Showing papers on "Landing gear published in 2002"

Landing gear aerodynamic noise prediction using unstructured grids

Abstract: Aerodynamic noise from a landing gear in a uniform flow is computed using the Ffowcs Williams-Hawkings (FW-H) equation. The time accurate flow data on the integration surface is obtained using a finite volume low-order flow solver on an unstructured grid. The Ffowcs Williams-Hawkings equation is solved using surface integrals over the landing gear surface and over a permeable surface away from the landing gear. Two geometric configurations are tested in order to assess the impact of two lateral struts on the sound level and directivity in the far-field. Predictions from the Ffowcs Williams-Hawkings code are compared with direct calculations by the flow solver at several observer locations inside the computational domain. The permeable Ffowcs Williams-Hawkings surface predictions match those of the flow solver in the near-field. Far-field noise calculations coincide for both integration surfaces. The increase in drag observed between the two landing gear configurations is reflected in the sound pressure le...

Microphone array assessment of an isolated, 26%-scale, high-fidelity landing gear

Abstract: An aeroacoustic study of a 26%-scale landing gear model was conducted in the NASA Ames 7- by 10-Foot Wind Tunnel using a phased microphone array. The incorporation of complex parts via stereo lithography produced a model that can mimic full-scale details down to 3 mm. These details include the contours, brake cylinders, bolt holes, and wheel hubs that appear on the real landing gear. Major noise sources were identified and ranked. From the sideline view, the noise levels of the cable harness and torque link were each at least 8 dB above that of a clean configuration. Sources from the more ambiguous fly-over view, such as the front axle, center axle and rear axle regions, were 11 dB above the clean configuration for frequencies below 2000 Hz full-scale. This increment in noise likely included other sources situated behind the truck. Referenced to the clean configuration, the braces and links contributed as much as 8 dB. Tests with a fully sealed fairing on the landing gear suggest, through careful design of major components, a noise reduction of up to 15 dB can be achieved although 2 to 6 dB of noise reduction is probably a more realistic goal. NOMENCLATURE

Research into Landing Gear Airframe Noise Reduction

Abstract: Servere air-traffic constraints are imposed by commercial airports following public complaints about the ever increasing noise impact. This situation lead to renewed emphasis by aviation industry into aircraft noise source research. While the engine noise still dominates during aircraft full-power take-off, it is the airframe noise which represents the essential contributor to the overall flyover noise signature in the landing phase for today's high-bypass ratio engine powered large commercial aircraft. Therefore in Europe a research project was launched aiming at the reduction of landing gear noise, which is the dominant airframe noise component for wide-body aircraft and the subject area of this paper. Based on the knowledge of a state-of-the-art full scale A340 nose- and main-landing gear baseline noise test, realistic noise reduction add-on devices were developed for these gears and the devices' effectiveness tested in a dedicated wind tunnel study. Both farfield noise data were taken and techniques employed for noise source localization. By removing the noise reduction devices orderly, their individual effectiveness were assessed. It was demonstrated that significant noise reduction can be achieved with add-on devices which have been designed to cause minimum interference with respect to the gears' functionality and maintainability.

Acceleration Feedback-Based Active and Passive Vibration Control of Landing Gear Components

Abstract: In this paper, a novel methodology is developed to absorb the vibrations of relatively large-scale aircraft structures such as landing gear components. This is accomplished using a combination of active and passive controls. A system equivalent to a Boeing 747 landing gear break rod is selected as a test bed. The expected goal of this study is to dissipate the fundamental vibration mode of the tube. A beam-type dynamic absorber and a constrained layer damping treatment are used for passive vibration control. Simulations and experimental results are provided for the dynamic absorber case. In addition, full-state feedback along with state estimation based on the “reciprocal state space” method is presented. The plant responses and estimates for both the open loop and closed loop systems are shown in simulations. An optimal controller based on acceleration measurements using piezoelectric actuators is implemented using a hardware in the loop protocol for the active vibration control of the system. The integr...

Validation of a prediction model for aerodynamic noise from aircraft landing gear

Abstract: The continued development of quiet engines is now giving rise to situations where airframe noise is comparable with engine noise at approach. The landing gear is a major contributor to airframe noise, and this paper outlines development and testing of a semi-empirical noise model for predicting the benefit of noise control fairings. The model is based on nondimensional source spectra derived from a data base of full-scale tests on A320 landing gear installed in the DNW wind tunnel and is used to predict the noise reduction potential of a variety of fairings installed on the main and noise gears from an A340 aircraft . The model is found to give good agreement with data and this gives confidence that it may be used as an engineering tool to optimise fairing design. The paper also discusses the way in which the model can provide a framework for incorporating CFD data in the design process and also number of factors which complicate the comparison of noise data from wind tunnel and flyover tests.

