UNPUBLISHED UNITED STATES COURT OF APPEALS FOR ..., Study Guides, Projects, Research of Law

Download UNPUBLISHED UNITED STATES COURT OF APPEALS FOR ... and more Study Guides, Projects, Research Law in PDF only on Docsity! NASA CR137525 VOLUME I EVALUATION OF ADVANCED LIFT CONCEPTS nm ~' o FUEL CONSERVATIVE SHORT-HAUL AIRCRAFT A FINAL REPORT o wD"I- . t JUNE 1974 W ,.o l a - TO: NATIONAL AERONAUTICS AND SPACE ADMINISTRATION m SYSTEMS STUDIES DIVISION . AMES RESEARCH CENTER Contract NAS 2-6995 om BY: LOCKHEED AIRCRAFT CORPORATION 7 ' w c"-4 NASA CR137525 VOLUME I EVALUATION OF ADVANCED LIFT CONCEPTS AND FUEL CONSERVATIVE SHORT-HAUL AIRCRAFT FINAL REPORT JUNE 1974 TO: NATIONAL AERONAUTICS AND SPACE ADMINISTRATION SYSTEMS STUDIES DIVISION AMES RESEARCH CENTER ' Contract NAS 2-6995 BY: LOCKHEED AIRCRAFT CORPORATION LACKNEEn Page 3.3 Operational Qualities 27 3.4 Noise Criteria 28 3.5 Economic Evaluation Criteria 29 Section 4.0: Over-the-Wing/Internally Blown Flap (OTW-IBF) Vehicles 32 4.1 OTW-IBF Concept 32 4.2 OTW-IBF Propulsion Data 36 4.3 OTW-IBF Aerodynamic Data 68 4.4 OTW-IBF Baseline Mission Vehicles 100 4.5 OTW-IBF Fuel-Conservative Vehicles 123 4.6 OTW-IBF Mission Performance 165 4.7 OTW-IBF Handling and Ride Qualities 178 4.8 OTW-IBF Weight and Balance 202 4.9 Noise Analyses 220 4.10 OTW-IBF Design 232 VOLUME II Section 5.0: Augmentor Wing (AW) Vehicles 249 5.1 AW Concept 249 5.2 AW Propulsion System Data 255 5.3 AW Aerodynamic Data 269 5.4 Baseline Mission AW Vehicles 272 5.5 AW Fuel-Conservative Vehicles 314 5.6 Noise Analyses 340 vi Page Section 6.0: Mechanical Flap (MF) Vehicles 343 6.1 MF Concept 343 6.2 MF Propulsion Data 345 6.3 MF Aerodynamic Data 350 6.4 MF Baseline Mission Vehicles 356 6.5 MF Fuel-Conservative Vehicles 384 6.6 MF Handling Qualities 415 6.7 MF Weight and Balance 424 6.8 Noise Analyses 432 Section 7.0: Other Lift Concepts 442 7.1 Externally Blown Flap (EBF) Concept 442 7.2 Over-the-Wing (OTW) Concept 449 7.3 Boundary Layer Control (BLC) Concept 450 7.4 Internally Blown Flap (IBF) Concept 453 7.5 Deflected Slipstream Concept 456 7.6 EBF/OTW/Deflected Slipstream Noise 473 7.7 References Section 8.0: Evaluation of Aircraft Configurations 474 8.1 Design for Fuel Con servation 474 8.2 Design for Noise Constraints 493 Section 9.0: Airline Economics 503 9.1 STOL Aircraft Costs (DOC/IOC/ROI) 503 9.2 Return on Investment (ROI) 509 vii Page Section 10.0: Compromise Solutions 514 10.1 Compatibility of Selection Criteria 514 10.2 Recommended Compromise Concept 521 Section 11.0: Conclusions and Recommendations 522 11.1 Conclusions 522 11.2 Recommendations 526 Appendix A: OTW-IBF Noise Analysis Vehicles 529 Appendix B: MF Noise Analysis Vehicles 537 Appendix C: Turboprop Maintenance 545 References 548 viii LIST OF FIGURES (Continued) Figure Title Page 27 Comparison of Estimated Engine-Out Hybrid Data 80 28 Lockheed Powered Lift Model (Low Wing) 81 29 Lift Curve Comparison of OTW and IBF Systems 82 30 CL vs CT Comparison of Various OTW and IBF Systems 82 31 CX vs CT Comparison of Various OTW and IBF Systems 83 32 CX vs CL Comparison of Various OTW and IBF Systems 83 33 Lift Curve Comparison with Gelac Test 119 85 34 CL vs CT Comparison with Gelac Test 119 85 35 CL MAX vs CT Comparison with Gelac Test 119 86 36 CX vs CL Comparison with Gelac Test 119 86 37 OTW/IBF Basic Aero Data - Engine Out 87 38 OTW/IBF Basic Aero Data - 2 Engines 88 39 Comparison of Baseline OTW/IBF and MF Drag Polars 90 40 Upper Surface Integrated Nacelles 93 41 Upper Surface Pylon Nacelles 94 42 Drag Variations of Various Nacelle Configurations 95 43 Drag Variations of Integrated Nacelles on Modified Wing 97 44 Drag Increments for Several Nacelle/Wing Configurations 99 45 OTW/IBF: Baseline Flap and Duct Configuration 101 46 OTW/IBF: Maximum IBF Thrust Split 102 47 OTW/IBF: T/W vs W/S and IBF Thrust Split 103 48 OTW/IBF: Flap Angle Requirements (4-engines) 105 49 OTW/IBF: Field Performance Options 106 50 OTW/IBF: Optimum IBF Thrust Split 106 51 OTW/IBF: 2 Engine Configurations 107 52 OTW/IBF: 3 Engine Configurations 108 xi LIST OF FIGURES (Continued) Figure Title Page 53 OTW/IBF: 4 Engine Configurations 109 54 OTW/IBF: DOC vs Number of Engines 110 55 OTW/IBF Twin - DOC vs Aspect Ratio and 1/4C Sweep 110 56 OTW/IBF Twin - Ramp Gross Weight vs Aspect Ratio 112 57 OTW/IBF Twin - Mission Fuel vs Aspect Ratio 112 58 OTW/IBF Twin - DOC and Noise Level vs FPR 113 59 OTW/IBF Twin - Cruise and Takeoff Matching (FPR 1.35) 115 60 910m (3000 Ft.) OTW/IBF Vehicle 116 61 Computer Sizing Data: 2 Engine OTW/IBF ( 1.35 FPR, 118 910m (3000 Ft.) Field 62 Computer Sizing Data: 4 Engine OTW/IBF C 1.35 FPR, 119 610m (2000 Ft.) Field 63 Computer Sizing Data: 2 Engine OTW/IBF @ 1.35 FPR, 120 107 0m (3500 Ft.) Field 64 Computer Sizing Data: 2 Engine OTW/IBF @ 1.47 FPR, 121 910m (3000 Ft.) Field 65 Typical Computer Sizing Graphic Output (1) 126 66 Typical Computer Sizing Graphic Output (2) 127 67 Typical Computer Sizing Graphic Output (3) 128 68 Typical Computer Sizing Graphic Output (4) 129 69 Typical Computer Sizing Graphic Output (5) 130 70 OTW/IBF 1.35 FPR: Mission Fuel vs Aspect Ratio and 132 Cruise Altitude 71 OTW/IBF 1.35 FPR: DOC @ 11.5€/Gal. vs Aspect Ratio 133 and Cruise Altitude 72 OTW/IBF 1.35 FPR: DOC C 23€/Gal. vs Aspect Ratio 134 and Cruise Altitude 73 OTW/IBF 1.35 FPR: DOC @ 46€/Gal. vs Aspect Ratio 135 and Cruise Altitude 74 OTW/IBF 1.35 FPR: DOC @ $1.15/Gal. vs Aspect Ratio 136 and Cruise Altitude xii LIST OF FIGURES (Continued) Figure Title Page 75 1.35 FPR OTW/IBF: Mission Fuel vs Design Cruise Mach No. 138 76 1.35 FPR OTW/IBF: DOC C 23€/Gal. vs Design Cruise 139 Mach No. 77 1.35 FPR OTW/IBF: Effect of Fuel Price on Optimum 141 Design Cruise Speed 78 1.35 FPR OTW/IBF: Effect of Fuel Price on Optimum 142 Design Cruise Altitude 79 Effect of Fuel Price on Aspect Ratio Optimization 143 80 Wing Loading for Minimum DOC vs Fuel Cost 143 81 Sensitivity to Compressibility Drag, 1.35 FPR OTW/IBF 144 82 Sensitivity to Airfoil Technology, 1.35 FPR OTW/IBF 145 83 Sensitivity to Sweep Angle, 1.35 FPR OTW/IBF 146 84 Sensitivity of Direct Operating Cost to Weight Saving and 147 Cost Increase 85 1.25 FPR OTW/IBF: Mission Fuel on Cruise Altitude (4-Engines) 149 86 1.25 FPR OTW/IBF: DOC-1 vs Cruise Altitude (4-Engines) 151 87 1.25 FPR OTW/IB F: DOC-2 vs Cruise Altitude (4-Engines) 152 88 1.25 FPR OTW/IBF: DOC-4 vs Cruise Altitude (4-Engines) 153 89 1.25 FPR OTW/IBF: Mission Fuel vs Cruise Mach No. (4-Engines) 154 90 1.25 FPR OTW/IBF: DOC-1 vs Cruise Mach No. 155 91 1.25 FPR OTW/IBF: DOC-2 vs Cruise Mach No. (4-Engines) 157 92 1.25 FPR OTW/IBF: DOC-4 vs Cruise Mach No. (4-Engines) 158 93 1.47 FPR OTW/IBF: Wing Loading vs Field Length and 161 Cruise Speed 94 1.47 FPR OTW/IBF: Mission Fuel vs Mach No: 162 95 1.47 FPR OTW/IBF: DOC-2 vs Mach No. 163 96 Generalized T/W Required by Takeoff: 1.35 FPR OTW/IBF 166 @ 910m (3000 Ft.) Field 97 Takeoff Operational Envelope: 1.35 FPR OT W/IBF @ 167 910m (3000 Ft.) Field xiii LIST OF FIGURES (Continued) Figure Title Page VOLUME II 147 AW - Independent Duct System (2 Engines) 252 148 AW - Independent Duct System (4 Engines) 252 149 Augmentor Wing Ducting Arrangements 254 150 AW Engine Comparisons 257 151 PD287-51 (Scaled) Engine Terminal Area Operation 263 152 Typical AW Power Plant Installation 265 153 Initial 2-Engine Vehicle Selection 274 154 Initial 4-Engine Vehicle Selection 275 155 Comparison of Two and Four Engine AW Aircraft 277 156 Optimum Augmentor/BLC Thrust Split (2 -Engine) 278 157 Optimum Augmentor/BLC Thrust Split (4-Engine) 279 158 Propulsive Lift Installation Losses 282 159 Reference AW Duct System Losses 283 160 2-Engine Augmentor Wing: Optimum Fan Pressure Recovery 285 161 4-Engine Augmentor Wing: Optimum Fan Pressure Recovery 286 162 AW: DOC vs T/S 287 163 Sensitivity to T/S Limits 288 164 AW - Ducting (2 Engine Configuration) 291 165 AW - Alternate Ducting (2 Engine Configuration) 291 166 Schematic of Alternate 2-Engine Ducting 293 167 AW - Ducting (4 Engine Configuration) 295 168 AW - Matching of Planform and Duct Area 295 169 AW - Distribution of Fan Pressure Losses 297 170 AW - Cruise Blowing Ducting (4 Engine) 297 171 AW - Comparison of Valved and Cruise Blowing Systems 299 172 Thrust/Weight vs Takeoff Wing Loading (Augmentor Wing) 301 xvi LIST OF FIGURES (Continued) Figure Title Page 173 AW - DOC vs Aspect Ratio and Sweep (Initial) 302 174 Relative DOC and Mission Fuel vs Aspect Ratio 304 175 AW: T/W and Ramp Weight vs W/S (2 Engines) 305 176 AW: DOC and Mission Fuel vs W/S (2 Engines) 306 177 AW General Arrangement (2 -Engine, FPR 3.0) 307 178 T/W and Ramp Weight vs W/S (4 Engines) 308 179 DOC and Mission Fuel on W/S (4 Engines) 309 180 AW General Arrangement (4-Engine, FPR 3.0) 310 181 Orthodox AW: Gross Weight and Mission Fuel vs Aspect Ratio 315 182 Orthodox AW: DOC- 1 and DOC-2 vs Aspect Ratio 316 183 Orthodox AW: DOC-4 and DOC-10 vs Aspect Ratio 317 184 Orthodox AW: Gross Weight and Mission Fuel vs Cruise Altitude 319 185 Orthodox AW: DOC-1 and DOC-2 vs Cruise Altitude 320 186 Orthodox AW: DOC-4 and DOC-10 vs Cruise Altitude 321 187 Orthodox AW: Gross Weight and Mission Fuel vs Cruise Speed 322 188 Orthodox AW: DOC-1 and DOC-2 vs Cruise Speed 323 189 Orthodox AW: DOC-4 and DOC-10 vs Cruise Speed 324 190 Orthodox AW General Arrangement (FPR 3.2) 327 191 Load-Compressor AW: T/W vs W/S and Thrust Split (AR = 14) 328 192 Load-Compressor AW: T/W vs W/S and Thrust Split (AR = 10) 329 193 Load-Compressor AW: Gross Weight and Mission Fuel vs. 330 Cruise Altitude 194 Load-Compressor AW: DOC-1 and DOC-2 vs Cruise Altitude 331 195 Load-Compressor AW: DOC-4 and DOC-10 vs Cruise Altitude 332 196 Load-Compressor AW: General Arrangement 337 197 DOC Comparison: Augmentor Wing vs OTW/IBF 338 198 Mission Fuel Comparison: Augmentor Wing vs OTW/IBF 339 199 AW Noise Footprint Contours (FPR 3.0) 342 xvii LIST OF FIGURES (Continued) Figure Title Page 200 Mechanical Flap Nacelles 348 201 Estimated Mechanical Flap Nacelle Dimensions 349 202 MF - Lift and Drag Characteristics of Various Mechanical 353 Flap Systems 203 MF - Comparison of CL MAX for Various Mechanical Flaps 354 204 MF - FAR Landing Field Length Comparison 355 205 MF - Approach Speed Comparison 355 206 2-Engine MF, 1.35 FPR Sizing Data 357 207 3-Engine MF, 1.35 FPR Sizing Data 358 208 4-Engine MF, 1.35 FPR Sizing Data 359 209 2-Engine MF, 1.574 FPR Sizing Data 360 210 3-Engine MF, 1.574 FPR Sizing Data 361 211 4-Engine MF, 1.574 FPR Sizing Data 362 212 Direct Operating Cost vs Number of Engines (MF) 364 213 Engine Cost Basis . 