Showing papers on "Landing gear published in 1999"

An Overview of Landing Gear Dynamics

Abstract: One of the problems facing the aircraft community is landing gear dynamics, especially shimmy and brake-induced vibration Shimmy and brake-induced vibrations can lead to accidents due to excessive wear and shortened life of gear parts and contribute to pilot and passenger discomfort To increase understanding of these problems, a literature survey was performed The major focus is on work from the last ten years Some older publications are included to understand the longevity of the problem and the background from earlier researchers The literature survey includes analyses, testing, modeling, and simulation of aircraft landing gear; and experimental validation and characterization of shimmy and brake-induced vibration of aircraft landing gear The paper presents an overview of the problem, background information, and a history of landing gear dynamics problems and solutions Based on the survey an assessment and recommendations of the most critically needed enhancements to the state of the art will be presented The status of Langley work contributing to this activity will be given

An Overview of Landing Gear Dynamics

Abstract: One of the problems facing the aircraft community is landing gear dynamics, especially shimmy and brake-induced vibration. Although neither shimmy nor brake-induced vibrations are usually catastrophic, they can lead to accidents due to excessive wear and shortened life of gear parts and contribute to pilot and passenger discomfort. Recently, NASA has initiated an effort to increase the safety of air travel by reducing the number of accidents by a factor of five in ten years. This safety initiative has spurred an increased interest in improving landing gear design to minimize shimmy and brake-induced vibration that are still largely misunderstood phenomena. In order to increase the understanding of these problems, a literature survey was performed. The major focus of the paper is to summarize work documented from the last ten years to highlight the latest efforts in solving these vibration problems. Older publications are included to understand the longevity of the problem and the findings from earlier researchers. The literature survey revealed a variety of analyses, testing, modeling, and simulation of aircraft landing gear. Experimental validation and characterization of shimmy and brake-induced vibration of aircraft landing gear are also reported. This paper presents an overview of the problem documented in the references together with a history of landing gear dynamic problems and solutions. Based on the assessment of this survey, recommendations of the most critically needed enhancements to the state of the art are given.

Modeling and Validation of a Navy A6-Intruder Actively Controlled Landing Gear System

Abstract: Concepts for long-range air travel are characterized by airframe designs with long, slender, relatively flexible fuselages One aspect often overlooked is ground-induced vibration of these aircraft This paper presents an analytical and experimental study of reducing ground-induced aircraft vibration loads by using actively controlled landing gear A facility has been developed to test various active landing gear control concepts and their performance, The facility uses a Navy A6 Intruder landing gear fitted with an auxiliary hydraulic supply electronically controlled by servo valves An analytical model of the gear is presented, including modifications to actuate the gear externally, and test data are used to validate the model The control design is described and closed-loop test and analysis comparisons are presented

Shimmy Vibration Analysis of Aircraft Landing Gears

Abstract: Shimmy vibration is a very important type of motion in the landing gear system during either the takeoff or landing of an aircraft. Energy input for this type of vibration is provided from the kine...

Fuzzy control of aircraft semi-active landing gear system

Abstract: With respect to fatige life of both the landing gear and airframe and passenger comfort the good landing impact and taxi performances are becoming more important due to the increasing in life time and in taxi distancea of aircraft. This paper presents a semi-active landing gear system controlled with fuzzy logic. It ie shown that the aircraft impact and vibration isolation properties aa well e.a the dynamic response of motions can be aigoiflcantly improved. The highly nonlinear aircraft dynamics coupled with varying landing and runway conditions are handled web with the proposed fuzzy controller.

Aircraft fore structure

Abstract: An aircraft fore-structure for wide- and very-wide body freight aircraft that is characterized by the presence of a unpressurized landing gear compartment in the lower fore end section. The landing gear compartment is formed by a ceiling at the top, that is preferably domed, and by a partition towards the rear. A door that is provided in the partition provides access through the landing gear compartment to the pressurized compartment located behind said partition. An opening in the fore of the landing gear compartment also provides access to the radar chamber without requiring the radome to be dismantled. The original layout of the landing gear compartment enables fore landing gear to be installed that is larger than that in existing aircraft.

Centerline landing gear for aerocraft

Abstract: A partially buoyant aircraft capable of transporting very large cargo payloads comprises a lifting body with an exterior airfoil configuration that includes internal structural support members for an exterior skin, the skin defining an internal volume for storing the cargo, propulsion apparatus, flight stabilization apparatus on a portion of the lifting body, lift assisting apparatus carried within the lifting body, and landing gear arranged in close proximity to the longitudinal centerline of the lifting body. Each landing gear comprises a wheel supported by a cylinder set including upper and lower telescoping cylinders, the upper cylinders of the wheels being ported together to operate as a single element.

