NASA Technical Memorandum 102250

Lateral-DirectionalStability and

Chort ontrolHaul Characteristics.of ResearchA_rcraft the Quiet (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

b

Cms

cL

c.

cr

cy

g

Ix, Ir, Iz

Ixz

mj

p, q,r

S

T

V

Vj

W

SWA

X_, Z1

6R

_s

Sw

¢

(')

lateral acceleration, g

wing span, ft

ram drag coefficient

rolling moment coefficient

lift coefficient

yawing moment coefficient

thrust coefficient

side force coefficient

aileron BLC momentum coefficient (written as Cmu_AIL in table 3)

acceleration of gravity

moment of inertia about the X-, Y-, and Z-axis, slug-ft 2

product of inertia, slug-ft 2

aircraft mass, slugs

aileron BLC nozzle mass flow rate, slugs/sec

engine air mass flow rate, slugs/sec

roll, pitch and yaw rates, deg/sec or rad/sec

dynamic pressure, lb/sq ft

wing area

engine thrust, lb

true airspeed, ft/sec

aileron BLC nozzle flow velocity, ft/sec

gross weight, lb

reference area for defining Cu, sq ft

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

rudder deflection, deg or rad

spoiler deflection, deg or rad

wheel deflection, deg

roll angle, deg

derivative with respect to time

O

e

initial condition

based on estimates

Subscripts

BLC

DLC

USB

boundary layer control

direct lift control

upper surface blown (flaps)

Abbreviations

PRECEDING PAGE BLANK NOT FILMED

III
Symbols identifying the stability and control derivatives in the figures are defined as follows:

act c,,,=

_,, c,,,--9 c,,,=

c,,,,=_ c,,,,=_, c,,,,,=_

Ct_s =..___t 06s Cn6s =ac.#6s Cv_s =a_.__ 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

CLV=c,,

CLR = C_

CLRUD = Cz._

CLAIL = CIsA

CLSP = Otss

CLLAT = CtLAT

CLSD = Ct_

CNB = C,_

CNP = C,_

CNR = C,_

CNRUD = C..t_

CNAIL = C.,A

CNSP = C,_s

CNLAT = C_T

CNSD = C.6

CYB = Cvp

CYP = OF,

CYR = OF,

CYRUD = Cr.t_

CYAIL = Or6A

CYSP = Oy6s

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 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 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 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 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 experience 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 stability 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 surfaces 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 spanwise station at 70% semispan outward to the wing tip. The pilot's control wheel drives a dual hydraulic
tandemactuatorto operatethe ailerons.Betweenthe aileronsandthe USBflaps,thewing is fitted with

conventionaldouble-slottedtrailing-edgeflaps.

Uppersurfacespoilersconsistingof twosurfaces,anoutboardandaninboardsection,oneachwing

panelarelocatedaheadof the slottedflaps. Theyareoperateddifferentially by control-wheeldeflection

throughhydraulicactuatorsto provideroll control,augmentingthatof theailerons.Figure3showsastatic

calibrationof thedeflectionanglesof theaileronsandthespoilersasfunctionsof thecontrol wheelangle.

Also, all of thespoilerscanbedeflectedtogether(symmetrically)to providedirectlift control (DLC) in

additionto their functionasa lateralcontrol. Therudderon theairplaneis double-hinged,with therear

portiondeflectingupto 50° (measuredfrom theaircraftcenterline),twicethatof theforwardsection.The

airplanewasfittedwith anoseboomonwhichweremountedanangle-of-attackvane,asideslipvane,and

pitot-staticinstrumentation.Instrumentationfor acquisitionof testdataprovidedfor onboardrecordingand

telemetrywith ground-basedrecordingof morethan100variablesatratesof 100Hz. Beforeprocessing

thedata,however,theframeratewasreducedbydecimationto 20Hz, andtheanalysisof thedatais based

onthisrate.

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.

2
Otherquantitiespertinentto theprocessingof 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 preprocessing 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

[÷_ Ixz_]

XI

-_ --_-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

i:1 j=l

40C. 40C.

c.:c. + +E -ff ;e,

i= 1 ]= 1

The state and input variables, (i and dij, are defined as follows.

