Showing papers on "Landing gear published in 2011"

Automated inspection of aircraft landing gear internal fluid levels

Abstract: A system for use in monitoring, measuring, computing and displaying the volumes of internal liquid and gas within a telescopic aircraft landing gear strut. Pressure sensors and temperature sensors and motion sensors are mounted in relation to each of the landing gear struts to monitor, measure and record the impact movement and rates of internal landing gear strut fluids; experienced by landing gear struts, as the aircraft landing gear initially come into contact with the ground. The computer of this system measures the compression experienced by each landing gear strut and determines if the landing gear strut is improperly serviced with either excess or deficient volumes of hydraulic oil and nitrogen gas. Additional features include automating the inspections required to aircraft landing gear, prior to flight, during flight and during landing events.

System and method to assess and report the health of landing gear related components

Abstract: The different advantageous embodiments provide an apparatus comprising a number of landing gear components for a vehicle, a number of systems, and a number of processor units. The number of systems is configured to generate data about the number of landing gear components and the vehicle. The number of processor units is configured to monitor the data and manage health of the number of landing gear components.

Recent Developments at the Numerical Simulation of Landing Gear Dynamics

Abstract: Aircraft landing gears support the aircraft during ground operations, including take-off, landing impact, taxiing, gate handling and maintenance Mostly for reasons of minimum mass and ground clearance, landing gears are slender structures which exhibit a considerable dynamic response to ground load excitations As the landing gear is one of the few systems on the aircraft without redundancies, the knowledge of landing gear dynamics is crucial for aircraft design and aircraft safety Simulation of landing gear dynamics is a cornerstone of aircraft loads analysis, as well for vertical loads resulting from touch-down as for longitudinal and lateral loads resulting from braking, steering and towing Another important field of interest is landing gear vibrations like gear walk and shimmy Those phenomena can be brake induced or result from tire spin-up at touch-down or simply from a coupling of dynamics of the running tire and structural mechanics of the landing gear leg All those effects strongly depend on a number of parameters such as aircraft speed, landing gear vertical deflection, tire pressure and wear of the parts Many of those parameters can only be estimated and might change during the operation of the aircraft Numerical investigation is thus a challenging task Analysis methods exist both in the frequency domain and in the time domain As stability analysis is straight forward in frequency domain methods, this approach is still often used However, in many cases nonlinearities are dominant which lead to limit-cycle characteristics of the vibrations Here, multibody modelling or a mixture of multibody and finite element modelling including time domain simulation is used In the article, a general outline is given of how vibration problems in landing gears can be treated by numerical analysis methods The article will start with a classification of typical problems, give a short overview of classical papers, and explain typical approaches In addition, alternative approaches for stability analysis and for the detection of limit-cycle oscillations as well as state-of-the-art modelling approaches will be presented

Integrated electric motor and gear in an aircraft wheel

Abstract: A wheel design is provided for an aircraft landing gear wheel that is configured to maximize the space available within a landing gear wheel well to support a geared motor assembly that drives the aircraft wheel when the aircraft is on the ground. The wheel includes inboard and outboard support walls that are spaced apart a selected distance along the wheel axle so that the geared motor assembly components are substantially completely contained within the wheel space defined by the support walls. The preferred motor driver assembly includes an electric motor and a gear and clutch assembly operatively connected to the wheel to drive the wheel and move the aircraft on the ground. The wheel and motor driver assembly described herein may be retrofitted in an existing aircraft wheel without changing existing landing gear components, including tires, piston, and axle.

Structural Analysis of a Composite Target-drone

Abstract: A finite element analysis for the wing and landing gear of a composite target-drone air vehicle was performed. For the wing analysis, two load cases were considered: a 5g symmetric pull-up and a -1.5g symmetric push-over. For the landing gear analysis, a sinking velocity of 1.4 m/s at a 2g level landing condition was taken into account. MSC/NASTRAN and LS-DYNA were utilized for the static and dynamic analyses, respectively. Finite element results were verified by the static test of a prototype wing under a 6g symmetric pull-up condition. The test showed a 17% larger wing tip deflection than the finite element analysis. This difference is believed to come from the material and geometrical imperfections incurred during the manufacturing process.

