NASA Langley Research Center October 16, Strut-Braced Wing Transport NAS DA17

Transcription

1 NASA Langley Research Center October 16, 1998

2 Introduction Equal basis comparison of advanced conventional, box wing & strut-braced wing transports Parallel study contracts DA16 Box Wing Transport Study DA17 Strut Braced Wing Transport Study Common design requirements Common technology basis 1995 Baseline 2010 Advanced Technology Suite 2

3 LMAS and VPI IPT Lockheed Martin Aeronautical Systems / Virginia Tech Integrated Product Team LMAS Program Manager VPI Steve Justice Bernard Grossman LMAS Design VPI Deputy Program Manager LMAS Structures VPI Jeff Romantic Bill Mason Bruce Kopec Bob Olliffe Rakesh Kapania LMAS Sizing VPI Integration LMAS Mass Properties VPI Aaron Harcrow Bill Mason Kenneth Martin Tim McLendon Rakesh Kapania LMAS Aerodynamics VPI Bob Coopersmith Bill Mason Avionics Joe McInturff LMAS Manufacturing VPI Kathy Jacobson Bill Mason LMAS Stability & Control VPI Cost LMAS Propulsion VPI Buckley Stamps Bill Mason Stan Giglio Dave Gorz Joe Schetz 3

4 Program Objectives Identify key structural and aerodynamic design features, enabling technologies, and technological challenges for a strut-braced wing transport Assess the benefits obtained by integration of emerging technologies with structurally innovative clean sheet aircraft concepts Compare the benefits of a clean sheet design to the benefits obtained with the same technologies on a conventional baseline transport aircraft 4

5 NASA Three Pillar Goals Addresses Parts of Pillar One and Pillar Two of the NASA Three Pillars for Success SAFETY Reduce the aircraft accident rate by a factor of five within 10 years, and by a factor of 10 within 20 years. NOISE Reduce the perceived noise levels of future aircraft by a factor of two from today s subsonic aircraft within 10 years, and by a factor of four within 20 years. EMISSIONS Reduce emissions of future aircraft by a factor of three within 10 years, and by a factor of five within 20 years. COST OF AIR TRAVEL Reduce the cost of air travel by 25% within 10 years, and by 50% within 20 years. CAPACITY While maintaining safety, triple the aviation system throughput, in all weather conditions, within 10 years. DESIGN & TEST Provide next generation design tools and experimental aircraft to increase design confidence,and cut the development cycle time for aircraft in half. 5

6 Background Werner Pfenninger proposes a strut-braced wing, 1954 Low parasite drag leads to need for low induced drag Struts allow wing span to increase, thickness to decrease Werner Pfenninger Concept Boeing study: , AFFDL Report TR-76-65, 1977 NASA System Studies: 1980, 1981 Results: Requires careful technology integration between aerodynamics and structures, but has promise Pfenninger persists, letter to Goldin in 1990 s 6

7 Strut-Braced Wing Advantages from VPI Studies The strut increases the structural efficiency of the wing Tip-mounted engines: wing weight reduced by 30% with sub-200 foot span Under-wing engines: span increased to 259 ft., 14% reduction in wing weight Wing t/c reduced without a weight penalty Lower weight and increased span reduce induced drag Reduced t/c allows less sweep without wave drag penalty Parasite drag is reduced via increased laminar flow Un-sweeping the wing reduces cross-flow instability Higher aspect ratio means smaller chords and smaller Re 7

8 Study Process SBW Tasks Review,Modify, &Verify MDO Tool Develop Initial SBW Concept Develop Baseline Configuration Develop Adv. Conventional Configuration Size & Optimize SBW Concept Cost Analysis Tech Sensitivity Select 1995 & 2010 Technology Suites Box Wing Tasks Concept Comparisons 8

9 Design Mission >31,000 FT Initial Cruise Altitude Mach 0.85 Cruise 140 Knot Approach Speed 11,000 FT T/O Field Length 7,500 NMi Range 11,000 FT LDG Field Length Two GE-90 Class Engines 325 Passengers - Three Class 4,000 Mile Economic Range 9

10 Aircraft Configuration Roadmap Task DA16 Task DA Pax Conventional 325 Pax SBW (2 Eng Loc s) Downselect Optimize 325 Pax Box Wing Optimize Pax Conventional Pax Conventional 600 Pax Box Wing Optimize 10

11 1995 Baseline Configuration Length ft. Span ft. Wing Area 5,584.3 ft. 2 H-Tail Area 1,410.0 ft. 2 V-Tail Area ft. 2 Thrust (per ENG.) 97,540 lb Baseline Configuration Empty Weight Operating Weight Zero Fuel Weight Ramp Weight 333,055 lb. 350,834 lb. 419,084 lb. 714,499 lb. 11

