SEARCH · Engineering Papers

Results for “Landing Gear”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13

All sources NASA NTRS DOE OSTI

NASA NTRS1989

The role of optimization in the next generation of computer-based design tools

There is a close relationship between design optimization and the emerging new generation of computer-based tools for engineering design. With some notable exceptions, the development of these new tools has not taken full advantage of recent advances in numerical design optimization theory and practice. Recent work in the field of design process architecture has included an assessment of the impact of next-generation computer-based design tools on the design process. These results are summarized, and insights into the role of optimization in a design process based on these next-generation tools are presented. An example problem has been worked out to illustrate the application of this technique. The example problem - layout of an aircraft main landing gear - is one that is simple enough to be solved by many other techniques. Although the mathematical relationships describing the objective function and constraints for the landing gear layout problem can be written explicitly and are quite straightforward, an approximation technique has been used in the solution of this problem that can just as easily be applied to integrate supportability or producibility assessments using theory of measurement techniques into the design decision-making process.

Rogan, J. Edward↗

NASA NTRS1950

Ditching Investigation of a 1/14-Scale Model of the Northrop C-125 Airplane

An investigation of a 1/14-scale dynamically similar model of the Northrop C-125 airplane was made to determine the ditching characteristics and proper ditching technique for the airplane. Various conditions of damage, landing attitude, flap setting, and speed were investigated. The behavior of the model was determined from visual observations, motion-picture records, and time-history deceleration records. The results of the investigation are presented in table form, photographs, and curves. It was concluded that the airplane should be ditched at a nose-high landing attitude (near 8 deg) with flaps full down. The fixed landing gear will cause the airplane to dive. The fuselage will be damaged and will probably flood rapidly. Longitudinal decelerations will be about 4g and the length of landing run will be about two fuselage lengths. If the main landing gear could be jettisonable or retractable the ditching characteristics would be greatly improved.

Fisher, Lloyd J.↗

NASA NTRS1956

Ditching Investigation of a 1/12-Scale Model of the Douglas F4D-1 Airplane, TED No. NACA DE 384

A ditching investigation was made of a l/l2-scale dynamically similar model of the Douglas F4D-1 airplane to study its behavior when ditched. The model was landed in calm water at the Langley tank no. 2 monorail. Various landing attitudes, speeds, and configurations were investigated. The behavior of the model was determined from visual observations, acceleration records, and motion-picture records of the ditchings. Data are presented in tables, sequence photographs, time-history acceleration curves, and attitude curves. From the results of the investigation, it was concluded that the airplane should be ditched at the lowest speed and highest attitude consistent with adequate control (near 22 deg) with landing gear retracted. In a calm-water ditching under these conditions the airplane will probably nose in slightly, then make a fairly smooth run. The fuselage bottom will sustain appreciable damage so that rapid flooding and short flotation time are likely. Maximum longitudinal deceleration will be about 4g and maximum normal acceleration will be about 6g in a landing run of about 420 feet, In a calm-water ditching under similar conditions with the landing gear extended, the airplane will probably dive. Maximum longitudinal decelerations will be about 5-1/2g and maximum normal accelerations will be about 3-1/2g in a landing run of about 170 feet.

Windham, John O.↗

NASA NTRS1975

Landing pressure loads of the 140A/B space shuttle orbiter (model 43-0) determined in the Rockwell International low speed wind tunnel (OA69), volume 1

Wind tunnel tests of a 0.0405 scale model of the -1404A/B configuration of the Space Shuttle Vehicle Orbiter are presented. Pressure loads data were obtained from the orbiter in the landing configuration in the presence of the ground for structural strength analysis. This was accomplished by locating as many as 30 static pressure bugs at various locations on external model surfaces as each configuration was tested. A complete pressure loads survey was generated for each configuration by combining data from all bug locations, and these loads are described for the fuselage, wing, vertical tail, and landing gear doors. Aerodynamic force data was measured by a six component internal strain gage balance. This data was recorded to correct model angles of attack and sideslip for sting and balance deflections and to determine the aerodynamic effects of landing gear extension. All testing was conducted at a Mach number of 0.165 and a Reynolds number of 1.2 million per foot. Photographs of test configurations are shown.