Fuel-Efficient Descent and Landing Guidance Logic for a Safe Lunar Touchdown

Abstract: The landing of a crewed lunar lander on the surface of the Moon will be the climax of any Moon mission. At touchdown, the landing mechanism must absorb the load imparted on the lander due to the vertical component of the lander’s touchdown velocity. A large horizontal velocity must also be avoided because it could cause the lander to tip over, risking the life of the crew. To be conservative, the worst-case lander’s touchdown velocity is always assumed in designing the landing mechanism, making it very heavy. Fuel-optimal guidance algorithms for soft planetary landing have been studied extensively. In most of these studies, the lander is constrained to touchdown with zero velocity. With bounds imposed on the magnitude of the engine thrust, these optimal control solutions typically have a “bang-bang” thrust profile: the thrust magnitude “bangs” instantaneously between its maximum and minimum magnitudes. But the descent engine might not be able to throttle between its extremes instantaneously. There is also a concern about the acceptability of “bang-bang” control to the crew. In our study, the optimal control of a lander is formulated with a cost function that penalizes both the touchdown velocity and the fuel cost of the descent engine. In this formulation, there is not a requirement to achieve a zero touchdown velocity. Only a touchdown velocity that is consistent with the capability of the landing gear design is required. Also, since the nominal throttle level for the terminal descent sub-phase is well below the peak engine thrust, no bound on the engine thrust is used in our formulated problem. Instead of bang-bang type solution, the optimal thrust generated is a continuous function of time. With this formulation, we can easily derive analytical expressions for the optimal thrust vector, touchdown velocity components, and other system variables. These expressions provide insights into the “physics” of the optimal landing and terminal descent maneuver. These insights could help engineers to achieve a better “balance” between the conflicting needs of achieving a safe touchdown velocity, a low-weight landing mechanism, low engine fuel cost, and other design goals. In comparing the computed optimal control results with the preflight landing trajectory design of the Apollo-11 mission, we noted interesting similarities between their landing performance.

Electric motor integrated with a wheel

Abstract: An integral motor and wheel assembly for aircraft landing gear is provided that includes an electric motor packaged within at least one gear wheel and configured to fit completely within the space provided in an existing aircraft for the landing gear components. The motor is positioned within the wheel to minimize the spin-up weight and to maximize the space within a given volume allocated for the motor. Installation of this motor and gear wheel assembly in an existing aircraft landing gear is designed to permit the continued use of existing landing gear components, including tires, axles, and pistons, so that the assembly can be easily retrofitted into existing aircraft.

Monitoring systems and methods for aircraft landing gear

Abstract: A system and method for monitoring loads applied to aircraft landing gear structure. The method includes the step of interrogating at least one sensor positioned proximate the landing gear structure by way of data acquisition circuitry to yield strain data. The method further includes the step of instructing the data acquisition circuitry with respect to a sampling rate and data resolution for interrogation.

Airplane landing gear with deflected airplane wheel retraction jack

Abstract: The invention discloses an airplane landing gear with a deflected airplane wheel retraction jack, belonging to the technical field of airplane landing gears. The airplane landing gear with a deflected airplane wheel retraction jack mainly comprises the integral structure of a landing gear main leg, which is composed of a landing gear main leg outer cylinder (3), a buffer piston rod (15), an upper torque arm (16), a lower torque arm (17), a hub (13) and a tyre (14). The airplane landing gear also comprises the retraction rod system of the landing gear, which is composed of an upper locking stay bar (9), a lower locking stay bar (10), an upper side stay bar (7), a lower side stay bar (8), a lug (6), a first lantern ring (4) and a second lantern ring (5); and a retraction actuator cylinder (S) and an unlocking actuator cylinder (J) form the retraction power plant of the landing gear. The invention realizes the oblique and front retraction mode of the landing gear; meanwhile, the retraction mechanism also realizes the mode that the tyre rotates around the axis of the buffer outer cylinder, and thus the tyre rotates to the horizontal position when the landing gear is retracted in an airfoil, thereby solving the problem of large occupied space of the lading gear tyre.

