Showing papers on "Landing gear published in 2014"

The Landing Gear System Case Study

Abstract: This document presents a landing gear system. It describes the system and provides some of its requirements. We propose this case study as a benchmark for techniques and tools dedicated to the verification of behavioral properties of systems.

UAV docking system and method

Abstract: An aerial vehicle docking system includes a landing pad and an aerial vehicle. The landing pad has a concave landing surface and a depression. The aerial vehicle has landing gear and a protrusion. The protrusion is shaped to mate with the depression. The protrusion and the landing gear are positioned on a bottom surface of the aerial vehicle.

Towards Full Aircraft Airframe Noise Prediction: Lattice Boltzmann Simulations

Abstract: Computational results for an 18%-scale, semi-span Gulfstream aircraft model are presented. Exa Corporation's lattice Boltzmann PowerFLOW(trademark) solver was used to perform time-dependent simulations of the flow field associated with this high-fidelity aircraft model. The simulations were obtained for free-air at a Mach number of 0.2 with the flap deflected at 39 deg (landing configuration). We focused on accurately predicting the prominent noise sources at the flap tips and main landing gear for the two baseline configurations, namely, landing flap setting without and with gear deployed. Capitalizing on the inherently transient nature of the lattice Boltzmann formulation, the complex time-dependent flow features associated with the flap were resolved very accurately and efficiently. To properly simulate the noise sources over a broad frequency range, the tailored grid was very dense near the flap inboard and outboard tips. Extensive comparison of the computed time-averaged and unsteady surface pressures with wind tunnel measurements showed excellent agreement for the global aerodynamic characteristics and the local flow field at the flap inboard and outboard tips and the main landing gear. In particular, the computed fluctuating surface pressure field for the flap agreed well with the measurements in both amplitude and frequency content, indicating that the prominent airframe noise sources at the tips were captured successfully. Gear-flap interaction effects were remarkably well predicted and were shown to affect only the inboard flap tip, altering the steady and unsteady pressure fields in that region. The simulated farfield noise spectra for both baseline configurations, obtained using a Ffowcs-Williams and Hawkings acoustic analogy approach, were shown to be in close agreement with measured values.

Aeroacoustic Evaluation of Flap and Landing Gear Noise Reduction Concepts

Abstract: Aeroacoustic measurements for a semi-span, 18% scale, high-fidelity Gulfstream aircraft model are presented. The model was used as a test bed to conduct detailed studies of flap and main landing gear noise sources and to determine the effectiveness of numerous noise mitigation concepts. Using a traversing microphone array in the flyover direction, an extensive set of acoustic data was obtained in the NASA Langley Research Center 14- by 22-Foot Subsonic Tunnel with the facility in the acoustically treated open-wall (jet) mode. Most of the information was acquired with the model in a landing configuration with the flap deflected 39 deg and the main landing gear alternately installed and removed. Data were obtained at Mach numbers of 0.16, 0.20, and 0.24 over directivity angles between 56 deg and 116 deg, with 90 deg representing the overhead direction. Measured acoustic spectra showed that several of the tested flap noise reduction concepts decrease the sound pressure levels by 2 - 4 dB over the entire frequency range at all directivity angles. Slightly lower levels of noise reduction from the main landing gear were obtained through the simultaneous application of various gear devices. Measured aerodynamic forces indicated that the tested gear/flap noise abatement technologies have a negligible impact on the aerodynamic performance of the aircraft model.

Development of an aircraft wheel actuator for green taxiing

Abstract: In this paper, the design and construction aspects of a wheel actuator to be used for aircraft taxiing on the ground and which will be located in the main landing gear are addressed. The main challenges with the application are the high torque density and fault tolerance requirements. This paper will look at all the different design aspects of the traction motor required for the actuator, including the electro-magnetic design and analysis, thermal management and mechanical analysis. The paper will then conclude with a brief overview of the construction aspects of the motor of the wheel actuator and experimental validation.

