Vendetta Final Proposal Part 2 - Cal Poly

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.
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