Vertically retracting side articulating landing gear for aircraft

Abstract: A side articulating main landing gear assembly for an aircraft is disclosed which includes a wheel axle fitting oriented in a horizontal plane when the landing gear is in an extended condition deployed from a landing gear bay of the aircraft, a tire supported on the wheel axle fitting and oriented in a vertical plane when the landing gear is in the extended condition, a shock absorber adapted to stroke between an extended state and a compressed state upon landing the aircraft, a set of articulating links connected to the wheel axle fitting, the shock absorber and the aircraft, and configured to maintain the tire in a vertical plane as the shock absorber strokes between the extended state and the compressed state, a set of tire planing links connected to the wheel axle fitting and the articulating links, and configured to maintain the wheel axle fitting in a horizontal plane as the shock absorber strokes between the extended state and the compressed state, and a drive crank connected to the shock absorber, the tire planing links, the articulating links and the aircraft, for moving the landing gear assembly between the extended condition and an inverted retracted condition stowed in the landing gear bay.

Wheel Structure for Integrating an Electric Drive Motor

Abstract: A wheel design is provided for an aircraft landing gear wheel that is configured to maximize the space available within a landing gear wheel well to support a motor driver assembly that drives the aircraft wheel when the aircraft is on the ground. The wheel includes inboard and outboard support walls that are spaced apart a selected distance along the wheel axle so that the motor driver assembly components are substantially completely contained within the wheel space defined by the support walls. The preferred motor driver assembly includes an electric motor and a gear and clutch assembly operatively connected to the wheel to drive the wheel and move the aircraft on the ground. The wheel and motor driver assembly described herein may be retrofitted in an existing aircraft wheel without changing existing landing gear components, including tires, piston, and axle.

Skid landing gear system

Abstract: A skid landing gear assembly is provided. One embodiment of the landing gear assembly may include a first and a second skid member, and a forward and an aft cross member. The forward and aft cross-members may have integrated attachment members coupled to a forward portion and an aft portion of the first and second skid members. In more particular embodiments, the cross-members may be beam members with open cross-sections, and the skid members may be beam members with a closed cross-section.

Unsteady Flow and Aerodynamic Noise Analysis around JAXA Landing Gear Model by Building-Cube Method

Abstract: In this paper, the airframe noise from the landing gear designed by Japan Aerospace Exploration Agency (JAXA) is investigated by incompressible Navier-Stokes flow solver using the Building-Cube Method (BCM) and by the Curle s equation. The BCM is a multiblock-structured Cartesian mesh solver, and the computational domain is composed of assemblage of various size of building blocks where small blocks are used to capture flow features in detail. By using the BCM and the Curle s equation, it is easy to generate a mesh and to perform the flow simulation around the landing gear which has a complex geometry. In this paper, the influence of some tiny components of the landing gear model, including the torque link positions and the wheel cap geometry, on the aerodynamic noise is discussed. It is shown that the flow field and the aerodynamic sound are significantly influenced by the wheel cap geometry whether the wheel had the seal cap or the cap with tear holes. From the comparisons of the pressure fluctuation on the LEG surface and of the streamlines, these phenomena are found to be attributed to the reduction of the vortices and the delay of the flow separation outside the tire caused by the flow induced from the inside to the outside of the tire through the tear holes. The importance of the grid resolution is also discussed.

Adaptive computation of aeroacoustic sources for a rudimentary landing gear using lighthill's analogy

Abstract: We present our simulation results for the benchmark problem of the ow past a Rudimentary Landing Gear (RLG) using a General Galerkin (G2) nite element method, also referred to as Adaptive DNS/LES. ...

Strut lock mechanism in landing position of airplane landing gear

Abstract: The utility model belongs to the airplane landing gear technology, and relates to an improvement of a strut lock in the landing position of an airplane landing gear The airplane landing gear strut lock mechanism provided by the utility model comprises lug pieces (10), a compression spring (11), an upper strut (12), a bracket (13), a knuckle bearing (14), a roller (15), a lower strut component (16), an electric door (17) and a lock hook (20), wherein a connecting hole of a main connecting double lug (10) is connected with a retractable action cylinder; and unlocking and locking of a strut lock can be performed through the retractable action cylinder When the landing gear is in the landing position, the lock hook (20) is clamped on a lug boss of the upper strut (12) through the retractable action cylinder, and at the same time, the movement of the lower strut component (16) is limited by the roller (15) installed on the upper strut (12) The airplane landing gear strut lock mechanism provided by the utility model has the advantages of simple structure, small occupied area and light weight, is fixed reliably, and can undergo and deliver ground loads, thereby being very suitable for light airplanes

Modelica Landing Gear Modelling and On-Ground Trajectory Tracking with Sliding Mode Control

Abstract: A control system for an aircraft taxiing on ground based on sliding mode has been developed. The controller is capable to track the trajectory assigned in terms of longitudinal velocity and yaw rate and to drive an aircraft equipped with electric motors in the main gear as well as conventional brakes and nose gear steering. In addition, it can successfully handle saturation of the actuators. The algorithm is shown to be robust against parameter uncertainties (e.g. aircraft mass) as well as low friction coefficients at the interface tyre-ground. In order to test the tracking controller, an accurate virtual aircraft model has been designed in Modelica, with particular attention to the landing gears.

