-

NASA AVSCOMTechnical Memorandum 4024 Technical Report 87-B-4 -

Acoustic Measurements From aRotor Blade-Vortex InteractionNoise Experiment in theGerman-Dutch Wind Tunnel (DNW)

R. M. Martin J. W. Elliott

Langley Research Center Aerostructures DirectorateHampton, Virginia USAAR TA-A VSCOM

Langley Research CenterW. R. Splettstoesser Hampton, Virginia

Deutsche Forschungs- andVersuchsanstalt far K.-J. SchultzLuft- and Raumfahrt Deutsche Forschungs- undBraunschweig, West Germany Versuchsanstalt far

Luft- und Raumfahrt

Braunschweig, West Germany

NASANational Aeronauticsand Space Administration

Scientific and TechnicalInformation Division

1988 WIN~

Contents

Abstract 1

Introduction.................. . . ..... . . .. . .. .. .. .. .. .. ...

Symbols.................. .. . . ..... . . ... . .. .. .. .. .. .. ...

Experimental Apparatus and Procedures. .. .. .... ...... ..... .. 2Wind Tunnel. .. .. ..... ..... ...... ..... ..... .. 2Model Rotor Test Apparatus .. .. ... ...... ..... ...... .. 2

Model Test Stand and Support. .. .. ...... ..... ..... ... 2Model Rotor .. .. .... ..... ...... ..... ...... .. 3Rotor Performance Data Acquisition and Reduction .. .. ... ..... ... 3

Matrix of Test Conditions .. .. ..... ..... ..... ...... .. 3Acoustic Instrumentation .. ... ..... ..... ...... ...... 4Microphone Array Traverse System. .. .. ...... ..... ....... 4Fuselage-Mounted Microphones .. .. ... ...... ..... ..... .. 4Acoustic Data Reduction and Analysis. .. .. .... ..... ...... .. 5Data Quality. .. .. ..... ..... ...... ..... ....... 5

Tunnel Flow Quality .. ... ..... ...... ..... ..... .. 5Rotor Performance Data. .. .. ..... ..... ..... ....... 5Background Noise .. .. .. ...... ..... ...... ..... .. 5Acoustic Reflections .. .. ... ..... ...... ..... ...... 6Acoustic Shielding by Fuselage. .. ... ..... ..... ...... .. 7Steadiness and Repeatability of Rotor Acoustic Data. .. .... ..... .. 7

Testing Procedures and Measurement Accuracy .. .. ... ..... ...... 7

Presentation of Data. .. .... ...... ..... ...... ...... 8

References. .. .. ..... ...... ..... ...... ..... ... 8

Tables. .. .. ..... ..... ...... ..... ..... ...... 9

Figures .. .. ...... ..... ..... ...... ..... ..... 11

Averaged Acoustic Signals .. .. .... ..... ...... ..... ... 23

Accession For

NTIS R&DTIC TABUnannounced 03Justificatio

ByDistribution/

Availability CodesAval~i -and/or

Dist sj~eoiaa

OTIC

It4SPIECTID

LII.

Abstract An extensive range of in-flow acoustic measure-ments were acquired in a plane underneath and up-

" Acoustic data are presented from a 40-percent- stream of the rotor model using a traversing nine-scale model of the four-bladed BO-105 helicopter microphone array. A digital acoustic data acquisi-main rotor, tested in a large aeroacoustic wind tun- tion system was employed to guide the choice of thenel. Rotor blade-vortex interaction (BVI) noise data test matrix and identify optimum measurement lo-in the low-speed flight range were acquired using a cations by using on-line identification of strong BVItraversing in-flow microphone array. The experimen- noise test conditions. The BVI directivity was inves-tal apparatus, testing procedures, calibration results, tigated by using an array of microphones traversingand experimental objectives are fully described. A in a large plane under and upstream of the rotor. Alarge representative set of averaged acoustic signals high quality data base for acoustic localization tech-are presented. . niques was acquired through a large range of mea-

surement locations. The occurrence of BVI acousticIntroduction signals created on the retreating side of the rotor was

pursued by positioning the microphone array underThe primary objectives of the test program re- and downstream of the rotor, in positions previously

ported here were (1) to acquire a comprehensive data found to best measure the phenomenon (ref. 3).base to improve the definition of the directivity pat- This paper addresses the general philosophy andterns of rotor blade-vortex interaction (BVI) impul- experimental approach of this program. Test resultssive noise, (2) to investigate more fully retreating- on acoustic directivity, retreating-side BVI, and BVIside BVI noise, and (3) to improve knowledge of the source locations have been presented in references 4locations of BVI noise sources. Secondary objectives to 6. In the present paper, the model test rig, instru-of the program were (1) to access the far field of mentation, data acquisition and reduction, acousticrotor BVI noise, (2) to extend the investigation of calibrations, and experimental procedures are fullyreference I into the scalability from model- to full- documented. A large representative set of the aver-scale of the BVI signal at high advance ratio, (3) to aged acoustic signals are presented.explore the parametric effects of advance ratio, tip-path-plane angle, and thrust coefficient on BVI noise, Symbolsand (4) to acquire a noise data base for future devel- CT rotor thrust coefficient, T/irpwR 4

opment of a BVI noise prediction methodology.The test was performed in the open test sec- filter cutoff frequency, Hz

tion of the Duits-Nederlandse Windtunnel (DNW), r radial distance from rotor hub toa large aeroacoustic test facility, utilizing a four- microphone (see fig. 1), mbladed, 40-percent dynamically scaled model ofthe Messerchmitt-B6lkow-Blohm GmbH BO-105 he- MH hover tip Mach number

licopter main rotor. The experiment was per- R rotor radius, 2.0 mformed jointly with research personnel of the German T rotor thrust, NAerospace Research Establishment, the DeutscheForschungs- und Versuchsanstalt fur Luft- und V flow speed, m/secRaumfahrt (DFVLR). The model rotor and the rotor Xw streamwise location of traversing arraytest stand were provided and operated by research relative to hub, positive upstreampersonnel of the Rotory Wing Aircraft Branch of (see fig. 1), corrected for streamwisethe DFVLR Institute of Flight Mechanics. Acous- movement of hub due to model pitch,tic instrumentation support was provided by research mpersonnel of the Technical Acoustics Division of theDFVLR Institute of Design Aerodynamics. Yw cross stream location of traversing

High quality acoustic data were acquired due to array microphones relative to hub,

the excellent fluid dynamic and acoustic properties positive under advancing side (see

of the DNW. In particular, the tunnel has quite low fig. 1), m

in-flow background noise and turbulence levels and a ZW vertical location of traversing array,sizable anechoic open test section. The importance positive above hub (see fig. 1), mof low turbulence airflow on rotor acoustic testingis stressed in reference 2, a comparison of acoustic ashaft angle of rotor shaft from vertical, deg

results from a model rotor tested in both the DNW aTPP rotor tip-path-plane angle, positiveand the French CEPRA-19 tunnel. nose up (see fig. 1), deg

Af spectral bandwidth, Hz figure 4 and table I. The stand consists of three ma-

9 polar angle, angle centered at hub jor subsystems: the hydraulic drive system, the rotorfro p-pa leane icre phoe balance system, and the rotor control system. Dur-from tip-path plane to microphone ing this test, the stand was housed within an acous-location, positive down (see fig. 1), deg tically insulated fiberglass shell and was attached

p advance ratio, V/wR to the computer-controlled, hydraulic sting supportdensity, kg/rn3 mechanism.

The rotor drive system consists of a seven-pistonazimuth angle in tip-path plane from axial drive motor connected by hydraulic lines torotor hub to microphone location, zero a remotely located electrically driven pump. Theover tall, 90' over rotor advancing side axial hydraulic motor is connected directly to the(see fig. 1), deg rotor shaft and has a power capability of 100 kW at

1050 rpm.w rotational speed of rotor, cycles/sec The rotor balance system is a six-component

Abbreviations: balance containing separate measuring elements forstatic and dynamic load components. The balance

ATD analog-to-digital consists of a lower and an upper plate connected

BVI blade-vortex interaction through transmission rods. Seven load cells on the

DFVLR Deutsche Forschungs- und Versuch- lower plate measure the static components. The dy-DFVLR De utsch Foru- und rsuh- namic components are measured by means of piezo-sanstalt fur Luft- und Raumfahrt electrical transducers connected to the transmission

DNW Duits-Nederlandse Windtunnel rods. A separate load cell is provided to measure(German-Dutch Wind Tunnel) the rotor torque and is located between the upper

and lower balance plates. This ensures that no un-DTA digital-to-analog desired coupling between the rotor balance and theMic microphone drive shaft occurs.

The rotor control system is of a swashplate sys-rms root-mean-square quantity tern consisting of three electric actuators attached

rpm revolutions per minute to the upper plate, the swashplate, and the rotatingblade pitch control rods. The actuators provide col-

SPL sound pressure level, dB referenced to lective and cyclic blade pitch control by moving the2 x 10- 5 Pa rms nonrotating part of the swashplate and are remotely

controlled. A potentiometer at the root of one of theExperimental Apparatus and Procedures blades measures the blade angle of incidence during

Wind Tunnel rotation.The fuselage is constructed of a 4-mm-thick re-

The test was performed in the open test section of inforced fiberglass shell covered on the inside withthe Duits-Nederlandse Windtunnel (DNW), located a heavy 3.5-mm-thick layer of sound-damping ma-in the North East Polder, The Netherlands. The terial and a 30-mm-thick layer of open cell sound-DNW is a subsonic, atmospheric, closed circuit wind absorbing foam. The outer side of the fuselage istunnel with three interchangeable, closed test section lined with 50-mm-thick open-cell foam to minimizeconfigurations and one open configuration. The open acoustic reflections. The overall sound pressure levelconfiguration employs an 8 x 6 m contraction section, transmission losses through the fuselage were 27 dBshown in figure 2, and a 19-m-long test section, sur- for simulated hydraulic drive noise and 30 dB forrounded by a large anechoic hall of about 30 000 m3 white noise. To maximize the transmission loss, spe-lined with absorptive acoustic wedges. The tunnel cial care was taken to shield both the gap betweenhas excellent fluid dynamic qualities, fully described the rotating rotor head and the top of the fuselage -in references 7 to 10. and the gap between the fuselage and sting.

The model rotor rig was supported by theModel Rotor Test Apparatus computer-controlled, hydraulically actuated sting.

Prior to the test, a thorough analysis was made ofModel Test Stand and Support the dynamic behavior of the rotor test rig and stingThe DFVLR rotor test stand (refs. 11-13) is combination to ensure that a ground resonance prob-

shown installed in the DNW open test section in fig- lem would not be encountered. The sting was cov-ure 3. Details of the rotor test stand are given in ered with a streamlined sound absorptive lining to

2

minimize acoustic reflections. The sting control sys- filtering. The rotating data were then merged withtern was programmed to keep a model reference point the fixed system data via a 64-channel encoder.at a preselected height in the test section, for the The fixed system also has a 32-channel capac-range of angle of attack (ashaft). However, it was ity. Signals from the displacement transducers, thenot possible to maintain the reference point at a fixed static and dynamic balance transducers, the shaftstreamwise location for the range of angle of attack. torque transducer, the shaft rpm encoder (360-per-

revolution), and the shaft position encoders (once-Model Rotor per-revolution and 512-per-revolution) were trans-

mitted to a PCM data acquisition system. The dataThe rotor is a 40-percent, dynamically scaled acquisition system consists of a central processor

model of a four-bladed, hingeless BO-105 rotor unit, a coprocessor, a random access memory unit,

(fig. 5). The rotor has a diameter of 4 m with a root and a magnetic tape rcorder and has a useful fre-

cutout of 0.350 m and a chord length of 0.121 m.

