Showing papers on "Landing gear published in 2016"

Autonomous system for unmanned aerial vehicle landing, charging and takeoff

Abstract: An unmanned aerial vehicle (UAV) can automatically guide itself to the vicinity of a charging station of an automated landing, charging and takeoff system, which then assists with the close-range laser guidance of the UAV in order for it to dock, without the need for landing gear. The dock has locating valleys that help the booms of the UAV to self-align under the force of gravity. Electrical connections are automatically made for data download and charging. A cover may be closed over the UAV during charging.

Prediction of Landing Gear Loads Using Machine Learning Techniques

Abstract: This article investigates the feasibility of using machine learning algorithms to predict the loads experienced by a landing gear during landing. For this purpose, the results on drop test data and...

Rotorcraft Hard Landing Mitigation Using Robotic Landing Gear

Abstract: A unique, beneficial feature of rotorcraft is their flexibility in aircraft-to-ground interfacing. For a variety of reasons, hard landings can occur when the descent rate of the aircraft is larger than intended. The resulting impact can result in vehicle damage, structural failure, injuries, etc. To reduce these risks, an attractive solution is the implementation of a robotic legged landing gear (RLLG) system. The system softens a hard landing by acting as a shock absorber with a relatively large stroke, allowing the aircraft to decelerate over a much larger distance compared with a tradition landing gear system. This paper explores the mitigation of rotorcraft hard landings via RLLG through a comprehensive multibody dynamics simulation tool. The purpose of this study is to demonstrate the efficacy of the RLLG as a robust solution to reduce loads during hard landings for multiple landing configurations. The results show that when using RLLG in place of conventional landing gear, peak loads are reduced by approximately 70–90%, depending on the landing conditions. Through Monte Carlo simulation, robotic landing gear system performance is shown to be robust to uncertain conditions. [DOI: 10.1115/1.4032286]

Landing of a fixed-wing UAV on a mobile ground vehicle

Abstract: The development of solar-powered high-altitude UAV has gained increasing attention in the recent years. Several aircraft have had successful flights in the stratosphere, but despite advances in lightweight design they can only carry small payloads compared to the total takeoff mass. This paper suggests to eliminate the need for a landing gear by landing on a mobile ground vehicle. This would not only increase the payload capacity, but also simplify landings in crosswind conditions and thus increase the operational availability. A system with a small UAV and a car-mounted landing platform is prepared as a technology demonstrator. Different aspects of the landing problem are studied in simulations and real experiments and algorithms for the cooperative control of both vehicles are proposed. Simulations as well as experiments with the real car and a simulated UAV show the feasibility of such landings.

Analysis of landing gear noise during approach

Abstract: Airframe noise is becoming increasingly important during approach, even reaching higher noise levels than the engines in some cases. More people are affected due to low flight altitudes and fixed traffic routing associated with typical approaches. Formost air- craft types, the landing gear system is a dominant airframe noise source. However, this element can only be modeled in an approximate manner in wind tunnel experiments. In this research, flyovers of landing aircraft were recorded using a 32 microphone array. Fun ctional beamforming was applied to analyze the noise emissions from the landing gear system. lt was confirmed that for some aircraft types, such as the Airbus A320 and the Fokker 70, the nose landing gear is a dominant noise source du ring approach. The correlation between the noise levels generated by the landing gear and the aircraft velocity was found to be significant, explai ning about 70% of the varia bility found in the noise levels, which is in good agreement with all known theory. Moreover, the experimental resu lts for the Airbus A320 measurements were compared with those obtained using the DLR system noise prediction tool PANAM. Whereas the total aircraft noise levels were in good agreement. the measurements indicate a higher contribution from the nose landing gear noise compared to the predictions.

Nonlinear modeling of adaptive magnetorheological landing gear dampers under impact conditions

Abstract: Adaptive landing gear dampers that can continuously adjust their stroking load in response to various operating conditions have been investigated for improving the landing performance of a lightweight helicopter. In prior work, adaptive magnetorheological (MR) landing gear dampers that maintained a constant peak stroking force of 4000 lbf across sink rates ranging from 6 to 12 ft s−1 were designed, fabricated and successfully tested. In this follow-on effort, it is desired to expand the high end of the sink rate range to hold the peak stroking load constant for sink rates ranging from 6 to 26 ft s−1, thus extending the high end of the speed range from 12 (in the first study) to 26 ft s−1. To achieve this increase, a spring-based relief valve MR landing gear damper was developed. In order to better understand the MR landing gear damper behavior, a modified nonlinear Bingham Plastic model was formulated, and it incorporates Darcy friction, viscous forces across the MR and relief valves to better account for the damper force behavior at higher speeds. In addition, gas pressure inside the MR damper piston is considered so the total damper force includes a gas force. The MR landing gear damper performance is characterized using drop tests, and the experiments are used to validate model predictions data at low and high nominal impact speeds up to 26 ft s−1 (shaft velocity of 9.6 ft s−1).

