[Code of Federal Regulations]
[Title 14, Volume 1]
[Revised as of January 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 14CFR25.321]

[Page 364]
 
                     TITLE 14--AERONAUTICS AND SPACE
 
CHAPTER I--FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION
 
PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES--Table of Contents
 
                          Subpart C--Structure
 
Sec. 25.321  General.

    (a) Flight load factors represent the ratio of the aerodynamic force 
component (acting normal to the assumed longitudinal axis of the 
airplane) to the weight of the airplane. A positive load factor is one 
in which the aerodynamic force acts upward with respect to the airplane.
    (b) Considering compressibility effects at each speed, compliance 
with the flight load requirements of this subpart must be shown--
    (1) At each critical altitude within the range of altitudes selected 
by the applicant;
    (2) At each weight from the design minimum weight to the design 
maximum weight appropriate to each particular flight load condition; and
    (3) For each required altitude and weight, for any practicable 
distribution of disposable load within the operating limitations 
recorded in the Airplane Flight Manual.
    (c) Enough points on and within the boundaries of the design 
envelope must be investigated to ensure that the maximum load for each 
part of the airplane structure is obtained.
    (d) The significant forces acting on the airplane must be placed in 
equilibrium in a rational or conservative manner. The linear inertia 
forces must be considered in equilibrium with the thrust and all 
aerodynamic loads, while the angular (pitching) inertia forces must be 
considered in equilibrium with thrust and all aerodynamic moments, 
including moments due to loads on components such as tail surfaces and 
nacelles. Critical thrust values in the range from zero to maximum 
continuous thrust must be considered.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-23, 
35 FR 5672, Apr. 8, 1970; Amdt. 25-86, 61 FR 5220, Feb. 9, 1996]

                   Flight Maneuver and Gust Conditions