Document
NASA Technical Memorandum 102250
Lateral-Directional Stability and
ontrol Characteristics.ofthe Quiet
ChortHaul ResearchA_rcraft (QSRA)
Jack D. Stephenson, James A. Jeske, and Gordon H. Hardy, Ames Research Center, Moffett Field, California May 1990 National Aeronautics and Space Administration Ames Research Center Moffett Field, California 94035-1000 NOMENCLATURE ay lateral acceleration, g b wing span, ft ram drag coefficient Cms rolling moment coefficient lift coefficient
cL
c. yawing moment coefficient
thrust coefficient
cr
side force coefficient
cy
aileron BLC momentum coefficient (written as Cmu_AIL in table 3) acceleration of gravity g Ix, Ir, Iz moment of inertia about the X-, Y-, and Z-axis, slug-ft 2 Ixz product of inertia, slug-ft 2 aircraft mass, slugs aileron BLC nozzle mass flow rate, slugs/sec mj engine air mass flow rate, slugs/sec roll, pitch and yaw rates, deg/sec or rad/sec p, q,r dynamic pressure, lb/sq ft S wing area T engine thrust, lb V true airspeed, ft/sec Vj aileron BLC nozzle flow velocity, ft/sec W gross weight, lb SWA reference area for defining Cu, sq ft X_, Z1 longitudinal and vertical distances from the engine inlets to the c.g., ft angle of attack, deg sideslip angle, deg or rad aileron deflection, deg or rad 6R rudder deflection, deg or rad _s spoiler deflection, deg or rad Sw wheel deflection, deg
¢ roll angle, deg
(') derivative with respect to time Subscripts initial condition O based on estimates e Abbreviations BLC boundary layer control DLC direct lift control USB upper surface blown (flaps) III PRECEDING PAGE BLANK NOT FILMED Symbols identifying the stability and control derivatives in the figures are defined as follows: act
c,,, =_,, c,,, --9 c,,, =
c,,,,=_ c,,,, =_, c,,,,,=_
=..___t =ac. Cv_s =a_.__ Ct_s 06s Cn6s #6s 06s Cn_ = #C #C
_-_+ _
C,_ = a_-j' + -_ c, The column headings in tables 2, 3, and 4 refer to the stability derivatives listed above as follows: CLB = Clp CNB = C,_ CYB = Cvp CLV = c,, CNP = C,_ CYP = OF, CLR = C_ CNR = C,_ CYR = OF, CYRUD = Cr.t_ CLRUD = Cz._ CNRUD = C..t_ CLAIL = CIsA CNAIL = C.,A CYAIL = Or6A CLSP = Otss CNSP = C,_s CYSP = Oy6s CLLAT = CtLAT CNLAT = C_T CLSD = Ct_ CNSD = C. 6 The last two of these derivatives are in units of (rad/sec) -l . All of the other derivatives are given in (rad) -1 .
iv SUMMARY This report presents the results of flight experiments to determine the lateral-directional stability and control characteristics of the Quiet Short-Haul Research Aircraft (QSRA), an experimental aircraft de- signed to furnish information on various aerodynamic characteristics of a transport type of airplane that makes use of the upper-surface blown (USB) flap technology to achieve short takeoff and landing (STOL) performance. The flight program designed to acquire the data consisted of maneuvers produced by rudder and control-wheel inputs with the airplane in several configurations that had been proposed for landing approach and takeoff operation. The normal stability augmentation system was not engaged during these maneuvers. Time-history records from the maneuvers were analyzed with a parameter estimation proce- dure to extract lateral-directional stability and control derivatives. For one aircraft configuration in which the USB flaps were deflected 50 °, several maneuvers were performed to determine the effects of varying the average angle of attack, varying the thrust coefficient, and setting the airplane's upper surface spoilers at a 13 ° symmetrical bias angle. The effects on the lateral characteristics of deflecting the spoilers were rather small and generally favorable. The data indicate that for one test, conducted at low thrust (a thrust coefficient of 0.38), compared with results from tests at thrust coefficients of 0.77 and larger, there was a significant decrease in the lateral control effectiveness, in the yaw damping and in the directional derivative (C,_). The directional derivative was also decreased (by about 30%) when the average angle of attack of the test was increased from 3 o to 16 °.
INTRODUCTION The Quiet Short-Haul Research Aircraft (QSRA) was designed and built to provide flight experi- ence in a program to study the characteristics of an airplane employing the upper-surface blown (USB) powered-lift concept. Flight experiments were conducted to acquire data that could be analyzed to provide longitudinal and lateral-directional static and dynamic stability derivatives for the airplane without stabil- ity augmentation. Results of these tests to determine the longitudinal stability characeristics have been reported in reference 1. Results of the tests to study the lateral-directional characteristics are presented in this report. The tests covered a range of engine thrust levels and airspeeds, in several configurations that had been considered suitable for landing approach and one configuration considered optimum for takeoff.
Time history records of the airplane's response to rudder and control-wheel inputs were analyzed with a linear-regression parameter estimation procedure to extract estimates of the lateral-directional stability and control derivatives.
THE RESEARCH AIRCRAFT A three-view sketch of the QSRA, with dimensions and areas of various components, is shown in figure 1. Figure 2 is a photograph of the aircraft with the flaps and ailerons deflected to represent a landing approach configuration. References 2 and 3 provide illustrations and other information on the control sur- faces whose aerodynamic characteristics were investigated as part of the flight program described herein.
The wing of the aircraft was constructed with the USB flaps extending spanwise from the fuselage to 47% semispan. The ailerons, which have upper-surface boundary-layer-control blowing, extend from a span- wise station at 70% semispan outward to the wing tip. The pilot's control wheel drives a dual hydraulic tandemactuatorto operatethe ailerons.Betweenthe aileronsandthe USB flaps, the wing is fitted with conventionaldouble-slotted trailing-edgeflaps.
