Showing papers on "Landing gear published in 2004"

High Resolution Calculation of a Simplified Landing Gear

Abstract: A hybrid approach is used to investigate the noise generated by a simplified landing gear without small scale parts such as hydraulic lines and fasteners. The Ffowcs Williams and Hawkings equation is used to predict the noise at far-field observer locations from flow data provided by an unsteady computational fluid dynamics calculation. A simulation with 13 million grid points has been completed, and comparisons are made between calculations with different turbulence models. Results indicate that the turbulence model has a profound effect on the levels and character of the unsteadiness. Flow data on solid surfaces and a set of permeable surfaces surrounding the gear have been collected. Noise predictions using the porous surfaces appear to be contaminated by errors caused by large wake fluctuations passing through the surfaces. However, comparisons between predictions using the solid surfaces with the near-field CFD solution are in good agreement giving confidence in the far-field results.

Optimal Conceptual Design of Two-Stage Reusable Rocket Vehicles Including Trajectory Optimization

Abstract: Many candidate concepts of reusable space transportation vehicles have been proposed around the world. This paper applies an optimization method for conceptual designs of winged fully reusable rocket two-stage-to-orbit (TSTO) vehicles in both horizontal takeoff and vertical launch styles. We first describe our methods for analyzing vehicle design. Then we integrate those methods into the optimization problem, the solution of which yields the minimized parameter, defined as the total gross weight of the first-stage booster and the second-stage orbiter. This information allows us to determine the optimal vehicle configuration and flight trajectory for a highly feasible TSTO vehicle. The optimal solutions show the necessity of lightening and miniaturizing components. Vertical launch vehicles are lighter in total gross weight than horizontal takeoff vehicles. In addition to optimizing vehicle configuration, this study also optimizes ascent and return trajectories. These optimizations enable the booster to glide back to the launch site without propellant, despite the long downrange path from the staging point of the ascent trajectory.

An Empirical Model for Landing Gear Noise Prediction

Abstract: *† ‡ This paper presents an experimental investigation on aircraft landing gear noise. The study consists of systematic testing and data analysis, using the full-scale Boeing 737 landing gear. The database covers a range of mean flow Mach numbers typical of landing conditions for commercial aircraft and various landing gear configurations, ranging from a fully dressed, complete gear to cleaner configurations involving only parts of the complete gear. This enables us to reveal contributions from various groups of the gear assembly and to derive functional dependencies of the radiated noise on the flow Mach number at various far field directivity angles and on various gear geometry parameters. It is shown that the noise spectrum can be decomposed into three frequency components, namely, the low, mid and high frequency components, respectively representing contributions from the wheels, the main struts and the small details such as hoses, wires, cutouts and steps. It is found that these different frequency components have different dependencies on flow parameters and gear geometry. For example, while the low and mid frequency noise scale on the sixth power law with flow Mach number, the high frequency noise follows the eighth power Mach number scaling and has a spectral shape proportional to the inverse square of frequency, indicating the turbulent wake, instead of the unsteady forces on the gear, as the sources of the noise. This is confirmed by phased microphone array measurements, identifying a source distribution in the wake region at high frequencies. Based on the spectral decomposition in the three frequency domains, normalized spectra are derived for all three components in terms of the Strouhal numbers. A model for the Overall Sound Pressure Level (OASPL) is also developed as a function of flow and geometry parameters. For the high frequency noise generated by small features in the landing gear, a detailed description of their numbers, sizes, shapes, locations and orientations is apparently not practical so that a complexity factor is introduced to account for the aggregate effects of all the small details. This complexity factor can be empirically related to aircraft design parameters such as the maximum takeoff or landing weight. Some examples are given to show the accuracy of the empirical model and comparisons with data show very satisfactory results.

V/stol biplane

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

Aircraft landing gear actuation system

Abstract: The invention relates to an aircraft landing actuation system, comprising a door actuation device to open and close a landing gear door, and a landing gear actuation device to retract and lower the landing gear. According to the invention, the landing gear actuation system is distinguished by the fact that at least the landing gear actuation device has an electric actuator motor.

