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Proposed Revision to Advisory Circular (AC) 25.981-1B, Fuel Tank Ignition Source Prevention Guidelines

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Information about this document as published in the Federal Register.

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This document has been published in the Federal Register. Use the PDF linked in the document sidebar for the official electronic format.

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Federal Aviation Administration, DOT.


Notice of proposed revision to advisory circular.


The Federal Aviation Administration invites public comment on a proposed revision to Advisory Circular 25.981-1B, Fuel Tank Ignition Source Prevention Guidelines. The revision provides updated guidelines for demonstrating compliance with the certification requirements for preventing ignition sources within the fuel tanks of transport category airplanes.


Comments must be received on or before September 10, 2002.


You should send your comments on the proposed revision to the Federal Aviation Administration, Attention: Mike Dostert, Propulsion/Mechanical Systems Branch, ANM-112, Transport Directorate, Aircraft Certification Service, 1601 Lind Ave SW., Renton, WA 98055-4056. You may also submit comments electronically to:

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Mike Dostert at the above address, telephone (425) 227-2132, facsimile (425) 227-1320, or e-mail

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How Do I Obtain a Copy of the Proposed Advisory Circular Revision?

You may obtain an electronic copy of the draft advisory circular identified in this notice at the following Internet address:​certification/​aircraft/​air_​index.htm.

  • Click on “Advisory Circulars”;
  • At the bottom of the next page, click on “Related Links”;
  • On the next page, click on “Draft Advisory circulars”.
  • On the next page, click on “Open for Comment”.

If you do not have access to the Internet, you may request a copy by contacting Mike Dostert at the address or phone number listed earlier in this announcement.

How Do I Submit Comments on the Draft Advisory Circular?

You are invited to comment on the proposed advisory material by submitting written comments, data, or views. You must identify the title of the AC and submit your comments in duplicate to the address specified above. We will consider all comments received on or before the closing date for comments before issuing the final advisory material.


On May 7, 2002, the Federal Aviation Administration (FAA) published Amendment 25-102 to 14 CFR part 25 in the Federal Register (66 FR 23086). That amendment requires design approval holders of certain turbine-powered transport category airplanes to submit substantiation to the FAA that the design of the fuel tank system of previously certificated airplanes precludes the existence of ignition sources within the airplane fuel tanks. The rule also requires the affected design approval holders to develop specific fuel tank system maintenance Start Printed Page 40372and inspection instructions for any items in the fuel tank system that are determined to require repetitive inspections or maintenance, to assure the safety of the fuel tank system. In addition, the rule requires certain operators of those airplanes to incorporate FAA-approved fuel tank system maintenance and inspection instructions into their current maintenance or inspection program.

In addition to the rule changes adopted by amendment 25-102, the FAA also developed advisory material to supplement the rule changes. That advisory material was issued on April 18, 2001, as Advisory Circular (AC) 25.981-1B and AC 25.981-2. The FAA now announces the availability of a revised version of AC 25.981-1B for public comment.

The revised advisory material, AC 25.981-1C, provides guidance on how to substantiate that ignition sources will not be present in airplane fuel tank systems following failures or malfunctions of airplane components or systems. Also included is guidance for developing any limitations for the Instructions for Continued Airworthiness that may be generated by the fuel tank system safety assessment identified in amendment 25-102.

Since issuance of AC 25.981-1B, the FAA has received a number of comments and requests for additional guidance from users of the AC and has developed the revised AC to address these issues. Changes to the AC include:

  • Clarification of the definition of filament heating energy levels,
  • A new paragraph addressing electrostatics,
  • A new paragraph describing considerations for establishing minimum wire separation distances,
  • Discussion of use of silver inside fuel tanks,
  • Additional guidance regarding spaces adjacent to fuel tanks
  • New guidance on considerations for electrical bond redundancy, self bonding couplings, bond integrity checks, bond corrosion and integrity, and definition of major components.

In addition, several portions of the AC have been reorganized to present the material in a more useable form. Revised text is highlighted in yellow for ease in identifying changes from the previous version (AC 25.981-1B). You may also review the previous version at the Internet address provided earlier in this document under the heading, “How do I obtain a copy of the proposed advisory circular revision?”

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Issued in Renton, Washington, on May 30, 2002.

Vi L. Lipski,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

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[FR Doc. 02-14756 Filed 6-11-02; 8:45 am]