[Code of Federal Regulations]

[Title 14, Volume 1]

[Revised as of January 1, 2006]

From the U.S. Government Printing Office via GPO Access

[CITE: 14CFR25.305]



[Page 369-370]

 

                     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



[[Page 370]]



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]