Directional Stability and Control During Landing Rollout

Abstract: Directional stability in landing rollout of the tricycle landing gear arrangement used in light airplanes is shown in a computer replication of a 1935 demonstration. Stability derivatives of aircraft tires are developed based on rolling tire experimental data. A small perturbation analysis using the tire stability derivatives provides a simplified model of the rollout problem, for better understanding and for checks on complete simulations. Eigenvalues in rollout are found for three cases, a sailplane, a light plane, and a large jet transport. A nonlinear transient analysis is used to verify the small perturbation model, for the sailplane case. Castering wheels are found to make negligible contributions to the eigenvalues. The position of the main gear with respect to the c.g. dominates the problem, aft gears being stable. Large airplanes with noncastering nose wheels appear to be stable in rollout over their ranges of airspeed and relative main gear to nose gear loadings. In transient analysis, banking into the swerve, a nonintuitive strategy for avoiding running off runways in side winds, is shown to be effective for bicycle gears, and in particular, for advanced sailplanes with main wheels ahead of the c.g.

High Speed Civil Transport Aircraft Simulation: Reference-H Cycle 1, MATLAB Implementation

Abstract: The mathematical model and associated code to simulate a high speed civil transport aircraft - the Boeing Reference H configuration - are described. The simulation was constructed in support of advanced control law research. In addition to providing time histories of the dynamic response, the code includes the capabilities for calculating trim solutions and for generating linear models. The simulation relies on the nonlinear, six-degree-of-freedom equations which govern the motion of a rigid aircraft in atmospheric flight. The 1962 Standard Atmosphere Tables are used along with a turbulence model to simulate the Earth atmosphere. The aircraft model has three parts - an aerodynamic model, an engine model, and a mass model. These models use the data from the Boeing Reference H cycle 1 simulation data base. Models for the actuator dynamics, landing gear, and flight control system are not included in this aircraft model. Dynamic responses generated by the nonlinear simulation are presented and compared with results generated from alternate simulations at Boeing Commercial Aircraft Company and NASA Langley Research Center. Also, dynamic responses generated using linear models are presented and compared with dynamic responses generated using the nonlinear simulation.

Semitrailer landing gear

Abstract: A semitrailer landing gear shoe for reducing pits, cracks, marks and depressions in pavements and extending the lives of pavements at truck terminals and delivery sites. In a first aspect of the invention, the average stress of a landing gear on a pavement is reduced by attaching enlarged plates to existing landing gear shoe with pairs of brackets and pairs of threaded fasteners. Concentrated stresses are reduced by bonding a compressible pad to lower surface of the enlarged plate. In a second aspect of the invention, average and concentrated stresses are reduced by replacing an existing landing gear shoe with a shoe having an enlarged lower portion and a compressible pad bonded or otherwise attached to the lower portion. Alternate constructions for the improved landing gear shoe and the compressible pad are disclosed.

Taxiing performance analysis of active control of landing gear

Abstract: A non linear model of active control of the landing gear has been established. According to the state equations and a reasonable objective function, the comprehensive performance of landing gear is optimized. By numerical simulation, the taxiing performance of an active control system landing gear and that of a passive system landing gear are compared.

Aircraft landing gear for underwing use has stiffening actuator to allow flexibility except in deployment phase

Abstract: The landing gear has a stiffening arm (20) between the fixed joint (22) on the leg (50) and a pin (25) which slides in the structure bracket (105,106) and is actuated by a hydraulic actuator to stiffen the leg longitudinally when the actuator (60) deploying the leg is actuated.

Vertical take-off and landing flying vehicle

Abstract: FIELD: aircraft manufacture. SUBSTANCE: flying vehicle includes fuselage with pilot and passenger cabins, landing gear and main landing gear, vertical and horizontal tail units, center-section wing and two wings made in form of pylons on which engine nacelles with engines are mounted; center-section wing has front and rear spars forming port to avoid creation of rarefied turbulent zone. Front spar has form of cylinder running inside fuselage which is used as axle of rotation of center-section wing relative to fuselage which may turn through angle of 90 to 120 deg. Wing is rigidly connected with center-section wing; rear spar is enclosed in fairing. In the lower port of fuselage there is well for retraction of above-mentioned fairing; main landing gear is located in rear section of engine nacelles and they are located in way of flight in aircraft mode of flight. Two versions are proposed: with turboprop and jet engines. EFFECT: reduction of drag; increased speed and flying range. 4 cl, 8 dwg

