope Landings with Articulated Landing Gear

Abstract: Rotorcraft are uniquely suited to operate in remote areas, primarily due to their ability to perform vertical takeoffs and landings. However, the slope of the landing surface can severely limit viable landing areas. Adding robotic articulated landing gear to a rotorcraft increases the number of degrees of freedom that can be used to land on an irregular surface. Instead of relying on the rotor thrust magnitude and direction to land safely, the gear can also be used to conform more closely with the ground, potentially allowing for quicker and safer landings. The current work presents a multi-body simulation tool to simulate the dynamics of a rotorcraft with robotic gear landing on sloped terrain, including overall system motion, loads computation, and stress analysis. Through dynamic simulation and analysis it is shown that a robotic legged landing gear system can substantially expand the slope and type of terrain for landing with a small increase in landing gear system weight.

Numerical continuation analysis of a three-dimensional aircraft main landing gear mechanism

Abstract: A method of investigating quasi-static landing gear mechanisms is presented and applied to a three-dimensional aircraft main landing gear mechanism model. The model has 19 static equilibrium equations and 20 equations describing the geometric constraints in the mechanism. In the spirit of bifurcation analysis, solutions to these 39 steady-state equations are found and tracked, or continued, numerically in parameters of interest. A design case study is performed on the landing gear actuator position to demonstrate the potential relevance of the method for industrial applications. The trade-off between maximal efficiency and peak actuator force reduction when positioning the actuator is investigated. It is shown that the problem formulation is very flexible and allows actuator force, length and efficiency information to be obtained from a single numerical continuation computation with minimal data post-processing. The study suggests that numerical continuation analysis has potential for investigating even more complex landing gear mechanisms, such as those with more than one sidestay.

CFD/CAA Analysis of the LAGOON Landing Gear Configuration

Abstract: The unsteady flow field about the ONERA/Airbus LAGOON two-wheel landing gear configuration and the associated aerodynamic noise generation are computed using a hybrid approach in which the flow field is provided by a Lattice-Boltzmann simulation, and the noise radiation is computed using the Ffowcs-Williams & Hawkings analogy. A detailed validation study is carried out, following the guidelines of the second workshop on benchmark problems for airframe noise computations, and deploying the complete experimental database for detailed comparisons. The effect of grid resolution on both nearand far-field results is investigated, showing the physical consistency of the numerical model. In addition, an assessment of the numerical prediction is carried out by computing the maximum perceived noise level along a nominal approach trajectory. Finally, an unsteady flow mechanism, never reported so far, involving the onset of cavity modes in the two facing rim cavities is analyzed in detail and correlated with the generation of tonal noise components.

Numerical simulation of landing gear noise via weakly coupled CFD-CAA calculations

Abstract: The present work is relevant from the numerical prediction of aircraft noise via aeroacoustics hybrid methods. It is part of a more extensive effort, which final objective is the development of a robust and accurate CFD-CAA weak coupling methodology. Within this framework, we focus here on the so-called surface coupling approach, a technique that allows conducting weakly coupled CFD-CAA calculations. Such approach (which had been previously developed and validated on simpler cases) is here applied to a ralistic problem of aircraft noise, given by the acoustic emission of a nose landing gear in approach flight (a configuration that was addressed in the Airbus LAGooN program). For doing so, several preliminary tasks are first addressed, which are carefully handled and thoroughly detailed. Two CFD-CAA coupled calculations are then conducted, both being based on i) a same CFD dataset coming from an unsteady aerodynamic calculation (zonal DES), and ii) two distinct CAA calculations of different characteristics ; first, a CFD-CAA calculation is conducted for the so-called ‘baseline’ configuration (i.e. isolated gear within a free-field flow), so as to validate the coupling procedure, as well as to generate a reference solution for subsequent assessment of the mean flow effects induced by the experimental set-up. The validation of the coupling procedure is conducted via a direct comparison of the CFD-CAA results with either experimental or numerical (CFD, CFD-FWH) outputs obtained in the near-, mid, and/or far-field. With the view of assessing the mean flow effects, an alternative CFD-CAA calculation is then performed, which incorporates the realistic sheared jet flow characterizing the anechoic facility. This allows assessing the (partial) convection and refraction effects induced by such jet mean flow, which helps underscoring better the relevance of the present CFD-CAA hybrid approach when it comes to handle real-life noise problems.

