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Russell H. Thomas – One of the best experts on this subject based on the ideXlab platform.

  • Open Rotor Aeroacoustic Installation Effects for Conventional and Unconventional Airframes
    , 2013
    Co-Authors: Michael Czech, Russell H. Thomas
    Abstract:

    As extensive experimental campaign was performed to study the aeroacoustic installation effects of an open rotor with respect to both a conventional tube and wing type Airframe and an unconventional hybrid wing body Airframe. The open rotor rig had two counter rotating rows of blades each with eight blades of a design originally flight tested in the 1980s. The aeroacoustic installation effects measured in an aeroacoustic wind tunnel included those from flow effects due to inflow distortion or wake interaction and acoustic propagation effects such as shielding and reflection. The objective of the test campaign was to quantify the installation effects for a wide range of parameters and configurations derived from the two Airframe types. For the conventional Airframe, the open rotor was positioned in increments in front of and then over the main wing and then in positions representative of tail mounted aircraft with a conventional tail, a T-tail and a U-tail. The interaction of the wake of the open rotor as well as acoustic scattering results in an increase of about 10 dB when the rotor is positioned in front of the main wing. When positioned over the main wing a substantial amount of noise reduction is obtained and this is also observed for tail-mounted installations with a large U-tail. For the hybrid wing body Airframe, the open rotor was positioned over the Airframe along the centerline as well as off-center representing a twin engine location. A primary result was the documentation of the noise reduction from shielding as a function of the location of the open rotor upstream of the trailing edge of the hybrid wing body. The effects from vertical surfaces and elevon deflection were also measured. Acoustic lining was specially designed and inserted flush with the elevon and Airframe surface, the result was an additional reduction in open rotor noise propagating to the far field microphones. Even with the older blade design used, the experiment provided quantification of the aeroacoustic installation effects for a wide range of open rotor and Airframe configurations and can be used with data processing methods to evaluate the aeroacoustic installation effects for open rotors with modern blade designs.

  • NASA’s propulsion Airframe aeroacoustics research
    The Journal of the Acoustical Society of America, 2004
    Co-Authors: Russell H. Thomas
    Abstract:

    The integration of propulsion and Airframe is a fundamental consideration in the design of an aircraft system. Many considerations influence the integration, such as structural, aerodynamic, and maintenance factors. In the future, a focus on the aerodynamic and acoustic interaction effects of installation, propulsion Airframe aeroacoustics will become more important as noise reduction targets become more difficult to achieve. In addition to continued fundamental component reduction efforts, a system level approach that includes propulsion Airframe aeroacoustics will be required in order to achieve the 20‐dB noise reductions envisioned by the aggressive NASA goals. This emphasis on the aeroacoustics of propulsion Airframe integration is a new part of NASA’s ongoing acoustics research. The presentation will review current efforts and highlight technical challenges and approaches.

  • Aeroacoustics of Propulsion Airframe Integration: Overview of NASA’s Research
    , 2003
    Co-Authors: Russell H. Thomas
    Abstract:

    The integration of propulsion and Airframe is fundamental to the design of an aircraft system. Many considerations influence the integration, such as structural, aerodynamic, and maintenance factors. In regard to the acoustics of an aircraft, the integration can have significant effects on the net radiated noise. Whether an engine is mounted above a wing or below can have a significant effect on noise that reaches communities below because of shielding or reflection of engine noise. This is an obvious example of the acoustic effects of propulsion Airframe installation. Another example could be the effect of the pylon on the development of the exhaust plume and on the resulting jet noise. In addition, for effective system noise reduction the impact that installation has on noise reduction devices developed on isolated components must be understood. In the future, a focus on the aerodynamic and acoustic interaction effects of installation, propulsion Airframe aeroacoustics, will become more important as noise reduction targets become more difficult to achieve. In addition to continued fundamental component reduction efforts, a system level approach that includes propulsion Airframe aeroacoustics will be required in order to achieve the 20 dB of perceived noise reduction envisioned by the long-range NASA goals. This emphasis on the aeroacoustics of propulsion Airframe integration is a new part of NASA’s noise research. The following paper will review current efforts and highlight technical challenges and approaches.

Justin D. Littell – One of the best experts on this subject based on the ideXlab platform.

