Airworthiness Directives; The Boeing Company Airplanes, 38214-38218 [2021-15391]

Download as PDF 38214 Federal Register / Vol. 86, No. 136 / Tuesday, July 20, 2021 / Rules and Regulations DEPARTMENT OF TRANSPORTATION Federal Aviation Administration 14 CFR Part 39 [Docket No. FAA–2021–0561; Project Identifier AD–2021–00623–T; Amendment 39–21647; AD 2021–14–20] RIN 2120–AA64 Airworthiness Directives; The Boeing Company Airplanes Federal Aviation Administration (FAA), DOT. ACTION: Final rule; request for comments. AGENCY: The FAA is adopting a new airworthiness directive (AD) for all The Boeing Company Model 737 airplanes. This AD was prompted by reports of latent failures of the cabin altitude pressure switches. This AD requires repetitive functional tests of the pressure switches, and on-condition actions, including replacement, if necessary. The FAA is issuing this AD to address the unsafe condition on these products. DATES: This AD is effective July 20, 2021. The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of July 20, 2021. The FAA must receive comments on this AD by September 3, 2021. 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 https://www.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. 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 khammond on DSKJM1Z7X2PROD with RULES SUMMARY: VerDate Sep<11>2014 15:59 Jul 19, 2021 Jkt 253001 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–2021– 0561. Examining the AD Docket You may examine the AD docket at https://www.regulations.gov by searching for and locating Docket No. FAA–2021–0561; 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 street address for Docket Operations is listed above. FOR FURTHER INFORMATION CONTACT: Nicole Tsang, Aerospace Engineer, Cabin Safety and Environmental Systems Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax: 206– 231–3959; email: Nicole.S.Tsang@ faa.gov. SUPPLEMENTARY INFORMATION: Background The FAA requires every proposed transport category airplane design with a pressurized cabin to include a system that warns the flightcrew of cabin depressurization. 14 CFR 25.841(b). On Boeing Model 737 airplanes, such warning systems include a cabin altitude pressure switch. The functions of this pressure switch are twofold: To detect if a certain cabin pressure altitude has been exceeded; and if so, to send a signal to the parts of the system that provide aural and visual warnings to the flightcrew. When this switch fails, it fails latently; that is, without making the failure known to the flightcrew or maintenance personnel. Due to the importance of the functions provided by this switch, in 2012 the FAA mandated that all Boeing Model 737 airplanes utilize two switches, to provide redundancy in case of one switch’s failure. AD 2012–19–11, Amendment 39–17206 (77 FR 60296, October 3, 2012).1 The FAA has received reports of latent failures of these cabin altitude pressure switches. In September 2020, an operator reported that on three of its airplanes, both pressure switches failed the on-wing functional test. The affected switches were on three different models of the Boeing 737. The airplane manufacturer investigated, and initially found, for reasons that included the expected 1 This airworthiness directive was eventually superseded by AD 2015–21–11, Amendment 39– 18304 (80 FR 65927, October 28, 2015) (AD 2015– 21–11). PO 00000 Frm 00006 Fmt 4700 Sfmt 4700 failure rate of the switches, that it did not pose a safety issue. Boeing decided in November 2020 that the failures were not a safety issue. Subsequent investigation and analysis led the FAA and the airplane manufacturer to determine, in May of 2021, that the failure rate of both switches is much higher than initially estimated, and therefore does pose a safety issue. The FAA does not yet have sufficient information to determine what has caused this unexpectedly high failure rate, so a terminating corrective action cannot yet be developed. However, a latent failure of both pressure switches could result in the loss of cabin altitude warning, which could delay flightcrew recognition of a lack of cabin pressurization, and result in incapacitation of the flightcrew due to hypoxia (a lack of oxygen in the body), and consequent loss of control of the airplane. Therefore addressing these failures requires immediate action. The FAA is issuing this AD to address the unsafe condition on these products. FAA’s Determination The FAA is issuing this AD because the agency has determined the unsafe condition described previously is likely to exist or develop in other products of the same type design. Related Service Information Under 1 CFR Part 51 The FAA reviewed Boeing Multi Operator Message MOM–MOM–21– 0292–01B, dated June 23, 2021. This service information specifies procedures for repetitive functional tests of the cabin altitude pressure switches, oncondition actions including follow-on functional testing and replacement of failed switches, sending a report to Boeing about any pressure switches that fail the initial functional test, and reporting to Boeing the airplanes in the operator’s fleet that have been tested. 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. AD Requirements This AD requires accomplishing the actions specified in the service information already described, except as discussed under ‘‘Differences Between this AD and the Service Information.’’ This AD also requires reporting to Boeing the results of the first functional test if any pressure switch failed, and sending reports to Boeing of the airplanes in the operator’s fleet that have been tested. E:\FR\FM\20JYR1.SGM 20JYR1 Federal Register / Vol. 86, No. 136 / Tuesday, July 20, 2021 / Rules and Regulations Effect of Certain Installation Procedures on Accomplishment of AD Requirements As previously noted, the FAA issued AD 2015–21–11, applicable to certain Model 737–100, –200, –200C, –300, –400, –500, –600, –700, –700C, –800, –900, and –900ER series airplanes. AD 2015–21–11 requires, among other actions, the installation of a redundant cabin altitude pressure switch in accordance with specified Boeing service information. The FAA has since approved numerous supplemental type certificates (STCs) and other means for installing the redundant pressure switch. As a result of its oversight of these newly-installed switches, the FAA has determined that use of approved maintenance procedures for the cabin altitude pressure switch functional test other than those specified in the task cards identified in Boeing Multi Operator Message MOM–MOM–21– 0292–01B, dated June 23, 2021, is acceptable for the functional test; therefore, those other procedures do not require approval of an alternative method of compliance (AMOC). khammond on DSKJM1Z7X2PROD with RULES Differences Between This AD and the Service Information Although Boeing Multi Operator Message MOM–MOM–21–0292–01B, dated June 23, 2021, affects ‘‘all 737CL’’ airplanes (the 737 Classics include Model 737–100, –200, –200C, –300, –400, and –500), Boeing did not send the MOM to Model 737–100, –200 and –200C operators. Additionally, Boeing did not reference procedures for performing the cabin altitude pressure switch functional test for Model 737– 100, –200, and –200C series airplanes. There are no Model 737–100 series airplanes operating worldwide; however, the applicability of this AD includes those airplanes in the event any of those airplanes are returned to service in the U.S. The FAA has also included Model 737–200 and –200C series airplanes in the applicability of this AD. Furthermore, the FAA requested that Boeing make the service information available to Model 737–200 and –200C operators. Boeing Model 737–200 and –200C operators may reference 737–200 Airplane Maintenance Manual (AMM) 21–33–11/ 501 for additional guidance on performing the cabin altitude pressure switch functional test. Boeing Multi Operator Message MOM–MOM–21–0292–01B, dated June 23, 2021, uses permissive language, such as ‘‘recommends’’ and ‘‘requesting,’’ in its ‘‘Functional Test Requirements’’ and ‘‘Reporting VerDate Sep<11>2014 15:59 Jul 19, 2021 Jkt 253001 Requirements’’ sections. However, the regulatory text in paragraphs (g) and (h) of this AD makes the language in those sections mandatory unless an exception in paragraph (j) of this AD applies. Boeing Multi Operator Message MOM–MOM–21–0292–01B, dated June 23, 2021, recommends returning failed pressure switches to the switch manufacturer. Although the FAA also recommends that operators return failed pressure switches in order to provide the switch manufacturer with additional data related to the unsafe condition, this AD does not require that action. Although Boeing Multi Operator Message MOM–MOM–21–0292–01B, dated June 23, 2021, identifies specific AMM task cards for use in accomplishing the functional test, paragraph (j)(1) of this AD clarifies that any approved maintenance procedures may be used for the functional test. This provides the operator an option to use the AMM task card or any approved maintenance procedure for the functional test without needing to request an AMOC. Boeing Multi Operator Message MOM–MOM–21–0292–01B, dated June 23, 2021, specifies certain on-condition actions, including an additional step while performing the functional test on the switch by increasing the altitude setting on the switch to an altitude of up to 20,000 feet if the cabin altitude warning does not activate by 11,000 feet during the initial functional test. The service information specifies repeating the functional test at intervals, but does not explicitly state that the on-condition additional functional testing is limited to the initial functional test only. Paragraph (j)(3) of this AD requires the on-condition additional functional test step of increasing the altitude setting to 20,000 feet only during the initial functional test (if applicable). Although Boeing Multi Operator Message MOM–MOM–21–0292–01B, dated June 23, 2021, specifies that failed switches be replaced with ‘‘new or serviceable’’ switches, this AD requires replacement with ‘‘serviceable’’ switches, which include any switches that are eligible for installation. This is to ensure that any installed switch is serviceable. Interim Action The FAA considers this AD to be an interim action. The reporting that is required by this AD will enable the airplane manufacturer to obtain better insight into the nature, cause, and extent of the switch failures, and eventually to develop final action to address the unsafe condition. Once final PO 00000 Frm 00007 Fmt 4700 Sfmt 4700 38215 action has been identified, the FAA might consider further rulemaking. Justification for Immediate Adoption and Determination of the Effective Date Section 553(b)(3)(B) of the Administrative Procedure Act (APA) (5 U.S.C. 551 et seq.) authorizes agencies to dispense with notice and comment procedures for rules when the agency, for ‘‘good cause,’’ finds that those procedures are ‘‘impracticable, unnecessary, or contrary to the public interest.’’ Under this section, an agency, upon finding good cause, may issue a final rule without providing notice and seeking comment prior to issuance. Further, section 553(d) of the APA authorizes agencies to make rules effective in less than thirty days, upon a finding of good cause. An unsafe condition exists that requires the immediate adoption of this AD without providing an opportunity for public comments prior to adoption. The FAA has found that the risk to the flying public justifies forgoing notice and comment prior to adoption of this rule because, as previously noted, the unexpectedly high rate of latent failure, of both pressure switches on the same airplane, could result in the cabin altitude warning system not activating if the cabin altitude exceeds 10,000 feet, resulting in hypoxia of the flightcrew, and loss of control of the airplane. Accordingly, notice and opportunity for prior public comment are impracticable and contrary to the public interest pursuant to 5 U.S.C. 553(b)(3)(B). In addition, the FAA finds that good cause exists pursuant to 5 U.S.C. 553(d) for making this amendment effective in less than 30 days, for the same reasons the FAA found good cause to forgo notice and comment. Comments Invited The FAA invites you to send any written data, views, or arguments about this final rule. Send your comments to an address listed under ADDRESSES. Include Docket No. FAA–2021–0561 and Project Identifier AD–2021–00623– T at the beginning of your comments. The most helpful comments reference a specific portion of the final rule, 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 final rule 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 https:// E:\FR\FM\20JYR1.SGM 20JYR1 38216 Federal Register / Vol. 86, No. 136 / Tuesday, July 20, 2021 / Rules and Regulations www.regulations.gov, including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this final rule. 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 AD 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 AD, 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 AD. Submissions containing CBI should be sent to Nicole Tsang, Aerospace Engineer, Cabin Safety and Environmental Systems Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax: 206–231–3959; email: Nicole.S.Tsang@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. Regulatory Flexibility Act The requirements of the Regulatory Flexibility Act (RFA) do not apply when an agency finds good cause pursuant to 5 U.S.C. 553 to adopt a rule without prior notice and comment. Because the FAA has determined that it has good cause to adopt this rule without notice and comment, RFA analysis is not required. Costs of Compliance The FAA estimates that this AD affects 2,502 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD: ESTIMATED COSTS Action Labor cost Functional test ........ 1 work-hour × $85 per hour = $85 per test ................................... In addition, the FAA has determined that preparing and sending a monthly report of tested airplanes takes about 1 work-hour per operator. Since operators are required to submit this report for their affected fleet(s), the FAA has determined that a per-operator estimate Cost per product Parts cost is more appropriate than a per-airplane estimate. Therefore, the FAA estimates the average total cost of the monthly report to be $85 (1 work-hour × $85) per report, per operator. The FAA estimates the following costs to do any necessary on-condition $0 Cost on U.S. operators $85 per test ... $212,670 per test. actions that would be required based on the results of the functional test. The FAA has no way of determining the number of aircraft that might need these actions: ON-CONDITION COSTS Action Labor cost On-condition functional test and switch replacement .. Reporting ...................................................................... 1 work-hour × $85 per hour = $85 ............................... 1 work-hour × $85 per hour = $85 ............................... khammond on DSKJM1Z7X2PROD with RULES Paperwork Reduction Act A federal agency may not conduct or sponsor, and a person is not required to respond to, nor shall a person be subject to a penalty for failure to comply with a collection of information subject to the requirements of the Paperwork Reduction Act unless that collection of information displays a currently valid OMB Control Number. The OMB Control Number for this information collection is 2120–0056. Public reporting for this collection of information is estimated to be approximately 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, completing and reviewing the collection of information. All responses to this collection of information are mandatory. Send comments regarding this burden estimate or any other aspect of this VerDate Sep<11>2014 15:59 Jul 19, 2021 Jkt 253001 Parts cost $1,278 0 Cost per product $1,363 85 collection of information, including suggestions for reducing this burden to: Information Collection Clearance Officer, Federal Aviation Administration, 10101 Hillwood Parkway, Fort Worth, TX 76177–1524. 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. 