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 all The Boeing Company Model 737 airplanes powered by LEAP-1B engines. This AD was prompted by reports of inadvertent release of the spring energy of the spring door opening system (SDOS) actuator with a certain part number, causing injury and the potential for injury to maintenance personnel. This AD requires replacing each affected SDOS actuator with a new SDOS actuator, and verifying that new safety markers are installed in the proper locations. The FAA is issuing this AD to address the unsafe condition on these products.

DATES:

This AD is effective September 3, 2021.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of September 3, 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 562-797-1717; 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 on the internet at https://www.regulations.gov by searching for and locating Docket No. FAA-2020-0333.

Examining the AD Docket

You may examine the AD docket on the internet at https://www.regulations.gov by searching for and locating Docket No. FAA-2020-0333; 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:

Rose Len, Aerospace Engineer, Propulsion Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax: 206-231-3604; email: rose.len@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 all The Boeing Company Model 737-8 and 737-9 airplanes. The NPRM published in the Federal Register on April 20, 2020 (85 FR 21791).

The NPRM was prompted by a report of an incident involving an SDOS actuator. The SDOS actuator is a telescopic, spring-loaded actuator that assists the mechanic in raising the engine fan cowl. Even when the actuator is extended (uncompressed), it retains energy in the spring (preloaded). In the incident, after an SDOS actuator with part number BOE-2001-901F was removed, a part separation occurred at the joint between the actuator's inner tube and its related “back end” bracket. The actuator came apart with spring-propelled force, injuring one of the maintenance personnel. This SDOS actuator used two roll pins and epoxy at this joint. The FAA has determined that this design, together with spring preload, caused these parts to break.

The FAA received a second report of a hazardous sudden extension of this actuator when, during improper removal of the SDOS actuator from the engine fan cowl while it was retracted, the SDOS actuator rapidly extended, with the potential to cause injury. This was possible because the fastener connecting the SDOS actuator to the fan cowl can be removed by cracking open the fan cowl and reaching under it. After the fastener was removed, the SDOS actuator was still connected to the engine fan case and was held in the retracted position by the “catch” hook, per the design. When the SDOS was rotated upward by hand, the catch hook released, and the SDOS actuator rapidly extended. The FAA has determined that the design of the SDOS actuator with part number BOE-2001-901H obscures the safety marker when the fan cowl is opened. The design of this SDOS actuator could, during maintenance, result in injury to maintenance personnel or damage to the airplane.

The manufacturer of the SDOS actuator, General Aerospace, has changed the design to have a stronger joint between the inner tube and the “back end” bracket that uses blind rivets rather than pins, together with an improved shape of the “catching” bracket. This redesign addressed the aforementioned part separation of the SDOS actuator, and the redesigned actuator became part number BOE-2001-901H. General Aerospace then modified part number BOE-2001-901H to include more detailed safety markers in new locations that display the warnings more clearly to maintenance personnel. That redesign addressed the aforementioned extension of the SDOS actuator from release of the catch hook. With the addition of the more detailed safety markers in the new locations, the SDOS actuator part number changed from BOE-2001-901H to BOE-2001-901J. General Aerospace Service Bulletin BOE-2001-901-71-01, dated November 2, 2019, which is referenced in Boeing Service Bulletin 737-71-1911, Revision 1, dated September 10, 2020, provides instructions for changing a BOE-2001-901H SDOS actuator to a BOE-2001-901J SDOS actuator.

The NPRM therefore proposed to require replacing each affected SDOS actuator with a new SDOS actuator, and verifying that the new safety markers are installed in the proper locations on the SDOS actuator.

The FAA is issuing this AD to address the possible separation of the SDOS actuator, and the visual obstruction of the SDOS actuator safety marker, either of which, during maintenance, could cause injury to maintenance personnel or damage to the airplane.