Uppersurfacespoilersconsistingof two surfaces, an outboardandaninboardsection,on eachwing
panelarelocatedaheadof the slottedflaps. They areoperated differentially by control-wheeldeflection throughhydraulicactuators to provideroll control,augmenting thatof theailerons.Figure3 showsa static calibrationof the deflectionanglesof theaileronsandthe spoilersasfunctionsof thecontrol wheelangle.
Also, all of the spoilerscanbedeflectedtogether(symmetrically)to providedirect lift control (DLC) in additionto their functionas a lateralcontrol. The rudderon the airplaneis double-hinged, with the rear portiondeflectingup to 50° (measured from theaircraftcenterline),twicethatof theforwardsection.The airplanewasfittedwith a noseboomonwhich weremountedanangle-of-attack vane,a sideslipvane,and pitot-staticinstrumentation. Instrumentation for acquisition of testdataprovidedfor onboard recordingand telemetrywith ground-based recordingof morethan100variablesat ratesof 100Hz. Beforeprocessing thedata,however,theframeratewasreducedby decimationto 20Hz, andthe analysisof thedatais based on this rate.
FLIGHT EXPERIMENTS To obtain the data for this report, the pilots set the requested airplane configuration, thrust level, and airspeed and then executed maneuvers produced by rudder and control wheel inputs. For most of the tests, the motion was excited first by a rudder doublet and then, after a brief time interval, by one or two large amplitude positive and negative wheel excursions. An example of a time-history record from a typical maneuver is shown in figure 4. A few of the maneuvers were responses to wheel inputs only. For all maneuvers, the normal lateral and directional stability augmentation system was turned off. Also for all of the maneuvers, the slotted flaps were set at 59 ° with an aileron droop angle of 23 °. The majority of the tests were performed with the USB flaps at 50 ° and with the DLC spoilers undeflected. For two of the tests with this USB flap angle, the DLC spoilers were set at a bias angle (of approximately 13 °) and kept at this angle, varying only with the aileron deflection as a lateral control. In addition to these tests, two were conducted with the USB flaps undetected, representing a takeoff configuration; two tests were conducted with 31 ° USB flap deflection; and one was done with 66 ° deflection. The maneuvers were done at constant thrust and, to the extent that was practicable, at constant angle of attack, as indicated by a cockpit display of the a vane angle. Strip chart plotting of telemetry data during the tests allowed ground monitoring of some of the variables.
DATA REDUCTION AND ANALYSIS In the appendix, the equations used to correct the air data measurements are presented. Angle of attack vane measurements were corrected for induced flow angles with equation (7), which was determined empirically from measurements of pitch attitude and flight path angle. Equations (8) and (9) were used to calculate, respectively, the dynamic and the static pressures corrected for position error. A correction to the sideslip vane angle measurement was determined by using the calculation described in the Appendix from reference 4, in which rates of change of side velocity computed using the equations of motion are compared with rates of change of side velocity calculated from the vane measurements. This correction consisted of applying a factor that reduced the measured sideslip angle by 6.5%, for all of the test conditions.
Otherquantitiespertinentto the processing of the data, thrust coefficient GT, ram drag coefficient Con and the momentum coefficient for the aileron boundary-layer-control flow G,, were calculated using equations (10) through (13) in the appendix. The data records were smoothed and filtered with the prepro- cessing program as described by R. E. Bach, Jr. in "State Estimation Applications in Flight-Data Analysis (A User's Manual for SMACK)" (NASA RP, to be published) (where it is included as an initial step of a state estimation analysis). Also, as part of this preprocessing program, angular accelerations needed in the equations of motion were calculated, as the time derivatives of the pitch, roll, and yaw rates. To obtain the lateral-directional stability and control derivatives, the linear-regression parameter estimation procedure described in reference 5 was applied to the smoothed data records, with the following equations assumed to represent the aircraft motion.
Equations of Motion The following equations of motion used in the analysis of the data are expressed with reference to the airplane body axes. It is assumed that the airplane is a rigid body and that the pitch rates are small.
rng _-ffay = Cy - CDr sin fl (I) Ix [p _ Ixz .1 = Ct - CDR _ sin fl (2) Iz XI [÷_ Ixz_] -_ --_-z i., = C. - CDR _- sin/3 (3) where Xz and Z1 are, respectively, the averages of the X- and Z-distances from the engine inlets to the c.g.
The moments of inertia, Ix and Iz, and the product of inertia, Ixz, are plotted as functions of the aircraft gross weight in figure 5. The coefficients Cr, Ct, and C, are assumed to be given by the expressions 4 _Cy 4 _Cy Cy : Cy, + E--_ (, + E --_j rj (4) i=I j=l 40Cl 4 0Q (5) i:1 j=l 40C. 40C.
(6) c.:c. + + E -ff ; e, i= 1 ]= 1 The state and input variables, (i and dij, are defined as follows.
2V 2V 61 = 6s - 6e_ 62 = 6A -- 6Ao 63 "- 6S -- 6S0 64 = _S RESULTS The aircraft configurations and flight conditions for the tests that provided data presented in this report are listed in table 1. In the first column, each letter, A through E, identifies an airplane configuration, as determined by the deflection angles of the USB flaps and by the symmetrical deflection of the DLC spoilers.
Tests A1 through A7 were done with the USB flaps at (nominally) 50 ° and with the spoilers undetected.
Tests B1 and B2 were done with the same flap angle but with the spoilers deflected as DLC devices 12.1 ° and 13.2 °, respectively• Tests C1 and C2 are with the USB flaps at zero deflection, D1 and D2 are with these flaps at 31 °, and E1 is for a 66 ° deflection. The second and third columns in table 1 indicate the flight number and the order in which the maneuver was performed during the flight. Table 1 also lists the thrust coefficient, lift coefficient, equivalent airspeed, and altitude at the beginning of each maneuver and the average angle of attack and gross weight during the maneuver. The rolling moment, yawing moment, and side force derivatives with respect to sideslip, roll rate, and yaw rate, from the parameter estimation calculations, are shown in table 2.