Soard, T. L.↗

NASA NTRS1979

Airframe noise measurements on a small-scale model of a supersonic transport concept in an anechoic flow facility

Airframe noise has been measured on a .015 scale model of an advanced supersonic transport concept (AST-100) in an anechoic flow facility. The model was equipped with leading- and trailing-edge flaps, nose and main landing gears, and engine nacelles. Each of these components was deployed, individually and collectively, to determine their contribution to the noise field. Results are presented which show that in the clean configuration the aircraft displays a symmetric dipole directivity, whereas in the more complex landing-approach configuration the directivity peaks in the forward quadrant. It was found that the landing-approach noise was due chiefly to the landing gear, the trailing edge flaps, and the aeroacoustic interaction between the two

Preisser, J. S.↗

NASA NTRS1954

Contribution to the theory of tail-wheel shimmy

A basic theoretical and experimental investigation is made of the shimmy behavior of a swiveling landing gear, the experimental tests being conducted with a small wheel mounted over a continuous belt. Effects of wheel loading, rolling velocity, rearward position of the wheel with respect to the swivel axis, tire elasticity, and torsional flexibility of the fuselage are investigated both experimentally and theoretically. A major theoretical conclusion is that the motion of a landing gear moving in a straight line without fuselage elasticity is stable for a sufficiently large rearward position of the wheel behind the swivel axis, and this conclusion is well verified quantitatively by the experimental data.

LOADS, LANDING - GROUND-RUN, LAND↗

NASA NTRS1981

Current Research in Aircraft Tire Design and Performance

A review of the tire research programs which address the various needs identified by landing gear designers and airplane users is presented. The experimental programs are designed to increase tire tread lifetimes, relate static and dynamic tire properties, establish the tire hydroplaning spin up speed, study gear response to tire failures, and define tire temperature profiles during taxi, braking, and cornering operations. The analytical programs are aimed at providing insights into the mechanisms of heat generation in rolling tires and developing the tools necessary to streamline the tire design process and to aid in the analysis of landing gear problems.

Tanner, J. A.↗

NASA NTRSDate not supplied

Aeroacoustic Computations of a Generic Low Boom Concept in Landing Configuration: Part 1 - Aerodynamic Simulations

Computational results are presented for a 15%-scale, full-span, generic low-boom concept aircraft model simulated as installed in the NASA Langley Research Center 14- by 22-Foot Subsonic Tunnel and in free-air conditions. The simulations were conducted with the lattice Boltzmann solver PowerFLOW® to capture the time-accurate characteristics of the flow. The aerodynamic behavior of the aircraft was investigated with various combinations of flap and landing gear deployments. To replicate the flow speed used during tests of the model, a Mach number of approximately 0.20 was chosen while varying the angle of attack through a limited range. Analyses were performed on local flow quantities, global forces, as well as flow distributions between configurations. Aerodynamic quantities were shown to be sensitive to mesh resolution levels, especially with flap and landing gear systems retracted. When comparing wind tunnel to free-air simulations, the aerodynamic quantities sampled were found to be in good agreement, suggesting that tunnel blockage and model support effects did not adversely impact the aerodynamic behavior of the model during the wind tunnel test. The results of this study improve our understanding of the highly complex, vortical flow generated by configurations with swept, low aspect-ratio wings at speeds encountered during landing operations.

low boom↗

NASA NTRS2019

Measured and Simulated Acoustic Signature of a Full-Scale Aircraft with Airframe Noise Reduction Technology Installed

