1. Cruise Efficient Short Take-Off and Landing (CESTOL)
Subsonic Transport System
(Revolutionary System Concepts for Aeronautics ’05)
Hyun Dae Kim
NASA Glenn Research Center
Jan. 26, 2006

2. Cruise Efficient Short Take-Off & Landing (CESTOL)
Background
Brief Concept Vehicle Description
Study Plan
Graphical Animation
Presentation by Boeing Technology / Phantom Works on Vehicle Configuration
Q & A

3. Description of the Problem
Cruise Efficient Short Take-Off & Landing (CESTOL)
Description of the Problem
Saturation of airports and the impact to the surrounding airspace and terrestrial communities are a rapidly increasing limit to world aviation travel. Subsonic commercial concepts appearing on the 25 year horizon must facilitate a more than 4X increase in air traffic, while complying with more stringent respect for the surrounding communities across the expanding world market.
Under-utilization of small regional airports (e.g., Cleveland’s Burke Lakefront Airport)
OBJECTIVE
Need fuel efficient low noise aircrafts that utilize small regional airports to address air traffic growth.
-> Low Noise Cruise Efficient STOL (CESTOL) Vehicle

4. Historical High Subsonic Transport Aircraft Configurations
Boeing 707
De Havilland Comet
Historically, there have been two distinctive commercial transport configurations.
One is a podded engine configuration like the original Boeing 707 and its derivatives.
The other is an embedded engine configuration like the British De Havilland Comet aircraft which later became current British Nimrod military aircraft.
Northrop YB-49

5. Cruise Efficient Short Take-Off & Landing (CESTOL)
New Vehicle Concept
Embedded Distributed Propulsion Vehicle will have:
High lift capability via spanwide vectored thrust providing powered and/or circulation control lift to enable STOL operation.
Efficient cruise performance through drag reduction by wing wake fill-in with engine thrust stream.
Reduction in aircraft noise through airframe shielding and acoustic treatment of the large available surface area of propulsion system.
Improvement in safety through a redundant multiple propulsion system.
Reduction or elimination of a number of aircraft control surfaces through differential and vectoring thrust for pitch, roll, and yaw moments.
Synergistic vehicle-propulsion integration is the key!
Now, here are the proposed concept description.
The Key to the concept is Synergistic ……
Thick wing/box structure weight savings
Weight savings thru common structure in inlets, wings, nozzles, etc.
No tail.
Significant drag reduction possilble
Increased internal drag
Engine maintenance diffuculty -> Not so. Engines can be installed between wing ribs and lowered thru lower wing surface.
Adverse flow interation between wing and propulsion aerodynamcs -> this can be overcome thru prudent CFD design.

6. Study Plan Task Organization Deliverables Date
Define mission design requirements
GRC/Boeing
Mission Req’s
7/30/05
Define vehicle configuration
Boeing
Vehicle Definition
10/30/05
1st order engine cycle analysis
GRC
Engine Deck
Explore noise benefits of distributed propulsion system
Diversitech
Detailed Final Report
1/31/06
Assess system benefits and perform comparison study
Assess noise benefits of the defined vehicle
Summarize results and recommend research approaches
All
Final Report

7. Graphical Animation of CESTOL Aircraft
At Cleveland’s Burke Lakefront Regional Airport

8. Cruise Efficient Short Take-Off and Landing (CESTOL)
Subsonic Transport System
(Revolutionary System Concepts for Aeronautics ’05)
Ronald Kawai
Boeing Technology/Phantom Works Huntington Beach

9. Study Scope Boeing Technology/Phantom Works Huntington Beach Creates
Revolutionary Concept and Develops Characteristics, Performance, and
Identifies Technology Needs for an Airplane Configuration Embodying
Very Low Noise Features Capable of Operations from Regional
Airports
NASA GRC Separate Contractor Quantifies Low Noise Potential

11. LITERATURE REVIEW Powered lift can provide high CL for STOL
Past STOL transport studies for regional/short range at cruise speeds
less than Mach 0.8
DSS turboprops have lowest GW & Cost but speed limited to below
Mach 0.7
Efficient Mach 0.8 possible with turbofans or UHB unducted fans
Mach 0.8 requires supersonic tip speed fans or counter-rotating fans
but the later have high take off and enroute noise
A shrouded fan, i.e. turbofan is needed for high speed with low noise
IBF/USB/Augmentor Wing have highest high lift efficiency

12. Other Studies Show
Internally Blow Flap Has
Better High Lift Performance
But Judged Complex

13. Extensive studies and analyses resulted in AF AMST program
fly-off between YC-14 and YC-15
IBF and Augmentor Wing ruled out by hot ducting complexity
YC-14 and YC-15 where straight wing airplanes
With efficient cruise below Mach 0.7