Actions Since the NPRM Was Issued

In the NPRM, the FAA proposed that the AD would apply to Boeing model 737-8 and 737-9 airplanes. Since then, the FAA determined that all Boeing model 737 airplanes powered by LEAP-1B engines (737 MAX airplanes), have engine fan cowls on which affected SDOS actuators could be installed. The affected SDOS actuators are rotable parts, so the future replacement of an SDOS actuator could reintroduce the unsafe condition. The 737 airplane models that are powered by LEAP-1B engines, and therefore that have fan cowls on which affected SDOS actuators could be installed, are currently the Model 737-8, 737-9, and 737-8200. The airplane models on which affected actuators could be installed could include any 737 models which will be powered by LEAP-1B engines, such as the Model 737-7. Therefore the FAA has revised the applicability of this AD to include all Model 737 airplanes powered by LEAP-1B engines. The prohibition on the installation of an affected SDOS actuator similarly applies to all airplanes identified in the applicability of this AD.

Comments

The FAA gave the public the opportunity to participate in developing this final rule. The following presents the comments received on the NPRM and the FAA's response to each comment.

Request To Update the Service Information to the Latest Revision

Boeing requested that the FAA mandate Boeing Special Attention Requirements Bulletin 737-71-1911 RB, Revision 1, dated September 10, 2020, because of various updates including removing retrofitted airplanes from the effectivity, group and configuration changes, and adapting certain instructions to allow work to be done on an individual fan cowl instead of all fan cowls at once. The revised service information does not add work for any airplane.

The FAA agrees. The service information mandated by this AD has been updated, to Boeing Special Attention Requirements Bulletin 737-71-1911 RB, Revision 1, dated September 10, 2020.

Request To Include Later Approved Revisions of the Service Information

American Airlines and United Airlines requested that paragraph (g) of the proposed AD be changed to include the words “or later approved revisions” with regards to Boeing Special Attention Requirements Bulletin 737-71-1911 RB, dated November 26, 2019.

The requested revision to paragraph (g) of the proposed AD to allow use of later-approved revisions of the service information would be contrary to Office of the Federal Register (OFR) regulations regarding incorporation by reference. Specifically, incorporation by reference of a publication is limited to the edition of the publication that is approved by OFR. 1 CFR 51.1(f). To allow operators to use later revisions of the referenced document that are not approved by the OFR and identified in the AD, either the FAA must (1) seek OFR approval to incorporate a later revision of the service document and revise the AD to reference the approved later revision, or (2) operators must request approval to use a later revision as an alternative method of compliance with this AD under the provisions of paragraph (k) of this AD.

Request for Clarification of the RC Steps in the Service Information

American Airlines requested clarification of paragraph (g) of the proposed AD. The commenter stated that it believes that the RC steps in both Boeing Special Attention Service Bulletin 737-71-1911 and Requirements Bulletin 737-71-1911 RB can be interpreted to mean that all steps of each Work Package are Required for Compliance. The company also states that the instruction to “Refer to the listed procedures in SB 737-71-1911 Original Issue or later approved revisions as an accepted procedure” found in each Work Package can be interpreted to mean that any part of the Work Package can be deviated from at the discretion of the operator, using the accepted procedures in the service information.

The FAA notes that Boeing's intention in including the multiple Work Packages, and the FAA's intention in mandating them, is to provide flexibility to the operator in the sequence of performing the mandated corrective actions. Each Work Package can be implemented one at a time. Each Work Package is defined by a unique combination of Group, Configuration, Engine 1 or Engine 2, and LEFT or RIGHT Fan Cowl descriptors. All of the Work Packages do not apply to every affected airplane.

The FAA further notes that both Boeing Special Attention Service Bulletin 737-71-1911 and Requirements Bulletin 737-71-1911 RB are consistent in their “RC: Start” and “RC: End” designations, which clearly delineate those Required Actions that are mandated by this AD. The instructions outside of the “RC: Start” and “RC: End” steps can be used to accomplish the required actions, but the AD does not authorize operators to use them as alternatives to the required actions. Where the service information specifies to “refer to” a recommended procedure, and only for those steps, operators may use an accepted alternative procedure.

