[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: 14CFR31.25]

[Page 728-729]
 
                     TITLE 14--AERONAUTICS AND SPACE
 
CHAPTER I--FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION
 
PART 31--AIRWORTHINESS STANDARDS: MANNED FREE BALLOONS--Table of Contents
 
                    Subpart C--Strength Requirements
 
Sec. 31.25  Factor of safety.

    (a) Except as specified in paragraphs (b) and (c) of this section, 
the factor of safety is 1.5.
    (b) A factor of safety of at least five must be used in envelope 
design. A reduced factor of safety of at least two may be used if it is 
shown that the selected factor will preclude failure due to creep or 
instantaneous rupture from lack of rip stoppers. The selected factor 
must be applied to the more critical of the maximum operating pressure 
or envelope stress.
    (c) A factor of safety of at least five must be used in the design 
of all fibrous or non-metallic parts of the rigging and related 
attachments of the envelope to basket, trapeze, or other means provided 
for carrying occupants.

[[Page 729]]

The primary attachments of the envelope to the basket, trapeze, or other 
means provided for carrying occupants must be designed so that failure 
is extremely remote or so that any single failure will not jeopardize 
safety of flight.
    (d) In applying factors of safety, the effect of temperature, and 
other operating characteristics, or both, that may affect strength of 
the balloon must be accounted for.
    (e) For design purposes, an occupant weight of at least 170 pounds 
must be assumed.

[Doc. No. 1437, 29 FR 8258, July 1, 1964, as amended by Amdt. 31-2, 30 
FR 3377, Mar. 13, 1965]