366 214 MF: T/W Required for Takeoff and Landing vs W/S and AR 369 215 MF: T/W Required to Meet Approach Climb Gradient Requirement 370 216 MF: T/W Required vs Climb Speed 370 217 MF: T/W and DOC vs W/S (FPR 1.35) 371 218 MF: T/W and DOC vs W/S (FPR 1.574) 372 219 MF: DOC vs Aspect Ratio and Sweep (Initial) 374 220 MF: DOC vs Aspect Ratio and Sweep (Updated) 374 221 Ramp Gross Weight vs Aspect Ratio and Sweep 375 222 926 Km (500 N.Mi.) Mission Fuel vs Aspect Ratio and Sweep 375 223 MF - General Arrangement, FPR 1.574 379 224 MF - General Arrangement, FPR 1.35 380 225 MF - Aircraft Weights and Thrust vs FPR 381 226 MF - DOC, Airframe and Engine Cost vs FPR 382 xviii LIST OF FIGURES (Continued) Figure Item Page 277 T-56 MF: DOC-2 vs Mach No. 469 278 Fuel and Cost Effects of Design Cruise Speed (OTW/IBF) 475 279 DOC-2 vs Cruise Mach No. (OTW/IBF) 475 280 Fuel and Cost Effects of Engines and Speed (OTW/IBF) 477 281 Effect of Fuel Cost on Optimum Fan Pressure Ratio (OTW/IBF) 479 282 Fuel and Cost Effects of Engines and Design Cruise Speed (MF) 480 283 Effect of Fuel Price on Optimum Fan Pressure Ratio: 482 1220m (4000 Ft.) MF 284 Effect of Fuel Price on Optimum Fan Pressure Ratio: 483 182 0m (6000 Ft.) MF 285 Effect of Field Length on Mission Fuel 485 286 Effect of Field Length on DOC 485 287 Comparison of Concepts - Minimum DOC-2 Cases 488 288 Effects of Installation on SFC 501 289 SFC (Pylon Thrust) vs FPR 501 290 DOC vs Range (R/STOL Aircraft) @ 2555 Hours Utilization 507 291 DOC vs Range (Twin CTOL) C 3285 Hours Utilization 507 292 DOC vs Range (727-200) @ 3285 Hours Utilization 507 293 DOC vs Utilization and Fuel Price 510 294 DOC vs Range (R/STOL Aircraft) @ 3285 Hours Utilization 510 295 DOC vs RO 1I 512 296 Potential High Performance USB System 519 APPENDICES A-1 OTW/IBF Computer Sizing Data: Noise Analysis Vehicles (1) 530 A-2 OTW/IBF Computer Sizing Data: Noise Analysis Vehicles (2) 531 A-3 OTW/IBF Computer Sizing Data: Noise Analysis Vehicles (3) 532 xxi LIST OF FIGURES (Continued) Figure Item Page A-4 OTW/IBF Computer Sizing Data: Noise Analysis Vehicles (4) 533 A-5 OTW/IBF Computer Sizing Data: Noise Analysis Vehicles (5) 534 A-6 OTW/IBF Computer Sizing Data: Noise Analysis Vehicles (6) 535 B-1 MF Computer Sizing Data: Noise Analysis Vehicles (1) 538 B-2 MF Computer Sizing Data: Noise Analysis Vehicles (2) 539 B-3 MF Computer Sizing Data: Noise Analysis Vehicles (3) 540 B-4 MF Computer Sizing Data: Noise Analysis Vehicles (4) 541 B-5 MF Computer Sizing Data: Noise Analysis Vehicles (5) 542 B-6 MF Computer Sizing Data: Noise Analysis Vehicles (6) 543 B-7 MF Computer Sizing Data: Noise Analysis Vehicles (7) 544 xxii LIST OF TABLES Table Title Page SUMMARY 0.1 Engine Selection for Concept Comparison at Equivalent Noise xxxiv Levels 0.11 OTW/IBF Baseline Aircraft Characteristics xxxvi 0.111 Fuel-Conservative Airplane Characteristics - 1.35 FPR OTW/ xxxix IBF - 910M (3000 feet) FL 0. IV AW Airplane Characteristics xliii 0.V MF Baseline Airplane Characteristics xlvi 0.VI Airplane Characteristics - 1.35 FPR MF 910M (3000 feet) FL xlix 0.VII Airplane Characteristics - 1.35 FPR MF 1220M (4000 feet) FL xlix 0.VIll T-56 and Quiet Propeller - 910M (3000 feet) liii 0.IX DOC and Fuel Penalties - No Performance Constraints liv 0.X DOC and Fuel Penalties at Field Length 1220M (4000 feet) or Ivi Less 0.XI DOC and Fuel Penalties at Field Length 910M (3000 feet) or Ivii Less - MO.75 0.XII Summary of 610 and 910M (2000 and 3000 feet) Aircraft lix VOLUME I OTW/IBF Engine Candidates 37 xxiii Table Title Page XXXIX Turboprop Technology Derivatives 463 XL T-56 Sensitivities 471 XLI Airplane Characteristics 1.35 FPR, OTW/IBF, 910M (3000 feet) FL 486 XLII Airplane Characteristics 1.35 FPR, MF, 910M (3000 feet) FL 486 XLIII T-56 and Quiet Propeller - 910M (3000 feet) FL 489 XLIV Airplane Characteristics 1.35 FPR, MF, 1220M (4000 feet) FL 490 XLV Summary of Fuel Consumptions 492 XLVI DOC and Fuel Penalties - No Performance Constraints 494 XLVII DOC and Fuel Penalties at Field Length 1220M (4000 feet) or Less 495 XLVIII DOC and Fuel Penalties at Field Length 910M (3000 feet) or Less - MO.75 497 XLIX Summary of 610M and 910M (2000 and 3000 feet) Aircraft (Min. DOC 2) 499 L Airplane Characteristics and Costs - OTW/IBF 910M (3000 feet) FL 504 LI Airplane Characteristics and Costs - OTW/IBF 610M (2000 feet) FL 505 LII Airplane Characteristics and Costs - MF 1220M (4000 feet) FL 506 LIll DOC Breakdown - STOL Aircraft 508 xxvi SYMBOLS AND ABBREVIATIONS AR airplane aspect ratio or nozzle aspect ratio, b/h AW augmenter wing b span BLC boundary layer control BPR bypass ratio, engine secondary airflow/engine primary airflow CD drag coefficient CL lift coefficient CP pressure coefficient CR roll moment coefficient CT thrust coeffic lient CX axial force coefficient C blowing moment coefficient c chord ¢/ASSM cents/available seat statute mile CTOL conventional takeoff and landing D diameter dB decibel DOC direct operating cost DOC-1 DOC at 11.5C/gallon of fuel DOC-2 DOC at 2 3 C/gallon of fuel DOC-3 DOC at 46 /gallon of fuel DOC-4 DOC at 1.15C/gallon of fuel EBF externally blown flap EPNdB equivalent perceived noise decibel F engine thrust xxvii f frequency (Hertz) FAR Federal Aviation Requirements FPR fan pressure ratio g gravitational constant H nozzle height Hz Hertz, unit of frequency IBF internally blown flap LE leading edge M Mach number or Meter m airflow or meter MF mechanical flap NPR nozzle pressure ratio OASPL overall sound pressure level OPR overall pressure ratio of engine OTW over-the-w ing OTW/IBF over-the-wing/internally blown flap hybrid OWE operating weight empty PNdB unit of perceived noise level .PNL perceived noise level q dynamic pressure R coanda radius RGW ramp gross weight RN Reynolds number RO1 return on investment R/STOL reduced/short takeoff and landing xxvi I * REFINE DESIGN OF SHORT-HAUL AIRCRAFT -- M 0.8, 9 140m. (30,000 FT.) 610m. 910m. 1070m. 1220m. FIELD LENGTH (2000 FT.) (3000 FT.) (3500 FT.) (4000 FT.) OVER THE WING/INTERNALLY BLOWN FLAP o 0 *-PARAMETRIC DESIGN MECHANICAL FLAP o AUGMENTOR WING o Q*-PRELIMINARY DESIGN * REOPTIMIZE ABOVE AIRCRAFT (WING AR, CRUISE SPEED AND ALTITUDE) FOR MINIMUM FUEL AND HIGHER FUEL COSTS REEXAMINE EXTERNALLY BLOWN FLAP ADD DEFLECTED SLIPSTREAM WITH TURBOPROP ENGINES EXTEND MECHANICAL FLAP ANALYSES TO COVER 1830m. AND 2 440m. (6000 AND 8000 FT.) EVALUATE ENGINES WITH FPR 1.25, 1.35, 1.47 * DETERMINE FUEL AND DOC PENALTY FOR POTENTIAL NOISE CRITERIA: 95 EPNdB AT 150m. (500 FT.) SIDELINE PART 36 MINUS 5, 10, 15 EPNdB SPERRY BOX LEVEL OF 80 EPNdB 90 EPNdB FOOTPRINT AREA LIMITED TO 2.59, 1.39, 0.78 km 2 (1.0, 0.5, 0.3 SQ. MI.) 90 EPNdB FOOTPRINT LENGTH LIMITED TO 6.5, 3.7, 1.9, 1.2 km (3.5, 2.0, 1.0 N. MI., 4000 FT.) FIGURE 0.1: STUDY APPROACH 148 PASSENGERS 0.8 MACH 910 M (3000 FT) FIELD LENGTH -[ o..c....ot 0.000-9905e 60810*o..8O80 SPAN = 35.56 M (116.66') LENGTH = 42.57 M (139.66') HEIGHT = 11.78 M (38.66') FIGURE 0.2: 910 M (3000 FT) OTW-IBF VEHICLE xxxii configurations, providing a greater wing thickness for a given drag rise, sweep angle, and design cruise speed. In all cases, emphasis was given to designs meeting noise levels equivalent to 95-100 EPNdB at 153 m. (500 ft.) sideline. The range of fan pressure ratios for engines used in the designs was chosen to cover a range of noise levels from slightly below 95 to considerably higher than 100 EPNdB at this sideline location. Effects of this variation are summarized later. The concepts were compared at approximately the same low noise level by utilizing the enginefan pressure ratios and noise treatment listed in Table 0.1. The following discussion is organized to cover, first, the design refinement of the hybrid OTW/IBF concept and changes associated with minimizing fuel consumption or minimizing operating cost at higher fuel prices. Next, the augmentor wing and mechanical flap concepts are covered. The other lift concepts are examined more briefly from the standpoint of fuel conservation. The concepts are then compared, noise aspects are summarized, and conclusions and recommendations are listed. Hybrid OTW/IBF Aircraft The hybrid OTWABF airplane is characterized by location of the engines over the wing and use of Coanda attachment for thrust vectoring, combined with ducting of a small proportion of the fan air to trailing edge flaps for low speed lift augmentation. Cross- ducting of the fan air in the IBF system makes it possible to achieve lift symmetry in a two, three, or four engine configuration. The baseline airplane resulting from design refinement, and optimized for minimum direct operating cost at 1972 fuel prices, is shown in Figure 0.2. Detailed analysis covered the following areas: o Nacelle inlet, exhaust and thrust reverser design; Coanda jet deflection. o Mass flow split, ducting, and flap configuration. o Limits on engine size related to wing area, expressed as thrust/ wing area (T/S) limit. o Aerodynamic performance and comparison of data from Lockheed and other wind tunnel tests. o Weights of flap, ducting, wing box and other components. xxxiii TABLE 0.1 ENGINE SELECTION FOR CONCEPT COMPARISON AT EQUIVALENT NOISE LEVELS Lift Concept Engine FPR Acoustic Treatment Hybrid OTW/IBF 1.35 Nacelle Wall only Augmentor Wing 3.0 - 3.2 High Mach Inlet; Exhaust Duct Wall; Flap Cavity Mechanical Flap 1.35 Nacelle Wall only Externally Blown Flap 1.25 Nacelle Wall only Over-the-Wing 1.35 Nacelle Wall only Boundary Layer Control/ 1.3 Nacelle Wall only Vectored Thrust Internally Blown Flap/ 1.3 Nacelle Wall only Vectored Thrust Deflected Slipstream (Turboprop) Nacelle Wall and Low Tip-Speed Prop xxxiv 0o o o 910 M (3000 FT) OTW/IBF WITH 1.35 FPR ENGINES 14 DOC-2 6 / .0 4 ENGINES 2-ENGINES-/ 2 ENGINES 12 _ " , 1.9 :D MIN FUEL Z 5 4 ENGINES MIN DOC 0 VMIN DOC-1 1.8 S.u DOC-1 MIN DO-2 O 4 ENGINES MIMIN FUEL 2 ENGINES 4 FUEL MIN DOC , 8 01.6 0.6 0.7 0.8 0.6 0.7 0.8 DESIGN CRUISE MACH NO. DESIGN CRUISE MACH NO. FIGURE 0.3: EFFECT OF DESIGN CRUISE SPEED ---- - 2-ENGINES 4.0 4-ENGINES / - DOC-10' 3.6 3.2 OPTIMUM DESIGN CRUISE DOC - C/ASSM MACH: 4 ENGINES S ESTIMATED 2.8 OPTIMUM DESIGN CRUISE MACH: 2-ENGINES 2.4 DOC-4 2.0 DOC-2 DOC-11.6 1I I I I-r 0.54 0.56 0.60 0.64 0.68 0.72 0.76 0.80 DESIGN CRUISE MACH NUMBER FIGURE 0,4: 1.35 FPR OTW/IBF: EFFECT OF FUEL PRICE ON OPTIMUM DESIGN CRUISE SPEED 910M (3000 FT.) FIELD LENGTH xxxvii airplane has a DOC-2 1.3% lower than the 2-engined configuration. If the airplane had been optimized for minimum mission fuel, the figure shows a 4- engined, 0.6 M design requires only 4080 Kg (9,000 lb.), a saving of 31% relative to the original DOC-1 design. However, thissaving is associated with a 8 % increase in DOC-1 to 1.75€/ASSM, while at DOC-2 the penalty is 2.6%. While this config- uration