Showing papers on "Landing gear published in 1996"

A method for landing gear modeling and simulation with experimental validation

Abstract: This document presents an approach for modeling and simulating landing gear systems Specifically, a nonlinear model of an A-6 Intruder Main Gear is developed, simulated, and validated against static and dynamic test data This model includes nonlinear effects such as a polytropic gas model, velocity squared damping, a geometry governed model for the discharge coefficients, stick-slip friction effects and a nonlinear tire spring and damping model An Adams-Moulton predictor corrector was used to integrate the equations of motion until a discontinuity caused by a stick-slip friction model was reached, at which point, a Runga-Kutta routine integrated past the discontinuity and returned the problem solution back to the predictor corrector Run times of this software are around 2 mins per 1 sec of simulation under dynamic circumstances To validate the model, engineers at the Aircraft Landing Dynamics facilities at NASA Langley Research Center installed one A-6 main gear on a drop carriage and used a hydraulic shaker table to provide simulated runway inputs to the gear Model parameters were tuned to produce excellent agreement for many cases

Emergency soft-landing system for rotor-type aircraft

Abstract: An emergency soft-landing system (10) for use on a rotor-type aircraft such as a helicopter (70). The system (10) includes at least one parachute-containing structure (12) that houses at least one parachute (50). The structure (12) is designed to be selectivelly attached to various locations on the helicopter's lower surface (76), the sides (82), and to the landing gear struts (85). The parachute (50) is deployed from the structure (12) when an out-of-control landing is unavoidable or an extreme emergency exists. The system (10) can be designed so that the parachute-containing structure (12) operates in combination with an airbag (60). An airbag can be attached to the helicopter's lower surface (76) near the rear end (78), and front end (80), and to the center of the helicopter between the landing gear (84). The parachute(s) (50) and airbag(s) (60) are designed to be manually deployed by a helicopter crew member or automatically by a dynamic responsive switch (34). The switch (34) is enabled when the helicopter reaches a specified altitude or an abnormal rate of descent.

Aircraft braking system with damped brake rod

Abstract: The invention is directed to a damped brake rod for use in an aircraft landing gear, the landing gear comprising a strut and a wheel and brake assembly carried on the strut. The brake rod connects the wheel and brake assembly to the strut and bears an axial load during braking. The brake rod is laterally damped to dissipate lateral vibrations imparted to the brake rod during braking.

Guidance and Control Design for High-Speed Rollout and Turnoff (ROTO)

Abstract: A ROTO architecture, braking and steering control law and display designs for a research high speed Rollout and Turnoff (ROTO) system applicable to transport class aircraft are described herein. Minimum surface friction and FMS database requirements are also documented. The control law designs were developed with the aid of a non-real time simulation program incorporating airframe and gear dynamics as well as steering and braking guidance algorithms. An attainable objective of this ROTO system, as seen from the results of this study, is to assure that the studied aircraft can land with runway occupancy times less then 53 seconds. Runway occupancy time is measured from the time the aircraft crosses the runway threshold until its wing tip clears the near side of the runway. Turnoff ground speeds of 70 knots onto 30 degree exits are allowed with dry and wet surface conditions. Simulation time history and statistical data are documented herein. Parameters which were treated as variables in the simulation study include aircraft touchdown weight/speed/location, aircraft CG, runway friction, sensor noise and winds. After further design and development of the ROTO control system beyond the system developed earlier, aft CG MD-11 aircraft no longer require auto-asymmetric braking (steering) and fly-by-wire nose gear steering. However, the auto ROTO nose gear hysteresis must be less than 2 degrees. The 2 sigma dispersion certified for MD-11 CATIIIB is acceptable. Using this longitudinal dispersion, three ROTO exits are recommended at 3300, 4950 and 6750 feet past the runway threshold. The 3300 foot exit is required for MD-81 class aircraft. Designs documented in this report are valid for the assumptions/models used in this simulation. It is believed that the results will apply to the general class of transport aircraft; however further effort is required to validate this assumption for the general case.

A Physically Representative Aircraft Landing Gear Model for Real-Time Simulation.