Aircraft wing structural design optimization based on automated finite element modelling and ground structure approach

Abstract: An optimization procedure combining an automated finite element modelling (AFEM) technique with a ground structure approach (GSA) is proposed for structural layout and sizing design of aircraft wings. The AFEM technique, based on CATIA VBA scripting and PCL programming, is used to generate models automatically considering the arrangement of inner systems. GSA is used for local structural topology optimization. The design procedure is applied to a high-aspect-ratio wing. The arrangement of the integral fuel tank, landing gear and control surfaces is considered. For the landing gear region, a non-conventional initial structural layout is adopted. The positions of components, the number of ribs and local topology in the wing box and landing gear region are optimized to obtain a minimum structural weight. Constraints include tank volume, strength, buckling and aeroelastic parameters. The results show that the combined approach leads to a greater weight saving, i.e. 26.5%, compared with three additional optimi...

Simulation-Based Airframe Noise Prediction of a Full-Scale, Full Aircraft

Abstract: A previously validated computational approach applied to an 18%-scale, semi-span Gulfstream aircraft model was extended to the full-scale, full-span aircraft in the present investigation. The full-scale flap and main landing gear geometries used in the simulations are nearly identical to those flown on the actual aircraft. The lattice Boltzmann solver PowerFLOW® was used to perform time-accurate predictions of the flow field associated with this aircraft. The simulations were performed at a Mach number of 0.2 with the flap deflected 39 deg. and main landing gear deployed (landing configuration). Special attention was paid to the accurate prediction of major sources of flap tip and main landing gear noise. Computed farfield noise spectra for three selected baseline configurations (flap deflected 39 deg. with and without main gear extended, and flap deflected 0 deg. with gear deployed) are presented. The flap brackets are shown to be important contributors to the farfield noise spectra in the mid- to high-frequency range. Simulated farfield noise spectra for the baseline configurations, obtained using a Ffowcs Williams and Hawkings acoustic analogy approach, were found to be in close agreement with acoustic measurements acquired during the 2006 NASA-Gulfstream joint flight test of the same aircraft.

Attitude Stabilization for Lunar and Planetary Lander with Variable Damper

Abstract: This paper describes an attitude control method that has been designed to prevent the overturning of lunar and planetary landers, based on a variable-damping shock absorber for the landing gear. Conventionally, the landing gear of lunar and planetary landers has a fixed shock attenuation parameter that is not used proactively for attitude control of the lander during the touchdown sequence. The new method enables the suppression of any disturbance to the attitude of the lander by adjusting the damping coefficient of each landing leg independently, based on the angular velocity vector and displacement velocity of each leg of the lander. The results of a numerical simulation indicate that the control rule for a three-dimensional system is effective for preventing the overturning of the lander on inclined terrain. The results of the simulation and experiments show that the landing gear with the actively variable damping and the control rule play a major role in preventing the overturning of a lunar or planet...

Landing Gear Noise Prediction and Analysis for Tube-and-Wing and Hybrid-Wing-Body Aircraft

Abstract: Improvements and extensions to landing gear noise prediction methods are developed. New features include installation effects such as reflection from the aircraft, gear truck angle effect, local flow calculation at the landing gear locations, gear size effect, and directivity for various gear designs. These new features have not only significantly improved the accuracy and robustness of the prediction tools, but also have enabled applications to unconventional aircraft designs and installations. Systematic validations of the improved prediction capability are then presented, including parametric validations in functional trends as well as validations in absolute amplitudes, covering a wide variety of landing gear designs, sizes, and testing conditions. The new method is then applied to selected concept aircraft configurations in the portfolio of the NASA Environmentally Responsible Aviation Project envisioned for the timeframe of 2025. The landing gear noise levels are on the order of 2 to 4 dB higher than previously reported predictions due to increased fidelity in accounting for installation effects and gear design details. With the new method, it is now possible to reveal and assess the unique noise characteristics of landing gear systems for each type of aircraft. To address the inevitable uncertainties in predictions of landing gear noise models for future aircraft, an uncertainty analysis is given, using the method of Monte Carlo simulation. The standard deviation of the uncertainty in predicting the absolute level of landing gear noise is quantified and determined to be 1.4 EPNL dB.