Table 3 presents the derivatives with respect to rudder angle, aileron angle, and differential spoiler angle. Rudder deflections are measured on the forward section of the double- hinged surface. For one test, C1, the rudder-effect derivatives are omitted because the deflection angles in the data record were in error.
In three of the tests (A1, A2, and D2) the rudder was not an input. The rudder derivatives for these tests are shown in parentheses and were entered as fixed not estimated values. Also, fixed values were entered for the derivatives representing the effects of the spoilers (employed as lateral control surfaces). The time- history variations of the spoilers differed enough from those of the ailerons that by including these controls separately, a better fit of the measured and computed accelerations could be obtained. The differences were not large enough, however, to estimate both sets of derivatives. The differences are due to different nonlinearities in the variation of these surfaces with the control wheel deflection and to different lags in their hydraulic actuator systems. In table 3 the column labelled Cmu-AIL is the momentum coefficient of the aileron boundary-layer control flow C_,.
Some differences in the effects of the lateral control in different maneuvers were observed to be as- sociated with the magnitude of the control deflection employed to excite the maneuver. The maximum angle of deflection of the control surfaces influenced the relation between the aileron and the spoiler de- flection. Table 4 shows the maximum deflection angles that the spoilers reached when the control wheel 0c, 0__Ca input was applied. Also in table 4 is a column with the heading CNLAT This is the sum of . and ., an • 0_^ 06_ approximate measure of the variation of yawing moment with the deflection of the two control surfaces, the ailerons and spoilers.
When the ailerons and spoilers are deflected for lateral control, the resulting change in lift distribution of the wing produces changes in flow angles at the tail. These changes together with the effect of a lag between the time of the surface deflection and the time for the changes of the flow direction to reach the tail are accounted for in the equations of motion by including the term with 6s (the rate of deflection of the spoiler) as a variable. Table 4 shows the estimates of the yawing moment and rolling moment derivatives with respect to this variable.
The variation with time of the rolling-momentcoefficient,the yawing-momentcoefficient,andthe side-force coefficientwerecalculated from the datameasurements for eachmaneuver. Plots of thesevari- ationswerecomparedwith plots of the variationsof thesecoefficientscalculatedusingthe valuesof the derivativesfrom the parameter estimationsolutions. An exampleof this comparisonis presented in fig- ure6. For all of the maneuvers listedin thetables,the time historiesbasedon the measurements andon theestimates werein goodagreement.
DISCUSSION Lateral-Directional Stability Derivatives In figures 7, 8, and 9 the estimated values for the lateral-directional derivatives listed in table 2 are plotted as functions of angle of attack. In these plots the angles of attack are the averages during the maneuvers. Most of the maneuvers were performed with relatively little variation from these averages. In figure 7 the symbols correspond to initial thrust coefficients, which are approximately equal to the thrust coefficients during the time of the maneuvers, because the engine rpm was not varied and the airspeed was maintained approximately constant by the pilot. In figures 8 and 9, the symbols represent data from tests performed with different USB flap angles.
Reference 6 presents a summary of methods based on simplified aerodynamic theory for predicting lateral-directional stability derivatives. Results from this theory indicate that the contributions of the wing to the values of some of the derivatives are functions of the wing lift coefficient. Because the lift coefficient of the QSRA is closely related to C7-, (shown, for example, in ref. 1) the theory would indicate an effect on these derivatives of varying Cr, if the contribution of the wing is important. Most of the results shown in figure 7 are from tests at values of C:r from 0.8 to 1.1. With an increase in Cr to 1.74, (at o_ = 2.3 °) the data indicate a small increase in the yaw damping but little change in the other derivatives. A decrease in CT from 0.8 to 0.38 had a significant effect, decreasing the magnitude of the yaw damping derivative C_ by about half and C,,_ by about 30%. The magnitudes of C_,, and C_,p were also decreased by approximately 50% and 30%, respectively, with this decrease in C7-. An effect of varying the angle of attack is noticeable in the derivative C,_ where the increase in oL from 3 ° to 16 ° decreased this derivative by about 30%. A similar effect on Cr,_ of increasing ot is shown in the data from the tests reported in reference 4. The aircraft that was the subject of the study described in reference 4 had tail components and a fuselage that were essentially the same as those of the QSRA, but a different wing design and engine installation.
In figure 7, two maneuvers are identified with flagged symbols. These are tests B1 and B2 in the tables, maneuvers performed with the DLC spoilers deflected approximately 13 ° and with the USB flaps at 50 °. The graph showing Clp indicates that deflecting the spoilers increased the dihedral effect by at least 20%. The plots of C,,, indicate that the spoiler deflection increased the yaw damping at the smaller thrust coefficient (1.13) but caused little change at the larger CT (1.74). In general, deflecting the spoilers did not have significant effects on the values of the other stability derivatives.
Figures 8 and 9 present plots of four of the stability derivatives (Ctp, C,_, C_, and C,,, ), obtained from tests with USB flaps set at angles of 0 °, 31 °, and 660, compared with the values for the 50 ° deflection. For two of these flap settings, 0 ° and 31 °, data were available that allow a comparison with data for the 50 ° flap angle at approximately the same thrust coefficients. No test results were available for the 50 ° deflection at the high thrust coefficient (i.e., 2.6) represented by the conditions of the test with the USB flaps at 66 ° Results from the latter test are compared with data from test A5, for which the thrust coefficient is 1.74, the largest value of CT at which data were obtained for the 50 ° configuration. In figures 8 and 9, the data show little effect of changing the flap angle from 50 ° to 31 °, but a decrease from 50 ° to 0 ° decreased C o by about 30% and resulted in a small decrease in the magnitude of C,_. Figure 9 shows that the roll damping derivative C_, calculated from the test with the USB flaps at 66 ° was greater in magnitude than that with the 50 ° deflection, but as mentioned above there was a difference in thrust coeffients that may be the reason for some of this increase.