The rotor blade is constructed of an NACA 23012 quency range up to 250 Hz.airfoil, with the trailing edge modified to form a Details of the rotor data processing are given in5-mm-long tab, to match the geometry of the full- reference 13 and are summarized here. For all signals,

5-mmlon ta, t mach he gomery f te fll- 20 revolutions of time domain data were written to

scale rotor. The rotor blades have -8' of linear twist, digitaltions o tie an a con to

a standard square tip, and a solidity of 0.077. Fur- digital tape. For on-line analysis and control the

ther details are given in table I and reference 11. central processor performed a Fourier analysis of theThe nominal rotor operating speed was 1040 rpm, data of a single revolution. A second processor fed

giving an acoustic blade-passage frequency of about with selected analog input of the fixed and rotating

70 Hz. The nominal hover tip Mach number was 0.64. system provided continuous on-line display of the

The rotor blades are made of glass-fiber-reinforced rotor control parameters: hover tip Mach number,

plastic and have essentially the same mass and stiff- thrust, hub moments, blade bending, and pitch linkloads. The final processing of the rotor performanceness distributions as the full-scale rotor. However, d s de f-l in b r the r esultsaofthe blade chord length (0.061R) is a slightly larger data was done off-line by averaging the results of

the 20 revolutions of stored data. These resultsscale than the full-scale chord (0.054R) in order to include such parameters as collective pitch, cyclicmaintain the proper Locke number scaling (ratio be- ich, ch ar tr powe pth, andtween the aerodynamic forces and the mass and elas- pitch, coning angle, rotor power and thrust, and

both the steady and the dynamic components of thetic forces, ref. 11). Each blade is equipped with a rotor forces, moments, and longitudinal and lateralsmall tab located at 70 percent of the radius, measur-ing 60 x 10 mm (shown in fig. 5). These tabs, in addi- flapping angles.tion to the pitch rods, are used to adjust the track ofeach blade in the rotor system. Strain gages installed Matrix of Test Conditionsnear the root of each blade are used to measure the A nominal test plan was developed to investigateblade flapping, lagging, and torsional moments. the three primary test objectives and concentrated

Rotor Performance Data Acquisition and on two thrust coefficients, 0.0044 and 0.0030, andReduction the forward speed range of 20 to 40 m/sec (p = 0.09

to 0.18) at a range of tip-path-plane angles for con-The rotor performance data were obtained from stant nominal hover tip Mach number of 0.64. The

the rotating and fixed systems of the DFVLR test value of 0.0044 is the nominal thrust coefficient for Sstand control system (ref. 12). The rotating system the full-scale BO-105, while the value of 0.0030 wasacquired the signals of the strain gages on the rotor chosen as a lower limit of thrust level. To investigateblades (flapping, lagging, and torsional moments), the secondary test objectives, a smaller set of condi-on the control rods (pitch link forces), on the ro- tions included velocities of 50 and 60 m/sec, thrusttor shaft (bending moment), and on the blade root coefficients ranging from 0.0036 to 0.0056, and hoverpotentiometer (blade pitch angle). tip Mach numbers ranging from 0.56 to 0.72.

The rotating signals we-e transmitted by two 16- To determine the optimum test conditions forchannel pulse-code-modulated (PCM) encoders on strong BVI noise generation and the optimum mea-the rotating rotor head. The data were multiplexed, surement locations for the traversing microphone ar-converted to a digital form, and then formatted into ray, an initial exploratory approach was used. Totwo serial data streams for transmission through slip minimize testing time during this exploratory phase,rings. Subsequently, both serial data streams were acoustic data were acquired with an on-line ATD sys-reformatted into parallel signals by two decoders tem and were not recorded on analog tape. Thefollowed by digital-to-analog (DTA) conversion and on-line analysis performed during this exploratory

3

ap--

matrix was used to fine-tune the final, more ex- time domain and spectral analysis. A two-channeltensive, test matrix, for which acoustic data were fast Fourier transform analyzer was also employedrecorded on analog tape for postprocessing. Data for quick-look analysis during testing.from the initial exploratory matrix are presented in Microphone calibrations were performed using areferences 4 and 6, and the final expanded test ma- sound level calibrator at the beginning and end of thetrix is presented in table II. The data presented here test. All microphone gains were adjusted to produceare the postprocessed acoustic signals from the final 500-mV rms output for an acoustic level of 114 dB atexpanded matrix. 1000 Hz. In addition, a daily calibration of a 1000-

Hz, 500-mV rms signal was recorded on all channelsAcoustic Instrumentation by signal insertion at the tape recorder inputs.The acoustic instrumentation consisted of a nine-

microphone in-flow array mounted on a traversing Microphone Array Traverse Systemsystem and two in-flow microphones mounted on therotor fuselage as shown in figure 3(b). The mi- The microphone array traverse system consistedcrophones were '/2-in. pressure-type condenser mi- of a horizontal wing with its span normal to the flowcrophones equipped with standard "bullet" nose direction and a traverse system with a total rangecones. Each complete microphone system (micro- in the flow direction of 8.2 m (7 m upstream, 1.2 mphone, preamplifier, and adapter) was calibrated us- downstream of the hub, see fig. 3). The microphonesing the electrostatic actuator method to document were arranged symmetrically with respect to theits frequency response. This response was found to tunnel centerline, spaced 540 nmn apart. The arraybe flat between 5 and 5000 Hz, sufficient for the fre- vertical position was nominally 2.1 m below the rotorquency range of the BVI noise (approximately 500 to hub, although a small set of data was acquired at 1.64000 Hz for model scale). and 2.6 m below the hub.

Signal conditioning of the microphones was per- The microphone holders employed a "soft"formed by computer-controlled amplifier and filter vibration-isolating mounting. A cross section of thesystems. The amplitude and phase characteristics wing is shown in figure 6. The total height of theof the two-pole Butterworth filters were investigated entire structure was such that only the streamlinedbefore the test for high-pass filtering at three nom- wing support struts crossed through the shear layer.inal cutoff frequencies. The amplitude response is The wing and support struts were covered with aflat in the passband. The phase shift is 1800 at the 25-mm-thick, open-cell foam airfoil section; and thecutoff frequency f,, is approximately 40' at 5fc, and supporting structure was covered with a 100-mm-negligible at approximately 1Ofc. The filters were thick foam lining except at the base which was cov-found to be well matched in their phase characteris- ered with 800-mm foam wedges.tics, within 10 in the passband. The traverse mechanism was powered by a

The acoustic data, the rotor once-per-revolution variable-speed dc electrical motor. Control and posi-and 512-per-revolution signals, and a time code were tioning was obtained with a servo position controller.recorded on a 14-track analog frequency-modulated The positioning accuracy was 2 mm. Prior to datarecorder. The data were recorded at a tape speed acquisition, the alignment of the traversing array was30 inches per second, which yielded a useful fre- calibrated over its range of motion. The alignmentquency response to about 20 kHz. in the cross flow direction was ±2 mm; in the ver-

To verify the frequency response of the entire tical direction, less than ±1 mm. The deflection ofmeasurement system in situ (from preamplifier to the traversing array due to aerodynamic drag wastape recorder), a white noise signal was inserted on the order of 9 mm in the streamwise directionsimultaneously into each preamplifier and recorded at 60 m/sec. The accuracy of this correction is es-on tape. The auto and cross power spectral densities timated to be ±3 mm. These deflections were cal-of the white noise signal were checked to ensure culated off-line and applied to the measured arrayflat frequency response and to document phase lag position data to correct the calculated microphonebetween channels. positions.

The digital amplifier and filter settings weretransmitted to a second, larger computer. During Fuselage-Mounted Microphonestesting, up to 10 microphone channels could be digi-tized using a 12-bit, high-speed simultaneous analog- Two microphones were mounted on the fuselage,to-digital (ATD) converter. The computer was em- one under each side of the rotor disk, at azimuthployed to control the ATD converter, to store calibra- angles of approximately 90' and 2700. The micro-tion and amplification factors, and to perform on-line phones were mounted in vibration isolation mounts

4 4 , y,_

similar to the mounts for the traversing array micro- the 8 x 6 m nominal test section, at 7 m from the jetphones (fig. 6). These microphones were mounted exit. Turbulence intensities in both the streamwisewith a small negative angle (approximately 50) to and the cross stream direction are less than 0.5 atthe tunnel free stream. This was an attempt to mini- this location.mize wind-induced background noise due to the free- In the low-speed range, the open-jet configuration -1stream velocity, because most of the data were at can exhibit a low-frequency, low-amplitude pulsationpositive rotor shaft angles. These microphones are of the mean flow, similar to the pulsations previouslystill subjected to the influence of the induced flow of observed in other open-jet tunnels (ref. 14). This pul-the rotor system, which cannot be calibrated. sation occurred at certain velocities between 20 and

28 m/sec, with a maximum amplitude of ±0.75 m/secAcoustic Data Reduction and Analysis and a period of about 10 seconds. In some cases this

pulsation caused problems in achieving stable rotorBefore being recorded on analog tape, the micro- performance parameters, so that some parts of the

phone data were high-pass filtered at 4 Hz to remove test matrix had to be redesigned or omitted. Overall,very low-frequency content. The microphone and this pulsation was of sufficiently low frequency to beblade position rrefeence signals (once-per-revolution considered quasi-steady compared with the analysisand 512-per-revolution) were conditionally digitized time for both the rotor performance and the acousticusing a sample rate keyed to the 512-per-revolution data.

signal, which yielded 1024 data points per revolu-

tion, or a sample rate of about 18 000 samples per Rotor Performance Datasecond. An antialiasing filter was employed at 9 kHz.This conditional sampling technique is used to ensure The nominal thrust coefficients tested were 0.0030that the acoustic samples are acquired when the ro- and 0.0044. The actual average thrust coefficientstor blades are in the same azimuthal position for ev- were 0.0029 and 0.00435 with standard deviations ofery revolution sampled. The time histories were dig- 3% and 1.4%, respectively. The nominal hover tipitized in this manner, and then 40 revolutions were Mach number was 0.64, with average and standardaveraged to obtain an average acoustic waveform and deviation of 0.636 and 0.5%. The first harmonics ofstandard deviation for each test condition. The av- lateral and longitudinal flapping angles were gener-erage time history and its standard deviation were ally less than 0.30. During the pretest calibrations,stored on computer disk. a check was made to ensure that a change in the

To obtain spectra, the data of four sequential ro- traversing array position in the test section did nottor revolutions were transformed to the frequency affect the rotor performance by requiring changes todomain using a 4096-point fast Fourier transform al- the rotor control inputs.gorithm. This procedure was performed 40 times,requiring the data of 160 revolutions, and the re- Background Noisesults were averaged to obtain an average narrow- The background noise data were acquired with allband spectrum, also stored on computer disk. Con- testing and model hardware installed in the tunnel.sidering each power spectrum as a chi-squared ran- The blades were not installed, but the hub wasdom variable, the statistical accuracy of the spectral spinning at nominal speed (1040 rpm).results is 0.8 to -1.0 dB for an 80-percent confidenceinterval. Effect of tunnel speed. Background noise was