Reliability Analysis of Landing Gear Retraction System Influenced by Multifactors

Abstract: The landing gear retraction system of an aircraft, including mechanical and hydraulic systems, is complex and nonlinear. It has many uncertain factors, which lead to difficulty in reliability analysis. To make the reliability analysis more accurate and efficient, some studies are represented in this paper. Taking the main landing gear of an aircraft as a research object, the dynamic equations of the retraction system were derived. The simulation model was built, combining the mechanism dynamics with the hydraulic system, and its accuracy was verified by laboratory test results. Based on this model, the paper shows how the key parameters, including the crosswind velocity, the diameter of the damping orifice, liquid capacity, friction, and oil leak, affect the performance of the landing gear retraction. After that, the limit state equation of the retraction system’s reliability was set up. For the implicit limit state equation, the response surface model of retraction reliability was established with a quad...

Biomimetic Design for Unmanned Aerial Vehicle Safe Landing in Hazardous Terrain

Abstract: Unmanned aerial vehicles capable of hazardous terrain landing are desirable for intelligence collection. A crucial point is the landing gear's autonomous adaptation to the rough surface, which is especially difficult in an unknown and constrained environment. To enable this capability, this paper proposes a novel biomimetic system that ascertains terrain appearances like large obstacles and precipitous slope using a monocular camera and adjusts the mechatronics landing structure according to the terrain. A dynamic model including the ground effect is provided and a time-to-contact theory-based backstepping nonlinear controller is designed to reject uncertainty disturbances as well as implement a bio-inspired guidance strategy for soft landing in hazardous terrain. The mechatronic architecture and cascade control structure using custom-built unmanned air vehicle platform are presented. Experimental results and video footage demonstrate this biomimetic approach efficiently controls a vehicle successfully landing in an unknown and unstructured constrained environment.

Computational Evaluation of Airframe Noise Reduction Concepts at Full Scale

Abstract: High-fidelity simulations focused on full-scale evaluation of new technologies for mitigating flap and landing gear noise are presented. These noise reduction concepts were selected because of their superior acoustic performance, as demonstrated during NASA wind tunnel tests of an 18%-scale, semi-span model of a Gulfstream aircraft. The full-scale, full-aircraft, time-accurate simulations were performed with the lattice Boltzmann PowerFLOW(Registered Trademark) solver for free air at a Mach number of 0.2. Three aircraft configurations (flaps deflected at 39 without and with main gear deployed, and 0 flaps with main gear extended) were used to determine the aero-acoustic performance of the concepts on component-level (individually) and system-level (concurrent applica-tion) bases. Farfield noise spectra were obtained using a Ffowcs-Williams and Hawkings acoustic analogy approach. Comparison of the predicted spectra without (baseline) and with the noise treatments applied showed that noise reduction benefits between 2-3 dB for the flap and 1.3-1.7 dB for the main landing gear are obtained. It was also found that the full extent of the benefits is being masked by the noise generated from the flap brackets and main gear cavities, which act as prominent secondary sources.

A method and a device for marking the ground for an aircraft in flight, and an aircraft including the device

Abstract: A method of marking a landing zone on ground for an aircraft in flight. The aircraft projects on the ground a light shape referred to as a “projected light shape” comprising at least one line of light defining a geometrical surface, the aircraft tending to place at least a portion of landing gear of the aircraft on the geometrical surface, the projected light shape being identical regardless of the position of the projector in air space.

