The Code of Federal Regulations (CFR) annual edition is the codification of the general and permanent rules published in the Federal Register by the departments and agencies of the Federal Government produced by the Office of the Federal Register (OFR) and the Government Publishing Office.
Download the Code of Federal Regulations in XML.
Parallel Table of Authorities and Rules for the Code of Federal Regulations and the United States Code
Text | PDF
Find, review, and submit comments on Federal rules that are open for comment and published in the Federal Register using Regulations.gov.
Purchase individual CFR titles from the U.S. Government Online Bookstore.
Find issues of the CFR (including issues prior to 1996) at a local Federal depository library.
Electronic Code of Federal Regulations
Title 14: Aeronautics and Space
§23.959 Unusable fuel supply.
(a) The unusable fuel supply for each tank must be established as not less than that quantity at which the first evidence of malfunctioning occurs under the most adverse fuel feed condition occurring under each intended operation and flight maneuver involving that tank. Fuel system component failures need not be considered.
(b) The effect on the usable fuel quantity as a result of a failure of any pump shall be determined.
[Amdt. 23-7, 34 FR 13093, Aug. 13, 1969, as amended by Amdt. 23-18, 42 FR 15041, Mar. 17, 1977; Amdt. 23-51, 61 FR 5136, Feb. 9, 1996]