provides an excellent reduction in mission fuel, it is doubtful that it would be accepted because of the increase in DOC and the large reduction in cruise speed. If the airplane is optimized for DOC at the increased fuel price, a 4-engined, 0.73 M configuration provides a DOC-2, 4% lower than the original optimized design and re- quires 27% less fuel for the mission. Thus, it can be seen that by optimizing for mini- mum DOC at the increased fuel price, fuel savings close to the design optimized for minimum fuel can be achieved while still minimizing operating costs. Figure 0.4 presents DOC at various fuel price levels plotted against design cruise Mach number for 2- and 4-engined designs which use optimum aspect ratios and cruise alti- tudes. The buckets in the curves determine the design cruise Mach number for minimum DOC at each fuel price, which when connected together form the lines of optimized cruise speed. Note that optimum cruise speed reduces with increase in fuel price as would be expected. The effect of engine fan pressure ratio on DOC at various fuel price levels is illustrated in Figure 0.5 for airplanes having optimum cruise speed, altitude and aspect ratio. These data were developed for the OTW/IBF, 3,000 ft. concept designed with each of the three engine cycles. It can be seen that DOC-1 is achieved with 1.47 FPR at 0.8 M while minimum DOC-10 is achieved with 1.32 FPR and 0.68 M. An excellent choice for fuel prices ranging from DOC-2 through DOC-10 is 1.35 FPR since it pro- vides DOC's close to minimum in all cases. The optimum aspect ratio varied for different fuel prices; airplanes optimized for min- imum fuel require aspect ratios of the order of 14, while airplanes optimized for DOC- 2 require aspect ratios of the order of 10-12, compared to 7-8 for minimum DOC-1. Table 0.III summarizes the design characteristics of the OTW/IBF configurations xxxviii 3.0 OC-10 0.68M RELATIVE DOC 2.0 OPTMUM \ FAN PRESSURE \RATIO -,,2 73M D ---... 0.8M 1.25 1.35 1.45 FAN PRESSURE RATIO FIGURE 0.5: EFFECT OF FUEL PRICE ON OPTIMUM FAN PRESSURE RATIO - OTW/IBF CONCEPT, 910 M (3000 FT) FL. 1.32 FPR OPTIMIZED FOR V.P. MIN. DOC-1 DOC-1 DOC-2 DOC-4 DOC-10 FUEL REF. 2 MACH NO. 0.8 0.8 0.75 0.70 0.70 0.60 NO. OF ENGINES 2 2 4 4 4 4 OWE - KG 44,570 43,450 36,510 35,290 35,290 34,870 (LB) (98, 250) (95, 790) (80,490) (77,800) (77,800) (76, 880) GROSS WEIGHT - KG 66,840 65,550 56,450 54,670 54,670 53,910 (LB) (147,350) (144,520) (124,440) (120,520) (120,540) (118,860) RATED THRUST - KN 163.7 167.5 55.3 48.0 48.0 44.1 (LB) (36,810) (37,660) (12,440) (10,790) (10,790) (9,910) MISSION FUEL - KG 6,330 6,030 4,400 4,210 4,210 4,070 (LB) (13,960) (13,300) (9,700) (9,290) (9,290) (8,975) AR 7.0 7.73 12 14 14 14 *DOC-1 -- /ASSM. J 1.7971 1.616 1.634 1.646 1.646 1.747 DOC-2 -- ¢/ASSM. - 1.889 1.831 1.837 1.837 1.937 DOC-4 -- ¢/ASSM. 2.437 2.246 1 2.221 2.221 2.307 DOC-10 - /ASSM. - 4.08 3.441 3.373 3.373 3.422 W/S T.O - KG/SQ. M. 455 449 554 530 530 457 (LB/SQ. FT) (93.2) (92.0) (113.5) (108.5) (108.5) (93.5) 90 EPNdB T.O. AREA 1.30 1.19 1.53 1.45 1.45 1.40 SQ. KM (SQ. MI) (0.5) (0.46) (0.59) , (0.56) (0.56) , (0.54) * ENGINE PRODUCTION QUANTITY: 750 IN REF. 2 IDENTICAL AIRPLANE 1500 IN PRESENT PHASE TABLE 0.111: FUEL CONSERVATIVE AIRPLANE CHARACTERISTICS 1.35 FPR OTW/IBF, 910 M (3000 FT) F.L. xxxix column; in this concept the 4 -engine configuration is superior because of the following factors: 0 The wing loading for the 2-engine airplane is restricted to a lower value because duct volume requirements necessitate a larger wing. o Lower flap deflections associated with second-segment climb pro- vide lower augmentation ratios for the 2 -engine airplane defined in Table 0.IV. This factor might be overcome by designing to fully deploy the augmentor at very small flap deflections. The associated reduction in thrust requirement would improve DOC-1 to approximately 1.97€/ASSM. and the ramp gross weight would be reduced to 82,000 kg (180,000 lb.). o Engine pricing for the 2 -engine configuration was based on a pro- duction quantity of 750 engines; if the pricing were based on 1500 engines (300 aircraft plus 25 percent spares in a 4 -engine design), the DOC would be reduced further to 1.89€/ASSM. However, it must be noted that the FPR 3.0 engine cannot be used for other powered lift or CTOL applications; the original engine pricing based on a fixed number of STOL aircraft sets is more realistic. The 4 -engine airplane optimized for DOC-1 is illustrated in Figure 0.7. The config- uration features engines placed on the upper surface of the wing in order to maximize available volume for ducts by locating engines as far as possible inboard; the upper surface location permits a more inboard location for the same degree of interference drag. The wing planform has a constant chord section extending to the outboard engine for the purpose of maximizing at a given wing area the chord (and duct volume) at this location. The columnsheaded DOC-2 in Table 0.IV reflect the characteristics of aircraft with further design refinement for reducing fuel consumption and minimizing DOC-2. The first airplane uses four engines with 3.2 FPR and improved SFC in a configuration similar to that shown in Figure 0.7. Reduction in mission fuel is significant compared to the xlii 910 M (3000 FT) FIELD LENGTH OPTIMIZED FOR REF. 2 MIN. DOC-1 DOC-1 DOC-2 FUEL NO. OF ENGINES 4 4 2 4 2 + 2 2 + 2 FPR 3.0 3.0 3.0 3.2 1.35 (3.0) 1.35 (3.0) MACH NO. 0.8 0.8 0.8 0.75 0.75 0.75 CRUISE ALT. - M 9, 140 9,140 9, 140 7,620 9, 140 9, 140 (FT) (30,000) (30, 000) (30,000) (30,000) (30,000) (30,000) AR 6.5 6.0 5.0 8.5 10.0 14.0 SWEEP - DEG. 30 20 20 10 10 10 W/S T.O. - KG/SQ.M 473 512 369 491 547 503 (LB/SQ. FT) (96.9) (105.0) (75.5) (100.5) (112.0) (103.0) T/W T.O. 0.324 .347 .444 .305 .29 (.41) .28 (.39) RGW - KG 72,350 69,900 92,910 63,460 65,030 69,070 (LB) (159,503) (154,100) (204,830) (139,900) (143,370 (152,280) OWE - KG 47,530 45,260 63,570 40,890 44,810 49,490 (LB) (104,779) (99,790) (140, 150) (90, 150) (98,790) (109, 100) MISSION FUEL - KG 8,408 8,256 11,706 6,559 7,049 5,583 (LB) (18,537) (18,200) (25,806) (14,460) (12,540) (12,309) DOC-1 - ¢/ASSM 1.90 1.88 2.164 DOC-2 - ¢/ASSM - - - 2.11 2.015 2.079 90 EPNdB T.O. AREA - SQ. K - 1.30 - < 1.30 -1.30 - (SQ. MI.) - (0.5) - (<0.5) ('0.5) - TABLE 0.1V AW - AIRPLANE CHARACTERISTICS xlii; 148 PAX 0.8 M 910 M (3000 FT) FIELD LENGTH SPAN = 28.9 M (94.7') LENGTH =42.4 M (139') HEIGHT =11.7 M (38.5') - cOaOOcOOO,,,Cooo,,, On oo oooooo o FIGURE 0.7: 910 M (3000 FT) AW VEHICLE - DOC-1 - -~ 148 PASSENGERS 0.8 MACH 910M (3000 FT) FIELD LENGTH SPAN = 41.35M (135.66') LENGTH = 43.18M (141.66') HEIGHT = 14.22M (46.66') FIGURE 0.8: MF - GENERAL ARRANGEMENT, FPR 1.35 xliv 0 -.J S o MINIMUM FUEL CASES MINIMUM DOC CASES 8 --- 4 ENGINE /4 ENGINE 12 ---- 2ENGINE 2.1- ---- 2ENGINE 5.0- 11 2.0 -91O0 4.5 10 1.9 Z QC-2DOC-2 o - /ASSM 9^ - 1.8 1220M r 4.0 4000 FT 8 1.7 1220M 3.5 4000 FT , 1830M 7 1.6 6000 FT 3.0 - 0.5 0.6 0.7 0.8 0.5 0.6 0.7 0.8 DESIGN CRUISE MACH NO. DESIGN CRUISE MACH NO. FIGURE 0,9: EFFECT OF DESIGN CRUISE SPEED - MF WITH 1.35 FPR ENGINES 2.2 2.0 OPTIMUM DESIGN CRUISE OPTIMUM DESIGN CRUISE DOC - 4 ENGINES 2 ENGINES /ASSM 1.8 - \ DOC-2 1.6- 4 ENGINES DOC-1 ----- 2 ENGINES 1.4 I-- I l 0.55 0.60 0.65 0.70 0.75 0.80 DESIGN CRUISE MACH NUMBER FIGURE 0. 10: EFFECT OF FUEL PRICE ON OPTIMUM DESIGN CRUISE SPEED: 1220 M (4000 FT) FIELD LENGTH MF xlvii Effect of other fuel prices on design speed for minimum DOC is reflected in Figure 0.10 for the 1220 m. (4000 ft.) MF airplane. Although the four-engine airplanes require less fuel, the two-engine airplanes provide minimum DOC at fuel prices up to those repre- sented by DOC-4. Tables 0.VI and 0.VII summarize the characteristics of MF configurations designed for 910 m. (3000 ft.) and 1220 m. (4000 ft.) with 148 passengers and 926 Km (500 n.m.) range. The study airplanes defined in reference 2 are also tabulated. A significant improvement is shown in the present study, primarily due to the improved installed engine performance achieved by elimination of acoustic splitters in the nacelles. The airplane designed for 1220 m. (4000 ft.) field performance and optimized for minimum DOC-2 is shown in Figure 0.11. Other Concepts Evaluated for Fuel Conservation The study completed in 1973, "Study of Quiet Turbofan STOL Aircraft for Short Haul Transportation" (reference 2) included evaluation of externally blown flap, over the wing, boundary layer control, and internally blown flap lift concepts. These have been reexamined in the present study in the light of fuel conservation and increased fuel prices. The externally blown flap airplane with 1.25 FPR engines has a design cruise speed of 0.65 M for minimum DOC-2. It is a four-engine configuration with aspect ratio 10. Fuel consumption and DOC-2 are shown in Figure 0.12, along with other lift concepts. Although its fuel is acceptably low, the DOC-2 is high, principally because of the low cruise speed and low fan pressure ratio engine which is required for comparable noise levels. The over-the-wing concept is closely comparable to the four-engine hybrid OTW/IBF except, of course, the IBF component is deleted and the flap would be modified for Coanda turning aft of the nacelle, and slotted elsewhere. At higher fuel prices, the economic advantage of two engines in the hybrid OTW/IBF is lost so the four-engine OTW must be regarded as a competitive concept. Boundary layer control and internally blown flap concepts both require vectoring of the fan air to achieve the required approach glide slopes. Under-wing installations with xlviii OPTIMIZED FOR REF. 2 MIN DOC-1 DOC-1 DOC-2 DOC-4 DOC-10 FUEL MACH NO. 0.8 0.8 0.75 0.70 0.70 0.60 0.55 NO. OF ENGINES 2 2 2 2 2 4 4 OWE - KG 52,590 46,870 41,760 40,020 40,020 38,270 35,290 (LB) (115,940) (103,330) (92,060) (88,230) (88,230) (84,380) (77,800 GROSS WEIGHT - KG 76,610 69,000 62,690 60,210 60,210 57,700 54,200 (LB) (168,890) (152,110) (138,200) 32,740) (132,740)(127,210) (119,480 RATED THRUST - KN 195.5 151.6 125.3 . 