Allen, Timothy

Bartels, Robert

Castelluccio, Mark

Claggett, Scott

Coulson, David

Dykman, John

Funk, Christie

Scott, Robert

Sexton, Bradley

NASA Technical Reports Server

1
Fixed Wing Project
Fundamental Aeronautics Program
National Aeronautics and Space Administration
Flutter and Aeroservoelastic Testing of the Boeing 
SUGAR Truss Braced Wing Aircraft
Presented by Robert Bartels
Robert Scott, Christie Funk, David Coulson, and Robert Bartels
NASA Langley Research Center 
Timothy Allen, Mark Castelluccio, Bradley Sexton, Scott Claggett and John Dykman
The Boeing Company
NASA ASE Summit, April 14, 2015
First presented at SD-13/GEPC-05. Special Session:  Subsonic Ultra Green Aircraft 
Research (SUGAR) Truss Braced Wing Aeroelasticity, SciTech 2015
https://ntrs.nasa.gov/search.jsp?R=20160007104 2019-08-31T02:47:48+00:00Z
2
Fixed Wing Project
Fundamental Aeronautics Program
Outline
• Phase I Findings, Phase II Objectives
• Experimental Validation, TDT Test
– Test Objectives
– Wind-Tunnel Model Design
– Transonic Dynamics Tunnel
– “Configurations” – GVT and FE Analyses
– Experimental Flutter Results
– Experimental ASE Results
• Phase II Findings
• Conclusions
3
Fixed Wing Project
Fundamental Aeronautics Program
TBW Phase I Findings, Phase II Objectives 
Phase I – Design Study of TBW Configuration
• Large uncertainty in wing weight estimates 
prevent concluding whether TBW is 
viable/beneficial concept
Conventional 
Configuration
TBW OEW 
Trade
Refined 
Conventional 
Config
20
30
40
50
60
70
80
90
120,000 140,000 160,000 180,000 200,000
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(
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TOGW (lb)
NASA Goal
U
pper W
eight Lim
it Goal
Baseline “SUGAR Free”
Conventional Configuration 
N
“SUGAR High”
Truss Braced Wing Configuration 
“Refined SUGAR”
Conventional Configuration 
N+3
Phase I
Phase II - Includes High Fidelity FEM to Refine Weight Estimate and 
Experimental Validation via ASE Wind-Tunnel Test in the TDT
N+3
4
Fixed Wing Project
Fundamental Aeronautics Program
Outline
• Phase I Findings, Phase II Objectives
• Experimental Validation, TDT Test
– Test Objectives
– Wind-Tunnel Model Design
– Transonic Dynamics Tunnel
– “Configurations” – GVT and FE Analyses
– Experimental Flutter Results
– Experimental ASE Results
• Phase II Findings
• Conclusions
5
Fixed Wing Project
Fundamental Aeronautics Program
Wind-Tunnel Test Objectives
• Determine Experimental Flutter 
Boundaries
• Investigate Active Flight Controls
- System ID
- Flutter Suppression 
- Assess Effects of FS on Gust   
Response
6
Fixed Wing Project
Fundamental Aeronautics Program
TBW Aeroelastic Wind-Tunnel Model
Full-Scale Design Point:
Mach = 0.82
Altitude = 15,915 ft
Span = 170 ft
Weight = 143,164 lb
Spar Pod Construction
Wing, Strut, Pylon Scaled
High Bandwidth Control Surfaces: 
2 Trailing Edge
Designed for Side Wall Mount
Fuselage 13.4 ft (reduced from 18.7 ft)
Span = 12.75 ft (to centerline)
Standoff = 2.25 in
Weight = 500 lb
Model Scale Factors:
Length = 0.15
Frequency = 3.470
Model Design Point
Gas = R134a
Scaled Weight = 109.63 lb
Mach = 0.82
Q=162 psf
Predicted Flutter Boundary
7
Fixed Wing Project
Fundamental Aeronautics Program
TBW Model Instrumentation
8
Fixed Wing Project
Fundamental Aeronautics Program
Transonic Dynamics Tunnel
9
Fixed Wing Project
Fundamental Aeronautics Program
TBW Modes and Frequencies
Wing 2nd out-of-plane bending mode Wing 1st torsion mode
10
Fixed Wing Project
Fundamental Aeronautics Program
Flutter Boundary Summary
11
Fixed Wing Project
Fundamental Aeronautics Program
Analysis/Test Comparison
12
Fixed Wing Project
Fundamental Aeronautics Program
Outline
• Phase I Findings, Phase II Objectives
• Experimental Validation, TDT Test
– Test Objectives
– Wind-Tunnel Model Design
– Transonic Dynamics Tunnel
– “Configurations” – GVT and FE Analyses
– Experimental Flutter Results
– Experimental ASE Results
• Phase II Findings
• Conclusions
13
Fixed Wing Project
Fundamental Aeronautics Program
ASE and CL Testing
• Open Loop System ID
– Sine sweeps to control surfaces for ASE model verification and system ID
– Dwell/Decay for estimating modal damping 