In figure 10 estimates given in table 2 for the derivatives Ct_ and C_ are plotted for the aircraft with the different USB flap deflection angles. They are shown as functions of the lift coefficient computed for conditions at the start of the maneuver. As in figures 8 and 9, values for the derivatives from data obtained with flap deflections of 0 °, 31 °, and 66 ° are compared with the values from tests with the flaps deflected 50 °. The figure indicates that the change in Ct, from its value for the 50 ° deflection to that for any of the other deflection angles was small when compared at similar values of Ct,. The magnitude of the estimate for the derivative C,_ at a lift coefficient of 5 for the configuration with the flaps at 31 ° was more than twice that for the 50 ° configuration. Results from tests at other conditions, however, indicate that estimates for this derivative are relatively independent of the flap deflection angles, if compared at the same lift coefficient.
Rudder and Lateral Control Effectiveness Estimates of the derivative 0_c_., the variation of yawing moment coefficient with rudder deflection, atn are listed in table 3 under the heading CNRUD. Most of the values estimated for this parameter are within the range from 0.35 to 0.41. The differing values do not show a correlation with variations in the test conditions or the airplane configuration. As indicated in reference 2, one of the design goals that had been specified for the aircraft was that the directional control could produce an initial acceleration in yaw of 0.23 radians per second squared under conditions for a normal STOL approach. If it is assumed that the rudder effectiveness is a linear function in the range of rudder deflection to its maximum of 25 o and is represented by the values for ac, listed in table 3, calculations indicate that this goal would be exceeded in STOL approaches and under the other conditions of the test maneuvers at airspeeds at least as low as 70 knots.
The effectiveness of the lateral control system of the QSRA in a configuration for STOL approach was investigated as part of the flight program reported in reference 7. Results presented in this reference indicate that the initial roll acceleration produced by full deflection of the control wheel (for the design airspeed and aircraft gross weight) met the design goal for this acceleration, 0.8 radians per second squared. Results of tests to determine effectiveness of this control for the aircraft with other USB flap deflections and at other test conditions are given in the present report. Deflection angles of the ailerons and the spoilers as functions of the control-wheel angle were measured with the airplane on the ground under conditions for which there would be no aerodynamic loads and no effect of a time lag in the system. This is the static calibration shown in figure 3. The relationship of the spoiler deflection to the aileron deflection shown in tiffs plot is representative of that existing during the test maneuvers for which the maximum angles of deflection of the control wheel were relatively limited, i. e., the maximum spoiler angles were less than about 35 °. Table 4, in which the maximum spoiler angles are listed, shows that tests A4, At, A7, B2, D1, and D2 were performed with these limited-angle inputs. For the other tests, the control-wheel excursions were large and, as shown in table 4, the spoilers deflected more than 55 °. Records of the surface deflection time histories from these tests show that the relationship of the spoiler and aileron deflections were significantly different from that illustrated in figure 3. The differences depended upon the rates at which the surfaces were moved and the length of time the control surface was held at the large angles.
Figure 11 illustrates examples of time histories of the aileron and spoiler deflections from two maneuvers, one (test A6) in which the maximum deflections were limited and one (test A1) that had large positive and negative deflections.
In the equations of motion presented earlier, the effects of the lateral control are expressed as forces and moments proportional to the aileron deflection plus those proportional to the spoiler deflection. Because the parameter estimation computations would not produce reliable values within a single solution for both the aileron and the spoiler derivatives, the calculations were executed with fixed values for one or the other of these derivatives. Values listed in the tables are taken from solutions in which the derivatives defined with respect to the spoiler deflection were fixed. The values that were chosen (shown in parentheses) undoubtedly are inaccurate by varying amounts, but their use allows the calculations to include some of the effects of the varying relationships of the aileron and spoiler deflections. When the lateral control inputs were represented in the equations of motion by the two separate terms, the computed acceleration time-histories consistently displayed better fits to the measurements than when represented by a single term (such as one based only on the control-wheel or aileron deflection). Table 3 lists the values extracted from the data for the aileron derivatives and the values set to represent the spoiler derivatives. One parameter that has been shown in wind tunnel tests to have an important influence on the performance of the lateral control is the strength of the blowing for aileron boundary-layer control. A measure of this parameter, the momentum coefficient C u for this blowing, is listed in table 3 as Cmu-AIL.
Any quantitative description of the effects of the variables on the lateral control effectiveness requires a means of combining the derivatives that apply to the two lateral control surfaces. Because of the varying relationship of the spoiler deflection to the aileron deflection, mentioned above, there is no unambiguous rule for combining them. However, for the purpose of discussing the effects of varying the test conditions, it is useful to choose simply the sum of the two derivatives (aileron and spoiler) as an effective lateral control derivative. The quantities Ct_r, C,_r, and C_'_r are defined in this way to represent approximately the rolling moment, yawing moment, and side force due to lateral control deflection. These quantities are plotted in figure 12 for the aircraft configuration with the USB flaps deflected 50 °. The yawing moment parameters based on this definition are listed (as CNLAT) in table 4.
