[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: 14CFR25.305]

[Page 363]
 
                     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. 25.305  Strength and deformation.

    (a) The structure must be able to support limit loads without 
detrimental permanent deformation. At any load up to limit loads, the 
deformation may not interfere with safe operation.
    (b) The structure must be able to support ultimate loads without 
failure for at least 3 seconds. However, when proof of strength is shown 
by dynamic tests simulating actual load conditions, the 3-second limit 
does not apply. Static tests conducted to ultimate load must include the 
ultimate deflections and ultimate deformation induced by the loading. 
When analytical methods are used to show compliance with the ultimate 
load strength requirements, it must be shown that--
    (1) The effects of deformation are not significant;
    (2) The deformations involved are fully accounted for in the 
analysis; or
    (3) The methods and assumptions used are sufficient to cover the 
effects of these deformations.
    (c) Where structural flexibility is such that any rate of load 
application likely to occur in the operating conditions might produce 
transient stresses appreciably higher than those corresponding to static 
loads, the effects of this rate of application must be considered.
    (d) [Reserved]
    (e) The airplane must be designed to withstand any vibration and 
buffeting that might occur in any likely operating condition up to 
VD/MD, including stall and probable inadvertent 
excursions beyond the boundaries of the buffet onset envelope. This must 
be shown by analysis, flight tests, or other tests found necessary by 
the Administrator.
    (f) Unless shown to be extremely improbable, the airplane must be 
designed to withstand any forced structural vibration resulting from any 
failure, malfunction or adverse condition in the flight control system. 
These must be considered limit loads and must be investigated at 
airspeeds up to VC/MC.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-23, 
35 FR 5672, Apr. 8, 1970; Amdt. 25-54, 45 FR 60172, Sept. 11, 1980; 
Amdt. 25-77, 57 FR 28949, June 29, 1992; Amdt. 25-86, 61 FR 5220, Feb. 
9, 1996]

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