A time domain window was not applied to these measured for a range of tunnel speeds at a fixeddata. The conditional sampling approach employed nominal traverse position 3 m upstream of the hub.minimizes leakage of the acoustic energy at the blade- Examples of the spectra for microphone 1 at 20, 40,passage frequency and its harmonics, and thus a and 60 m/sec are shown in figure 7(a). Each oftime domain window is not required to improve the the nine microphones located on the traversing arrayspectral estimates at those frequencies. shows generally the same background noise levels as

Data Quality microphone 1 at this position (Xw = 3 m). The low-frequency levels of the traverse microphones increase

Tunnel Flow Quality about 28 dB (from 82 to 110 dB) due to increasingthe speed from 20 to 60 m/sec. Data for fuselage

The DNW has very good aerodynamic qualities microphone 10 is shown in figure 7(b). The levelswhen operated in the open throat mode (refs. 7-10). increase only about 15 dB (from 90 to 105 dB) withA potential core of uniform flow (mean flow velocity an increase in speed from 20 to 60 m/sec. The±0.5%) has been defined as a 5 x 3 m core within low-frequency background noise levels of the fuselage

5

microphones at the lower tunnel speeds are higher downstream at the highest tunnel speed. The high-than those measured by the traversing microphones. est background noise for the fuselage-mounted micro-The higher frequencies of the spectra are about the phones probably occurs at the largest shaft angle andsame for the fuselage and traverse microphones. The highest tunnel speed. Several test conditions fittinghigher frequency noise levels for all microphones start these conditions were chosen and the rotor signalsat about 35 dB at 20 m/sec and increase to about were compared with the background noise. The rotor55 dB at 60 m/sec. spectra and the background spectra are almost iden-

tical at the first spectral line (20 Hz), but above thisEffect of traversing array position. Background point the rotor spectrum is at least 5 dB higher than

noise was measured at 40 m/sec for X.. = 1, 3, the background spectrum and typically 20 dB higherand 5 m and at 60 m/sec for X, = -0.7 and 3 m. in the frequency range dominated by BVI noise, asThe spectral levels increase consistently (by about shown in figure 10. The results indicate that the10 dB) as the traverse moves downwind and closer background noise levels are not a contaminant forto the model (X, = 5 to 1 m). This is illustrated any of the microphone measurements.by figure 8, which shows the background noise levels The effect of the spurious tones observed by thefor Xw = 1, 3, and 5 m at 40 m/sec from micro- traverse microphones at the higher tunnel speeds andphones 1 and 5 and by figure 9, which shows the upstream positions was also investigated. These datadata for X. = -0.7 and 3 m at 60 m/sec from mi- are seen in figure 10, which shows that although thecrophones I and 5. This increase in level at the down- background tones are just below the rotor signal,stream positions is probably due to the increased they do not appear to be a significant contaminant.proximity of the microphones to the bottom shearlayer (see fig. 3(a)) and increased proximity to themodel system. The levels measured at the fuselage Acoustic Reflections -

microphones appear to be fairly insensitive to thetraverse position, indicating that the traverse itselfis not creating additional background noise. To measure the potential contamination of the ro-

tor signal due to reflections, small explosive chargesBackground tones. Discrete tones were measured were specially mounted on the model rotor test rig

by some of the traverse microphones, particularly and detonated to create an impulsive noise source.at tunnel speeds of 30, 40, and 50 m/sec, in the The explosives generate peak pressure levels of ap-range of 2 to 5 kHz. The tone frequencies are not proximately 148 dB at a distance of 4 m. The chargesrelated to tunnel speed. An example can be seen were mounted in a three-rod mock-up rotor, within figure 8(b) for microphone 5 at 40 m/sec at two 10 charges on each rod, mounted between 80 andtraverse positions. The highest levels of these tones 100 percent of the rotor radius. The mock-up rotorappear to be about 70 dB, which is typically much was installed on the rotor head with the three rodslower than the rotor signals in that frequency range located at 60', 1800, and 3000 azimuth (a). Approx-(see the following section on signal-to-noise ratio). imately 30 charges were ignited to assess the acous-The tones have the largest amplitude at upstream tic reflections for the following tunnel configurations:locations, although they are present at lower levels at tunnel speeds of 0 and 60 m/sec, Xw of 4, 2, 1, andXw = 1 and -0.7 m. These tones are not measured -0.7 m, and Z. of -0.5, 0, 0.3, and 0.5 m.by all the traverse microphones at once, indicating The acoustic signals were recorded on analog tape 41that the sources are localized, and analyzed on-site. For all the tested configura-

tions, the reflected signals were generally less thanEffect of rotor shaft angle. Background noise 10 percent of the direct blast signal, or 20 dB down

levels were studied for Xw = 3 and -0.7 m for rotor from the direct signal, and in many cases were ofshaft angles of -5', 00, 50, and 100. No significant negligible amplitude. The effect of increasing tunneleffect was seen in the traverse microphone data. speed was found to be negligible, as was the effect of 0The data for a fuselage microphone (microphone 10) rotor hub vertical position. An example of the blastexhibited slightly lower levels at -5', which was signals measured at 60 m/sec by microphones 1, 3, 5,expected due to the preset microphone angle of 50 7, and 9 at Xw = 4 m is shown in figure 11 for a blast(see "Fuselage-Mounted Microphones"). located at 0 = 3000. The difference in the maximum

pressure measured at microphones 1. 3, and 5 can beAcoustic signal-to-noise ratio. From the above re- attributed to distance from the source. The signals

suits, the highest background noise for the traverse at microphones 7 and 9 have been shielded by themicrophones occurs when the traverse is the farthest fuselage, as discussed in the next section.

6

Acoustic Shielding by Fuselage in figure 12. At p = 0.092, figure 12 shows boththe instantaneous data (fig. 12(a)) acquired using the

Acoustic diffraction for the traversing array mi- on-line ATD system and the 40-average time historycrophones was identified and is due to the presence (fig. 12(b)) obtained from the postprocessing. Theof the fuselage. When the traversing array is moved general features of the instantaneous data are con-close to the model, the microphones at one end of sistently seen in the averaged waveform. Particularthe traverse are shielded from the acoustic signal features to note are the small impulses approximatelyfrom the opposite side of the rotor disk. This was 0.01 period after the major impulses of the first threequantified by comparing the known propagation dis- blade passages and the large impulse 0.01 period be-tances(fromthe sourceto each microphone)withthe fore the third major impulse. An equally good com-measured blast signal arrival times, amplitudes, and parison, particularly in the BVI characteristics, canmodel geometry be found for a = 0.138 in figures 12(c) and 12(d).

From t path g eom rohe test hardware, a free The repeatability of the rotor signal was stud-acoustic path to all the microphones exists at X = ied for several test conditions repeated during the2 m, and all the array microphones receive a directly experiment. An example of the instantaneous datapropagated blast signal. However, the amplitudes acquired using the on-line system at different timesmeasured at microphones 1, 2, and 3 when the source during the experiment is given in figure 13, for

is located at V) = 60' are attenuated to a larger de- d 01n the 18 Thes d w fi tered

gree than can be attributed to spherical spreading. by =a 01500-3000 andHz band-pass filter data(ref.5). filtered

(This is also observed at microphones 7, 8, and 9 there is considerable random noise evident in these

when the source is located at 0 = 300'.) This in- data, the general amplitudes and features of the ma-

dicates that the fuselage is causing diffraction of the jor impulses can be seen in the two measurements.

acoustic signal for this particular geometry. For tra-

verse positions that are close to and under the model, Testing Procedures and Measurementthe blast signals received by the "shielded" micro- Accuracyphones are not the direct signal but a combination of Corrections to the free-stream flow angle anda reflected and a diffracted signal, with significantly speed ion to the ree-sthe fng ndlower amplitudes. This can be seen in the data of speed due to the presence of the lifting rotor in thelowerraplites. This cad n figure seen fr t1 m and test section were calculated according to the methodmicrophones 7 and 9 in figure 11, for X = Iof Heyson (ref. 15) and applied to the measured datathe blast located at 0 = 300'. The delay time, at- off-line to obtain the corrected tip-path-plane anglestenuation, and distortion of the blast waveform can presented here. These corrections are considered rea-be seen in the shielded microphones. snte eres the retiow are atnsidere

These results indicate that the directivity or abso- sonable estimates of the true flow angle at moderatelute levels of advancing- or retreating-side BVI can- tunnel speeds, but become less reliable as the correc-not be accurately determined from the shielded mi- tion increases at the lower tunnel speeds, less thancrophone locations. The conclusions can be sunuma- 20 mn/sec. I.rzedhnte t e o cBecause of the pivoting of the support sting torized in the table below. achieve a specified shaft angle, the center of the rotor

hub experiences both a vertical and a streamwise

Source Shielded translation. The sting controller was programmed

azimuth, deg XW, m microphones to reposition the hub at the same vertical position

60 2.0 1, 2, 3, 10 for any shaft angle. The streamwise movement of

1.0 1,2,3,4,10 the rotor hub could not be corrected by repositioning-.7 1, 2,3,4, 10 the sting, but is calculated off-line and is accounted

for in the calculation of microphone locations. The

300 2.0 7, 8, 9, 11 streamwise position of the microphones Xw is thus

1.0 6, 7, 8, 9, 11 corrected for the movement of the hub due to model

-.7 6, 7, 8, 9, 11 pitch angle.In addition to the kinematic motion of the sting

support, the actual rotor hub position was also in-

Steadiness and Repeatability of Rotor Acoustic fluenced by vertical deflections due to its weight, the

Data rotor angle, the rotor thrust level, and aerodynamicdrag. These effects were calibrated before data ac-

To illustrate the steadiness of the rotor signals, quisition by measuring the rotor hub position for theseveral cases were chosen for comparison. Two of ranges of shaft angle, rotor thrust, and tunnel speedthese cases, at pj = 0.092 and u = 0.138, are shown contained in the test matrix. These corrections were

7

then applied to the data off-line. The accuracy of the 3. Leighton, Kenneth P.; and Harris, Wesley L.: Onrotor hub position measurements is ±2 mn. Mach Number Scaling of Blade/Vortex Noise Produced by

The rotor parameters-tip-path-plane angle, Model Helicopter Rotors at Moderate Tip Speeds. FDRLhover tip Mach number, and thrust-were set using Rep. 84-3, Dep. of Aeronautics and Astronautics, Mas-the digital displays at the rotor controls. The ro- sachusetts Inst. of Technology, Oct. 1984.

tor operator set the rotor speed for the desired value 4. Martin, Ruth M.; and Splettstoesser, Wolf R.: Acousticof hover tip Mach number, simultaneously adjusting Results of the Blade-Vortex Interaction Acoustic Testcolehove t ch obainube siultanousy a Tig of a 40 Percent Model Rotor in the DNW. Proceedingscollective pitch to obtain the desired thrust. The ro- of the National Specialists' Meeting on Aerodynamics andtor was operated so that the first harmonics of the Aeroacoustics, American Helicopter Soc., c.1987.shaft bending moments and of lateral and longitudi- 5. Martin, R. M.; Splettstoesser, W. R.; Elliott, J. W.;nal flapping were as close to zero as possible. In this and Schultz, K.-J.: Advancing-Side Directivity andcase, and neglecting blade bending, the measured ro- Retreating-Side Interactions of Model Rotor Blade-tor shaft angle was thus equivalent to the tip-path- Vortex Interaction Noise. NASA TP-2784, USA-plane angle. AVSCOM TR 87-B-3 1988.

