Section 10.1. Design Loads Spectrum
The design load spectrum is used to determine the damage growth
in each critical part during analysis and testing. It is based on the specified mission profile information and the
required aircraft life. A description
of the load sequence development is given in Section 5.3 of this handbook. A brief review is presented here. Giessler,
et al.  presents a detailed description of load sequence
The load sequence is composed of the load cycles that can be
expected to occur during the lifetime operation of the aircraft. They are the result of ground operations,
such as towing, taxiing, turning, braking, take-off and landing, and of
airborne operations of maneuvering, turbulence encounters, store ejection and
refueling. The specification documents
include the numbers of these loads to be anticipated at various levels during
the aircraft life.
The design spectrum must be based on a reasonable estimate of
the anticipated mission usage history.
All load sources should be included and the anticipated severity should
reflect on both previously observed data and on any performance advances being
designed into the new aircraft. It has
become somewhat of an axiom that the full maneuvering capability of the aircraft
will be used during its operation.
Thus, it is essential that the design load sequence be representative of
the aircraft capability. Figure 10.1.1 from Buntin  illustrates a basic
procedure for the development of a design loads spectrum. This is an interactive program involving
several different data sources and other design activities.
The design loads spectra usually progresses from a preliminary
effort based on the initial aerodynamics to a final form based on the final
aerodynamics and aircraft configuration.
10.1.1. A Procedure for Development
of Design Loads Spectra [Buntin, 1979]