Control system and method for a semi-levered landing gear for an aircraft

Abstract: A control system for controlling a tiltable wheel truck of a main landing gear includes an auxiliary strut, a ground mode system operably connected with the aircraft for detecting and providing signals indicative of when the aircraft is on the ground; a takeoff mode system operably connected with the aircraft for detecting and providing signals indicative of when the aircraft is operating in a throttled-up mode; and an auxiliary strut control unit operably connected with the ground mode sensor, takeoff mode sensor, and auxiliary strut. The auxiliary strut control unit is operable to issue a lock-up command signal to the auxiliary strut upon detecting signals from the sensors indicating that the aircraft is on the ground and that the aircraft is operating in a throttled-up mode, whereby the auxiliary strut is caused to lock up during a takeoff roll but is unlocked during other operating modes of the aircraft.

Simulation of Aircraft Landing Gears with a Nonlinear Dynamic Finite Element Code

Abstract: Recent advances in computational speed have made aircraft and spacecraft crash simulations using an explicit, nonlinear, transient-dynamic,e niteelement analysiscodemore feasible.This paperdescribes thedevelopment of a simplelanding-gearmodel, which accurately simulatestheenergy absorbed by thegearwithoutaddingsubstantial complexity to the model. For a crash model the landing gear response is approximated with a spring where the force applied to the fuselage is computed in a user-written subroutine. Helicopter crash simulations using this approach are compared with previously acquired experimental data from a full-scale crash test of a composite helicopter.

Unsteady Simulation of a Landing-Gear Flow Field

Abstract: UNSTEADY SIMULATION OF A LANDING-GEAR FLOW FIELDFei Li lHigh Technology CorporationHampton, VA 23666Mehdi R. Khorrami 2NASA Langley Research CenterHampton, VA 23681Mujeeb R. Malik 3High Technology CorporationHampton, VA23666AbstractThis paper presents results of an unsteady Reynolds-averaged Navier-Stokes simulation of a landing-gearflow field. The geometry of the four-wheel landing-gear assembly consists of several of the fine detailsincluding the oleo-strut, two diagonal struts, a door,yokes/pin and a flat-plate simulating the wing surface.The computational results, obtained by using 13.3million grid points, are presented with an emphasis onthe characteristics of the unsteadiness ensuing fromdifferent parts of the landing-gear assembly, includingvortex shedding patterns and frequencies of dominantoscillations. The results show that the presence of thediagonal struts and the door significantly influence theflow field. Owing to the induced asymmetry, vorticesare shed only from one of the rear wheels and not theother. Present computations also capture streamwisevortices originating from the upstream corners of thedoor.IntroductionDuring the approach and landing phase of anaircraft, the wing leading-edge slats and trailing edgeflaps are fully extended and the landing gears aredeployed. The interaction of the airflow with suchprotrusions in the aircraft structures gives rise tounsteady flow phenomena that are responsible for soundradiation. Because the engines are operated at reducedthrust during landing, airframe noise, especially fromthe landing gear and the high-lift system, constitutes amajor noise source. The envisioned stricter communitynoise regulations are forcing aircraft manufacturers todevise ways to minimize noise radiation from thecurrent and future large transport aircraft. EfficientSenior Scientist, Member AIAA.2 Research Scientist, Computational Modeling andSimulation Branch, Associate Fellow AIAA.3Chief Scientist, Associate Fellow AIAA.noise prediction tools that incorporate the attendantphysics are, therefore, highly desired and needed.One approach towards this end is to numericallysimulate the full complex flow field to provide theunsteady near-field pressure signature required by anacoustic solver based on the Ffowcs Williams-Hawkings formulation (Refs. 1 and 2), which thenyields the acoustic far-field. Although computationallyintensive, direct computation of the unsteady flow fieldprovides an insight into the dominant noise sourceswhich, in turn, can be used for developing reduced ordermodels and in devising means for noise suppression.The combination of an accurate near-field flow solutionwith that of an acoustic propagation formulation hasachieved considerable success in identifying noisesources associated with high-lift systems (e.g.,Khorrami et al., 3-5Singer et al.2'6). The present studyfollows a similar approach and thus, as a first steptowards a comprehensive goal of predicting landing-gear noise, highly resolved time-accurate flowsimulation of a complex landing-gear configuration isattempted.While flow computations of high-lift devices such asflaps and slats received significant attention in the lastdecade, the intricacies of a landing-gear flow field haveremained essentially unknown due to overwhelminggeometrical complexities. The multiple structures thatcollectively generate gear-related noise are nose landinggear, main landing gear (MLG), and wheel wells.Between the nose landing gear and the MLG, noiseassociated with the latter is louder and it is usuallyradiated in all directions. The wheel-well cavitiesproduce high-amplitude tones. However, these tonesoccur at very low frequencies and hence are notconsidered important sources from the standpoint ofcommunity noise. In addition, experiments (Dobrzynski& Heller 7) indicate that the landing gear protrudingfrom the cavity provides a spoiling effect for the cavitytones. In view of these observations, the MLG noiseconstitutes the dominant part of the landing-gear noise.Copyright © 2002 by High Technology Corporation. Publishedby the American Institute of Aeronautics & Astronautics, Inc. with permission.