6. Splettstoesser, W. R.; Schultz, K. J.; and Martin,

Presentation of Data Ruth M.: Rotor Blade-Vortex Interaction ImpulsiveNoise Source Identification and Correlation With Rotor

The data presented in the plots at the end of this Wake Predictions. AIAA-87-2744, Oct. 1987.paper are a representative set of the postprocessed 7. Van Ditshuizen, J. C. A.; Courage, G. D.; Ross, R.;results of the final test matrix defined by table II. and Schultz, K.-J.: Acoustic Capabilities of the German-Preceding these plots is a detailed table of test condi- Dutch Wind Tunnel DNW. AIAA-83-0146, Jan. 1983.tions corresponding to the plots. Each plot presents 8. Compilation of Calibration Data of the German-Dutch

the averaged time histories of traversing array mi- Wind Tunnel. MP-82.01, Duits-Nederlandse Wind-

crophones 1, 3, 5, 7, and 9. Spectral results are tunnel, Mar. 13, 1982.not presented here but averaged narrow-band spec- 9. Ross, R.; Van Nunen, J. W. G.; Young, K. J.; Allen,

R. M.; and Van Ditshuizen, J. C. A.: Aero-Acoustic Cal-tra have been calculated for all test conditions. Both ibration of DNW Open Jet. DNW TR 82.03, German-the averaged time histories and the spectral results Dutch Windtunnel (DNW) (North East Polder, Nether-are available to the research community for their use lands), July 1982. (Also available as Boeing Documentin rotor noise work and can be provided in the form D6-51501, 1983.)of plots, computer listings, tapes, or computer disks 10. Seidel, M.; and Maarsingh, R. A.: Test Capabilitiesas required. Interested persons should contact the of the German-Dutch Wind Tunnel DNW for Rotors,principal author of this document. Helicopters and V/STOL Aircraft. Proceedings of the

Fifth European Rotorcraft and Powered Lift Aircraft Fo-rum, Sept. 1979, pp. 17-1-17-22.

NASA Langley Research Center 11. Langer, H. J. (SCITRAN, transl.): DFVLR Rotorcraft -

Hampton, VA 23665-5225 Construction and Engineering. NASA TM-77740, 1984.

December 23, 1987 12. Langer, H.-J. (Leo Kanner Assoc., transl.): Data Input,Processing and Presentation. NASA TM-77739, 1984.

13. Breustedt, Wolfgang (SCITRAN, transl.): Data Analysis

References on the Rotor Test Stand Program for Interactive Process-ing. NASA TM-77948, 1985.

1. Splettstoesser, W. R.: Schultz, K. J.; Boxwell, D. A.; 14. Applin, Zachary T.: Modification to the NASA Langleyand Schmitz, F. H.: Helicopter Model Rotor-Blade Vor- 4- by 7-Meter Tunnel for Improved Rotorcraft Aerody-tex Interaction Impulsive Noise: Scalability and Para- namics and Acoustics. NASA paper presented at themetric Variations. NASA TM-86007, USAAVSCOM American Helicopter Society National Specialist's Meet-TM-84-A-7, 1984. ing on Helicopter Testing Technology (Williamsburg,

2. Boxwell, D. A.; Schmitz, F. H.; Splettstoesser, W. R.; VA), Oct. 29-Nov. 1, 1984.Schultz, K. J.: Lewy. S.; and Caplot, M.: A Compar- 15. Heyson, Harry H.: Use of Superposition in Digital Com-ison of the Acoustic and Aerodynamic Measurements of puters To Obtain Wind-Tunnel Interference Factors for 0a Model Rotor Tested in Two Anechoic Wind Tnnels. Arbitrary Configurations, With Particular Reference toNASA TM-88364, USAAVSCOM TM-86-A-6, 1986. V/STOL Models. NASA TR R-302, 1969.

8

Id"EMM W ftw

Table I. Details of the BO-105 Model Main Rotor and Rotor Test Stand

Main rotor:Rotor diameter, m. .. ...... ..... ...... ..... ..... 4Blade airfoil section ... ..... ...... ..... ..... NACA 23012Number of blades .. ...... ..... ...... ..... ....... 4Blade solidity .. ..... ..... ...... ..... ..... .. 0.077Blade tip speed, rn/sec. ... ..... ...... ..... ..... .. 218Flapping frequency ratio .. ..... ...... ............ 1.111Lagging frequency ratio. .. ..... ..... ..... ...... .. 0.785Nominal rotational speed, rpm .. ... ..... ..... ...... .. 1040Nominal rotor thrust, N. .. .... ..... ...... ..... .... 3600Nominal rotor thrust coefficient .. ..... ...... ..... .... 0.0044

Drive system:Shaft power, kW. .. ..... ..... ...... ..... ....... 100Rotor drive moment, N-rn. .. ..... ..... ..... .. 900 at 1050 rpmPower (electric). .... ..... ..... ...... 3 phase, 380 V at 300 A

Balance load range:Axial force, N .. .... ...... ..... ..... ...... .. 1000Side force, N. .. .... ..... ...... ..... ..... ... 2000Thrust force, N. .... ...... ..... .... 7000 static ±1500 dynamicRolling moment, N-rn. .. .... ..... ...... ..... ..... 700Pitching moment, N-rn.. ..... ..... ..... ...... .... 700

Control system:Blade setting angle range, deg. .. ..... ...... ..... ..- 4 to 14

9

ij0

Table II. Final Test Matrix

Comment CT V, m/sec ashaft, deg Xw, m Zw, m MH

o: sweep 0.0044 17 0.078 a 7 to 10 5.0 -2.1 0.636

20 .092 6 to 10 2.5

25 .115 4 to 8 2.5

30 .138 2 to 6 1.0

32 .147 0 to 4 1.0

37 .170 -2 to 2 2.5

,u sweep 0.0044 b33 to 41 0.152 to 0.187 0 2.5 -2.1 0.636

28 to 36 0.129 to 0.166 2.0 1.0

25 to 35 0.115 to 0.161 4.0 1.0

20 to 26 0.092 to 0.120 6.0 2.5

17 to 22 0.078 to 0.101 8.0 2.5

13 to 21 0.060 to 0.097 10.0 5.0 -. _

Xw sweep 0.0044 38 0.175 0.5 c - 1.2 to 6.0 -2.1 0.636

35 .161 3.0

31 .143 5.0

25 .115 5.5

20 .092 8.0

19 .087 10.0e sweep 0.0044 30 0.138 a 4 to 7 -1.15 -2.1 0.636

14 sweep 0.0044 b28 to 34 0.129 to 0.156 5.0 -1.15 -2.1 0.636

Xw sweep 0.0044 30 0.138 5.0 d - 1.2 to 4.4 -2.1 0.636

a sweep 0.0030 30 0.138 al to 7 -1.15 -2.1 0.636

40 .184 -1 to 3

p sweep 0.0030 b2 8 to 35 0.129 to 0.161 2.8 -1.15 -2.1 0.636

36 to 44 0.166 to 0.20

2 1.2

Xw sweep 0.0030 30 0.138 2.8 d - 1.2 to 4.4 -2.1 0.636

40 .184 1.2

Near/far-field 0.0044 19 0.087 10.0 e1. 5 to 6.0 -1.6 0.636

data 31 .143 5.0 el. 5 to 6.0 -1.6

19 .087 10.0 f 2 .5 to 6.2 -2.6

31 .143 5.0 f2.5 to 6.2 -2.6

High I 0.0044 50 0.230 -5 to 1 2.5 -2.1 0.636

60 .276 -7 to 1 2.5 -2.1

60 .276 -7 to 0 2.57 -2.6

60 .276 -7 to 0 3.68 -2.6

M H sweep 0.0044 g2 7 to 35 0.140 5.0 4.5 -2.1 h 0 .5 6 to 0.72 _

CT sweep 0.0036 to 0.0056 31 0.140 5.0 4.5 -2.1 0.636

M H sweep 0.0044 917.5 to 22.5 0.090 8.0 4.0 -2.1 h 0 .5 6 to 0.72

CT sweep 0.0036 to 0.0056 20 0.090 8.0 4.0 -2.1 0.636

M H sweep 0.0044 933.3 to 42.8 0.175 0.5 4.0 1 -2.1 h0 .5 6 to 0.72

CT sweep 0.0036 to 0.0056 38 0.175 0.5 4.0 J -2.1 0.636

'Varied in increments of 0.5.bVaried in increments of 1.cVaried as follows: 6.0, 5.2. 4.4, 3.6. 2.8, 2.0, 1.5, 0.8, 0, -0.7, -1.2.dVaried as follows: 4.4, 2.8. 2.0, 1.2, 0.4. 0, -0.4. -0.7. -1.2.eVaried as follows: 1.5, 2.1. 2.7, 3.3, 4.0, 4.6.

fVaried as follows: 2.5. 3.5, 4.4. 5.4, 6.2.

gVaried in increments of 2.

hVaried in increments of 0.04

10

-

MIC Ywzw

ri

Q Tp -f e -

'wr HUBFLOW Xw MIC

TOP VIEW SIDE VIEWFigure 1. Diagram of coordinate system and test geometry.

[S

11

47

___ 44

85 16"

I I

t 14

6

) Prefabricated concrete circuit

() Eight-bladed fan with electric drive (nominal 12.5MW)

) Heat exchanger (1 1MW) with flow rectifier

O Anti-turbulence screensExchangeable test sections: .x9.5m 2 , 8x6m2 6x6m 2 , open Jet

( Air exchange hatches

0 Throttling device( Acoustically treated testing hall: 52x30x20m3.m'

® Parking hall

@ Control room(6 Experiment hall

@ Model assembly hall

@ Calibration hall()Office building

Figure 2. Plan view of the DNW facility.

L~12

001

00

Mica 1-9 1

T~~ aversin Ar;e

Traversing Arrayl.

(a) Slan view.

in ill i meters.g

8000

Re 2

4215Inclinoeter s Telemetryror hequipment

$Swashplate actuators

0 A0! .6 (b)monnt viane

~Acoustic lining

Figure 4dVulic motor d a m e

Oval 0

(a) Side view. .-

(b) Front view.14 Figure 4. Diagram of the DFVLR rotor test stand. All dimensions are in millimeters.

350

.1-TRACKING TAB-- 1400 (I TRAM

NACA 23012 TRAILING EDGE TABJ

121mm CHORD

1.9 0.9

TRAILING EDGE

Figure 5. Model BO-105 rotor blade geometry.

S480Acoustic lining

HolderA

Wing steel structure 150 x 75

Figure 6. Cross section of traversing microphone array wing and microphone holder. All dimensions are inmillimeters.

15

1161C~~~~ 101 l ?Rj ,22 j

110-

100-

90

~ 80 r/sec

0.co70 60

60 -') 4

50 -- 20

40 I I' v4!0 1000 2000 3000 4000 5000

Frequency, Hz

(a) Microphone 1.

110

100 -

90-

80 m r/sec0-

0

6024040

0 1000 2000 3000 4000 5000Frequency, Hz

(b) Microphone 10.

Figure 7. Background noise at X,, = 3 m, as a function of tunnel speed. Af 20 Hz,

16

110-

100-

90

0.~

60-t7

50''0 1000 2000 3000 400 5000

Frequency, Hz

(a) Microphone 1.

110-

10 0 t

90

~8O

70

60'

0 1000 2000 3000 4000 5000Frequency, Hz

(b) Microphone 5.

Figure 8. Background noise at V =40 rn/sec as a function of traversing array position. Af =20 Hz.

17

120-

110

100-

80 ---.

70

0 1000 2000 3000 4000 5000Frequency, Hz

(a) Microphone 1.

120

110-

100

I -0.7801 3

701

60 -60 1000 2000 3000 4000 5000Frequency, Hz

(b) Microphone 5.

