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Technical Paper

Acoustic Test Facility Capabilities at Gulfstream Aerospace

2011-05-17
2011-01-1647
Gulfstream Aerospace Corporation (GAC) owns and operates an Acoustic Test Facility (ATF) in Savannah, GA. The ATF consists of a Reverberation Chamber, Hemi-Anechoic Chamber, and a Control Room. Types of testing conducted in the ATF include Transmission Loss, Sound Power, and Vibration testing. In addition to accommodating typical types of acoustic testing, the ATF has some unique capabilities. The ATF can be used to conduct testing at cold temperatures representative of up to 45,000 ft flight altitude, while simultaneously taking Transmission Loss measurements of the chilled test sample. Additionally, the ATF has the capability of conducting Transmission Loss testing of a full mockup of the aircraft sidewall, including a section of fuselage, all the thermal/acoustic materials up to and including the interior decorative panel. A sound source capable of very high amplitudes at high frequencies is required to obtain good measurements from testing multiple wall systems such as this.
Technical Paper

Design of a Quiet Inlet for a 6×6 Boundary Layer Flow Duct

2011-05-17
2011-01-1617
The turbulent boundary layer (TBL) that forms on the outer skin of the aircraft in flight is a significant source of interior noise. However, the existing quiet test facilities capable of measuring the TBL wall pressure fluctuations tend to be at low Mach numbers. The objective of this study was to develop a new inlet for an existing six inch square (or 6×6) flow duct that would be adequately free from facility noise to study the TBL wall pressure fluctuations at higher, subsonic Mach numbers. First, the existing flow duct setup was used to measure the TBL wall pressure fluctuations. Then the modified inlet was successfully used to make similar measurements up to Mach number of 0.6. These measurements will be used in the future to validate wall pressure spectrum models for interior noise analysis programs such as statistical energy analysis (SEA) and dynamic energy analysis (DEA).
Technical Paper

Improving SEA Predictions with Experimental Data

2011-05-17
2011-01-1701
Statistical Energy Analysis (SEA) has been used widely by industry and academia for more than 20 years to predict the mid-to-high frequency range behavior of complex acoustic systems. At Gulfstream Aerospace Corporation (GAC), SEA models have been developed to predict the interior cabin noise levels of completed Gulfstream aircraft. These models are also used for acoustic evaluations of design changes prior to implementation as well as a diagnostic tool for investigating noise and vibration issues. Throughout the development of the SEA models, extensive experimental testing in GAC's Acoustic Test Facility (ATF) was conducted on numerous aircraft components represented in the models. This paper demonstrates the importance of using experimental data to improve the accuracy of the SEA predictions by accurately adjusting the material properties and acoustic parameters of the SEA model to better match the ATF experimental data.
Technical Paper

Design of Rotorcraft Gearbox Foundation for Reduced Vibration and Increased Crashworthiness Characteristics

2011-05-17
2011-01-1704
Vehicle design is a complex process requiring interactions and exchange of information among multiple disciplines such as fatigue, strength, noise, safety, etc. Simulation models are employed for assessing and potentially improving a vehicle's performance in individual technical areas. Challenges arise when designing a vehicle for improving mutually competing objectives, satisfying constraints from multiple engineering disciplines, and determining a single set of values for the vehicle's characteristics. It is of interest to engage simulation models from the various engineering disciplines in an organized and coordinated manner for determining a design configuration that provides the best possible performance in all disciplines. The multi-discipline design process becomes streamlined when the simulation methods integrate well with finite element or computer aided design models.
Technical Paper

Design and Conduct of Precision Planetary Gear Vibration Experiments

2009-05-19
2009-01-2071
Abstract Despite a large body of analytical work characterizing the dynamic motion of planetary gears, supporting experimental data is limited. Experimental results are needed to support computer modeling and offer practical optimization guidelines to gear designers. This paper presents the design and implementation of a test facility and precision test fixtures for accurate measurement of planetary gear vibration at operating conditions. Acceleration measurements are made on all planetary bodies under controlled torque/speed conditions. Custom, high-precision test fixtures accommodate instrumentation, ensure accurate alignment, help isolate gear dynamics, and allow for variability in future testing. Results are compared with finite element and lumped parameter models.
Technical Paper

