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156 AFDD Weight Models 19–5 Alighting Gear Group The alighting gear group consists of: basic structure, retraction, and crashworthiness structure. There are two models, parametric (AFDD82) and fractional. The basic landing gear weight is: parametric wLG =0.4013W 0.6662 fractional wLG = fLGWMTO MTO N 0.5360 LG (W/S) 0.1525 and WLG = χLGwLG. Typically fLG =0.0325 (fractional method). Based on 28 aircraft, the average error of the parametric equation is 8.4% (fig. 19-11). The retraction and crashworthiness weights are: wLGret = fLGretWLG wLGcw = fLGcw(WLG + WLGret) WLGret = χLGretwLGret WLGcw = χLGcwwLGcw Typically fLGret =0.08, and fLGcw =0.14. Parameters are defined in table 19-8, including units as used in these equations. Table 19-8. Parameters for landing-gear weight. parameter definition units WMTO maximum takeoff weight lb fLG landing gear weight (fraction maximum takeoff weight) W/S wing loading (1.0 for helicopter) lb/ft2 NLG number of landing gear assemblies fLGret retraction weight (fraction basic weight) crashworthiness weight (fraction basic and retraction weight) fLGcw 19–6 Engine Section or Nacelle Group and Air Induction Group The engine section or nacelle group consists of: engine support structure, engine cowling, and pylon support structure. The weights (AFDD82 model) are: Wsupt = χsupt0.0412(1 − fairind)(Weng/Neng) 1.1433 N 1.3762 eng Wcowl = χcowl0.2315S 1.3476 nac Wpylon = χpylonfpylonWMTO Based on 12 aircraft, the average error of the engine-support equation is 11.0% (fig. 19-12). Based on 12 aircraft, the average error of the engine-cowling equation is 17.9% (fig. 19-13). The air induction group weight (AFDD82 model) is: Wairind = χairind0.0412fairind(Weng/Neng) 1.1433 N 1.3762 eng Typically fairind =0.3 (range 0.1 to 0.6). Based on 12 aircraft, the average error of the air induction equation is 11.0% (fig. 19-14). Parameters are defined in table 19-9, including units as used in these equations.
AFDD Weight Models 157 Table 19-9. Parameters for engine section, nacelle, and air induction weight. parameter definition units WMTO maximum takeoff weight lb Weng weight all main engines lb number of main engines Neng Snac wetted area of nacelles and pylon (less spinner) ft2 fairind fpylon air induction weight (fraction nacelle plus air induction) pylon support structure weight (fraction WMTO) 19–7 Propulsion Group The propulsion group consists of the engine system, fuel system, and drive system. 19-7.1 Engine System The engine system consists of the main engines, the engine-exhaust system, and the engine accessories. The engine-system weights are: Weng = χengNengWone eng Wexh = χexhNeng(K0exh + K1exhP ) Wacc = χacc2.0088 flub(Weng/Neng) 0.5919 N 0.7858 eng where flub =1.4799 if the accessory weight includes the lubrication system weight, 1.0 if the lubrication system weight is in the engine weight. The exhaust-system weight is per engine, including any IR suppressor. The accessory-weight equation is the AFDD82 model. Based on 16 aircraft, the average error of the accessories equation is 11.5% (fig. 19-15). Parameters are defined in table 19-10, including units as used in these equations. Table 19-10. Parameters for engine-system weight. parameter definition units Neng number of main engines P installed takeoff power (SLS static, specified rating) per engine engine exhaust weight vs. power, constants hp K0exh,K1exh 19-7.2 Propeller/Fan Installation The rotor group equations are used for propellers. 19-7.3 Fuel System The fuel system consists of tanks and support structure (including fuel tanks, bladders, supporting structure, filler caps, tank covers, and filler material for void and ullage), and fuel plumbing (including fuel-system weight not covered by tank weight). The fuel-system weights (AFDD82 model) are: Wtank = χtank0.4341C 0.7717 int N 0.5897 int fcwf 1.9491 bt Wplumb = χplumb K0plumb + K1plumb(0.01Nplumb +0.06Neng)(F/Neng) 0.866
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NASA/TP-2009-215402 NDARC NASA Desi
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NASA/TP-2009-215402 NDARC NASA Desi
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TABLE OF CONTENTS CHAPTER 1 - INTRO
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TABLE OF CONTENTS (cont.) CHAPTER 1
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viii LIST OF FIGURES (cont.) Figure
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Chapter 1 Introduction The NASA Des
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Introduction 3 of rotorcraft config
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Introduction 5 previous case DESIGN
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Introduction 7 4) Scully, M.; and F
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Chapter 2 Nomenclature The nomencla
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Nomenclature 11 Fuel Tanks Power Na
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Nomenclature 13 Motion aF AC aircra
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Chapter 3 Tasks The NDARC code perf
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Tasks 17 engine group is found (inc
