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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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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Development of rotorcraft interior noise control concepts. Phase 2: Full scale testing, revision 1

The phase 2 effort consisted of a series of ground and flight test measurements to obtain data for validation of the Statistical Energy Analysis (SEA) model. Included in the gound tests were various transfer function measurements between vibratory and acoustic subsystems, vibration and acoustic decay rate measurements, and coherent source measurements. The bulk of these, the vibration transfer functions, were used for SEA model validation, while the others provided information for characterization of damping and reverberation time of the subsystems. The flight test program included measurements of cabin and cockpit sound pressure level, frame and panel vibration level, and vibration levels at the main transmission attachment locations. Comparisons between measured and predicted subsystem excitation levels from both ground and flight testing were evaluated. The ground test data show good correlation with predictions of vibration levels throughout the cabin overhead for all excitations. The flight test results also indicate excellent correlation of inflight sound pressure measurements to sound pressure levels predicted by the SEA model, where the average aircraft speech interference level is predicted within 0.2 dB.

Yoerkie, C. A.↗
NASA NTRS1938

Flight and Wind-tunnel Tests of an XBM-1 Dive Bomber

Results are given of pressure-distribution measurements made in flight over the right wing cellule and the right half of the horizontal tail surfaces of a dive-bombing biplane. Simultaneous measurements were also taken of the air speed, control-surface positions, control forces, and normal accelerations during various abrupt maneuvers in vertical plane. These maneuvers consisted of push-downs and pull-ups from level flight, dives and dive pull-ups from inverted flight. Besides the pressure measurements, flight tests were made to obtain (1) wing-fabric deflections during dives and (2) variation of the minimum drag coefficient with Reynolds Number. Supplementary tests were also done in the full-scale wind tunnel to obtain the characteristics of the airplane under various propeller conditions and with various tail settings. The results indicate that: (1) by increasing the fabric deflection between pressure ribs, the span load distribution was considerably modified near the center and the wing moment relations were changed; and (2) the minimum drag was less for the idling propeller than for the propeller locked in a vertical position. The value of C(sub D sub min) was equal to K(Reynolds Number)(exp -0.03) for a range from 2,800,000 to 13,100,000.

Donely, Philip↗
NASA NTRS1983

Aircraft surface coatings

A series of studies in which films and liquid spray-on materials were evaluated in the laboratory for transport aircraft external surface coatings are summarized. Elastomeric polyurethanes were found to best meet requirements. Two commercially available products, CAAPCO B-274 and Chemglaze M313, were subjected to further laboratory testing, airline service evaluations, and drag-measurement flight tests. It was found that these coatings were compatible with the severe operating environment of airlines and that coatings reduced airplane drag. An economic analysis indicated significant dollar benefits to airlines from application of the coatings.

Source record↗
NASA NTRS1954

Studies of the Lateral-Directional Flying Qualities of a Tandem Helicopter in Forward Flight

An investigation of the lateral-directional flying qualities of a tandem-rotor helicopter in forward flight was undertaken to determine desirable goals for helicopter lateral-directional flying qualities and possible methods of achieving these goals in the tandem-rotor helicopter. Comparison between directional stability as measured in flight and rotor-off model tests in a wind tunnel shows qualitative agreement and, hence, indicates such wind-tunnel test, despite the absence of the rotors, to be one effective method of studying means of improving the directional stability of the tandem helicopter. Flight-test measurements of turns and oscillations, in conjunction with analytical studies, suggest possible practical methods of achieving the goals of satisfactory turn and oscillatory characteristics in the tandem helicopter.

Amer, Kenneth B↗
NASA NTRS1976

Flight loads measurements obtained from calibrated strain-gage bridges mounted externally on the skin of a low-aspect-ratio wing

Flight-test measurements of wingloads (shear, bending moment, and torque) were obtained by means of strain-gage bridges mounted on the exterior surface of a low-aspect-ratio, thin, swept wing which had a structural skin, full-depth honeycomb core, sandwich construction. Details concerning the strain-gage bridges, the calibration procedures used, and the flight-test results are presented along with some pressure measurements and theoretical calculations for comparison purposes.

Eckstrom, C. V.↗
NASA NTRS1994

Microburst vertical wind estimation from horizontal wind measurements

The vertical wind or downdraft component of a microburst-generated wind shear can significantly degrade airplane performance. Doppler radar and lidar are two sensor technologies being tested to provide flight crews with early warning of the presence of hazardous wind shear. An inherent limitation of Doppler-based sensors is the inability to measure velocities perpendicular to the line of sight, which results in an underestimate of the total wind shear hazard. One solution to the line-of-sight limitation is to use a vertical wind model to estimate the vertical component from the horizontal wind measurement. The objective of this study was to assess the ability of simple vertical wind models to improve the hazard prediction capability of an airborne Doppler sensor in a realistic microburst environment. Both simulation and flight test measurements were used to test the vertical wind models. The results indicate that in the altitude region of interest (at or below 300 m), the simple vertical wind models improved the hazard estimate. The radar simulation study showed that the magnitude of the performance improvement was altitude dependent. The altitude of maximum performance improvement occurred at about 300 m.