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 Regulatory Findings PO 00000 Frm 00008 Fmt 4700 Sfmt 4700 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, and (2) Will not affect intrastate aviation in Alaska. E:\FR\FM\20JYR1.SGM 20JYR1 Federal Register / Vol. 86, No. 136 / Tuesday, July 20, 2021 / Rules and Regulations 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. § 39.13 [Amended] 2. The FAA amends § 39.13 by adding the following new airworthiness directive: ■ 2021–14–20 The Boeing Company: Amendment 39–21647; Docket No. FAA–2021–0561; Project Identifier AD– 2021–00623–T. (a) Effective Date This airworthiness directive (AD) is effective July 20, 2021. (b) Affected ADs None. (c) Applicability This AD applies to all The Boeing Company Model 737 airplanes, certificated in any category. (d) Subject Air Transport Association (ATA) of America Code 21, Air conditioning. (e) Unsafe Condition This AD was prompted by reports of latent failures of the cabin altitude pressure switches. The FAA is issuing this AD to address the unexpectedly high rate of latent failure of both pressure switches on the same airplane which could result in the cabin altitude warning system not activating if the cabin altitude exceeds 10,000 feet, resulting in hypoxia of the flightcrew, and loss of control of the airplane. khammond on DSKJM1Z7X2PROD with RULES (f) Compliance Comply with this AD within the compliance times specified, unless already done. (g) Repetitive Functional Tests Except as specified in paragraph (j) of this AD: At the latest of the times specified in paragraphs (g)(1) through (3) of this AD, perform the initial functional test of the cabin altitude pressure switches, and before further flight, do all applicable on-condition actions, in accordance with the ‘‘Functional Test Requirements’’ section of Boeing Multi Operator Message MOM–MOM–21–0292– 01B, dated June 23, 2021. Repeat the functional test thereafter at intervals not to exceed 2,000 flight hours and do all applicable on condition actions before further flight. VerDate Sep<11>2014 15:59 Jul 19, 2021 Jkt 253001 (1) Within 2,000 flight hours since the last functional test of the cabin altitude pressure switches. (2) Prior to the accumulation of 2,000 total flight hours on the airplane. (3) Within 90 days after the effective date of this AD. Note 1 to paragraph (g): Additional guidance for performing the functional test required by paragraph (g) of this AD can be found in 737–200 Airplane Maintenance Manual (AMM) 21–33–11/501, 737CL AMM TASK CARD 31–026–01–01, 737CL AMM TASK CARD 31–010–01–01, 737NG AMM TASK CARD 31–020–00–01, and 737MAX AMM TASK CARD 31–020–00–01, and other approved maintenance procedures. (h) Reporting for Switch Failure If any switch fails the initial functional test required by paragraph (g) of this AD: At the applicable time specified in paragraph (h)(1) or (2) of this AD, report the results of that functional test, in accordance with Boeing Multi Operator Message MOM–MOM–21– 0292–01B, dated June 23, 2021. (1) If the functional test was done on or after the effective date of this AD: Submit the report within 10 days after the functional test. (2) If the functional test was done before the effective date of this AD: Submit the report within 10 days after the effective date of this AD. (i) Repetitive Reporting of Tested Fleet Within 40 days, but no earlier than 30 days, after the effective date of this AD: Send a report to Boeing listing the total number of airplanes, including tail numbers, in the operator’s fleet that have been tested since the effective date of this AD, in accordance with Boeing Multi Operator Message MOM– MOM–21–0292–01B, dated June 23, 2021. Thereafter, send a report for the number of airplanes tested, at intervals of 30 days for a total period of 12 months. A report is not required for any 30-day interval in which no airplanes were tested. (j) Exceptions to Service Information Specifications (1) Where Boeing Multi Operator Message MOM–MOM–21–0292–01B, dated June 23, 2021, refers to certain task cards for the functional test, that service information is not required by this AD, and any approved maintenance procedures are acceptable for the functional test. (2) Where Boeing Multi Operator Message MOM–MOM–21–0292–01B, dated June 23, 2021, specifies replacing failed switches with ‘‘new or serviceable’’ switches, this AD requires replacement with ‘‘serviceable’’ switches, which include any switches that are eligible for installation. (3) Where Boeing Multi Operator Message MOM–MOM–21–0292–01B, dated June 23, 2021, specifies the on-condition additional step of increasing the altitude to 20,000 feet if the cabin altitude warning does not activate by 11,000 feet, this AD requires that additional step only during the initial functional test. PO 00000 Frm 00009 Fmt 4700 Sfmt 4700 38217 (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 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 Related Information. Information may be emailed to 9-ANMSeattle-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 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. (l) Related Information For more information about this AD, contact Nicole Tsang, Aerospace Engineer, Cabin Safety and Environmental Systems Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax: 206–231–3959; email: Nicole.S.Tsang@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 Multi Operator Message MOM– MOM–21–0292–01B, dated June 23, 2021. (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/ibrlocations.html. E:\FR\FM\20JYR1.SGM 20JYR1 38218 Federal Register / Vol. 86, No. 136 / Tuesday, July 20, 2021 / Rules and Regulations Issued on July 2, 2021. Gaetano A. Sciortino, Deputy Director for Strategic Initiatives, Compliance & Airworthiness Division, Aircraft Certification Service. Fort Worth, TX 76177. For information on the availability of this material at the FAA, call (817) 222–5110. It is also available at https://www.regulations.gov by searching for and locating Docket No. FAA–2021–0348. [FR Doc. 2021–15391 Filed 7–15–21; 4:15 pm] BILLING CODE 4910–13–P Examining the AD Docket DEPARTMENT OF TRANSPORTATION Federal Aviation Administration 14 CFR Part 39 [Docket No. FAA–2021–0348; Project Identifier 2018–SW–076–AD; Amendment 39–21645; AD 2021–14–18] RIN 2120–AA64 Airworthiness Directives; Leonardo S.p.a. (Type Certificate Previously Held by Agusta