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Tasks 19 3-4 Maps 3-4.1 Engine Perf
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Chapter 4 Operation 4-1 Flight Cond
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Operation 23 e) Input payload weigh
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Operation 25 Table 4-1. Mission seg
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Operation 27 horizontal ground dist
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Operation 29 climb for zero power m
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Operation 31 a) Horizontal velocity
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Operation 33 From the pressure p =
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Chapter 5 Solution Procedures The N
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Solution Procedures 37 Sizing Task
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Solution Procedures 39 relaxation i
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Solution Procedures 41 Table 5-4. T
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Solution Procedures 43 successive s
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Solution Procedures 45 initialize e
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Chapter 6 Cost Costs are estimated
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Cost 49 Table 6-1. DoD and CPI infl
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Cost 51 predicted base price (1994$
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Chapter 7 Aircraft The aircraft con
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Aircraft 55 The tilt control variab
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Aircraft 57 forward axes for descri
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Aircraft 59 For steady-state flight
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Aircraft 61 where Δz F = z F − z
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Aircraft 63 disk area); or the drag
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Aircraft 65 7-10 Performance Indice
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Aircraft 67 WEIGHT EMPTY STRUCTURE
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Chapter 8 Systems The systems compo
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Chapter 9 Fuselage There is one fus
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Fuselage 73 αe = αfus − αzl, w
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Chapter 10 Landing Gear There is on
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Chapter 11 Rotor The aircraft can h
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Rotor 79 propulsion group. The driv
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Rotor 81 plane command. The collect
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Rotor 83 or just CSF = WCHF with no
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Rotor 85 If μ is zero, the equatio
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Rotor 87 The velocity ratio is fW =
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Rotor 89 T/T ∞ 1.3 1.2 1.1 1.0 Ha
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Rotor 91 TPP tilt / cyclic magnitud
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Rotor 93 with an average over the r
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Rotor 95 (all equal to 1 for μz =0
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Rotor 97 κ 1.30 1.25 1.20 1.15 1.1
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Rotor 99 (C T /σ) s c d mean 0.20
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Rotor 101 11-5.1.3 Twin Rotors For
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Rotor 103 The wake is a skewed cyli
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Page 119 and 120: Chapter 12 Force The force componen
Page 121 and 122: Chapter 13 Wing The aircraft can ha
Page 123 and 124: Wing 111 denotes outboard edge, sub
Page 125 and 126: Wing 113 13-3.1 Lift The wing lift
Page 127 and 128: Wing 115 The wing interference at t
Page 129 and 130: Chapter 14 Empennage The aircraft c
Page 131 and 132: Empennage 119 14-4 Weights The tail
Page 133 and 134: Chapter 15 Fuel Tank 15-1 Fuel Capa
Page 135 and 136: Fuel Tank 123 if Wfuel >Wfuel−max
Page 137 and 138: Chapter 16 Propulsion The propulsio
Page 139 and 140: Propulsion 127 If the sum of the fi
Page 141 and 142: Chapter 17 Engine Group The engine
Page 143 and 144: Engine Group 131 The engine group p
Page 145 and 146: Engine Group 133 specific fuel cons
Page 147 and 148: Chapter 18 Referred Parameter Turbo
Page 149 and 150: Referred Parameter Turboshaft Engin
Page 159 and 160: Chapter 19 AFDD Weight Models This
Page 161 and 162: AFDD Weight Models 149 The spar-cap
Page 163 and 164: AFDD Weight Models 151 19-1.2 Aircr
Page 165 and 166: AFDD Weight Models 153 where w = nz
Page 167: AFDD Weight Models 155 units as use
Page 171 and 172: AFDD Weight Models 159 where fP = f
Page 173 and 174: AFDD Weight Models 161 The conversi
Page 175 and 176: AFDD Weight Models 163 19-12 Foldin
Page 177 and 178: AFDD Weight Models 165 error (%) er
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