Abstract: : A detailed aircraft landing gear model developed by the authors is presented. The advantages of this model are numerous. Its accuracy is sufficient for engineering analysis, yet it is applicable to real-time applications. The model is able to represent the complex ground reaction behavior required by such conditions as damaged runways, moving landing surfaces, high surface winds, and large asymmetric loads. The various subsystems are modeled in an intuitive manner, facilitating identification of any physical property by the user.

Electrorheology for smart landing gear

Abstract: Electrorheological (ER) technology was explored for its suitability to the continuous control of force and motion in aircraft landing gear. Although the state of knowledge on all types of active suspensions was examined, the analytical and experimental portions of the study focused upon the control of damping, alone. A specific class of ER damper designs was selected by means of a generalized analysis that modeled the ER fluid as a "bingham" plastic material. This analysis reveals the advantage of ER damping devices that minimize shear rates such that static shear stresses tend to dominate the damper's response. A prototype damping device in this class was constructed and simplified response parameters of the device were measured. Alternative formulations of the ER fluid are discussed and the employed test fluid is described. An analysis of the landing transient for an example military aircraft was performed so that the nominal performance of an ER-based damping controller could be estimated. The study observes that although ER technology offers promise over the long term, current limitations in fluid performance severely constrain the application to aircraft landing gear.

Flight Determination of Configurational Effects on Aircraft Stall Behavior.

Abstract: The objective of this paper is to investigate the influence of changes in aircraft's configuration, such as those caused by a deflected flap or a landing gear, on its stall characteristics. To this end, stall model in statespace is extended to account for asymmetric unsteady effects and applied to quasisteady and dynamic stall maneuvers for different landing flap settings with landing gear in up and down positions. Identification results, obtained applying nonlinear max imum likelihood parameter estimation method, clearly show that a change in the aircraft's configuration has a dominant effect on flow separation which significantly alters the aircraft's stall behavior. Qualitatively, the proposed model structure is able to represent these effects fairly well. Efficacy of the model and sensitivity of stall to configurational changes has been demonstrated with the aid of typical results obtained from analysis of quasisteady stall data for two different landing flap positions and for that with landing gear down.

Main landing gear having tilting of main gear pivot pins

Abstract: A main landing gear system which employs Ackermann type steering utilizing kingpins and tierods wherein a plurality of paired wheels are employed and wherein each truck axle is adapted for independent steering Electronic control means along with hydraulic directional valve means are utilized A main landing gear having single wheel or king pin steering Pivot pin tilting is utilized in truck type main landing gear, eg where a truck axle is adapted for independent steering or where single wheel or king pin steering is utilized

Verification of a Large Discrete System using Algebric Methods

Abstract: Symbolic algebraic modeling and analysis techniques for DEDS are applied to the landing gear subsystem in the new Swedish fighter aircraft, JAS 39 Gripen. Our methods are based on polynomials over ...

Easy-attachable wheel apparatus for helicopters

Abstract: An easily-attachable supplemental wheel apparatus that allows one person to perform the ground-handling functions necessary to maneuver an aircraft or helicopter having a skid configured landing gear. The apparatus includes an axle extending across the landing skids having a pair of spaced eyelets attached to the axle in such a position that one of the landing skids can easily slide through each eyelet. The apparatus includes a pair of wheels rotatably attached to the axle to allow for easy ground movement along with an attachment for securing the axle to the airframe.

Landing gear cooling device for space shuttle

Abstract: PURPOSE:To enable the positive cooling of a landing gear exposed to aerodynamic heating at the time of re-entry of the tire of the like of a space shuttle without providing a cooling device. CONSTITUTION:A landing gear chamber 90 for storing a landing gear (tire 6, gear column 7, and the like) is provided with a closable gear door 3. At the gliding time after re-entry, this gear door 3 is opened by an opening means such as an operating cylinder 1 and a gear door operating rod 2 to take in outside air, and the landing gear is taken into the gear chamber 9 to cool the aerodynamically heated landing gear.