S.p.A.) Helicopters Federal Aviation Administration (FAA), DOT. ACTION: Final rule. AGENCY: The FAA is superseding Airworthiness Directive (AD) 2011–18– 52 for certain Agusta S.p.A. (now Leonardo S.p.a.) Model AB139 and AW139 helicopters. AD 2011–18–52 required revising the life limit for certain part-numbered tail rotor (T/R) blades, updating the helicopter’s historical records, repetitively inspecting each T/R blade for a crack or damage, and depending on the results, replacing the T/R blade. This AD was prompted by the manufacturer developing improved T/R blades using different materials and establishing life limits for each improved blade. This AD retains certain requirements from AD 2011–18–52, revises certain requirements from AD 2011–18–52, and expands the applicability to include the newly-designed T/R blades. The FAA is issuing this AD to address the unsafe condition on these products. DATES: This AD is effective August 24, 2021. The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of August 24, 2021. ADDRESSES: For service information identified in this final rule, contact Leonardo S.p.A. Helicopters, Emanuele Bufano, Head of Airworthiness, Viale G.Agusta 520, 21017 C. Costa di Samarate (Va) Italy; telephone +39– 0331–225074; fax +39–0331–229046; or at https://www.leonardocompany.com/ en/home. You may view this service information at the FAA, Office of the Regional Counsel, Southwest Region, 10101 Hillwood Pkwy., Room 6N–321, khammond on DSKJM1Z7X2PROD with RULES SUMMARY: VerDate Sep<11>2014 15:59 Jul 19, 2021 Jkt 253001 You may examine the AD docket at https://www.regulations.gov by searching for and locating Docket No. FAA–2021–0348; 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, the European Aviation Safety Agency (now European Union Aviation Safety Agency) (EASA) AD, 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: Matt Fuller, AD Program Manager, General Aviation & Rotorcraft Unit, Airworthiness Products Section, Operational Safety Branch, FAA, 10101 Hillwood Pkwy., Fort Worth, TX 76177; telephone (817) 222–5110; email matthew.fuller@faa.gov. SUPPLEMENTARY INFORMATION: Background The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2011–18–52, Amendment 39–17020 (77 FR 23109, April 18, 2012) (AD 2011–18–52). AD 2011–18–52 applied to Agusta S.p.A. (now Leonardo S.p.a.) Model AB139 and AW139 helicopters with a T/R blade part number (P/N) 3G6410A00131 or P/N 4G6410A00131 installed. The NPRM published in the Federal Register on May 10, 2021 (86 FR 24780). AD 2011–18–52 required, within 5 hours time-in-service (TIS), establishing a life limit of 600 hours TIS or 1,500 takeoff and landing cycles (cycles), whichever occurs first, on the affected T/R blades and updating the helicopter’s historical records. If a T/R blade’s total number of cycles was unknown, determining the T/R blade cycles by multiplying the T/R blade’s hours TIS by 4 was required. For a T/ R blade that, on the effective date of AD 2011–18–52, had already exceeded 600 hours TIS or 1,500 cycles, the AD required replacing the T/R blade with an airworthy T/R blade within 5 hours TIS. AD 2011–18–52 also required, within 25 hours TIS, and thereafter at intervals not to exceed 25 hours TIS, inspecting PO 00000 Frm 00010 Fmt 4700 Sfmt 4700 the T/R blade for a crack or damage that exceeds the limits of the applicable maintenance manual. The inspection was required to be accomplished using a mirror, magnifying glass (5X or greater), and light source; or borescope. If there was a crack, or if there was damage that exceeded the limits of the applicable maintenance manual, AD 2011–18–52 required, before further flight, replacing the T/R blade with an airworthy T/R blade. AD 2011–18–52 was prompted by a fatal accident involving an Agusta Model AW139 helicopter, which may have been caused by cracks in a T/R blade. EASA, which is the Technical Agent for the Member States of the European Union, issued EASA Emergency AD 2011–0156–E, dated August 25, 2011 (EASA AD 2011–0156– E) to require repetitive inspections and reducing the life limit of the T/R blades. According to EASA, this condition, if not detected and corrected, could result in failure of a T/R blade and subsequent loss of control of the helicopter. After the FAA issued AD 2011–18–52, EASA issued a series of ADs as follows: • EASA AD 2012–0030, dated February 17, 2012 (EASA AD 2012– 0030), which superseded Emergency AD 2011–0156–E, advised that the manufacturer developed improved, newly-designed T/R blades P/N 3G6410A00132 and P/N 4G6410A00132, established life limits for each improved T/R blade, added repetitive inspections for the improved T/R blades, and advised that each T/R blade P/N had its own individual life limit. • EASA AD 2012–0076, dated May 2, 2012 (EASA AD 2012–0076), which superseded EASA AD 2012–0030 and was issued after the manufacturer developed another version of improved T/R blades P/N 3G6410A00133 and P/ N 4G6410A00133 with different materials. AD 2012–0076 required interim life limits for the new improved version of the T/R blades while also retaining the inspection requirements of EASA AD 2012–0030. • EASA AD 2012–0076R1, dated July 13, 2012 (EASA AD 2012–0076R1), which revised EASA AD 2012–0076 after a modification was developed to allow installation of certain partnumbered T/R blades under certain conditions. • EASA AD 2012–0076R2, dated February 20, 2014 (EASA AD 2012– 0076R2), which revised EASA AD 2012–0076R1, was issued after another modification was developed. EASA AD 2012–0076R2 requires removing the 25 hours TIS inspection of certain partnumbered T/R blades, extending the life E:\FR\FM\20JYR1.SGM 20JYR1