Vicroy, Dan D.↗
NASA NTRS1996

The X-31A quasi-tailless flight test results

A quasi-tailless flight investigation was launched using the X-31A enhanced fighter maneuverability airplane. In-flight simulations were used to assess the effect of partial to total vertical tail removal. The rudder control surface was used to cancel the stabilizing effects of the vertical tail, and yaw thrust vector commands were used to restabilize and control the airplane. The quasi-tailless mode was flown supersonically with gentle maneuvering and subsonically in precision approaches and ground attack profiles. Pilot ratings and a full set of flight test measurements were recorded. This report describes the results obtained and emphasizes the lessons learned from the X-31A flight test experiment. Sensor-related issues and their importance to a quasi-tailless simulation and to ultimately controlling a directionally unstable vehicle are assessed. The X-31A quasi-tailless flight test experiment showed that tailless and reduced tail fighter aircraft are definitely feasible. When the capability is designed into the airplane from the beginning, the benefits have the potential to outweigh the added complexity required.

Bosworth, John T.↗
NASA NTRS1982

Comparison of Flight Measured, Predicted and Wind Tunnel Measured Winglet Characteristics on a KC-135 Aircraft

One of the objectives of the KC-135 Winglet Flight Research and Demonstration Program was to obtain experimental flight test data to verify the theoretical and wind tunnel winglet aerodynamic performance prediction methods. Good agreement between analytic, wind tunnel and flight test performance was obtained when the known differences between the tests and analyses were accounted for. The flight test measured fuel mileage improvements for a 0.78 Mach number was 3.1 percent at 8 x 10(5) pounds W/delta and 5.5 percent at 1.05 x 10(6) pounds W/delta. Correcting the flight measured data for surface pressure differences between wind tunnel and flight resulted in a fuel mileage improvement of 4.4 percent at 8 x 10(5) pounds W/delta and 7.2 percent at 1.05 x 10(6) pounds W/delta. The performance improvement obtained was within the wind tunnel test data obtained from two different wind tunnel models. The buffet boundary data obtained for the baseline configuration was in good agreement with previous established data. Buffet data for the 15 deg cant/-4 deg incidence configuration showed a slight improvement, while the 15 deg cant/-2 deg incidence and 0 deg cant/-4 deg incidence data showed a slight deterioration.

Dodson, R. O., Jr.↗
NASA NTRS1947

Comparison of Wind-Tunnel Predictions with Flight Measurements of the Longitudinal-Stability and -Control Characteristics of a Douglas BTD-1 Airplane

Low Mach number longitudinal-stability and control characteristics as predicted by use of wind tunnel data from a powered 3/16-scale model are compared with flight test measurements of a Navy BTD-1 airplane. The accuracy of the wind tunnel data and the discrepancies involved in attempting to correlate with flight data are discussed and analyzed. The comparison showed that wind tunnel predictions were, in general, in good agreement with flight test data. The predicted values were for the most part sufficiently accurate to show the satisfactory and unsatisfactory characteristics in the preliminary design stage and to indicate possible methods of improvement. The discrepancies which did occur were attributed principally to physical dissimilarities between model and airplane and the instability to determine accurately the flight power conditions. The effect of Mach number was considered negligible since the maximum flight test value was about 0.5. In order to simulate more closely the flight conditions and hence obtain more accurate data for predictions, it appears desirable to perform large-scale tests of unorthodox control surfaces such as the sealed vaned elevators with which the airplane was equipped.

Bunnell, Mort V.↗
NASA NTRS1935

The Influence of Tip Shape on the Wing Load Distribution as Determined by Flight Tests

Pressure measurements were made in flight on the right upper wing of an M-3 airplane. The effects of tip plan form, washout, and transverse camber were investigated with eight tip forms in unyawed conditions through the range of positive lift coefficients from zero lift to the stall. The conclusion is that the tip plan form does not influence the span distribution of the coefficients of normal force and moment. It is shown inferentially that temperature, humidity, and the aging of the wood and fabric wing structure used on the M-3 airplane have an appreciable influence on the load distribution.

