Showing papers on "Landing gear published in 2008"

Preliminary analysis of acoustic measurements from the nasa-gulfstream airframe noise flight test

Abstract: The NASA-Gulfstream joint Airframe Noise Flight Test program was conducted at the NASA Wallops Flight Facility during October, 2006. The primary objective of the AFN flight test was to acquire baseline airframe noise data on a regional jet class of transport in order to determine noise source strengths and distributions for model validation. To accomplish this task, two measuring systems were used: a ground-based microphone array and individual microphones. Acoustic data for a Gulfstream G550 aircraft were acquired over the course of ten days. Over twenty-four test conditions were flown. The test matrix was designed to provide an acoustic characterization of both the full aircraft and individual airframe components and included cruise to landing configurations. Noise sources were isolated by selectively deploying individual components (flaps, main landing gear, nose gear, spoilers, etc.) and altering the airspeed, glide path, and engine settings. The AFN flight test program confirmed that the airframe is a major contributor to the noise from regional jets during landing operations. Sound pressure levels from the individual microphones on the ground revealed the flap system to be the dominant airframe noise source for the G550 aircraft. The corresponding array beamform maps showed that most of the radiated sound from the flaps originates from the side edges. Using velocity to the sixth power and Strouhal scaling of the sound pressure spectra obtained at different speeds failed to collapse the data into a single spectrum. The best data collapse was obtained when the frequencies were left unscaled.

Analysis of Carbon-Dioxide Emissions from Transport Aircraft

Abstract: The problem of allocation of fuel consumption and carbon-dioxide emissions from transport aircraft is presented. An accurate comprehensive program for transport aircraft has been developed. The model includes a geometry deck with 12 subsystems, a separate engine input deck with basic parameters, a database of engine performance from independent simulation, an aerodynamics model for all flight conditions, and an operational deck. Validation of the model is discussed from the point of view of aerodynamics and payload-range performance. The aircraft considered are the Boeing B-737-500, B-747-400, and B-777-300, and the Airbus A340-300. Parametric studies are shown in terms of flight distance, passenger load, baggage allowance, operation with an en route stop, and direct flight. Calculations of best flight range and average passenger load have been considered. Data are presented in matrix form to be used for allocation of carbon dioxide in carbon trading schemes and for the critical evaluation of emissions from civil and commercial operations. It is shown that emissions per passenger per nautical mile range from 0.5 to 1.5 times the reference conditions, which is taken from the design range at full passenger load. It is also shown that fuel and emission savings can be achieved from optimal flight distance.

Method for Vertical Takeoff from and Landing on Inclined Surfaces

Abstract: Takeoff and landing modes are added to a flight control system of a Vertical Take-Off and Landing (VTOL) Unmanned Air Vehicle (UAV). The takeoff and landing modes use data available to the flight control system and the VTOL UAV's existing control surfaces and throttle control. As a result, the VTOL UAV can takeoff from and land on inclined surfaces without the use of landing gear mechanisms designed to level the UAV on the inclined surfaces.

Aircraft landing gear compression rate monitor

Abstract: A system for use in monitoring, measuring, computing and displaying the rate of compression of aircraft landing gear struts experienced while aircraft are executing either normal or hard landing events. A high speed computer attached to high speed cameras, or range-finders, mounted in relation to each of the landing gear struts are used to monitor, measure and record the landing gear compression rates and aircraft touch-down vertical velocities experienced by landing gear struts, as the aircraft landing gear initially comes into contact with the ground. The system also determines through landing gear strut compression rates if aircraft landing limitations have been exceeded.

A Study on Local Flow Variations for Landing Gear Noise Research

Abstract: *This paper discusses a systematic study on the local flows in the vicinity of aircraft landing gears with the objective of understanding the flow features, identifying their effects on landing gear noise generation and prediction and developing simple and efficient models to calculate the local flow velocity for gear noise prediction and analysis. To achieve this objective, local flows for various aircraft types and various operation conditions are extracted from a large CFD database and analyzed to reveal the parametric trends of the local flows as a function of parameters such as the aircraft angle of attack and landing gear location. It is shown that for wing mounted gears, the local flows are strongly affected by the high lift system; the circulation around the high lift wing induces a flow under the wing in opposite direction to the free stream flow, and hence, makes the local flow velocity lower than the free stream velocity, by as much as 25 percent at the gear locations. The local velocities are shown to increase monotonically from their minimum values close to the lower surface of the wing to the free stream velocity as the distance from the wing increases. However, for fuselage mounted gears, the trends are opposite; the local flow velocity for nose gears is usually slightly higher than the free stream and it achieves its maximum close to the lower surface of the fuselage with decreasing amplitude with the distance from the fuselage. This is because the nose gears are located in a flow acceleration region downstream of the stagnation point on the nose cone surface, which is approximately defined here as the minimum velocity point. For all gears, it is shown that the local flow velocity is a decreasing function of the aircraft angle of attack. For wing mounted gears, this is due to the increased lift of the wing at large angles of attack, while for nose gears, increasing angles of attack move the stagnation point downstream towards to nose gears, reducing the velocity at the gear location. Based on these flow features, a simple reduced-order model is developed, which correlates the local flow velocity to the free stream velocity, the aircraft angle of attack, the maximum aircraft takeoff weight and the distance from the aircraft. All these parameters are readily available in practical applications, rendering the simple model suitable for landing gear noise prediction. Some qualitative discussions are given on the effects of the local flow features on landing gear noise analysis and prediction.

