Digital DATCOM Data
Digital DATCOM Data Overview
The Aerospace Toolbox product enables bringing United States
Air Force (USAF) Digital DATCOM files into the MATLAB® environment
by using the datcomimport function. For more
information, see the datcomimport function
reference page. This section explains how to import data from a USAF
Digital DATCOM file.
The example used in the following topics is available as an Aerospace Toolbox example.
You can run the example by entering astimportddatcom in
the MATLAB Command Window.
USAF Digital DATCOM File
The following is a sample input file for USAF Digital DATCOM
for a wing-body-horizontal tail-vertical tail configuration running
over five alphas, two Mach numbers, and two altitudes and calculating
static and dynamic derivatives. You can also view this file by entering type astdatcom.in in
the MATLAB Command Window.
$FLTCON NMACH=2.0,MACH(1)=0.1,0.2$ $FLTCON NALT=2.0,ALT(1)=5000.0,8000.0$ $FLTCON NALPHA=5.,ALSCHD(1)=-2.0,0.0,2.0, ALSCHD(4)=4.0,8.0,LOOP=2.0$ $OPTINS SREF=225.8,CBARR=5.75,BLREF=41.15$ $SYNTHS XCG=7.08,ZCG=0.0,XW=6.1,ZW=-1.4,ALIW=1.1,XH=20.2, ZH=0.4,ALIH=0.0,XV=21.3,ZV=0.0,VERTUP=.TRUE.$ $BODY NX=10.0, X(1)=-4.9,0.0,3.0,6.1,9.1,13.3,20.2,23.5,25.9, R(1)=0.0,1.0,1.75,2.6,2.6,2.6,2.0,1.0,0.0$ $WGPLNF CHRDTP=4.0,SSPNE=18.7,SSPN=20.6,CHRDR=7.2,SAVSI=0.0,CHSTAT=0.25, TWISTA=-1.1,SSPNDD=0.0,DHDADI=3.0,DHDADO=3.0,TYPE=1.0$ NACA-W-6-64A412 $HTPLNF CHRDTP=2.3,SSPNE=5.7,SSPN=6.625,CHRDR=0.25,SAVSI=11.0, CHSTAT=1.0,TWISTA=0.0,TYPE=1.0$ NACA-H-4-0012 $VTPLNF CHRDTP=2.7,SSPNE=5.0,SSPN=5.2,CHRDR=5.3,SAVSI=31.3, CHSTAT=0.25,TWISTA=0.0,TYPE=1.0$ NACA-V-4-0012 CASEID SKYHOGG BODY-WING-HORIZONTAL TAIL-VERTICAL TAIL CONFIG DAMP NEXT CASE
The output file generated by USAF Digital DATCOM for the same
wing-body-horizontal tail-vertical tail configuration running over
five alphas, two Mach numbers, and two altitudes can be viewed by
entering type astdatcom.out in
the MATLAB Command Window.
Data from DATCOM Files
Use the datcomimport function to bring
the Digital DATCOM data into the MATLAB environment.
alldata = datcomimport('astdatcom.out', true, 0);Imported DATCOM Data
The datcomimport function creates a cell
array of structures containing the data from the Digital DATCOM output
file.
data = alldata{1}
data =
struct with fields:
case: 'SKYHOGG BODY-WING-HORIZONTAL TAIL-VERTICAL TAIL CONFIG'
mach: [0.1000 0.2000]
alt: [5000 8000]
alpha: [-2 0 2 4 8]
nmach: 2
nalt: 2
nalpha: 5
rnnub: []
hypers: 0
loop: 2
sref: 225.8000
cbar: 5.7500
blref: 41.1500
dim: 'ft'
deriv: 'deg'
stmach: 0.6000
tsmach: 1.4000
save: 0
stype: []
trim: 0
damp: 1
build: 1
part: 0
highsym: 0
highasy: 0
highcon: 0
tjet: 0
hypeff: 0
lb: 0
pwr: 0
grnd: 0
wsspn: 18.7000
hsspn: 5.7000
ndelta: 0
delta: []
deltal: []
deltar: []
ngh: 0
grndht: []
config: [1x1 struct]
cd: [5x2x2 double]
cl: [5x2x2 double]
cm: [5x2x2 double]
cn: [5x2x2 double]
ca: [5x2x2 double]
xcp: [5x2x2 double]
cla: [5x2x2 double]
cma: [5x2x2 double]
cyb: [5x2x2 double]
cnb: [5x2x2 double]
clb: [5x2x2 double]
qqinf: [5x2x2 double]
eps: [5x2x2 double]
depsdalp: [5x2x2 double]
clq: [5x2x2 double]
cmq: [5x2x2 double]
clad: [5x2x2 double]
cmad: [5x2x2 double]
clp: [5x2x2 double]
cyp: [5x2x2 double]
cnp: [5x2x2 double]
cnr: [5x2x2 double]
clr: [5x2x2 double]Missing DATCOM Data
By default, missing data points are set to 99999 and data points are set to NaN where no DATCOM methods exist or where the method is not applicable.
