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AGENCY:
Federal Aviation Administration (FAA), DOT.
ACTION:
Notice of proposed rulemaking (NPRM).
SUMMARY:
The FAA proposes to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 737-800 series airplanes. This proposed AD was prompted by a determination that the compliance time for the initial ultrasonic inspection required by AD 2019-11-06 is insufficient for certain airplanes. This proposed AD would require reducing the compliance time for the ultrasonic inspection of the skin under the drag link assembly. The FAA is proposing this AD to address the unsafe condition on these products.
DATES:
The FAA must receive comments on this proposed AD by November 12, 2024.
ADDRESSES:
You may send comments, using the procedures found in 14 CFR 11.43 and 11.45, by any of the following methods:
- Federal eRulemaking Portal: Go to regulations.gov. Follow the instructions for submitting comments.
- Fax: 202-493-2251.
- Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.
- Hand Delivery: Deliver to Mail address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.
AD Docket: You may examine the AD docket at regulations.gov under Docket No. FAA-2024-2315; 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 NPRM, any comments received, and other information. The street address for Docket Operations is listed above.
Material Incorporated by Reference:
- For Boeing material identified in this NPRM, contact Boeing Commercial Airplanes, Attention: Contractual & Data Services (C&DS), 2600 Westminster Blvd., 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 St., Des Moines, WA.
FOR FURTHER INFORMATION CONTACT:
Owen Bley-Male, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 206-231-3992; email: owen.f.bley-male@faa.gov.
SUPPLEMENTARY INFORMATION:
Comments Invited
The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments to an address listed under ADDRESSES . Include “Docket No. FAA-2024-2315; Project Identifier AD-2023-00537-T” at the beginning of your comments. The most helpful comments reference a specific portion of the proposal, explain the reason for any recommended change, and include supporting data. The FAA will consider all comments received by the closing date and may amend this proposal because of those comments.
Except for Confidential Business Information (CBI) as described in the following paragraph, and other information as described in 14 CFR 11.35, the FAA will post all comments received, without change, to regulations.gov, including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this NPRM.
Confidential Business Information
CBI is commercial or financial information that is both customarily and actually treated as private by its owner. Under the Freedom of Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public disclosure. If your comments responsive to this NPRM contain commercial or financial information that is customarily treated as private, that you actually treat as private, and that is relevant or responsive to this NPRM, it is important that you clearly designate the submitted comments as CBI. Please mark each page of your submission containing CBI as “PROPIN.” The FAA will treat such marked submissions as confidential under the FOIA, and they will not be placed in the public docket of this NPRM. Submissions containing CBI should be sent to Owen Bley-Male, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 206-231-3992; email: owen.f.bley-male@faa.gov. Any commentary that the FAA receives that is not specifically designated as CBI will be placed in the public docket for this rulemaking.
Background
The FAA issued AD 2019-11-06, Amendment 39-19652 (84 FR 27193, June 12, 2019) (AD 2019-11-06) for certain The Boeing Company Model 737-600, 737-700, 737-700C, 737-800, 737-900, and 737-900ER series airplanes. AD 2019-11-06 requires ultrasonic inspections of the skin under the drag link assembly for cracks and applicable on-condition actions. The FAA issued AD 2019-11-06 to address cracking in the station (STA) 540 bulkhead chord or skin, which could result in the inability of a primary structural element to sustain limit load.
Since issuing AD 2019-11-06, the FAA has received a report that, for Model 737-800 series airplanes that have been modified to a freighter configuration using Boeing Drawing 800A0003, an evaluation of structural stresses using revised stress level calculations found that the inspection thresholds required by AD 2019-11-06 were insufficient. Those airplanes are subject to additional structural stresses due to the modifications done during conversion to a freighter configuration. Therefore, the compliance times for the initial inspections required by AD 2019-11-06 could be performed on those airplanes after the appropriate inspection threshold has passed, which could result in undetected cracking in the STA 540 bulkhead chord or skin. The FAA determined that, for those airplanes, a reduced compliance time is needed to address the unsafe condition. Accomplishing the actions required by this proposed AD would replace the initial ultrasonic inspections required by paragraph (g) of AD 2019-11-06 for Model 737-800 airplanes converted to a freighter configuration using Boeing Drawing 800A0003.
This condition, if not addressed, could lead to undetected cracking in the STA 540 bulkhead chord or skin, which could result in possible rapid decompression and loss of structural integrity of the airplane.
FAA's Determination
The FAA is issuing this NPRM after determining that the unsafe condition described previously is likely to exist or develop on other products of the same type design.
Material Incorporated by Reference Under 1 CFR Part 51
The FAA reviewed Boeing Alert Service Bulletin 737-53A1368, dated February 27, 2018. This material specifies an ultrasonic inspection of the skin under the drag link assembly and repair for any cracks; repetitive inspections for any cracks, including ultrasonic inspections, high frequency eddy current inspections, low frequency eddy current inspections, and detailed inspections; and a preventative modification if no crack is found.
The FAA also reviewed Boeing 737-800BCF Airworthiness Limitations, D140A006, Revision L, dated April 1, 2021. This material contains required inspections for principal structural element items. Section 5.2.1 of this material identifies the airplanes affected by this proposed AD.
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 ADDRESSES .
Proposed AD Requirements in This NPRM
This proposed AD would reduce the compliance time for the initial ultrasonic inspection required by AD 2019-11-06 for Model 737-800 series airplanes that have been converted to a freighter configuration using Boeing Drawing 800A0003.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, would affect 18 airplanes of U.S. registry. The FAA estimates the following costs to comply with this proposed AD:
Estimated Costs for Required Actions
| Action | Labor cost | Parts cost | Cost per product | Cost on U.S. operators |
|---|---|---|---|---|
| Initial inspection | Up to 23 work-hours × $85 per hour = $1,955 | $0 | $1,955 | Up to $35,190. |
Estimated Costs for On-Condition Actions
| Labor cost | Parts cost | Cost per product |
|---|---|---|
| Up to 56 work-hours × $85 per hour = $4,760 | $24,020 | Up to $28,780. |