Vendetta Final Proposal Part 2 - Cal Poly

9 Weight & Balance
Weight and balance has proven to be a challenge in designing the Vendetta for both subsonic and supersonic
flight conditions. After having sized the aircraft using a weight fraction method, and after having developed an initial
configuration, the next step was to develop a more accurate, class II weight buildup of the aircraft. The class II method
used in the design of the Vendetta was developed from those methods found in the Nicolai, Raymer, and Roskam texts in
order to obtain a collaborative and unbiased perspective. These methods involved defining several physical and
geometric parameters of the aircraft. These parameters were inputs into a series of equations developed from historical
weight trends. The weight estimations for various components as well as the level of agreement between authors are
shown below in Table 9.I.
Table 9.I - Initial Component Weight Buildup
Weight (lb)
Accuracy
Component Roskam Nicolai Raymer Average Roskam Nicolai Raymer
Structures
Wing Group 9,687 11,466 7,870 9,674 0% -31% 26%
Horizontal Tail 1,135 1,694 958 1,262 14% -62% 32%
Vertical Tail 801 1,538 1,497 1,279 47% -34% -28%
Fuselage 10,681 16,031 10,398 12,370 19% -52% 22%
Main Landing Gear 2,742 2,969 1,156 2,289 -33% -52% 60%
Nose Landing Gear 387 405 408 400 5% -2% -3%
Propulsions 10,636 10,878 11,199 11,209 4% 0% -4%
Systems 18,649 14,506 14,350 20,574 -29% 12% 13%
Payload 9,280 9,280 9,280 9,280 0% 0% 0%
Fuel 58,974 58,974 58,974 58,974 0% 0% 0%
TOGW 123,433 128,215 128,215 127,778 4% -2% -2%
The detailed weight buildup of the structures, control surfaces, systems, payload, and fuel groups has been
compacted in order to save space and can be viewed in its entirety in Foldout 1. The table indicates that all three authors
tend to disagree to some extent in their weight estimates of certain components, and for other components, one author
may have no way of estimating that components weight at all. A more accurate and detailed component weight buildup
was developed by considering all three methods and taking the average shared between them. One author’s estimation
was discarded if it did not agree to within ±30% of the average of the other authors’ estimations. The remaining weights
were averaged in order to develop a weight buildup for the entire aircraft. The class II weight buildup for the Vendetta
after the elimination process is shown in Table 9.II
42