Experimental Investigations of the Comet Lander Philae Touchdown Dynamics

Abstract: The comet lander Philae (as part of Europe’s Rosetta mission) is en route to its target, 67/P Churyumov-Gerasimenko. With landing operations coming up at the end of 2014, a partial retesting of the Philae lander’s touchdown system was carried out in spring of 2013. Intensive testing was performed as part of Philae’s design and verification program approximately 10 years ago. However, the new test series specifically addresses touchdown conditions that have been out of capability of the pendulum test facility used at those times. Thus, the follow-up tests focus on touchdown conditions such as asymmetric loads, effects from terrain undulation, and the effect of granular soil mechanics, which could not be studied sufficiently in the original tests. This paper provides insight into the touchdown system of the Philae lander, the characteristics of the used test facility, its weight offloading operating mode, and the specific application to a small-body landing test. The results of the study are presented and d...

On LAGOON Nose Landing Gear CFD/CAA Computation over Unstructured Mesh using a ZDES approach

Abstract: This paper is part of ONERA's effort to compute the noise generation around landing gears, effort that has been shown with studies on a variety of configurations such as the ones included inside the BANC-II (Benchmark problems for Airframe Noise Computations). In this case, the addressed geometry is the LAGOON baseline nose landing gear. On the present computation, a refined unstructured mesh is generated for resolving the boundary layer up to y around one. The simulation of the flow was performed using a Zonal Detached Eddy Simulation (ZDES) model, implemented inside ONERA's code CEDRE. The transient data obtained were used as input for a Ffowcs-Williams and Hawkings computation over the skin of the landing gear and on a porous surface around it, which was performed using ONERA's in-house code KIM. Both the aerodynamic and aeroacoustic results are compared with the experimental ones obtained at F2 and CEPRA19 test campaigns. The comparisons obtained show a good agreement in terms of mean field, wall pressure (mean and spectral content) and aeroacoustic far-field measurements.

Folding rotor-type unmanned aerial vehicle

Abstract: The invention discloses a folding rotor-type unmanned aerial vehicle. The folding rotor-type unmanned aerial vehicle can be folded compactly and unfolded quickly, so that the application flexibility of the rotor-type unmanned aerial vehicle is enhanced effectively. The unmanned aerial vehicle comprises a main body, four rotor arms and a landing gear, wherein each rotor arm is folded and unfolded reliably through a hinge mechanism and a limiting and locking mechanism. When the unmanned aerial vehicle is in a folded state, the rotor arms are positioned in axial grooves in the main body, a torsion spring in the hinge mechanism is compacted, and a limiting and locking piece is positioned at a locked position under the action of a reset spring. When the rotor arms of the unmanned aerial vehicle are required to be unfolded, the limiting and locking piece is driven to slide through a stirring piece along the circumferential direction of the main body, so that the rotor arms are unlocked; the rotor arms are driven to fall quickly by the torsion spring under the effect of torsional force and are limited in a horizontal state. After the rotor arms are unfolded completely, the stirring piece is released, and the limiting and locking piece is returned to the locked position under the effect of the reset spring, so that the rotor arms in an unfolded state are limited and locked.

ABZ 2014: The Landing Gear Case Study

Abstract: This paper describes the modeling, done using the Event-B notation, of the aircraft landing gear case study that is proposed in a special track of the ABZ’2014 Conference. In the course of our development, we discovered some problems in our initial modeling approach. This has led us to propose a second approach and then a third one. Each approach is more efficient than the previous one in terms of proof obligations (roughly speaking: 2000, 1000, 500). All this will be described in this paper. We also try to go beyond this specific case study and give some thoughts about large industrial modeling.

Bifurcation Analysis of a Coupled Nose Landing Gear-Fuselage System

Abstract: Under certain conditions during takeoff and landing, pilots may sometimes experience vibrations in the cockpit. Because the cockpit is located right above the nose landing gear, which is known to potentially be prone to self-excited vibrations at certain velocities, an explanation for those vibrations might be oscillations of the landing gear feeding into the fuselage. However, the fuselage dynamics itself may also influence the dynamics of the landing gear, meaning that the coupling must be considered as bidirectional. A mathematical model is developed to study a coupled nose-landing-gear–fuselage system, which allows to assess the overall influence of the coupling on the system dynamics. Bifurcation analysis reveals that this interaction may be significant in both directions and that the system behavior depends strongly on the modal characteristics of the fuselage.