Shimmy in a nonlinear model of an aircraft nose landing gear with non-zero rake angle

Abstract: This work concentrates on the lateral oscillations in vehicles, also called shimmy, with a particular emphasis on aircraft. A mathematical model of a nose landing gear is discussed with geometric detail that has been mostly neglected in the past research. Stability criteria for the shimmy-free operation of the landing gear are derived using linear stability analysis. Nonlinear analysis is used not only to study the qualitative behaviour of the Hopf bifurcation but also to analyze the system beyond the Hopf bifurcation. The manuscript concludes with suggestions for future research.

Casing and front landing gear assembly for an aircraft

Abstract: A casing including a wall defining an internal housing which allows retraction of a corresponding landing gear into the interior of the housing. The wall separates the non-pressurized internal housing from a surrounding pressurized zone of the aircraft. The separation wall is a shell which envelops the shape of the landing gear, on the side opposite the opening of the internal housing, and the reinforcement structure includes on one hand longitudinal reinforcement elements extending on both sides of the shell and on the other hand transverse reinforcement elements connecting the longitudinal reinforcement elements. The shell has a first zone of considerable width accommodating the wheels of the landing gear, a second zone of lesser width accommodating the rod of the landing gear, and a third zone running from the second zone of lesser width, becoming wider and accommodating a portion of the mechanism for deployment/retraction of the landing gear.

Aircraft landing gear provided with at least one noise reducing means

Abstract: Disclosed is an landing gear that includes at least One constituent element having an upstream air side and downstream air side relative to airflow across the aircraft landing gear in the down position. The landing gear also includes at least one noise reducing unit including at least one individual net having geometric meshes. The net is positioned at the downstream air side of the constituent element and is arranged at the downstream air side so as to reduce noise generating turbulence generated by airflow across the constituent element in its down position.

Aircraft landing gear monitoring apparatus

Abstract: An apparatus is disclosed for monitoring the load on at least one part of an aircraft landing gear during landing of the aircraft. The apparatus (100) comprises a housing containing a sensor (110, 170) which senses a parameter indicative of the load in the part of the landing gear, a processor (120) which receives signals fromthe sensor and processes the signals to produce data representative of the parameter measured by the sensor, a battery (130) which provides electrical power to the processor, a memory (140) for storing measurement data from the processor, and a wireless transmitter (150, 160) which is controlled by the processor. The wireless transmitter is arranged to transmit at least some of the measurement data from the processor to a remote device (200) located outside of the housing.

Dynamic CFD Simulation of Aircraft Recovery to an Aircraft Carrier

Abstract: perform localized mesh correction to restore the quality of the deformed grid surrounding the aircraft. The unsteady aircraft loads provided by these simulations were compared to the Manned Flight Simulator (MFS) aerodynamic model for the same aircraft configuration and airwake velocity profile. This provided a one-to-one comparison of the aerodynamic model used in the MFS with the CFD F/A-18 aircraft model that includes the coupling effects between the aircraft and ship flowfields. The lift force comparisons show a much more rapid increase in lift for the one-way coupled MFS model as the aircraft crosses the flight deck ramp. This demonstrates the differences in the two models, and highlights the importance of modeling the flowfield coupling physics of aircraft/ship recovery operations in manned-flight-simulation environments. I. Introduction Accurate models for the prediction of the dynamic response of an aircraft to a ship airwake are critical to the development of realistic flight simulation tools for aircraft carrier launch and recovery operations. For this simulation environment, the aircraft model is integrated with a ship airwake flowfield such that the aircraft loads are obtained in the presence of the fluctuating, turbulent airwake. Of particular interest is the coupled interaction between the ship and aircraft flowfield in the vicinity of the deck ramp and touchdown areas, as this point in the landing flightpath produces the highest workload for the pilot. Additionally, the degree of coupling between the aircraft and airwake is highest in this location. Currently, the Manned Flight Simulator (MFS) at NAVAIR Patuxent River, MD incorporates a comprehensive real-time simulation model of the F-18 that is comprised of multiple aircraft aspects including the models of the propulsion system, landing gear, avionics, and aerodynamics. Ship airwake models are integrated with the aircraft model using an array of points distributed on the airframe, typically at the nose, tail, aircraft center of gravity, and wingtips. The aircraft model samples the velocities of a stand-alone airwake flowfield at these points to derive aircraft forces and moments from a look-up table generated from wind tunnel/flight test data. Unsteady, turbulent airwake data generated from computational fluid dynamics (CFD) calculations have been integrated with the MFS F-18 model to provide the fluctuating airwake environment through which the aircraft flies 1 .