Landing gear vibration absorber for a helicopter and method of operating said landing gear vibration absorber

Abstract: The invention is related to a landing gear vibration absorber (1) of a helicopter (2) with a landing gear (3) comprising a pair of skids (4, 5) and at least one cross tube (6, 7) for mounting the skids (4, 5) to a helicopter's fuselage (8). At least one spring-mass system (10, 20, 24) is mounted to the landing gear (3). Said at least one spring-mass system (10, 20, 24) is tuned to the helicopter's main excitation frequency and said at least one spring-mass system (10, 20, 24) being located at or near at least one antinode of the landing gear (3). The invention is related as well to a method of operating a landing gear vibration absorber (1) of a helicopter (2).

Systems and methods for detecting landing gear ground loads

Abstract: There is provided a system for predicting loading of a landing gear including, a plurality sensors positioned proximate to the landing gear. The plurality of sensors measure strain applied to the landing gear, and each sensor yielding strain data. The system further includes a processor that receives the strain data from the plurality of sensors and predicts at least one ground load based on strain data. There is further provided a method for predicting loading of a landing gear. The method includes powering a plurality of sensors located proximate to a landing gear structure, interrogating the plurality of sensors via data acquisition circuitry to yield strain data, instructing the data acquisition circuitry as to a sampling rate and data resolution to be used for the interrogating, and, finally, processing the strain data to predict a ground load.

Vertical takeoff and landing aircraft

Abstract: An aircraft has a fuselage, a lifting free wing, and a nose section. The fuselage has a front end, a rear end, and a longitudinal axis. The lifting free wing is pivotally connected to the fuselage with a pivot. The nose section is pivotally mounted on the front end of the fuselage, and includes a pair of engines, and a pair of counter-rotating propellers. A canard free wing is pivotally connected to the nose section with a pivot. A pair of vertical stabilizers are mounted on the rear end of the fuselage and each includes a rudder and a pair of landing gear.

Integrated Vehicle Wheel Motor Structured to Manage Heat

Abstract: A wheel design with heat management capability is provided for an aircraft landing gear wheel that is specifically configured to maximize the space available within a landing gear wheel well to support a geared motor assembly that drives the aircraft wheel when the aircraft is on the ground. A thermal interface between the geared motor assembly and a support wall effectively directs heat generated by brakes, motor, or gear components through the wheel ultimately to be shed entirely outside the aircraft to prevent damage to the wheel and motor components. The heat dissipating wheel and motor driver assembly described herein may be retrofitted in an existing aircraft wheel without changing existing landing gear components, including tires, piston, and axle.

Low-Altitude Operation of Unmanned Rotorcraft.

Abstract: Currently deployed unmanned rotorcraft rely on preplanned missions or teleoperation and do not actively incorporate information about obstacles, landing sites, wind, position uncertainty, and other aerial vehicles during online motion planning. Prior work has successfully addressed some tasks such as obstacle avoidance at slow speeds, or landing at known to be good locations. However, to enable autonomous missions in cluttered environments, the vehicle has to react quickly to previously unknown obstacles, respond to changing environmental conditions, and find unknown landing sites. We consider the problem of enabling autonomous operation at low-altitude with contributions to four problems. First we address the problem of fast obstacle avoidance for a small aerial vehicle and present results from over a 1000 rims at speeds up to 10 m/s. Fast response is achieved through a reactive algorithm whose response is learned based on observing a pilot. Second, we show an algorithm to update the obstacle cost expansion for path planning quickly and demonstrate it on a micro aerial vehicle, and an autonomous helicopter avoiding obstacles. Next, we examine the mission of finding a place to land near a ground goal. Good landing sites need to be detected and found and the final touch down goal is unknown. To detect the landing sites we convey a model based algorithm for landing sites that incorporates many helicopter relevant constraints such as landing sites, approach, abort, and ground paths in 3D range data. The landing site evaluation algorithm uses a patch-based coarse evaluation for slope and roughness, and a fine evaluation that fits a 3D model of the helicopter and landing gear to calculate a goodness measure. The data are evaluated in real-time to enable the helicopter to decide on a place to land. We show results from urban, vegetated, and desert environments, and demonstrate the first autonomous helicopter that selects its own landing sites. We present a generalized planning framework that enables reaching a goal point, searching for unknown landing sites, and approaching a landing zone. In the framework, sub-objective functions, constraints, and a state machine define the mission and behavior of an UAV. As the vehicle gathers information by moving through the environment, the objective functions account for this new information. The operator in this framework can directly specify his intent as an objective function that defines the mission rather than giving a sequence of pre-specified goal points. This allows the robot to react to new information received and adjust its path accordingly. The objective is used in a combined coarse planning and trajectory optimization algorithm to determine the best patch the robot should take. We show simulated results for several different missions and in particular focus on active landing zone search. We presented several effective approaches for perception and action for low-altitude flight and demonstrated their effectiveness in field experiments on three autonomous aerial vehicles: a 1m quadrocopter, a 36m helicopter, and a hill-size helicopter. These techniques permit rotorcraft to operate where they have their greatest advantage: In unstructured, unknown environments at low-altitude.