Microphone phased-array and pole-mounted microphone data gathered during the NASA Acoustics Research Measurements flight tests were used to benchmark results from companion full-scale aeroacoustics simulations. Conducted with the lattice Boltzmann solver PowerFLOW®, the simulations predicted the acoustic behavior of various tested aircraft configurations. Emphasis was placed on those flown during the third flight test - a Fowler flap-equipped Gulfstream G-III with and without noise abatement technology on the main landing gear. Direct comparisons between experimental and synthetic microphone phasedarray data were achieved by applying the same processing and deconvolution technique to both sets of data. To extend the validation of the computations to the metric used for noise certification, the Effective Perceived Noise Level, a high-fidelity digital model of the nose landing gear, which was excluded from earlier computations, was developed and integrated into the G-III aircraft geometry. The acoustic study presented here demonstrates that the simulated beamform maps and corresponding integrated farfield spectra accurately predict the locations and strengths of the prominent airframe noise sources present on the G-III aircraft.

Khorrami, Mehdi R.↗

NASA NTRS2003

Shuttle Systems 3-D Applications: Application of 3-D Graphics in Engineering Training for Shuttle Ground Processing

This project illustrates an animation of the orbiter mate to the external tank, an animation of the OMS POD installation to the orbiter, and a simulation of the landing gear mechanism at the Kennedy Space Center. A detailed storyboard was created to reflect each animation or simulation. Solid models were collected and translated into Pro/Engineer's prt and asm formats. These solid models included computer files of the: orbiter, external tank, solid rocket booster, mobile launch platform, transporter, vehicle assembly building, OMS POD fixture, and landing gear. A depository of the above solid models was established. These solid models were translated into several formats. This depository contained the following files: stl for sterolithography, stp for neutral file work, shrinkwrap for compression, tiff for photoshop work, jpeg for Internet use, and prt and asm for Pro/Engineer use. Solid models were created of the material handling sling, bay 3 platforms, and orbiter contact points. Animations were developed using mechanisms to reflect each storyboard. Every effort was made to build all models technically correct for engineering use. The result was an animated routine that could be used by NASA for training material handlers and uncovering engineering safety issues.

Godfrey, Gary S.↗

NASA NTRS2015

Evaluation of Airframe Noise Reduction Concepts via Simulations Using a Lattice Boltzmann Approach

Unsteady computations are presented for a high-fidelity, 18% scale, semi-span Gulfstream aircraft model in landing configuration, i.e. flap deflected at 39 degree and main landing gear deployed. The simulations employ the lattice Boltzmann solver PowerFLOW® to simultaneously capture the flow physics and acoustics in the near field. Sound propagation to the far field is obtained using a Ffowcs Williams and Hawkings acoustic analogy approach. In addition to the baseline geometry, which was presented previously, various noise reduction concepts for the flap and main landing gear are simulated. In particular, care is taken to fully resolve the complex geometrical details associated with these concepts in order to capture the resulting intricate local flow field thus enabling accurate prediction of their acoustic behavior. To determine aeroacoustic performance, the farfield noise predicted with the concepts applied is compared to high-fidelity simulations of the untreated baseline configurations. To assess the accuracy of the computed results, the aerodynamic and aeroacoustic impact of the noise reduction concepts is evaluated numerically and compared to experimental results for the same model. The trends and effectiveness of the simulated noise reduction concepts compare well with measured values and demonstrate that the computational approach is capable of capturing the primary effects of the acoustic treatment on a full aircraft model.

