Document headings vary by document type but may contain the following:
See the Document Drafting Handbook for more details.
AGENCY:
Federal Aviation Administration (FAA), DOT.
ACTION:
Final rule.
SUMMARY:
The FAA is adopting a new airworthiness directive (AD) for certain The Boeing Company Model 747-400F series airplanes. This AD was prompted by a report that cap seals were not applied to certain fasteners in the fuel tanks during production. This AD requires applying cap seals to certain fastener collars inside the fuel tanks. The FAA is issuing this AD to address the unsafe condition on these products.
DATES:
This AD is effective October 21, 2024.
The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of October 21, 2024.
ADDRESSES:
AD Docket: You may examine the AD docket at regulations.gov under Docket No. FAA-2024-1000; or in person at Docket Operations between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this final rule, any comments received, and other information. The address for Docket Operations is U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.
Material Incorporated by Reference:
- For Boeing material identified in this AD, contact Boeing Commercial Airplanes, Attention: Contractual & Data Services (C&DS), 2600 Westminster Boulevard, MC 110-SK57, Seal Beach, CA 90740-5600; telephone 562-797-1717; websitemyboeingfleet.com.
- You may view this material at the FAA, Airworthiness Products Section, Operational Safety Branch, 2200 South 216th Street, Des Moines, WA. For information on the availability of this material at the FAA, call 206-231-3195. It is also available atregulations.gov under Docket No. FAA-2024-1000.
FOR FURTHER INFORMATION CONTACT:
Samuel Dorsey, Aviation Safety Engineer, FAA, 2200 South 216th Street, Des Moines, WA 98198; telephone 206-231-3415; email samuel.j.dorsey@faa.gov.
SUPPLEMENTARY INFORMATION:
Background
The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain The Boeing Company Model 747-400F series airplanes. The NPRM published in the Federal Register on April 12, 2024 (89 FR 25823). The NPRM was prompted by a report indicating that cap seals were not applied to certain fasteners in the fuel tank during production. The FAA issued AD 2022-10-11, Amendment 39-22049 (87 FR 34120, June 6, 2022) to require, among other actions, application of cap seals to certain fasteners in the fuel tank on airplanes having line numbers 645 through 1363 inclusive. Cap seals were determined to be a necessary feature by SFAR 88 reviews and were required to be retrofitted onto existing airplanes by AD 2022-10-11 and earlier ADs. Boeing intended to incorporate similar changes on future airplanes, ultimately those having line numbers 1364 through 1419 inclusive, via a production design change. However, Boeing discovered that the design change omitted application of the cap seals on eight fasteners (four each on the left and right wings in the inboard main fuel tanks). Without these cap seals, the ends of the fasteners do not have sufficient electrical insulation to prevent arcing in the event of a lightning strike or high-powered short circuit, possibly creating an ignition source in the inboard main fuel tanks. A failure to prevent possible ignition sources in the fuel tank, in combination with flammable fuel vapors, could result in an explosion or fire and consequent loss of the airplane. In the NPRM, the FAA proposed to require applying cap seals to certain fastener collars inside the fuel tanks. The FAA is issuing this AD to address the unsafe condition on these products.
Discussion of Final Airworthiness Directive
Comments
The FAA received comments from Air Line Pilots Association, International (ALPA) and an individual who supported the NPRM without change. The FAA also received an additional four comments from individuals who had no objection to the NPRM. One commenter expressed concern about the effect on safety of certain internal Boeing practices. This comment is outside the scope of the NPRM.
The FAA received an additional comment from Boeing. The following presents that comment and the FAA's response.
Request for Clarification of Sealant Part Number
Boeing requested an exception be added to paragraph (h) of the proposed AD to correct an incorrect part number listed in the service bulletin for the sealant. Boeing Alert Requirements Bulletin 747-57A2371 RB, dated September 29, 2023, inadvertently specifies the application of sealant Boeing Material Specification (BMS) 5-45, CLASS B-2, GRADE 1, for certain required actions. GRADE 1 does not apply to the specification noted. Boeing informed customers of this typographical error via Information Notice 747-57A2371 IN-01 dated May 20, 2024.
The FAA agrees and has added an exception in paragraph (h)(2) of this AD to correct the typographical error. As stated by Boeing, Class B BMS 5-45 sealant does not have an additional grade identifier. Only Class A BMS 5-45 sealant possesses a grade identifier.
Conclusion
The FAA reviewed the relevant data, considered any comments received, and determined that air safety requires adopting this AD as proposed. Accordingly, the FAA is issuing this AD to address the unsafe condition on these products. Except for minor editorial changes, and any other changes described previously, this AD is adopted as proposed in the NPRM. None of the changes will increase the economic burden on any operator.
Material Incorporated by Reference Under 1 CFR Part 51
The FAA reviewed Boeing Alert Requirements Bulletin 747-57A2371 RB, dated September 29, 2023. This material specifies procedures for applying cap seals to four fastener collars inside the fuel tank common to the stiffeners located at the front spar on the left and right wings. This material is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section.
Costs of Compliance
The FAA estimates that this AD affects 15 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD:
Estimated Costs
| Action | Labor cost | Parts cost | Cost per product | Cost on U.S. operators |
|---|---|---|---|---|
| Apply cap seals | 37 work-hours × $85 per hour = $3,145 | $1,000 | $4,145 | $62,175 |