12 Advanced Technology Downselect Process Technologies Applicable to Advanced Vehicle Concepts- Risk Cost Performance Safety Objective: Capture discipline expert s knowledge and judgment 2010 Technologies for 2015 Entry Into Service (EIS) Method for identifying technologies meeting affordability, performance and safety needs Highest ranked items included in study Technologies Applicable To Adv. Vehicle Concepts Availability / Risk Design Cycle & Cost Manufacturing / Cost Operations / Utilization Cost Technologies Importance Factor (TBD) Performance Safety Customer Pref./Necess. Risk/Cost/Perf Ranking Riblets (Paintless tech) FBL/PBW Fixed Leading Edges Simple High Lift - Simple Flaps Design Optimization Direct Lift Direct Side Force Advanced High Lift Active Gust Load Control Natural Laminar Flow Excrescence Drag Reduction Fast Acting Flaps Circulation Control All Flying Control Surfaces Active Flexible Wing Laminar FLow Control Relaxed Statc Stability

13 2010 Baseline Configuration Length ft. Span ft. Wing Area 4,672.0 ft. 2 H-Tail Area ft. 2 V-Tail Area ft. 2 Thrust (per ENG) 76,529 lb Baseline Configuration Empty Weight Operating Weight Zero Fuel Weight Ramp Weight 272,279 lb. 289,907 lb. 358,157 lb. 568,134 lb. 13

14 Engine Location Trade Study Configuration trade study examined strut & engine location Goal to determine configurations with minimum Engine-strut interference Wing mounted engines: Engine inboard of wing/strut intersect NO configurations without strut-engine interference Acoustic, thermal, buffet problems behind engine Engine at Wing/Strut Intersect Engine mount limit of 40% semi-span Wing-strut-pylon interference Fuselage Mounted Engines: Allows optimization of wing-strut system Wing-strut intersection initially set at 75% semi-span 14

15 Airline Interaction Ongoing Exchange with Delta Air Lines Very Productive Aircraft Engineering, Operations, Airport Services Represented 7500 Mi. & Ft TOFL Implies International Operations 4000 Mi. Average Stage Length 4400~5000 Hr./Yr. Average International Utilization Hr/Day, 1300 TO/LDG Cycles/Year Domestic HR/Day, 500 TO/LDG Cycles/Year International Pax Load / Unload Major Factor in Large A/C Turn Around Cargo (Not Baggage) Very Important Source of Revenue LD2 and LD3 Containers Span vs. Gate Spacing Possible Future Problem with Higher Capacity Aircraft Large A/C Alternate With Small Ones - Sometimes Wings Overlap 80 M (262.5 Ft) Box Probably a Good Limit to Use 15

16 Wing-Strut Attachment Minimum offset required for manufacturing Offset effects included in structural analysis Designed to minimize aerodynamic interference MDO used to optimize offset distance 16

17 Strut-Fuselage Attachment Strut damping system prevents sharp initiation of tension loads Prevents rapid, dynamic loading of strut Designed to take advantage of structural synergy with main landing gear frames 17

18 Optimized Strut-Braced Wing Concept Length ft. Span ft. Wing Area 4,237.3 ft. 2 H-Tail Area ft. 2 V-Tail Area ft. 2 Thrust (per ENG) 62,662 lb. Strut-Braced Wing Empty Weight Operating Weight Zero Fuel Weight Ramp Weight 249,670 lb. 267,350 lb. 335,600 lb. 504,835 lb. 18

19 Internal Cabin Layout 325 Passenger Three-Class Cabin Layout 24 First Class Passengers (55 in seat pitch) 49 Business Class Passengers (45 in seat pitch) 252 Coach Class Passengers (34 in seat pitch) 36 LD-3 Containers Below Passenger Deck 19

20 Airport Compatibility: Gate Spacing Comparison Strut-braced wing design is only slightly larger than current aircraft The concepts will not adversely affect airport operations or throughput Strut-braced wing span is slightly less than 2010 baseline configuration Base Strut Box 2010 Baseline 1995 Baseline 2010 Box Wing 20

21 Geometric Comparison Sized 325 Passenger Transports 1995 Conventional 2010 Conventional 2010 Strut-Braced Wing 2010 Box Wing Length Length Length Length Overall ft Overall ft Overall ft Overall ft Fuselage ft Fuselage ft Fuselage ft Fuselage ft Span Span Span Span Wing ft Wing ft Wing ft Wing (F) ft H-Tail 86.5 ft H-Tail 66.1 ft H-Tail 65.6 ft Wing (R) ft Height Height Height Height Overall 65.1 ft Overall 60.1 ft Overall 57.4 ft Overall 63.2 ft V-Tail 37.0 ft V-Tail 33.5 ft V-Tail 31.8 ft V-Tail 35.1 ft 21