Landing gear assembly

Abstract: A landing gear assembly comprises a wheel support housing rotatably connected to a support member, the wheel support housing containing an electrically powered motor operable to adjust the angular position of the wheel support housing relative to the support member.

Development of prototype electro-hydrostatic actuator for landing gear extension and retraction system

Abstract: More Electric Aircraft (MEA) or All Electric Aircraft (AEA) is intensively researched and developed all over the world to reduce total Aircraft power consumption, and thus total operation cost. In MEA or AEA development, Aerospace Research and Technologies activity are focusing the area of Electrical Power system, Flight control, Engine system, Environmental Control System and Landing Gear System.[1] We are focusing the Landing Gear Actuation System and as our 1st step we have developed prototype ELECTRO-HYDROSTATIC ACTUATOR (EHA) for Landing Gear Extension and Retraction System (LGERS) application. The prototype EHA was designed and tested to evaluate the performance, weight and reliability to apply the future Aircraft application. From our prototype model development, we have clarified the technical issues to be improved or considered in the future MEA or AEA application.

Method of reducing the aerodynamic noise generated by an aircraft landing gear

Abstract: The method involves coating structural parts (7, 13) and a lower branch (21) of a landing gear with respective light materials e.g. high density polyurethane foam or elastomer material, for providing an aerodynamic shape to the structural parts and the branch for regulating an air flow around the structural parts and the branch. The density of the materials is less than that of the structural parts and the branch.

Aircraft center of gravity automatic calculating system

Abstract: This invention describes the system and the means for continuous monitoring of center of gravity and total weight of an airplane at rest on the ground. Information from strain gauge transducers located on structural members for the nose wheel and main landing gear is communicated to a computer where calculations are made and data is transmitted to gauges in the airplane cockpit. Range limits for the airplane center of gravity with respect to the center of lift, and also the total airplane weight overload limit are clearly indicated on the respective gauges. This invention makes possible the proper loading of an airplane, which makes for efficient trimming to save fuel. This invention also guarantees proper weight distribution in the airplane consistent with the center of lift and center of gravity limits. This is a huge safety factor for airplane passengers, flight crew, and the public.

Noise Reduction of a Model-Scale Landing Gear Measured in the Virginia Tech Aeroacoustic Wind Tunnel

Abstract: The effectiveness of various fairings for landing gear noise reduction was measured in the Virginia Tech (VT) Stability Wind Tunnel. This wind tunnel was recently upgraded to an aeroacoustic facility, which allowed acoustic measurements to be carried out in the far-field, out of the flow, and in a low reverberant environment. The model was a very faithful replica of the full-scale landing gear, designed to address the issues associated with low-fidelity models. A 63-element microphone phased array was used to locate the noise source components of the landing gear in its baseline and streamlined configurations, and to measure the noise reduction potential of the fairings. Measurements were carried out from two far-field positions on the flyover path of the landing gear. Through a comparison between the noise levels of the landing gear with and without fairing, the noise reduction potential of each fairing could be estimated. The results from these experiments also showed that if phased-array measurements of the landing gear noise are carried out in the near-field, the noise reduction potential of the fairings could be largely overestimated.

