NASA/CR-1999-209527 Cg/Stability Map for the Reference H Cycle 3 Supersonic Transport Concept Along the High Speed Research Baseline Mission Profile Daniel P. Giesy and David M. Christhilf Lockheed Martin Engineering & Sciences Company, Hampton, Virginia December 1999
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NASA/CR-1999-209527
Cg/Stability Map for the Reference H Cycle 3Supersonic Transport Concept Along theHigh Speed Research Baseline Mission Profile
Daniel P. Giesy and David M. ChristhilfLockheed Martin Engineering & Sciences Company, Hampton, Virginia
Cg/Stability Map for the Reference H Cycle 3Supersonic Transport Concept Along the HighSpeed Research Baseline Mission Profile
Daniel P. Giesy and David M. ChristhilfLockheed Martin Engineering & Sciences Company, Hampton, Virginia
National Aeronautics and
Space Administration
Langley Research Center
Hampton, Virginia 23681-2199
Prepared for Langley Research Center
under Contract NAS1-96014
December 1999
Available from:
NASA Center for AeroSpace Information (CASI) National Technical Information Service (NTIS)
7121 Standard Drive 5285 Port Royal Road
Hanover, MD 21076-1320 Springfield, VA 22161-2171
(301) 621-0390 (703) 605-6000
Abstract
A comparison is made between the results of trimming a High Speed Civil Transport (H-SCT) concept along a reference mission profile using two trim modes. One mode uses thestabilator. The other mode uses fore and aft placement of the center of gravity. A comparisonis made of the throttle settings (cruise segments) or the total acceleration (ascent and descentsegments) and of the drag coefficient. The comparative stability of trimming using the twomodes is also assessed by comparing the stability margins and the placement of the lateral andlongitudinal eigenvalues.
IntroductionThe study reported in this document is a follow on study to the work reported by Chowdhry
and Buttrill in their memorandum [1]. In that report, they documented “a study performed toassess the bare airframe stability characteristics of a HSCT configuration and to investigate thebenefits, if any, of using an active fuel management system to reduce trim drag.” The study consistsof trimming the aircraft at each point along a reference mission profile (1) holding the x-cg atits nominal position and using the stabilator and (2) holding the stabilator at zero deflection andmoving the x-cg to trim. Stability and performance measures of the aircraft are compared at thetwo trim conditions at each point of the reference mission profile.
Ref. [1] studied the Reference H, cycle 1 HSCT concept. The present study uses theReference H Cycle 3 airplane (Ref. H-3) [2].
Reference Mission ProfileThe reference mission profile was taken from a TCA Configuration Description Document
[3, pp. A32 – A43]. It is described by a sample of 79 flight conditions divided into five segments:
This mission profile was designed for the Technology Concept Airplane (TCA) which isheavier than Ref. H-3. To correct for this weight differential, the aircraft weights from the TCAmission profile have been multiplied by the factor 649914/740600 which is the ratio of the maxi-mum taxi weight of Ref. H-3 to that of TCA. Each flight condition of the reference mission profileis then defined by its Mach number, its altitude, its (scaled) weight, and its rate of climb. These areshown in Figs. 1 – 4.
Modeling and Analysis SoftwareThe model of Ref. H-3 and much of the analysis software was contained in an integrated
MATLAB/SIMULINK HSCT simulation [4]. The software modulerefhsim3 trim.m in [4]performed an analysis of the Ref. H-3 aircraft at each flight condition using specific values ofthe trim variables. For this analysis, the AUTOCGFLAG and the AUTOWTFLAG were turnedoff; weight was scheduled by the reference mission profile as already explained and the center
2
of gravity was determined by interpolation using the five standard mass sets as explained in thenext section. The AUTOFLAPFLAG was on, so that flaps followed their automatic schedule, andRIGID FLAG was off, so Quasi-Steady AeroElastic (QSAE) increments were incorporated. TheMATLAB Optimization Toolbox constrained optimization routineconstr.m was used to varythe trim variables to achieve the trim conditions. Once trim was achieved, the derivatives@CM=@�and@CL=@� were estimated using a central difference derivative approximation with�� = :1deg., further utilizingrefhsim3 trim.m . Stability margin (as a per cent of mean aerodynamicchord) was then calculated to be�100(@CM=@�)=(@CL=@�).