Figure 9. Background noise at V =60 rn/sec as a function of traversing array position. Af =20 Hz.

11sF

- Rotor spectrumP =.185aTPP'IIIII0.9

100 Cr= .0044Xw= 2.5mMicrophone 5

m90 - -- - Background noiseV= 40 rn/sec

>0280-

CL0I.Ohl

0

6.0-

r2 VV

50 110 1000 2000 3000 4000 5000

Frequency, Hz

Figure 10. Comparison of typical rotor spectrum with background noise. Af =20 Hz.

XW 1 I.OmV -60 rn/80CSource at W - 3000

MaxPressure,

1 MIC Pa

0 9 202

* 0-.-. 7 194

5 1302X -0

0

0 1 2 3 4 5 6 7 8 9 1Tim.e. meec

Figure 11. Example of blast calibration data, showing shielded microphones 7 and 9.

19

IJ=.092aTPP= 3.80

20 - Xw =6.Om0 T=.0046

15

610-

5.

0

0

-50 .1 .2 .3 .4 .5 .6 .7 .8 .9 1.0

Time/Period

(a) Unaveraged on-line data at u 0.092.

20

15

0~10

5

0

-50 .1 .2 .3 .4 .5 .6 .7 .8 .9 1.0

Time/Period

(b) Averaged postprocessed data at p = 0.092.

Figure 12. Comparison of instantaneous on-line acoustic data with averaged postprocessed results(microphone 5).

20

pi=.138aTPP=2.2

25 - XWl=.OmCT= .04

20

015IL

0) 105 -

0

-5

-1010 .1 .2 .3 .4 .5 .6 .7 .8 .9 1.0

Time/Period

(c) Unaveraged on-line data at p = 0.138.

25

20

6~10-

5- -

0

-5

-1010 .1 .2 .3 .4 .5 .6 .7 .8 .9 1.0

Time/Period

(d) Averaged postprocessed data at u = 0.138.

Figure 12. Concluded.

21

15

10

0 U

05

0

1~ 5

-10

0 010 230 450 6

-15

010 230 450 6

Tie me(b at -nt49

Figure ~ 03 eetblt fflee nln aa .3;aP .' " . ;C .00mirohne1; 480z

022

7JW W 1W W W I ILKI5 1"NAU]rEWR WW KWMU

Averaged Acoustic SignalsThe data presented in the following plots are a representative set of the postprocessed

results of the final test matrix defined by table II. Each plot presents the averaged timehistories of traversing array microphones 1, 3, 5, 7, and 9. The following table is an indexof test conditions for the plots and page numbers.

Test Conditions for Plots of Averaged Acoustic Signals

V, otTpp, aXw, Zw, -

m/sec p deg m m CT Point MH Page

;17.0 ,z0.078 bl. 7 ,z5.3 -2.1 ;0.00435 210 --0.636 27.-..17.0 ;.078 b3 .0 :5.3 264 28;17.0 ;.078 b4 .6 ,,5.3 267 29;20.0 z.092 b2 .1 z2.8 225 30;20.0 ;.092 b4.1 221 31-z 20.0 z.092 b6.1 217 32;25.0 ,t.115 1.5 226 33z25.0 z.115 3.5 230 34z25.0 ;. 115 5.5 234 35;30.0 .138 .2 1.1 244 36

;30.0 .138 2.2 239 37;30.0 z.138 4.3 235 38

:32.0 ,:.147 -1.6 253 39;32.0 .147 -. 1 250 40;32.0 ;.147 .9 248 41-32.0 ,z.147 2.4 245 42

37.0 .170 -3.1 z2.5 262 4337.0 .170 -1.1 258 4437.0 .170 .9 254 4533.0 .152 -1.4 .00402 318 46

50.0 .160 -1.2 .00417 320 4739.0 .179 -1.0 :t .00435 324 4841.0 .187 -.8 , 326 4927.5 .130 -. 1 1.1 309 5030.3 .139 .1 311 5132.0 .147 .4 I 313 5234.0 .157 .5 0 0464 315 5335.9 .165 .8 z:%00435 317 5424.8 .113 1.6 ,1.2 ] 297 5526.5 .125 1.7 ,1.2 299 56 6

aXw varies with OTPP (see section "Testing Procedures and Measurement Accuracy").bAccuracy of estimated aTPP deteriorates as V decreases below 20 m/sec (see "Testing

Procedures and Measurement Accuracy").

23

Test Conditions for Plots of Averaged Acoustic Signals Continued

V, aTPP aXw Zw

m/sec 9 deg m m CT Point -1 fH Page28.5 0.132 2.2 1.2 -2.1 0.00416 301 z0.636 5731.2 .142 2.3 -z.00435 303 5832.8 .150 2.4 305 5935.0 .159 2.7 1 308 6020.1 .092 b2.1 ;z2.8 290 6122.0 .101 2.7 292 6223.8 .110 3.2 294 6325.6 .120 3.6 296 6417.3 .079 b2.7 2.9 284 6519.1 .087 b3.7 ;2.9 286 66

21.0 .095 4.4 2.9 288 6713.1 .059 bl.4 ,:5.5 275 6816.2 .073 b4.0 278 6918.3 .083 b5.2 280 7020.7 .093 6.2 1 283 7138.0 .175 -. 5 -. 1 400 72

.8 402 732.0 404 743.6 406 755.2 408 76

35.0 .161 1.7 -1.0 399 77.5 397 78

2.1 395 79I 3.7 393 805.3 391 81

31.1 -. 143 ;3.3 -. 9 380 82* 6 382 83

2.2 384 843.8 386 855.4 388 86

24.8 .114 2.9 -. 9 379 871.0 377 88 '3.1 374 894.7 372 906.3 369 91

20.0 z-.092 b,3.8 -. 8 .00476 358 92b, 3.8 .8 z.00435 360 93bz3.8 2.4 362 94

I I 54.1 4.0 364 95I i 4.1 5.6 366 96

18.9 1.087 bz5.7 -. 6 1 357 97

IXw varies with (aTPP (see section "Testing Procedures and Measurement Accuracy").bAccuracy of estimated OTPP deteriorates as V decreases below 20 rn/sec (see "Testing

Procedures and Measurement Accuracy").

24

Test Conditions for Plots of Averaged Acoustic Signals-Continued

V, TPP, aXw, Zw,

m/sec A deg m n CT Point MH Page18.9 ;0.087 b 5_.7 2.0 -2.1 ;0.00435 354 , 0.636 98

3.3 .00474 352 994.9 -. 00435 350 1006.5 348 101

;29.8 ;.137 2.3 -. 9 476 102

-29.8 z.137 3.8 473 103;29.8 .137 5.3 470 104

27.7 .127 2.9 512 10530.0 .136 3.2 510 10631.9 .145 3.4 508 107

34.1 .154 3.6 1 506 108;30.0 .138 3.2 -. 5 536 109

.2 538 110

.6 540 1112.2 542 1124.6 544 113

-.2 ;- 1.0 ;.00290 460 1141.3 457 1153.4 453 1165.9 448 117

40.0 .184 -1.6 469 11840.0 .184 .4 465 11940.0 .184 2.4 461 12027.4 .126 1.4 489 12130.9 .142 1.6 492 12234.6 .159 1.9 496 12335.6 .164 .5 ;1.1 497 12437.6 .173 499 12539.6 .182 501 126

41.7 .192 503 127

43.5 .200 505 12830.0 .138 1.6 -1.0 515 129

.3 517 130

.5 519 1312.1 521 132

.... 4.5 523 13340.0 .184 .6 -1.1 532 134

I .4 530 135.5 528 136

-1.3 527 _ 137

aX, varies with aTPP (see section "Testing Procedures and Measurement Accuracy").bAccuracy of estimated oTpP deteriorates as V decreases below 20 m/sec (see "Testing

Procedures and Measurement Accuracy").

25

Test Conditions for Plots of Averaged Acoustic Signals-Concluded

V, aTPP, aXw, Zw, -m/sec p deg m m CT Point MH Page

40.0 zO.184 0.6 4.5 -2.1 0.00290 524 ;0.636 13818.5 .085 b5.5 2.6 -1.6 5.00435 577 13918.5 .085 b5.5 4.5 -1.6 580 14030.7 .141 3.3 3.0 -1.6 585 14130.7 .141 3.3 4.2 -1.6 583 14218.5 .085 b;5.5 3.0 -2.6 589 14318.5 .085 b,5.5 6.7 -2.6 592 14430.9 .142 3.3 2.7 -2.6 597 14530.9 .142 3.3 6.5 -2.6 593 14649.8 .229 -5.5 2.4 -2.1 329 147

49.8 .229 -3.5 z2.4 .00409 331 14849.8 .229 -1.9 ;2.4 .00435 333 14949.8 .229 -. 5 p2.4 .00435 336 15060.0 z.276 -7.3 ;2.3 .00435 338 15160.0 z:.276 -4.8 ;2.3 .00418 341 15260.0 ;.276 -3.8 ;2.3 ;.00435 343 15360.0 ;.276 -1.3 ;2.3 4 -. 00435 346 15459.6 ;.274 -7.3 zt2.4 -2.6 ;.00435 599 15559.6 -. 274 -5.3 ;2.4 601 15659.6 ;.274 -3.3 ,t2.4 603 157

59.6 .274 -1.3 ;2.4 605 15859.1 .272 -7.3 -3.5 614 15959.1 .272 -4.3 _3.5 611 16059.1 .272 -2.3 ;3.5 609 16159.1 .272 -. 3 ;3.5 607 16230.9 .142 ;3.3 4.7 -2.1 545 .559 163

547 .636 164I ,I548 .675 165

.00357 554 .636 166

.00399 553 .636 167

... . . .00548 550 .636 168,- 19.6 z.090 b;4.1 4.4 .00392 555 .557 169 S

bz4.1 .00428 557 .636 1704.6 .00361 560 .636 171

b3.6 j .00466 562 .636 172b2.9 1 .00547 564 .636 173

38.0 .175 -.6 4.0 .00431 565 .559 174-.5 .00436 567 .636 175-.3 .00352 570 .636 176-.6 .00469 572 .636 177-. 8 ,.00547 574 .636 17

aX., varies with aTPP (see section "Testing Procedures and Measurement Accuracy").bAccuracy of estimated OLTpP deteriorates as V decreases below 20 m/sec (see "Testing

Proce(ures and Measurement Accuracy").