Noise Scaling and Community Noise Metrics for the Hybrid Wing Body Aircraft

Abstract: An aircraft system noise assessment was performed for the hybrid wing body aircraft concept, known as the N2A-EXTE. This assessment is a result of an effort by NASA to explore a realistic HWB design that has the potential to substantially reduce noise and fuel burn. Under contract to NASA, Boeing designed the aircraft using practical aircraft design princip0les with incorporation of noise technologies projected to be available in the 2020 timeframe. NASA tested 5.8% scale-mode of the design in the NASA Langley 14- by 22-Foot Subsonic Tunnel to provide source noise directivity and installation effects for aircraft engine and airframe configurations. Analysis permitted direct scaling of the model-scale jet, airframe, and engine shielding effect measurements to full-scale. Use of these in combination with ANOPP predictions enabled computations of the cumulative (CUM) noise margins relative to FAA Stage 4 limits. The CUM margins were computed for a baseline N2A-EXTE configuration and for configurations with added noise reduction strategies. The strategies include reduced approach speed, over-the-rotor line and soft-vane fan technologies, vertical tail placement and orientation, and modified landing gear designs with fairings. Combining the inherent HWB engine shielding by the airframe with added noise technologies, the cumulative noise was assessed at 38.7 dB below FAA Stage 4 certification level, just 3.3 dB short of the NASA N+2 goal of 42 dB. This new result shows that the NASA N+2 goal is approachable and that significant reduction in overall aircraft noise is possible through configurations with noise reduction technologies and operational changes.

Design and verification of the landing impact attenuation system for Chang’E-3 lander

Abstract: Landing impact attenuation system is one of the important segments for ChangE-3 lander, which ensures ChangE-3 lander a stable and reliable landing at touchdown, and a successive support for a long run on the lunar surface. In this paper, the primary requirements, chief factors of the system design and final scheme are introduced. Verification aspects, formulation and results of both experiment and simulation are presented. The successful landing indicated that the attenuation system design and test for ChangE-3 lander is rational and reliable. The system met the landing requirements completely.

Modeling a Landing Gear System in Event-B

Abstract: This paper describes the Event-B modeling of the landing gear system of an aircraft whose the complete description can be found in [3]. This real-life case study has been proposed by the ABZ’2014 track that takes place in Toulouse, the European capital of the aeronautic industry. Our modeling is based on the Parnas and Madey’s 4-Variable Model that permits to consider the different parts of a system. These parts are incremently introduced using the Event-B refinement technique. The entire development has been carried out under the Rodin toolset. To validate and prove the different components, we use the Atelier B, SMT and ML provers which are plugged to Rodin.

Numerical continuation analysis of a dual-sidestay main landing gear mechanism

Abstract: A model of a three-dimensional dual-sidestay landing gear mechanism is presented and employed in an investigation of the sensitivity of the downlocking mechanism to attachment point deflections. A motivation for this study is the desire to understand the underlying nonlinear behavior, which may prevent a dual-sidestay landing gear from downlocking under certain conditions. The model formulates the mechanism as a set of steady-state constraint equations. Solutions to these equations are then continued numerically in state and parameter space, providing all state parameter dependencies within the model from a single computation. The capability of this analysis approach is demonstrated with an investigation into the effects of the aft sidestay angle on retraction actuator loads. It was found that the retraction loads are not significantly affected by the sidestay plane angle, but the landing gear’s ability to be retracted fully is impeded at certain sidestay plane angles. This result is attributed to the lan...

Aerodynamic Measurements of a Gulfstream Aircraft Model With and Without Noise Reduction Concepts

Abstract: Steady and unsteady aerodynamic measurements of a high-fidelity, semi-span 18% scale Gulfstream aircraft model are presented. The aerodynamic data were collected concurrently with acoustic measurements as part of a larger aeroacoustic study targeting airframe noise associated with main landing gear/flap components, gear-flap interaction noise, and the viability of related noise mitigation technologies. The aeroacoustic tests were conducted in the NASA Langley Research Center 14- by 22-Foot Subsonic Wind Tunnel with the facility in the acoustically treated open-wall (jet) mode. Most of the measurements were obtained with the model in landing configuration with the flap deflected at 39o and the main landing gear on and off. Data were acquired at Mach numbers of 0.16, 0.20, and 0.24. Global forces (lift and drag) and extensive steady and unsteady surface pressure measurements were obtained. Comparison of the present results with those acquired during a previous test shows a significant reduction in the lift experienced by the model. The underlying cause was traced to the likely presence of a much thicker boundary layer on the tunnel floor, which was acoustically treated for the present test. The steady and unsteady pressure fields on the flap, particularly in the regions of predominant noise sources such as the inboard and outboard tips, remained unaffected. It is shown that the changes in lift and drag coefficients for model configurations fitted with gear/flap noise abatement technologies fall within the repeatability of the baseline configuration. Therefore, the noise abatement technologies evaluated in this experiment have no detrimental impact on the aerodynamic performance of the aircraft model.