Agencies

[Federal Register Volume 86, Number 136 (Tuesday, July 20, 2021)]
[Rules and Regulations]
[Pages 38214-38218]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-15391]



[[Page 38214]]

-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0561; Project Identifier AD-2021-00623-T; 
Amendment 39-21647; AD 2021-14-20]
RIN 2120-AA64


Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule; request for comments.

-----------------------------------------------------------------------

SUMMARY: The FAA is adopting a new airworthiness directive (AD) for all 
The Boeing Company Model 737 airplanes. This AD was prompted by reports 
of latent failures of the cabin altitude pressure switches. This AD 
requires repetitive functional tests of the pressure switches, and on-
condition actions, including replacement, if necessary. The FAA is 
issuing this AD to address the unsafe condition on these products.

DATES: This AD is effective July 20, 2021.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of July 20, 
2021.
    The FAA must receive comments on this AD by September 3, 2021.

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 https://www.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.
    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 at https://www.regulations.gov 
by searching for and locating Docket No. FAA-2021-0561.

Examining the AD Docket

    You may examine the AD docket at https://www.regulations.gov by 
searching for and locating Docket No. FAA-2021-0561; 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 street address for Docket 
Operations is listed above.

FOR FURTHER INFORMATION CONTACT: Nicole Tsang, Aerospace Engineer, 
Cabin Safety and Environmental Systems Section, FAA, Seattle ACO 
Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax: 206-
231-3959; email: [email protected].

SUPPLEMENTARY INFORMATION:

Background

    The FAA requires every proposed transport category airplane design 
with a pressurized cabin to include a system that warns the flightcrew 
of cabin depressurization. 14 CFR 25.841(b). On Boeing Model 737 
airplanes, such warning systems include a cabin altitude pressure 
switch. The functions of this pressure switch are twofold: To detect if 
a certain cabin pressure altitude has been exceeded; and if so, to send 
a signal to the parts of the system that provide aural and visual 
warnings to the flightcrew. When this switch fails, it fails latently; 
that is, without making the failure known to the flightcrew or 
maintenance personnel. Due to the importance of the functions provided 
by this switch, in 2012 the FAA mandated that all Boeing Model 737 
airplanes utilize two switches, to provide redundancy in case of one 
switch's failure. AD 2012-19-11, Amendment 39-17206 (77 FR 60296, 
October 3, 2012).\1\
---------------------------------------------------------------------------

    \1\ This airworthiness directive was eventually superseded by AD 
2015-21-11, Amendment 39-18304 (80 FR 65927, October 28, 2015) (AD 
2015-21-11).
---------------------------------------------------------------------------

    The FAA has received reports of latent failures of these cabin 
altitude pressure switches. In September 2020, an operator reported 
that on three of its airplanes, both pressure switches failed the on-
wing functional test. The affected switches were on three different 
models of the Boeing 737.
    The airplane manufacturer investigated, and initially found, for 
reasons that included the expected failure rate of the switches, that 
it did not pose a safety issue. Boeing decided in November 2020 that 
the failures were not a safety issue. Subsequent investigation and 
analysis led the FAA and the airplane manufacturer to determine, in May 
of 2021, that the failure rate of both switches is much higher than 
initially estimated, and therefore does pose a safety issue.
    The FAA does not yet have sufficient information to determine what 
has caused this unexpectedly high failure rate, so a terminating 
corrective action cannot yet be developed. However, a latent failure of 
both pressure switches could result in the loss of cabin altitude 
warning, which could delay flightcrew recognition of a lack of cabin 
pressurization, and result in incapacitation of the flightcrew due to 
hypoxia (a lack of oxygen in the body), and consequent loss of control 
of the airplane. Therefore addressing these failures requires immediate 
action. The FAA is issuing this AD to address the unsafe condition on 
these products.

FAA's Determination

    The FAA is issuing this AD because the agency has determined the 
unsafe condition described previously is likely to exist or develop in 
other products of the same type design.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed Boeing Multi Operator Message MOM-MOM-21-0292-01B, 
dated June 23, 2021. This service information specifies procedures for 
repetitive functional tests of the cabin altitude pressure switches, 
on-condition actions including follow-on functional testing and 
replacement of failed switches, sending a report to Boeing about any 
pressure switches that fail the initial functional test, and reporting 
to Boeing the airplanes in the operator's fleet that have been tested. 
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.

AD Requirements

    This AD requires accomplishing the actions specified in the service 
information already described, except as discussed under ``Differences 
Between this AD and the Service Information.'' This AD also requires 
reporting to Boeing the results of the first functional test if any 
pressure switch failed, and sending reports to Boeing of the airplanes 
in the operator's fleet that have been tested.