Unmanned flying vehicle

Abstract: FIELD: aeronautical engineering. SUBSTANCE: unmanned flying vehicle has toroidal fuselage and main rotor consisting of pair of coaxial rotors of opposite rotation creating lifting force necessary for vertical take-off and landing of flying vehicle. According to first version, flying vehicle is provided with external remotely controlled sensing device unit (250) for observation from the Earth surface. This unit may be folded in transportation position. Unit may be used for scanning in horizontal and vertical planes within preset elevation/depression angles. Flying vehicle is provided with foldable landing gear (300) for landing on unprepared areas. Landing gear (300) has several legs secured to toroidal fuselage by means of hinges. Hinges make it possible to stow landing gear in transportation position; each leg is retracted inside fuselage together with hinged pivot. EFFECT: possibility of remote observation. 16 cl, 10 dwg

Aircraft landing gear, equipped with a device for protection of a nearby fuel tank, and aircraft equipped with this landing gear

Abstract: An aircraft landing gear ( 16 ) located in front of a fuel tank is equipped with a protection device ( 22 ) designed to at least partially automatically disconnect the landing gear ( 16 ) from the structure that supports it. For example, the protection device ( 22 ) comprises a part ( 40 ) hinged on the landing gear, and mechanisms ( 42 ) connecting this part to pins ( 38 ) through which the landing gear ( 16 ) is installed on the aircraft. In the case of a bad landing, the landing gear pivots backwards and the part ( 40 ) collides with a reinforcement wall placed on the tank. The part ( 40 ) then pivots about its axis and releases the pins ( 38 ) from their housing. Perforation of the tank is thus prevented.

Development of a composite torque link for helicopter landing gear applications

Abstract: In the framework of a composite landing gear technology programme, a composite torque link for helicopter landing gear applications was developed. The torque link was designed by finite element analysis and optimised for minimal weight. The torque link was fabricated by Resin Transfer Moulding (RTM) for which a tooling concept was developed. Static tests demonstrated the load carrying capabilities in undamaged and damaged condition of the torque link since all specimens failed beyond their Design Ultimate Load level.

Taxiing, Take-Off, and Landing Simulation of the High Speed Civil Transport Aircraft

Abstract: The aircraft industry jointly with NASA is studying enabling technologies for higher speed, longer range aircraft configurations. Higher speeds, higher temperatures, and aerodynamics are driving these newer aircraft configurations towards long, slender, flexible fuselages. Aircraft response during ground operations, although often overlooked, is a concern due to the increased fuselage flexibility. This paper discusses modeling and simulation of the High Speed Civil Transport aircraft during taxiing, take-off, and landing. Finite element models of the airframe for various configurations are used and combined with nonlinear landing gear models to provide a simulation tool to study responses to different ground input conditions. A commercial computer simulation program is used to numerically integrate the equations of motion and to compute estimates of the responses using an existing runway profile. Results show aircraft responses exceeding safe acceptable human response levels.

Multi-functional convertible transport facility

Abstract: FIELD: heavy-than-air flying vehicles used as ground (water) transport. SUBSTANCE: transport facility has wing panels foldable inside casing, landing gear with drive and steerable wheels, air propeller and tail unit. Wheels and propeller are driven from plant. Center of gravity of CONVERTIBLE transport facility is located simultaneously in zone of flight CG positions and in zone of coupling characteristics and stability in position on landing gear. At take-off, pilot increases wing angle, thus ensuring lift-off of vehicle. On water surface, use is made of extensible hydrofoils. EFFECT: ease of conversions; enhanced efficiency both on ground and in air. 4 cl, 2 dwg

Cell-combined large size sea surface vehicle and airplane takeoff/landing platform

Abstract: A large size sea surface vehicle is combined by a large number of cells that are distributed along two horizontal dimensions on sea surface. Connections of the cells are elastic and flexible to prevent destructive stress. Its power system comprises a large number of engines controlled by computers that are organized in an Internet-like computer network. The sea surface vehicle is unlimitedly scalable, practically unsinkable and exceptionally mobile and its draught is very shallow. Without changing itself, the sea surface vehicle can function as the bases of an aircraft carrier, a mobile sea surface airport, a heavy weapon group transport/landing ship, a comprehensive sea battle platform and a solar energy collection platform. An airplane takeoff/landing platform is made for airplanes to take off and land on it. The airplane takeoff/landing platform comprises a carrying board on which an airplane carries out takeoff and landing, a moving system on which the carrying board moves forward and backward, a thrusting system by which the carrying board is accelerated and a braking system by which the carrying board is decelerated. The airplane takeoff/landing platform provides a new approach of airplane's takeoff and landing. It significantly increases an airplane's survival probability when the airplane's landing gear does not work. It can actually function as a mobile airfield itself.