(5)

(6)

2V

2V

61 = 6s - 6e_ 62 = 6A -- 6Ao

63 "- 6S -- 6S0 64 = _S

3
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 timehistory 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 associated 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 deflection. 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 variationwith time of the rolling-momentcoefficient,theyawing-momentcoefficient,andthe

side-forcecoefficientwerecalculatedfrom thedatameasurementsfor eachmaneuver.Plotsof thesevariationswerecomparedwith plotsof thevariationsof thesecoefficientscalculatedusingthe valuesof the

derivativesfrom theparameterestimationsolutions.An exampleof thiscomparisonis presentedin figure6. For all of themaneuverslistedin thetables,thetimehistoriesbasedonthe measurementsandon

theestimateswerein 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 oLfrom 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

5
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,

6
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 themostfavorable(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 yawing 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 produced 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 system 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 include 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 performed 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 conducted 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_

- 0.0021 a 2 (7)

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

= 0.003385 V_2( 1. + AV(2. + AV/V_2)/V_) (8)

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.]

11

1'161._./_, InrP_r_3NAttv Pa_A_t PRECEDING PAGE BLANK NOT FILMED ,,
Thethrustcoefficientfor thefour enginesis calculatedas

4

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

a7 = ay_ - (X.i" - II,(p2 + r 2 ) )/g (14)

where ay_ is the instrument measurement.

12
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 LateralDirectional 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.

13
Table1. QSRAlateral-directionaltests---initialconditionsandaverageanglesof attack

Run

ID

Flt No./ USB DLC Init. Init. Av. Init. Init.

run code flaps, SPLRS, CL CT alpha, VE, altit.,

deg deg deg kt ft

Gross wt,

lb

A1

A2

A3

A4

A5

A6

A7

B1

B2

C1

C2

D1

D2

E1

361 A 48.7 0.0 5.61 0.86 15.6 70 3990

361 B 48.7 0.0 5.67 0.87 18.0 69 4180

361 C 48.7 0.0 3.04 0.38 1.1 95 7780

361 D 48.7 0.0 5.45 0.77 16.0 71 5800

430 A 48.0 0.0 5.11 1.74 2.3 70 2825

439 A 49.2 0.0 4.20 0.85 3.1 81 6770

439 B 49.2 0.0 4.30 0.88 3.1 80 5695

430 B 48.0 12.1 5.05 1.74 5.2 70 2435

452 A 49.5 13.2 4.59 1.13 6.7 78 3220

398 A 0.0 0.0 3.25 0.72 11.2 92 7370

430 D 0.0 0.0 3.42 0.79 12.3 85 2555

360 A 31.6 0.0 4.29 1.54 3.3 79 1750

360 B 31.6 0.0 5.02 1.80 9.8 72 2870

430 C 65.9 0.0 6.24 2.57 0.3 63 1920

55780

55570

56000

55880

51250

56050

55950

51000

56150

55770

50360

53940

53480

50730

14
i

0

i

ra_

0 /

..Q

.J

00_0000000000

I_ _°_°_°__

° ° 0 ° ° • o ° o ° o o ° °

o • o ° ° o . ° 0 ° ° ° °

_TTTTT77_T

0__0___

dddddd_dodddd

[-

>.

0

0

,-, r_

0

O'

u

#

....... o._._._._

e,.

15
Table 4. Lateral control rate derivatives

Run Max

ID splr

deft,

deg

CNLAT CNSD CLSD

A1 60.3 0.063 -0.008

A2 60.1 0.080 -0.013

A3 59.7 0.049 -0.007

A4 9.6 0.042 -0.000

A5 53.2 0.065 -0.015

A6 20.1 0.027 -0.007

A7 9.2 0.013 -0.005

B 1 47.6" 0.096 -0.007

B2 24.7 _ 0.067 -0.004

C1 59.6 0.031 -0.005

C2 60.1 0.033 -0.010

D1 34.3 0.008 -0.006

D2 19.0 0.023 -0.011

E1 56.2 0.067 -0.012

-0.010

-0.010

-0.005

-0.026

-0.011

-0.016

-0.010

-0.009

-0.015

-0.005

-0.005

-0.016

-0.008

-0.024

°Measured from initial position.