Mathematical model and vibration analysis of aircraft with active landing gear system using linear quadratic regulator technique

Abstract: This paper deals with the study and comparison of passive and active landing gear system of the aircraft and dynamic responses due to runway irregularities while the aircraft is taxying. The dynamic load and vibration caused by the unevenness of runway will result in airframe fatigue, discomfort of passengers and the reduction of the pilot’s ability to control the aircraft. One of the objectives of this paper are to obtain a mathematical model for the passive and active landing gears for full aircraft model. The main porpuse of current paper is to design Linear Quadratic Regulator (LQR) for active landing gear system that chooses damping and stiffness performance of suspension system as control object. Sometimes conventional feedback controller may not perform well because of the variation in process dynamics due to nonlinear actuator in active control system, change in environmental conditions and variation in the character of the disturbances. To overcome the above problem, this research designs a controller for a second order system based on Linear Quadratic Regulator. The performance of active system is compared with the passive landing gear system by numerical simulation. The results of current paper in compared with the previous work mentioned in reference, demonstrate 37.04% improvement in body acceleration, 20% in fuselage displacement and 13.8% in the shock strut travel. The active landing gear system is able to increase the ride comfort and good track holding by reducing the fuselage acceleration and displacement and load induced to airframe caused by runway excitation.

Rosetta Lander: On-Comet Operations Execution and Recovery after the Unexpected Landing

Abstract: Philae’s landing on comet 67P/Churyumov–Gerasimenko on 12 November 2014 was one of the main milestones of the European Rosetta mission. The nature of Philae’s mission, to land, operate and survive on comet 67P, required a high degree in autonomy of the on-board software and of the operations scheduling and execution concept. Philae’s baseline operations timeline consisted of predefined and validated blocks of instrument deployments and scientific measurements. These were supported by subsystem activities such as rotation and lifting of the main body relative to the landing gear to allow for specific instrument deployment or in order to cope with the unknown attitude after landing. The nominal descent was followed by an unforeseen rebound at touchdown, lifting Philae again from the comet surface to enter a two-hour phase of uncontrolled flight over the comet surface. Philae’s unknown final landing site, unfavorable attitude with respect to the local surface, bad illumination and lack of anchoring required a complete rescheduling of the baseline timeline. The autonomy offered by the system and the predefined contingency operations were exploited by the operations team to maximize output despite this undesirable state. Implementation of the rescheduling to allow a maximum scientific output, despite the limitations due to unknown communication windows, unknown orientation with respect to the comet surface, the associated risks of any mechanisms activation, the lack of sufficient solar power and limited battery lifetime, is described and elaborated.

Potential for Landing Gear Noise Reduction on Advanced Aircraft Configurations

Abstract: The potential of significantly reducing aircraft landing gear noise is explored for aircraft configurations with engines installed above the wings or the fuselage. An innovative concept is studied that does not alter the main gear assembly itself but does shorten the main strut and integrates the gear in pods whose interior surfaces are treated with acoustic liner. The concept is meant to achieve maximum noise reduction so that main landing gears can be eliminated as a major source of airframe noise. By applying this concept to an aircraft configuration with 2025 entry-into-service technology levels, it is shown that compared to noise levels of current technology, the main gear noise can be reduced by 10 EPNL dB, bringing the main gear noise close to a floor established by other components such as the nose gear. The assessment of the noise reduction potential accounts for design features for the advanced aircraft configuration and includes the effects of local flow velocity in and around the pods, gear noise reflection from the airframe, and reflection and attenuation from acoustic liner treatment on pod surfaces and doors. A technical roadmap for maturing this concept is discussed, and the possible drag increase at cruise due to the addition of the pods is identified as a challenge, which needs to be quantified and minimized possibly with the combination of detailed design and application of drag reduction technologies.

Charging landing gear, unmanned aerial vehicle, charging platform and unmanned aerial vehicle cruising and charging system

Abstract: The invention discloses a charging landing gear suitable for an unmanned aerial vehicle. A cross rod of the charging landing gear is provided with a plurality of charging contact parts, wherein a charging circuit module is also arranged in the cross rod; and adapting of a charging interface of the unmanned aerial vehicle can be directly finished through the landing gear. The invention discloses a landing gear-based unmanned aerial vehicle. The unmanned aerial vehicle can be electrically connected directly through the landing gear when charged; the unmanned aerial vehicle stops on a charging platform of the matched with the landing gear when needing to be charged; and the unmanned aerial vehicle can be charged through the charging platform. The invention further discloses the charging platform matched with the landing gear. Through the design which is simple in structure and low in cost, good contact of the charging contact parts is ensured. The invention further provides an unmanned aerial vehicle cruising and charging system based on the unmanned aerial vehicle and the charging platform. The charging platform can be searched for the unmanned aerial vehicle through a cloud management server; and a flight path is set for the unmanned aerial vehicle.

