2023-03138. Airworthiness Directives; The Boeing Company Airplanes

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 747-8 series airplanes. This proposed AD was prompted by a report of stress corrosion cracking in certain stringers and end stringer splice assemblies. This proposed AD would require repetitive inspections of the stringers and end stringer splice assemblies for any crack, shim, or gap, and applicable on-condition actions. 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 March 31, 2023.

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: [phone].

• 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-2023-0157; 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 service information 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 [phone]; website myboeingfleet.com.

• You may view this service information at the FAA, Airworthiness Products Section, Operational Safety Branch, 2200 South 216th St., Des Moines, WA. For information on the availability of this material at the FAA, call 206-231-3195. It is also available at regulations.gov by searching for and locating Docket No. FAA-2023-0157.

FOR FURTHER INFORMATION CONTACT:

Stefanie N. Roesli, Aerospace Engineer, Airframe Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA 98198; phone: [phone]; email: [e-mail].

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-2023-0157; Project Identifier AD-2022-01309-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 Stefanie N. Roesli, Aerospace Engineer, Airframe Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA 98198; phone: [phone]; email: [e-mail]. 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 has received a report indicating cracks found on end stringers of two Model 747-8 airplanes at station (STA) 2285, left and right sides, during foreign object debris (FOD) inspections in preparation for airplane modification. Boeing has also reported similar cracking on other Model 747-8 airplanes. The cracks were not visually detectable until the stringer splice assemblies were removed. The root cause was found to be stress corrosion cracking caused by excessive and sustained internal tensile stresses that were due to no shim being installed or shimmed gaps exceeding engineering limits at production. A crack in a stringer or end stringer splice assembly could grow in length and go undetected. This condition, if not addressed, could result in the inability of a structural element to sustain limit load and could adversely affect the 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.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Boeing Alert Requirements Bulletin 747-53A2909 RB, dated September 21, 2022. This service information specifies procedures for repetitive detailed inspections of the stringers and the end stringer splice assemblies at stringers S-17 to S-25 from STA 2285 to STA 2300 main entry door #5 cutout aft edge frame for any crack, any shim between a stringer and bear strap, and any gap within the fastener-joint-to-bear-strap joint, and applicable on-condition actions. On-condition actions include detailed inspections of the stringers and end stringers splice assemblies located between STA 2285 and STA 2300 from stringers S-17L to S-25L/S-17R to S-25R, open hole high frequency eddy current (HFEC) inspection of the fastener holes of the skin common to the end stringer splice fitting for cracks, and repair of cracked stringer/end stringer splice fittings.

This service information 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 require accomplishing the actions specified in the service information already described except for any differences identified as exceptions in the regulatory text of this proposed AD. For information on the procedures and compliance times, see this service information at regulations.gov by searching for and locating Docket No. FAA-2023-0157.

Clarification of Terminating Action

Boeing Alert Requirements Bulletin 747-53A2909 RB, dated September 21, 2022, contains a terminating action flagnote (b) in Tables 1 through 4 of the Accomplishment Instructions that specifies “Doing the detailed and High Frequency Eddy Current (HFEC) inspections and finding no crack as a result of the inspection is terminating action to Requirements Bulletin 747-53A2909 RB for that affected end stringer splice assembly.” However, the flagnote “(b)” is located with certain conditions in Tables 1 through 4 and appears to be contradictory in certain locations, e.g., “Condition 8.2: No crack found as a result of option 2 inspections” specifies to do repetitive inspections; however the option 2 inspections are the detailed and HFEC inspections, which the flagnote specifies is terminating action. The FAA has clarified the terminating action in paragraphs (g)(1) through (4) of this proposed AD to confirm that no action is required for an end stringer splice assembly on which no cracking is found after the specified option 2 inspections are done.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would affect 2 airplanes of U.S. registry. The FAA estimates the following costs to comply with this proposed AD:

Estimated Costs

Action	Labor cost	Parts cost	Cost per product	Cost on U.S. operators
Detailed Inspection (S-17L to S-25L) and (S-17R to S-25R)	4 work-hours × $85 per hour = $340 per inspection cycle	$0	$340 per inspection cycle	$680 per inspection cycle.

The FAA estimates the following costs to do any necessary on-condition actions that would be required based on the results of the proposed inspection. The agency has no way of determining the number of aircraft that might need these on-condition actions:

On-Condition Costs

Action	Labor cost	Parts cost	Cost per product
Detailed Inspection and Open Hole (HFEC) Inspection per side	54 work-hours × $85 per hour = $4,590	$0	$4,590
Repair of cracked stringer/end stringer splice fitting	13 work-hours × $85 per hour = $1,105	600	1,705

The FAA has included all known costs in its cost estimate. According to the manufacturer, however, some or all of the costs of this proposed AD may be covered under warranty, thereby reducing the cost impact on affected operators.

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.

The FAA is 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

The FAA determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would 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 this proposed regulation:

(1) Is not a “significant regulatory action” under Executive Order 12866,

(2) Would not affect intrastate aviation in Alaska, and

(3) Would not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Incorporation by reference
• Safety

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

PART 39—AIRWORTHINESS DIRECTIVES

The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

§  39.13

[Amended]

The FAA amends § 39.13 by adding the following new airworthiness directive:

The Boeing Company: Docket No. FAA-2023-0157; Project Identifier AD-2022-01309-T.

(a) Comments Due Date

The FAA must receive comments on this airworthiness directive (AD) by March 31, 2023.

(b) Affected ADs

None.

(c) Applicability

This AD applies to The Boeing Company Model 747-8 series airplanes, certificated in any category, as identified in Boeing Alert Requirements Bulletin 747-53A2909 RB, dated September 21, 2022.