26

E

0 0

rN O w E 00 0I

Q~O(0.. 6I I

o Io

0

14 -

Lo L LO Lr)tn LO O 0 O 0

c~cjleinsgjc oilnooO

27

E 00 00

r , toII II

0 -

Eii4 C'4 CN C4 (N

a_Z - i- MC'0 7

0

o0L-(DQ-

00 00 0 00 0 00 0 00 00(NN N'(N(

28

0 00 0

tV)W E I I I I I

0 > 0 C

4- LO U,) LO U

CL > ui uiu iui

P 0

0

DCL

C,

U,0 UU 0 0U 0 O JU) 0 O UU 0U

Ddi '9.Iflss9ejd oijsfloo

29

EIi 0000

0 N

(D C Nco

0 0C3 0 00-

0 - 6 -

C (NN N (

CL .2 (n -nt

0

mmo

0

Z

00 00 0 00 0 00 0 00 0 0D

30

wmwwwu

E0

o- - 0 0

II I C4to c,4

0 - 6CNN

('O50 C .2 on Nn -

0

0

Flo 0l tou o to ~ -j a uu ,

Dd '~fl~e.J ~~fO~V31

N

"t toffJ I I I I I

co 0 to0

.0 . 0 -

a- (N X 0p

Z5. r- LO

0

0

to 0 t L o LO 0 Un LO 0 LtnLU) 0

32

E0 -

C-N I

0 W C- E 0

0 > N -

-4- toto wOtOt

Pj5~Q. .!? o=0-

0

-

NI-

o o 00 a 0c 0 c0 0 0o 0

33

E INII

* (O E6 0> ' 04 00

0- X" Cl 0 - N

a-P

LOD

co

It, 0 n Itu 0 LOt 0O LtU 0 LoUV) 0 "

C44C

Dcl l-isec oilsnoo

* 0L 0 0 L.0 .7

V - -) 0 o ,4 E 0000C111 C; 0 0 00

a).. o* 0)

CL .2 -pr-L

0

L

Nl-

to 0 uLO 0O LLnU 0n UM 0 Lnto( LOu

35

E

o "' .N - - -Ez- -- I I II

a- C: L

X 0

- - h

z~o~o 2 NC

U') to LO O U) LO 0 LnU') 60

o~j 9jnssaj :Di-noo

Li~lMA '. r A U)

E 0 0 0 00

- "t r)I I I I

.0

.2 o)) 0)

I.- Ic-

- o0

a)

000)

o~j tinssacl oisnQo

37

0 000 0o

0 -

S E I I

(0(

0 0 0 00 0 c 0 0 0

z3) 9rQ LO r) U L() l t) -

ocj ainsaidolls o:0

38

Q0 f14

0 0 0 00

0 0

00

0 00

0 ( 0

-n 0 L OL 0 0 L 0 n O 0 P

a.j ,g--jn s -jc -is o:

g: 1 ~ 39

it0

LO 0 0

000

ci)

a)

I-

I LO U 0 )L 0 I~ 0 InU 0o U)

40mu

3mt -w , zI. * v *-.~.~'

0 N

~W O O N- -t RtI

0 0 04 E0

II I

0~~~C .? ~N U ~

0

I L

0~~~~ 0 0 0 0 0 0 0 0 0 0

41

E

0 N .---

04~ E%, C0

Doo w

o- x .J-

-4-£- )< M- -

5 0: C .2 o .

0

0

d)Q-

a)

0 0 00 0 00 0 0 0 0 0 0 0 00

42

E

C C4 E I I00

I* It

4-

0

(00

433

00 0 0N--

* (00 00-o X - 0 N

Eii 0 0 0 0

0

co

(D

'~E

to) 0 LO to 0 to UO 0 'f uO 0 W()UO 0 if)

ININ I IN INIC INI

44

E

co~- 0 00

C I

E- U) a) Un) .1)

>C) N N_ N N

-00

o

IN

E.

C,

in 0 O Lin 0 L0U)O 0 LOinO 0 Ln 0 in

0 d 'JflS~~d !~SfO~V45

MO&M~m i f0

0 N 7 -7

C) Po 00 0 -C

U- to , I I I IN

U11 1 1 E C- -0 - 0

00

EV

000

w0

LO 0 ULO 0 LOu 0O O LOU 0 n ULO) 0 OO

d E~jnssajcj o!1sIncocV

404

mmE iow7m

E

00

12N 7

0 (D E

0 0 000 0 0 0

-00

'WV c

C)~

E

(0co

0_

04 in in 0n in LOL L OL

_1 N N N C,

z23()o. . oens-c ilsn

000

.0

0 - 0

0I II>11 04 C1400

-4 i) LO) If) fO IfO

00

?5 C) CL .2 cn r-to r

CLO

E)

LO LOLO L Ln n LOLO LC14 C1 N C-

leinsa-j oilno:S

N9

0 0-

-4- 0 00 0 000

0

CP

m-o

L

LO L to n LO 0 LnLO 0 tn L 0 L

ocj ainsai~j:Dilnoo

so)

E 0y 0)0

60.

-4 00 0c 00 0 0 0 0

N N cN N- Nf -%

1 00

0 N 7 - -4~)Ov)C"J C' N C14

0 0

0 - 6

E 2 2 20 0

0

co

0 -V

a)

LLI 6

0 0 00C 0 0 0 0 00C 0 00 0 00 V

Dd 'eaflssa.Jj o!1snolDV

52

AN nx AU -i

E

10

0 0 N

4- - - -

040

E~ 0

X ))

00

C).

0 0 00 0 00 0 0 0 0 0 0 0 0LO V Ln LflLf) LflL!) LO fl Lf

53

(-0

E0 0

0 000co

m Il

CL .2 cp LO

(D0

L

(DE.

CN

0 000 000 00 0 00 00(0 (D( w0( w0( w00

odj 'a-flSSa.jdj olIlsnoo

54

R07 p mS

000

C- 0; 0 0 00

0 (0

?5 0 0L .2LOt

cc0000 0 -

06j -isE-c -is o

05

II %V E 1.04a)

ES

0 0 0

0n r- -n 0 -l -

Lf t LOO) 1 1 1(No E toI

(0to000

M 0

U 4 CL . - - -

00

(D0

CD

0 0 0 00 0 0 0 8 0)

Dcj einsa-jc oilnoo

56N

. . . . . ..,

E 0 0 0

00

0 to 0 00

3 - - -

S.2? a) LO p.

0

,z

L

0)

0.4

0 0 00 0 00 0 00 0 00 0 0itO 0rL LO LO) tf) t) LO~t a) L

odj 'gjnssg-jc oilsfloo

57

E-0 0 000

(N (N (N N C

IL X

iC -M 0- .2

0

(DL

C.

0000 0 00 0 00 0 00 0

Dd 'e9jflssajd o!ilo:DVS

58

W-1111, r, -r P-r~x ?"LTILI

E00 00

0 N0

C\4 0 00

0ii >* 04')

.4- -- -

00

co

0

(D~

0 000 0 00 0 00 0 00 0 0(0 ((0 ( 0( (D LO0 (0 (0 (0

59

0 -

LC -tt

0 (D 0

0 I

-4- E -n -n

0

o

0

a)(-

0 0 00 C 0 00 0: 00 C 00 0 00'0((0 (.0(L (D Lo (D w

o0d 'a-flssejdj D!1lnooV

OWN E 00 0 0

~c igEI I I I

-4-- E N NN

X. C N C1 C C

I-~ 0CL~ .2 c'i N U,

0

-(o

a)

ES

0 0 00 0 00 0 0 0 0 0 0 0 00P.

61

10 0 o o 00N 7- -6

CN Nl N N

0 0, E 0000

> N - -N

I I I

00

.oO

-J-

U, 0 OL LOU" U"LC 0 -LU-) 0 l LO" U")

62

0 0 o 0 0

(0 00 0 0

CL liiiC cl C0 0

5QCL .2? cn N Lo to

0

-o

a)

a)'~E

r%

Ddj '9)jnsse.AJcJ oisno:V

63

%

, b-b

(-0 C1 C- - . .

C p 0

E 0 0) 0 0)

30 0 0 .

0 0 0

,~i~z0

-

LO 0 LO L 0 L LO n LOLO 004 C14C4 C1

c~cj jnssaci oisno)

00 -.

0 N . 1NC-'J (N(N-

ooC14j E~ I I0"~o E 0 0 Co0(0 0 0 0-

C4- CO COi CO CO

CL~ .2 LO

-0

- 00

- o

0 c o c c 0 0 0 0,C14 4 N 14 C14 C14 N

ocj a-in sa-jj oisno)

654

Iw

E

N 7 c' j

00 -- t 0 1 110. o , L 00

060

0 C4 - a

>c N N N C"J

0

L.

U)W

LOL U) 0 L n nL

% tn r0 rloPO 1)

oS a-n se.- isn o

Si6

LC)~ 'c N0 . - -

0 C C 4 E 10 00t

E0 o 0 0

_0

0

00

LO 0 uO LO 0 'L~ O uLO 0 LO to 0 U

Dd 'e.jfSS9eJd oSlooV

67

0 N---

M,; to 0('4C4C N Cun - 4 o , I I I II

0 CN0 (

E 0 0 -

4- ul) LI*) If) Uf)

0. i ) L6) If) i) ..

0CLf)t)

=00

(0

L

C)0 LOLO LOLO LO n 0 U) O Q

r~cj'e.Assail oisnoo

En o 00 0N 04 0 C

E-, -- r , I I I I

co 0o0 1 1

I11111E 0 0 0 0 0tnLf LA tn LO

0~0

0

-W 0(D

0 0 0 0 0 0 0 0 00 0 0 0 0 0C1 C'4( C1 N r

69

Lis -all 0

E

Co 0 o oN o

0 NO 0 0- E o0t> C CNI

E

CL .2~ LO to,

00

00

(D

I L

w70U, 0 UU, 0 U,, 0 ,U~ UUA0ll

I FmMWrgmr~lwruwAniW rt LR A 3P RMP PUNTniq m rt Pi nxUKJ~xm m. w .

E

00 0 0 (00 0

000

0 O(DN E

0 > C0

P =0

z ~ um-Y CL n

w~w~ .'IA A M M A M M MArMAM~ A ~ M M % R~ A I AM AM A AN M~A .A MA MA xxnjq U~M £P ?MA.

Eo 0oo0

0 - C

N 0~C)t~ E Io 0 I

-0 0 0-

00

a- )

P 0

U') 0 UO LO 0 U)U 0 to)U 0 LOU toU

72

IF-

E

0 2i 0 0 0 0(o N VN7

I I

E NN N 1

00 00 0000

co

.-

LO LnLO L 0 0 Ln L LOtn rn

Dcj q-jns9.ij oisnoo

73)

07-

E0C0, 0C0

0 NJ- -6N N *

r- o I III D E co

-4- 0 00

00

En

CLL x 0)Cl- 2 cnLO a

00

0000 0 00 0 00 0 0 0 0 0

74

0 00

Ln ,I I C%4

0 00-

0 C- 0

C%4 CN Na_)a_.

::3- t5 U 0- c) r-Ln t

LO

I I I

0 0 0 0 0 0 0 00 0 0 V

75

.............

E0 0 0-

4.- -~ (NN Cl (

C) 0, 1, 1,

00

.00

I L

Ddj 'G9jflssajcj osnooV

76

oN N1 0N C1 CN

E w 0o cc* 0 0

Q- X- N-

10SCL~O 2 U")

0

0

L

0 00c 00 0 0

77

%

E

0 0 0

(D 0

0< 000 0 0 60 6 6Zn 5nLO 0 a' LO~ -nL

ocj ainsE).jj oisnoo

(N% 0

T - 0- 0

0* 00 0

0 -1 1

X 39 -C

- r-

aa)

-- I

C-4 C4C C

ocj~~~.~ 9.nse.j isno

79

- 0 00

o LOJ 00 c~I Io

-4- 7 q N

00

0

0

a

800

k 0e 00 0 0it0 0

E00 -

ttoI I Ir0 c0 0 G

0 >- 0'

Q- C X Lri LA Lri tr0~

C5 ) 0- .2 r-- LO to

0

00

ocj enssa-cj oisna-

1

Lip 10

0 0000

(0 t~ ro 0 00 toCd 020

0)

0-

(00

0 0 00C 0 00 0 0 0 00 C)

82

E 0 oo0Cs- -N

oo 0(0 0ot

.0

~~5)Q .2 LOu-

(c0

L

Q)

0 0 00 0 00 0 0 0 Cl 0 0 0 0LOL0UO)OL L n O Lfl

od 'e.flssajdj oil.sfloo

83

0 0 0 0 0

E 0

00 - 0 00 C14 T 6

-4- x" C4 i c-i C c-i

0

coO

0.

