SAWE Report - Cal Poly San Luis Obispo

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5.2 Wing Planform The next aspect of the wing that was considered was the leading and trailing edge sweep angles. Because any edges on an aircraft reflect radar energy, the sweep angles of the edges of the wing were chosen to minimize radar energy reflected back to the source, especially in the frontal aspect of the aircraft where a specific RCS requirement is given by the RFP. To avoid reflecting radar toward the front of the aircraft, the leading and trailing edges of the wing had to be highly swept. In addition, the sweep angles could not be approximately 45º because a corner reflector would be created. These requirements led to a diamond shaped wing planform with leading and trailing edge wing sweeps of approximately 40º. Two initial designs were considered one having a 40º swept leading edge and a 30º forward swept trailing edge and the other having matched 35.3º leading edge and trailing edge sweeps. A trade study was performed to select between these two wing configurations by studying the effect of the two configurations on RCS and aerodynamics. Figure 5.2 shows a comparison of radial sweeps of both configurations using RadBase2. The return from the 40º and 35.3º leading edge sweeps can be clearly seen in the plot. The leading edge spike on the matched leading and trailing edge configuration is approximately 15 dB lower than the other configuration; however it is 5º closer to the frontal aspect of the aircraft. The aerodynamic study of the two wing configurations indicated that approximately 1,000 lb (454 kg) of additional fuel would be required due to the additional wave drag of the lower leading edge sweep angle. Because of the aerodynamic benefits and because the RFP only gives frontal aspect RCS requirements, the 40º leading edge and 30º trailing edge configuration was chosen. 23
1 GHz. 40º LE Sweep 10 GHz. 40º LE Sweep 1 GHz. 35.3º LE Sweep 10 GHz. 35.3º LE Sweep RFP Requirement (-12 dB) 50 dB 40 dB 30 dB 20 dB 10 dB 35.3º LE Sweep 40º LE Sweep 0 dB -10 dB -20 dB -30 dB -40 dB -50 dB Figure 5.2 - Effect of Wing Leading and Trailing Edge Sweep on Aircraft RCS Once the wing area, aspect ratio, and sweep angles were chosen, the tip chord was kept at 8 ft (2.4 m) to avoid an overly small tip chord that could interact with radar wavelengths unpredictably. This resulted in the wing planform shown in Figure 5.3, with the measurements given in Table 5.I. Leading and trailing edge flaps, and ailerons were added to the wing. The chord high lift devices and control surfaces were kept at a constant percentage of the mean aerodynamic chord so that the hinge lines would parallel to the wing edges. The trailing edge flap chord is 20% of the mean aerodynamic chord and the leading edge flap and aileron are each 10% of the mean aerodynamic chord. The trailing edge flap extends from the fuselage to 65% of the semi-span, the leading edge flap extends from the fuselage to 90% of the semi-span, and the aileron extends from the edge of the flap to 90% of the semi-span. No moveable surfaces were added to the last 10% of the semi-span so that radar obsorbing materials (RAM) could be added in the wing tip to minimize any returns from that edge. 24
Page 1 and 2: SAWE Paper No. 3232 Category No. 10
Page 3 and 4: Table of Contents Abstract_________
Page 5 and 6: List of Figures Figure 1.1 - Design
Page 7 and 8: Figure 13.4 - Rectilinear Vision Pl
Page 9 and 10: Nomenclature AIAA American Institut
Page 11 and 12: α Angle of Attack, degrees, rad.
Page 13 and 14: Table 1.II - Summary of Design Requ
Page 15 and 16: Figure 1.3 - F-15 Strike Eagle F-11
Page 17 and 18: Table 1.III - Comparison of the F-1
Page 19 and 20: Many of the equations buried in the
Page 21 and 22: 3 Configuration The current configu
Page 23 and 24: Another problem arises from the 20
Page 25 and 26: • Span = 54.7 ft • m.a.c. = 32
Page 27 and 28: 4 Stealth Considerations As mention
Page 29 and 30: Table 4.I - Common Ground Radars Ra
Page 31 and 32: 30 20 10 0 -10 -20 -30 -40 -50 1 GH
Page 33: 5 Aerodynamics The major aerodynami
Page 37 and 38: 5.3 Wing Thickness The effect of wi
Page 39 and 40: 5.4 Airfoil The NACA 65A-003 airfoi
Page 41 and 42: 1 Section Lift Coefficient 0.9 0.8
Page 43 and 44: 90 80 Wing Cross Sectional Area (ft
Page 45 and 46: 6 Propulsion In developing the prop
Page 47 and 48: Table 6.II - RFP Dimensions Compare
Page 49 and 50: 38 Figure 6.1 - VAATE Goals
Page 51 and 52: TSFC 3.0 2.8 2.6 2.4 2.2 2.0 1.8 1.
Page 53 and 54: Deflection Angle Analysis for Mach
Page 55 and 56: Figure 6.8 - Cost Association with
Page 57 and 58: The inlet has a boundary layer dive
Page 59 and 60: 7 Materials and Structure The overa
Page 61 and 62: Vertical Attachment Points Horizont
Page 63 and 64: 8 Landing Gear Landing Gear design
Page 65 and 66: steel. This means that more braking
Page 67 and 68: Table 9.II - Final Component Weight
Page 69 and 70: throughout the 5-hour mission. Usin
Page 71 and 72: 10 Stability and Control To initial
Page 73 and 74: difference in neutral point and cen
Page 75 and 76: 40 30 20 10 0 -10 -20 -30 -40 -50 2
Page 77 and 78: The Vendetta configuration utilizes
Page 79 and 80: -0.6 -0.4 UNSTABLE NEUTRAL -0.2 Lif
Page 81 and 82: Validation of an aircraft design su
Page 83 and 84: consumption. The main aspects of th
Page 85 and 86:
In addition to the performance requ
Page 87 and 88:
70,000 Altitude (ft) 60,000 50,000
Page 89 and 90:
11.4 Mission Requirements By comple
Page 91 and 92:
Table 11.VIII - Landing Flight Prof
Page 93 and 94:
11.7 Alternate Missions In addition
Page 95 and 96:
12 Payload Weapon internal layout d
Page 97 and 98:
13 Cockpit Cockpit Design began wit
Page 99 and 100:
that could be used in landing and t
Page 101 and 102:
14 Systems The systems of the Vende
Page 103 and 104:
14.3 Fuel System Initial fuel syste
Page 105 and 106:
15 Manufacturing Several manufactur
Page 107 and 108:
16 Cost Analysis The final and perh
Page 109 and 110:
Appendix Threats Chart Common Surfa
Page 111 and 112:
Wing Break Point Fuel Aft Fuselage
Page 113 and 114:
The Vendetta Design Team Chris Atki
Page 115 and 116:
References 1. “Ejection Systems,
Page 117:
35. www.dfrc.nasa.gov/PAO/PAIS/HTML
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