Steering collar locking mechanism for retractable aircraft nose landing gear

Abstract: A retractable nose landing gear assembly for an aircraft is disclosed, which includes an elongated strut cylinder defining a longitudinal axis, an elongated strut piston mounted for reciprocal movement relative to the strut cylinder between a shrunk condition when the landing gear is retracted into a wheel well of an aircraft and a fully extended condition when the landing gear is deployed from the wheel well for landing the aircraft, and wherein the strut piston is mounted for rotation about the axis of the strut cylinder for steering the aircraft while taxiing on the ground, and a locking mechanism operatively associated with the strut cylinder for preventing rotation of the strut piston about the axis of the strut cylinder when the landing gear is in a shrunk condition retracted within the wheel well of the aircraft during flight.

Investigation of engine tones in flight

Abstract: Acoustic fly-over measurements with Boeing 747-400 aircraft have been performed in order to extend an existing noise data base for Airbus A319/20 and MD-11 aircraft with another widely used wide-body aircraft. The data were recorded with a large multi-arm spiral microphone array with 238 microphones which extended over an area of 42 by 35 m. The flight trajectories were determined using a combination of onboard flight recorder and GPS data and an array of laser distance meters on the ground. A linearised trajectory of the aircraft was determined for every fly-over in order to calculate frequency spectra for different emission angles at emission time by compensating the Doppler effect. Sound source maps were calculated using the standard beamforming algorithm and a deconvo- lution method for moving sources. Fly-over measurements were performed with different configurations in order to analyse airframe and engine noise sources separately. In this paper, the main focus is on the analysis of fly-overs with different engine speeds, but also, some results for landing gear noise are presented.

A landing gear

Abstract: A landing gear (10), including an elongate axle (16a) pivotally (18) connected to a bogie beam (14), the landing gear further including a locking device (30) for locking the axle at a substantially fixed orientation with respect to the bogie beam, the locking device including first and second barrier arms (32c, 34c) that are movable between a first configuration, in which they define a barrier so as to maintain the axle in the substantially fixed orientation with respect to the bogie beam, and a second configuration, in which the axle may pivot about the bogie beam.

Aero-acoustic optimisation method for complex-section mechanical parts and corresponding mechanical part and landing gear

Abstract: An apparatus and method are provided for reducing the drag caused by a complex-section part in an airflow, for example the landing gear of an aircraft, making it possible to optimize the lift/drag ratio and to reduce the aerodynamic noise by reducing the local noise source. To do so, the complex-section part is masked with a special casing. More specifically, the aero-acoustically optimized complex-section metal mechanical part is fitted with an aerodynamically shaped cover made of several longitudinal parts articulated with hinges to facilitate their installation. This cover is attached to at least two supports placed away from one another along the axis of the part, each support locally mating with the section of the part.

Modeling of landing of a helicopter with skid undercarriage with regard for the second landing impact

Abstract: A technique is suggested for calculating the helicopter spatial motion and the stress-strain state of a skid landing gear in the course of landing with regard for the second landing impact; geometric, material and design nonlinearity of undercarriage springs deformation is taken into account. The comparison between the analysis results and experimental data is presented.