For the configuration with the USB flaps at 50 °, figure 12 shows that there was a decrease by more than 15% in the rolling effectiveness parameter CLt_ when the thrust coefficient was decreased from 0.85 to 0.38 and C u decreased from 0.095 to 0.044. At thrust coefficients in the range from 0.8 to 0.9, data were obtained for this configuration that show some effect of angle of attack variation. An increase in o_ from 3 ° to 16 ° decreased this roll effectiveness by about 20%. Data from tests B1 and B2 indicate that setting the spoilers at an angle of deflection (of 13 °) increased the effectiveness by a small amount. The lateral control was slightly less effective with the USB flaps undeflected than with 50 ° deflection. Table 3 shows that a value for CL_ calculated for the test in which the USB flaps were deflected 66 o would be 0.55 (0.40 plus 0.15), which is significantly larger than the values from the other tests. This large value is partly attributable to the large value of the thrust coefficient (2.57). Estimated values for C,_r listed in table 4 (and plotted in figure 12 for the configuration with the USB flaps at 50 o) indicate that the yawing moment resultingfrom thelateralcontroldeflectionwasfavorablefor all of thetestmaneuvers. Thecontrol inputs that includedlargespoilerdeflectionsgenerallyresultedin the mostfavorable(positive)valuesfor C_.,z • The terms assumed to represent the input functions in the equations of motion, equations 1 through 6, include terms assumed to be proportional to the rate of deflection of the spoilers, in addition to those proportional to the deflections of the spoilers, ailerons, and rudder. They are included to account for any effect of a lag in the changes in flow direction in the region of the tail, changes induced by changes in the wing lift distribution, when the lateral control surfaces are deflected. The yawing- and rolling-moment derivatives associated with these terms, C,_ and Ct,, respectively, are listed in table 4 under the headings CNSD and CLSD. The values for the aircraft with the USB flaps at 50 ° are plotted in figure 13. This figure and table 4 show that for all of the tests in which the maximum spoiler angles were more than 10 °, the estimated values for C,_ are negative. This indicates that part of the favorable yawing moment due to the lateral control is a result of an induced sidewash. When this control is moved rapidly, the favorable yaw- ing moment response is preceded by a transient that for a brief interval reduces this moment. The rolling moment derivatives Cz_ are also all negative. This indicates that, because Ctt.,.r includes the induced flow effects, the immediate roll response to rapid movements of the control surfaces is slightly less than that indicated by the values of Ct_r in figure 12. These induced flow effects are qualitatively similar to those that were observed in the data from tests of the augmented jet-flap aircraft reported in reference 4.
CONCLUDING REMARKS Experiments have been conducted to determine lateral-directional stability characteristics of the QSRA, an experimental airplane designed to provide information on various flight characteristics of an aircraft that employs the upper surface blown (USB) flap powered-lift technology. Data records from maneuvers pro- duced by control-wheel and rudder inputs were analyzed with a parameter estimation procedure to extract stability and control derivatives for the airplane in several configurations and at various angles of attack and levels of engine thrust. The maneuvers were conducted with the normal stability augmentation sys- tem of the aircraft turned off. The USB flaps, which are mounted on the wing behind the engines and extend spanwise from the fuselage outward to the 47% semispan station, augment the wing lift by causing a deflection of the engine exhaust and increasing the circulation. Other features of the airplane's design in- clude trailing-edge slotted flaps extending out to the 70% semispan station and, outboard of these, ailerons with bounday-layer control. All of the tests described in this report were conducted with the slotted flaps deflected approximately 59 ° and with the ailerons drooped 23 °. Most of the test maneuvers were per- formed with the USB flaps set (nominally) at 50 °. In addition to these, a limited number of tests were also conducted with these flaps at 0 °, 31 °, and 66 °.
Results were obtained with the USB flaps at 50 ° that provided information on the effects of varying the thrust coefficient (CT) and angle of attack (oe), and of symmetrically deflecting upper-surface spoilers.
A decrease in C,r from 0.8 to 0.38 decreased the yaw damping by about 50% and decreased the derivative C,_ by about 30%. An increase in a from 3 ° to 16 ° caused a decrease of about 30% in the value of C,_. The data indicate that a 13 ° symmetrical deflection of the spoilers resulted in a small increase in the dihedral effect and slightly more yaw damping. The effects on most of the stability derivatives of setting the different USB flap angles were generally small, but the data indicate that when this flap angle was changed from 50 ° to zero, there was a decrease of about 30% in the value of C,_.
From earlier tests, it had been determined that the rudder and the lateral control were effective in providing yawing and rolling accelerations that met or exceeded the levels that had been specified as goals for the airplane's design conditions. The tests described in this report indicate that these controls were effective for the various configurations and throughout the ranges of angle of attack (up to 18 °) that were investigated. The effectiveness of the lateral control was somewhat reduced when the test was conducted at a reduced thrust level, corresponding to a value of Cr of 0.38, compared with other tests for which Ca- was 0.77 and larger. The variation of yawing moment coefficient with lateral control deflection was positive in sign for all of the test conditions. Results based on determination of the yawing moment associated with the rate of deflection of the lateral control surfaces indicate that there is an induced sidewash that provides some of the favorable variation of yawing moment with control deflection.
APPENDIX DATA REDUCTION FORMULAS Corrections to aerodynamic data that were applied as part of the data reduction are from tests con- ducted prior to those that are the subject of this report. The vane-indicated angle of attack, oti, was corrected by adding the increment A a, given by the following formula, in degrees.
As = -1.5[ 1. + 0.0182(6= - 55.)] - 0.12[ 1. + 1.5(6,,- 55.) + 0.0108(N- 60.)]c_ (7) - 0.0021 a 2 where iS,, is the USB flap deflection angle in degrees and N is the engine fan percent rpm, averaged among the engines. The sideslip angle/3 for all test conditions was computed as 93.5% of the angle indicated by the sideslip angle vane. This correction to the measurement was determined by the method described in reference 4. In this method the correction factor is determined by matching the rate of change of the side velocity computed from the vane measurement with this change computed from the side acceleration, roll and yaw rates, velocity, and attitude time histories.
