Standard Methods for Aerospace Stress Analysis

6Aircraft Load Cases

6.1 Introduction to Load Cases

Structural loads analysis criteria to determine the loads acting on the aircraft structure due to flight maneuvers, flight turbulence, landing, ground handling, water, and pressurization are discussed in this chapter. These analysis criteria help to develop the design load conditions, fail‐safe load conditions, fatigue load conditions, and operating load conditions.

6.2 Aviation Loads Regulations

Per 25.301 Loads,

1. Strength requirements are specified in terms of limit loads (the maximum loads to be expected in service) and ultimate loads (limit loads multiplied by prescribed factors of safety). Unless otherwise provided, prescribed loads are limit loads.
2. Unless otherwise provided, the specified air, ground, and water loads must be placed in equilibrium with inertia forces, considering each item of mass in the airplane. These loads must be distributed to conservatively approximate or closely represent actual conditions. Methods used to determine load intensities and distribution must be validated by flight load measurement unless the methods used for determining those loading conditions are shown to be reliable.
3. If deflections under load would significantly change the distribution of external or internal loads, this redistribution must be taken into account.

6.3 Limit and Ultimate Load Cases

Design limit loads are defined as the loads the aircraft structure would see and must withstand per design for the duration of the ...