A Numerical Aeroacoustics Analysis of a Detailed Landing Gear

Abstract: This paper presents results of an unsteady simulation of a detailed nose landing gear. The discussion focuses on a steering system which is one of the most important nose landing gear source of noise. The results show that the complex geometry of the steering device generates acceleration in the flow field. The vorticies generated by the hydraulic pipes are pointed out and a wide frequency range pressure spectra is presented.

Evaluation of a Landing Gear Semi-Active Control System for Complete Aircraft Landing

Abstract: This paper deals with the simulation of landing gear semi-active control for a small trainer aircraft in a multibody framework. The behavior of single passive landing gear drop test simulation models and of a complete aircraft landing simulation model, developed and implemented in the commercial multibody code ADAMS in previous works, is compared to the that of analogous models equipped with semiactive shock absorber controllers. The control strategy and the controller tuning and sensitivity tests are briefly outlined and the results of its application to the landing gears is presented. The reduction in peak vertical attachment load values for the landing gear drop tests ranges from 5% to 35%, depending on the test conditions, and in the complete aircraft landing simulation, it is in the order of 5% to 20%, once again depending on the particular landing configuration. Comparisons between the drop tests and complete landing simulations in corresponding conditions are made, and the significant sensitivity tests are repeated on the complete aircraft model.

Full machine ground load on site calibration test method and its device

Abstract: In the present invention, carriage and landing gear are used as pivot points to make aircraft hold in level state; at this state, load is imposed onto selected section area by strain transducer unit and to record load value, in this case aircraft wing can be calibrated on line so not only load truthfulness can be ensured but also accuracy of load calibration and precision of measurement can be ensured as mechanical basis is provided for faitigue life and analog test of aircraft wing as well as for setting up load equation of aircraft wing

Airframe noise study of a Bombardier CRJ-700 aircraft model in the NASA Ames 7- by 10-foot wind tunnel

Abstract: An acoustic and aerodynamic experimental study was conducted of a 7%-scale unpowered Bombardier CRJ-700 aircraft model in the NASA Ames 7- by 10-Foot Wind Tunnel for the purpose of identifying and attenuating airframe noise sources. Simulated landing, takeoff and approach configurations were evaluated at Mach 0.22 and 0.26. With a phased-microphone array mounted in the ceiling over the inverted model, various noise sources in the high-lift system, landing gear, fins, and other miscellaneous components were located and compared for sound level and frequency at one flyover location. Numerous model modifications and noise-alleviation devices were evaluated. Simultaneous with acoustic measurements, aerodynamic forces were recorded to document aircraft conditions and any performance changes caused by the geometric modifications. Such performance changes were small and are not reported here. Ten airframe noise sources were identified that might be important to approach and landing noise of the full-scale aircra...

Towards a Permanent ACN Solution for 6-Wheel Landing Gear Aircraft

Abstract: Utilizing historical full-scale airfield pavement test data (that has been collected from the 1940's to the mid-1970's), and updating the historical record with test-to-failure data from the FAA National Airport Pavement Test Program, the pavement life cycle relationship to aircraft loading as indexed by landing gear type (dual, dual tandem, tri-tandem, etc.) has been investigated. The resulting collection of pavement failure data was analyzed for applicability to the existing S-77-1 methodology (using what is commonly referred to as the CBR equation). The investigation and analysis establishes that the CBR equation retains its usefulness for predicting pavement thickness, requirements and pavement life for airfield pavements. It is concluded that the unique solution of the CBR equation at the 10,000 coverage level for four precisely defined subgrade support conditions (as defined by ICAO ACN guidelines) continues to be well suited to the use for which it is intended. A parallel study of the FAA test results via multi-layer elastic system solutions is included, which renders a similar conclusion renders a similar conclusion.