Pitot static data corrections had been determined from low level flights in calm air under conditions where the true speed could be measured and the air density was known. The following formula was used to compute a correction which was added to the indicated airspeed (V_, knots).
AV = 0.3219 × 10-4Vi 3 - 0.01231V,. 2 + 1.4762 V_ - 53.405 The corrected dynamic pressure (_) in pounds per square foot was calculated from the equation (8) = 0.003385 V_2( 1. + AV(2. + AV/V_2)/V_) The corrected static pressure(P_) in pounds per square foot was computed from the indicated pressure (P_) with the relation P, = P_ - 0.003385A V(2. + A V/V,.) (9) The expression below was determined to be a suitable representation of the engine thrust, as a function of fan percent rpm, Mach number M, ambient pressure ratio, and temperature. Defining T_ as the ratio of absolute ambient to sea level standard temperature and For one engine the thrust 7", in pounds was computed as 7", = P_[(1.134+ 0.78M2)N_ - (53.3 + 27.M2)Nt + 6430.M 2 + 1420.]
1'161._./_, InrP_r_3NAttv Pa_A_t PRECEDING PAGE BLANK NOT FILMED ,,
The thrustcoefficientfor the four engines is calculatedas
c =E T" (lo)
,,=! q'g
The mass flow rate M of the air entering the engines was computed from the thrust and pressure ratio in slugs per second as follows: .Mr = P_ [0.4911 x lO-9(Tn/Pr) 2 + O.O0119(T./P_ + 2.5)] (11)
V%
The ram drag coefficient was calculated from the following relations, in which V_ is true airspeed in feet per second and the mass flow is summed for the four engines.
V_ = 29.03 _(T, (12) The side force and yawing moment data presented in this report am with the ram drag effect removed. The momentum coefficient C_, for aileron BLC blowing (Cmu AlL in table 3) is from the relation ( Vj - V) rh_ (13)
C. = 'gwA
where rh: is the mass flow rate from the BLC nozzles, V.r is the velocity of this flow, and SwA is the reference area defined as the area of the wing within the region spanned by the ailerons.
In equation (1), which is the side force expression, the side acceleration is given with reference to the aircraft c.g. The accelerometer package was located in the horizontal plane of the c.g. 1.45 feet behind the quarter-chord point of the mean aerodynamic chord and 0.71 feet to the left of the plane of symmetry. The quantities X_ and Y, in the equation below represent the distances of these instruments from the c.g. for the test conditons and are negative in sign. The acceleration was transferred to the c.g. with the equation (14) a7 = ay_ - (X.i" - II,(p2 + r 2 ) )/g where ay_ is the instrument measurement.
REFERENCES 1. Stephenson, J. D.; and Hardy, G. H.: Longitudinal Stability and Control Characteristics of the Quiet Short-Haul Research Aircraft (QSRA). NASA TP-2065, Nov. 1989.
2. Boeing Commercial Airplane Company Staff: Quiet Short-Haul Research Aircraft Predicted Flight Characteristics. NASA CR-152203, Oct. 1979 3. Eppel, Joseph C.: Quiet Short-Haul Research Aircraft Familiarization Document, Revision 1. NASA TM-81298, Sept. 1981.
4. Stephenson, J. D.: The Application of Parameter Estimation to Flight Measurements to Obtain Lateral- Directional Stability Derivatives of an Augmented Jet-Flap STOL Airplane. NASA TP-2033, Jan.
1983.
5. Bach, R. E., Jr.: A User's Manual for AMES (A Parameter Estimation Program). NASA CR-163118, 1974.
6. Campbell, J'. P.; and McKinney, M. O.: Summary of Methods for Calculating Dynamic Lateral Stability and Response and for Estimating Lateral Stability Derivatives. NASA TR-1098, 1952.
7. Cochrane, J. A.; Riddle, D. W.; Stevens, V. C.; and Shovlin, M. D.: Selected Results from the Quiet Short-Haul Research Aircraft Flight Research Program. AIAA J. Aircraft, vol. 19, no. 12, Dec.
1982.
Table1. QSRAlateral-directional tests---initialconditionsandaverage anglesof attack
Gross wt, Run Flt No./ USB DLC Init. Init. Av. Init. Init.
lb ID run code flaps, SPLRS, CL CT alpha, VE, altit., deg deg deg kt ft 55780 A1 361 A 48.7 0.0 5.61 0.86 15.6 70 3990 55570 361 B 48.7 0.0 5.67 0.87 18.0 69 4180 A2 56000 A3 361 C 48.7 0.0 3.04 0.38 1.1 95 7780 55880 361 D 48.7 0.0 5.45 0.77 16.0 71 5800 A4 51250 430 A 48.0 0.0 5.11 1.74 2.3 70 2825 A5 56050 439 A 49.2 0.0 4.20 0.85 3.1 81 6770 A6 55950 A7 439 B 49.2 0.0 4.30 0.88 3.1 80 5695 51000 430 B 48.0 12.1 5.05 1.74 5.2 70 2435 B1 56150 452 A 49.5 13.2 4.59 1.13 6.7 78 3220 B2 55770 C1 398 A 0.0 0.0 3.25 0.72 11.2 92 7370 50360 430 D 0.0 0.0 3.42 0.79 12.3 85 2555 C2 53940 D1 360 A 31.6 0.0 4.29 1.54 3.3 79 1750 53480 D2 360 B 31.6 0.0 5.02 1.80 9.8 72 2870 50730 430 C 65.9 0.0 6.24 2.57 0.3 63 1920 E1
....... o._._._._
.J 00_0000000000 >.