Rhode, Richard V↗
NASA NTRS2009

Lessons Learned from Numerical Simulations of the F-16XL Aircraft at Flight Conditions

Nine groups participating in the Cranked Arrow Wing Aerodynamics Project International (CAWAPI) project have contributed steady and unsteady viscous simulations of a full-scale, semi-span model of the F-16XL aircraft. Three different categories of flight Reynolds/Mach number combinations were computed and compared with flight-test measurements for the purpose of code validation and improved understanding of the flight physics. Steady-state simulations are done with several turbulence models of different complexity with no topology information required and which overcome Boussinesq-assumption problems in vortical flows. Detached-eddy simulation (DES) and its successor delayed detached-eddy simulation (DDES) have been used to compute the time accurate flow development. Common structured and unstructured grids as well as individually-adapted unstructured grids were used. Although discrepancies are observed in the comparisons, overall reasonable agreement is demonstrated for surface pressure distribution, local skin friction and boundary velocity profiles at subsonic speeds. The physical modeling, steady or unsteady, and the grid resolution both contribute to the discrepancies observed in the comparisons with flight data, but at this time it cannot be determined how much each part contributes to the whole. Overall it can be said that the technology readiness of CFD-simulation technology for the study of vehicle performance has matured since 2001 such that it can be used today with a reasonable level of confidence for complex configurations.

Rizzi, Arthur↗
NASA NTRS2009

What was Learned from Numerical Simulations of F-16XL (CAWAPI) at Flight Conditions

Nine groups participating in the CAWAPI project have contributed steady and unsteady viscous simulations of a full-scale, semi-span model of the F-16XL aircraft. Three different categories of flight Reynolds/Mach number combinations were computed and compared with flight-test measurements for the purpose of code validation and improved understanding of the flight physics. Steady-state simulations are done with several turbulence models of different complexity with no topology information required and which overcome Boussinesq-assumption problems in vortical flows. Detached-eddy simulation (DES) and its successor delayed detached-eddy simulation (DDES) have been used to compute the time accurate flow development. Common structured and unstructured grids as well as individually-adapted unstructured grids were used. Although discrepancies are observed in the comparisons, overall reasonable agreement is demonstrated for surface pressure distribution, local skin friction and boundary velocity profiles at subsonic speeds. The physical modeling, be it steady or unsteady flow, and the grid resolution both contribute to the discrepancies observed in the comparisons with flight data, but at this time it cannot be determined how much each part contributes to the whole. Overall it can be said that the technology readiness of CFD-simulation technology for the study of vehicle performance has matured since 2001 such that it can be used today with a reasonable level of confidence for complex configurations.

Rizzi, Arthur↗
NASA NTRS2018

Challenges and Opportunities for Subsonic Transport X-Plane Acoustic Flight Research

Aircraft system noise aspects of experimental aircraft acoustic flight research are analyzed. Experimental aircraft are seen as a key development step toward the introduction of a full scale low noise subsonic transport in the future, especially when considering an unconventional aircraft configuration integrating a range of advanced noise reduction technologies. Possible design scenarios for an experimental aircraft are considered where the scale of the experimental aircraft relative to the future, full scale aircraft is likely a major cost driver. Aircraft system noise predictions are presented for a NASA modeled Mid- Fuselage Nacelle subsonic transport concept. The predictions are made for the total airframe system noise at 100, 50, 25, and 12.5% scale of the full scale, future version of the concept, both without and then with a set of noise reduction technologies. The noise reduction technologies include the dual use fairing of the Krueger flap, the continuous mold line for the trailing edge high lift flap, and the pod gear concept for the main gear. The predictions are treated as simulations of flight test measurements of an experimental aircraft that are then processed to full scale as flight data would be. The analysis shows that the combined impact of frequency shift, atmospheric absorption, and background noise cutoff is to establish a realistic upper limit on useful frequency from the experimental aircraft noise. The implications for instrumentation requirements are also noted for high frequency, as well as for the challenge of identifying sources that are reduced significantly by the proposed noise reduction technologies. For the experimental acoustic flight research to be most useful for the objectives of improving the prediction of the future full scale aircraft, it is indicated that the scale should be above 75%. As the demonstrator scale approaches 50%, the limitations become more severe for direct impact to the prediction of the full scale future concept.

Thomas, Russell H.↗
NASA NTRS1992

Airborne in situ computation of the wind shear hazard index

An algorithm for airborne in situ computation of the wind shear hazard index (F-factor) was developed and evaluated in simulation and verified in flight. The algorithm was implemented on NASA's B-737-100 airplane, and tested under severe maneuvering, nonhazardous wind conditions, and normal takeoffs and landings. The airplane was flown through actual microburst conditions in Orlando, FL, where the algorithm produced wind shear measurements which were confirmed by an independent, ground-based radar measurement. Flight test results indicated that the in situ F-factor algorithm correctly measured the effect of the wind environment on the airplane's performance, and produced no nuisance alerts.