118.4 118.4 43.4 38.5 (LB) (43,950) (34,070) (28,160) 26,610) (26,610) (9,760) (8,660 MISSION FUEL - KG 7,550 6, 110 5,440 4,870 4,870 4,200 3 (LB) (16,640) (13,460) (12,000) (10,730) (10,730) (9,250) (8,770 AR 7.0 7.0 7.0 7-10 7-10 10 14 *DOC-1 -- ¢/ASSM. 1.93111 1.632 1 1.582| 1.597 1.597 1.75 1.828 DOC-2 -- /ASSM. 1.912 1.832 1.818 1.818 1.94 2.010 DOC-4 -- ¢/ASSM. 2.472 2.328 2.262 12.262 2.32 2.376 DOC-10 -- ¢/ASSM. 4.152 3.760 3.589 3.589 3.46 3.472 W/S T - KG/SQ.M. 302 287 287 287 287 287 287 T.O. (LB/SQ. FT) (61.8) (58.8) (58.8) (58.8) (58.8) (58.8) (58.8) 90 EPNdB T.O. AREA 1.04 1.48 1.40 1.37 1.37 1.09 1.06 SQ. KM (SQ. MI) (0.4) (0.57) (0.54) (0.53) (0.53) (0.42) (0.41) IDENTICAL AIRPLANE * ENGINE PRODUCTION QUANTITY: 750 IN REF. 2 1500 IN PRESENT PHASE TABLE 0.VI: AIRPLANE CHARACTERISTICS 1.35 FPR. MF 910 M (3000 FT) F.L. OPTIMIZED FOR REF. 2 MIN. DOC-1 DOC-1 DOC-2 DOC-4 DOC-10 FUEL MACH NO. 0.8 0.8 0.75 0.70 0.65 0.60 NO. OF ENGINES 2 2 2 2 4 4 OWE - KG 40,510 39,140 36,770 35,790 33,800 33,920 (LB) (89,300) (86,280) (81,060) (78,900) (74,520) (74,770) GROSS WEIGHT - KG 62,120 59,400 56,460 55,340 52,590 52,530 (LB) (136,950) (130,950) (124,480) (122,000) (115,950) (115,800) RATED THRUST - KN 150.3 114.3 111.0 104.8 40.9 38.0 (LB) (33,800) (25,690) (24,950) (23,560) (9,190) (8,550) MISSION FUEL - KG 5,865 4,717 4,382 4,218 3,801 15 (LB) (12,930) (10,400) (9,660) (9,300) (8,380) (8,190) AR 7.0 10.0 10.0 10.0 14.0 14 *DOC-1 -- ¢/ASSM. 1.681l 1.446 1.45 1.466 1.626 1.70 DOC-2 -- ¢/ASSM. 1.67 J 1.648 1.659 1.798 1.87 DOC-4 -- ¢/ASSM. 2.10 2.05 2.044 2.142 2.21 DOC-10 -- ¢/ASSM. 3.408 3.25 3.20 J73.174 j 3.23 W/S - KG/SO.M. 455 391 393 379 40 361 T.O. (LB/SQ. FT) (93.1) (80.0) (80.5) (77.6) (82.5) (74.0) 90 EPNdB T.O. AREA 0.97 1.42 1.37 1.32 1.088 N/A SQ. KM (SQ. MI) (0.375) (0.55) (0.53) (0.51) (0.42) * ENGINE PRODUCTION QUANTITY: 750 IN REF. 2 1500 IN PRESENT PHASE TABLE 0.VII: AIRPLANE CHARACTERISTICS 1.35 .FPR. MF. 1220 M (4000 FT) F L. xlix Pegasus-type nozzles showed inferior cruise performance, DOC and fuel consumption compared to other concepts. Aircraft were designed with rubberized T-56 turboprop engines and with conventional and low-tip-speed propellers. Stall speed margins were based on power-on conditions, pro- viding allowable wing loadings higher than those based on power-off as required by FAR Part 25. The quiet propeller aircraft had better fuel consumption and DOC due to the higher low-speed thrust permitting higher wing loadings for a given field performance. Cruise speeds were Mach 0.5 to Mach 0.6. Fuel and DOC-2 are shown as a function of field length in Figure 0.12. Characteristics of aircraft designed for 910 m. (3000 ft.) field performance with different fuel price levels are shown in Table 0.VIII. If the T-56 turboprop deflected slipstream concept were acceptable from considerations of passenger appeal and cruise speed, it would be the best choice for field lengths up to 1525 m. (5000 ft.). It is suggested that this application is most suitable in the low to medium density short haul market, particularly at stage lengths below 700 Km (380 n.m.). It is not likely to compete successfully for passengers in competition with higher-speed fan-powered aircraft in high-density routes such as Chicago-New York. Since the present study is primarily concerned with the latter high-density arena, the turboprop deflected slipstream aircraft have been included only as a reference in the comparisons that follow. Evaluation of Aircraft Configurations Noise analyses and tradeoffs were conducted to determine the economic penalty associated with the various potential noise requirements, such as FAR 36, less than FAR 36, 95 EPNdB at the 500 ft. sideline, 80 EPNdB at Sperry Box, and footprint area and length for various noise level contours. The analyses were arranged to indicate the effect of concepts, fan pressure ratio, field length and fuel price variations on the various noise level measuring parameters. Table 0.IX summarizes the effect of noise constraints on airplane configuration, DOC-2, and fuel consumption with no restriction on the performance factors. With cruise speed and block time unrestricted, the two-engine mechanical flap aircraft with 1830 m. (6000 ft.) field length and FPR 1.35 engines satisfies many noise restrictions with no lii OPTIMIZED FOR MIN. DOC-1 DOC-2 DOC-4 DOC-10 FUEL MACH NO. 0.60 0.55 0.55 0.50 0.50 NO. OF ENGINES 4 4 4 4 4 OWE - KG 35,690 34,805 34,805 34,360 34,360 (LB) (78,680) (76,730) (76,730) (75,750) (75,750) GROSS WEIGHT - KG 54,440 53,170 53,170 52,720 52,720 (LB) (120,028) (117,223) (117,223) (116,232) (116,232) MISSION FUEL - KG 3,656 3,293 3,292 3,148 3,148 (LB) (8,060) (7,260) (7,260) (6,940) (6,940) AR 14 14 14 14 14 DOC-1 -- ¢/ASSM. r 1.473 1.477 1.477 1.500 1.500 DOC-2 -- ¢/ASSM. 1.642 1.629 1.629 1.643 1.643 DOC-4 -- /ASSM. 1.977 1.935 1.935 1.935 1.935 DOC-10-- ¢/ASSM. 2.985 2.851 2.851 2.805 2.805 W/S - KG/SQ. M. 391 387 387 371 371 T.O. (LB/SO.FT) (80.0) (79.2) (79.2) (76.0) (76.0) INST. THRUST/ENG. - KN 40.1 37.8 37.8 35.6 35.6 (LB) (9,019) (8,502) (8,502) (7,996) (7,996) CRUISE POWER % 90 80 80 70 70 90 EPNdB AREA - SQ. KM 1.30 1.30 1.30 1.30 1.30 (ESTIMATE) (SQ. MI) (0.5) (0.5) (0.5) (0.5) (0.5) IDENTICAL IDENTICAL AIRPLANE AIRPLANE TABLE 0.VIII: T-56 AND QUIET PROPELLER - 910 M (3000 FT) F.L. liii LIFT NO. FPR FIELD LENGTH CRUISE DOC-2 FUEL CONCEPT ENG. M (FT) SPEED P /ASSM KG (LB)MIN DOC-2 CASE: MIN DOC FOR FAR36-5 MF 2 1.47 1,830 (6,000) 0.75 148 -1.59 MF 2 1.35 1,830 (6,000) 0.75 148 1.599 4,199 (9,258)MIN DOC FOR FAR36-10 MF 2 1.35 1,830 (6,000) 0.75 148 1.599 4,199 (9,258)MIN DOC FOR FAR36-15 MF 2 1.35 1,220 (4,000) 0.75 148 1.641 4,318 (9,519)MIN DOC FOR 95 EPNdB C 152 M (500') MF 2 1.35 1,830 (6,000) 0.75 148 1.599 4,199 (9,258)MIN DOC FOR 80 EPNdB CSPERRY BOX SIDELINE OTW/IBF 4 1.25 910(3,000) 0.75 50 3.87 2,223 (4,900) MIN DOC FOR 80 EPNdB C SPERRY BOX FLYOVER OTW/IBF 4 1.25 610 (2,000) 0.75 5-10 7+MIN DOC-2 FOR 90 EPNdB FOOTPRINT: 2.60 SQ. KM(1 SQ.MI.) MF 2 1.35 1,830 (6,000) 0.75 148 1.599 4,199 (9,258) 1.3 SQ. KM (0.5 SQ. MI.) MF (0.526) 2 1.35 1,220(4,000) 0.75 148 1.641 4,318 (9,519).83SQ. KM (0.32 SQ. MI.) OTW/IBF (WTTERSITH 4 1.35 910 (3,000) 0.75 148 1.863 '4,790 (10,560) .75 SQ. KM(0.29 SQ. MI.) MF 4 1.25 1,220(4,000) 0.65 148 1.887 4,027 (8,877) MIN DOC-2 FOR 90 EPNdB FOOTPRINT LENGTH: 6.48 KM (3.5 N.MI.) MF 2 1.35 1,830 (6,000) 0.75 148 1.599 4,199 (9,258)3.704KM (2.0 N.MI.) MF 2 1.35 1,830 (6,000) 0.75 148 1.599 4, 199 (9,258)1.85 KM (1.0 N.MI.) OTW/IBF 2 1.35 < 910 (3,000) 0.75 148 1.90 6,350 (14,000)1220 M (4000 FT) OTW/IBF 2 1.25 610 (2,000) 0.75 148 2.3 6,804 (15,000) TABLE .IX: DOC AND FUEL PENALTIES - NO PERFORMANCE CONSTRAINTS FIELD DOC-2 FUEL NOISE LIFT NO. OF ENGINE LENGTH PENALTY PENALTY REQUIREMENT CONCEPT ENGINES FPR m. (FT.) PCTG PCTG REFERENCE MF 2 1.35 1830 0 0 (6000) FAR 36 - 10 OR 15 MF* 2 1.35 910 15 27 (3000) FAR 36 - 15 OTW/IBF 4 1.35 910 17 14 (SPLITTER) (3000) 95 EPNdB @ 152 m.(500 FT.) OTW/IBF 4 1.35 910 15 6 (3000) 90 EPNdB AREA 2.6 SQ. Km (1 SQ.MI.) MF* 2 1.40 910 14 27 (3000) - 1.3 SQ. Km (0.5 SQ.MI.) OTW/IBF 4 1.37 910 15 6 (3000) 0.83 SQ. Km (0.32 SQ.MI.) OTW/IBF 4 1.35 910 17 14 (SPLITTER) (3000) 90 EPNdB LENGTH 2.3 Km (7500 FT.) OTW/IBF 4 1.35 910 17 14 (SPLITTER) (3000) 1.86 Km (1 N.MI.) OTW/IBF 2 1.35 850 20 50 (2800) 1.22 Km (4000 FT.) OTW/IBF 2 1.25 610 40 60 (2000) * MF AT LOW WING LOADING REQUIRES RIDE QUALITY GUST ALLEVIATION AND DEMONSTRATION FOR PASSENGER ACCEPTABILITY ON LONGER STAGE LENGTHS. TABLE 0.XI DOC AND FUEL PENALTIES @' FIELD LENGTH 910 m. (3000 FT.) OR LESS -- M 0.75 Field Length % Penalties for Meeting Meters Feet FAR 36-15 1 sq . Km 90 EPNdB 90 EPNdB 2.3 Km Long DOC Fuel DOC Fuel DOC Fuel 1830 6000 3 4 10 10 17 14 1220 4000 3 4 10 10 17 14 915 3000 17 14 16 10 17 14 To meet FAR 36 minus 15, the landing field length must be reduced below 1830 m. (6000 ft.) because of approach noise. If the requirement is one sq. Km for the 90 EPNdB footprint area, the penalty is 10 percent in DOC and fuel and no additional penalty is incurred for reduction in field length to 1220 m. If the length of the 90 EPNdB footprint is required to be 2.3 Km. the 910 m. (3000 ft.) field length is re- quired and the DOC and fuel penalties are 17% and 14% respectively. Table 0.XII summarizes the characteristics of aircraft designed for 610 and 910 meter field lengths. As noted previously, the AW and EBF aircraft represented here have about the same noise characteristics as the OTW/IBF aircraft with 1.35 FPR engines. Their direct operating costs are 10 to 11 percent higher. Penalties for meeting noise requirements would be increased to approximately double those listed in the above discussions. Further comparison of the MF and OTW/IBF aircraft is shown in Figure 0.13 for 0.75 M designs on the basis of fuel and field length. The 4-engined OTW/IBF is clearly supe- rior to the MF at field lengths shorter than 1070 m. (3500 ft.) while the 4 engined MF is superior at field lengths longer than 1220 m. (4000 ft.). However, it should be noted that minimum DOC's are achieved with the 2-engined, rather than the 4-engined MF and therefore the primary comparison should be between the 4 -engined OTW/IBF and the 2-engined MF. The direct operating costs of these concepts are presented in Figure 0.14 for 0.75 and 0.8 M and as a function of field length. At 910 m. (3000 ft.) and DOC-1, the OTW/IBF is superior at 0.8M, while the MF is slightly superior at 0.75 M. For DOC-2, the OTW/IBF is superior at 0.8 M, while the concepts are equal at 0.75 M. Iviii FIELD LENGTH 610 M (2000 FT) 910 M (3000 FT) NO. OF FUEL NO. OF FUEL CONCEPT ENG. M KG DOC-2 ENG. M KG DOC-2 (FPR) (LB) ¢/ASSM (FPR) (LB) ¢/ASSM 4 0.75 4,944 1.961 4 0.75 4,400 1.831 (1.35) (10,900) (1.35) (9,700) OTW/IBF 4 0.75 5,117 1.820 - (1.47) (11,280) 2 0.70 5,089 1.818 MF (1.35) (11,220) 2 + 2 0.75 5,688 2.015 AW (1.35/3.0) (12,540) 4 0.65 5,003 2.196 4 0.65 4,427 2.046 (11,030) (1.25) (9,760) DEFLECTED 4 0.55 3,293 1.629 SLIPSTREAM (T-56) (7,260) TABLE 0.XII SUMMARY OF 610 M AND 910 M (2000 AND 3000 FT) AIRCRAFT (MIN. DOC 2) lix in this area but experimental data are lacking. An improvement of 15 percent in DOC and 10 percent in fuel consumption was estimated for an engine arrangement which avoids the long exhaust duct. Improvement less than this magnitude, if verified experimentally, would make the OTW concept (possibly combined with IBF) an over- whelmingly superior approach at all field lengths up to 6000 feet. It is concluded that the hybrid OTW/IBF concept with design cruise speed of Mach 0.75 and FPR 1.35 engines should be considered the best potential solution for 910 m.