Skid type landing gear

Abstract: PROBLEM TO BE SOLVED: To provide a skid type landing gear which can eliminate inferiority that in a cross tube directly determining rigidity of the skid type landing gear of a helicopter, high strength required at hard landing time and low rigidity for avoiding ground resonance are simultaneously required, manufacture is difficult, and rigidity adjustment at completion time is difficult. SOLUTION: This device is provided with a connection member 15, 16, in which a cross tube 3 arranged in a direction orthogonal to a roll axis direction to be arranged in a bottom part of an airframe so as to lower down both end parts toward the outward, making a mounting part in the airframe able to turn, is formed so as to engage with an airframe bottom part, and a plurality of contact parts 18, in which by deflection of the cross tube 3 when landing is performed by rapid sinking, without through the connection member 15, 16, in the airframe bottom part, a peripheral surface of the cross tube 3 is brought into direct contact, so as to directly transmit a load generated when a skid tube 6 is landed to the airframe bottom part.

Actively Controlled Landing Gear for Aircraft Vibration Reduction

Abstract: Concepts for long-range air travel are characterized by airframe designs with long, slender, relatively flexible fuselages. One aspect often overlooked is ground induced vibration of these aircraft. This paper presents an analytical and experimental study of reducing ground-induced aircraft vibration loads using actively controlled landing gears. A facility has been developed to test various active landing gear control concepts and their performance. The facility uses a NAVY A6-intruder landing gear fitted with an auxiliary hydraulic supply electronically controlled by servo valves. An analytical model of the gear is presented including modifications to actuate the gear externally and test data is used to validate the model. The control design is described and closed-loop test and analysis comparisons are presented.

Airbus airframe noise reduction—A European harmonized research effort

Abstract: Very large aircraft—such as the planned Airbus A3XX—require correspondingly high lift forces and extended landing gear structures, thus causing potentially very high airframe noise levels during the landing approach. This problem was realized by the Airbus Consortium, and the first relevant research initiatives date back to the early 1990s. Soon after, initial research at DLR began under contract to Airbus Industrie, dedicated to landing gear airframe noise. Recognizing the general challenge of research for aircraft noise reduction at that time, a European Noise Reduction Initiative (ENRI) was proposed, dealing with both engine and airframe noise. Subsequent technical discussions, however, led to separate programs for engine and airframe noise research, the latter being initiated under the acronym RAIN (reduction of airframe and installation noise). RAIN encompasses analytical and experimental work to describe, predict, and reduce the noise both from landing gears and high lift devices. In parallel, national research programs began: In France wind tunnel and flyover experiments relate to the whole aircraft airframe noise characteristics, while corresponding research in Germany focuses on high lift devices noise. In Great Britain, noise modeling is performed for landing gear noise prediction. These national efforts are coordinated by the Airbus partner companies (3E‐program).

Using Simulation to Optimize Ski Jump Ramp Profiles for STOVL Aircraft

Abstract: : Ramps have been used for many years aboard the Navy ships of many Countries to reduce takeoff run distance and wind-over-deck (WOD) requirements, as well as to increase the aircraft takeoff gross weight capability over that of a flat deck carrier. Under the Joint Strike Fighter program, an effort has been funded to evaluate various ramp profiles and ramp performance Optimization methodologies. Results of these evaluations will be used with an advanced STOVL aircraft to provide the maximum benefit to takeoff performance, while not becoming a design driver for landing gear of adversely affecting ship designs.

Method and apparatus for removing an aircraft strut from an aircraft having retractable landing gear

Abstract: An apparatus for removing struts from pivoting landing gear supports of a plane having retractable landing gear includes a stiffening anchor attached to a distal end of the strut wherein the distal end is the end at which the wheel is attached. The apparatus further includes a press collar that slidingly contains the strut within it. In between the press collar and the stiffening anchor is a hydraulic ram that provides up to twenty thousand pounds of urging pressure. The urging pressure provided by the hydraulic ram is axially translated into the aircraft pivoting landing gear support and into the landing gear strut in an opposite axial direction to remove the strut. The stiffening anchor is formed to fit the strut and to distribute the urging pressure in a way that does not damage the strut. A method of removing a strut seized to a pivotal landing gear support of a plane having retractable landing gear includes placing the hydraulic strut removing tool against the strut, securing it to the strut, and applying hydraulic pressure until the strut is urged free.