Innovative Anti Crash Absorber for a Crashworthy Landing Gear

Abstract: This paper defines an innovative concept to anti-crash absorber in composite material to be integrated on the landing gear as an energy-absorbing device in crash conditions to absorb the impact energy. A composite cylinder tube in carbon fiber material is installed coaxially to the shock absorber cylinder and, in an emergency landing gear condition, collapses in order to enhance the energy absorption performance of the landing system. This mechanism has been developed as an alternative solution to a high-pressure chamber installed on the Agusta A129 CBT helicopter, which can be considered dangerous when the helicopter operates in hard and/or crash landing. The characteristics of the anti-crash device are presented and the structural layout of a crashworthy landing gear adopting the developed additional energy absorbing stage is outlined. Experimental and numerical results relevant to the material characterization and the force peaks evaluation of the system development are reported. The anti-crash prototype was designed, analysed, optimized, made and finally the potential performances of a landing gear with the additional anti-crash absorber system are tested by drop test and then correlated with a similar test without the anti-crash system, showing that appreciable energy absorbing capabilities and efficiencies can be obtained in crash conditions.

Extended physics-based wing mass estimation in early design stages applying automated model generation

Abstract: This article introduces a tool chain for extended physics-based wing mass estimation. Compared to state-of-the-art tool chains, the physics-based structural modelling is extended beyond the wing primary structure. The structural model also includes the movable trailing edge devices including tracks, the spoilers, the engine pylons and the landing gear. The chain consists of the structural analysis model, models for aerodynamic, fuel, landing gear and engine loads as well as a sizing algorithm. To make the complexity of the model generation process feasible for preliminary aircraft design, a knowledge-based approach is chosen. This means that the analysis models are created partly automatically, which leads to a minimum set of required input parameters for the central model generator. The DLR aircraft parametrisation format Common Parametric Aircraft Configuration Scheme is used as central data model for input and output. Therefore, the chain can be easily included in a wider multidisciplinary aircraft design environment.

Modeling an Aircraft Landing System in Event-B

Abstract: This paper presents a stepwise formal development of the landing system of an aircraft. The formal models include the complex behaviour, temporal behaviour and sequence of operations of the landing gear system. The models are formalized in Event-B modeling language, and then the ProB model checker is used to verify the deadlock freedom and to validate the behaviour requirements by animating the formalized models. This case study is considered as a benchmark for techniques and tools dedicated to the verification of behavioural properties of the complex critical systems.

Aircraft autonomous pushback

Abstract: The invention provides methods and systems for controlling speed of an aircraft during an autonomous pushback manoeuvre, i.e. under the aircraft's own power without a pushback tractor. The method includes applying a torque to at least one landing gear wheel of the aircraft, the torque being in a direction opposite to the backwards rolling direction of rotation of the landing gear wheel. The torque applied does not exceed a limit for ensuring aircraft longitudinal stability. For longitudinal stability the torque applied should not cause the aircraft to risk a tip-over event.

Application of Active Suspension System to Reduce Aircraft Vibration using PID Technique and Bees Algorithm

Abstract: dynamic load and vibration caused by landing impact and the unevenness of runway will result in airframe fatigue, discomfort of crew/passengers and the reduction of the pilot's ability to control the aircraft. The aim of the current paper is to design Proportional Integral Derivative classical controller based on Bees Intelligent Algorithm as the optimization technique for nonlinear model of active landing gear system that chooses damping and stiffness performance of suspension system at touchdown as optimization object. Optimal setting of controller parameters to achieve desirable time response using numerical software method based on Bees Algorithm is easier and more effective than other traditional methods because it does not need high experience and complex calculations and leads to better results. This research develops nonlinear two-dimensional mathematical model to describe landing gear system with oleo-pneumatic shock absorber and linear tire. Based on this model, the dynamic equations derived are used to investigate the behavior of an aircraft active landing gear system subject to runway disturbance excitation and the stability conditions of the landing system around static equilibrium position is studied according to the Routh-Hurwitz criterion. Simulink control system simulation software is utilized to validate the theoretical analysis of system stability and results comparison and adaptation of this paper with research of Wang and Xing about investigation of active landing gear system. Results of system numerical Simulation with optimized controller using Bees Algorithm in MATLAB software shows that the transmitted impact load to airframe, the vertical vibration of aircraft and time to return static equilibrium position at touchdown are significantly improved compared with other control performances.