Fares, Ehab↗

NASA NTRS2015

Strain Gage Loads Calibration Testing with Airbag Support for the Gulfstream III SubsoniC Research Aircraft Testbed (SCRAT)

This paper describes the design and conduct of the strain-gage load calibration ground test of the SubsoniC Research Aircraft Testbed, Gulfstream III aircraft, and the subsequent data analysis and results. The goal of this effort was to create and validate multi-gage load equations for shear force, bending moment, and torque for two wing measurement stations. For some of the testing the aircraft was supported by three airbags in order to isolate the wing structure from extraneous load inputs through the main landing gear. Thirty-two strain gage bridges were installed on the left wing. Hydraulic loads were applied to the wing lower surface through a total of 16 load zones. Some dead-weight load cases were applied to the upper wing surface using shot bags. Maximum applied loads reached 54,000 lb. Twenty-six load cases were applied with the aircraft resting on its landing gear, and 16 load cases were performed with the aircraft supported by the nose gear and three airbags around the center of gravity. Maximum wing tip deflection reached 17 inches. An assortment of 2, 3, 4, and 5 strain-gage load equations were derived and evaluated against independent check cases. The better load equations had root mean square errors less than 1 percent. Test techniques and lessons learned are discussed.

flight tests↗

NASA NTRS2019

Assessment of Airframe Noise Reduction Technologies Based on EPNL from Flight Tests

The acoustic performance of various airframe noise reduction technologies – Adaptive Compliant Trailing Edge flap, main landing gear fairings, and gear cavity treatments – was determined, individually and in combination, using the Effective Perceived Noise Level metric. These noise measurements and calculations closely follow the Federal Aviation Administration aircraft noise certification standards, specifically for the approach noise measurement point. The flyover data correspond to pole-mounted, single-microphone measurements obtained during a series of flight tests, conducted under the NASA Flight Demonstrations and Capabilities project, that evaluated flap and landing gear noise reduction technologies. To minimize contributions from the propulsion system, the aircraft was flown along the approach path with engine thrust set at ground idle. Although contamination from engine, background, and secondary airframe noise sources partially masked the true performance of the tested technologies, the resulting acoustic data clearly showed substantial noise reductions relative to baseline levels. The acoustic benefits measured by the single microphones are consistent with previously reported trends in acoustic levels obtained from phased microphone array data.

Ravetta, Patricio A.↗

NASA NTRSDate not supplied

Phased Array Characterization of Slat Noise Radiation from a High-Lift Common Research Model

A test campaign was conducted in the open-jet test section of the NASA Langley 14- by 22-Foot Subsonic Tunnel on a 10%-scale, semispan version of a High-Lift Common Research Model (CRM-HL) incorporating a leading-edge slat, trailing-edge flap and removable high-fidelity main landing gear. Far field acoustic measurements were obtained on baseline and acoustically treated model configurations using a traversing 97-microphone phased array that viewed the pressure side of the airframe. A modified version of the DAMAS deconvolution method incorporating corrections for shear layer acoustic wave decorrelation was employed to determine the locations and strengths of relevant noise sources along the span of the slat and in the vicinity of the flap edges and landing gear. The main goal of the test campaign was to use the array data to evaluate the effectiveness of various slat noise reduction concepts. It was found that slat-gap fillers produced significant broadband noise reduction for all Mach numbers and airfoil angles of attack that were investigated. Mach number scaling revealed an approximate velocity to the sixth power relationship for the slat noise at higher frequencies. Directivity measurements obtained from integration of DAMAS pressure-squared values over defined geometric zones around the model showed that baseline slat noise radiation approximated a dipole as a function of polar emission angle, becoming approximately omnidirectional with the introduction of the slat-gap filler. The test campaign clearly demonstrated the noise reduction benefits that can be obtained by applying appropriate treatments to leading edge slats on commercial transport-class aircraft.

William M Humphreys, Jr.↗

NASA NTRS2019

Composites for Advanced Drive Systems, A Systems Analysis-Revolutionary Vertical Lift Technology (RVLT)