Development of a Large-Scale Microphone Array for Aircraft Jet Plume Noise Source Characterization

2011-05-17
2011-01-1733
Military jet aircraft expose both ground maintenance personnel and the community to high levels of noise. The U.S. Department of Defense is funding research to develop advanced modeling tools for noise reduction techniques and community noise exposure. A large-scale microphone array for portable near-field acoustic holography (NAH) and data acquisition system was created for this purpose. The system was designed for measuring high-amplitude jet noise from current and next-generation military aircraft to provide model refinement and benchmarking, evaluate performance of noise control devices, and predict ground maintenance personnel and community noise exposure. The acoustical instrumentation system was designed to be easy to use with scalable data processing as the primary focus. The data acquisition system allowed up to 152 channels simultaneously sampled at a rate of 96 kHz.
Technical Paper

Study of Unmanned Supersonic Aircraft Configuration

2013-10-07
2013-36-0353
The aim of this work is to present the preliminary configuration design studies for an unmanned, lightweight (less than 15 kg), supersonic research aircraft. The studies comprise the aircraft typical mission, the aerodynamic and structural arrangement, preliminary performance, as well as mass distribution. The aircraft, an Unmanned Air Vehicle, or “UAV”, is named as Pohox (“arrow” in Maxakali indian language). It is intended to be the flying test bed for a multicycle engine capable to provide thrust in subsonic, transonic and supersonic regimes. In order to provide validation of the analysis tools, flight performance characteristics of a known, high speed aircraft - North American X-15 - have been also evaluated and compared with the available flight test data. The present analysis is an important step towards the aircraft detailed definition. And the features associated with the configuration obtained are good indications of the technical feasibility of this supersonic UAV.
Technical Paper

The Development of HFE Space Claims for Combat Vehicles

2014-04-01
2014-01-0488
Abstract Discuss the basics of posturing and positioning of the full range of occupants necessary to cover the required anthropometric demographics in combat vehicles, both ground and air, since there are similarities to both and that they are both very different than the traditional automotive packaging scenarios. It is based on the Eye Reference Point and the Design Eye Point. Discuss the three Reach Zones: Primary, Secondary and Tertiary. Discuss Vision Zones and potentially ground intercepts. Discuss body clearances, both static and dynamic. Discuss the basic effects of packaging occupants with body armor with respect to SRP's and MSRP's.
Technical Paper

A Modeling of a New Store Installed in Fighter Aircraft

2005-05-16
2005-01-2384
The installation of a new store in an aircraft introduces changes to its structural dynamics characteristics. Such new configuration can present undesirable instabilities in flight. One of the most dangerous instabilities that the aircraft may experience is flutter. It is a disastrous interaction among inertial, elastic and aerodynamic forces present in the modified aircraft configuration. Therefore, this phenomenon must be prevented. In the study of flutter, the knowledge of parameters such as natural frequencies, damping and shapes of some vibration modes of the aircraft-store/suspension assembly is of crucial importance. These parameters can be obtained from ground vibration tests. This work presents a set of ground vibration test results of a new store intended to be installed in a fighter aircraft. The results are the natural frequencies, damping and mode shapes and are used to evaluate a three-degree-of-freedom model that will represent the mechanical system.
Technical Paper

Aspects of the Application of a Three Dimensional Panel Method Tool in the Design of a Light Aircraft

2005-11-22
2005-01-4161
This paper presents the computer implementation process of the Panel Method for aerodynamic analysis of three dimensional bodies with or without lift. The computer implementation consists in the creation of pre and post processing environments and a solver for the solution of the problem in external flow potential over three dimensional bodies with and without lift. For cases in which there’s no lift, a constant distribution of sources over the body (fusaleges, farings, etc.) is used, their intensities calculated in order to guarantee impermeability of the body. For cases in which there is lift, a constant distribution of sources and doublets are used on the body (wings, tails, etc.). The intensity of the sources is solved in the same manner as cases with no lift. Intensity of doublets is solved in order to satisfy the equality condition regarding pressure on the under and upper side of the trailing edge (Kutta Condition) of the body without lift.
Technical Paper