Landing gears aerodynamic interaction noise

Abstract: Airframe noise is generated as a result of the interaction of turbulent flow with different airframe components, i.e. the high lift devices and landing gears in particular, and may dominate over engine noise in the approach phase of large commercial aircraft. This paper describes the landing gears interaction noise research work in the EC co-financed project "Significantly Lower Community Exposure to Aircraft Noise" (SILENCER). Systematic steady and unsteady landing gear wake measurements were performed on differently scaled A340 type centre and main landing gears. The analysis of wake measurements showed almost isotropic turbulence characteristics for short distances downstream. Noise measurements were performed for a main landing gear being exposed to the wake flow of a centre landing gear. It turned out that only low frequency interaction noise is likely to be radiated while at high frequencies a noise reduction is obtained due to reduced mean wake flow speed.

On-site calibrating test method and its device for landing gear load

Abstract: The present invention discloses on-site calibrating test method and device for landing gear load and is related to the safety and reliability of landing gear. The present invention features in-situ load application and calibration for landing gear under true and natural no-detachment condition to ensure the truth and precision of load calibration and measurement. The present invention solves the difficult problem of practically measuring and calibrating landing gear load of, especially, large airplane. The measured load spectrum data provides for the research and design of landing gear with important mechanical reference.

Aeroacoustic Study of a 26%-Scale Semispan Model of a Boeing 777 Wing in the NASA Ames 40- by 80-Foot Wind Tunnel

Abstract: An acoustic and aerodynamic study was made of a 26%-scale unpowered Boeing 777 aircraft semispan model in the NASA Ames 40- by 80-Foot Wind Tunnel for the purpose of identifying and attenuating airframe noise sources. Simulated approach and landing configurations were evaluated at Mach numbers between 0.12 and 0.24. Cruise configurations were evaluated at Mach numbers between 0.24 and 0.33. The research team used two Ames phased-microphone arrays, a large fixed array and a small traversing array, mounted under the wing to locate and compare various noise sources in the wing high-lift system and landing gear. Numerous model modifications and noise alleviation devices were evaluated. Simultaneous with acoustic measurements, aerodynamic forces were recorded to document aircraft conditions and any performance changes caused by the geometric modifications. Numerous airframe noise sources were identified that might be important factors in the approach and landing noise of the full-scale aircraft. Several noise-control devices were applied to each noise source. The devices were chosen to manipulate and control, if possible, the flow around the various tips and through the various gaps of the high-lift system so as to minimize the noise generation. Fences, fairings, tip extensions, cove fillers, vortex generators, hole coverings, and boundary-layer trips were tested. In many cases, the noise-control devices eliminated noise from some sources at specific frequencies. When scaled to full-scale third-octave bands, typical noise reductions ranged from 1 to 10 dB without significant aerodynamic performance loss.

Retractable landing gear for aircraft

Abstract: Retractable landing gear for an aircraft, the landing gear being of the type that is raised vertically, and comprising a plurality of independent legs, each leg comprising a structural part rigidly secured to a structure of the aircraft, a pivoting rocker beam supporting a pair of wheels, and a shock absorber In accordance with the invention, the shock absorber of each leg is extended by a positioning portion enabling the total length of the extended shock absorber to be shortened in order to collapse the leg, and each leg further comprises a positioning actuator connected in hinged manner to the extended shock absorber and arranged to lengthen relative to a normal use position in order to lengthen the corresponding leg This makes it possible to shorten and/or lengthen one or another of the legs of the landing gear while the aircraft is stationary or taxiing slowly

Landing gear, a brake, a brake-and-wheel assembly for an airplane, and a method of maintaining such landing gear

Abstract: The invention provides airplane landing gear comprising at least one axle for carrying at least one brake-and-wheel assembly comprising a rim mounted to rotate on the axle and a stack of disks and a support carrying modular electromechanical actuators that are individually removable, the landing gear and the brake-and-wheel assembly being organized in such a manner that each actuator is in at least one of the following configurations: an empty space of dimensions sufficient for receiving the actuator extends on a disassembly path directly facing the actuator when it is in an operating position; the actuator is associated with displacement means enabling it to be moved from an operating position to a disassembly position, an empty space of dimensions sufficient to receive the actuator extending along a disassembly path directly facing the actuator when it is in the disassembly position.

