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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.

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All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Aircraft integrated design and analysis: A classroom experience

AAE 451 is the capstone course required of all senior undergraduates in the School of Aeronautics and Astronautics at Purdue University. During the past year the first steps of a long evolutionary process were taken to change the content and expectations of this course. These changes are the result of the availability of advanced computational capabilities and sophisticated electronic media availability at Purdue. This presentation will describe both the long range objectives and this year's experience using the High Speed Commercial Transport design, the AIAA Long Duration Aircraft design and RPV design proposal as project objectives. The central goal of these efforts is to provide a user-friendly, computer-software-based environment to supplement traditional design course methodology. The Purdue University Computer Center (PUCC), the Engineering Computer Network (ECN) and stand-alone PC's are being used for this development. This year's accomplishments center primarily on aerodynamics software obtained from NASA/Langley and its integration into the classroom. Word processor capability for oral and written work and computer graphics were also blended into the course. A total of ten HSCT designs were generated, ranging from twin-fuselage aircraft, forward swept wing aircraft to the more traditional delta and double-delta wing aircraft. Four Long Duration Aircraft designs were submitted, together with one RPV design tailored for photographic surveillance.

Weisshaar, Terrence A.↗
NASA NTRS1989

An experimental investigation of multi-element airfoil ice accretion and resulting performance degradation

An investigation of the ice accretion pattern and performance characteristics of a multi-element airfoil was undertaken in the NASA Lewis 6- by 9-Foot Icing Research Tunnel. Several configurations of main airfoil, slat, and flaps were employed to examine the effects of ice accretion and provide further experimental information for code validation purposes. The text matrix consisted of glaze, rime, and mixed icing conditions. Airflow and icing cloud conditions were set to correspond to those typical of the operating environment anticipated for a commercial transport vehicle. Results obtained included ice profile tracings, photographs of the ice accretions, and force balance measurements obtained both during the accretion process and in a past-accretion evaluation over a range of angles of attack. The tracings and photographs indicated significant accretions on the slat leading edge, in gaps between slat or flaps and the main wing, on the flap leading-edge surfaces, and on flap lower surfaces. Force measurements indicate the possibility of severe performance degradation, especially near C sub Lmax, for both light and heavy ice accretion and performance analysis codes presently in use. The LEWICE code was used to evaluate the ice accretion shape developed during one of the rime ice tests. The actual ice shape was then evaluated, using a Navier-Strokes code, for changes in performance characteristics. These predicted results were compared to the measured results and indicate very good agreement.

Potapczuk, Mark G.↗
NASA NTRS1990

Stowable Mechanical Sound Suppressor

Stowable sound suppressor conceived for high-speed commercial transport (HSCT) engines. Suppressor is located just aft of variable nozzle of engine. During takeoff, when suppression of noise required, multisegmented system of separators rotates out of center plug across nozzle stream. Actuation accomplished by single ball-screw drive and links, similar to spokes in umbrella. With iris nozzle translated forward, circumferential row of tubes exposed. Pattern of tubes and separators form suppressor configuration. Flow stream through slots and tubes sized to takeoff area. Useful on any turbo-jet engine in which active suppression of sound required.

Thompson, Edward R.↗
NASA NTRS1987

Simulated airline service experience with laminar-flow control leading-edge systems

The first JetStar leading edge flight test was made November 30, 1983. The JetStar was flown for more than 3 years. The titanium leading edge test articles today remain in virtually the same condition as they were in on that first flight. No degradation of laminar flow performance has occurred as a result of service. The JetStar simulated airline service flights have demonstrated that effective, practical leading edge systems are available for future commercial transports. Specific conclusions based on the results of the simulated airline service test program are summarized.

Maddalon, Dal V.↗
NASA NTRS1987

The 757 NLF glove flight test results

A major concern in the application of a laminar flow wing design to commercial transports is whether laminar flow can be sustained in the presence of the noise environment due to wing mounted turbofan engines. To investigate this issue, a flight test program was conducted using the Boeing 757 flight research airplane with a portion of the wing modified to obtain natural laminar flow. The flight test had two primary objectives. The first was to measure the noise levels on the upper and lower surface of the wing for a range of flight conditions. The second was to investigate the effect of engine noise on laminar boundary layer transition. The noise field on the wing and transition location on the glove were then measured as a function of the engine power setting at a given flight condition. The transition and noise measurement on the glove show that there is no apparent effect of engine noise on the upper surface transition location. On the lower surface, the transition location moved forward 2 to 3 percent chord. A boundary layer stability analysis to the flight data showed that cross flow disturbances were the dominant cause of transition at most flight conditions.