14. YC-14 Interior Noise
Peak at hz
AFFDL-TR

15. BOEING C-17A AF SELECTED THE C-17 WITH EBF TO BECOME THE ONLY
SUCCESSFUL LARGE TURBOFAN POWERED STOL TRANSPORT
(Swept Wing for Mach 0.74 – 0.77 Cruise, 2750 nmi range w/164,900 lb
payload, First flight Sept 15, 1991)
FUTURE STOL TRANSPORT CONCEPT IMROVEMENT OPPORTUNIES:
- IMPROVE CRUISE EFFICIENCY (INCREASE SPEED AND RANGE)
- LOWER NOISE

16. remain near constant with increased flight frequencies and city pairs
2005 Boeing Current Market Outlook
Extrapolation of growth forecast would predict average airplane size to
remain near constant with increased flight frequencies and city pairs
Future Demand continues for 90 to 175 passenger size
Operating from regional airports would relieve long pre-departure times

17. Noise Restrictions can be expected to escalate with increasing number of flights
Very low noise will be required to enable growth for expanded operations at
existing and new commercial airports while minimizing noise penalties

18. Including a minimum 100 ft runway width for larger aircraft
showed that 84% or 813 of 973 civil airports have 5,000 ft +
AIAA , Regional Jet Operational Improvements resulting from Short Field Performance and Design

19. Noise Footprint Would Be Very Important at Many Other Airports:
Expanded use of regional airports
Allow relaxation of curfews/operating at night
Allow increased operations per day
Allow conversion of military closing to commercial use
Neighbors want low noise regardless of airplane weight:
Goal should be cum noise as to Stage 3 minus XX

20. STOL to Reduce Noise Footprints
Rapid Climb Out
Steep Approach
Take Off
The BWB configurations studied have inherently much lower approach noise. The take-off noise benefits from no wing noise reflection..
Sideline
2000m
Approach

21. . TO .
Sideline
Approach
Low Sideline Noise would be of high value at Burke Lakefront Airport

22. Long Beach, CA Airport 10PM to 7AM curfew
41 flight/day limit can be raised if aircraft noise decreased

23. El Toro Marine Air Base in SoCal could not be converted to
relieve congestion at LAX because of neighborhood opposition

24. 2025+ Summary Traffic Growth Forecasts generally for next 20 years
For 2025+, extrapolate trends from Boeing Current Market Outlook
Noise sensitive regions are U.S. and Europe
Twin aisles and large airplanes for trans oceanic flights
Single aisle dominates size and generally with many more take-off
and landing operations/day than twin aisle and large aircraft
Reducing noise for greatest noise growth is thus single aisle
passenger size
Focus on high end for growth, 170 passenger size, but with BWB,
It becomes multiple aisle airplane
Study for use at regional airports for air traffic expansion that may
provide dual use technology for multi-role military applications

27. BLENDED WING BODY IS FUTURE CONCEPT FOR
IMPROVED EFFICIENCY AND LOWER NOISE
LOW NOISE FEATURES:
Forward noise shielding
No aft noise reflection
No flap noise
Low approach thrust
Body suppression of landing gear noise

28. Benefits From Embedded Distributed Propulsion
Embedded engines for quiet powered lift
Close coupled engine to slot with cold low pressure fan bleed
Smaller nozzle diameters for improved jet noise shielding
More rapid mixing moving jet noise source forward
Longer flap chord shielding / nozzle diameter
Increased atmospheric attenuation form higher frequency jet noise
Reducing engine size enables embedding in mid wing sections for more
forward Cp and Cg
Reduces the thrust of individual engines reducing engine out thrust
yaw control moments

29. Distributed propulsion:
Forward Fan Noise Shielding
Aft Turbo-machinery and Combustion Noise Shielding
Jet Noise Shielding
Chevrons for mixing
Fan Bleed IBF
Freestream Inlet
Distributed propulsion:
Smaller exhaust diameters enhances jet noise shielding
Smaller engines enable direct fan bleed for low pressure powered IBF
Slotted ejector reduces powered lift noise
Minimal engine out rolling moment with powered lift

30. Concept Development Process
SOW
2025 technology for traffic growth using untapped regional airspace
Cruise efficient configuration with Embedded Wing Propulsion
Review/Summarize Previous Studies
IBF most efficient powered lift for STOL
Mission Requirements for CESTOL
170 pax, 3,000 nmi, Mach 0.8
Very low noise
Minimum 5,000 ft TOFL
Define Configuration with STOL characteristics
WingMOD planform development
Digital configuration development
Assess System Benefits of Distributed Propulsion on CESTOL
Boeing Integrated Vehicle Design System (BIVDS) synthesis
Very low noise features on Quiet Powered Lift Concept
Foundational Technology Needs Outlined

31. WingMOD: Multidisciplinary Optimization
Configuration Estimate
Hard Constraints
Payload
Range
Approach Speed
etc.
Design Constraints
Running Loads
Buffet Characteristics
DFMA
etc.
Optimized Config.
WingMOD
Optimizer
Baseline Config.
Closed.
Balanced.
Trimmed.
Min. OEW
Aerodynamics
Vortex Lattice Model
Empirical Profile Drag, Compressibility Drag, & Sectional Maximum Lift
CFD, Wind Tunnel Calibration
Structures
Monocoque Beam Model
Stress & Buckling Sizing
Static Aeroelastics
Controls
Elevon Model
Balance Analysis
Configuration Layout