16
>

c

c

rr

/!J\

!

w

Iu.i

(lc

_1

N u_

:E N ,-

0

N I:

_L,IJ

N

I I

I I

.D_  ̧ _'

"O

• N

c 0

o. ,-

u_

I I

w

<3

T

_v

(

A

t,_ t'Nv

¢

¢

¢

_C

O

O

o

L

A

--m

1

.(,_

I",,,, N

A

v

E

z

Z

0

o9

Z

1,1,1

c:

I-,

_J

C

g

0_,._

Lt.

17
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

18
50

40

30

20-

10

O}

0

-10

-20

-30

-40

-50

SPOILERS. NEGATIVE SIGN:

LEFT SPOILER UP

LEFT AILERON T.E. DOWN, POSITIVE

RIGHT AILERON T.E. UP, POSITIVE

Jj

I ! I I I

-60 -40 -20 0 20

CONTROL WHEEL DEFLECTION,

! | J

-80 40 60 80

5w, deg

Figure 3. Static calibration of the aileron deflection and the spoiler deflection as functions of the controlwheel angle.

19
5-

.3

0

-.3

I

16

0

-16

50

_11

0

9O

-90

0

(a)

| I I I I I I I I I I I I I I I

5 10 15 20 25 30 35 40

TIME, sec

Figure 4. Time-history record of a typical maneuver resulting from a rudder input followed by a controlwheel input. Test A5. (a) at-, t3, 6R, and 6w.

20
15

"0

-15

30

i

-3

rn

/

"0

10

-10

r\

¢_ "\\

30

U

-30 , i , ,

0 5 10

(b)

\

! I I ! | I

15 20 25

TIME, sec

Figure 4. Concluded. (b) o_, qS,r, and p.

1 [ I I I I

30 35 40

21
CN

t

(3

/

03

)<

%I

(3

.J

03

N

240,000

200,000

160,000

440,000

420,000

400,000

380,000

v

i I I I I I

I I I l ,I I

26,000 f

(3

22,000

J

03

N

X

-- 18,000 i

4O

I I I I I

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.

22
(g

_. 20

¢,O

-80

.3

0

-.3

--FROM MEASURED DATA

...... FROM ESTIMATED PARAMETERS

c_ [D

J

6R

6W

V t i

C

.2

-.2

.8

0

-.8

0

, I ,,, I I I I I I I

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.

23
0I

I

-.8 1

1.2

.8

.4

CT

[] .38

O .8- 1.1

O 1.74

FLAG - DLC SPOILERS AT 13 °

E] @ GE) O

b

I i I I I

[]

"o

0

0 0

I I I I I

I=

_. -.2

ko_

@

o _ o

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) Rollingmoment derivatives.

24
O,

-.4

re, ,

e"

-.8

OQ

0

_>

'o

Q

0

Q

I _ I i J

¢J

B

--,4

--.8

-1.2

1.2

.8

.4

(b)

0

0

Q

I | I I I

08 _

| I I I J

4 8 12 16 20

_, deg

Figure 7. Continued. (b) Yawing-moment derivatives.

25
0.

>-

>-

o

0

-2

4

13

0

0

13

-4

-8 _,c)

0

o8

o0

"o

l I I 1

_ o°

0

I I I I

_,'o

I i I

4 8 12

(_, deg

GD O

I

16

!

20

Figure 7. Concluded. (c) Side-force derivatives.

26
USB FLAPS C T

r'] 66 deg 26

O 50 1.7

'1o

° I 1 1 E)

-.4 , . i i i i _ 0 i

USB F LAPS

O 31 deg

O 50

"o

_ -.4 i i i i I _c 0

0<> 0 0

i i I I

I |, i i I

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.

27
0

USB FLAPS

I"1 66 deg

O 50

0

Q.

_°8

_3

-1.2

®

.'1

"lO

-.4

==-.8

, l = J I -1.2

E)

I I I I I

O I

GI.

