SAWE Report - Cal Poly San Luis Obispo

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The extra 10° cant resulted in a substantially larger pitch coupling term. In addition to the complications of canting more, a 30° angle would mean that a more complex mixer and control system would be required. This would add to the cost and is avoided. It is important to note that the previous static methods do not take into account the dynamic characteristics or modes of this aircraft. With such a large amount of the fuselage in front of the center of pressure, the Vendetta may require a complex yaw damper or larger vertical to compensate. The size of the vertical could potentially be driven by the one engine inoperative (OEI) control power requirements. Because the engine nozzle centerlines are mounted considerably offset from the centerline at 3 feet (0.9144 m), a large yawing moment will be created if the Vendetta loses an engine during takeoff. The engines produce roughly 45,000 pounds of thrust and would generate a 135,000 foot-pound moment. Table 10.III shows the results of the rudder control power analysis for this critical OEI condition. Table 10.III - Rudder Control Power Results for OEI Condition PARAMETER NOTATION VALUE Side Force due to Rudder C yδr 0.0105 Rolling Moment due to Rudder C lδr 0.0072 Rudder Effectiveness C nδr -0.0070 OEI Critical Yawing Moment 135,000 ft-lbs Rudder Deflection Required in OEI Condition at Takeoff 13.6° With a rudder effectiveness of -0.0070 (1/deg), a 13.6° rudder deflection is required to keep the aircraft flying straight in the OEI condition on takeoff. This is not too large, and would suffice by allowing approximately another 10° of rudder deflection for the pilot to yaw the aircraft beyond the straight condition for controllability. In this condition, the aircraft would be susceptible to large amounts of sideslip, β. This rudder deflection would be substantially higher if a higher cant angle were used. In these critical situations where the aircraft is in danger, the added drag created by the mixing is desired to be as little as possible. A separate 4 surface empennage was now made necessary because going to a purely V-tail was shown to be ill-advised at this stage because of the aforementioned studies. If a pure v-tail was chosen, it would have to be full-flying due to the demand placed on the surface and hinge lines in supersonic flight. This would require a large actuator and large structural members in the aft portion of the aircraft. This would considerably drive the configuration away from initial RCSfriendly layouts as well as increasing complexity and cost. 65
The Vendetta configuration utilizes a 20° cant on the verticals and a separate full-flying horizontal as seen in Figure 10.5. It was mentioned earlier that one of the reasons the horizontal tail volume coefficient was larger in the historical aircraft was because those aircraft did not utilize control augmentation systems or digital fly-by-wire control systems. Not only did they have to account for wide shifts in CG, they also had to combat the muck tuck problem associated with breaking the sound barrier. Figure 10.5 - Vendetta Empennage Configuration Figure 10.6 shows that as the aircraft Mach trim exceeds the critical Mach number, the center of pressure of the wing and other control surfaces travels aft. In the case of the Vendetta, this leaves the CG an extra 12% m.a.c. in front of the neutral point; this makes it 12% more stable. This 12% shift was calculated with the Air Force’s Data Compendium (DATCOM) mg 12% m.a.c. methods. Figure 10.6 - Mach Tuck Illustrated The shift in the neutral point of the wing means that the horizontal would have to deflect to keep the Vendetta from “tucking” under. The trim drag created could be avoided by shifting the CG, by altering the neutral point, or designing the aircraft to be unstable subsonic and stable supersonic. The use of a trim tank was investigated to pump fuel aft and shift the CG closer to the neutral point in supersonic cruise. This notion was dismissed because the tank would be a vacant waste of space and would complicate ground procedures where refueling would have to leave the tank vacant. The use of an extra flying surface such as a canard could be used as well. The canard would destabilize the aircraft by moving the neutral point forward and closer to the CG but it would make the Vendetta even more uncontrollable in the subsonic landing and takeoff conditions. This extra control surface would add to the cost and complexity. A fuel management system could be used to burn fuel from certain tanks to keep the CG travel in check. After analyzing the abrupt shift in the neutral point when the Vendetta climbs to its cruise condition, it was decided that the fuel management system could not pump fuel fast enough to 66
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 and 34: 5 Aerodynamics The major aerodynami
Page 35 and 36: 1 GHz. 40º LE Sweep 10 GHz. 40º L
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: 40 30 20 10 0 -10 -20 -30 -40 -50 2
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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