Evaluation of DOD Army Aviation Filters

2005-04-11
2005-01-1804
This program was divided into two phases: 1) comparison of DOD and API approved coalescer/separators and 2) determination if any current DOD coalescer/separators could pass API/IP 1581 5th Edition using the DOD 80-gpm and 350-gpm housings. In Phase I, seven evaluations were performed according to an approved design of experiment to compare the water removal efficiencies for the current DOD system and an equivalent American Petroleum Institute/Institute of Petroleum (API/IP) system. DOD evaluations were performed with and without water bottoms. These evaluations demonstrated that an equivalent API system out performs the current DOD system. In Phase II, ten evaluations were performed with products provided by three different manufacturers. Two manufacturers were able to pass API/IP 1581 5th Edition by improving the separator's water shedding performance.
Technical Paper

Fischer-Tropsch Fuels: Why Are They of Interest to the United States Military?

2005-04-11
2005-01-1807
Synthetic fuels can be manufactured through a process known as Fischer-Tropsch (FT) synthesis. The FT process converts synthetic gas, composed of primarily carbon monoxide and hydrogen, derived from various feedstocks (e.g. natural gas, coal, biomass or petroleum coke) into synthetic hydrocarbons. These hydrocarbons can then be further processed into various FT hydrocarbon products, including diesel fuels or jet fuels. The military has several reasons for their interest in FT fuels. This paper explores these reasons, including the emerging global FT industry, the technologies being investigated for power and propulsion systems, the environmental benefits, and the potential for enhanced strategic mobility and energy security.
Technical Paper

Study of Unmanned Supersonic Aircraft Configuration

2014-09-30
2014-36-0193
Abstract The aim of this work is to present the preliminary performance studies of the unmanned, lightweight (less than 10 kg), supersonic research aircraft. The studies comprise the typical mission for the aircraft's first supersonic version, based on the aerodynamic, thrust, and mass characteristics presented in a previous work. The aircraft, named as “Pohox”, is an Unmanned Air Vehicle, or “UAV”, and is intended to be the flying test bed for a multi cycle engine capable to provide thrust in subsonic, transonic and supersonic regimes. Different tools have been developed to perform the analysis. In the analysis, different flight paths are considered in order to provide insights in terms of fuel consumption, altitude and speed gain. Aircraft ‘excess power’ diagrams have been generated, to provide guidance for the definition of the flight paths to be analyzed. Drag dependency with Mach number is considered in the analysis.
Technical Paper

Simulation of Aircraft Engine Fan Noise Considering Different Types of Flow

2014-11-04
2014-36-0789
Abstract This article presents a comparative analysis of the influence of different types of flows over fan noise propagation and scattering within the nacelle intake of aircraft turbofan engines. The methodology for the noise simulation is explained. First, the fan noise source is modeled using a boundary condition that represents all the uncorrelated cut-on modes in the interior of the nacelle duct. Then different types of flows and flight conditions are considered in order to determine the influence of the aerodynamic phenomenon in the noise emitted by the nacelle intake. The liner attenuation is also simulated by mean of Myers boundary condition. Finally the results for far field noise are validated against numerical data obtained from the literature for hard and lined wall conditions.
Technical Paper

Weight Analysis for Low-Speed and Sun-Powered Aircraft

2014-09-30
2014-36-0508
Abstract One of the critical tasks of aircraft design is the definition of mass of aircraft's main items, and the aircraft mass distribution. Depending on the type of aircraft (e.g. commercial, general aviation, highly-maneuverable) different types of mass distribution data or trend curves are available; and in general these curves are based on the existing aircraft. But some lack of data is noticeable in terms of solar aircraft, i.e. the available information in terms of mass trends does not fulfill the needs of the designers of this type of aircraft. Considering this perspective, the main motivation of this study is to provide some information, in terms of mass trends and mass analysis for sun-powered aircraft, which could fill part of the gap, and stimulate other efforts in the same direction. Through this work, studies of mass breakdown of different examples of sun-powered aircraft are presented.
Technical Paper