Aircraft Landing Impact Parametric Study with Emphasis on Nose Gear Landing Conditions

Abstract: A parametric approach to simulation of landing impact, with pitching and heaving degrees of freedom of the aircraft motion, has been used to determine the response of the main and nose gears. Compared to each gear's independent behavior, there are important differences in the landing conditions and in the resulting vertical loads and displacements when these aircraft motions are included. For main gears, the maximum vertical loads are almost linearly dependent on the sinking speed, but there is some variation in the proportion of kinetic energy absorbed. For nose gears, no similar validity exists, compared with the single gear results. Correlation with aircraft sinking speed is absent, but the response is sensitive to the values of initial pitch angle and pitch inertia. This is associated with the equivalent mass and its motion at this location, which are greatly affected by these input quantities and by the aircraft scale.

Integrated aircraft flight dynamics prediction and simulation

Abstract: In a flight simulator program, a flight dynamics editing module enables the user to input parameters for modifying an existing aircraft design or creating an aircraft design. Starting with the type and purpose of aircraft, the user is able to specify parameters defining the configuration, and various other aspects of the aircraft, including the number and type of engines, properties of the flight controls, type of landing gear, etc. Once the user has input the parameters, an aerodynamic coefficients generator module included with the flight simulation program determines aerodynamic coefficients for the aircraft design, using classical formulas and determining the coefficients in an appropriate order. The aerodynamic coefficients and certain parameters input by the user are then output as two flight model data files, in a format usable by the flight simulator program, so that the user can evaluate the aircraft design by flying it within the simulation.

Landing gear warning system

Abstract: The present invention provides for a computer that accepts inputs from a surface monitor to determine whether the terrain below the aircraft is water or land In a preferred embodiment an improved landing gear warning system is provided to warn a pilot when landing gear of an aircraft are in the improper configuration for a landing on a particular surface The warning system comprises a computer operatively connected to a surface monitor and a gear-status warning indicator The computer also accepts an input from the gear status sensors to determine if the landing gear is extended or retracted If the system senses a water surface and the landing gear is down, a warning light and/or buzzer alerts the pilot that the landing gear is in the incorrect configuration If the landing surface is land and the gear is up, the “gear status” indicator warning is initiated

Lighter-than-air aircraft with air cushion landing gear means

Abstract: A lighter-than-air aircraft (1) having a gas-filled hull (2) and a pair of spaced apart landing gear units (11, 12) on the underside of the hull arranged on opposite sides of a longitudinally extending central vertical plane of the hull. Each landing gear unit (11, 12) comprises bag skirt means (5-7, 5'-7'), means for supplying air to and removing air from the bag skirt means and actuating means operable to move the bag skirt means between an operative configuration for containing one or more air cushions and an inoperative configuration.

V/STOL biplane aircraft

Abstract: The present invention is a 2 passenger aircraft capable of vertical and conventional takeoffs and landings, called a jyrodyne. The jyrodyne comprises a central fuselage with biplane-type wings arranged in a negative stagger arrangement, a horizontal ducted fan inlet shroud located at the center of gravity in the top biplane wing, a rotor mounted in the shroud, outrigger wing support landing gear, a forward mounted canard wing and passenger compartment, a multiple vane-type air deflector system for control and stability in VTOL mode, a separate tractor propulsion system for forward flight, and a full-span T-tail. Wingtip extensions on the two main wings extend aft to attach to the T-tail. The powerplants consist of two four cylinder two-stroke reciprocating internal combustion engines. Power from the engines is distributed between the ducted fan and tractor propeller through the use of a drivetrain incorporating two pneumatic clutches, controlled by an automotive style footpedal to the left of the rudder pedals. When depressed, power is transmitted to the ducted fan for vertical lift. When released, power is transmitted to the tractor propeller for forward flight. The aircraft can also takeoff and land in the conventional manner with a much larger payload, and is easily converted to amphibious usage. Landing gear is a bicycle arrangement with outriggers. The aircraft combines twin engines, heavy-duty landing gear, controlled-collapse crashworthy seats with a low stall speed and high resistance to stalls to eliminate any region of the flight regime where an engine or drivetrain failure could cause an uncontrollable crash.

