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Scalability of RC aircraft
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Page 1 Microsystems & Electronics; Optronic Systems & Signal Processing
Scalability of Model Flight Test ResultsR. Arning
DGLR-Workshop on System Identification, Parameter Estimation and Optimisation
Ottobrunn, June 9th, 2005
Ingenieurbro Dr. Richard K. Arning
Page 2 Microsystems & Electronics; Optronic Systems & Signal Processing
Overview Overview
Motivation of scaled model flight testing
Applicability of method
Quality influences
Results
Page 3 Microsystems & Electronics; Optronic Systems & Signal Processing
Applicability of methodApplicability of method
Quality and relevance vs. model size ?
X-38ALFLEX
F-18
X-33NASA
NASA
NASA
Page 4 Microsystems & Electronics; Optronic Systems & Signal Processing
Motivation of scaled model flight testingMotivation of scaled model flight testing
Advantages:
Full set (6-DOF) measurement of dynamic derivatives
No wind tunnel / sting mounting interference
Early flight data
Low cost
Low risk
Page 5 Microsystems & Electronics; Optronic Systems & Signal Processing
Applicability of methodApplicability of method
Regions of constructional realisation for dynamically scaled models below 200 N MTOW and 200 N/m2 wing loading
0
20
40
60
80
100
120
140
160
180
200
G[N
]
1 2 3 4 5Spannweite [m]
Segelflzg.
Motorsegler
Raumflzg.
0
20
40
60
80
100
120
140
160
180
200
1 2 3 4 5Spannweite [m]
Segelflzg.
Motorsegler
Sportflzg.+Transportflzg.
Verkehrsflzg.
Glider
SailplaneMotor GliderGeneral Aviation
Spaceplane
Airliner
Span [m]
W
e
i
g
h
t
[
N
]
Limit for airliner models due to extreme high wing loading;
In general: To small Reynolds numbers
Wing loading for fighter aircraft models above limit
Page 6 Microsystems & Electronics; Optronic Systems & Signal Processing
Applicable to aircraft:
with relative low relative mass ratio:
at low speeds (uncompressible flow)
with acceptable chord length at scale sized (wing, tail)
Applicable to general aviation and below category aircrafts &
space planes during take-off and landing phase
NOT applicable: In stall region and for performance testing
Applicability of methodApplicability of method
bSm
=
))original
1
altitude original
altitude model
5,1
original
modelmodel ReRe
=
ll
))
Page 7 Microsystems & Electronics; Optronic Systems & Signal Processing
RS 180 Sportsman1:4,8-scale
Tail-Spin testing Tail-Spin testing
Speed Canard1:4-scale
MS 893 Morane1:4-scale
ELAC1:31.3-scale
ASK-211:3-scale
PHOENIX1:7-scale
System identification of winglets influence
System identification(closed and open loop)
Proof-of Concept /Engine failure characteristics
System identification of airbrakes influence
TT-621:5-scale
Applicability of methodApplicability of method IngenieurbroDr. Richard K. Arning
Page 8 Microsystems & Electronics; Optronic Systems & Signal Processing
scale center of gravity
dynamically scaled mass m
dynamically scaled moments of inertia I
dynamically scaled control system (if relevant)
quality of sensors and calibration (integrated), redundancy of sensor information
additional external equipment (e.g. nose-boom)
simplification of aerodynamic model
coverage of flight envelope and maneuvers by recorded flight data
Quality influencesQuality influences
*lr
*lplll0ll rCpCCCCCC +++++=
Page 9 Microsystems & Electronics; Optronic Systems & Signal Processing
Sensors and data acquisition system
Telemetriebodenstation
Quality influencesQuality influences
Page 10 Microsystems & Electronics; Optronic Systems & Signal Processing
Quality influencesQuality influences
Sensors and data acquisition system
Page 11 Microsystems & Electronics; Optronic Systems & Signal Processing
Sensors and data acquisition system
Quality influencesQuality influences
150
200
250
300
350
400
K
[
P
a
/
V
]
D
-12.0 -8.0 -4.0 0.0 4.0 8.0 12.0
[]
= -5 = 0 = 5
= 10 = 15 = 20
= 25 = 30
Page 12 Microsystems & Electronics; Optronic Systems & Signal Processing
Sensors and data acquisition system
Quality influencesQuality influences
1.E-03
1.E-02
1.E-01
1.E+00
1 . E -03 1. E -02 1 . E -01 1. E +00 1. E +01 1 . E +02 1. E +03 1 . E +04 1. E +05
0.01
0.1
1
0.001
G
y
r
o
A
l
l
a
n
-
D
e
v
i
a
t
i
o
n
[
/
s
]
0.01
0.1
1
0.001
G
y
r
o
A
l
l
a
n
-
D
e
v
i
a
t
i
o
n
[
/
s
]
Gyro
Integration Time [s]
0.001 0.1 1 10 100 1000 104 1050.01
10-4
10-3
10-2
10-5 Ac
c
e
l
.
A
l
l
a
n
-
D
e
v
i
a
t
i
o
n
[
g
=
9
.