The trimmed aircraft was then linearized usinglinearmodel.m and refh-sim3 lin.m from [4]. Lateral and longitudinal eigenvalues were calculated by applying MAT-LAB built-in function eig to subblocks of the linear system matrix.
Trim DetailsIn all trim runs, the thrust multiplier was set to 1.09, so that maximum power available
was 109% of nominal maximum. This was suggested by Dr. Chris Gracey of LaRC based on hisexperience with calculating fuel optimal trajectories.
At all flight conditions, nominal X and Z positions of the center of gravity were determinedby linear interpolation using gross weight as the independent variable and using the simulationmass sets from [2, Table 3.1-1, Page 3-2]. The relevant data are (Z-CG data come from a Boeing-supplied FORTRAN subroutineDATAstatement):
At each flight condition, the aircraft was trimmed in two different ways. In theStabilatortrimmedcase, the X-CG was held at its nominal value, and trim was achieved using the coupledstabilizer and elevator (withDELEV1 = DELEV2 = 2*DSTAB). In theCG trimmedcase, thestabilator was held at 0 degrees deflection, and the X-CG was moved to achieve trim.
In all trim cases the body axis X-velocity,u, the body axis Z-velocity,w, and the Euler pitchangle,�, were used as trim variables. The parameters gross weight and altitude were scheduled bythe flight condition.
In all trim cases, the trim constraints included constant angle of attack (_� = 0) and constantpitch rate (_q = 0). Mach and rate of climb were constrained to values scheduled by flight condition.
During climb (Seg. 1), throttle was set to max (100%) and during descent (Segs. 3 and 5),throttle was set to idle (3%). During the cruise segments (Segs. 2 and 4), an additional constraintwas imposed; total velocity was to be constant (_VT = 0). The throttle setting then became anadditional trim variable.
After trim was calculated, the stability margin was determined as previously noted. Thetrimmed aircraft was then linearized. The linearized states are:
1. Total Velocity,VT ,
3
2. Angle-of-attack,�,
3. Pitch rate,q,
4. Euler angle�,
5. Altitude,h,
6. Roll rate,p,
7. Yaw rate,r,
8. Bank angle�,
9. Sidslip angle�,
10. Euler angle ,
11. Latitude, and
12. Longitude.
Linearization of the trimmed aircraft produces a 12 by 12 state matrix,A. The longitudinaleigenvalues are found by taking the eigenvalues of the sub-matrix ofA consisting of the first 5 rowsand columns ofA. The lateral eigenvalues are found by taking the eigenvalues of the sub-matrixof A consisting of rows and columns 6 – 9 ofA.
Trim ResultsTrim values of trim variables are shown in Figs. 5 – 10. Fig. 5 shows that, with the X-CG
held to its nominal position, trim can be established throughout the reference mission profile withstabilizer deflections of no more than about�1:5Æ (with coupled elevator deflections of up to about�3Æ). Fig. 6 shows the nominal X-CG schedule (circles) and the X-CG position needed to trim inthe absence of stabilator deflection (x’s). The horizontal dash-dot lines show the forward (48%)and aft (54%) X-CG limits as given in [2, Page B-8]. The nominal X-CG schedule takes it outsidethese limits during part of the supersonic cruise segment (Seg. 2). The trim position of the X-CG,however, exceeds the aft X-CG limit both more often and by a greater amount than the nominal.The elapsed time to fly from flight condition 8 to 15 (the last condition before the X-CG exceedsits aft limit until the first condition where the X-CG has returned to its limit) is 10 minutes 22seconds. Besides the question of whether one would want to exceed the limit by so much, there isthe question of whether one would want to include high enough capacity fuel pumping systems tomove the X-CG that rapidly. The X-CG trim position throughout the entire descent and subsoniccruise phase (Segs. 3 – 5) falls outside the aft limit, the excess becoming as much as 6% of meanaerodynamic chord.
The value of trim variableu to trim the aircraft is shown in Fig. 7. It seems to be quiteinsensitive to whether the aircraft is trimmed by stabilator deflection or X-CG positioning. Thevalues of trim variablesw and�, shown in Figs. 8 and 9, show only slightly more sensitivity to thetrim mode.