Application of a Flexible Wing Modeling and Physical Mass Estimation System for Early Aircraft Design Stages

Abstract: State-of-the-art models in preliminary wing design apply physics-based methods for primary structures while using empirical correlations for secondary structures. Using those methods, a detailed optimization such as e.g. rear spar positions or flap size is only possible within a limited design space. Novel structural concepts such as multi-spar flap layouts or the introduction of composite materials cannot be analyzed using statistical methods and require extended higher level structural modeling. Therefore, a flexible wing modeling and physical mass estimation system for early aircraft design stages is developed – the WINGmass system. The core of the interdisciplinary tool chain is a central model generator that automatically generates all analysis models from the DLR aircraft data format CPACS (Common Parametric Aircraft Configuration Scheme). For the automatic model generation, a large amount of engineering rules are implemented in the model generator, to reduce the amount of required input parameters and therefore to relieve the aircraft designer. Besides the multi-model generator, the tool chain consist of a structural finite element model (incl. wing primary structures, flaps, flap tracks, ailerons, engine pylon and landing gear), a structural sizing algorithm and loads models for aerodynamic, fuel, landing gear and engine loads. The wing mass estimation system is calibrated against real mass values of the wing primary structures and the trailing edge devices of the Airbus A320 and A340-200. The results of the calibrated tool chain are compared to the masses of the primary structures of the B747-100 and the aluminum baseline version of the MD-90-40X. The calibration factors for composite primary structures are derived from the composite version of the MD-90-40X. Finally, the benefits of the extended physics-based modeling and the application of the WINGmass system in an interdisciplinary aircraft design environment are shown in an aircraft design study. The objective of this study is to compute the optimal wing shape in terms of mission fuel as a function of the take-off field length. Therefore, a parameter variation of the wing and flap geometry is performed, the engine scaled correspondingly and the mission fuel evaluated.

Numerical investigation of a realistic nose landing gear

Abstract: A hybrid approach is used to study the noise generated by a realistic full-scale nose land- ing gear configuration. Compressible Detached-Eddy Simulations are performed to com- pute the flow field ...

High-reliability landing gear control system

Abstract: The invention relates to a high-reliability landing gear control system. The high-reliability landing gear control system comprises a control driving unit and an EMAC driving circuit, wherein the control driving circuit comprises a power supply transformation power distribution module, a 1553B bus interface module, a CPU processing unit, a steering motor driving circuit, a solenoid valve driving circuit and an analog quantity signal processing circuit, wherein the CPU processing unit comprises a taking-up and releasing control module, a front wheel steering control module and an anti-skid braking driving control module; the landing gear control system adopts a driving and control integrated design, the CPU processing unit can be used for achieving combined control on taking up and releasing of a landing gear and a cabin door, the steering of a front wheel, and the anti-skid braking of an electro-mechanical actuator of a main engine wheel, and the system is light in weight, low in power consumption, high in reliability and good in environment adaptation, and can be widely applied to novel spacecraft landing recovery systems and traditional aircraft landing gear systems.

Method for determining aircraft center of gravity independent of measuring the aircraft weight

Abstract: A method which determines aircraft Center of Gravity independent of measuring the aircraft weight. The method is used in monitoring, measuring and computing the Center of Gravity of an aircraft utilizing pressurized, telescopic landing gear struts with axles. Pressure sensors are mounted in relation to each of the landing gear struts to monitor, measure and record aircraft landing gear strut loads by way of pressure. Axle deflection sensors are mounted in relation to each of the landing gear axles to monitor, measure and record aircraft landing gear axle loads by way of deflection. Nose landing gear strut pressure and corresponding values from axle deflection sensors may be adjusted in correlation to the reduced size of the nose landing gear, as compared to the size of the main landing gear, allowing aircraft Center of Gravity to be determined from the combined measured main landing gear pressures in relation to a nose landing gear strut pressure measurements, or combined main landing gear axle deflection sensor in relation to a nose landing gear axle deflection sensor; without any determination of the aircraft weight.

