2021-23935. Airworthiness Directives; The Boeing Company Airplanes

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 737-9 airplanes. This AD was prompted by a report of missing sealant on the left and right wing leading edge outboard blowout door. This AD requires doing a fluid seal contact inspection and a detailed inspection for missing sealant on each blowout door and applying sealant if necessary. The FAA is issuing this AD to address the unsafe condition on these products.

DATES:

This AD is effective December 8, 2021.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of December 8, 2021.

ADDRESSES:

For service information identified in this final rule, contact Boeing Commercial Airplanes, Attention: Contractual & Data Services (C&DS), 2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600; telephone [phone]; internet https://www.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 https://www.regulations.gov by searching for and locating Docket No. FAA-2020-1166.

Examining the AD Docket

You may examine the AD docket at https://www.regulations.gov by searching for and locating Docket No. FAA-2020-1166; 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.

FOR FURTHER INFORMATION CONTACT:

Chris Baker, Aerospace Engineer, Propulsion Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax: [phone]; email: [e-mail].

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 The Boeing Company Model 737-9 airplanes having line numbers 6834, 6852, 6872, 6899, 6917, 6935, 7096, 7173, 7196, 7201, 7208, 7216, 7246, 7253, 7261, 7268, 7306, 7316, 7338, 7348, 7361, 7384, 7388, 7394, and 7428. The NPRM published in the Federal Register on January 21, 2021 (86 FR 6269). The NPRM was prompted by a report indicating that the application of sealant on the left wing and right wing leading edge outboard blowout door was missed during the airplane manufacturing process on some Model 737-9 airplanes. In the NPRM, the FAA proposed to require doing a fluid seal contact inspection and a detailed inspection for missing sealant on each blowout door and applying sealant if necessary. The FAA is issuing this AD to address the missing sealant, which is intended to act as a fuel barrier. In the presence of a substantial fuel leak from the wing box, the unintended drain path could allow fuel to come into contact with the engine. This condition, if not addressed, could lead to a large ground fire.

Discussion of Final Airworthiness Directive

Comments

The FAA received comments from The Air Line Pilots Association, International (ALPA), Boeing, and an individual, who all stated that they supported the NPRM without change. The FAA also received comments from United Airlines (UAL) and two individuals. The following discussion presents those comments and the FAA's response.

Request To Use Alternative Products

UAL suggested that the FAA work with Boeing on identifying acceptable alternatives to the developer specified in the service information. UAL stated that during initial accomplishment of the inspection there were difficulties sourcing the specified developer due to the requirement in Boeing Alert Requirements Bulletin 737-57A1350 RB to use the bulk material and not the aerosol spray. UAL stated it was ultimately able to procure the required bulk material.

The FAA disagrees with the request to change the AD to allow the use of alternative developers. Use of the bulk developer identified in Boeing Alert Requirements Bulletin 737-57A1350 RB, dated April 23, 2020, is needed for effective inspection. The aerosol spray form of the developer penetrates more aggressively than the bulk form, so it could cause existing sealants to swell. The use of bulk material avoids the potential for false readings of the gasket contact verification to be caused by sealant swelling.

The commenter also did not identify any alternative developers in either bulk or aerosol spray that would be an acceptable alternative to the developer identified in Boeing Alert Requirements Bulletin 737-57A1350 RB, dated April 23, 2020. However, operators may submit an alternative method of compliance (AMOC) request using the procedures specified in paragraph (i) of this AD; the request should include data that substantiates the alternative developer will ensure an effective inspection to determine if additional sealant is required. The FAA has not changed this AD as a result of this comment.

Request for Information on the Approval Process for Alternative Materials

Two individuals asked about the approval process for alternative suitable materials (sealant) and procedures. In addition, the individuals questioned the role of the Boeing Company Organization Designation Authorization (ODA) in the approval process.

In order to receive an AMOC to use an alternate sealant, the AMOC request would need to show that the alternate sealant meets or exceeds the performance or characteristics of the current sealant that is identified in Boeing Alert Requirements Bulletin 737-57A1350 RB, dated April 23, 2020. While paragraph (i) of this AD indicates that AMOC authority may be delegated to the Boeing ODA, the ODA would still need to request that authority from the FAA and should include justification for why the authority should be granted. The FAA will then make the determination whether the ODA may grant AMOCs for this specific AD.

Conclusion

The FAA reviewed the relevant data, considered any comments received, and determined that air safety requires adopting this AD. Except for minor editorial changes, this AD is adopted as proposed in the NPRM.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Boeing Alert Requirements Bulletin 737-57A1350 RB, dated April 23, 2020. The service information specifies procedures for doing a fluid seal contact inspection and a detailed inspection of the left and right wing leading edge outboard blowout door, at the inboard and outboard ends of the hinge, for missing sealant and applying sealant, if necessary. 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 .

Costs of Compliance

The FAA estimates that this AD affects 14 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD:

Estimated Costs for Required Actions

Action	Labor cost	Parts cost	Cost per product	Cost on U.S. operators
Inspections	4 work-hours × $85 per hour = $340	$0	$340	$4,760

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

Estimated Costs of On-Condition Actions

Labor cost	Parts cost	Cost per product
Up to 4 work-hours × $85 per hour = Up to $340	Up to $100	Up to $440.

The FAA has included all known costs in this cost estimate. According to the manufacturer, however, some or all of the costs of this 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

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) Will not affect intrastate aviation in Alaska, 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.

List of Subjects in 14 CFR Part 39

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

The Amendment

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

PART 39—AIRWORTHINESS DIRECTIVES

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

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

§ 39.13

[Amended]

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

2021-19-19 The Boeing Company: Amendment 39-21737; Docket No. FAA-2020-1166; Project Identifier AD-2020-00906-T.

(a) Effective Date

This airworthiness directive (AD) is effective December 8, 2021.

(b) Affected ADs

None.

(c) Applicability

This AD applies to The Boeing Company Model 737-9 airplanes, certificated in any category, as identified in Boeing Alert Requirements Bulletin 737-57A1350 RB, dated April 23, 2020.

(d) Subject

Air Transport Association (ATA) of America Code 57, Wings.

(e) Unsafe Condition

This AD was prompted by a report of missing sealant on the left and right wing leading edge outboard blowout door. The FAA is issuing this AD to address the missing sealant, which is intended to act as a fuel barrier. In the presence of a substantial fuel leak from the wing box, the unintended drain path could allow fuel to come into contact with the engine. This condition, if not addressed, could lead to a large ground fire.

(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 737-57A1350 RB, dated April 23, 2020, do all applicable actions identified in, and in accordance with, the Accomplishment Instructions of Boeing Alert Requirements Bulletin 737-57A1350 RB, dated April 23, 2020.

Note 1 to paragraph (g):

Guidance for accomplishing the actions required by this AD can be found in Boeing Alert Service Bulletin 737-57A1350, dated April 23, 2020, which is referred to in Boeing Alert Requirements Bulletin 737-57A1350 RB, dated April 23, 2020.

(h) Exception to Service Information Specifications

Where Boeing Alert Requirements Bulletin 737-57A1350 RB, dated April 23, 2020, refers to “the Original Issue date of Requirements Bulletin 737-57A1350 RB,” this AD requires using “the effective date 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 Chris Baker, Aerospace Engineer, Propulsion Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax: [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 737-57A1350 RB, dated April 23, 2020.

(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]; internet https://www.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, email [e-mail], or go to: https://www.archives.gov/​federal-register/​cfr/​ibr-locations.html.

Issued on September 10, 2021.

Lance T. Gant,

Director, Compliance & Airworthiness Division, Aircraft Certification Service.