[[Page 38215]]

Effect of Certain Installation Procedures on Accomplishment of AD 
Requirements

    As previously noted, the FAA issued AD 2015-21-11, applicable to 
certain Model 737-100, -200, -200C, -300, -400, -500, -600, -700, -
700C, -800, -900, and -900ER series airplanes. AD 2015-21-11 requires, 
among other actions, the installation of a redundant cabin altitude 
pressure switch in accordance with specified Boeing service 
information. The FAA has since approved numerous supplemental type 
certificates (STCs) and other means for installing the redundant 
pressure switch. As a result of its oversight of these newly-installed 
switches, the FAA has determined that use of approved maintenance 
procedures for the cabin altitude pressure switch functional test other 
than those specified in the task cards identified in Boeing Multi 
Operator Message MOM-MOM-21-0292-01B, dated June 23, 2021, is 
acceptable for the functional test; therefore, those other procedures 
do not require approval of an alternative method of compliance (AMOC).

Differences Between This AD and the Service Information

    Although Boeing Multi Operator Message MOM-MOM-21-0292-01B, dated 
June 23, 2021, affects ``all 737CL'' airplanes (the 737 Classics 
include Model 737-100, -200, -200C, -300, -400, and -500), Boeing did 
not send the MOM to Model 737-100, -200 and -200C operators. 
Additionally, Boeing did not reference procedures for performing the 
cabin altitude pressure switch functional test for Model 737-100, -200, 
and -200C series airplanes. There are no Model 737-100 series airplanes 
operating worldwide; however, the applicability of this AD includes 
those airplanes in the event any of those airplanes are returned to 
service in the U.S. The FAA has also included Model 737-200 and -200C 
series airplanes in the applicability of this AD. Furthermore, the FAA 
requested that Boeing make the service information available to Model 
737-200 and -200C operators. Boeing Model 737-200 and -200C operators 
may reference 737-200 Airplane Maintenance Manual (AMM) 21-33-11/501 
for additional guidance on performing the cabin altitude pressure 
switch functional test.
    Boeing Multi Operator Message MOM-MOM-21-0292-01B, dated June 23, 
2021, uses permissive language, such as ``recommends'' and 
``requesting,'' in its ``Functional Test Requirements'' and ``Reporting 
Requirements'' sections. However, the regulatory text in paragraphs (g) 
and (h) of this AD makes the language in those sections mandatory 
unless an exception in paragraph (j) of this AD applies.
    Boeing Multi Operator Message MOM-MOM-21-0292-01B, dated June 23, 
2021, recommends returning failed pressure switches to the switch 
manufacturer. Although the FAA also recommends that operators return 
failed pressure switches in order to provide the switch manufacturer 
with additional data related to the unsafe condition, this AD does not 
require that action.
    Although Boeing Multi Operator Message MOM-MOM-21-0292-01B, dated 
June 23, 2021, identifies specific AMM task cards for use in 
accomplishing the functional test, paragraph (j)(1) of this AD 
clarifies that any approved maintenance procedures may be used for the 
functional test. This provides the operator an option to use the AMM 
task card or any approved maintenance procedure for the functional test 
without needing to request an AMOC.
    Boeing Multi Operator Message MOM-MOM-21-0292-01B, dated June 23, 
2021, specifies certain on-condition actions, including an additional 
step while performing the functional test on the switch by increasing 
the altitude setting on the switch to an altitude of up to 20,000 feet 
if the cabin altitude warning does not activate by 11,000 feet during 
the initial functional test. The service information specifies 
repeating the functional test at intervals, but does not explicitly 
state that the on-condition additional functional testing is limited to 
the initial functional test only. Paragraph (j)(3) of this AD requires 
the on-condition additional functional test step of increasing the 
altitude setting to 20,000 feet only during the initial functional test 
(if applicable).
    Although Boeing Multi Operator Message MOM-MOM-21-0292-01B, dated 
June 23, 2021, specifies that failed switches be replaced with ``new or 
serviceable'' switches, this AD requires replacement with 
``serviceable'' switches, which include any switches that are eligible 
for installation. This is to ensure that any installed switch is 
serviceable.

Interim Action

    The FAA considers this AD to be an interim action. The reporting 
that is required by this AD will enable the airplane manufacturer to 
obtain better insight into the nature, cause, and extent of the switch 
failures, and eventually to develop final action to address the unsafe 
condition. Once final action has been identified, the FAA might 
consider further rulemaking.

Justification for Immediate Adoption and Determination of the Effective 
Date

    Section 553(b)(3)(B) of the Administrative Procedure Act (APA) (5 
U.S.C. 551 et seq.) authorizes agencies to dispense with notice and 
comment procedures for rules when the agency, for ``good cause,'' finds 
that those procedures are ``impracticable, unnecessary, or contrary to 
the public interest.'' Under this section, an agency, upon finding good 
cause, may issue a final rule without providing notice and seeking 
comment prior to issuance. Further, section 553(d) of the APA 
authorizes agencies to make rules effective in less than thirty days, 
upon a finding of good cause.
    An unsafe condition exists that requires the immediate adoption of 
this AD without providing an opportunity for public comments prior to 
adoption. The FAA has found that the risk to the flying public 
justifies forgoing notice and comment prior to adoption of this rule 
because, as previously noted, the unexpectedly high rate of latent 
failure, of both pressure switches on the same airplane, could result 
in the cabin altitude warning system not activating if the cabin 
altitude exceeds 10,000 feet, resulting in hypoxia of the flightcrew, 
and loss of control of the airplane. Accordingly, notice and 
opportunity for prior public comment are impracticable and contrary to 
the public interest pursuant to 5 U.S.C. 553(b)(3)(B).
    In addition, the FAA finds that good cause exists pursuant to 5 
U.S.C. 553(d) for making this amendment effective in less than 30 days, 
for the same reasons the FAA found good cause to forgo notice and 
comment.