Advances on Electromagnetic Numerical Codes to Solve for Radar Cross Section of Aircrafts

2014-09-30
2014-36-0390
Abstract Radar Cross Section (RCS) is the equivalent effective area of a given target intercepting a radar wave. In other words, RCS is a measure of how detectable a solid is with radar. For the past years, several electromagnetic numerical codes were used to calculate the RCS of aircrafts including the well known and commonly used Finite Element Method (FEM), Finite Difference Time Domain (FDTD) and Method of Moments (MoM). An incident planar wave is used to simulate the radar signal. Today a hybrid method known as Finite Element Boundary Integral (FEBI) solves a RCS model using the advantages of both FEM and MoM. This paper shows a series of RCS benchmarks listed in the literature comparing the results and performance of FEM, IE and FEBI. In order to show the state of the art of electromagnetic numerical codes and a more realistic analysis, several RCS of aircraft models are presented using FEBI and a true radar source.
Technical Paper

Demonstration of a Structural Damage Detection System in Fast Jet Flight Trials

2009-11-10
2009-01-3204
A structural damage detection system has been used to sense the propagation of cracks in a metallic flight test specimen on board a Hawk jet trainer. The work has demonstrated that the growth of structural cracks can be successfully and automatically detected on board a fast jet while flying unrestricted flight profiles. The experiment was part of a European collaborative defense program designed to demonstrate a number of diverse structural health monitoring technologies during flight in a military jet environment. This paper focuses on the performance of an acoustic emission detection system that was able to detect the growth of cracks in an alloy cantilever specimen bolted to a structural bulkhead in a pod suspended beneath the aircraft's left hand wing.
Journal Article

Role of Power Distribution System Tests in Final Assembly of a Military Derivative Airplane

2009-11-10
2009-01-3121
Boeing has contracts for military application of twin engine airplanes generically identified in this paper as the MX airplane. Unlike previous derivatives, the MX airplanes are produced with a streamlined manufacturing process to improve cost and schedule performance. The final assembly of each MX airplane includes a series of integration tests, called factory functional tests (FFTs), which are modified from those of typical commercial versions and verify correctness of equipment installation and basic functionalities. Two airplanes have been through the production line resulting in a number of FFT lessons learned. Addressed are the power distribution lessons learned: 1) the expanded coverage of the basic automated power-on generation system test, 2) the need for a manual wire continuity test, 3) salient features of the power distribution tests, and 4) keys to make first pass power distribution test smooth and successful.
Technical Paper

Electronic Power Distribution System Topologies

2009-11-10
2009-01-3122
This paper presents several possible topologies for Electronic Power Distribution Systems. A discussion is presented on the advantages and drawbacks of each topology. Weight savings, reliability increase, diagnostics and prognostics capabilities are discussed. Trade study results are presented to back up the discussion. The paper also presents some options on communication between the power system and the avionics systems.
Journal Article

Evaluation of the Use of a Head Worn Display (HWD) for Flight Support in the Commercial Flight Deck

2009-11-10
2009-01-3144
This study compared the performance of pilots flying a series of approach and landings under each of three conditions: using standard 737-NG flight deck displays only, using those displays with an optical head up display (HUD), and using those displays with a head worn display (HWD) depicting the same symbology as the HUD. Display condition had no effect on pilots' normal landing flight profiles or successful avoidance of a runway incursion. However, pilots reported decreased situation awareness and increased perceived workload when using the HWD as compared to the other two conditions. Pilot comments suggested that the poorer ratings for HWD were attributed to physical characteristics of the hardware and noticeable head-tracking latency. The results indicate that while the HWD technology still needs more refinement, the near-to-eye display concept is a viable alternative to a HUD.
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