Simulation of Aircraft Landing Gear Dynamics Using Flexible Multibody Dynamics Methods in Simpack

Abstract: In a variety of mechanical systems friction induced vibrations are a major concern. The aircraft landing gear is by nature a complex multi-degree-of-freedom dynamic system. It may encounter various vibration modes which can be induced by brake frictional characteristics and design features. These brake induced oscillations can lead to very high loads in the landing gear and brake structure which may result in passenger discomfort and sometimes in component failure. Along with the serious fore and aft oscillations of a landing gear, often referred to as gear walk, chatter, squeal, shimmy and other vibrations in aircraft landing systems are not only annoying and disconcerting but can also affect the stability of the plane during take-off, landing, and rolling. In this paper, simulation of such an unstable and complex phenomenon during aircraft ground maneuvers is done to detect vibrations in aircraft landing gear. A commercial multibody simulation tool SIMPACK is used for this purpose. The article is based on work done in cooperation between DLR and Liebherr Aerospace.

Similarity-based modeling of aircraft flight paths

Abstract: Modeling methods based on historical data can be used to model the values of parameters describing the flight paths of both military and commercial jet aircraft. Flight path parameters that are modeled typically include: pilot inputs such as the positions of the stick or control column and control wheel, power levers, rudder pedal, and controls for the slats, spoilers, stabilizer, and landing gear; control surface and controller responses such as the positions of the ailerons, elevators, flaps, rudder, slats, spoilers, stabilizer, and fuel flows; and aircraft responses such as airspeed, altitude, angle of attack, acceleration components, pitch, roll, yaw, the speeds of the low-pressure and high-pressure turbines, and exhaust gas temperatures. The utility of the models lies in their ability to confirm normal behavior and to detect abnormal behavior of control surfaces and engine systems during takeoff, cruise, and landing. Examples of several methods applied to a newly manufactured military jet to confirm acceptance test results during an entire flight are illustrated. Also illustrated are examples of several methods applied to the analysis of a commercial jet aircraft incident involving a control surface failure during a landing approach, an analysis that illustrates the capability of the method to support fault isolation. One of the versions, a similarity-based modeling method, exhibits a superior ability to achieve the intended purposes.

Decoupled steering/planing air vehicle nose landing gear

Abstract: A landing gear assembly comprises a landing gear strut assembly further comprising a landing gear strut having a longitudinal axis and extending from an inboard end to an outboard end capable of attaching to a wheel, and a landing gear housing. The landing gear housing has a longitudinal axis coincident with the landing gear strut longitudinal axis and having an interior chamber capable of accepting a portion of the landing gear strut. The landing gear housing is capable of pivotably coupling to an aircraft. The landing gear assembly further comprises a retraction linkage having an inboard end capable of coupling to the aircraft and an outboard end coupled to the landing gear housing. The retraction linkage is moveable to retract the landing gear strut assembly into an aircraft landing gear compartment about the landing gear housing pivotable aircraft coupling. The landing gear assembly further comprises a steering linkage capable of coupling and decoupling to the landing gear strut and, when coupled, capable of steerably rotating the landing gear strut with respect to the landing gear housing about the coincident longitudinal axis. The landing gear assembly further comprises a planing linkage that can gradually rotate the landing gear strut into a planar position as the landing gear strut assembly is retracted and decoupled from the steering linkage.

Alighting gear for aircraft

Abstract: PROBLEM TO BE SOLVED: To enhance the workability of manually lighting up and down a landing gear during the ground maintenance or during an emergency landing gear lowering mode by automatically operating a bypass valve in an alighting gear for aircraft. SOLUTION: An alighting gear for aircraft comprises a landing gear 21 accommodated in a fuselage, an up-line 45 to lead a pressurized working fluid to a landing gear operating actuator 7 when accommodating the landing gear 21 in the aircraft alighting gear with the landing gear 21 driven by hydraulic pressure via the landing gear operating actuator 7, a down-line 46 to lead the pressurized working fluid to the landing gear operating actuator 7 when the landing gear 21 is developed, and a first bypass valve 6 having an opening to enable the manual operation of the landing gear operating actuator 7. The first bypass valve 6 automatically switches pressure to the opening when internal pressure is dropped after the landing gear operating actuator 7 is stopped with working fluid pressure in the up-line 45 and the down-line 46 as pilot pressure. COPYRIGHT: (C)2004,JPO