The FAA has added paragraph (i) to this AD to provide credit for the previous accomplishment of Boeing Special Attention Requirements Bulletin 737-71-1911 RB, dated November 26, 2019.

Request for Clarification on the Correct Number of Safety Markers

American Airlines asked if the FAA requires a certain number of safety markers on SDOS part number (P/N) BOE-2001-901J units that have been changed from SDOS P/N BOE-2001-901H units. The AD requires that two P/N 12299 safety markers be installed on the SDOS actuator outer tube (cowl door side) if they are not already installed, but the commenter noted that there could be a third safety marker, P/N BOE-2001-713, already installed.

The FAA notes that an operator can comply with this AD by installing either (1) a P/N BOE-2001-901J actuator with its two original safety markers, or (2) a P/N BOE-2001-901H actuator that has been converted to a P/N BOE-2001-901J actuator with two new safety markers, with or without a third marker. The FAA has not changed this AD regarding this request.

Request for Clarification on Newly Delivered Airplanes

American Airlines requested clarification on whether the operator would need to request an AMOC for the newly delivered airplanes that already have the SDOS part number BOE-2001-901J. The commenter noted that paragraph (g) of the proposed AD did not include Boeing Special Attention Requirements Bulletin 737-71-1911 RB, Revision 1, dated September 10, 2020.

The FAA notes that AMOCs will not be necessary for airplanes that are newly delivered with the P/N BOE-2001-901J SDOS actuator installed. As previously explained, paragraph (g) of this AD has been updated to include Boeing Special Attention Requirements Bulletin 737-71-1911 RB, Revision 1, dated September 10, 2020, which includes a revised effectivity list. No further change to this AD is necessary.

Request for Change to the Airplane Applicability

American Airlines and United Airlines requested that paragraph (c) of the proposed AD be amended to be limited to airplanes identified in the Effectivity section of Boeing Special Attention Requirements Bulletin 737-71-1911 RB. As an alternative, American Airlines requested that a sub-paragraph be added to paragraph (h) of the proposed AD to state that a review of maintenance and delivery records can be used to determine the installed SDOS actuator part number, provided the SDOS part number can be definitively determined from the records check.

The FAA notes that paragraph (c) of this AD now includes all Boeing Model 737 airplanes powered by LEAP-1B engines. Paragraph (g) of this AD now mandates Boeing Special Attention Requirements Bulletin 737-71-1911 RB, Revision 1, dated September 10, 2020. Because all Model 737 airplanes powered by LEAP-1B engines have engine fan cowls that, due to the rotability of the affected parts, are subject to the same SDOS actuator issue, paragraph (j) of this AD now prohibits the installation of SDOS actuators having part numbers BOE-2001-901F and BOE-2001-901H on all Model 737 airplanes powered by LEAP-1B engines.

Request To Allow Use of Alternative Lockwire

American Airlines requested that the FAA allow use of .040 lockwire for the lock wire specified in steps 1(b) and 2(b) of the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-71-1911, dated November 26, 2019. American Airlines noted that the .040 lockwire is more common and readily available than .041 lockwire and would provide an equivalent level of safety. American Airlines expressed concern that if the FAA interpreted use of .041 lockwire as an RC step, the .040 lockwire could easily be mistakenly used due to the similarity to the .041 lockwire. The commenter requested that the FAA include an exception regarding this issue if appropriate.

The FAA notes that for the purposes of the SDOS actuator, .040 lockwire will function the same as .041 lockwire. The FAA further notes that Boeing Special Attention Requirements Bulletin 737-71-1911 RB, Revision 1, dated September 10, 2020, does not specify the use of lockwire in an RC step. Therefore, no change to this AD is necessary as a result of this comment.

Request To Change Description of the Incidents Prompting This AD

Boeing requested an update to the SUMMARY and Discussion sections of the NPRM, and paragraph (e) of the proposed AD, to clarify that there were two different causes and corrective actions.

