Vendetta Final Proposal Part 1 (3.4 MB) - Cal Poly

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2 Defining the Design DomainAn initial takeoff weight estimate was made using historical aircraft data. First, a database of aircraft similar inmission was compiled. Next, an iterative weight fraction method outlined in Roskam. This method calculates the weightfraction for each mission segment. Using the resulting weight fractions, the aircraft gross takeoff and empty weightswere iterated until a weight fraction consistent with the historical trends was reached. Figure 2.1 shows the historicaltrend in aircraft weight fractions and the initial estimate of <strong>Vendetta</strong>’s empty and takeoff gross weights. The results ofthe weight fraction method are shown in Table 2.I.Figure 2.1 - Historical Weight Fractions & Weight Fraction EstimatesTable 2.I - Weight Fractions & WeightsMission Segment WeightsWeightsFractionsStart/Takeoff 6% Takeoff 108,400 lbClimb To Cruise 11% Empty 51,600 lbCruise-Out 25% Fuel 47,600 lbDash-Out 17% Payload 9,054 lbDash-Back 14% Fuel Weight Fraction 47.6%Cruise-Back 16%30 Minute Reserve 6%Misc. 5%Total 100%Warm -upMisc.Reserve Initial ClimbCruise BackCruise OutDash BackDash Out5
The weight fraction method provides a rough starting point for aircraft takeoff gross weight. The assumptionsused in the weight fraction method are listed in Table 2.II. Inaccuracies of up to 10% are possible depending on thequality of the initial assumptions, and 20% is not uncommon for unusual missions such as the one outlined in the RFP.Another source of inaccuracy is the historical aircraft used to define weight fraction trends. Because no supercruisingstealth bombers currently exist, many subsonic aircraft or non-stealthy aircraft were used in the historical aircraftdatabase.Once a starting TOGW is known, the physical dimensions can be estimated using a constraint plot. Theconstraint plot examines the relationship between two variables based on given requirements. Generally for initial sizingof an aircraft, the two variables used are sea-level takeoff wing loading and thrust-to-weight ratio. The RFP providesmany performance requirements that can be written as functions of these design parameters. Equations for range,specific excess power, takeoff and landing distance, and others from in Roskam, Nicolai, and Raymer were used todefine the constraints produced by these requirements. Additional assumptions were made to create the constraint plot asshown in Table 2.III.Table 2.II - Weight Fraction AssumptionsTable 2.III - Constraint AssumptionsSFC _CruiseSFC _DashSFC _TurnSFC _LoiterL/D Cruise 10L/D Dash 10L/D Turn 10L/D Loiter 121.11 lbm/lbf-hr1.11 lbm/lbf-hr1.11 lbm/lbf-hr0.8 lbm/lbf-hrC Lmax_TO 1.8C Lmax_CR 1.2C LCruise 0.2AR 3e 0.8The constraint plot in Figure 2.2 shows how thrust-to-weight ratio and wing loading relate to a specificperformance constraint. This allows an acceptable thrust-to-weight ratio and wing loading to be found. Note that anydesign points on the hatched side of a constraint would not meet the specific design requirement that that constraintrepresents. The constraint plot clearly identifies a design domain in which any combination of thrust-to-weight ratio andwing loading would satisfy all of the design requirements.The combination of the weight fraction method and the constraint plot provided an initial estimate the physicalsize and weight of the airplane. From the acceptable wing loading and thrust-to-weight ratio values determined from theconstraint plot, a single point must be chosen. A design with a higher wing loading will result in a smaller aircraft,which will be less expensive and easier to maintain. High thrust to weight ratios will require larger, more expensive andless efficient engines. Many assumptions were used to create the individual constraints, so the true effect of the6
Page 6 and 7: Figure 11.1 - 1-g Military Specific
Page 8 and 9: Nomenclature6DOF Six Degrees of Fre
Page 10: 1 IntroductionThe American Institut
Page 13: Table 1.III - Comparison of the F-1
Page 17 and 18: 3 ConfigurationThe current configur
Page 19 and 20: • Span = 53 ft• m.a.c. = 32 ft
Page 21 and 22: VendettaChris DroneyNate SchnaibleK
Page 23 and 24: low signature axisymmetric advanced
Page 25 and 26: 0° Lookup77°50403020100-10-20-30-
Page 27 and 28: 5.2 Wing SweepThe next wing paramet
Page 29 and 30: 5.3 Wing ThicknessThe effect of win
Page 31 and 32: 0.10.050-0.05-0.1-0.150 0.1 0.2 0.3
Page 33 and 34: 5.6 DragDrag was divided into four
Page 35 and 36: 6 PropulsionIn developing the propu
Page 37 and 38: Turbine Engine Technology (IHPTET)
Page 39 and 40: 35,00030,000Sea Level 1.5K 5K10K20K
Page 41 and 42: 0.990.980.97Pressure Recovery0.960.
Page 43 and 44: oundary layer diverter for high spe
Page 45 and 46: 7 Structural Layout & Material Sele
Page 47 and 48: Vertical AttachmentPointsHorizontal
Page 49: 8 Landing GearLanding Gear design f

Vendetta Final Proposal Part 1 (3.4 MB) - Cal Poly

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