DDES and Acoustic Prediction of Rudimentary Landing Gear Experiment Using Unstructured Finite Volume Methods

Abstract: The far-field noise produced by a Rudimentary Landing Gear (RLG) was investigated using Delayed Detached Eddy Simulation (DDES) coupled with a Ffowcs-Williams Hawkings (FWH) integral. Computational results are presented for the RLG geometry using three unstructured grids of quasi-nested refinement. The geometry consists of a square post attached to an axle supporting four wheels, which is entirely suspended from an inviscid flat plate. The Reynolds number was fixed at 106 based on the wheel diameter and freestream properties. The freestream Mach number was fixed at 0.115. The effect of grid resolution using a low dissipation scheme is examined in terms of both aerodynamic forces as well as acoustic spectra. Flow visualizations reveal rich three-dimensional unsteady content and the pattern of wall-pressure fluctuations are consistent with experimental observations. In general the FWH equation predictions of the far-field noise are in very good agreement with acoustic microphone measurements. From these preliminary results it appears that DDES has the potential to become a viable tool for evaluating low noise gear designs during the early design phases before wind tunnel and flight testing have commenced. Efforts are underway to extend the approach to more complex landing gear geometries.

Semi-active control of aircraft landing gear system using H-infinity control approach

Abstract: The landing of an aircraft is one of the most critical operations because it directly affects the passenger safety and comfort. During landing, the aircraft fuselage undergoes excessive vibrations that cause the safety and the comfort problem and hence need to be suppressed quickly. A semi-active control system of a landing gear suspension by using Magnetorheological damper can solve the problem of excessive vibrations effectively. In this paper, a switching technique is developed in the simulation of the landing procedure which enables the system to switch from the single degree of freedom to three degrees of freedom system in order to simulate the sequential touching of the two wheels of the main landing gears and the nose landing gear wheels with the ground. A semi-active Magnetorheological damper is developed using two different controllers namely linear quadratic regulator and the H∞. Spencer model is used to predict the dynamic behavior of the Magnetorheological damper. The results of the designed controllers are compared to study the performance of the controllers in reducing the overshoot of the bounce response as well as the bounce rate response. The simulation results validated the improved performance of the robust controller compared to the optimal control strategy when the aircraft is subjected to the disturbances during landing.

Vibration Attenuation of Magnetorheological Landing Gear System with Human Simulated Intelligent Control

Abstract: Due to the short duration of impulsive impact of an aircraft during touchdown, a traditional landing gear can only achieve limited performance. In this study, a magnetorheological (MR) absorber is incorporated into a landing gear system; an intelligent control algorithm, a human simulated intelligent control (HSIC), is proposed to adaptively tune the MR absorber. First, a two degree-of-freedom (DOF) dynamic model of a landing gear system featuring an MR absorber is constructed. The control model of an MR damper is also developed. After analyzing the impact characteristic during touchdown, an HSIC is then formulated. A genetic algorithm is adopted to optimize the control parameters of HSIC. Finally, a numerical simulation is performed to validate the proposed damper and the controller considering the varieties of sink velocities and sprung masses. The simulations under different scenarios show that the landing gear system based on the MR absorber can greatly reduce the peak impact load of sprung mass within the stroke. The biggest improvement of the proposed controller is over 40% compared to that of skyhook controller. Furthermore, HSIC exhibits better adaptive ability and strong robustness than skyhook controller under various payloads and sink velocities.

Investigating landing gear noise using fly-over data: the case of a Boeing 747-400

Abstract: Investigation of the landing gear noise of the Boeing 747-400 in flight Comparison of different fly-over velocities in order to obtain a scaling law for the Sound pressure Level based on microphone Array measurements

Airport capacity from takeoff assist

Abstract: Systems and methods for ground-based aircraft thrust systems are provided. In particular, some embodiments use an electromechanical thrust assembly to accelerate aircraft using ground-based energy for takeoff. The assembly can include one or more sleds, one or more maglev tracks, and/or one or more linear motors. Airplanes are loaded onto a sled (e.g., a saddle-shaped sled) that supports and balances the airplane instead of the landing gear aboard the aircraft. The sled levitates above the ground using high-density permanent magnet arrays. Magnetic levitation forces are varied along the assembly to account for lift provided by airflow over the wings. An aircraft thrust system includes a magnetically levitated saddle-shaped sled with airbags that support an aircraft during takeoff acceleration coupled with a linear motor that spans the length of the distance needed for takeoff.

Fly-over source localization on civil aircraft

Abstract: In June 2012, fly-over measurements were performed on landing aircraft at P.-E. Trudeau Montreal airport. A custom-made measurement system developed by GAUS (Groupe d’Acoustique de l’Universite de Sherbrooke) including a 95-microphone array with its related audio pre-amplifying and recording system have been used to acquire a comprehensive data set of over 300 flyovers during a five-day period. A particular focus has been made on Bombardier CRJ200 aircraft for which several flight conditions have been measured. Trajectories of aircraft were tracked by a synchronized 2-camera system. Precise localizations of landing gear, flaps and engine have been obtained as preliminary results. The article details source identification results as well as the complete experimental set-up and the algorithms used in de-dopplerization and Beamforming computations.