(3000 ft.) or shorter field performance on the basis of lower fuel consumption and further potential for improvement. The versatility of full-load, longer range performance should be in- corporated; using CTOL runways; a 2780 Km (1500 n.mi.) range can be provided with a takeoff field length of 1280 m. (4200 ft.). If 1.35 FPR engines with 57.8 KN (13,000 lb.) thrust were developed, aircraft sized for 90, 120, or 150 passengers could be designed with 2, 3, or 4 engines. Recommended Compromise Concept The potential of the hybrid OTW/IBF for both 610 and 910 m. (2000 and 3000 ft.) field lengths and small noise footprints indicates that it should be pursued in research and development programs. Implementation decisions are downstream so that confirmation of the results of current analyses can be obtained and a minimum risk program could be initiated in the 1980's. Decisions and actions which are appropriate are the following: o Continuation of the Quiet STOL Research Airplane program. o Implementation of further analytical and experimental develop- ment of improved nacelle and engine installation with emphasis on improving cruise performance and determining the optimum combination of high speed and low speed installation approaches. o Analytical refinement of engine design characteristics through an integrated airframe/engine study in the fan pressure ratio range of 1.3 to 1.4 for noise. o Initiation of a quiet R/STOL engine development with technology drawn from the QCSEE program and guidance from the integrated airframe/engine study. Ixii Figure 0.15 summarizes the conclusions of the fuel conservation portions of the study by indicating the available fuel savings and the associated DOC and speed penalties at 1830 m. (6000 ft.) and 910 m. (3000 ft.) field lengths. Figure 0.16 summarizes the comparison of OTW/IBF and MF concepts at 910 m. (3000 ft.) field length from which it can be concluded that the OTW/IBF is economically superior in fuel and DOC at field lengths below 910 m. (3000 ft.) while the MF is superior at field lengths greater than 910 m. (3000 ft.). At 910 m. (3000 ft.) the OTW/IBF is considered superior because of its better fuel consumption, better ride quality, and greater po- tential for improvement. Figure 0.17 summarizes the conclusions regarding aspect ratio effects and the EBF, AW, and deflected slipstream lift concepts. The recommendations regarding the desirable engine fan pressure ratio and additional Research and Development are summarized in Figures 0.18 and 0.19 while the recom- mendations regarding noise requirements are summarized in Figure 0.20. Ixiii * AT 1830 M (6000 FT) F.L., o 926 KM,. MISSION FUEL CAN BE REDUCED BY UP TO 24% AT THE EXPENSE OF A 31% REDUCTION IN SPEED AND A 15% INCREASE IN DOC-2 (20% IN DOC-1). o BY OPTIMIZING FOR DOC-2, MISSION FUEL CAN BE REDUCED BY 5% FOR THE SAME DOC-2 AND A 7% REDUCTION IN SPEED * AT 910 M (3000 FT) F.L., o MISSION FUEL CAN BE REDUCED BY UP TO 20% AT THE EXPENSE OF A 31% REDUCTION IN SPEED AND A 12% INCREASE IN DOC-2 (18% IN DOC-1). o BY OPTIMIZING FOR DOC-2, MISSION FUEL CAN BE REDUCED 11% FOR THE SAME DOC-2 AND 7% REDUCTION IN SPEED. * 0.75 M AND OPTIMIZATION FOR DOC-3 ARE RECOMMENDED FOR FUTURE SHORT HAUL TRANSPORTS FIGURE 0. 15: SUMMARY OF RESULTS -- FUEL CONSERVATION o AT 910 M (3000 FT) F. L., o OPTIMIZED FOR DOCI AT 0.8M, THE OTW/IBF HAS 1% BETTER DOC AND 1% BETTER FUEL CONSUMPTION THAN MF. o OPTIMIZED FOR DOC2 THE OTW/IBF HAS 1% POORER DOC, 9% BETTER FUEL CONSUMPTION & 7% HIGHER SPEED THAN MF. o OPTIMIZED FOR DOC4, THE OTW/1BF HAS 2% BETTER DOC AND 13% BETTER FUEL CONSUMPTION THAN MF. o OPTIMIZED FOR MINIMUM FUEL, BOTH CONCEPTS ARE EQUAL. o OTW/IBF HAS BETTER RIDE QUALITIES THAN MF. o AT > 910 M THE MF IS BETTER THAN OTW/IBF IN BOTH FUEL CONSUMPTION AND DOC. o AT <.910 M THE OTW/IBF IS BETTER THAN MF IN BOTH FUEL CONSUMPTION AND DOC. FIGURE 0. 16: SUMMARY OF RESULTS - COMPARISON OF OTW/IBF AND MF Ixiv 1.0 INTRODUCTION 1.1 BACKGROUND Studies of Quiet Turbofan STOL Aircraft for Short Haul Transportation were conducted by Lockheed and McDonnell-Douglas for NASA Ames Research Center in 1972 and early 1973. These were reported in detail in references 1, 2, and 3. Both studies concluded that quiet short field aircraft can be economically viable and benefit both long and short-haul transportation. To be economically viable, field lengths of 3000 to 4000 feet were strongly preferred; operating cost penalties for 2000-foot or shorter field length appeared to be greater than could be balanced by STOL indirect benefits. In the Lockheed study it was determined that the various powered high lift concepts such as the externally blown flap, the internally blown flap, and the over-the-wing blown flap (upper surface blown flap) produced configurations with approximately equal economic results. However, two particularly promising concepts appeared to be the Over-the-Wing/Internally Blown Flap (OTW/IBF) hybrid at a field length of 910m (3000 ft.)and the Mechanical Flap (MF)at a field length of 12 2 0m (4000 ft.). Unfortunately, the data base upon which the OTW/IBF concepts is based is neither as extensive nor as well substantiated as competing concepts, such as the externally blown flap or augmentor wing. It was also shown that more economical vehicles could be developed for both these con- cepts if the 152 m (500 ft.) sideline noise level requirement was relaxed somewhat from 95 EPNdB. Additional benefits would accrue from such a choice of noise level since the engines suited for slightly higher noise level have fan pressure ratios (FPR's) on the order of 1.4 to 1.6 which make them suitable for advanced CTOL airplanes meeting FAR 36 minus 10dB noise levels, a level to be expected in the 1980 time period. It was therefore proposed to investigate and analyze the critical aspects of 910M (3000 ft.) OTW/IBF design to that level which will provide a meaningful configuration for developing test configurations for future R&D programs and to compare the performance 1 r of this concept to the performance of the MF concept at 9 10m (3000 ft.)field per- formance. The number of engines has a significant effect upon operating cost as illustrated by the mechanical flap configuration examined in references 1, 2, and 3. Whereas the preference for two engines for unpowered lift systems was clear-cut, more detailed analysis was required to resolve the question in a rigorous manner for powered lift systems. Accordingly, 2, 3 and 4 engine OTW/IBF vehicles were included in the present study and these were complemented with a study of a twin-engine augmentor- wing vehicle. Since the twin engine pure OTW and EBF configurations are virtually excluded by engine-out trim considerations and the other candidate configurations have already been examined, the AW study completed a comprehensive review of this aspect for all powered lift systems. (The twin-engine Boeing AMST is classified here as a hybrid OTW system since it uses leading-edge blowing.) Work was initiated on this study extension in July 1973. Early in the program it was observed that the fuel consumption of airplanes using the hybrid propulsive-lift concept was lower than for the mechanical flap or augmentor wing concepts for aircraft designed for 3000-foot field performance, low noise level, and cruise at M 0.8. The wing loading and aspect ratio for propulsive lift aircraft can be higher than that possible for a mechanical flap airplane at any given field length; this generally means lower fuel consumption. Increasing prices and scarcity of fuel in late 1973 highlighted the need to examine operating requirements such as cruise speed and altitudes, as well as the effect of different potential noise requirements, on fuel consumption and airplane design for minimum operating costs at higher fuel prices. Accordingly, an additional task was initiated in early January 1974 to cover these aspects. 1.2 OBJECTIVES This report describes the results of analyses integrated to accomplish the following objectives: o Detailed definitive design and economic comparison of 9 1(m (3000 ft.)field length MF, AW and OTW/IBF configurations. A primary objective is establishing credibility of performance estimates, including sensitivity to variations in basic data. 2 o Detailed determination of the economic and noise level effects of using an intermediate bypass engine suitable for an advanced CTOL, as well as use of a low-noise engine. o Development of the preliminary design of optimized OTW/IBF airplanes to that level which could provide test configurations for future R&D programs. o Development of additional data for OTW/IBF configurations with 610 and 107 0mn (2000 and 3500 ft.) field length capability and MF configurations with 1070 and 1220m (3500 and 4000 ft.) field length capability. o Evaluation of the fuel savings achievable by application of advanced lift concepts to a short-haul aircraft; determination of the effect on fuel con- sumption of different field lengths, cruise requirements and noise levels. 1.3 APPROACH Specific configuration design points were selected for different lift concepts and field lengths, as summarized in Figure 1 . Emphasis was placed on the points designated "preliminary design" in the figure: 9 10m (3000-ft.) field lengths for over the wihng/ internally blown flap, mechanical flap, and augmentor wing; 1220m (4000-ft.) field length for the mechanical flap. The preliminary design data was then extended to other field lengths, as shown. Initially these aircraft were optimized for M 0.8 cruise at 914 0m (30, 000 ft.) for minimum direct operating cost with 1972 prices for fuel, aircraft and engines, maintenance, and other DOC elements. Optimization would not be affected if these inflated uniformly; for convenience in comparing to previous studies, the 1972 price basis was maintained. However, the rapid price increase for fuel in 1973 indicated that fuel consumption would assume a more dominant position in airline economics and that airplane and engine features which conserved fuel should be evaluated from two standpoints: minimum fuel consumption and minimum direct operating cost optimizations at higher fuel prices. 3 2.0 SOME ASPECTS OF THE SHORT-HAUL SYSTEM SCENARIO The previous systems studies (References 1-3) highlighted the primary need for STOL short-haul capability for the relief of congestion at the major hub airports. An additional major advantage was cited as the increase in convenience to the public if additional airports could be utilized which were closer to the sources of origin and destination. Current study activity has involved an examination of the effect of recent developments on this scenario. Of major importance is the recognition that a very effective short- haul and long-haul air transportation network is functioning today. It is a complex interacting system in which a major effect on profitability of the long haul system is the short haul collection system which brings people to a hub airport by air in sufficient quantity to achieve profitable load factors on wide-body equipment. 