Air, electric and hydraulic landing gear jack

Abstract: A trailer landing gear drive system is disclosed in which pneumatic, hydraulic and electric motors, as well as the traditional hand crank, are easily interchangeable. The landing gear jack mechanism is disposed to easily connect to any one of these drive motors. The system can utilize any one of the three motor combinations without making any change to the jack itself. Each drive motor output shaft is keyed to connect to the input shaft driving the worm gear of the jack. The output shaft of each type of motor is keyed the same so that the motors are swappable with respect to the input shaft of the landing gear. The hand crank shaft is also keyed to be the same as the keyed motor output shafts. Each motor may include a flange to permit it to be secured to the landing gear. The system eliminates the gear reduction box and replaces it with a worm gear. Furthermore, the system can be operated remotely so that the operator need not be exposed to the perils of weather, a shifting load, other vehicles in the vicinity or other similar hazards.

Process for assembly of landing gear on an aircraft structure and aircraft comprising such landing gear

Abstract: A landing gear hinge shaft is installed on an aircraft structure using at least two ball joints ( 22 ), at least one of which is adjustable. The differences between the theoretical and real positions of the centers of the balls are measured, and the adjustments that have to be made to bring the centers of the balls back to their theoretical positions is deduced. This is done by making a first adjustment in the axial direction using a shim ( 30 ) and a second adjustment in the radial direction by adjusting the rotation of an inner cage ( 34 ) and an outer cage ( 36 ) of the ball joint. The inner and outer cages have eccentric axes that facilitate the adjustment.

Influence of landing-gear design on helicopter ground resonance

Abstract: The influence of landing-gear design on a ground-resonance phenomenon is investigated with the aid of finite-element software. Ground resonance is a vibration phenomenon that occurs at certain roto...

Hybrid air vehicle having air cushion landing gear

Abstract: A hybrid air vehicle having a gas-filled contoured flattened hull including a pair of longitudinally extending side lobes defining, on the underside of the hull, a longitudinally extending central recess, a payload module received in the central recess and air cushion landing gear units on the underside of the side lobes of the hull The landing gear units are spaced apart on either side of the payload module The hybrid air vehicle has characteristics of an airplane, a lighter-than-air airship and a hovercraft

Landing gear for aircraft and tire for aircraft

Abstract: PROBLEM TO BE SOLVED: To provide a landing gear for an aircraft capable of reducing abrasion of a tire in landing to improve the life of the tire. SOLUTION: This landing gear for an aircraft is provided with a rotating device 20 (a fin 21, a cover 22) for applying force received from an air current to a wheel 12 to rotate the wheel 12.

Three way displacement test device for aeroplane landing gear landing vibration test

Abstract: The utility model relates to a three way displacement test device for aeroplane landing gear landing vibration test; a four degree of freedom space position test device which consists of a space orientation, a rotary-angle sensor and a support bracket can freely rotate along each direction in a three-dimensional space The front end of the device is provided with magnetic absorption elements The utility model has the advantages that a manipulator of the three way displacement test device can flexibly move in the three-dimensional space; in the moment when an aeroplane landing gear landing, coordinates values of moving track of the front end of the manipulator in the three-dimensional space can be calculated by a computer in a measuring range of the device through the angle change of the rotary-angle sensor, and furthermore, the dynamic changing process of three way impact displacement of aeroplane wheels can be achieved in the aeroplane landing gear landing vibration tests

Assembly and method of exercising an airplane landing gear strut

Abstract: A strut exercise assembly for an aircraft comprises a fluid strut telescopic along a path. A couple selectively connects the fluid strut to a driver. The driver telescopes the fluid strut along a path through the couple.

Passing the test -- the hard way

Abstract: SUBTITLE: 11 OF 12 MAIN LANDING GEAR WHEELS BURST FOLLOWING A340-600 MAXIMUM BRAKE ENERGY EVALUATION.