The FAA agrees and has revised the Summary, Background, and paragraph (e) of this AD to delineate the two corrective actions. The Background section of this final rule describes in detail the two incidents and how each resulted in the actuator's sudden and hazardous extension. To address the cause of each incident, this AD requires two actions, both of which are unchanged from the NPRM: (1) Replacing each affected SDOS actuator with a new SDOS actuator, and (2) verifying that new safety markers are installed in the proper locations.

Request To Update the Number of Affected U.S. Airplanes

Boeing stated that the number of affected U.S.-registered airplanes identified in the Costs of Compliance section depends on whether the NPRM covers only the SDOS attachment issue (in which case Boeing stated the number is correct), or also covers the safety marker issue (in which case Boeing stated an additional 240 airplanes would be affected).

The FAA notes that since this AD addresses both the SDOS actuator attachment issue and the safety marker issue, both types of affected SDOS actuators must be replaced, resulting in an additional 240 U.S.-registered airplanes that would be affected. The estimated cost for this AD has been updated to reflect a total of 400 U.S.-registered airplanes.

Request To Revise Cost Estimate

Boeing requested that the FAA revise the Costs of Compliance section of the NPRM to correct the labor cost calculation to $425 per airplane.

The FAA agrees that the NPRM provided an incorrect estimate for the number of work-hours to replace the SDOS actuators. The FAA has revised the costs accordingly in this final rule.

Request To Modify the Affected Part Without Removal

Southwest Airlines requested clarification as to whether the SDOS actuator part number BOE-2001-901H can be changed on wing to part number BOE-2001-901J using the General Aerospace Service Bulletin BOE-2001-901-71-01 referenced in the Boeing Special Attention Service Bulletin 737-71-1911, Revision 1, dated September 10, 2020. Southwest Airlines stated that it believes it is possible to do so.

The FAA notes that neither General Aerospace Service Bulletin BOE-2001-901-71-01, which is referenced in Boeing Special Attention Service Bulletin 737-71-1911, nor Boeing Special Attention Requirements Bulletin 737-71-1911 RB, Revision 1, both dated September 10, 2020, requires removing the SDOS actuator before applying the safety markers. No change to this final rule is necessary as a result of this comment.

Request To Clarify the Need for Ongoing Inspections

Southwest Airlines asked whether the FAA was developing a requirement for ongoing inspections to make sure the safety markers are still present. The commenter stated that Boeing Special Attention Requirements Bulletin 737-71-1911 RB, dated November 26, 2019, does not mention inspecting for safety markers after the initial compliance.

The FAA notes that proper installation of the safety markers is intended to be permanent; therefore, no repetitive inspections of the safety marker installation are necessary. Because all Model 737 airplanes powered by LEAP-1B engines have engine fan cowls that, due to parts rotability, are subject to reinstallation of affected SDOS actuators, those airplanes are subject to the requirements of paragraph (j) of this AD, which prohibits the installation of SDOS actuators having part numbers BOE-2001-901F and BOE-2001-901H. The FAA has not changed this AD as a result of the comment.

Request To Include Instructions for Examination of Spare Parts

United Airlines requested clarification of actions required for spare parts. The commenter asserted that spare parts should be handled in the same manner as parts found installed on the aircraft once they are removed and that Paragraph 3.B., Work Instructions, provided in the Boeing Special Attention Service Bulletin 737-71-1911, dated November 26, 2019, are intended to be performed at an aircraft level with some steps not being applicable.

The FAA disagrees and has not changed the AD with regard to this request. ADs in general do not apply directly to spare parts because under 14 CFR part 39, ADs are legally enforceable rules that apply only to products such as airplanes, and not to parts that are not installed on an airplane. The FAA can, by AD, prohibit or condition the installation of a part on a product. This AD prohibits the installation of SDOS actuators having part numbers BOE-2001-901F and BOE-2001-901H. However, the FAA notes that Boeing Special Attention Service Bulletin 737-71-1911, Revision 1, dated September 10, 2020, includes non-mandatory information on how to contact General Aerospace for shipping instructions for SDOS actuator part number BOE-2001-901F, although this AD does not require the return of any parts. Further, the BOE-2001-901H SDOS actuators can be changed to BOE-2001-901J SDOS actuators.