2.1 ENERGY SHORTAGES AND AIRPORT CONGESTION The effects of the energy crises on airline operations have been discussed with representa- tives of Delta, Eastern, and Northeast Airlines. These discussions investigated the impact of short fuel supply on passenger travel habits, schedules, load factors, and average delay rates. Fuel allocations and increased fuel costs were also examined to determine the influence on operations and future planning. Anticipated changes in previously projected air passenger traffic growth and airport congestion were analyzed to better determine the benefits of quiet R/STOL aircraft for short haul traffic with short runways added on a non- interfering basis with CTOL operations. Air passenger travel habits have not changed as drastically as first anticipated. The reduction in low demand flights appears to have an insignificant effect on loss of passengers to other modes of transportation. Passengers appear to reschedule their own activities to accept other available flights. The anticipated passenger traffic has been boosted some- what by a shift to the airlines from automobile travel, caused by the gasoline shortage. Records show that the 1973 air passenger traffic exceeded expectations and 1974 is expected to exceed predictions made in the initial phases of the fuel crisis. 6 Schedule cuts have been made at the times of least demand so that peak hour airport operations have not been affected to any extent. Considerable improvements have been experienced in average load factor; however, this has not affected the ability to meet demand. Fuel allocation cutbacks have led the airlines to examine further the various means of conserving fuel in addition to eliminating low demand flights. Reduced throttle settings result in reduction in fuel consumption with no troublesome reduction in block time. Other methods exercised during peak hours as initiated by Reference 5 include holding a departing flight at the gate until clearance to takeoff is obtained, thereby conserving fuel in ground operations,or holdingat the point of origination until clearance is obtained at the point of destination to reduce.airborne delays. The higher fuel prices have increased the break even load factor, even though various cost reduction practices have been implemented. This has been offset somewhat by the improvements in average load factor that are presently being experienced. Continued fuel cost increases and lower fuel allocations are still a major concern with all airlines. This situation tends to favor the more fuel efficient wide body aircraft and, in some cases, airlines are attempting to accelerate the introduction of these aircraft into their route structure. The consensus of all airlines is more optimistic toward a continued passenger growth rate during the coming years. However, the predicted rate of growth varies somewhat. Airport congestion is not viewed as a significant problem for the next several years. Nevetheless, congestion is being viewed as a future problem that must be recognized in present planning. Atlanta and other cities are continuing to evaluate the anticipated traffic growth in terms of the need for expanding the capabilities of existing facilities and property or the need for acquiring additional property for new airports. Recognizing the extremely long lead times in obtaining necessary land and constructing required facilities, the Atlanta Regional Commission has an active transportation planning program in progress which is studying the feasible ways of meeting the future air traffic needs of the Atlanta area. A second airport 7 is in serious consideration at the present time to augment the capabilities of the Hartsfield Atlanta International Airport. New York is also looking at the possibility of an additional airport, and Chicago is still studying the problems of a workable system in the Midway/ O'Hare combination. Of course, any steps in developing additional workable airports for congestion relief will have a tendency to postpone the need for, and benefits to be derived from, R/STOL type aircraft operations. A recent paper by Charles L. Blake (Ref. 6) summarizes the report of the FAA Airport Study Team which highlights the groundside congestion problem assuming considerable ATC improvements in airside capacity. Recognizing the fuel shortage and the uncertainties in predicting future developments, it is noted that "the FAA Airport Study Team predicts a steadily increasing strain on airport capacity." Mr. S. B. Poritzky of the Air Transport Association has commented (Ref. 7) that "quantifiable ATC-based airport capacity improvements... are smaller than expected. The bigger payoff must come from optimized total airport design and enough runways, and in the long run more 'real-estate-stingy' airplanes." 2.2 DEMAND - CAPACITY ANALYSES The airport capacity and demand analyses in Reference 2 have been reexamined in the light of the energy crisis to determine if the saturation of major airport hub capacities still remains a serious concern inhibiting the growth and prosperity of the national air transportation industry. The changes resulting from the fuel shortage such as the anticipated future growth of air passenger traffic, airline operations, and cost of fuel were assessed in terms of future airport demand versus capacity and cost of delay under various levels of fuel costs. The cost of delay with and without R/STOL capabilities was compared to show the economics of augmenting airport CTOL capacity with R/STOL capabilities. All costs used in these analyses are in 1973 dollars. The Atlanta Airport was used as an example of a major hub airport in these analyses. Figure 2 shows the presently predicted demand and capacity of the Atlanta Airport. Some changes are shown from that reported previously in the predicted average aircraft seat capacity, average load factor, and the originating and connecting passenger ratio. 8 16 z , 12 ou 8 100 O 75 > < 50 FIGURE 3: PEAK HOUR DELAY ATLANTA AIRPORT 100 0 75 50 z p o1 •& 500- 150 400- u 100 -300 - U- Z 200 50 - 100 - 0 0 1970 80 90 2000 YEAR FIGURE 5: DELAY EFFECT ON FUEL CONSUMPTION - ATLANTA AIRPORT 200 - @ 23/GAL / - - - @ 46/GAL O WITHOUT ATC // - IMPROVEMENTS - 150/ / 4 WITH ATC / / 0 IMPROVEMENTS/ LL 100 0 / L- Ou 50 *00, ow WITH R/STOL ) RUNWAYS 1970 80 90 2000 YEAR FIGURE 6: ANNUAL COST OF DELAY - ATLANTA AIRPORT 12 Savings in fuel through relief of congestion would be achieved, also, by construction or use of additional airports. The California corridor represents a significant example of the successful dispersion of air traffic from the hubs to secondary airports; the volume of passengers not interconnecting with long-haul is high enough to support this system with sufficient frequency of flights at the secondary airports. However, the importance of the interconnection problem in other areas must be recognized. Chicago and Atlanta are primary examples of the cases where a short-haul collecti on system brings passengers to an interchange which offers a tremendous choice of destina- tions with high frequency of service. Some quotations from a working paper of the Atlanta Regional Commission, Reference 14, serve to illustrate the magnitude of this valuable service to the public: "Atlanta now serves 92 cities with nonstop flights...some 597 nonstop flight departures daily... A large number of the Atlanta nonstop flights are on-line continuation flights which provide service to other cities involving one or more stops... (including off-line connections) these scheduled routes provide service to 171 other cities... (providing) convenient access to alldomestic airports when the connection potential of the served cities is considered... for every 100 inbound plus outbound passengers at Atlanta only 27 are Atlanta orginations or destinations. Only one in 10 of the inbound plus outbound passengers is a resident of the Atlanta region." "During the morning busy hour from 10:00 o'clock to noon there are over 200 scheduled flights at the Atlanta airport. Flight connections are those flights departing one-half hour to two hours after a flight arrival. There are 97 flight arrivals from 68 different cities during the time interval from 10:00 o'clock to 11:30 daily each morning. There are 89 flight departures to 72 different cities during the time interval from 10:30 o'clock to noon... a total of 4,093 directional flight connections can be made during the peak involving service between the 116 different cities. Each day Atlanta provides over 14,000 directional flight connections." "Diversion of connecting passengers may be a natural result of the evolution of a mature domestic route network. The medium hubs surrounding Atlanta will grow and develop more nonstop routes in the future. Cities such as Birmingham, Memphis, Nashville, Charlotte and Jacksonville will provide additional flight connections in the future which will permit passengers to use these airports as alternative connection points having a more direct path than Atlanta between cities connected. In addition, Birmingham/Charlotte nonstop service will become more frequent which provides a diversion by overflying Atlanta. Other examples of overflights would be between the grawing medium hubs and other large hubs, such as: Charlotte/Miami and New York/Birmingham... Atlanta scheduled 13 In very approximate terms, air transport revenue passenger miles grew 10 percent annually from 1967 to 1972 while fuel use grew about 5 percent annually. It is projected that air passenger growth may be maturing such that growth rates of 6 to 8 percent are pro- jected for the future along with fuel demand growth rates of 2 to 4 percent. (The fuel requirements are, of course, lower because of the phasing-in of larger, more 'fuel-efficient' aircraft.) It is concluded that requirements for aircraft fuel are likely to grow more slowly than the most modest estimates of total energy growth rates. Therefore, extreme penalties in airplane design and economics for absolute minimum fuel consumption are unwarranted. Fuel is likely to be available, especially if the recognized current good performance of the airlines in conserving fuel is continued. Aviation fuel could come from a combination of domestic and imported fuel, in which case air transportation would contribute detrimentally to the balance of payments problem -- to the extent of a billion dollars a year or more in the next few years but still only 5 per- cent of the balance of payments deficit generated by the other petroleum users. It seems likely that solutions for converting coal and shale will be implemented; something of this kind is essential to avoid the trade deficit and a rational ceiling would be available to avoid arbitrary wild upward swings in fuel prices. Studies at NASA Ames Research Center have indicated that these processes may stabilize aircraft fuel prices at two to three times the 1972 levels. No projections have been observed for fuel prices returning to less than twice 1972 prices. It is concluded that future aircraft design and operational procedures should be predicated on at least double the 1972 fuel price -- and escalated or inflated from that point along with the rest of the economy. The aircraft design implications of fuel shortages include a slight lowering of design speeds to those which give minimum operating costs at the higher fuel prices. Fuel savings offset the penalty of increased block times. Moderate weight and cost increases for wings with higher aspect ratios are more than balanced by the savings in fuel costs. The lowering in speed also permits an increase in wing aspect ratio with minimum weight penalty. Of particular significance is the increase in aspect ratio without weight penalty which can be afforded by the greater thickness of advanced supercritical airfoils. 