Rotorcraft propulsion systems are continually looking to improve power density; that is reducing weight and increasing power throughput. In order to advance rotorcraft propulsion system technology, NASA Glenn Research Center (NGRC) contracted Boeing Vertical Lift (Contract #NNA15AB12B, Task Order NNA16BE07T) to perform system level benefit assessments for incorporation of composite materials into rotorcraft transmission gear and shaft systems, in the rotating frame. In general, the environment inside a typical rotorcraft transmission is aggressive for typical composite materials. Design challenges in the rotating frame and related safety risks must be understood and accounted for in the design. Boeing developed a technical approach that evaluated a relatively large population of rotorcraft main transmissions. This technical approach took rotorcraft from various size classes and configurations and applied parametric weight estimating principles to assess the performance impact of composite hybrid technologies inside transmissions, in the rotating frame. Parametric weight estimates showed that composite hybrid technologies account for an average 9% weight savings over the baseline transmissions. More weight savings may be observed when accounting for quantity of transmissions in an aircraft configuration and benefits to airframe, landing gear, and fuel systems. A weight reduction of 595 lbs was calculated for NASA's Large Civil Tilt Rotor (LCTR2) by utilizing composite hybrid components inside the Prop-Rotor Transmission in the rotating frame and accounting for design changes to the airframe, landing gear, and fuel system. In order to develop composite hybrid technologies, sub-scale and full-scale testing should continue, building on the work that NGRC has begun. Design and testing efforts should focus on technical challenges, such as joint and attachment interfaces, temperature effects, inspection procedures, and fault detection. It is recommended to address technical challenges with targeted research and development efforts, conducted at relevant scale, prior to incorporating composite hybrid technologies within the rotating frame of helicopter transmissions.

Darmstadt, Patrick R.↗

NASA NTRS2016

Computational Evaluation of Airframe Noise Reduction Concepts at Full Scale

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.

Khorrami, Mehdi R.↗

NASA NTRS2018

Simulations of a Full-Scale Aircraft with Installed Airframe Noise Reduction Technologies

Computational results are presented for a high-fidelity, full-scale, full-span Gulfstream G-III aircraft model equipped with flap and main landing gear (MLG) noise reduction technologies. The simulations, which were conducted in support of a NASA airframe noise flight test campaign of the same technologies, use the lattice Boltzmann solver PowerFLOW® to capture time-accurate flow data with sound propagation to the far field accomplished using a Ffowcs-Williams and Hawkings (FWH) acoustic analogy approach. The aerodynamic and aeroacoustic behavior of the aircraft were investigated in the approach configuration with combinations of flap and landing gear deployments. The simulated flap concept is an Adaptive Compliant Trailing Edge (ACTE) flap that replaces the Fowler flap system on the G-III aircraft. The simulated MLG noise reduction concept is comprised of porous fairings and a collection of other smaller fairings fitted around the flow-facing components. Using the Fowler flap results as a reference, comparisons are presented on the noise reduction effectiveness of the ACTE flap system. Investigations were made on the effects of using the porous fairings and ACTE flap as noise reduction concepts in tandem. The ACTE flap was found to reduce the total airframe noise level at all flap deflection angles when compared to the Fowler flap equipped model. As anticipated, a reduction in aerodynamic performance was also found when the ACTE flap system was used. The MLG fairings were shown to further reduce the total airframe noise level of the G-III.

Ferris, Ryan J.↗

NASA NTRS2018

Flight-Test Evaluation of Airframe Noise Mitigation Technologies

A series of flight tests targeting airframe noise reduction was planned and executed under the NASA Flight Demonstrations and Capabilities project. The objectives of the tests were two-fold: to evaluate the aeroacoustic performance of several noise reduction technologies in a relevant environment and to generate a comprehensive database for advancing the state of the art in simulation-based airframe noise prediction methodologies. These technologies – an Adaptive Compliant Trailing Edge flap, main landing gear fairings, and gear cavity treatments – were integrated on a NASA Gulfstream G-III aircraft to determine their effectiveness, both on a component-level (individually) and a system-level (combined) basis. With the aircraft flying an approach pattern and the engines set at ground idle, extensive acoustic measurements were acquired using a phased microphone array system. Detailed analyses of the gathered acoustic data clearly demonstrate that significant noise reduction was achieved for the flap and main landing gear components.

Khorrami, Mehdi R.↗