32. Quiet Distributed Propulsion Starting Point
Fan bleed slot ejector IBF for quiet powered lift
Short inlet diffuser w/AFC
Inlet and exhaust noise shielding
IBF sizing 12 x 6 K lb thrust engines
Slot width per engine = 68.1 in
Slot height = 2.36 in
Fan pressure ratio = 1.69
4 engines
4 engines
4 engines
Injection
Slots in in
137 ft
100 optimization runs to evolve controllable planform

33. Configuration Components – All
Basic Airframe
Upper Deck
Avionics
Air Conditioning
Lower Deck
Landing Gear
Furnishings & Standard Items
Anti-Icing
Operational Items
Propulsion
Electrical
Inboard Fuel
Instruments
Outboard Fuel
Fuel System
Surface Controls
Hydraulic, Pneumatic, APU

34. Control Surface Usage
Lift effectors geared to pitch effectors -0.64:1 for trim, 0.44:1 for control
10.2 deg flap deflection on lift effectors
Transition flap geared to pitch effectors -0.29:1 for trim, 0.16:1 for control
Lift effect, pitch and roll control
Yaw and roll control
Pitch and roll control
Pitch control

37. BIVDS Evaluation Mission Performance
EWP Design
500 nm
150 nm
Range (nm)
3,000
500
150
Payload (lb)
40,000
Takeoff Gross Weight (lb)
189,140
157,874
152,835
Landing Weight (lb)
152,548
151,052
150,866
Total Fuel (lb)
44,098
12,832
8,793
Block Fuel (lb)
37,723
7,946
4,098
Block Time (h)
6.92
1.48
0.68
Initial Cruise Altitude (ft)
39,000
43,000
31,000
Takeoff Field Length (ft)
2,452
1,772
1,694
Landing Field Length (ft)
3,477
3,457
3,454
Takeoff CLmax Liftoff
1.66
1.80
1.83
Takeoff CLmax Obstacle
1.57
1.65
Landing CLmax
1.06

38. Segment Climb 1st and 2nd Accel to Final Climb Speed TO
Performance analyses resulted in about the same take-off flight paths with the same altitude over the take-off measuring point at 6,500 m or 21,325 ft from brake release

39. Very Low Noise Features
3,500 ft TOFL
Embedded Distributed
propulsion enables
quiet powered lift
with jet noise shielding
Rapid Climb (3000+ ft over T.0. noise point)
Could Use Cutback
or Higher Altitude Before Acceleration to Climb Speed
Steep Descent (6 degree glide slope)
Forward
Noise
Shielded
Aft Noise
Shielded
Consider Part
Span Verticals
to Improve Sideline
Shielding if Necessary
Note: Powered lift is off during climb
Differential elevons positions could be optimized for noise shielding
Boeing Technology/Phantom Works Huntington Beach provides mission
data for very low noise concept for NASA to make noise assessment

40. Foundational Technologies Needed
Noise Shielding Codes
Reflections
Turbo-machinery noise
Jet noise
Inlet/airframe Aero Integration
Inlets in high Mach flow field
Quiet Powered Lift:
Low Pressure IBF performance and noise
Revolutionary Engine Concepts
Short Cruise Efficient
Variable Geometry Noise Reflection Nozzles
Forward noise source
Flow Control Inlets
Active, Passive and Hybrid Evaluations

41. Reduce Nozzle Height and Create Vortices to Move Jet Noise Source Forward

42. Need Small Turbofan for X-48B
Foundational Technology for Jet Noise Shielding
Shielded Jet Noise Nozzle
CFD Development
Shielding Code Development
Calibration Wind Tunnel Tests
Model Tests
Flight Validations
Small Turbofan(s)
Current X-48B program to validate
low speed characteristics
Modify with quiet turbofan
for very low noise and IR
validation

43. Conclusions
Continuing growth in air travel demand is forecast. This growth is expected to increase
daily departures operating from an increasing number of city pairs.
This growth is forecast to go with increasing GDP providing a need for very quiet airplane
operating from regional airports which can have current economics
Studies have shown eliminating noise reflections while providing noise shielding can
significantly reduce flyover noise
Extending these principals to jet noise source downstream in the exhaust wake
should provide more dramatic noise reductions
Large surface area planforms such as the BWB provides opportunities for increased
source noise shielding
Embedded distributed propulsion offers the potential for quiet powered lift with jet noise
shielding for small noise footprints operating from regional airports
Configuration studies were made to evolve a BWB STOL planform that is trimmable
with total noise shielding
Low noise footprints would also have low IR footprints for passive protection from terrorists
Development of foundational technologies are needed that would be generic and dual use