Multi-stage space transport system and method for horizontal-takeoff

Abstract: The transport system consists of a flight module (2) with a reusable aerodynamic carrier module (1). The flight module has a drive unit, especially a rocket, (5) which is the only drive for the combination of modules. The carrier module has tanks to supply fuel and oxidant to the rocket. The carrier module has landing gear (4). The fuel tanks have separating valves in the supply lines (9,10) for detachable connection to the rocket in the flight module. The flight module may be slung underneath the carrier module in the region of the landing gear.

Algorithms for aircraft trim analysis on ground

Abstract: In the analysis of aircraft dynamics for up and away flight, the general practice consists of trimming the aircraft for a specific manoeuvre at a specified altitude and mach number. In this paper conditions for quasi-steady equilibrium are motivated for aircraft dynamics in the ground roll phase. Algorithms for implementation of these conditions are also described. By use of these algorithms, the locus of trim points is obtained for a comprehensive take-off manoeuvre of a delta wing aircraft beginning with ground roll, followed by rotation and ending in lift-off. This result is compared with approximate calculations wherein the landing gear states are ignored and linear aerodynamics is assumed. The exact result is also compared with the simulation of the take-off manoeuvre in a pilot in the loop simulator.

Flying vehicle landing-gear retraction and extension drive

Abstract: FIELD: aeronautical engineering. SUBSTANCE: drive has control lever mounted in crew cabin and aerodynamic surface mounted on landing gear leg for rotation about this leg; control lever is mechanically linked with aerodynamic surface. EFFECT: reduction of power and mass of units of landing-gear retraction and extension system mounted on flying vehicle. 2 dwg

Device promoter wheelspin landing gear for aircraft. (Machine-translation by Google Translate, not legally binding)

Abstract: Device promoter wheelspin landing gear for planes, to be useful in all types of aircraft, wherein the device promoter wheelspin landing gear for planes, comprising a body (3) alabear, attachable to the rim of the wheels (2) solidarity covers wheel (2). (Machine-translation by Google Translate, not legally binding)

Nose landing gear assembly for a catapult launched airplane

Abstract: A nose landing gear assembly for an airplane which can be launched with catapult assistance. The landing gear assembly includes a nose strut, upper drag link, lower drag link, launch bar and launch bar actuator. When the nose shut is in the extended position, the upper drag link, lower drag link and launch bar form a direct load path between the catapult shuttle and the airplane thereby avoiding subjecting the nose strut to loads reacted from the shuttle. The nose strut, launch bar, launch bar actuator and airplane fuselage form a first four bar linkage. Furthermore, the nose strut, upper drag link, lower drag link and airplane fuselage form a second four bar linkage such that during retraction of the nose strut, the launch bar, launch bar linkage, upper drag link and lower drag link are caused to move up and into the airplane wheel well.

Comparison of Hover/Ground-Effect Characteristics for a Joint Strike Fighter Configuration

Abstract: Hover and ground-effect tests were conducted with the Lockheed-Martin Large Scale Powered Model (LSPM) during June-November 1995 at the NASA Ames Research Center's Outdoor Aerodynamics Research Facility (OARF) This was done in support of the Joint Strike Fighter (JSF) Program being lead by the Department of Defense The program was previously metered to as the Joint Advanced Strike Technology (JAST) Program The tests at the OARF included: engine thrust calibrations out of ground effect, measurements of individual nozzle jet pressure decay characteristics, and jet-induced hover force and moment measurements in and out of ground effect The engine calibrations provide data correlating propulsion system throttle and nozzle settings to thrust forces and moments for the bare fuselage with the wings, canards, and tails removed This provides propulsive forces and moments while minimizing any of the effects due to the presence of the airframe The engine calibrations were used later to determine thrust for hover testing at the OARF and for transition testing which took place in the NASA Ames 80 by 120 foot Wind Tunnel The jet decay characteristics reflect the jet entrainment properties and are related to the aircraft suckdown characteristics The JSF program provided the opportunity to obtain model scale effects using two models; one at small scale and one at large scale Examples of data from these tests will be presented out of ground effect which will demonstrate the effect of scale For one JSF configuration, two small-scale models and one large-scale model were tested and obtained different values for the lift loss out of ground effect These differences were examined and are found to be largely dependent on the jet efflux characteristics The jet-induced hover forces and moments are presented in and out of ground effect For the hover testing the model is methodically built up from the bare fuselage, to include the wings, canards, and vertical tails, to determine the effects of each Other components such as weapons bay doors, landing gear doors, and other lift improvement devices and their effect on the jet-induced forces and moments are examined

