# AD 2008-05-06: Longitudinal floor beam web - Type: Airworthiness directive - Status: Historical - Products: Boeing 737-100 Series, 737-200 Series, 737-300 Series, 737-400 Series and 737-500 Series - Effective: April 8, 2008 - Published: March 4, 2008, 73 FR 11538–11539 - Issued: February 20, 2008 - Issued as: Final rule - Superseded by: [AD 2016-13-11](https://openairdocs.org/ad/2016-13-11) - Product type: Aircraft, Large airplane - Amendment: 39-15400 - Docket: FAA-2007-0224 (https://www.regulations.gov/docket/FAA-2007-0224) - Project: 2007-NM-188-AD - Registered aircraft: 48 may be affected, by airframe or engine model (OpenAirDocs) - Official PDF: https://openairdocs.org/files/sha256/8d/94/8d946f6d9ca981652cc80172fe1128893ab5ad985fa318161063a1e6313cd503 (from https://www.govinfo.gov/content/pkg/FR-2008-03-04/pdf/E8-3810.pdf) - Federal Register: https://www.federalregister.gov/documents/2008/03/04/E8-3810/airworthiness-directives-boeing-model-737-100--200--300--400-and--500-series-airplanes - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/F41B3C1B7F0334ED86257402005558EB.0001 - DRS record last changed: August 7, 2025 - Page: https://openairdocs.org/ad/2008-05-06 ## Summary We are adopting a new airworthiness directive (AD) for certain Boeing Model 737-100, -200, -300, -400, and -500 series airplanes. This AD requires repetitive inspections for fatigue cracking in the longitudinal floor beam web, upper chord, and lower chord located at certain body stations, and repair if necessary. This AD results from several reports of cracks in the center wing box longitudinal floor beams, upper chord, and lower chord. We are issuing this AD to detect and correct fatigue cracking of the upper and lower chords and web of the longitudinal floor beams, which could result in rapid loss of cabin pressure. ## The airworthiness directive ### Adoption of the Amendment Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows: 1. The authority citation for part 39 continues to read as follows: 2. The FAA amends § 39.13 by adding the following new AD: 2008-05-06 Boeing: Amendment 39-15400. Docket No. FAA-2007-0224; Directorate Identifier 2007-NM-188-AD. ### (a) Effective Date (a) This airworthiness directive (AD) is effective April 8, 2008. ### (b) Affected ADs (b) None. ### (c) Applicability (c) This AD applies to Boeing Model 737-100, -200, -300, -400, and -500 series airplanes, certificated in any category; as identified in Boeing Service Bulletin 737-57-1296, dated June 13, 2007. ### (d) Unsafe Condition (d) This AD results from several reports of cracks in the center wing box longitudinal floor beams, upper chord, and lower chord. We are issuing this AD to detect and correct fatigue cracking of the upper and lower chords and web of the longitudinal floor beams, which could result in rapid loss of cabin pressure. ### (e) Compliance (e) You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done. ### (f) Repetitive Inspections (f) Do the various inspections for fatigue cracks in the longitudinal floor beam web, upper chord, and lower chord, located at the applicable body stations specified in the Accomplishment Instructions of Boeing Service Bulletin 737-57-1296, dated June 13, 2007, by doing all the actions specified in the Accomplishment Instructions of the service bulletin, except as provided by paragraph (g) of this AD. Do the inspections at the time specified in paragraph (f)(1) or (f)(2) of this AD, as applicable. (1) For Groups 1 and 2 airplanes as identified in the service bulletin: Do the inspections at the applicable initial compliance time listed in paragraph 1.E., “Compliance,” of the service bulletin; except, where the service bulletin specifies a compliance time after the date on the service bulletin, this AD requires compliance within the specified compliance time after the effective date of this AD. Repeat the inspections thereafter at the intervals specified in paragraph 1.E., “Compliance,” of the service bulletin. (2) For Group 3 airplanes as identified in the service bulletin: Do the inspections at the applicable initial compliance time listed in paragraph 1.E., “Compliance,” of the service bulletin; except, where the service bulletin specifies a compliance time after the date on the service bulletin, this AD requires compliance within the specified compliance time after the effective date of this AD. Repeat the inspections thereafter at the intervals specified in paragraph 1.E., “Compliance,” of the service bulletin. (g) If any crack is found during any inspection required by this AD, and Boeing Service Bulletin 737-57-1296, dated June 13, 2007, specifies contacting Boeing for repair instructions: Before further flight, repair using a method approved in accordance with the procedures specified in paragraph (h) of this AD. ### (h) Alternative Methods of Compliance (AMOCs) (h)(1) The Manager, Seattle Aircraft Certification Office, FAA, has the authority to approve AMOCs for this AD, if requested in accordance with the procedures found in 14 CFR 39.19. (2) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Before using any approved AMOC on any airplane to which the AMOC applies, notify your appropriate principal inspector (PI) in the FAA Flight Standards District Office (FSDO), or lacking a PI, your local FSDO. (3) An AMOC that provides an acceptable level of safety may be used for any repair required by this AD, if it is approved by an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization Organization who has been authorized by the Manager, Seattle ACO, to make those findings. For a repair method to be approved, the repair must meet the certification basis of the airplane. ### (i) Material Incorporated by Reference (i) You must use Boeing Service Bulletin 737-57-1296, dated June 13, 2007, to do