Drive device for aircraft using tripod, landing gear and aircraft

Abstract: The utility model is applicable to the field of aircraft structures, and provides a drive device for an aircraft using a tripod, a landing gear and an aircraft. The drive device comprises a transmission mechanism and a power device used for driving the transmission mechanism to move; the transmission mechanism comprises a base, a driven mechanism and a driving mechanism, wherein the base comprises a main body part and a first base connecting part arranged at the main body part; the driven mechanism is used for driving the tripod to move; the driving mechanism is connected with the power device and used for driving the driven mechanism to move; and the first base connecting part is connected with one end of the driven mechanism, and the other end of the driven mechanism is connected with the driving mechanism. The landing gear comprises a landing gear body and a tripod which is connected to the landing gear body through the drive device. The aircraft comprises an aircraft body and the landing gear. According to the drive device for the aircraft using the tripod, the landing gear and the aircraft, the drive device can drive the tripod to move relative to the landing gear body and is simple in structure and high in structural reliability.

Aircraft landing gear longitudinal force control

Abstract: An aircraft landing gear longitudinal force control system (20) for an aircraft having landing gears with braking and/or driving wheel(s) The system includes an error- based force controller (21) having feedback for minimising any error between the demanded force (Fx*) and the actual force (Fx_LG) achieved by the force control system The feedback may be derived from force sensors on the landing gear for direct measurement of the landing gear longitudinal force The force control system may include an aircraft level landing gear total force controller and/or a landing gear level force controller for each actuated landing gear

Hybrid Wing Body Aircraft Acoustic Test Preparations and Facility Upgrades

Abstract: NASA is investigating the potential of acoustic shielding as a means to reduce the noise footprint at airport communities. A subsonic transport aircraft and Langley's 14- by 22-foot Subsonic Wind Tunnel were chosen to test the proposed "low noise" technology. The present experiment studies the basic components of propulsion-airframe shielding in a representative flow regime. To this end, a 5.8-percent scale hybrid wing body model was built with dual state-of-the-art engine noise simulators. The results will provide benchmark shielding data and key hybrid wing body aircraft noise data. The test matrix for the experiment contains both aerodynamic and acoustic test configurations, broadband turbomachinery and hot jet engine noise simulators, and various airframe configurations which include landing gear, cruise and drooped wing leading edges, trailing edge elevons and vertical tail options. To aid in this study, two major facility upgrades have occurred. First, a propane delivery system has been installed to provide the acoustic characteristics with realistic temperature conditions for a hot gas engine; and second, a traversing microphone array and side towers have been added to gain full spectral and directivity noise characteristics.

Landing gear for unmanned aerial vehicle

Abstract: The utility model discloses a landing gear for an unmanned aerial vehicle The landing gear comprises a landing gear base, a top surface and a support wall The base is connected with the top surface through the support wall, and is provided with a battery inlet hole Battery plugs are arranged on the base on the two sides of the battery inlet hole A battery compression plate is arranged on the support wall Balls are arranged on vertex angles of the battery compression plate Ball grooves are formed in the support wall Springs are arranged between the battery compression plate and the top surface According to the landing gear for a miniature multi-rotor unmanned aerial vehicle, stable landing in a complex environment, the blind plugging of a battery and combination with a landing gear fixing device of a battery replacement platform are realized

Landing gear force and moment distributor

Abstract: The present invention provides a landing gear force and moment distributor system (20) for an aircraft having a landing gear including a pair of bogies arranged symmetrically about the longitudinal axis, each bogie having an actuator arranged to brake and/or drive one or more wheels. The force distribution system comprises a distribution module arranged to: receive an input demand including a longitudinal force input demand corresponding to a desired braking or driving force along the longitudinal axis for the landing gear and a moment input demand corresponding to a desired moment about the vertical axis for the landing gear; and to use the received input demand to calculate an output command comprising, for each bogie, a longitudinal force output command corresponding to a braking or driving force along the longitudinal axis to be applied to said bogie to achieve the longitudinal force input demand, and a moment output command corresponding to a braking or driving force along the longitudinal axis to be applied to said bogie to achieve the moment input demand.

Aircraft landing gear cooling system

Abstract: According to one embodiment, an apparatus for cooling at least one landing gear brake of an aircraft in flight is described. The apparatus includes an air handling assembly that is coupled to the aircraft. The air handling assembly includes at least one air inlet port. The apparatus also includes an air delivery assembly that is in air receiving communication with the air handling assembly. The air delivery assembly includes at least one nozzle that is configured to direct air into a first space adjacent a first side of the landing gear brake to create an air pressure differential across the landing gear brake.

