【正文】 18 Miscellaneous Sizing Considerations Takeoff Rotation Angle From the threedimensional CMARC analysis, described below, it was determined that an angle of 15176。 the other varied the wing loading. This made it possible to plot a curve of GTOW vs. wing loading for each aspect ratio. Using this for loop approach allowed the team to rapidly generate numerous data points which (with a small enough wing loading increment) could be linearly connected to adjacent points to form a smooth curve. Team V。 5 Design Requirements The current design requirements shown below in Table 1 are still the same as presented in this team’s System Definition Review [13]. Through the work presented in this report, it will be shown that at the current level of detail an alternatefueled aircraft can meet all the given requirements. Table 1 Design Requirements Design Requirements Summary ≤1500 ft takeoff distance to clear a 50 ft obstacle ≥600 lb payload with max fuel ≥125 kts max cruise speed, Target = 150 kts ≥500 nm range, Target = 600 nm ≥48x44 cabin height x width Target GTOW of 2800 lbs Target base price of $300,000 Team V。 3 Table of Contents Introduction ................................................................................................................................... 4 Design Requirements .................................................................................................................... 5 Proposed Concept ......................................................................................................................... 6 Design Mission............................................................................................................................... 7 Sizing .............................................................................................................................................. 8 2D Aerodynamics ........................................................................................................................ 19 3D Aerodynamics ........................................................................................................................ 24 Performance ................................................................................................................................ 31 Structures..................................................................................................................................... 35 Weight and Balance amp。 9 G TO WWT p???? 550200 Equation 4 where ηp is the propeller efficiency, which is assumed to be based upon the propeller analysis discussed later. The SFC was calculated from the brake horsepower SFC (BSFC) which was calculated for the aircraft’s engine to be . Engine selection and SFC calculation is discussed later in this report. The equation used to calculate SFC from BSFC is: pVB S F CS F C ???? 550 Equation 5 where V is speed and ηp is the propeller efficiency. 12WW corresponds to the fuel used during takeoff and is also calculated using Equation 3 with 100% thrust. Duration for the takeoff segment is assumed to be one minute as specified in Raymer’s chapter 19 [10]. 23WW represents the fuel weight used in climbing to the cruise altitude of 8000 ft. It is calculated using Raymer’s equation : ?????????????????? ??????TDVhCWW eii1e xp1 Equation 6 where C is SFC (same as previously discussed), Δhe is the change in height energy, V is the average climb speed and D/T is the average drag divided by the average thrust during climb. It should be noted, however, that D/T is not actually calculated within the code, and is instead replaced by: 1??????? ?? WTDLTD Equation 7 In Equation 7, L/D is calculated implicitly by calculating CL/CD. CL is calculated using the equation: 221 VS WqSWC L ?? ???? ? Equation 8 where W/S is wing loading (an input parameter) and ρ is air density at sea level. CD is calculated using the curve fit for the plane’s drag polar: 0 2 0 7 2 ????? LLD CCC Equation 9 Δhe is calculated using Raymer’s equation : Team V。 16 It can be seen in Figure 3 that the lowest GTOW is approximately 2610 lbs which corresponds to a wing loading of lbs/sq ft and an aspect ratio of approximately . For the final design, Team V chose to use a wing loading of and an aspect ratio of to allow room for error. Also note that in Figure 3 the climb constraint plotted is for a climb rate of 1350 fpm, not the 700 fpm climb rate used for the design mission. This was done so that the climb constraint would appear on the carpet plot, as 700 fpm was too far to the left. Plugging this wing loading and aspect ratio back into the sizing/carpet plot code gave the final sizing numbers. These can be seen in Table 3. It should be noted that our 75% power cruise speed is not our designed cruise speed, thus the power required to fly at 150 kts during cruise was calculated to be approximately 61% using Equation 16 above. Team V。 19 2D Aerodynamics In order to improve the performance of the aircraft, it was suggested that a new laminar flow airfoil be designed specifically for the Barn Owl. The goal of the design is to use optimization methods to create an airfoil that has lower drag during cruise than the NACA fourdigit series airfoils used on some GA aircraft, while simultaneously maintaining good performance at high angles of attack and under fully turbulent conditions. Methodology The optimization procedure is shown in Figure 7 as a flow chart. First, the Matlab optimizer generates a vector of design variables with information regarding the xy location of control (or “handle”) points the airfoil’s surface needs to pass through, as well as the tangency and curvature at the tr