  • Large Field Digital Image Correlation Used for Full-Scale Aircraft Crash Testing: Methods and Results
    International Digital Imaging Correlation Society, 2017
    Co-Authors: Justin D. Littell
    Abstract:

    Since the summer of 2013, five full-scale crash tests have been conducted at NASA Langley Research Center’s (LaRC) Landing and Impact Research Facility (LandIR) on deformable Airframes for the evaluation of a variety of crashworthy concepts. Two tests were conducted on two CH-46E “Sea Knight” Airframes as part of the Transport Rotorcraft Airframe Crash Testbed (TRACT) project and three tests were conducted on three Cessna 172 General Aviation aircraft as a part of the Emergency Locator Transmitter Survivability and Reliability (ELTSAR) project. Full field digital image correlation (DIC) data was obtained as a part of each aircraft’s experimental suite, thus giving insight into the crash severity and Airframe deformation which occurred for each test [1].

  • Experimental Photogrammetric Techniques Used on Five Full-Scale Aircraft Crash Tests
    , 2016
    Co-Authors: Justin D. Littell
    Abstract:

    Between 2013 and 2015, full-scale crash tests were conducted on five aircraft at the Landing and Impact Research Facility (LandIR) at NASA Langley Research Center (LaRC). Two tests were conducted on CH-46E Airframes as part of the Transport Rotorcraft Airframe Crash Testbed (TRACT) project, and three tests were conduced on Cessna 172 aircraft as part of the Emergency Locator Transmitter Survivability and Reliability (ELTSAR) project. Each test served to evaluate a variety of crashworthy systems including: seats, occupants, restraints, composite energy absorbing structures, and Emergency Locator Transmitters. As part of each test, the aircraft were outfitted with a variety of internal and external cameras that were focused on unique aspects of the crash event. A subset of three camera was solely used in the acquisition of photogrammetric test data. Examples of this data range from simple two-dimensional marker tracking for the determination of aircraft impact conditions to entire full-scale Airframe deformation to markerless tracking of Anthropomorphic Test Devices (ATDs, a.k.a. crash test dummies) during the crash event. This report describes and discusses the techniques used and implications resulting from the photogrammetric data acquired from each of the five tests.

David K. Schmidt – One of the best experts on this subject based on the ideXlab platform.

  • Analysis of Airframe and engine control interactions and integrated flight/propulsion control
    Journal of Guidance Control and Dynamics, 1992
    Co-Authors: John D. Schierman, David K. Schmidt
    Abstract:

    A framework is presented for the analysis of dynamic cross-coupling between Airframe and engine control systems. This approach is developed for assessing the significance of Airframe/engi ne interactions with regard to system stability, performance, and critical frequency ranges where interactions are especially problematic. The stability robustness against Airframe/engine interactions are of particular interest, and a robustness analysis approach is developed and presented. The difference between systems exhibiting two-directional vs one-directional coupling is also discussed. Two control configurations of a vehicle previously considered in several integrated flight/propulsion control studies are then evaluated using the technique, and it is shown that the baseline configuration reflects little significant Airframe/engine interactions. Consequently, classical decentralized Airframe and engine control laws appear to be quite adequate. However, analysis of the other system configuration shows significant performance degradation in the engine loop because of Airframe/engi ne coupling.

  • Analysis of Airframe/engine interactions in integrated flight and propulsion control
    Navigation and Control Conference, 1991
    Co-Authors: John D. Schierman, David K. Schmidt
    Abstract:

    An analysis framework for the assessment of dynamic cross-coupling between Airframe and engine systems from the perspective of integrated flight/propulsion control is presented. This analysis involves to determining the significance of the interactions with respect to deterioration in stability robustness and performance, as well as critical frequency ranges where problems may occur due to these interactions. The analysis illustrated here investigates both the Airframe‘s effects on the engine control loops and the engine’s effects on the Airframe control loops in two case studies. The second case study involves a multi-input/multi-output analysis of the Airframe. Sensitivity studies are performed on critical interactions to examine the degradations in the system’s stability robustness and performance. Magnitudes of the interactions required to cause instabilities, as well as the frequencies at which the instabilities occur are recorded. Finally, the analysis framework is expanded to include control laws which contain cross-feeds between the Airframe and engine systems.

Werner Dobrzynski – One of the best experts on this subject based on the ideXlab platform.