16 2.4 ASSESSMENT OF COMMUNITY NOISE PROJECTIONS The premise is advanced that the proposed rules for fleet noise levels will be in effect or that modifications will achieve the same effect by 1980 -- all aircraft at or below FAR Part 36. Although the L1011 and DC-10 are quieter than the levels permitted by FAR Part 36, the EPNdB levels of smaller aircraft just meeting Part 36 are roughly the same as the noise level of the heavier wide-body aircraft. Frequency at the major air- ports is unlikely to increase significantly since passenger growth can be satisfied by substitution of larger aircraft. Thus, frequency and level of noise exposure will not change significantly by 1980. Airplanes being delivered now or on order will be in service through the 19 80 's and it seems clear that it would be disastrous to both the airline and the national economy to force more stringent standards on this fleet. Nevertheless, a gradual lowering of average fleet noise levels (and average airport community exposure levels) seems to be in the best interest of all concerned. Design requirements for new aircraft of 10 dB below existing FAR 36 levels are highly probable by the 19 80's. It would be logical that a fleet noise averaging process be incorporated in the regulations so that the community noise benefit of the gradual introduction of quieter aircraft could be passed on as an incentive to airline operators. Further quieting to 90 EPNdB at the airport boundary (18 EPNdB below the FAR 36 level 3.5 N.M. from brake release) for large aircraft was called for as a research goal by the CARD study (Ref. 11). Aircraft below 34,000 Kg (75,000 lb.) gross weight would have a level of 80 EPNdB at the airport boundary (22 dB below the FAR 36 level for approach noise at 1 N.M. from threshold). These goals are indeed ambitious, as the CARD report recognized in stating "... establishment of such ambitious research goals at this time is a controversial issue but the failure to establish a low-level noise goal now could result in the application of scarce resources to R and D activities that may fail to provide the desired solution to the noise problem on a long-term basis." It is concluded that designers of new aircraft to be operational by 1985 should recognize the high probability of a FAR 36 minus 10 noise requirement (as others have concluded, 17 Ref. 12 and 13) . Further lowering of levels for large long-range CTOL aircraft is likely to be much slower in coming, as the economic penalties are high for this class of aircraft. Aerodynamic noise calculations and measurements on 272,000 Kg (600,000 lb.) aircraft show that FAR 36 minus 8 to 10 EPNdB would be the lowest noise level on approach that a large CTOL aircraft could achieve, regardless of how quiet the engines are. Additional quieting of aerodynamic noise would require a technological break- through or a decrease in approach speed (toward R/STOL characteristics). For long- range aircraft the penalties for this performance have not been assessed. For shorter- range aircraft the penalties may not be prohibitive for further lowering of noise level by 1990. If aircraft capacity is increased by provision of non-interfacing runways for short haul aircraft, new areas of the community are subject to impingement by aircraft noise. The appropriate compromise for establishing an allowable level at the airport boundary has not been established. The CARD research goal shows noise level varying from 80 EPNdB for 34,000 Kg (75,000 lb.) aircraft to 90 EPNdB for 272,000 Kg (600,000 lb.) aircraft. The data needed for a rational answer would be the tradeoff of aircraft operating cost against the cost to move the airport boundary. Data on the aircraft cost portion of this balance are given in subsequent sections of this report. It seems clear that the noise level on the takeoff or approach path will be more pertinent than the sideline noise level. 2.5 POTENTIAL SOLUTIONS The data and analyses presented in subsequent sections of this report reaffirm the potential of technology advances in airfoil technology, high bypass engine development, ride quality technology, and propulsive lift. It will be shown that fuel conservation and low noise are compatible requirements and that reduced field lengths can be achieved with minimum operating cost penalties for short-range aircraft. 18 higher in available runway lengths. McDonnell-Douglas emphasized the use of secondary airports for city-pairs with significant local origination and destination traffic. They concluded that 910 m. (3000 ft.) field performance would be desirable and that this capability was available at almost every site examined. Lockheed emphasized the importance of interconnection with other airline flights and suggested that congestion and noise relief would occur if CTOL short haul traffic was offloaded to non-interfering short haul runways of 910 m. (3000 feet) or more at existing hub airports. The need for ex- panding the airport boundaries would be zero or minimal if the runway lengths were 910 m. (3000 feet) and would increase at some of the major airports if runway lengths of 1220 m. (4000 feet) were required. The Aviation Advisory Committee concluded that 1220 m. (4000 feet) runways were appropriate, and needed for short haul transport. No definitive cost tradeoff has been made that includes the airport expansion cost increment as a function of runway length. It is concluded that the requirement for 9 10m. (3000 feet) airplane capability is sufficiently probable that it should continue to be pursued. Condi- tions in the late 198 0's and beyond are most likely to lend considerable value to a 'real- estate stingy' airplane. The design requirement that the airplane be capable of a given field performance on a 95 0 F day has been associated with a sea level field elevation. It seems reasonable that higher- elevation airports can be assumed to compensate with additional runway length for the elevation effect. Other field requirements have also been included in the current study: 610 m., 1070 m. 12 20 m. and 1830 m. (2000, 3500, 4000 and 6000 ft.). The consequent airplane designs and economics give perspective to the effect of this variable. 3.1.4 Cruise Speed and Altitude Cruise speed of M 0.8 and 9140 m. (30,000 feet) altitude were selected as design re- quirements for 926 km (500 n.mi.) aircraft in the basic system study, based on the following considerations: o Initial screening of quiet propulsive lift aircraft indicated that this performance gave the lowest direct operating cost in most cases - at 1972 cost and fuel price levels. 21 o Air-traffic compatibility with aircraft currently employed in short-haul air transport indicated the desirability for cruise in the neighborhood of M 0.8. o For stage lengths up to 926 km..(500 n.m.), flexibility in routing and ATC assignments indicated the desirability of 9140 M. (30,000 FT.) altitude capability. o For 926 km. (500 n.m.) flights it was felt that-block times should be approximately equivalent to those available from CTOL aircraft now performing the mission so that this factor would not be detrimental from the standpoint of passenger preference. With the advent of an aircraft fuel shortage, and increased fuel prices, the aircraft in current use were slowed slightly to conserve fuel. This was beneficial with current aircraft designs such as the DC-9, down to approximately M 0.75. The influence on block time was negligible from the standpoint of the passenger for short-haul segments. Direct operating costs, in real terms, were either unaffected or slightly reduced from the fuel saving, compared with what they would be at faster speeds and lower block times. This amount of slow down did not require rescheduling of the airplane so that it flew as many revenue-miles per year as previously; the annual utilization increased in terms of block hours and the annual productivity was essentially unchanged. In considering new short-haul aircraft designs it was considered appropriate to reexamine design cruise speed and altitude as they affected fuel consumption and direct operating cost at higher fuel prices. Design cruise speed of M 0.75, and perhaps lower would be competitive with current generation aircraft in the short-haul mission and would be compatible with air traffic in this environment. An evaluation of the effect of cruise speed and altitude, as a function of fuel price, is presented in the following sections of this report. It is suggested that aircraft flying a spectrum of stage lengths up to 900 km, with average stage lengths of 400-500 km., should have the capability of flying M 0.75 at 9 140m. (30,000 feet). In the following analyses, the DOC calculations are con- servatively high for the slower aircraft because annual utilization has been assumed to be 2500 hr. per year; in practice the slower aircraft would probably have a higher 22 annual utilization in terms of hours. The annual productivity in short-haul missions would probably be as high as faster aircraft. 3.1.5 Flight Profile and Reserves The flight profile and definition of fuel reserves were presented in Reference 1/2. No changes from the conditions selected initially have been deemed necessary or desirable. The following summarizes the criteria used: 1. Takeoff and initial climb according to the performance criteria discussed in Section 3.2. 2. Powercut-back at 213 m. (700 feet) for 4-engine aircraft or 305 m. (1000 feet) for 2 -engine aircraft to that throttle setting which will maintain a positive climb gradient if an engine fails (Ref. FAR Part 36). 