Optimizing Low Density Concrete Behavior for Soft Ground Arrestor Systems

Abstract: There are approximately 10 aircraft overruns per year that occur within the United States. Overruns are more common during landing than during takeoff and more likely to occur in wet conditions. Aircraft overruns can result in passenger fatalities, injuries, and extensive aircraft damage. The majority of aircrafts involved in an overrun stop within 305 m (1000-ft.) of the runway threshold. To reduce overrun hazards, the Federal Aviation Administration (FAA) requires airports to have a 305 m (1000 ft) runway safety area beyond the design runway length. However, many airports are restricted from extending their runway because of either natural or man-made barriers. As an alternative to creating a 305 m (1000-ft) runway safety area through runway extension, the FAA allows for the installation of an engineered material arrestor system (EMAS). Arrestor systems are designed as passive systems to reduce aircraft stopping distance by inducing drag forces on aircraft landing gear. An EMAS is typically constructed using a low-density cementitious material. Previous work by the authors has studied the sensitivity of aircraft stopping distance to aircraft characteristics considering two types of arrestor bed materials: phenolic foam and low-density concrete. This article investigates a much larger suite of possible low-density concrete mixes. Three arrestor bed configurations along with twenty-six low-density concrete mixtures were studied to evaluate aircraft stopping distance behavior as a function of low-density concrete mixture. Two aircrafts were considered, B727 and B747. The aircrafts represent different landing gear configurations and weights. Stopping distance was determined for each low-density concrete material considering each aircraft with and without reverse thrust. Over four hundred stopping distance analyses were conducted during the study using the FAA ARRESTOR computer code. In this paper, plots are used to summarize the study results.

Mechanisms for Model Scale Landing Gear Noise Generation

Abstract: th scale to determine the main noise generating features on simplified, four-wheel bogies aligned with the flow. Previous experiments have indicated that changes to wheel shape and model layout can have substantial effects on model noise. In this paper we explain these changes in noise level and present surface oil visualization of the mean flow for different wheel shapes. Acoustic measurements describe the noise generated by major components of the landing gear model and identify sources at the wheel edges, rear axle and oleo/beam junction. The most important noise sources were the result of wake-body interactions and we present changes to the wheel shape, layout of the landing gear and local fairings as successful methods of noise reduction. Results suggest that modest changes in design could yield a much more stable flow over the landing gear, substantially reducing noise generated by all components.

Method of feeding energy to actuators associated with an aircraft undercarriage

Abstract: The invention relates to a method of feeding energy to actuators associated with the undercarriages forming the landing gear of an aircraft, the aircraft comprising: a main power supply that operates independently of rotation of wheels carried by the landing gear; and a local power supply comprising one or more local generators, each driven by rotation of a wheel carried by an undercarriage; the method of the invention comprising the following steps: in a nominal mode of operation, powering said actuators by the local power supply; and in an additional mode of operation, when the delivery of energy by the local power supply is not sufficient, providing additional energy or all of the energy required by said actuators by means of the main power supply.

Aircraft landing gear

Abstract: The invention relates to an aircraft landing gear comprising a landing gear leg, wherein the landing gear leg or one or more parts of the landing gear leg consists partly or completely of a fiber composite material.

Braking-energy equalization system

Abstract: A braking-energy equalization system applied to an aircraft undercarriage, which undercarriage includes at least two sets of landing gear, with each set of landing gear including at least two wheels and with each of wheels being equipped with a brake, wherein the system includes means intended to introduce a delay time to delay the braking of the brakes having a higher braking torque in comparison with the other brakes having a lower braking torque, so as to equalize the braking energies absorbed by the brakes of the landing gear during the landing or during an interrupted takeoff of the aircraft.

Advanced Landing Gears for Improved Impact Absorption

Abstract: The presented project ADLAND (AST3-CT-2004-502793) dealt with evaluating the options for adaptive shock absorbers to be applied in aircraft landing gears. Analytical design procedures were developed to simulate different potential design options and a best practice solution determined. The different hardware components regarding adaptive shock absorbers were then developed and tested with regard to adaptive landing gear model. The objectives of the project were: to develop a concept of adaptive shock-absorbers, to develop new numerical tools for design of adaptive absorbers and for simulation of the adaptive structural response to an impact scenario, to develop technology for actively controlled shock-absorbers applicable in landing gears, to design, produce and perform repetitive impact tests of the adaptive landing gear model with high impact energy dissipation effect, to design, produce and test in flight the chosen full-scale model of the adaptive landing gear.

Method and apparatus for providing power in an aircraft to one or more aircraft systems

Abstract: A method and apparatus is disclosed in which an aircraft system such as the landing gear system or braking system is operated at least partially under power provided by a generator driven by the wheels of the landing gear

Aerodynamically-Assisted Landing Gear

Abstract: Apparatus and methods provide for the use of a lift-producing body with a landing gear assembly in order to provide a lifting force during landing gear operations that reduces the load on the landing gear actuator. According to embodiments, the lift-producing body may be configured for attachment to the landing gear assembly. The lift-producing body may be reconfigured while the landing gear assembly is being retracted or deployed in order to maximize the aerodynamic lift created by the lift-producing body or to minimize the drag induced by the lift-producing body.