  • almost 40 years of Airframe noise research what did we achieve
    Journal of Aircraft, 2010
    Co-Authors: Werner Dobrzynski
    Abstract:

    With the advent of low noise high bypass ratio turbofan engines Airframe noise gained significant importance with respect to the overall aircraft noise impact around airports. Already around 1970 Airframe noise, originating from flow around the landing gears and high-lift devices, was recognized as a potential “lower aircraft noise barrier” at approach and landing. Since then, the outcome of extensive acoustic flight tests and aeroacoustic wind tunnel experiments enabled a detailed description and ranking of the major Airframe noise sources and the development of noise reduction means. In the last decade advances in numerical and experimental tools led to a better understanding of complex noise source mechanisms. Efficient noise reduction technologies were developed for landing gears while the benefits of high-lift noise reduction means were often compensated by a simultaneous degradation in aerodynamic performance. The focus of this paper is not on the historical sequence of Airframe noise research but rather aims to provide a concise survey of the achievements in Airframe noise source description and reduction over the last 40 years worldwide. Due to the vast amount of work focused on a variety of Airframe noise problems, this review can only provide examples but does not claim to be complete.

  • research at dlr towards Airframe noise prediction and reduction
    Aerospace Science and Technology, 2008
    Co-Authors: Werner Dobrzynski, Roland Ewert, Michael Pottpollenske, Michaela Herr, Jan Werner Delfs
    Abstract:

    Abstract In the final approach phase Airframe noise represents the ultimate aircraft noise barrier for future aircraft when equipped with quiet UHBR engines. This paper summarizes the results achieved at DLR in the development of methods and tools for Airframe noise prediction and reduction. Numerous DLR internal, national and EC co-financed research projects were conducted to investigate the aerodynamic noise of wing high-lift devices and landing gears, which constitute the major Airframe noise contributors. Experimental noise source studies where performed on both scaled 2D generic and complete high-lift wing models and on an A320 full-scale wing section as well as on full-scale landing gears. These tests aimed at the quantification of Airframe noise levels, the identification of major aeroacoustic sources and the development of noise prediction schemes. The results from these experiments provided information on the noise generation mechanisms and radiation characteristics from slats and landing gears. Devices were developed, which promise an overall Airframe noise reduction potential of up to 5 dB, relative to Airframe noise levels of current aircraft. While such technologies already reach a high “technology readiness level” for landing gears, the development of noise reduction means for high-lift devices still remains in a research stage. For the development of low-noise high-lift devices for future aircraft by means of computational aeroacoustics, low-cost simulation codes were developed, validated and applied to a variety of 2D Airframe noise problems.

  • Airframe noise characteristics from flyover measurements and prediction
    AIAA CEAS Aeroacoustics Conference, 2006
    Co-Authors: Michael Pottpollenske, Werner Dobrzynski, Heino Buchholz, Sebastien Guerin, Gerd Saueressig, Ullrich Finke
    Abstract:

    Aircraft noise impact around airports will increase corresponding to the predicted growth in air-traffic if no measures for aircraft source noise reduction are taken or noise abatement flight procedures are developed. During the final approach phase engine noise and Airframe noise are comparable in level, the latter being governed by flow noise originating from landing gears and high lift devices. Based on the results of dedicated wind tunnel studies semi-empirical/empirical Airframe noise prediction schemes were developed for both high lift devices’ and landing gear noise to support the calculation of noise impact in the vicinity of airports. Within an ongoing German national research project on the development of noise abatement procedures, co-financed by the German Ministry of Education and Research (BMBF), flyover noise measurements were conducted on an Airbus A319 aiming at the validation of DLR’s Airframe noise prediction schemes. In order to distinguish between Airframe and engine noise sources flyovers were performed for different aircraft configurations and operational conditions.

Nasa – One of the best experts on this subject based on the ideXlab platform.

  • Propulsion Airframe Integration Overview
    , 2015
    Co-Authors: Nasa
    Abstract:

    The Propulsion Airframe Integration (PAI) Project develops advanced technologies to yield lower drag integration of the propulsion system with the Airframe. Lower drag reduces aircraft fuel burn for a given mission, and therefore contributes to the UEET Program s 15 percent CO2 emission reduction goal for large commercial jet transports. An overview of the PAI technologies and plans is given in this presentation.