• Flutter Suppression Control Laws
– LQR based control law for each ASE model
– System ID based control law (2)
• Derived from two experimental data points
– Linear sine sweeps to each surface at two stable tunnel 
conditions
– AOA = -3°
– FEM 19 based control laws (18)
• ASE models derived from version 19 of NASTRAN FEM
• 18 ASE models used, including OL stable and unstable
– Control laws were scheduled based on Mach and dynamic pressure
• Gust Response
– Back to back OL and CL data points acquired with AOS frequency sweep
14
Fixed Wing Project
Fundamental Aeronautics Program
Closed Loop Results, AOA < 0
AOA -3
AOA -1
15
Fixed Wing Project
Fundamental Aeronautics Program
Closed Loop Results, AOA > 0
AOA +1
AOA +3
16
Fixed Wing Project
Fundamental Aeronautics Program
FEM19 Controller OL/CL @ Unstable Condition 
17
Fixed Wing Project
Fundamental Aeronautics Program
17
Flutter Suppression
6/6/2016
18
Fixed Wing Project
Fundamental Aeronautics Program
OL/CL Gust Response, FEM19 Based Control
19
Fixed Wing Project
Fundamental Aeronautics Program
Outline
• Phase I Findings, Phase II Objectives
• Experimental Validation, TDT Test
– Test Objectives
– Wind-Tunnel Model Design
– Transonic Dynamics Tunnel
– “Configurations” – GVT and FE Analyses
– Experimental Flutter Results
– Experimental ASE Results
• Phase II Findings
• Conclusions
20
Fixed Wing Project
Fundamental Aeronautics Program
Conclusions
• Open-Loop Flutter Boundaries Established
– Flutter Boundaries a Function of Aerodynamic Loading (Angle of Attack)
– Boeing NASTRAN/MDO Approach Validated/Improved
• Importance of Static Nonlinear Effects Established
• The TBW Configuration Remains A Viable Concept For Reducing Transport Aircraft Energy 
Consumption
• Flutter Suppression Control Laws Designed & Demonstrated
– Control Laws Designed using ASE Models Derived From Both Open-Loop 
Experimental Data and the NASTRAN FEM
– Close Loop Dynamic Pressures of at Least 25% Above the Open Loop 
Boundary Were Demonstrated
– Viability of Flutter Suppression for TBW N+3 Concept Established
– Flutter Suppression Controllers Provide Small Gust Load Alleviation Benefit
• Model Status
– Survived Several Hard Flutter Points
– NASA Retained Ownership, Available for Future Testing
• Documentation
– SciTech 2014 (2)
– Contractor Reports (2) 
– SciTech 2915 Special Session
– Aviation 2015 (1)
21
Fixed Wing Project
Fundamental Aeronautics Program
21Your Title Here
22
Fixed Wing Project
Fundamental Aeronautics Program
22Your Title Here
Backup Slides
23
Fixed Wing Project
Fundamental Aeronautics Program
Truss-Braced Wing: Wing Weight Uncertainty
PROBLEM
Conceptual design of Truss-Braced Wing (TBW) configuration during the N+3 
phase 1 study showed significant potential of this technology to contribute to 
meeting NASA N+3 goals, but also highlighted a significant uncertainty in the 
wing weight estimate.
OBJECTIVE
Refine the TBW configuration and reduce the uncertainty in the potential 
benefits with specific focus on reducing the uncertainty of the wing weight.
APPROACH
Create a detailed finite element model (FEM) of the TBW configuration to 
provide a higher fidelity weight estimate of the concept; validate the FEM via 
a transonic aeroservoelastic (ASE) test in the NASA Transonic Dynamics 
Tunnel (TDT).
RESULTS
A high fidelity weight estimate was completed which showed favorable wing 
weights and significant improvement in fuel burn. The ASE test was used to 
validate and update the wing weight estimate which increased 463 lbs
(12,577 lb wing).
SIGNIFICANCE
The TBW configuration remains a viable concept for reducing transport 
aircraft energy consumption. The validated detailed FEM enables credible 
weight and fuel burn estimates that justify further investigations of the TBW 
concept. Based on these results, an aerodynamic performance test and 
evaluation is going forward that will show that high-order aerodynamic design 
and analysis tools can be used to predict the performance of a low-
interference truss braced wing.
Phase IIPhase I
Conventional 
Configuration
TBW high 
fidelity
TBW OEW 
Trade
Refined 
Conventional 
Config
20
30
40
50
60
70
80
90
120,000 140,000 160,000 180,000 200,000
B
l
o
c
k
 