I_ _°_°_°__
° ° 0 ° ° • o ° o ° o o ° ° o • o ° ° o . ° 0 ° ° ° °
_TTTTT77_T
0__0___ dddddd_dodddd
i
,-, r_ e,.
i [- O' ra_ u 0 /
#
..Q Table 4. Lateral control rate derivatives CNLAT CNSD CLSD Run Max ID splr deft, deg A1 60.3 0.063 -0.008 -0.010 A2 60.1 0.080 -0.013 -0.010 A3 59.7 0.049 -0.007 -0.005 A4 9.6 0.042 -0.000 -0.026 A5 53.2 0.065 -0.015 -0.011 A6 20.1 0.027 -0.007 -0.016 A7 9.2 0.013 -0.005 -0.010 B 1 47.6" 0.096 -0.007 -0.009 B2 24.7 _ 0.067 -0.004 -0.015 C1 59.6 0.031 -0.005 -0.005 C2 60.1 0.033 -0.010 -0.005 D1 34.3 0.008 -0.006 -0.016 D2 19.0 0.023 -0.011 -0.008 E1 56.2 0.067 -0.012 -0.024 °Measured from initial position.
/!J\
A
_C
O
(
O o c: !
I-, _J C w I- u.i A (lc _1 L t,_ t'N v --m
g
0_,._ Lt.
• N c 0 o. ,-
¢
I I
T
¢
N u_ .(,_ I I I",,,, N :E N ,- u_ _v A 0 N I I
¢ v
E > c z c rr N I: Z _L,IJ .D_ ¸ _' "O 0 o9 w Z 1,1,1
<3
ORIGINAL PAGE BLACK _D. _HI[F., P_HOJ_OGRAP_ Figure 2. Photograph of the QSRA in a landing-approach configuration.
ORIGINAL PAGE rS OF POOR QUALITY SPOILERS. NEGATIVE SIGN: LEFT SPOILER UP LEFT AILERON T.E. DOWN, POSITIVE RIGHT AILERON T.E. UP, POSITIVE 20- O} -10
Jj
-20 -30 -40 ! | J I ! I I I -50 -60 -40 -20 0 20 -80 40 60 80 CONTROL WHEEL DEFLECTION, 5w, deg Figure 3. Static calibration of the aileron deflection and the spoiler deflection as functions of the control- wheel angle.
I .3 5- -.3 -16
_11
9O | I I I I I I I I I I I I I I I -90 0 5 10 15 20 25 30 35 40 TIME, sec (a) Figure 4. Time-history record of a typical maneuver resulting from a rudder input followed by a control- wheel input. Test A5. (a) at-, t3, 6R, and 6w.
"0 -15 rn /
i
-3 r\ ¢_ "\\ "0 -10 U
\
! I I ! | I 1 [ I I I I -30 , i , , 0 5 10 15 20 25 30 35 40 TIME, sec (b) Figure 4. Concluded. (b) o_, qS, r, and p.
240,000 CN t (3 200,000 / v )< i I I I I I 160,000 440,000 420,000
%
I (3 400,000 .J N I I I l ,I I 380,000 (3 22,000 J 26,000 f N X I I I I I -- 18,000 i 4O 44 48 52 66 60 x 1000 GROSS WEIGHT, Ib Figure 5. QSRA moments of inertia, I= and Iz, and product of inertia, I_,, as functions of gross weight.
--FROM MEASURED DATA ...... FROM ESTIMATED PARAMETERS 6 W (g c_ [D _. 20 ¢,O J 6 R -80 .3 V t i -.3 .2 C -.2 .8 , I ,,, I I I I I I I -.8 0 5 10 15 20 25 30 35 40 TIME, sec Figure 6. Comparison of the time histories of Cl, C,_, and Cy computed with measured and with estimated parameters. USB flaps, 50 °, Test A3.
C T [] .38 O .8- 1.1 O 1.74 FLAG - DLC SPOILERS AT 13 °
0 I
E] @ GE) O b
I
I i I I I -.8 1 1.2 0 0 "o .8 [] .4 I I I I I I= @ _. -.2 o _ o ko_
oo
_o -.4 i i i i 0 4 8 12 16 20 _, deg Figure 7. Lateral-directional stability derivatives for the QSRA with the USB flaps deflected 50 °. (a) Rolling- moment derivatives.
O, _> OQ 'o Q -.4 re, , Q e" I _ I i J -.8 B --,4 Q ¢J --.8 I | I I I -1.2 1.2 08 _ .8 .4 (b) | I I I J 4 8 12 16 20 _, deg Figure 7. Continued. (b) Yawing-moment derivatives.
"o 0.
>- l I I 1 -2
o8
_ o°
I I I I GD O o0 _,'o -4 >- o -8 _,c) I i I I !
0 4 8 12 16 20 (_, deg Figure 7. Concluded. (c) Side-force derivatives.
USB FLAPS C T r'] 66 deg 26 O 50 1.7 '1o 1 1 E)
° I
i i I I -.4 , . i i i i _ 0 i USB F LAPS O 31 deg O 50 "o 0<> 0 I |, i i I _ -.4 i i i i I _c 0 USB FLAPS L_ 0 deg O 50 "o "1o O[ _ 1 1 Q i _-0 _ .. L A | I -.4 i i i = ¢j ¢J 0 4 8 12 16 20 0 4 8 12 16 20 _, deg o_, deg Figure 8. Sideslip derivatives, Ct_ and C,_, vs o_, for the QSRA with the USB flaps deflected 0 °, 31 °, and 66 ° , compared with the derivatives for 50 ° flap deflection.
USB FLAPS I"1 66 deg O 50 "lO -.4 ® .'1 E) Q.
==-.8 _°8 _3 I I I I I , l = J I -1.2 -1.2 USB FLAPS O 31 deg O 50 O I "ID -.4 Q ¢ E)¢ GI.