Some Reasons for Fracture of Load-Bearing Elements of Landing Gears Made of High-Strength Steels in Antonov Airplanes

Abstract: We give the results of tests of some reasons for the unpredicted fracture of force components of a landing gear made of high-strength steels.

Energy absorbing capability of kneeling landing gear for new type armed helicopters during crash process (i): numerical simulation

Abstract: Landing gear is one of the key components of armed helicopters during their design. The dynamic behavior of the landing gear, especially its energy absorbing capability, plays an important role in attenuating the impulsive loading and ensuring the survivability of occupants. This paper firstly introduces the basic design principles of helicopter crashworthiness, and then a typical example of a landing gear associated with a fuselage represented by an effective mass system of the rigid truss undergoing the hard landing impact vertically to the ground with a velocity of 6m/s is studied by using two approaches. One is FEM analysis based on the dynamic model and the other is energy absorbing by the landing gear during the hard landing (crash) process; the change of the kinetic energy of the helicopter and the impact curve of the main attenuation oleo cylinder have been given. Furthermore, a comparison between the results obtained from the two approaches is made. The study can be used as a theoretical instruction for the new type of helicopter crashworthiness design.

Landing gear for plane

Abstract: The utility model relates to an 'airplane overground landing rack' which is a movable safe-landing special-purpose installation arranged on the airport ground and primarily comprises a tyre skid, a guiding chamber, and a buttcover plate. When an alighting carriage of an airplane is out of work, the utility model can be placed at a normal landing position on a runway, the airplane is softly butt-jointed with the buttover plate, and a series of actions like angle presetting, performance of butt joint, parallel cushioning, glide propulsion, centric runway, stop of glide and the like are carried out in sequence to guarantee safe and successful landing. With the utility model, not only the disastrous accidents caused by forcing landing can be prevented, but also forced-landing stand-by facilities can be greatly reduced.

Energy absorbing capability of kneeling landing gear for new type armed helicopters during crash process (ii): theoretical model analysis

Abstract: In the previous paper, the finite element method (FEM) was adopted to analyze the dynamic plastic response and the energy absorbing capability of a landing gear associated with a fuselage represented by an effective mass system of the rigid truss undergoing the hard landing impact vertically to the ground with an initial velocity of 6m/s .The model is based on practical armed helicopters. During the primary design stage, how to simply and effectively estimate the energy absorbing capability of the helicopter structural components and how to establish the corresponding rule of reasonably distributing the impact energy to the components are extremely important. This paper is focused on the simple theoretical model of using the spring mass system based on Lagrange differential equations to approximately estimate the partitioning of the energy absorbing by the landing gear during the hard landing process. The changes of the kinetic energy of the helicopter and the impact curve of the main attenuation oleo cylinder have been given. Finally, a comparison between the results obtained from the FEM technique and present the oretical model is made.

Aircraft tire and rim having blade like windmill to reduce friction, shock or the like between tire and runway when aircraft is landing

Abstract: PROBLEM TO BE SOLVED: To reduce the weight of an aircraft, to lessen the wear of a tire, and to prolong the service life of the tire SOLUTION: Blades of a semi-spherical shape or an adequate shape which are rotated under the wind are fitted to a tire, a rim or both of an aircraft The tire and the rim are fitted to the aircraft, in which wheels are rotated by the effect with the outside air when the aircraft lowers its landing gear, and rotated at considerably high speed when the aircraft is landing to reduce the friction and shocks when the aircraft lands COPYRIGHT: (C)2004,JPO

Gear Walk Instability Studies Using a Vibration Model of a Reduced Scale Landing Gear System

Abstract: Gear walk is a dynamic instability condition that can pose serious harm to an aircraft and its passengers. The instability is believed to be borne as a result of braking, in which vibration of the landing gear can be induced generating motion reminiscent of a walking movement. This paper focuses on the theoretical account of a Reduced Scale Landing Gear (RSLG) apparatus and studies gear walk phenomenon. The mathematical approach involves lumped-parameter model representation of the RSLG that accounts for the landing gear’s struts, the wheels and the caliper-disc brake dynamics. The theoretical treatment of the RSLG apparatus entails consideration of the structure of the device that includes the account of dynamic response of the assembly consisting of a fuselage, two struts and two wheels. Various physical and geometrical parameters are determined and included in the mathematical model of the apparatus. It is demonstrated that the occurrence of gear walk vibration is greatly influenced by the structural stiffness of the system. Both synchronous and 180° out of phase motion of the struts are generated in a parametric study in which structural stiffness is varied.Copyright © 2002 by ASME