Aircraft thrust, assembly, and methods

Abstract: Systems and methods for ground-based aircraft thrust systems are provided. In particular, some embodiments use an electromechanical thrust assembly to accelerate aircraft using ground-based energy for takeoff. The assembly can include one or more sleds, one or more maglev tracks, and/or one or more linear motors. Airplanes are loaded onto a sled (e.g., a saddle-shaped sled) that supports and balances the airplane instead of the landing gear aboard the aircraft. The sled levitates above the ground using high-density permanent magnet arrays. Magnetic levitation forces are varied along the assembly to account for lift provided by airflow over the wings. An aircraft thrust system includes a magnetically levitated saddle-shaped sled with airbags that support an aircraft during takeoff acceleration coupled with a linear motor that spans the length of the distance needed for takeoff.

Numerical Simulations of Flow over a Landing Gear with Noise Reduction Devices using the Lattice-Boltzmann Method

Abstract: Computational methods were used to predict the noise produced from flow around a full-scale, fully-dressed two-wheel main landing gear. Flow simulations were performed using a commercially available code based on the Lattice-Boltzmann Method. Far-field sound predictions were obtained using an acoustic analogy. The aerodynamic and acoustic simulation results for the baseline geometry were verified through comparisons with wind tunnel test results. In both the simulations and the experiments, the dominant noise sources were found to be located along the main strut and piston, downstream of the light and torque arms. Various low-noise landing gear configurations were investigated, each of which aiming to minimize the impingement of upstream components’ wakes on downstream surfaces. Simulation results indicated that the modified torque arm geometry yielded the most significant noise reduction from a single design modification. The predicted benefit of the combination of all noise reduction methods was found to be around 3.4 dB.

Aircraft front portion having an improved landing gear bay

Abstract: An aircraft front portion in which the landing gear storage bay is arranged under a cockpit floor. The landing gear bay is mechanically connected to the fuselage frames of the aircraft front portion in order to perform the function of taking up the mechanical forces acting on the fuselage frames under the effect of pressurization. The cockpit floor is thus simplified since it serves solely as a plane for the crew to walk on and it can be lowered so as to release space in the cockpit.

Assembly test vehicle of airplane main landing gear

Abstract: The invention discloses an assembly test vehicle of an airplane nose landing gear, and four universal wheels and five servo electric cylinders are used for achieving six-freedom-degree movement of the nose landing gear and rotation of a strut of the nose landing gear along an axle. The movement amount, along an X axis and a Y axis, of the nose landing gear and the rotation amount, along a Z axis, of the nose landing gear can be adjusted manually and quickly, the movement amount, along the Z axis, of the nose landing gear, the rotation amount, along the X axis and the Y axis, of the nose landing gear and the rotation amount, along the axle, of the strut of the nose landing gear can be adjusted quantitatively through the servo electric cylinders, and the six-freedom-degree movement is achieved through real-time quantitative control. The assembly test vehicle of the airplane nose landing gear is high in freedom degree, easy to position accurately in an assembly process and capable of achieving the quantitative control in the assembly process and flexible manual rapid adjustment, assembly accuracy of the nose landing gear is greatly improved, and assembly time is saved.

Control of ground travel and steering in an aircraft with powered main gear drive wheels

Abstract: A controllable aircraft taxi system is provided that enables the simultaneous control of aircraft autonomous ground movement and direction of aircraft autonomous ground movement. Independently controlled non-engine drive means capable of driving an aircraft landing gear wheel to move an aircraft autonomously on the ground without reliance on the aircraft's main engines are mounted to provide driving torque to aircraft a selected number of main landing gear wheels. The aircraft nose landing gear steering system is provided with steering angle detection and measurement means adapted to communicate with main landing gear wheel non-engine drive means, enabling simultaneous control over both autonomous aircraft ground travel and direction of autonomous aircraft ground travel. The present invention overcomes steering challenges presented by using non-engine drive means on main landing gear wheels to drive aircraft autonomously during taxi.

Fuselage-mounted landing gear assembly for use with a low wing aircraft

Abstract: An aircraft comprises at least one wing comprising a trailing edge flap that is selectively moveable between a stowed position and an extended position. The aircraft also includes a fuselage comprising a first gear door on a side of the fuselage and a second gear door on a bottom of the fuselage. The first gear door is moveable in a gear door envelope between a closed position and an open position. The wing is coupled to the fuselage in a low-wing configuration. A landing gear assembly is coupled to the fuselage and is selectively moveable between a retracted position and a deployed position. The trailing edge flap may be extended simultaneously with, before, or after deployment of the landing gear assembly and opening of the first gear door.