22 Weight Comparison Sized 325 Passenger Transports 1995 Conventional 2010 Conventional 2010 Strut-Braced Wing 2010 Box Wing Ramp 714,499 lb. Ramp 568,134 lb. Ramp 504,835 lb. Ramp 535,963 lb. Fuel 295,415 lb. Fuel 209,977 lb. Fuel 169,235 lb. Fuel 186,821 lb. Zero Fuel 419,084 lb. Zero Fuel 358,157 lb. Zero Fuel 335,600 lb. Zero Fuel 349,142 lb. Pax/Cargo 68,250 lb. Pax/Cargo 68,250 lb. Pax/Cargo 68,250 lb. Pax/Cargo 68,250 lb. Op Equip 17,779 lb. Op Equip 17,628 lb. Op Equip 17,680 lb. Op Equip 17,603 lb. Empty 333,055 lb. Empty 272,279 lb. Empty 249,670 lb. Empty 263,289 lb. 22

23 DOC+I for Advanced Conventional 325 Pax A/C DOC+I ($/ASM) DOC+I Comparison Investment $ (55.2%) Fuel & Oil $ (16.5%) Maintenance $ Crew (17.0%) $ A/C Price Comparison (11.3%) % savings 19% savings A/C Price, $M Baseline Adv. Conv. Total DOC+I = $ / ASM Average A/C Price = $ 128 M 0 Baseline Adv. Conv. 23

24 DOC+I for Strut-Braced 325 Pax A/C Investment $ (56.3%) Fuel & Oil $ (14.5%) DOC+I, $/ASM DOC+I Comparison 26% savings Maintenance $ Crew (17.1%) $ (12.1%) A/C Price, $M A/C Price Comparison 23% savings 0 Baseline Strut-Braced Total DOC+I = $ / ASM Average A/C Price = $ 122 M 0 Baseline Strut-Braced 24

25 Cost Summary 0.06 DOC+I, ($/ASM) A/C Price, $M % Reduction % Reduction DOC+I, $/ASM A/C Price, $M Baseline Adv. Conv. 325 Pax Strut Wing 0 25

26 Sensitivity Study Technology Waterfall Natural Laminar Flow NLF TOGW = % 1995 Technology SBW TOGW=623,430 lb. Riblets Active Load Management All Moving Control Surfaces Composite Wing And Tails Integrally Stiffened Fuselage Skins Integrated Modular Flight Controls Fly-By-Light, Power-By-Wire Simple High-Lift Adv. Flight Mgt. Systems (Avionics) Propulsion SFC and Engine Systems AERO TOGW = % AIRFRAME -118,595 lb. (-19%) TOGW = % SYSTEMS TOGW = % PROPULSION TOGW = % 2010 Technology SBW TOGW = 504,835 lb. 26

27 Enabling Technologies Low cost composite structures Weight reduction while beating the cost of metallic structures Improve aeroelastic tailoring for thin wing & strut sections Advanced metallic structural concepts Advanced processes allow use of metals in areas unsuited to composites Weight savings comparable to composites Low drag airfoil design Natural laminar flow Thin wing section to reduce wave drag while maintaining high lift performance Fiber optic based flight controls & databus Reduced weight & volume Improved reliability & HIRF resistance 27

28 NASA Three Pillars Goals Impact Pillar One: Global Civil Aviation Improved systems technologies increase reliability & safety Reduced engine size & thrust reduces community noise Improved fuel efficiency reduces emissions by 42% Decreased direct operating cost of air travel (DOC+I) by 26% Aircraft size slightly larger than existing aircraft - minimal effect on airport capacity Pillar Two: Revolutionary Technology Leaps Increased confidence in concept as candidate for experimental aircraft 28

29 Issues Strut Load Environment Area equal to 100 passenger jet transport wing (~900 sq. ft) Designed for minimal airload & drag at cruise condition Significant inertia & airloads at off-design conditions Effects estimated using weight factors - more detailed analysis required Strut Design Strut currently modeled as tension only structural member Bending loads will have significant impact on strut stroke/damper system Update of design assumptions needed based on more realistic strut aerodynamic & inertia loads Wing/Strut Interaction Strut inference on wing high lift (flaps) undefined Impacts of strut inertia & airloads on wing & interface structure unknown Engine Integration Wing downwash and flap effects on fuselage mounted engines unknown 29

30 Future Work Detailed analysis of wing/strut system CFD analysis of aerodynamic loading on strut & wing at critical load cases FEM analysis with CFD generated airloads Revised wing structural weights based on FEM results Refine wing/strut interface design Aerodynamic design to reduce interference effects Structural design to accommodate revised wing/strut loads Wing & strut aeroelastic analysis Strut dynamics when unloaded in tension Effect of damper system Revised strut design Fixed vs. sliding strut design Integration with fuselage structure Minimize Flap/Strut Interference 30