Conclusion

The FAA reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting this final rule with the changes described previously and minor editorial changes. The FAA has determined that these minor changes:

• Are consistent with the intent that was proposed in the NPRM for addressing the unsafe condition; and
• Do not add any additional burden upon the public than was already proposed in the NPRM.

The FAA also determined that these changes will not increase the economic burden on any operator or increase the scope of this final rule.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Boeing Special Attention Requirements Bulletin 737-71-1911 RB, Revision 1, dated September 10, 2020. This service information describes procedures for replacing each affected SDOS actuator with a new SDOS actuator and verifying that safety markers are installed. 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 the ADDRESSES section.

Costs of Compliance

The FAA estimates that this AD affects 400 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD:

The FAA has included all known costs in its 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 persons.

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

Adoption of 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.

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

2021-13-18 The Boeing Company: Amendment 39-21623; Docket No. FAA-2020-0333; Product Identifier 2020-NM-015-AD.

(a) Effective Date

This AD is effective September 3, 2021.

(b) Affected ADs

None.

(c) Applicability

This AD applies to all The Boeing Company Model 737 airplanes powered by LEAP-1B engines, certificated in any category.

(d) Subject

Air Transport Association (ATA) of America Code 71, Powerplant.

(e) Unsafe Condition

This AD was prompted by reports of inadvertent release of the spring energy of certain spring door opening system (SDOS) actuators. The FAA is issuing this AD to address possible separation of the SDOS actuator and visual obstruction of the SDOS actuator safety marker, which, during maintenance, can cause injury to maintenance personnel or damage to the airplane.

(f) Compliance

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

(g) Required Actions

For airplanes identified in Boeing Special Attention Requirements Bulletin 737-71-1911 RB, Revision 1, dated September 10, 2020: At the applicable times specified in the “Compliance” paragraph of Boeing Special Attention Requirements Bulletin 737-71-1911 RB, Revision 1, dated September 10, 2020, except as specified by paragraph (h) of this AD, do all applicable actions identified in, and in accordance with, the Accomplishment Instructions of Boeing Special Attention Requirements Bulletin 737-71-1911 RB, Revision 1, dated September 10, 2020.

Note 1 to paragraph (g): Guidance for accomplishing the actions required by this AD can be found in Boeing Special Attention Service Bulletin 737-71-1911, Revision 1, dated September 10, 2020, which is referred to in Boeing Special Attention Requirements Bulletin 737-71-1911 RB, Revision 1, dated September 10, 2020.

(h) Exception to Service Information Specifications

Where Boeing Special Attention Requirements Bulletin 737-71-1911 RB, Revision 1, dated September 10, 2020, uses the phrase “the original issue date of Requirements Bulletin 737-71-1911 RB,” this AD requires using “the effective date of this AD.”

(i) Credit for Previous Actions

This paragraph provides credit for the actions specified in paragraph (g) of this AD, if those actions were performed before the effective date of this AD using Boeing Special Attention Requirements Bulletin 737-71-1911 RB, dated November 26, 2019.

(j) Parts Installation Prohibition

As of the effective date of this AD, no person may install on any airplane an SDOS actuator having part number BOE-2001-901F or BOE-2001-901H.

(k) 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 local Flight Standards District 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 (l) of this AD. Information may be emailed to: 9-ANM-Seattle-ACO-AMOC-Requests@faa.gov.

(2) Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the local flight standards district office/certificate holding district 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.

(l) Related Information

For more information about this AD, contact Rose Len, Aerospace Engineer, Propulsion Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax: 206-231-3604; email: rose.len@faa.gov.

(m) 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 Special Attention Requirements Bulletin 737-71-1911 RB, Revision 1, dated September 10, 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 562-797-1717; 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 fedreg.legal@nara.gov, or go to: https://www.archives.gov/federal-register/cfr/ibr-locations.html.