Oseguera, Rosa M.↗
NASA NTRS1999

Measurements of the Basic SR-71 Airplane Near-Field Signature

Airplane design studies have developed configuration concepts that may produce lower sonic boom annoyance levels. Since lower noise designs differ significantly from other HSCT designs, it is necessary to accurately assess their potential before HSCT final configuration decisions are made. Flight tests to demonstrate lower noise design capability by modifying an existing airframe have been proposed for the Mach 3 SR-71 reconnaissance airplane. To support the modified SR-71 proposal, baseline in-flight measurements were made of the unmodified aircraft. These measurements of SR-71 near-field sonic boom signatures were obtained by an F-16XL probe airplane at flightpath separation distances ranging from approximately 740 to 40 ft. This paper discusses the methods used to gather and analyze the flight data, and makes comparisons of these flight data with CFD results from Douglas Aircraft Corporation and NASA Langley Research Center. The CFD solutions were obtained for the near-field flow about the SR-71, and then propagated to the flight test measurement location using the program MDBOOM.

Haering, Edward A., Jr.↗
NASA NTRSDate not supplied

Fluid-Structure Interaction Simulations Of Supersonic Parachute Inflation: Model Sensitivities

Fluid-structure interaction simulations have the potential to accelerate the certification process of parachute systems for interplanetary robotic exploration missions while helping to mitigate risks by covering a wider range of scenarios than can be flight tested. The Launch, Ascent, and Vehicle Aerodynamics team is working toward actualizing this potential by further developing the capability to perform such fluid-structure interaction simulations and validating it with the best supersonic parachute flight test data available. We perform several simulations of the Advanced Supersonic Parachute Inflation Research Experiments’ third flight test (SR03) where we independently vary several parameters to determine their sensitivity on the predicted drag. We investigate sensitivity of the drag to the added mass of the confluence fitting, to the effective porosity, to how the gore seams are modeled, to viscous effects, and to deceleration. Modeling the added mass of the confluence fitting has virtually no impact on the drag, but is worthwhile to include to better match the overall system’s mass, which is important for the simulations with deceleration. Parachute drag is only marginally sensitive to porosity and viscous effects. Maximum parachute drag is most sensitive to how the gore seams are modeled, causing a nearly 20% drop when they are modeled as stiffer radials, and to deceleration, causing an additional 10% reduction. Results show improved agreement with flight test measurements when the FSI model is closest to the as-built configuration and physics experienced in flight: with the confluence fitting, viscous effects, the gore seams modeled as stiff radials, and including deceleration.

ESM↗
NASA NTRS1997

XV-15 Structural-Acoustic Data

Tiltrotor aircraft are a potentially viable means of intercity travel. The tiltrotor is able to transport passengers relatively quickly from the center of a city to destinations within a 300-mile radius. For such vehicles to be commercially viable, the interior noise and vibration levels must be acceptable to the passengers. A review of the literature revealed very little structural-acoustic data related to the tiltrotor. For this reason, structural-acoustic measurements were taken aboard an XV-15 tiltrotor. The six flight conditions included five in level flight, nominally 140-220 knots, for airplane mode (nacelle at 0 degrees) and one out-of-ground-effect (OGE) hover (nacelle at 90 degrees). The flight test measurements included nine exterior surface pressures, five structural accelerations, and two interior pressures. These sensors were located near the tip path plane on the port side of the aircraft. One minute of data was acquired at each condition. The data is presented as time histories, autospectra, coherence functions, and cross-spectra. In general, for level flight, the measured data showed very little effect of forward flight speed except to change the amplitude of the response; however, the character of the response was found to be dependent on spatial location. In contrast, in the hover mode the spatial location had very little effect on the character of the response. Additionally, the report highlights: the coherence between the transducer data and the rotor tach signal; and transfer function calculations between the exterior pressures.

Lyle, Karen H.↗
NASA NTRS2015

Trailing Vortex-Induced Loads During Close Encounters in Cruise

The trailing vortex induced aerodynamic loads on a Falcon 20G business jet flying in the wake of a DC-8 are predicted to provide a preflight estimate of safe trail distances during flight test measurements in the wake. Static and dynamic loads on the airframe flying in the near wake are shown at a matrix of locations, and the dynamic motion of the Falcon 20G during traverses of the DC-8 primary trailing vortex is simulated. Safe trailing distances for the test flights are determined, and optimum vortex traverse schemes are identified to moderate the motion of the trailing aircraft during close encounters with the vortex wake.

Mendenhall, Michael R.↗