()

CIL

0 0 Dd 0 0 0 0 0 0 0 0 00

o 'aeflsseid oi1lsooV

84

E 00 o to

0 1 .0

E t

0 - (N

L I L

.E >" 0 ) 0 0 0 0iq C4 NN q

oU 'ens-~jolno

0~85

000

E

~-4 -

- 0 0

3. 0 0

- ta)

cL CN

>D uj U.)n sac uilsno

86 Q Q . 0 *

00 0 0 0

(~o 0 I.0N C

- 00 0

0 1 ~ 1N

E o 0 0 00 0

a-) N-:iII I I II

00

0

0 0 00 0 C0 0 00 0 0 0 00

0dc 'einssa-jcj o!1looV

87

E 0 000

C;Cl CI

0 0CILC

P 0- 000CL .2 n - LO

-40-0-0 0 0 0 0 0a. LO ><') LO - n t- -O -n

ra. 9jn s -c oln o

88~~1

E 0 0

to 0c 0 0

0 00

c II

0-

-u

0 00 co 0 00 0 0 0to.

'e.A ssajj Disno)

8)

t , E0 o ~ 0D 0oc

E0

0_ 0

0

Q.-

C; 0

900

VN wvwwliI w mTM m IF WR JK-JRr~mr S

E

E (0

> N - 7

0 I0

0 >

0

(D0L

(D)

U,

U-) 0 LnU 0 Ln U-) 0 LO U') U) LU') 0

Ddj 'e.flssa&jd 5!ilnoV

9mo

Eo 0 0 0 0

Pr) . E - 0000 to0_ - - o - r -

E LoN O nL

a_ X

25 0 C0 .2 mt

0 I 0

n- I I I I I

co

0

Q-

(NJ

L J I II.

td -insseicd oilsnoDV

92V

. . . .. ... .

E

0NO C14 - C

oCN T; 0

01111 E 0 0 0 0 0

(0

U) 0 LO to 0 LO U) 0 LOU 0 0 0U) 0

r-dc 'a-flsse.Acj oilsfl0oV

E0 0 o 0

C~LO N C1 NC 1 I

c)) ro D I I I I

C 0 0-0 N - 4

lilli E 0000

0

0.

()

0) 0 0 0 0 00C 0 00C 0 0 0 00pe N I Ile

o0d 'teflsse.id oloov

al4I

1 0 0 0 00

0 IN IV.- ,)a '(tt CACE C l

q 'tf .01111100 - 0

(iDll DOo 0 0000 4- > 0N 0004

0 0

Q-o

coO

0.

00 0 0 000 0 0 0 0 00;

Odc 'e-flsseid oilooV

a*0 0 0 0

() q*I I I II

IIII E 0 0 0 004-to to to wot

0-, uw vii v-iu

co

-J L

C4

Dd 'einfssO.Ad !ilo:DV

96

Ei0 0 0 0 0

00 J ~ r- . I VIU I II

00

a--

0 I-M

CL~ .2 -O

0

co

c)

0 0 0 0 0 000 0 00 00

Ddj 'eiflsseJcl oisoD

97

E

N % (U-) C1 (0 N (NOC) 01 L)u) III I I

0On O(D 4) E 00 0o w0 0 0 0

CL 0 00

0

0

CD

0 0 00 0 00 0 00 0 00 0 0

98

E

00 Er I I I I

C 00-(

-4-4

a-a ~. LO, N

0

-W0

0 0 c0 0 00 0 00 0 0 0 00

~dc 'einsseici oisno

99

Eit 3 0 0

oaC-4O ("4 0 *NC

0C OU-r)0 000

U~C 0 0

4Q 0) M 04mCa_ I

?5C)CL.2 cy r-

0~0

ZC9~c~c0

0

-o

C;4

100

Ii 0 000 N 7

r--oo r-) LO cc N N C C1 100 .qt R I I I I I

D O0Eto 000t

C! 1 0

LO LO_ too

a- c X0

_00

coO

0

Q.

Nl

0D

101

E0 0000

ff - -t

Vo N o" 00

00

0L 0 ) 00

-W0

-(00

102.

1v -,I)

E0 0 0 0

0 CN N CN CJ (N

0 (o ,t E w-000

E o o 6 0)

00

0a-a1)

-

(D

0 0 0 cc 00 0 0 oS;

Dd '&.jfss9ejd o!il:v

103

61J W i I ~MA 1 K E ~M~ .E~ P W

E

- 'I to-IILo to E 00

06

E

00

(D 0

L

'~E

0 0 00 0 00 0 00 0 000

104

E

r- 0Y 0 0 C4C C

-t NO -

(N (.0 Sr -t 0 0t

00

Eo

* 0)

0 0 0 cc 00 0 0 0 0 c

zZtOn NO? to In e r)W)W

105

L.V.

E00 0 0

oD NN 0 - C- C

-- O ,I I I I0)Q(0 L E n 0 c

0(

0- 0 0 0I0

5U CL .L:? 0) I, FOt

0

00

NU,

0)

ES

100

UNNUMNUEZ NVUDA

Eo 0 o

0 Nx

"t 0 110d E 0 0 c

CN -* >- C0 00

C* 0' OO

f-I-1 0

i -)2C .2 ocn

00

(0

0.c

0 0 00 0 00 0 00 0 0 0 0 0

107

E0 0 0 0

Ln P~to o E I IC 1 0 CD

0

G! N 0!-

0- x" 0 0 000

MCO

0)

0 0 00 0 00 0 0 0 0 00 0 0

108

E0 0

C- -~q 0 0. 01 4C

o a 0Q C;. 00

E totow

00

-0

(D 0

0 0 00 0 00000o 0 0 0 0 0if nLr) LO'AL n OL

ocd 'eilssaici Zo.l03V S109

2 11,111,111,11

Et 0 0000

0 N3 ---

-1 00 0 N CN 0

O U0 L) E 00a - 0-

- CN -_

0 0

E to toto to t

Q_.

0

00 00 0 00 0 00 0 0 0 00

I ~ ein s -. I Inoo

110

E

P -0

Z 50 M N. L e

.0 00 0 0 0 0 0 -

to- w ( L to w wo w

Dc. ><.j s a-~ 0 0 6 0

E~ ~ 0 0

EN) N WN (D CAU * C

-tr)-tI I III0 -- 0 00

)- - 6 -

a- c X ciC -

Z Z5 :M C .2 uO W-

co

0

a-

(,

U"O 0 LO LO) 0 O" 0 Lnu"O 0 LOu" 0 O)

Ddj 'e-nssajc-j oiIlooW

112

0 0 0

To 0 Nc

E > C1 C.. C14 -

a- c

0~0

I- I-

Z~o~L .! N-E

0 0 0 C 0 00 00

D cj 9.j s sc-). cj ilstoO)

113

E

0) 00

No o o(

0 o E (00 0 0003.

0~ )- elC0C1 C1 -~ 1 1

1111111i 1 1111hl

E

o) N00 'a~~r. I II I

N) C r-)(0 0. "t E w 00t

0

0

0 0 0 0 0

I- Q-

ZrQ(Q .2insa~ oolno

01

0 0 0 00N CJ C'4

0)C'L- 1 0

00

CL3

coO

-

00 00 0 00 a 0 0 0 0 0 0 0

116

0 N-

E

0- a) 0) 0I 00-04 -'

0

0 0 0 0 0 0

0

-o

a-

o 0 00 0 0 0 0 00C 0 0 0 0 0

0dc 'einssajcj oilsnoov

117

qmxzww~mMOVIMM0

E00 0 0

o E -o0 0t

'- CN C'

0 1 1

0- x-T

CL .2 o- -n rn

0

coO

(D

a-

0 000 0 00 0 00 0 00 00

118

0 0 (Dt E t 0 0 0L

06 -7C

0 1 1

111111~ E 0 0 000

iz 5 ) C .2 LO to

0

0 0 0 0 0 0 c 0 -Qtn DO

ocj 9.jn sa-jj oisnoo

119

0 E 0 0 0 0

C E (0

00

0

-

120)

-511

E

0- 0r 00 01 01

N "o 00 1N 1N 1

0 o"tED 0 0

0 1 1N

0 0 (

:ti CL .2 (N

II II (N00

0

L.

(D

(D

ES

UO 0 n LU 0 O LOU 0 n UO 0 LOU~ 0 Lf

121

000 0

C- CNI CN C1

E) 0

0 0 0 00

o0111111 E c,0

I~f E5 --

'D0

(D

.

E~

0, 0 Ln to 0 LO U, 0 LOU 0n U,)O 0 U

122

w rvkgiuUW RI enw~

0 0 0 00N 7 - - I

0 NO E N0

0 0 - N

IILOt

0

vc

'a-ins~a-jj :Disno-

123

KJKI%13mF~glrvwu Ial F~taxpw N"

E

0 0o E 0 o 000

0

0

11 11 1 mC C .2 -~ - -O

0

C1O

C.

Lin t 0 L Lin n toLn -cq IN 4 rJ IN I

o.1 einssei~ oiln0)

124t

o0 0 0

V ) L N toA~ I I I I I

0 ( N E D o 0 0

0

CL .2 c - OW

(D0

a

(D

jL0 0 0 0 C) 00 0 0 )14 0.

D C] einsejcj:DilnoaD

125

E

0r 00 0 0 0

00F"n I I I

0 (

E;0 >~ C',

z~~5OCL .2 o '

_0

0

(D

-o

oj a-nsse-cj oisno-

UUl

- N N

E cpC) r00

3* 00

11111 C E .2 0 0

0

-

(DE.a)-

0 0 00 0 00 0 0 0 0 00 0 0tn LO U) UO LO ItL()L UU) iL

o0d 'e..nssa-i~ !ilno~v

127

E

00- 0 0 0 00 -14, -~ 0

cN 0 0 0U-) E coc00

CL3

0 m -(

0

(00cl

0 00 00 0 0)

Dcj einseicioils oa-

128)

E

m 0 00 -

C- - 0 0 0> NN N N

0 1

.E c- NN -N 01 C4

0lii UN L .2 Nn N

II II co

0

000 0K0 0 00 0 0

odj lensac clsnoov

129

0

E0 0- 0 0

00 (D m C14 C14 C14

0 to0

C '000 0 0o

X~ it

05C l .2 U')-

0

(D

a-N

to) 0 LO to 0 Ln U') 0 tp ) L A LO 0 )

130

0)io N) 00 -3 CA- N

r,- - N to I I I II

o Ln E to000

1 1 1 11 1 1~)t t i

E4 to NO W) PO L

F- 0

co

(DE-

C

0 0D 0 C)0 0C 0 0

'c e.flsseij o!1sI1oV

131mo

.- k

E

0 0 0 i -

CN CN N ('4N)l N I I I I0~ U)~r 00

Co0o > ; I

0

co

0

L

LO 0 LO %j LOLO 0 Ul) O 0 l) L

Dcj einsaicl:Dilnoo

132

Ei00 0 0

o Ln E

00 000 C14 B

5~~.. .2*.p-.Or

0

% I---I

od 'eiflsse-ic oilsnoV .jk

133

E0 0o0 0

o N C4C C 0D )o)NI I I II

0 0 U-C) E w 0 0 00 t0 0

0 0 0 00

00

(o0

L

5-5 %

E

o0 0 N V

0 oc LC) E (D00- 00 0

0I 1

Q- X 39

=00

-W(D0

CL

(D

IfO 0 If)LO 0 Ln LO) 0 LO LO 0 LOt LC)

Dd '8fSSn 014.SflOWV

135

Co No -- to

c'i -7 .