Runyan, L. Jim↗
NASA NTRS1989

Evaluation of analysis techniques for low frequency interior noise and vibration of commercial aircraft

The application of selected analysis techniques to low frequency cabin noise associated with advanced propeller engine installations is evaluated. Three design analysis techniques were chosen for evaluation including finite element analysis, statistical energy analysis (SEA), and a power flow method using element of SEA (computer program Propeller Aircraft Interior Noise). An overview of the three procedures is provided. Data from tests of a 727 airplane (modified to accept a propeller engine) were used to compare with predictions. Comparisons of predicted and measured levels at the end of the first year's effort showed reasonable agreement leading to the conclusion that each technique had value for propeller engine noise predictions on large commercial transports. However, variations in agreement were large enough to remain cautious and to lead to recommendations for further work with each technique. Assessment of the second year's results leads to the conclusion that the selected techniques can accurately predict trends and can be useful to a designer, but that absolute level predictions remain unreliable due to complexity of the aircraft structure and low modal densities.

Landmann, A. E.↗
NASA NTRS1990

Flight crew aiding for recovery from subsystem failures

Some of the conceptual issues associated with pilot aiding systems are discussed and an implementation of one component of such an aiding system is described. It is essential that the format and content of the information the aiding system presents to the crew be compatible with the crew's mental models of the task. It is proposed that in order to cooperate effectively, both the aiding system and the flight crew should have consistent information processing models, especially at the point of interface. A general information processing strategy, developed by Rasmussen, was selected to serve as the bridge between the human and aiding system's information processes. The development and implementation of a model-based situation assessment and response generation system for commercial transport aircraft are described. The current implementation is a prototype which concentrates on engine and control surface failure situations and consequent flight emergencies. The aiding system, termed Recovery Recommendation System (RECORS), uses a causal model of the relevant subset of the flight domain to simulate the effects of these failures and to generate appropriate responses, given the current aircraft state and the constraints of the current flight phase. Since detailed information about the aircraft state may not always be available, the model represents the domain at varying levels of abstraction and uses the less detailed abstraction levels to make inferences when exact information is not available. The structure of this model is described in detail.

Hudlicka, E.↗
NASA NTRS1990

NASA airframe structural integrity program

NASA initiated a research program with the long-term objective of supporting the aerospace industry in addressing issues related to the aging of the commercial transport fleet. The program combines advanced fatigue crack growth prediction methodology with innovative nondestructive examination technology with the focus on multi-stage damage (MSD) at rivited connections. A fracture mechanics evaluation of the concept of pressure proof testing the fuselage to screen for MSD was completed. A successful laboratory demonstration of the ability of the thermal flux method to detect disbonds at rivited lap splice joints was conducted. All long-term program elements were initiated, and the plans for the methodology verification program are being coordinated with the airframe manufacturers.

Harris, Charles E.↗
NASA NTRS1990

An evaluation of the pressure proof test concept for thin sheet 2024-T3

The concept of pressure proof testing of fuselage structures with fatigue cracks to insure structural integrity was evaluated from a fracture mechanics viewpoint. A generic analytical and experimental investigation was conducted on uniaxially loaded flat panels with crack configurations and stress levels typical of longitudinal lap splice joints in commercial transport aircraft fuselages. The results revealed that the remaining fatigue life after a proof test was longer than that without the proof test because of crack growth retardation due to increased crack closure. However, based on a crack length that is slightly less than the critical value at the maximum proof test stress, the minimum assured life or proof test interval must be no more than 550 pressure cycles for a 1.33 proof factor and 1530 pressure cycles for a 1.5 proof factor to prevent in-flight failures.

Dawicke, D. S.↗
NASA NTRS1989

H(2)- and H(infinity)-design tools for linear time-invariant systems

Recent advances in optimal control have brought design techniques based on optimization of H(2) and H(infinity) norm criteria, closer to be attractive alternatives to single-loop design methods for linear time-variant systems. Significant steps forward in this technology are the deeper understanding of performance and robustness issues of these design procedures and means to perform design trade-offs. However acceptance of the technology is hindered by the lack of convenient design tools to exercise these powerful multivariable techniques, while still allowing single-loop design formulation. Presented is a unique computer tool for designing arbitrary low-order linear time-invarient controllers than encompasses both performance and robustness issues via the familiar H(2) and H(infinity) norm optimization. Application to disturbance rejection design for a commercial transport is demonstrated.

Ly, Uy-Loi↗
NASA NTRS1984

Energy Efficient Engine: Control system component performance report

An Energy Efficient Engine (E3) program was established to develop technology for improving the energy efficiency of future commercial transport aircraft engines. As part of this program, General Electric designed and tested a new engine. The design, fabrication, bench and engine testing of the Full Authority Digital Electronic Control (FADEC) system used for controlling the E3 Demonstrator Engine is described. The system design was based on many of the proven concepts and component designs used on the General Electric family of engines. One significant difference is the use of the FADEC in place of hydromechanical computation currently used.

Beitler, R. S.↗
NASA NTRS1990

Effect of detailed surface geometry on riblet drag reduction performance

A comparison is made of the effect of small changes in v-groove geometry, for several riblet films applicable for drag reduction to commercial transport aircraft, whose nominal v-groove dimension is of the order of 0.002 inch. The films were tested in a water towing-tank facility. The results obtained indicate that small riblet peak geometry variations can result in a deterioration of riblet drag-reduction efficacy of as much as 40 percent, while interriblet valley curvature was found not to be critical to riblet performance.