Flying vehicle retractable landing gear

Abstract: FIELD: aeronautical engineering. SUBSTANCE: landing gear has leg 2 with breaker strut 7, wheeled bogie 5 with shock absorber 9. Wheeled bogie is articulated to strut by means of lever 11. Landing gear is provided with bogie turning mechanism which consists of system of articulated bell cranks 12 and 13 and rods 3 and 14. Double-arm bell crank 13 is articulated on strut; one arm of bell crank 13 is connected with rod 3 and other arm is connected to bell crank 12 by means of rod 14. EFFECT: enhanced efficiency of retracting the landing gear in fuselage. 3 cl, 7 dwg

Device to support steering of aircraft in landing stage

Abstract: PROBLEM TO BE SOLVED: To assist piloting of an aircraft at a landing stage by actuating an integrating means on detecting the crossing of a lower value of a threshold of height with respect to the ground, detecting the crossing of an upper value of a threshold of distance according to its actuation signal, and issuing an alarm when a load sensor doest not detect landing of wheels. SOLUTION: A projection device 13 is controlled by a sign generator 14 which receives updating commands from a computer 15 with programmed logic. The computer 15 is connected to a navigation system 10, the outputs of ILS glide slope and localizer receivers 11 and the output of a load sensor 16 sensitive to the pressure of the hydraulic shock absorbers of a main landing gear and, for updating various reticules displayed on a collimator 12, calculates the distance traveled from the threshold of the runway by integrating ground speed on detecting the crossing of a lower value of a threshold of height with respect to the ground. When an upper value of the threshold of distance is crossed without landing, the load sensor 16 actuates an alarm to assist piloting.

Overload protection for an aircraft nose landing gear attached to an aircraft tractor without a towbar

Abstract: The present invention relates to an overload protection for an image captured by a rodless aircraft tractor nose landing gear of an aircraft. When the overload protection according to an embodiment of the receiving device for the front landing gear of an aircraft is an overload protection provided to the aircraft tractor within the telescoping arms (9). This overload protection consists of shear pins (28), designed in accordance with the respective permissible nose wheel load, wherein the shear pin (28) on the cylinder piston rod (26) and the cylinder tubes (30) secure the telescope tips (25). In addition, a safety bolt (27) with a safety margin (29) within each cylinder piston rod (28) is provided in each case. In case of overload, caused by tensile or compressive forces that exceed the maximum allowable value for the nose gear load values, and after shearing of the shear pin (28), the cylinder piston rod (26) may within the safety game (29) in the cylinder tubes (30) in the longitudinal direction of the aircraft tractor to a certain extent in both directions freely.

Computer Simulation of the Bi-Stable Valve in the A340 Landing Gear:

Abstract: The increasing use of simulation for both circuit and component analysis in the aircraft industry has come about due to the requirement for acceptable transient as well as steady state performance of aircraft systems. The computer simulation package, Bathfp, developed at the Fluid Power Centre, University of Bath, is suitable for investigations into both of these. Utilities are provided which allow a model of a complicated system or component to be built up from its elements, which can be introduced to the model library of components so that particular dedicated areas of interest such as flight control actuation systems and braking and landing gear may be examined in detail. Component models enable the internal details of valves, pumps, motors, actuators and other elements to be simulated to a high degree of accuracy.This paper describes the application of the simulation package to perform a detailed analysis of the bi-stable valve in the A340 landing gear shock absorber. In the original design, a malfunc...