F
u
e
l
 
 
/
 
S
e
a
t
 
 
(
l
b
)
TOGW (lb)
NASA Goal
U
pper W
eight Lim
it Goal
24
Fixed Wing Project
Fundamental Aeronautics Program
Documentation
Contractor Final Reports
1. Bradley, M. K. and Droney, C. K., “Subsonic Ultra Green Aircraft 
Research: Truss Braced Wing Design Exploration,” Contractor report, 
The Boeing Company, June 2014.
2. Bradley, M. K., Droney, C. K., and Allen, T. J., “Subsonic Ultra Green 
Aircraft Research: Truss Braced Wing Aeroelastic Test Report,” 
Contractor report, The Boeing Company, June 2014
AIAA Conference papers
1. Coggin, J., Kapania, R., et. al., “Nonlinear Aeroelastic Analysis of a Truss 
Braced Wing Aircraft”, SciTech, No. AIAA-2014-0335, National Harbor, 
Maryland, January 2014.
2. Bartels, R. E., Scott, R. C., Allen, T., Sexton, B., and Funk, C., 
“Computed and Experimental Flutter/LCO Onset for the Boeing Truss-
Braced Wing Wind-Tunnel Model,” 32nd AIAA Applied Aerodynamics 
Conference, No. AIAA-2014-2446, Atlanta, GA, June 2014.
25
Fixed Wing Project
Fundamental Aeronautics Program
FY15 Documentation
• Contractor Final Report -> submit for publication as a NASA CR
• AIAA SciTech, January 2015
– Bradley, M., “Final Results of the Subsonic Ultra Green Aircraft Research 
(SUGAR) Study”
– Special Session Sponsored by SDTC & GEPC
1. Allen, Timothy J. [The Boeing Company], "SUGAR Truss Braced Wing Full Scale 
Aeroelastic Analysis and Dynamically Scaled Wind Tunnel Model Development”
2. Scott, Robert C. [NASA], "Aeroservoelastic Wind-Tunnel Test of the SUGAR 
Truss Braced Wing Wind-Tunnel Model”
3. Bartels, Robert E. [NASA], "Nonlinear Aeroelastic Analysis of SUGAR Truss-
Braced Wing Wind-Tunnel Model Using FUN3D”
4. Zhao, Wei [Virginia Tech], "Nonlinear Aeroelastic Analysis of SUGAR Truss-
Braced Wing (TBW) Wind-Tunnel Model (WTM) under In-plane Load”
5. Mallik, Wrik [Virginia Tech], "Aeroelastic Analysis and Optimization of Truss-
Braced Wing Aircraft with Novel Control Effectors”
6. Chen, P. C. [ZONA], "Low-Weight Low-Drag Truss-Braced Wing Design using 
Variable Camber Continuous Trailing Edge Flaps”
• AIAA Aviation, June 2015
– Bartels, R., Scott, R., and Funk, C. “Analysis of Limit Cycle Oscillation Data from 
the Aeroelastic Test of the Boeing SUGAR Vehicle”
26
Fixed Wing Project
Fundamental Aeronautics Program
Flow Through Nacelle and Active Control Surfaces
