Vendetta Final Proposal Part 2 - Cal Poly

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ehaviors and to adhere to MIL-8785C. It was calculated that the Vendetta’s fuselage forebody will destabilize the aircraft an additional 3.1% in subsonic cruise and 5.0% in supersonic cruise. The wing was placed to account for this. This is much improved over previous configurations where the fuselage destabilized the aircraft up to 16%. This is due to the fact that so fuselage with a large mean width was in front of the CG and NP. Figure 10.7 shows the Vendetta’s pitch break characteristics in the subsonic low speed and supercruise regimes given a CG location that would yield a statically stable aircraft. -0.6 Lift Coefficient (C L ) -0.4 UNSTABLE NEUTRAL -0.2 -0.25 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25 0 0.2 M = 0.2 M = 1.6 0.4 0.6 0.8 Moment Coefficient (C m ) Figure 10.7 - Pitch Break Characteristics This figure shows that as the Vendetta rotates and has some angle-of-attack in the low speed subsonic (Mach 0.2) regime, it will want to continue to rotate and break away. In the supercruise, the aircraft behaves much more linearly. The subsonic characteristics are of some concern, but even simple feedback schemes in the DFCS solve this problem. The supersonic characteristics are actually more desirable because the maneuvering required is very light and the control system will not be oscillating or fluttering the control surfaces, which creates unnecessary drag, to keep the aircraft flying straight. A full state-space based model for the aircraft driven by a Taylor expansion and fit into equations of motion was developed for flight simulator validation. These forms are too complex for simple dynamic analysis, so the literal factor forms of the dynamics modes were used to determine conformity with MIL-8785C. The literal factors are nothing more than simplifications of the transfer function forms for longitudinal and lateral modes of interest. These forms omit insensitive stability derivatives. The conformity with the military specifications for handling quality is shown in Table 10.IV. 54
Table 10.IV - Longitudinal and Lateral Dynamic Mode Conformity with MIL-8785C Damping ratio (ζ) Natural Frequency (ω n ) Mode Vendetta MIL-8785C Vendetta MIL-8785C MIL-8785C Level Phugoid 0.094 > 0.04 0.091 - I Short Period 0.921 0.35 – 1.3 4.721 - I Dutch Roll 0.103 > 0.08 1.960 > 0.4 I Table 10.IV shows that the Vendetta satisfies all of the military specifications for these three important modes while in a subsonic cruise with the CG monitor. The only thing of concern regarding these results is high value for undamped natural frequency in the Dutch Roll mode. It is not uncommon for aircraft of this size and type to incorporate fairly simple yaw dampers operating on the yaw rate. With the use of the DFCS, the Vendetta has no problem keeping that mode in control. Because there is a large amount of robustness available with CG excursion and the DFCS, the longitudinal modes are well within the Type I military specifications and remain there in the supercruise. From inertia computations illustrated in the weights and balance section (Section 7), it became apparent that the Vendetta has a very small inertia that would need to be overcome to roll. This is due to the wings being the only significant structure located off the centerline. This makes for very favorable roll damping and allows for the flaperon and aileron configurations to be driven by the sizes required for high lift augmentation as presented in the aerodynamics section. The final sizes and parameters for the empennage and roll control are presented in Table 10.V. Table 10.V – Empennage Surfaces Surface Area (ft 2 ) Control Surface Horizontal Stabilator 270.0 Full-Flying Vertical Stabilizer 165.0 Rudder @ 27% m.a.c. 10.1 Simulation Validation of a large supersonic aircraft like Vendetta is difficult due to limitations in experimental tools. Subsonic wind tunnel models would be limited to testing takeoff and landing aerodynamics and would be inaccurate due to Reynolds number discrepancies. Because of this, flight simulation was utilized to test the design of the aircraft. The Cal Poly Flight Simulator was used to evaluate handling qualities, ground handling, up-and-away tasks, and low speed performance. The flight simulator consists of a flight cab and instrument panel as shown in Figure 10.8 and Figure 10.9. 55
Page 1 and 2: well as a tip back angle which did
Page 3 and 4: Table 9.II - Final Component Weight
Page 5 and 6: the center-of-gravity location clos
Page 7 and 8: 10 Stability and Control To initial
Page 9 and 10: management system could then be use
Page 11 and 12: 40 30 20 10 0 -10 -20 -30 -40 -50 2
Page 13: flight. This would require a large
Page 17 and 18: Additional components were integrat
Page 19 and 20: 11 Performance 11.1 Specific Excess
Page 21 and 22: 70,000 60,000 50,000 Altitude (ft)
Page 23 and 24: 11.3 Mission Requirements The RFP d
Page 25 and 26: 11.4 Takeoff & Landing The RFP requ
Page 27 and 28: 12 Payload Weapon internal layout w
Page 29 and 30: ange occurs due to the additional w
Page 31 and 32: 13 Cockpit Cockpit design began wit
Page 33 and 34: Due to RFP requirements the majorit
Page 35 and 36: fuelled systems offer high power to
Page 37 and 38: 14.4 Government Furnished Equipment
Page 39 and 40: The assembly line would allow for m
Page 41 and 42: is a learning curve associated with
Page 43 and 44: Table 17.I - RFP Compliance Checkli
Page 45 and 46: 20,000 0.9 581 2,164 3,231 4,407 5,
Page 47 and 48: Appendix B - Design Tools Company S
Page 49: 25. Roskam, J. Airplane Flight Dyna

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