3. Acceleration to 250 KEAS and maximum climb at this speed after reaching a point where ground noise level is below 80 PNdB. It is recognized that the safety of the cutback maneuver has been questioned and that it is generally not applied below 460 meters (1500 ft.) when it is used in current practice. This is discussed later in connection with' the noise data. 4. Climb to 3050 m. (10,000 feet) at 460 km./hr. (250 knots) EAS with allowance of 2 minutes for air maneuver. 5. Climb to cruise altitude at best climb speed for minimum block time. 6. Cruise at design cruise speed. 7. Descend at best descent speed for minimum block time, decelerating to 460 km./hr. (250 knots) EAS at 3050 m, (10,000 feet). Cabin pressurization of 61 KN/m 2 (8.8 psi) was established to permit maximum climb and descent rates while restricting change of pressure in the cabin to 91 m. (300 feet) per minute change in cabin altitude. 23 o distance to accelerate to V1 and clear 10.67 m. (35 ft.) with critical engine failure at V1 o distance to acclerate to V 1, followed by an average deceleration rate of 0. 4 g to a stop with a 3 second time delay between acclera- tion and deceleration phases. o Rolling coefficient of friction - 0.015 o Lift-off/stall pseed ratio = 1.15 - 1 engine out (PL) = 1.20 - all engines operating (PL) = 1.20 (MF) o Minimum load factor capability = 1.20 - I engine out (PL) = 1.30 - all engines operating (PL) = 1.30 (MF) o FAR minimum control speed margins. o FAR 25 and XX second segment climb gradient = 2.4 percent for two engine aircraft = 2.7 percent for three engine aircraft = 3.0 percent for four engine aircraft o Landing: o Sea level field at 350 C (950F) o Minimum approach/stall speed ratio = 1.20 - 1 engine out (PL) = 1.25 - all engines operating (PL) = 1.30 (MF) o Minimum load factor capability = 1.20 - 1 engine out (PL) = 1.30 - all engines operating (PL) = 1.30 (MF) o Approach over 10.67 m. (35 ft.) with sink rate = 4.6m./sec (900 fpm) 26 o Flare to touchdown at 3 m./sec-(10 FPS) o 1 second delay between touchdown and brake and/or thrust reverser application o Roll out deceleration rate = 0.35g o Landing field length = landing distance divided by 0.6. o FAR 25 and XX approach climb gradients = 2.1 percent for two engine aircraft = 2.4 percent for three engine aircraft = 2.7 percent for four engine aircraft o FAR 25 and XX landing climb gradient = 3.2 percent 3.3 OPERATIONAL OUALITIES 3.3.1 Handling Qualities The philosophy and reference studies of handling qualities are discussed in Section 2.7 of reference 2; criteria selected are summarized below. Longitudinal - For STOL aircraft the trim requirement plus maneuver capability for landing approach at the approach speed is most critical and will be used to establish the tail size and type of horizontal tail. To the basic trim requirement is added a maneuver capability of 0.3 rad/sec 2 at the most forward center of gravity. This level of pitch acceleration beyond trim produces a pitch angle in the first second of 4.3 degrees assuming maximum control deflection is achieved in 0.3 seconds with a 0. 1 second transport lag and a time constant of 2.0 seconds. Lateral - The criteria for lateral control power required is based on an acceleration capability of 0.42 rad/sec 2 at the landing approach speed in symmetric flight. A further 27 requirement is to retain 30 percent of this control power for maneuvering after trimming a critical engine failure in a 46 km/hr (25 knot) crosswind at the approach speed. Directional - Directional control power requirements are expressed in terms of the ability to trim the most critical engine failure in the presence of a 25 knot (46 Km/hr) crosswind at the approach speed and an initial yaw acceleration capability in trimmed flight of 0.16 rad/sec 2 3.3.2 Ride Qualities The criteria for ride qualities were RMS gust levels of 1.7 m/sec (5.7 ft/sec) for cruise, 2.5 m/sec (8.2 ft/sec) for descent, and 3.0 M/sec (9.8 ft/sec) for landings were used. These criteria are sufficient to insure that a design goal is achieved. However, since scale of turbulence is such an important parameter which at times seems as arbitrary as the criteria, it should also be specified. The values used in this analysis for the longitudinal scale of turbulence were 990, 570 and 210 m (3250, 1700 and 700 feet) for the cruise, descent, and landing approach conditions respectively. The velocities considered were M 0.8 and 9100 m (30,000 ft.) for cruise, 463 km/hr (250 knots) at 1500 m (5000 ft) for the descent, and a velocity that varied with configuration (1.25 V ) at 150 m (500 ft) for the landing approach. 3.4 NOISE CRITERIA Potential noise criteria of the 1980's were discussed in Section 2.4. It was concluded that aircraft noise requirements equivalent to FAR 36 minus 10 EPNdB should be the basis for a new design of CTOL aircraft; further reduction of approach noise would require a lowering of approach speeds which would introduce the trend toward R/STOL performance. Short-haul runways on hub airports or use of secondary airports will require different criteria such as minimum footprint area and length. Downtown STOLports, now regarded as unlikely to be accepted or be operational in the 1980's, might well require 80 to 90 EPNdB noise levels at the airport boundaries; the Sperry box dimensions would represent a rectangular area 1830 m. (6000 feet) long by 610 m. (2000 feet) wide. 28 the unit price for this quantity would be 25 percent higher than the price for a 1500-unit production. The effect of this is approximately 4 percent increase in aircraft DOC and this effect is shown in the subsequent analyses. However, it was concluded that engines with fan pressure ratios of 1.35 to 1.6 would have sufficient value for CTOL applica- tions that the larger. production quantity should be used as the baseline condition for the evaluation of twin-engine aircraft for this category of engines. 31 4.0 OVER-THE-WING/INTERNALLY BLOWN FLAP (OTW-IBF) VEHICLES 4.1 OTW-IBF CONCEPT The evaluation of alternate lift concepts in reference 2 showed the hybrid OTW-IBF to be particularly promising for field lengths of 910m (3000 ft).and less, where the augmentor wing (AW) might have been expected to be superior. More- over it did not appear to be at a great disadvantage to the preferred longer-field concept, i.e., the mechanical flap (MF) for fields approaching 12 2 0m (4000 ft). Since the hybrid concept was necessarily based upon a far less extensive technology data base than either of these competing concepts, a more refined conceptual design of the hybrid vehicle for 9 10m (3000 ft) has been undertaken in subsequent studies, which are reported here in order to improve the credibility of economic comparisons. Furthermore all vehicles in in reference 2 were constrained to a common 152 m (500 ft) sideline noise level of 95 PNdb which generally necessitated the use of acoustic splitters as well as nacelle wall treatment. It now appears that the use of wall treatment alone and an appropriately selected fan pressure ratio are the most economic means of compliance with noise criteria. Accordingly subsequent studies have been bbsed upon nacelle wall treatment alone for each candidate fan pressure ratio (FPR) engine and imply variable noise standards from which trade studies of cost and noise may be developed (as discussed in Section 8.0). The OTW-IBF vehicles derived for the foregoing purposes which are described in Section 4.4 retain the baseline mission requirements established in reference 2 and carry 148 passengers over a capacity payload stage length of 926 km (500 n mi) when operating from a 9 10m (3000 ft) field. The baseline cruise speed and the initial cruise altitude are Mach 0.8 and 9140m (30, 000 ft) respectively. A more surprising trend observed in the vehicle data from reference 2 was the indica- tion that powered lift concepts such as the OTW-IBF might offer mission fuel savings relative to MF vehicles. Accordingly fuel-conservative OTW-IBF vehicles have also been derived in the studies reported here and are described in Section 4.5. The scope of the investigation of these aspects has been greatly expanded from that of the baseline mission vehicles in that significant mission parameters (cruise speed, altitude 32 and field length) have been optimized as well as the main configuration parameters included in both cases. Furthermore attention has been equally devoted to mission fuel consumption per se and operating costs at the elevated fuel prices now in prospect whereas the baseline mission vehicles have been optimized with respect to DOC at 1972 prices (as in reference 2). The baseline mission vehicles have high-wing arrangements and a landing gear which is mounted on a fuselage seating six-abreast in a single aisle arrangement. Subsequent examination of alternate fuselage configurations has indicated that whereas the addi- tional weight and surface area of a twin aislesix-abreast arrangement would increase mission fuel by 2.6% and DOC by 1%, a single aisle five-abreast arrangement was both lighter and had a lesser surface area. Because of the 1% saving in fuel and 0.3% saving in DOC of this configuration, all fuel conservative vehicles have the longer five- abreast fuselage which implies a longer landing gear and thus a low-wing arrangement for its convenient attachment and retraction. The two classes of vehicle also differ with respect to engine location in that a two-engine arrangement is preferred for the base- line mission with the most inboard possible nacelle location which is best suited to the IBF ducting requirements and incidentally minimizes the asymmetric lift and rolling moment following engine failure. With the substantially higher aspect ratio wings, at which the fuel conservative vehicles are optimized, a four-engine con- figuration has generally appeared more advantageous. Independently cross-ducted IBF flows were utilized in the two-engine OTW-IBF in reference 2 in order to exploit asymmetric IBF lift as a counter to the rolling moment induced by the OTW asymmetry in single-engine operation. However it was shown that this arrangement seriously impeded fuel storage provisions and thereby precluded wing loadings exceeding approximately 440 Kg/m 2 (90 Ib/sq ft) which was an effective barrier to further DOC reduction. Furthermore the IBF duct losses associated with the unavoidable changes in flow direction effectively restricted the IBF flow to little more than 10% of the total fan flow which was undesirably low. From consideration of all possible duct configurations it has been concluded that the most desirable arrangement which minimizes the intrusion upon fuel storage volume and yet satisfies 33