High Speed 
Aileron 
Low Speed Aileron 
Flow
Through 
Nacelle
Side-wall 
Mounted Strut 
Jury 
27
Fixed Wing Project
Fundamental Aeronautics Program
Boeing Weight Results with Resized FEM
Updated flutter penalty increases to 809 lb
28
Fixed Wing Project
Fundamental Aeronautics Program
Dynamically Scaled Model
R134a
29
Fixed Wing Project
Fundamental Aeronautics Program
Truss-Braced Wing: Wing Weight Uncertainty
Phase I Findings
Conceptual design of Truss-Braced Wing (TBW) configuration 
during the N+3 phase 1 study showed significant potential of this 
technology to contribute to meeting NASA N+3 goals, but also 
highlighted a significant uncertainty in the wing weight estimate.
Phase II Objectives
Refine the TBW configuration and reduce the uncertainty in the 
potential benefits with specific focus on reducing the uncertainty 
of the wing weight.
Phase II Approach
Create a detailed finite element model (FEM) of the TBW 
configuration to provide a higher fidelity weight estimate of the 
concept; validate the FEM via a transonic aeroservoelastic (ASE) 
test in the NASA Transonic Dynamics Tunnel (TDT).
Phase IIPhase I
Conventional 
Configuration
TBW high 
fidelity
TBW OEW 
Trade
Refined 
Conventional 
Config
20
30
40
50
60
70
80
90
120,000 140,000 160,000 180,000 200,000
B
l
o
c
k
 
F
u
e
l
 
 
/
 
S
e
a
t
 
 
(
l
b
)
TOGW (lb)
NASA Goal
U
pper W
eight Lim
it Goal
30
Fixed Wing Project
Fundamental Aeronautics Program
FEM 19 and FEM 20 Differences
v.19 FEM
v.20 FEM
Modes 3 and 4
coalesce to 
produce flutter/LCO
31
Fixed Wing Project
Fundamental Aeronautics Program
Skin / Pod Design
32
Fixed Wing Project
Fundamental Aeronautics Program
Wind-TunModel FEMs
FEM 19 “Pre Holiday”
FEM 20 “Post Holiday”
Modes 3 and 4
coalesce to 
produce flutter/LCO
33
Fixed Wing Project
Fundamental Aeronautics Program
Pre-Holiday Flutter w/ NASTRAN Analyses
34
Fixed Wing Project
Fundamental Aeronautics Program
NASTRAN Flutter Analysis
Typical Linear Analysis
35
Fixed Wing Project
Fundamental Aeronautics Program
Control Systems
36
Fixed Wing Project
Fundamental Aeronautics Program
Control Law Design Block Diagram


Flutter and Aeroservoelastic Testing of the Boeing SUGAR Truss Braced Wing Aircraft

Flutter and Aeroservoelastic Testing of the Boeing SUGAR Truss Braced Wing Aircraft

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