It can be seen in the Digital DATCOM output file and examining the imported data that , , , and have data only in the first alpha value. Here are the imported data values.
data.cyb
ans(:,:,1) =
1.0e+004 *
-0.0000 -0.0000
9.9999 9.9999
9.9999 9.9999
9.9999 9.9999
9.9999 9.9999
ans(:,:,2) =
1.0e+004 *
-0.0000 -0.0000
9.9999 9.9999
9.9999 9.9999
9.9999 9.9999
9.9999 9.9999
data.cnb
ans(:,:,1) =
1.0e+004 *
0.0000 0.0000
9.9999 9.9999
9.9999 9.9999
9.9999 9.9999
9.9999 9.9999
ans(:,:,2) =
1.0e+004 *
0.0000 0.0000
9.9999 9.9999
9.9999 9.9999
9.9999 9.9999
9.9999 9.9999
data.clq
ans(:,:,1) =
1.0e+004 *
0.0000 0.0000
9.9999 9.9999
9.9999 9.9999
9.9999 9.9999
9.9999 9.9999
ans(:,:,2) =
1.0e+004 *
0.0000 0.0000
9.9999 9.9999
9.9999 9.9999
9.9999 9.9999
9.9999 9.9999
data.cmq
ans(:,:,1) =
1.0e+004 *
-0.0000 -0.0000
9.9999 9.9999
9.9999 9.9999
9.9999 9.9999
9.9999 9.9999
ans(:,:,2) =
1.0e+004 *
-0.0000 -0.0000
9.9999 9.9999
9.9999 9.9999
9.9999 9.9999
9.9999 9.9999The missing data points will be filled with the values for the first alpha, since these data points are meant to be used for all alpha values.
aerotab = {'cyb' 'cnb' 'clq' 'cmq'};
for k = 1:length(aerotab)
for m = 1:data.nmach
for h = 1:data.nalt
data.(aerotab{k})(:,m,h) = data.(aerotab{k})(1,m,h);
end
end
endHere are the updated imported data values.
data.cyb
ans(:,:,1) =
-0.0035 -0.0035
-0.0035 -0.0035
-0.0035 -0.0035
-0.0035 -0.0035
-0.0035 -0.0035
ans(:,:,2) =
-0.0035 -0.0035
-0.0035 -0.0035
-0.0035 -0.0035
-0.0035 -0.0035
-0.0035 -0.0035
data.cnb
ans(:,:,1) =
1.0e-003 *
0.9142 0.8781
0.9142 0.8781
0.9142 0.8781
0.9142 0.8781
0.9142 0.8781
ans(:,:,2) =
1.0e-003 *
0.9190 0.8829
0.9190 0.8829
0.9190 0.8829
0.9190 0.8829
0.9190 0.8829
data.clq
ans(:,:,1) =
0.0974 0.0984
0.0974 0.0984
0.0974 0.0984
0.0974 0.0984
0.0974 0.0984
ans(:,:,2) =
0.0974 0.0984
0.0974 0.0984
0.0974 0.0984
0.0974 0.0984
0.0974 0.0984
data.cmq
ans(:,:,1) =
-0.0892 -0.0899
-0.0892 -0.0899
-0.0892 -0.0899
-0.0892 -0.0899
-0.0892 -0.0899
ans(:,:,2) =
-0.0892 -0.0899
-0.0892 -0.0899
-0.0892 -0.0899
-0.0892 -0.0899
-0.0892 -0.0899Aerodynamic Coefficients
You can now plot the aerodynamic coefficients:
Plotting Lift Curve Moments
h1 = figure;
figtitle = {'Lift Curve' ''};
for k=1:2
subplot(2,1,k)
plot(data.alpha,permute(data.cl(:,k,:),[1 3 2]))
grid
ylabel(['Lift Coefficient (Mach =' num2str(data.mach(k)) ')'])
title(figtitle{k});
end
xlabel('Angle of Attack (deg)')
Plotting Drag Polar Moments
h2 = figure;
figtitle = {'Drag Polar' ''};
for k=1:2
subplot(2,1,k)
plot(permute(data.cd(:,k,:),[1 3 2]),permute(data.cl(:,k,:),[1 3 2]))
grid
ylabel(['Lift Coefficient (Mach =' num2str(data.mach(k)) ')'])
title(figtitle{k})
end
xlabel('Drag Coefficient')
Plotting Pitching Moments
h3 = figure;
figtitle = {'Pitching Moment' ''};
for k=1:2
subplot(2,1,k)
plot(permute(data.cm(:,k,:),[1 3 2]),permute(data.cl(:,k,:),[1 3 2]))
grid
ylabel(['Lift Coefficient (Mach =' num2str(data.mach(k)) ')'])
title(figtitle{k})
end
xlabel('Pitching Moment Coefficient')