_-.8 _°8 ¢ I I I I I I I I I i -1.2 -1.2 USB FLAPS Z_ 0 deg O 50 AZ_
o o i
(3 i I (_ (3 a -.8 i l = a i -.8 I 8 12 16 20 0 4 8 12 16 20 0 4 o_, deg _, deg Figure 9. Roll- and yaw-damping derivatives vs _ for the QSRA with the USB flaps deflected 0 °, 31 °, and 66 ° , compared with damping estimates for the aircraft with the flaps at 50 ° .
USB FLAPS CT 2.6 [] 66 deg O 50 1.7 1.2 - 1:1 "10 Q .8 E "0 _.4 .4 "0.
O[
p.
(.I I --.8 I I I i USB FLAPS O 31 deg 1.2 O 50 .8 "10 O O O.
_. -.4 .4 @ "(3.
,r = @ i i i I I I l --.8 USB FLAPS L_ 0 deg 1.2 - O 50
%
"O cP
O I_ .8 Z_ "O O ¢, O.
O _o4 i .4 O O t- O I I I l --.8 I i 0 I i I I 4 5 6 7 6 7 2 3 4 5 3 CL C L USB flaps, 0 °, 31 °, and 66 °, Figure 10. Cross derivatives, Ct, and C,_, as functions of lift coefficient.
compared with the derivatives for 50 ° flap deflection.
6A .... 6 S 2O 6 A 6S, deg -20 -40 20- 6 W, deg 0 -'-_---_- -20 - -40 - (a) I _ , i I l , I -60 ' ' 26 28 30 20 22 24 TIME, sec " " AILERONS ...... SPOILERS i I _, 6 A 6 S, deg
-
-20 _t -40 El- 6 w, deg -50 - (b) i I i L _ I - 1O0 , I , i , .J , i , i , i 1 2 3 0 4 5 6 7 8 9 TIME, sec Figure 11. Time-history records of the aileron and spoiler deflections from two maneuvers having different control-wheel input variations. (a) Input with small maximum wheel angle. Test A6. (b) Input with large maximum wheel angle. Test A1.
CT C DLC P SPOILERS, deg [3 0.38 0.04 0 0.8 - 0.9 0.10 - .13 0 O h 1.1 0.10 13 O 1.74 0.13 0 1.74 0.13 12 .6 E) .4 _ E) (3 ,.J .2 I I I I | Q z_ Q 0 @ O ...I | i I I i .2 0 Q_ .-I >- -.2 ¢ A A i i 0 4 8 12 16 20 o_, deg Figure 12. Variation of the rolling-moment, yawing-moment, and side-force coefficients with lateral con- trol deflection vs a; USB flaps at 50 °.
C T [] 0.38 O 0.6 - 1.0 Z_ 1.0 - 1.4 O 1.4- 1.8 FLAG - DLC SPOILERS AT 13 ° 0 0
e
_. -.02 t,- r.j I I A I -.04 i e S. o e !
• '<, -.02 I I I I 0 4 8 12 16 2O o_, deg Figure 13. Variation of the rolling- and yawing-moment coefficients with rate of deflection of the spoilers.
USB flaps, 50 °.
Report Documentation Page
Naiona_ A_on_bcl and Spaoe Admini_r slion 2. Government Accession No.
3. Recipient's Catalog No.
1. Report No.
NASA TM- 102250 5. Report Date 4. Title and Subtitle May 1990 Lateral-Directional Stability and Control Characteristics of the Quiet Short-Haul Research Aircraft (QSRA) 6. Performing Organization Code 8. Performing Organization Report No.
7. Author(s) A-90007 Jack D. Stephenson, James A. Jeske, and Gordon H. Hardy 10. Work Unit No.
505-61-71 9. Performing Organization Name and Address 11. Contract or Grant No.
Ames Research Center Moffett Field, CA 94035-1000 13. Type of Report and Period Covered Technical Memorandum 12. Sponsoring Agency Name and Address National Aeronautics and Space Administration 14. Sponsoring Agency Code Washington, DC 20546-0001 15. Supplementary Notes Point of Contact: Jack D. Stephenson, Ames Research Center, MS 211-2 Moffett Field, CA 94035-1000 (415) 604-6004 or FTS 464-6004 16. Abstract Tl_t_rt _nts the results of flight experiments to determine the lateral-directional stability and control characteris- tics of the Quiet Short-Haul Research Aircraft (QSRA), an experimental aircraft designed to furnish information on various aerodynamic characteristics of a transport type of airplane that makes use of the upper-surface blown (USB) flap technology to achieve short takeoff and landing (STOL) performance. The flight program designed to acquire the data consisted of maneuvers produced by rudder and control-wheel inputs with the airplane in several configurations that had been proposed for landing approach and takeoffoperation. The normal stability augmentation system was not engaged during these maneuvers.Time- history records from the maneuvers were analyzed with a parameter estimation procedure to extract lateral-directional stability and control derivatives. For one aircraft configuration in which the USB flaps were deflected 50 °, several maneuvers were performed to determine the effects of varying the average angle of attack, varying the thrust coefficient, and setting the airplane's upper surface spoilers at a ] 3 ° symmetrical bias angle. The effects on the lateral characteristics of deflecting the spoilers were rather small and generally favorable. The data indicate that for one test, conducted at low thrust (a thrust coefficient of 0.38), compared with results from tests at thrust coefficients of 0.77 and larger, there was a significant decrease in the lateral control effectiveness, in the yaw damping and in the directional derivative (_. The directional derivative was also decreased (by about 30%) when the average angle of attack of the test was increased from 3 ° to 16 ° .
18. Distribution Statement 17. Key Words (Suggested by Author(s)) Unclassified-Unlimited STOL aircraft, Lateral-directional stability, Powered li t aircraft, QSRA flight research Subject Category - 08 22. Pdce 20. Security Classif. (of this page) 21. No. of Pages 19. Security Classif. (of this report) A03 Unclassified T_,_-_ assified NASA FORM 1626 OCTSS For sale by the National Technical Information Service, Springfield, Virginia 22161