Bifurcation study of a dynamic model of a landing gear mechanism

Abstract: This paper presents a new modeling approach for the analysis of landing-gear mechanisms. By replacing the mechanism’s rotational joints with equivalent high-stiffness elastic joints, numerical-continuation methods can be applied directly to dynamic models of landing-gear mechanisms. The effects of using elastic joints are considered through two applications: an overcenter mechanism and a nose-landing-gear mechanism. In both cases, selecting a sufficient stiffness for the elastic joint is shown to provide accurate continuation results. The advantages of this new modeling approach are then demonstrated by considering the unlocking of a nose landing gear with a single uplock/downlock mechanism, when subjected to different orientations and magnitudes of gravitational loading. The unlocking process is shown to be qualitatively insensitive to changes in both load angle and load magnitude, ratifying the robustness of a previously proposed control methodology for unlocking a nose landing gear with a single uplock...

Landing gear test loading device

Abstract: The invention provides a landing gear test loading device which comprises a main load bearing mechanism frame (1). A plurality of upright columns are spliced to form the main load bearing mechanism frame (1), and the main load bearing mechanism frame (1) is fixed onto the ground; a lifting platform (2) is connected into the main load bearing mechanism frame (1) by guide rails (13) and is parallel to the ground, a lifting motor system (3) for driving the lifting platform (2) to move is mounted on the side, which is far away from the ground, of the lifting platform (2); a landing gear (4) is fixed to the side, which is close to the ground, of the lifting platform (2) by the aid of a landing gear fixing supporting device, a false wheel (6) is mounted on the other side of the landing gear (4) and is connected with a load loading system fixed onto the main load bearing mechanism frame (1), and the load loading system is used for applying load to the false wheel (6). The landing gear test loading device has the advantages that the landing gear test loading device is used for controlling change of stroke of a shock absorber in the landing gear, loading points and airplane wheels are relatively fixedly positioned, and the load can be loaded in a variable-stroke manner without manual intervention.

Take-Off and Landing Using Ground-Based Power-Simulation of Critical Landing Load Cases Using Multibody Dynamics

Abstract: A novel take-off and landing system using ground-based power is proposed in the EU-FP7 project GABRIEL. The main feature of this system is the complete removal of the landing gear from civil aircraft. The proposed system has the potential to reduce aircraft weight, emissions, and noise. A feasibility study of the structural design of the connection mechanism between aircraft and ground system has been performed by simulating the landing procedure on a moving ground system. One of the key challenges is the landing on a moving ground system under high crosswind conditions. The main focus in the current research is the calculation of the critical dynamic loads on both aircraft and ground system for a wide range of landing conditions (sink rate, velocity differences between aircraft and ground system, etc.). For comparison, conventional landing procedures with a traditional landing (TL) gear have also been simulated. The aerodynamics of the aircraft is represented by an accurate empirical model. The r...

Unsteady Aero-Loads from Vortices Shed on A320 Landing Gear Door: CFD compared to flight tests

Abstract: AFLoNext is a project of four years duration, funded by the European Commission within the Seventh Framework Programme. The project’s main objectives are proving and maturing highly promising flow ...

Tilt-rotor fixed wing aircraft with vertical take-off and landing function

Abstract: The invention relates to a tilt-rotor fixed wing aircraft with a vertical take-off and landing function. The tilt-rotor fixed wing aircraft comprises an aircraft body, wings and a tail, wherein the wings and the tail are mounted on the aircraft body. Pitching and tilting power devices are arranged on the left side and the right side of the aircraft body. A front landing gear and a main landing gear are arranged at the bottom of the aircraft body. An equipment hatch is arranged on the upper portion of the aircraft body, and an aviation telemetering camera is arranged in an equipment cabin. A control cabin hatch is arranged on the upper portion of the aircraft body, and a control device is arranged in a control cabin. A reverse-torsional balance power device is arranged on the rear portion of the aircraft body. The wings are mounted on the two sides of the aircraft body and provided with wing control planes. The tail is connected with the aircraft body through tail supporting rods and comprises a horizontal tail, a pitching control plane, a vertical tail and a yaw control plane. The tilt-rotor fixed wing aircraft has the advantages that the vertical take-off and landing, tilting and level flight of the aircraft can be achieved through one power system, take-off and landing of an unmanned aerial vehicle are not limited by fields, the structural weight can be better reduced, the aircraft can fly more stably, the flying time is longer, operation is simpler, and the flying process is more intelligent.