242 Aircraft Weight and Center of Gravity Estimation

ksp = 1.001 for a spoiler

kwl = 1.002 for a winglet (a generalized approach for a standard size)

kre = 1 for no engine, 0.98 for two engines, and 0.95 for four engines (generalized)

If nonmetal is used, then mass changes by the factor of usage. For example, x% mass is nonmetal that is y% lighter, the component mass would be as follows:

In a simpler form, if there is reduction in mass due to lighter material, then mass is reduced by that factor. If there is a 10% mass saving, then:

8.10.3 Empennage Group – Civil Aircraft

H- and V-tails also are lifting surfaces and use semi-empirical equations similar to those used for the wing. The empennage does not have an engine or undercarriage installation. It may carry fuel, but in this book, fuel is not stored in the empennage. The drivers are the same as those in the wing group mass.

Equation 8.20 is modified to suit the empennage mass estimation. Both the H- tail and V-tail plane mass estimations have a similar form but they differ in the values of constants used.

MEMPcivil = 0.0213 × (MTOM × nult)0.48 × SW0.78 × AR × (1 + λ)0.4/(Cos × t/c0.4) (8.23)

If nonmetals are used, then mass changes by the factor of usage. For example, x% mass is nonmetal that is y% lighter, the component mass would be as follows:

In a simpler form, if there is reduction in mass due to lighter material, then the mass is reduced by that factor. If there is a 10% mass saving, then:

Writing the modified equations in terms of this book’s nomenclature, Equation 8.23 is changed to the empennage for an H-tail and a V-tail as follows. For all H-tail movement, use kconf = 1.05; otherwise, 1.0.

For V-tail configurations, use kconf = 1.1 for a T-tail, 1.05 for a midtail, and 1.0 for a low tail.