Aerodynamic interference of dissimilar aircraft flying in close proximity

Abstract: Introduction O Jan. 14, 1992, an F-14A aircraft experienced an unsafe landing gear indication prior to recovery at a Naval air station. The air crew requested a chase aircraft to conduct a visual inspection of their landing gear in accordance with standard operating procedures. A T-34C aircraft with instructor and student pilot joined on the F-14 to inspect the landing gear. Shortly after the F-14 crew was notified that their gear looked good, the T-34 collided with the substantially larger aircraft. The T-34 and air crew were lost and the F-14 received minor damage and returned to the airfield. A study of Navy and Air Force midair collisions involving formation flying over the past 10 years has shown that pilot error is the predominant common denominator. Task saturation, preoccupation with cockpit duties, and failure to judge closure rates and to take sufficient, timely, and appropriate action to avoid a collision are major factors in mishap findings.' Mutual aerodynamic interference of aircraft in close proximity is rarely discussed in mishap findings or in flight training, yet may be a significant causal factor. Interference of airflow over lifting surfaces, because of the pressure field of another aircraft and to the changes in local flow direction, can alter the aerodynamic characteristics of the trailing aircraft. Unexpected changes in lift and pitching moments may occur that affect closure rate and task saturation of the unaware or uninformed pilot. A numerical study of the aerodynamic interference between dissimilar aircraft in close proximity was conducted. The example aircraft involved a T-34 flying beneath an F-14 in an approach configuration. A short training video and report were produced for the Naval Air Systems Command to indicate the causal mechanisms of the aerodynamic interference and the trim changes to be expected by the pilot in such a situation with the aim of improving aviation safety education. This Note briefly describes the results of the study. For more complete information see Ref. 5.

Full-Scale A320 Landing Gear Airframe Noise Characteristics

Abstract: Flyover noise levels of today's aircraft in the approach configuration - i.e. with slats, flaps and gears deployed -are occasionally dominated by airframe noise contributions. Initial airframe noise tests were performed in the German-Dutch Wind Tunnel, employing full-scale A320 landing gears. Farfield noise characteristics were determined from measurements with different gear configurations (covering different gear elements with streamlined fairings) at wind speeds ranging from 40 to 78 m/s. Aerodynamic noise from landing gears turnes out to be broadband with constant levels in 1/3-oct. bands up to 3 kHz. Levels increase corresponding to the 6th power of flow velocity. From the results of this study it is expected that a noise reduction potential of up to 5 EPNdB could be realized through localized applications of streamlined fairings and/or flow spoilers.

Aircraft trailing-edge assembly

Abstract: FIELD: aeronautical engineering; swept wings of medium-capacity and heavy aeroplanes whose landing gear wing legs are retracted into trailing-edge assembly and in fuselage well. SUBSTANCE: trailing-edge assembly is additionally provided with beam 12, under-wing beam 5 secured on wing torsion box 1 under tail boom inside flap mechanism fairing 4 whose attachment units are mounted on cantilever formed by tail boom and under-wing beam. Articulated attachment unit of landing gear beam and tail boom is hinged to one end of additional beam 12 which is connected in its turn with wing torsion box. Bell crank 8 connecting landing gear beam 6 with fuselage 7 is articulated to side strut 10 of landing gear. Attachment of panels 14 with wing torsion box 1 is of floating construction. EFFECT: reduced mass of wing and increased service life of wing structure due to reduction and redistribution of load exerted on wing torsion box by attachment units of landing gear. 6 dwg

Dynamic verification of a large discrete system [aircraft landing gear controller]

Abstract: Symbolic algebraic analysis techniques are applied to the landing gear subsystem in the Swedish fighter aircraft, JAS 39 Gripen Our methods are based on polynomials over finite fields (with Boolean algebra and propositional logic as special cases) Polynomials are used to represent the basic dynamic equations for the processes (controller and plant) as well as static properties of these Temporal algebra (or temporal logic) is used to represent specifications of system behaviour These specifications are verified both on a model of the landing gear controller, and a model of the closed loop behaviour of the landing gear controller connected to a plant The model of the landing gear controller is made from the actual implementation in Pascal The tools used are developed by the authors in Mathematica and uses an efficient implementation of binary decision diagrams