In the cruise segments, the power lever setting is used as an additional trim variable, sup-plemented by adding the constraint that the total acceleration should be zero (_VT = 0). Fig. 10
4
shows that the X-CG trimmed aircraft uses slightly less power in these segments. In the climb anddescent segments, Segs 1, 3, and 5, where the power setting is programmed to a fixed setting, theX-CG trimmed aircraft experiences slightly more acceleration (Fig. 11). Both of these phenomenaare attributable to the reduction in drag coefficient,CD, which is the result of trimming by varyingthe X-CG position as opposed to using the stabilator. This is shown in Fig. 12.
Stability ResultsStability margins for each trimmed condition are shown in Fig. 13. Although the results
between the two trim paradigms are mixed over the reference mission profile, the X-CG trimmedcase seems to have more tendency to go to a negative stability margin than the stabilator trimmedcase.
The lateral eigenvalues are well behaved, considerately separating into the conventionalspiral mode, roll mode, and Dutch roll pair. The spiral mode remains stable (Fig. 14), as doesthe roll mode which is shown in Fig. 15 and the Dutch roll pair whose real and imaginary partsare plotted as a function of flight condition number in Fig. 16. Dutch roll damping also seemsadequate.
The longitudinal eigenvalues were not so readily identifiable. Fig. 17 shows the real partof the most unstable longitudinal eigenvalue. Fig. 18 gives a scatter plot of all the longitudinaleigenvalues with the two trim paradigms plotted separately. The raw eigenvalue data are tabulatedat the end of this report.
AcknowledgementThe authors are grateful to Dr. Christopher Gracey of NASA Langley Research Center for
his help in locating data for this study and in formulating the approach.
References
[1] Rajiv Singh Chowdhry and Carey Buttrill, “Reference-H Assessment: Bare Airframe Stabilityand Trim Drag Reduction,” Memo to GFC ITD, September 13, 1995.
[2] “High Speed Civil Transport Reference H – Cycle 3 Simulation Data Base.” A Boeing reportfor NASA Contract NAS1-20220, Task Assignment No. 36, WBS 4.3.5.1.2.1.
[3] “High Speed Research Program HSR II – Airframe task 20; Task 2.1 – Technology Integration;Sub-task 2.1.1.1 Refine Technology Concept Airplane: Configuration Description Document;Deliverable Report.” Approved by J. B. Coffey, BCAG; J. K. Wechsler, MDC; P. F. Sweetland,BCAG; H. R. Welge, MDC. Prepared for NASA Langley Research Center, NASA ContractNAS1-20220. April 1, 1996.
[4] Rajiv S. Chowdhry, “User’s Manual for MATLAB ReferenceH Cycle 3 Simulation Software”,December, 1996.
5
0 10 20 30 40 50 60 70 800
0.5
1
1.5
2
2.5
Nominal mission flight condition number
Mac
h
Parameter defining nominal mission: Mach
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
Figure 1: Reference Mission Profile: Mach
6
0 10 20 30 40 50 60 70 800
1
2
3
4
5
6
7
x 104
Nominal mission flight condition number
Alti
tude
, ft
Parameter defining nominal mission: Altitude
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
Figure 2: Reference Mission Profile: altitude
7
0 10 20 30 40 50 60 70 803.5
4
4.5
5
5.5
6
6.5
x 105
Nominal mission flight condition number
Gro
ss w
eigh
t, lb
Parameter defining nominal mission: Gross weight
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
Figure 3: Reference Mission Profile: Gross Weight
8
0 10 20 30 40 50 60 70 80−60
−40
−20
0
20
40
60
80
100
Nominal mission flight condition number
Rat
e of
clim
b, ft
/sec
Parameter defining nominal mission: Rate of climb
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
Figure 4: Reference Mission Profile: rate of climb
9
CG trimmed Stabilator trimmed
0 10 20 30 40 50 60 70 80−2
−1.5
−1
−0.5
0
0.5
1
1.5
Nominal mission flight condition number
Sta
bila
tor
com
man
d, d
eg
Trim variable "stabilator"
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
Figure 5: Trim settings of the stabilator
10
CG trimmed Stabilator trimmed
0 10 20 30 40 50 60 70 80
48
50
52
54
56
58
60
62
Nominal mission flight condition number
x_cg
, % M
AC
Trim variable "X_CG"
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
Figure 6: Trim settings of the X-CG
11
CG trimmed Stabilator trimmed
0 10 20 30 40 50 60 70 80400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
