C.184.108.40.206 Selection and Characterization of Critical Missiles.
Since the aircraft categories and subcategories in Reference 1 are not based on
specific consideration of mass, stiffness, and velocity, which determine the impact force
time-history, selection of critical aircraft missiles should be based on an assessment of
all aircraft identified as potential missiles in the site-specific hazard study. However, if a
site-specific hazard study shows that aircraft of only certain categories or subcategories
are potential missiles, the critical missile selection should be based on these categories
or subcategories. If no site-specific hazard study is performed, critical missiles can be
selected based on generic aircraft properties given in References 1 and 2.
The use of impact kinetic energy as the sole parameter for selecting the critical missile
for evaluating global structural deformation is approximate. It assumes that even though
the peak force to which the target may be subjected depends on missile and target
mass, stiffness, and strength characteristics, the target damage potential is essentially
input energy-dependent since some ductility is permitted. However, if the kinetic
energies of the missiles are comparable but their stiffness and strength characteristics
are known to be significantly different, these differences should be considered.
References 1 and 2 provide impact velocity distributions for many aircraft subcategories
based on subcategory-specific crash data. If the site-specific hazard study identifies an
aircraft as a potential missile, and this aircraft belongs to one of the subcategories for
which an impact velocity distribution is available in References 1 or 2, this distribution
can be considered in establishing the impact velocity and selecting the critical missiles.
If the mass distribution of the aircraft along the length of the fuselage (Md) cannot be
obtained or calculated by any of the means outlined in Section 220.127.116.11, it can be
estimated as follows:
From published literature, obtain the mass distribution curve of a category or
subcategory of aircraft, the shape and configuration of which are similar to the