(d) Subject

Air Transport Association (ATA) of America Code 53, Fuselage.

(e) Unsafe Condition

This AD was prompted by a report of stress corrosion cracking in the stringers and end stringer splice assemblies located between station (STA) 2285 and STA 2300 from stringers S-17 to S-25 on the left and right sides of the airplane caused by excessive and sustained internal tensile stresses that were due to no shim being installed or shimmed gaps exceeding engineering limits at production. A crack in a stringer or end stringer splice assembly could grow in length and go undetected. The unsafe condition, if not addressed, could result in the inability of a structural element to sustain limit load and could adversely affect the structural integrity of the airplane.

(f) Compliance

Comply with this AD within the compliance times specified, unless already done.

(g) Required Actions

Except as specified by paragraph (h) of this AD: At the applicable times specified in the “Compliance” paragraph of Boeing Alert Requirements Bulletin 747-53A2909 RB, dated September 21, 2022, do all applicable actions identified in, and in accordance with, the Accomplishment Instructions of Boeing Alert Requirements Bulletin 747-53A2909 RB, dated September 21, 2022. For this AD, terminating action for certain end stringer springer splice assemblies are specified in paragraphs (g)(1) through (4) of this AD.

Note 1 to paragraph (g):

Guidance for accomplishing the actions required by this AD can be found in Boeing Alert Service Bulletin 747-53A2909 RB, dated September 21, 2022, which is referred to in Boeing Alert Requirements Bulletin 747-53A2909 RB, dated September 21, 2022.

(1) For any end stringer splice assembly on which no cracking is found after accomplishing CONDITION 3 (OPTION 2) (ACTION 1) and CONDITION 3 (OPTION 2) (ACTION 2) inspections specified in Table 1 of the Accomplishment Instruction of Boeing Alert Requirements Bulletin 747-53A2909 RB, dated September 21, 2022, no further action is required by this AD for that end stringer splice assembly.

(2) For any end stringer splice assembly on which no cracking is found after accomplishing CONDITION 6 (OPTION 2) (ACTION 1) and CONDITION 6 (OPTION 2) (ACTION 2) inspections specified in Table 2 of the Accomplishment Instruction of Boeing Alert Requirements Bulletin 747-53A2909 RB, dated September 21, 2022, no further action is required by this AD for that end stringer splice assembly.

(3) For any end stringer splice assembly on which no cracking is found after accomplishing CONDITION 8 (OPTION 2) (ACTION 1) and CONDITION 8 (OPTION 2) (ACTION 2) inspections specified in Table 3 of the Accomplishment Instruction of Boeing Alert Requirements Bulletin 747-53A2909 RB, dated September 21, 2022, no further action is required by this AD for that end stringer splice assembly.

(4) For any end stringer splice assembly on which no cracking is found after accomplishing CONDITION 10 (OPTION 2) (ACTION 1) and CONDITION 10 (OPTION 2) (ACTION 2) inspections specified in Table 4 of the Accomplishment Instruction of Boeing Alert Requirements Bulletin 747-53A2909 RB, dated September 21, 2022, no further action is required by this AD for that end stringer splice assembly.

(h) Exceptions to Service Information Specifications

(1) Where the Compliance Time column and certain notes of the tables in the “Compliance” paragraph of Boeing Alert Requirements Bulletin 747-53A2909 RB, dated September 21, 2022, use the phrase “the original issue date of Requirements Bulletin 747-53A2909 RB,” this AD requires using “the effective date of this AD.”

(2) Where Boeing Alert Requirements Bulletin 747-53A2909 RB, dated September 21, 2022, specifies contacting Boeing for repair instructions: This AD requires doing the repair using a method approved in accordance with the procedures specified in paragraph (i) of this AD.

(i) Alternative Methods of Compliance (AMOCs)

(1) The Manager, Seattle ACO Branch, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request to your principal inspector or responsible Flight Standards Office, as appropriate. If sending information directly to the manager of the certification office, send it to the attention of the person identified in paragraph (j) of this AD. Information may be emailed to: [e-mail].

(2) Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the responsible Flight Standards Office.

(3) An AMOC that provides an acceptable level of safety may be used for any repair, modification, or alteration required by this AD if it is approved by The Boeing Company Organization Designation Authorization (ODA) that has been authorized by the Manager, Seattle ACO Branch, FAA, to make those findings. To be approved, the repair method, modification deviation, or alteration deviation must meet the certification basis of the airplane, and the approval must specifically refer to this AD.

(j) Related Information

For more information about this AD, contact Stefanie N. Roesli, Aerospace Engineer, Airframe Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA 98198; phone: [phone]; email: [e-mail].

(k) Material Incorporated by Reference

(1) The Director of the Federal Register approved the incorporation by reference (IBR) of the service information listed in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.

(2) You must use this service information as applicable to do the actions required by this AD, unless the AD specifies otherwise.

(i) Boeing Alert Requirements Bulletin 747-53A2909 RB, dated September 21, 2022.

(ii) [Reserved]

(3) For service information identified in this AD, contact Boeing Commercial Airplanes, Attention: Contractual & Data Services (C&DS), 2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600; telephone [phone]; website myboeingfleet.com.

(4) You may view this service information at the FAA, Airworthiness Products Section, Operational Safety Branch, 2200 South 216th St., Des Moines, WA. For information on the availability of this material at the FAA, call 206-231-3195.

(5) You may view this service information that is incorporated by reference at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, [e-mail], or go to: www.archives.gov/​federal-register/​cfr/​ibr-locations.html.

Issued on January 27, 2023.

Christina Underwood,

Acting Director, Compliance & Airworthiness Division, Aircraft Certification Service.