Flow-Field Investigation of Gear-Flap Interaction on a Gulfstream Aircraft Model

Abstract: Off-surface flow measurements of a high-fidelity 18% scale Gulfstream aircraft model in landing configuration with the main landing gear deployed are presented. Particle Image Velocimetry (PIV) and Laser Velocimetry (LV) were used to measure instantaneous velocities in the immediate vicinity of the main landing gear and its wake and near the inboard tip of the flap. These measurements were made during the third entry of a series of tests conducted in the NASA Langley Research Center (LaRC) 14- by 22-Foot Subsonic Tunnel (14 x 22) to obtain a comprehensive set of aeroacoustic measurements consisting of both aerodynamic and acoustic data. The majority of the off-body measurements were obtained at a freestream Mach number of 0.2, angle of attack of 3 degrees, and flap deflection angle of 39 degrees with the landing gear on. A limited amount of data was acquired with the landing gear off. LV was used to measure the velocity field in two planes upstream of the landing gear and to measure two velocity profiles in the landing gear wake. Stereo and 2-D PIV were used to measure the velocity field over a region extending from upstream of the landing gear to downstream of the flap trailing edge. Using a special traverse system installed under the tunnel floor, the velocity field was measured at 92 locations to obtain a comprehensive picture of the pertinent flow features and characteristics. The results clearly show distinct structures in the wake that can be associated with specific components on the landing gear and give insight into how the wake is entrained by the vortex at the inboard tip of the flap.

A bifurcation study to guide the design of a landing gear with a combined uplock/downlock mechanism.

Abstract: This paper discusses the insights that a bifurcation analysis can provide when designing mechanisms. A model, in the form of a set of coupled steady-state equations, can be derived to describe the mechanism. Solutions to this model can be traced through the mechanism's state versus parameter space via numerical continuation, under the simultaneous variation of one or more parameters. With this approach, crucial features in the response surface, such as bifurcation points, can be identified. By numerically continuing these points in the appropriate parameter space, the resulting bifurcation diagram can be used to guide parameter selection and optimization. In this paper, we demonstrate the potential of this technique by considering an aircraft nose landing gear, with a novel locking strategy that uses a combined uplock/downlock mechanism. The landing gear is locked when in the retracted or deployed states. Transitions between these locked states and the unlocked state (where the landing gear is a mechanism) are shown to depend upon the positions of two fold point bifurcations. By performing a two-parameter continuation, the critical points are traced to identify operational boundaries. Following the variation of the fold points through parameter space, a minimum spring stiffness is identified that enables the landing gear to be locked in the retracted state. The bifurcation analysis also shows that the unlocking of a retracted landing gear should use an unlock force measure, rather than a position indicator, to de-couple the effects of the retraction and locking actuators. Overall, the study demonstrates that bifurcation analysis can enhance the understanding of the influence of design choices over a wide operating range where nonlinearity is significant.

Unmanned aerial vehicle/unmanned aircraft system

Abstract: An unmanned aerial vehicle/unmanned aircraft system including an airframe; a plurality of rotor assemblies respectively extending from a plurality of arms connected to said airframe, said rotor assemblies each having a rotor thereon with at least one rotor blade; a landing gear extending from said airframe; and a flight controller disposed on said airframe; wherein said flight controller receives instructions for unmanned aerial vehicle/unmanned aircraft system control.

Model-Checking Real-Time Properties of an Aircraft Landing Gear System Using Fiacre

Abstract: We describe our experience with modeling the landing gear system of an aircraft using the formal specification language Fiacre. Our model takes into account the behavior and timing properties of both the physical parts and the control software of this system. We use this formal model to check safety and real-time properties on the system but also to find a safe bound on the maximal time needed for all gears to be down and locked (assuming the absence of failures). Our approach ultimately relies on the model-checking tool Tina, that provides state-space generation and model-checking algorithms for an extension of Time Petri Nets with data and priorities.