Walsh, Michael J.↗
NASA NTRS1991

Static Footprint Local Forces, Areas, and Aspect Ratios for Three Type 7 Aircraft Tires

The National Tire Modeling Program (NTMP) is a joint NASA/industry effort to improve the understanding of tire mechanics and develop accurate analytical design tools. This effort includes fundamental analytical and experimental research on the structural mechanics of tires. Footprint local forces, areas, and aspect ratios were measured. Local footprint forces in the vertical, lateral, and drag directions were measured with a special footprint force transducer. Measurements of the local forces in the footprint were obtained by positioning the transducer at specified locations within the footprint and externally loading the tires. Three tires were tested: (1) one representative of those used on the main landing gear of B-737 and DC-9 commercial transport airplanes, (2) a nose landing gear tire for the Space Shuttle Orbiter, and (3) a main landing gear tire for the Space Shuttle Orbiter. Data obtained for various inflation pressures and vertical loads are presented for two aircraft tires. The results are presented in graphical and tabulated forms.

Howell, William E.↗
NASA NTRS1991

Analysis and design of planar and non-planar wings for induced drag minimization

Improvements in the aerodynamic efficiency of commercial transport aircraft will reduce fuel usage with subsequent reduced cost, both monetary and environmental. To this end, the current research is aimed at reducing the overall drag of these aircraft with specific emphasis on reducing the drag generated by the lifting surfaces. The ultimate goal of this program is to create a wing design methodology which optimizes the geometry of the wing for lowest total drag within the constraints of a particular design specification. The components of drag which must be considered include profile drag, and wave drag. Profile drag is dependent upon, among other things, the airfoil section and the total wetted area. Induced drag, which is manifested as energy left in the wake by the trailing vortex system is mostly a function of wing span, but also depends on other geometric wing parameters. Wave drag of the wing, important in the transonic flight regime, is largely affected by the airfoil section, wing sweep, and so forth. The optimization problem is that of assessing the various parameters which contribute to the different components of wing drag, and determining the wing geometry which generates the best overall performance for a given aircraft mission. The primary thrust of the research effort to date was in the study of induced drag. Results from the study are presented.

Straussfogel, Dennis M.↗
NASA NTRS1990

Euler and potential computational results for selected aerodynamic configurations

A selection of CFD successes and failures is evaluated, on the basis of experimental data/CFD result correlations involving full-potential and Euler computations of the aerodynamics of four commercial transport wings and two low aspect ratio delta wings. An effort is made to ascertain optimum values for grid density and distribution, artificial dissipation, Courant-Friedrichs-Lewy number, enthalphy damping, and a multigrid scheme for each flow condition and configuration analyzed. It is demonstrated that CFD solutions can assist the experimentalist prior to a test by indicating the locations of high pressure gradients and projecting test condition limitations due to balance design limits.

Hicks, R. M.↗
NASA NTRS1990

An evaluation of the pressure proof test concept for thin sheet 2024-T3

The concept of pressure proof testing of fuselage structures with fatigue cracks to insure structural integrity was evaluated from a fracture mechanics viewpoint. A generic analytical and experimental investigation was conducted on uniaxially loaded flat panels with crack configurations and stress levels typical of longitudinal lap-splice joints in commercial transport aircraft fuselage. The results revealed that the remaining fatigue life after a proof test was longer than that without the proof test because of crack growth retardation due to increased crack closure. However, based on a crack length that is slightly less than the critical value at the maximum proof test stress, the minimum assured life or proof test interval must be no more than 550 pressure cycles for a 1.33 proof factor and 1530 pressure cycles for a 1.5 proof factor to prevent in-flight failures.

Dawicke, D. S.↗
NASA NTRS1990

Design and validation of advanced transonic wings using CFD and very high Reynolds number wind tunnel testing

A study is presented that opens the possibility for further wing aerodynamic technology advances when the test and design environment is at a significantly higher Reynolds number than that used for previous generations of commercial transports. Early generation wings were based primarily on NACA airfoil sections integrated simply into three-dimensional designs. Recently, designs have been developed with a major influence from CFD and have depended less on iterative wind tunnel testing. It is shown that, coupled with improvements in CFD wing modeling and advances in test techniques, additional improvements in wing technology can be realized at significantly higher Reynolds numbers.

Goldhammer, Mark I.↗
NASA NTRS1990

Considerations for the retrofit of data link

Human factors issues related to the retrofit of data link in commercial transport aircraft are discussed. Topics that must be considered for data link implementation include, the loss of the party line, (i.e., the availability to all aircraft of information transmitted on a common voice frequency), and the scheduling of information to the flight crew. This paper focuses primarily on the human factors issues related to retrofit of Mode S. Retrofits is a difficult task because panel space accessible to flight crew members is limited. As with all cockpit equipment, data link implementation will have to comply with Federal Aviation Regulation 25.1523, which requires the manufacturer to address the conspicuity and ease of use of the data link device, and to assess the impact on crew workload. Operational sequence diagrams are provided to illustrate a methodology that can be used to decompose the flight crew body channel utilization of candidate avionics configurations in order to optimize the pilot-vehicle interface.

Corwin, William H.↗