the actions required by this AD, unless the AD specifies otherwise. (1) The Director of the Federal Register approved the incorporation by reference of this service information under 5 U.S.C. 552(a) and 1 CFR part 51. (2) For service information identified in this AD, contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207. (3) You may review copies of the service information incorporated by reference at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. ## Rule preamble ### Dates This AD is effective April 8, 2008. The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of April 8, 2008. ### Addresses For service information identified in this AD, contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207. ### For further information contact Nancy Marsh, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 917-6440; fax (425) 917-6590. ### Discussion We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an airworthiness directive (AD) that would apply to certain Boeing Model 737-100, -200, -300, -400, and -500 series airplanes. That NPRM was published in the Federal Register on November 26, 2007 (72 FR 65911). That NPRM proposed to require repetitive inspections for fatigue cracking in the longitudinal floor beam web, upper chord, and lower chord located at certain body stations, and repair if necessary. ### Comments We gave the public the opportunity to participate in developing this AD. We considered the comment received. Boeing, the single commenter, supports the NPRM. ### Conclusion We reviewed the relevant data, considered the comment received, and determined that air safety and the public interest require adopting the AD as proposed. ### Costs of Compliance There are 2,852 airplanes of the affected design in the worldwide fleet. This AD affects 652 airplanes of U.S. registry. The required inspection takes approximately 13 work hours per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the required inspection for U.S. operators is $678,080, or $1,040 per airplane, per inspection cycle. ### Authority for This Rulemaking Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. “Subtitle VII: Aviation Programs,” describes in more detail the scope of the Agency's authority. We are issuing this rulemaking under the authority described in “Subtitle VII, Part A, Subpart III, Section 44701: General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action. ### Regulatory Findings This AD will not have federalism implications under Executive Order 13132. This AD will not have a substantial direct effect on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. For the reasons discussed above, I certify that this AD: (1) Is not a “significant regulatory action” under Executive Order 12866, (2) Is not a “significant rule” under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979), and (3) Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. You can find our regulatory evaluation and the estimated costs of compliance in the AD Docket. ## Affected data sheets (1) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS A16WE](https://openairdocs.org/tcds/A16WE): The Boeing Company; names 5 of 17 models: 737-500 Series, 737-100 Series, 737-300 Series, 737-200 Series, 737-400 Series ## Registered aircraft it may apply to (OpenAirDocs) Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment. - Aircraft: 48 (48 by airframe model, 0 by engine model) - Makers: Boeing 48 Models with the most aircraft: - [Boeing 737-400](https://openairdocs.org/model/boeing-737-400): 8 aircraft (airframe model) - [Boeing 737-500](https://openairdocs.org/model/boeing-737-500): 6 aircraft (airframe model) - [Boeing 737-436](https://openairdocs.org/model/boeing-737-436): 6 aircraft (airframe model) - [Boeing 737-300](https://openairdocs.org/model/boeing-737-300): 4 aircraft (airframe model) - [Boeing 737-205](https://openairdocs.org/model/boeing-737-205): 3 aircraft (airframe model) - [Boeing 737-490](https://openairdocs.org/model/boeing-737-490): 3 aircraft (airframe model) - [Boeing 737-484](https://openairdocs.org/model/boeing-737-484): 3 aircraft (airframe model) - [Boeing 737-524](https://openairdocs.org/model/boeing-737-524): 3 aircraft (airframe model) - [Boeing 737-505](https://openairdocs.org/model/boeing-737-505): 2 aircraft (airframe model) - [Boeing 737-200](https://openairdocs.org/model/boeing-737-200): 1 aircraft (airframe model) - [Boeing 737-201](https://openairdocs.org/model/boeing-737-201): 1 aircraft (airframe model) - [Boeing 737-301](https://openairdocs.org/model/boeing-737-301): 1 aircraft (airframe model) - [Boeing 737-401](https://openairdocs.org/model/boeing-737-401): 1 aircraft (airframe model) - [Boeing 737-209](https://openairdocs.org/model/boeing-737-209): 1 aircraft (airframe model) - [Boeing 737-306](https://openairdocs.org/model/boeing-737-306): 1 aircraft (airframe model) - [Boeing 737-319](https://openairdocs.org/model/boeing-737-319): 1 aircraft (airframe model) - [Boeing 737-330](https://openairdocs.org/model/boeing-737-330): 1 aircraft (airframe model) - [Boeing 737-405](https://openairdocs.org/model/boeing-737-405): 1 aircraft (airframe model) - [Boeing 737-528](https://openairdocs.org/model/boeing-737-528): 1 aircraft (airframe model) All 19 models: https://openairdocs.org/ad/2008-05-06/models.md Every aircraft: https://openairdocs.org/ad/2008-05-06/aircraft.md ## Related documents - [AD 2016-13-11](https://openairdocs.org/ad/2016-13-11): Wings · Boeing 737-100 Series, 737-200 Series, 737-300 Series and 2 more. Effective Aug 9, 2016. Supersedes this AD - [Proposed rule FAA-2007-0224](https://openairdocs.org/proposed/FAA-2007-0224): Notice of proposed rulemaking (NPRM), published Nov 26, 2007 Its text cites no advisory circulars or STCs. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.