Semi-trailer landing gear ratcheting apparatus

Abstract: A manual cranking apparatus for the landing gear of a semi-trailer. The cranking apparatus includes a rotatable mechanism that is permanently connected to the cross-shaft of the landing gear. The rotatable mechanism is adapted to be folded such that, in storage position, the mechanism is positioned beneath the trailer.

Landplane to flying boat conversion

Abstract: An aerodynamically efficient fiberglass hull consisting of a pointed bow, a step amidships, and aft section coming to a point which will be attached to the hull of land aircraft and convert them to water operations. In addition, one wing float will be securely attached to the outboard section of each wing. The main and nose landing gear will be removed enabling the propellers to have adequate clearance from water. Landing gear removal procedures will not be used for amphibious aircraft.

Control of an electro-hydrostatic actuation system for the nose landing gear of an "all electric aircraft"

Abstract: The EU research Project Power Optimised Aircraft (POA) investigates the approach to replace primary hydraulic supply by extended electric power systems towards a More or All Electric Aircraft [4]. This contribution presents an electrically powered actuation system for nose landing gears using an EHA (electrohydrostatic actuator) approach. One motor pump unit supplies door and gear actuation as well as the steering system. Different control strategies for the individual actuators are introduced. The effects of different control strategies are shown by simulation results.

Composite materials for structural landing gear components

Abstract: Composite materials are widely used in the aerospace industry. The application however of composites within a single load-path primary structure, such as the aircraft landing gear system, is far from common. Developments in new composite materials and new manufacturing techniques offer improved characteristics and design potential, for the application of these materials in Structural Landing Gear Components.

Method and apparatus for braking and maneuvering

Abstract: Aircraft landing gear assembly comprising a hub motor / generator comprises a wheel strut and with respect to the alternating wheels are mounted turntable and each stator disc. The present invention may be a wheel hub motor / generator power before the wheels touch the ground, acting as a motor so as to allow the wheels to turn up. Wear slip when the tire which can reduce the speed of the aircraft relative to the speed difference between the speed of the ground, which helps reduce tire touching the ground. After ground, the wheel hub motor / generator as a generator, regenerative braking force which may be applied and / or motorized braking force to the wheels. Usable electrical energy generated by the resistor is dissipated in the landing and taxiing / or stored for later use, for example, taxi, and a motor to power the aircraft. The present invention is given, a method and apparatus of the present invention and the ABS for the front landing gear braking.

Multidisciplinary Optimization Process for the Conceptual Design of Landing Gears for Blended Wing Body Configurations

Abstract: New aircraft configurations like the blended wing-body (BWB) are expected to improve the performance and economic efficiency of the future air transport. However, new challenges also arise requiring new processes in the design which are not available from conventional aircraft. Landing gear design which involves the analysis of complex dynamical systems and also encompasses many engineering disciplines such as structural mechanics and weights is one of these challenges. In this paper the first step of an attempt to develop an optimization process in order to find the optimum BWB landing gear design is presented. The process is implemented in the beginning of the configuration or conceptual phase of the design. This allows the search for a configuration with a better potential for the optimum design which, in the end, will results in a better overall design. The interesting aspect of the process is the integration of Multibody Simulation (MBS) tools for the analysis of the structural dynamic behavior during the optimization. Such a simulation approach delivers information which cannot be obtained from simpler methods used for conventional aircraft. In this paper two different main landing gear configuration concepts are analyzed and optimized. The MBS modeling of the two concepts is shown. The integration of the MBS into the optimization process is presented. Finally the results of the optimization are presented and discussed. While this paper shows the first step of an attempt to establish such a new design process, its purpose is to establish a useful foundation for further study and it can also be regarded as a work-in-progress paper for future investigations.