_°8

-1.2

Q

¢

0

I I I I

USB FLAPS

O 31 deg

O 50

0

"ID

-.4

_-.8

i -1.2

E)¢

¢

I I I I I

USB FLAPS

Z_ 0 deg

O 50

o oi

-.8 i l = a i -.8 I

0 4 8 12 16 20 0 4

_, deg

AZ_

(3

i I (_ (3 a

8 12 16 20

o_,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 ° .

28
1.2 -

USB FLAPS

[] 66 deg

O 50

CT

2.6

1.7

"10

E

.8

.4

0

Q

I I I i

1:1

"0

"0.

p.

(.I

I O[ _.4

--.8

1.2

.8

O.

.4

i I I I l

USB FLAPS

O 31 deg

O 50

0

"10

_. -.4

"(3.

,r=

--.8

"O

¢,

O.

O

1.2 -

.8

.4

Z_

cP

%

USB FLAPS

L_ 0 deg

O 50

O I_

_o4 i

--.8

2

"O

tO

I i

6 7

0 I i I I

2 3 4 5 3

C L

Figure 10. Cross derivatives, Ct, and C,_, as functions of lift coefficient.

compared with the derivatives for 50 ° flap deflection.

O O

@

i

@ i

O

O

O

I I I l

4 5 6 7

CL

USB flaps, 0 °, 31 °, and 66 °,

29
6A

6S, deg

60

40

2O

0

-20

-40

6A

.... 6S

6 W, deg

6 A

6 S, deg

80

60

40

20-

0 -'-_---_-

-20 -

-40 - (a)

-60 ' '

18

60

40

20

0

-20

-40

20 22 24

TIME, sec

I _ , i I l , I

26 28 30

" " AILERONS

...... SPOILERS

i I _,

-

_t

6 w, deg

50

0

-50 -

(b)

i

ElI i L _ I

1 2 3

- 1O0 , I , i , .J , i , i , i

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.

30
[3

O

h

O

CT C DLC

P SPOILERS,

deg

0.38 0.04 0

0.8 - 0.9 0.10 - .13 0

1.1 0.10 13

1.74 0.13 0

1.74 0.13 12

.6

,.J

E)

.4 _ E)

13

.2

0

(3

I I I I |

...I

z_ Q

0 @ O

.2 0

0

.-I

>-

Q

| i I I i

0

Q_

-.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 control deflection vs a; USB flaps at 50 °.

31
CT

[] 0.38

O 0.6 - 1.0

Z_ 1.0 - 1.4

O 1.4- 1.8

FLAG - DLC SPOILERS AT 13 °

0

13

e

_. -.02

t,-

r.j

-.04 i

0 0

0

I I A I

e

S. o e

• '<, -.02 I I I I

0 4 8 12 16

o_, deg

!

2O

Figure 13. Variation of the rolling- and yawing-moment coefficients with rate of deflection of the spoilers.

USB flaps, 50 °.

32
Naiona_ A_on_bcl and Report Documentation Page

Spaoe Admini_r slion

1. Report No.

NASA TM- 102250

2. Government Accession No.

4. Title and Subtitle

Lateral-Directional Stability and Control Characteristics of the

Quiet Short-Haul Research Aircraft (QSRA)

7. Author(s)

Jack D. Stephenson, James A. Jeske, and Gordon H. Hardy

9. Performing Organization Name and Address

Ames Research Center

Moffett Field, CA 94035-1000

12. Sponsoring Agency Name and Address

National Aeronautics and Space Administration

Washington, DC 20546-0001

3. Recipient's Catalog No.

5. Report Date

May 1990

6. Performing Organization Code

8. Performing Organization Report No.

A-90007

10. Work Unit No.

505-61-71

11. Contract or Grant No.

13. Type of Report and Period Covered

Technical Memorandum

14. Sponsoring Agency Code

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 characteristics 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.Timehistory 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° .

17. Key Words (Suggested by Author(s))

STOL aircraft, Lateral-directional stability,

Powered li t aircraft, QSRA flight research

18. Distribution Statement

Unclassified-Unlimited

Subject Category - 08

19. Security Classif. (of this report)

T_,_-_assified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

33

22. Pdce

A03

NASA FORM 1626 OCTSS

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