Vendetta Final Proposal Part 2 - Cal Poly

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. Use of flight simulation and dynamic analysis tools are
utilized for these concerns.
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, a large yawing moment will be created if the
135,000 ft-lbs
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 at a takeoff speed of 1.2 times
the stall speed at sea level. In this configuration the Vendetta can
45,000 lbs off
center
maintain a 953 fpm climb at military power and 3,435 fpm at
maximum afterburning thrust. This performance is overkill, but is
Figure 10.4 - OEI Forces and Moments
driven by the RFP requirement for zero foot per second specific excess power at a load factor of two.
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 lb
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 V-tail was shown to be ill-advised. 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
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