8
1
m
/
s
]
Accelerometer
Allan-plot of MEMS accelerometer and gyro
Page 13 Microsystems & Electronics; Optronic Systems & Signal Processing
Estimated 1-Sigma Value of measurement systemELAC 1997 2005 possible
rotational rates 1,5 /s < 0,5 /s
acceleration 0,05 g < 0,01 g
, 1 0,5 control surfaces deflection 0,3 0,3
dynamic pressure ? combine with vel. measurement
mass 10 g 2 gIx, Iy, Iz 3% 3%Ixz 2 deviation from main axis 1 Ixy, Iyz set to 0 measure
position of center of gravity 2 mm 1 mm ?
position of aerodynamic 30 mm 30 mm
measurements
Quality influencesQuality influences
Page 14 Microsystems & Electronics; Optronic Systems & Signal Processing
Example: Minaturised control system
Quality influencesQuality influences
Autopilot HW with fully integrated MEMS-based flight control sensors, 100 Hz control frequency
Weight < 25 grams
Micro UAV: DO-MAV
500 grams
0,42 m span
Page 15 Microsystems & Electronics; Optronic Systems & Signal Processing
ELAC-space plane configuration with additional external installations(e.g. noseboom, skids)wind tunnel model scale factor 1:65
ELAC-space plane configuration free flyingmodel (rudderactuation)
Quality influencesQuality influences
Page 16 Microsystems & Electronics; Optronic Systems & Signal Processing
-0,20
-0,15
-0,10
-0,05
0,00C [-]l
6,0 8,0 10,0 12,0 14,0 16,0 [-]
Freiflug
Windkanal
-0,8
-0,6
-0,4
-0,2
0,0C [-]l
6,0 8,0 10,0 12,0 14,0 16,0 [-]
Freiflug
Windkanal
0,00
0,02
0,04
0,06
0,08
0,10C [-]l
6,0 8,0 10,0 12,0 14,0 16,0 [-]
Freiflug
Windkanal
-0,40
-0,30
-0,20
-0,10
0,00C [-]lp
6,0 8,0 10,0 12,0 14,0 16,0 [-]
Freiflug
Windkanal
0,0
0,2
0,4
0,6
0,8
1,0C [-]lr
6,0 8,0 10,0 12,0 14,0 16,0 [-]
Freiflug
Vortex-Lattice
Comparison of roll moment derivatis btweenflight test and wind tunnelmeasurements
Results: Comparison wind tunnel / free flightResults: Comparison wind tunnel / free flight
Page 17 Microsystems & Electronics; Optronic Systems & Signal Processing
From differences in wind tunnel and flight tests derived parameter uncertainties of rolling damping moment coefficient for space plane X-33
(Cobleigh: Development of the X-33 Aerodynamic Uncertainty ModelNASA TP-1998-206544, April 1998)
Results: Comparison with literature about deviation of wind tunnel and free flight dataResults: Comparison with literature about deviation of wind tunnel and free flight data
Page 18 Microsystems & Electronics; Optronic Systems & Signal Processing
Results: Comparison with literature about typical deviation of wind tunnel and free flight dataResults: Comparison with literature about typical deviation of wind tunnel and free flight data
FALKE-Orbiter Space-Shuttle Orbiter
Study 1 Study 2 ELAC model
AC +0.08 +/- 0.050 +0.008 +0.036 AC +12.5% +0.8% +15.7%
WC -0.04 +0.07 +/- 0.0125 -0.010 +0.036mC +0.008 +/- 0.022 +/- 0.008 -0.009 -0.001 mC -5% -20% +40% +/- 28% -6.4% +0.3%
mqC +/- 80% -33.3% -19.2%mqC VL +13.0% +19.1%mqC DC -10.0% -1.2% QC -15% +/- 25% -0.140 +0.200 0.067 0.104 QC +/- 0.028 0.043 0.063 QC +/- 0.086 -0.046 -0.030 lC +0.024 +/- 0.030 +/- 0.045 0.001 0.042 lC -10% -25% +40% +/- 25% -10.8% 4.2% lC -6% -30% +60% +/- 0.011 -0.040 -0.200
lpC -16 +57% -40% +70% -1.2% 16.6%lrC VL -200% +150% 36.0% 152.7% nC +0.009 +/- 0.030 -0.065 +0.046 -0.070 -0.007 nC +/- 0.024 +/- 0.017 -0.056 -0.025 nC -17% -30% +60% +/- 26% -41.3% -25.2%
npC VL -200% +100% -42.4% -13.9%nrC +/-4% -35% +40% -27.5% 0.5%
VL: Vortex-Lattice DC: DATCOM-Methode
Page 19 Microsystems & Electronics; Optronic Systems & Signal Processing
Comparison of ELAC result (deviation modelflight testing / wind tunnel) with parameteruncetainties from literature for X-33
Results: Comparison with literature about typical deviation of wind tunnel and free flight data
Results: Comparison with literature about typical deviation of wind tunnel and free flight data
-150
-100
-50
0
50
100
150
200
250
300[
%
]
C
A
C
W
C
m
C
m
C
W
K
m
q
C
V
L
m
q
C
D
C
m
q
-400
-300
-200
-100
0
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300
[
%
]
C
Q
C
Q
C
Q
C
l
C
l
C
l
C
l
p
C
V
L
l
r
C
n
C
n
C
n
C
V
L
n
p
C
n
r
Page 20 Microsystems & Electronics; Optronic Systems & Signal Processing
Method is applicable to subsonic/low speed flight regime and configurations with specific lower mass density (e.g. GA)
Quality of miniaturised (low-cost) sensors (drift & sensitivity) has been improved significantly over the recent years; aerodynamic sensors and nose-boom integration remain challenging
Even miniaturised autopilots are available today to investigate configurations with closed control loop and realistic position of center of gravity
For applications to determine the quasi-unsteady aerodynamics of these configuration the method is reliable enough today
SummarySummary