II I I I

* 00

.L) -0 00

o - 6I a

(00

LL

1362

zt0

E

00) CP'14 (N CN14(N(0 3 0) E .

. . 00-

0 >(: , -

a- -

Zi2 L) CL .2 on r- -e

cop

0

-o

L L -1

137

N00 t 0 0 0

OC E' re N I I(0 0D U t D

00

0 0 -

o - (' - -E'

0

("4

0 0000 0 00 0 00 00N\ C'J'. (NNJ('4 C4C' N('

Ddl '9.flss9.jcj Zfl.sfloo

138

0 0 0- t 0 0-o N -9 CO 0O(

0> C4 CaC

4 totot

00

cJ)

0

CD

LO 0 O uLO 0 'Iou) 0 tnl to LOU 0LO ~

Od '9flSSJd ~fl~V1391

%0

00 (000

0C 000 Ln E 000

-4-* !

0. .C

a.

(D1

cl.

ES

LO) 0 LO IfO 0 ULLn 0 LO LO) 0 LO LO 0 C

140

()0C: co 00 0 0 0

E o 000 00 0

* 000

o > N I

11111111

-. 4-~~~ 0 0* ~* 0)a. ~ NN N N%

oc .ns-jjolno

I-141

%

*ll~

-c t %

0 00 0

0 co

0 4- > CC'.J

C L4

0

-(00

L L CL0 00 00 0 00 0 0 0

ocl ,9-nssaj~j:Dilnoo

142~

'1

0

N LO

-4- 0tr 00 0 01

r0- 0 r U)000

C0'

00

LOo

00

Q)

00 00 0 00 0 00 0 00 0 00

Dd 'a-jfss9.jd oilsno1DV

143

0

qmvw9 lllvm Ail"OlinW MNJT-Ilr M M~mxVZ& " m wi o p-.A V Am-MX-TMOVXF rclr ) x~rxrL,%~rT W) 1

E

0 (0 0 00

o N (D to(0-Ln ,t NL)c%%4 N (N C

C) O'(DLf)0o 0

I I a (

H ljll E o 0

=00

U-))

0.

(D

(N

0 0 C00 0 cc 0 00 0 0 0 0

Dd 'ajnss9eJd o!1lnoV

144

E0 0 0 0

0N lp to to W9t

0 L E t o I00

to 0 toC

00

0 0 0O ('1 n - O n 0 L

)<~C C C. e'

oa aiseiloln o

/114

II-

.0. e

IrI0 N

* U-) (0 0 ( (

0 1 1

4,

CLI .2. 4OW

>< (0

-

LO~~~~0 U' A, L O 0 L L ' l

OLL

E

0 0

o 0 0 0

00

_00

00

Q)

0 0 00 0 0)0 0 00 0 00 0 0~

ocd 'a-flssa-jd o!1lo:DV

147

% % %

0 0

(0 00(

0I I

1111 1 E co00 00 00 00

00

(00L

I.-D

E0 0 0 0 -

00r 0 N CN N C

o Eo 0 0.0 0 0

0I It0-

-4--

NNN

(D

LL

r0 <

Dd 'enss,9Jd oisnoo

149

r--) o

0 0 - N

Lfl LOl Ln LO LO

X it N N N- C

- c

0

- to 0.

(00

o~j -inse.Ad oils oa-

150~

E

OQ- 0 0

No N - 6

-4- *0 tN I I

0 C 0

-00

0

00

.0.

0 coca 00 0 00 0 00 0 0

Dd 'aJflssaicd o!1snooV

151I

7E

1 0 0 0 0 0f O ., , N 1 7 -C4C

0 (N

00

LL

E

o Do 2 .00

E to to Ewt

i062 L 0.0

0

L

0 0 0

153

00

0 T

~ E

0 N 0

E ~ (0

154-

E1 0 C0

OLD U 0 000 000 *0 (

00 0C43(

Ii ~ E

0~

Z~Q Q. .2 cro -

0

.00

L L.

Ni

E 0 000N -reN CN (N (N

U) oII IIO((DE oo 0

06 q 000 14C

C;iE4

(N (N to (

0

00

I L

156

%0

E

110 (0 o (0r4CZ -I to to to

0 00 -6

00 w

C 03

CL.

E.6

W~) 0 O t 0 0J LO 0 tLO) 0 ULO L 0 U04N NC4 C4" C4JC4 C C

1 5 7Iv %

%S

anaj .J') SCn r5nSSRMtCMU ~NwraU U i ~ mS E~p W ra

00

o 00 o o0c(0

0 .- 0n -' n O

M: 0

'E

tO 0 UO 0 n iLU) 0 U) 0 f uu O'

Dd 9.jnssajcj oflsoov'

158

7 ;: S:S:: S

0 0 0 0 (0

kN -

E 00 0 00

0 C

00

.2 o)r- -Q

00

159

E

C~L toDtO

E-4 O LO LO)U)U

a_

0

co

-o

0 00 00 000 0 0 0 0W) t Pe)tn P) N

Dd 'enssed oisno,

160,

IrS

- a - - wZ W, v

0 (0

c.' C"' c'.C EI I ot Ih

co0 00.0 90 0

.2 p - 0O - (

-4- in LO 0 nU)U- 'n LO 0 n

~~161

S0 (0 (0 (0

nz~~L~ C',J C"

r- o I

Z 0 C4. C

m-o

0

Q,

C (tf) C )) 0 u)) 0 U le) Pei)

iDd 'ajnss9ijd 9!1l0:DV

162

E

0 N 7 - 1

0 0ODo~ 0 0-

(N

Nt C) CL .2-

0

.0

a)

a)

(N

1634

1163%

E 0 0)

o N 7

* 0 (.0 U- o0- 0 0

0 C; 6

II Hfl" E q~. . 4

0

00

L

LN qo) 0 0 0 0 00 0 0 0 0 0 0 00

Dd '9.jfSS9ejd 3!1loo~V

164I

0 0 0

X P

(N (D

'0.0 00 0 00

0 >9. n s 6g c- o(N noo

- N N N165

a.z ,V -

E0

In L I I I

F u) 00 (cc)0o C- ;

0

Lo L U-)Ln U) U- U-

Dcj linssecj oi(00o

166.

00

N E 0 0- 0) 0 C C

o u -) to 0-00t

* C 0 0-

~ 0CL . LO to

0

.-tJ

a)0-

Nci,

187

vw

- WAX

E

o r 0 -N -1 - 10N (NJ co'c

Cd .; 0 0 0-

CL x

(-: L .2 01 N U)-

0

o

(DL.

C)

0 0 00 0 00 0 00 0 00 0 0C14CN (NJ C14 (NJ 0

Ddl 'e.flsseaid Zil.sflo3v

168N

(0 co 0 0

ONO~Mf e'jNO

a- X)0 )0

0

co

0

L..

- -- co -0 0 00 0 0 011

0dc ',g.lsse-jcj oi1looV

169I

E0

(N (N (NC 0

0 000 10I1 1 i ET 0

E< 0

0

LO~~~~~~ ~L -nL OU) 0 nL oV

oci -insajcjoils oa-

170)

000 0

C'4 C%.J C%

0 -) r- I I Ie

00

0~0

-o

(00

LL

0 0 c 0 00 0 00)

C4C'4 ('4 NC4 N

ocd 'einssei oL.lsooV

171

' 0k

L ORV' ~ A

0 0 000o N -

0 O W U-) to0 0 0 .C* o ) 0, 0 0

0 yN 6 -(

11111o 0 0

CL~0~ .2 7, LO

00

00

.

172*

C-) uVO~ C -N -

LO (4 I I I (I

E 0 0

00

-(0

to) 0 LO 0 0LO( 0 UL L 0 LO LO 0 it)

Ddj a-inssa.Ad oilnSo

173

E0~ 0 0

Ln (N 0) (N) (N (N

r-o t -) Lo I I Io71 u'-)U E cCd C; 00 >- C4, Q-

I11111 E ( 4N (N (N-4-0 0 000

C.CD

0 0 0 0 c 0 0 00 0

.

Dcj 9.jn s9-J oilnoDO

174~.

E

00

o - -(

0 0~ E 0 0

00 (D

C 6 1C 00 > C14 .5

E '1$CN 04 CN (1

CL5CL X-

(uO

o~j ainsseid oisno-

1-5

(Ill

FIX'

FI010 00

N

r- o r - I I0 L) E to000

>- C4c

C. 0 0

z~j5(~cLX

o) 7O

cx;)

N-

2 220 0 0 0 0 0 0 0 0 0 0 0

r-)cI IEj s a c cIln :D -

17

o -- tNC C4Co- 0 oq to o"II

0' ('D C'r E' 004

0 00

EI N~ E1 C (

(-):2 C .2 an W-.-

0

-

0 0 00 0 00 0 00 0 00 00

1771

WM0

r~'Z. r4wJfltSA~I~f~rf. .. S. bfJ,~SllS~.f~fS M *7

E00 0 0 00-

N N .1

r- DL P)rI I

0 0 0

1 1. - 1

0 0

0

(D

tf) 0 n toLf 0 IU-) - Ul) fl) 0 - U-U) 0

Dd 'e.AnssEldjc oilsfloo

178I

NReport Documentation PageSOWe Ad'-straton

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.NASA TM-4024AVSCOM TR 87-B-4

4. Title and Subtitle 5. Report Date ,

Acoustic Measurements From a Rotor Blade-Vortex Interaction March 1988Noise Experiment in the German-Dutch Wind Tunnel (DNW) 6. Performing Organization Code

7. Author(s)

R. M. Martin, W. R. Splettstoesser, J. W. Elliott, 8. Performing Organization Report No.

and K.-J. Schultz L-163689. Performing Organization Name and Address 10. Work Unit No.

Aerostructures DirectorateUSA XRTA-AVSCOM 505-61-51-06Langley Research Center 11. Contract or Grant No.

Hampton, VA 23665-522512. Sponsoring Agency Name and Address

National Aeronautics and Space Administration 13. Type of Report and Period CoveredWashington, DC 20546-0001 Technical Memorandum

and 14. Army Project No.U.S. Army Aviation Systems Command 1L161102AH45St. Louis, MO 63120-1798 ___

15. Supplementary Notes

R. M. Martin: Langley Research Center, Hampton, Virginia.W. R. Splettstoesser and K.-J. Schultz: DFVLR, Braunschweig, West Germany.J. W. Elliott: Aerostructures Directorate, USAARTA-AVSCOM, Langley Research Center,Hampton, Virginia.

16. Abstract

Acoustic data are presented from a 40-percent-scale model of the four-bladed BO-105 helicoptermain rotor, tested in a large aeroacoustic wind tunnel. Rotor blade-vortex interaction (BVI) noisedata in the low-speed flight range were acquired using a traversing in-flow microphone array. Theexperimental apparatus, testing procedures, calibration results, and experimental objectives are fullydescribed. A large representative set of averaged acoustic signals are presented.

17. Key Words (Suggested by Authors(s)) 18. Distribution StatementRotor acoustics Unclassified - UnlimitedBlade-vortex interaction noiseAcoustic directivity

Subject Category 7119. Security Classif.(of this report) 20. Security Classif.(of this page) 21. No. of Pages 22. Price

Unclassified Unclassified 181 A05NASA FORM 1626 OCT 86 NASA-Langley. 1988

For sale by the National Technical Information Service, Springfield, Virginia 22161-2171