Nominal mission flight condition number
u, ft
/sec
Trim variable "u"
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
Figure 7: Trim settings of the x-velocity
12
CG trimmed Stabilator trimmed
0 10 20 30 40 50 60 70 8020
40
60
80
100
120
140
160
Nominal mission flight condition number
w, f
t/sec
Trim variable "w"
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
Figure 8: Trim settings of the z-velocity
13
CG trimmed Stabilator trimmed
0 10 20 30 40 50 60 70 800
2
4
6
8
10
12
14
16
Nominal mission flight condition number
The
ta, d
eg
Trim variable "Theta"
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
Figure 9: Trim settings of the Euler pitch angle
14
CG trimmed
Stabilator trimmed
Fixed
0 10 20 30 40 50 60 70 800
10
20
30
40
50
60
70
80
90
100
Nominal mission flight condition number
Pow
er le
ver
setti
ng, %
of m
ax
Throttle: Fixed in segments 1, 3, 5; variable in segments 2, 4
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
Figure 10: Trim settings of the throttle
15
CG trimmed
Stabilator trimmed
Fixed
0 10 20 30 40 50 60 70 80−8
−6
−4
−2
0
2
4
6
Nominal mission flight condition number
V_T
dot
, ft/s
ec/s
ec
Total acceleration
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
Figure 11: _VT
16
Trim with x_cg Trim with DSTAB
0 10 20 30 40 50 60 70 800.01
0.015
0.02
0.025
0.03
0.035
0.04
Nominal mission flight condition number
C_D
Drag coefficient
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
Figure 12:CD
17
CG trimmed Stabilator trimmed
0 10 20 30 40 50 60 70 80−10
−5
0
5
10
15
Nominal mission flight condition number
Sta
bilit
y m
argi
n, %
MA
C
Stability margin of trimmed aircraft
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
Figure 13: Stability Margin
18
CG trimmed Stabilator trimmed
0 10 20 30 40 50 60 70 80−0.07
−0.06
−0.05
−0.04
−0.03
−0.02
−0.01
0
Nominal mission flight condition number
Spi
ral m
ode
eige
nval
ue
Lateral Eigenvalues: spiral mode
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
Figure 14: Lateral Eigenvalues: Spiral mode
19
CG trimmed Stabilator trimmed
0 10 20 30 40 50 60 70 80−2
−1.8
−1.6
−1.4
−1.2
−1
−0.8
−0.6
−0.4
Nominal mission flight condition number
Rol
l mod
e ei
genv
alue
Lateral Eigenvalues: roll mode
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
Figure 15: Lateral Eigenvalues: Roll mode
20
CG trimmed Stabilator trimmed
0 10 20 30 40 50 60 70 80−0.2
−0.15
−0.1
−0.05
Nominal mission flight condition number
Rea
l par
t
Lateral Eigenvalues: Dutch roll pair
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
0 10 20 30 40 50 60 70 800.7
0.8
0.9
1
1.1
1.2
Nominal mission flight condition number
Imag
inar
y pa
rt
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
Figure 16: Lateral Eigenvalues: Dutch roll pair
21
CG trimmed Stabilator trimmed
0 10 20 30 40 50 60 70 80−0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
Nominal mission flight condition number
Rea
l par
t
Maximum real part of longtitudinal eigenvalue
Segment 1 Seg. 2 Seg. 3 Seg. 4 Seg. 5
Figure 17: Longitudinal Eigenvalues: Real part of most unstable
Table 4 (continued). Longitudinal eigenvalues, Stabilator trimmed case
31
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Cg/Stability Map for the Reference H Cycle 3 Supersonic Transport ConcAlong the High Speed Research Baseline Mission Profile
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Daniel P. Giesy and David M. Christhilf
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3. ABSTRACT (Maximum 200 words)
A comparison is made between the results of trimming a High Speed Civil Transport (HSCT) concept alongerence mission profile using two trim modes. One mode uses the stabilator. The other mode uses fore and ament of the center of gravity. A comparison is make of the throttle settings (cruise segments) or theacceleration (ascent and descent segments) and of the drag coefficient. The comparative stability of trimminthe two modes is also assessed by comparing the stability margins and the placement of the lateral and longeigenvalues.
4. SUBJECT TERMS 1
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High Speed Civil Transport; High speed supersonic transport; Longitudinal trVariable center of gravity; Stability
ATION 2
SP2
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tandard Form 298 (Rev. 2-89)rescribed by ANSI Std. Z39-1898-102