Comments Invited

    The FAA invites you to send any written data, views, or arguments 
about this final rule. Send your comments to an address listed under 
ADDRESSES. Include Docket No. FAA-2021-0561 and Project Identifier AD-
2021-00623-T at the beginning of your comments. The most helpful 
comments reference a specific portion of the final rule, 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 final rule 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 
https://

[[Page 38216]]

www.regulations.gov, including any personal information you provide. 
The agency will also post a report summarizing each substantive verbal 
contact received about this final rule.

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 AD 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 AD, 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 AD. Submissions containing CBI should be sent to Nicole 
Tsang, Aerospace Engineer, Cabin Safety and Environmental Systems 
Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA 
98198; phone and fax: 206-231-3959; email: [email protected]. Any 
commentary that the FAA receives that is not specifically designated as 
CBI will be placed in the public docket for this rulemaking.

Regulatory Flexibility Act

    The requirements of the Regulatory Flexibility Act (RFA) do not 
apply when an agency finds good cause pursuant to 5 U.S.C. 553 to adopt 
a rule without prior notice and comment. Because the FAA has determined 
that it has good cause to adopt this rule without notice and comment, 
RFA analysis is not required.

Costs of Compliance

    The FAA estimates that this AD affects 2,502 airplanes of U.S. 
registry. The FAA estimates the following costs to comply with this AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
           Action                Labor cost       Parts cost      Cost per  product     Cost on U.S.  operators
----------------------------------------------------------------------------------------------------------------
Functional test............  1 work-hour x $85              $0  $85 per test........  $212,670 per test.
                              per hour = $85
                              per test.
----------------------------------------------------------------------------------------------------------------

    In addition, the FAA has determined that preparing and sending a 
monthly report of tested airplanes takes about 1 work-hour per 
operator. Since operators are required to submit this report for their 
affected fleet(s), the FAA has determined that a per-operator estimate 
is more appropriate than a per-airplane estimate. Therefore, the FAA 
estimates the average total cost of the monthly report to be $85 (1 
work-hour x $85) per report, per operator.
    The FAA estimates the following costs to do any necessary on-
condition actions that would be required based on the results of the 
functional test. The FAA has no way of determining the number of 
aircraft that might need these actions:

                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                   Action                                 Labor cost                Parts cost        product
----------------------------------------------------------------------------------------------------------------
On-condition functional test and switch      1 work-hour x $85 per hour = $85...          $1,278          $1,363
 replacement.
Reporting..................................  1 work-hour x $85 per hour = $85...               0              85
----------------------------------------------------------------------------------------------------------------

Paperwork Reduction Act

    A federal agency may not conduct or sponsor, and a person is not 
required to respond to, nor shall a person be subject to a penalty for 
failure to comply with a collection of information subject to the 
requirements of the Paperwork Reduction Act unless that collection of 
information displays a currently valid OMB Control Number. The OMB 
Control Number for this information collection is 2120-0056. Public 
reporting for this collection of information is estimated to be 
approximately 1 hour per response, including the time for reviewing 
instructions, searching existing data sources, gathering and 
maintaining the data needed, completing and reviewing the collection of 
information. All responses to this collection of information are 
mandatory. Send comments regarding this burden estimate or any other 
aspect of this collection of information, including suggestions for 
reducing this burden to: Information Collection Clearance Officer, 
Federal Aviation Administration, 10101 Hillwood Parkway, Fort Worth, TX 
76177-1524.

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, and
    (2) Will not affect intrastate aviation in Alaska.

[[Page 38217]]

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

0
1. The authority citation for part 39 continues to read as follows:

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


Sec.  39.13  [Amended]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive:

2021-14-20 The Boeing Company: Amendment 39-21647; Docket No. FAA-
2021-0561; Project Identifier AD-2021-00623-T.

(a) Effective Date

    This airworthiness directive (AD) is effective July 20, 2021.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to all The Boeing Company Model 737 airplanes, 
certificated in any category.

(d) Subject

    Air Transport Association (ATA) of America Code 21, Air 
conditioning.

(e) Unsafe Condition

    This AD was prompted by reports of latent failures of the cabin 
altitude pressure switches. The FAA is issuing this AD to address 
the unexpectedly high rate of latent failure of both pressure 
switches on the same airplane which could result in the cabin 
altitude warning system not activating if the cabin altitude exceeds 
10,000 feet, resulting in hypoxia of the flightcrew, and loss of 
control of the airplane.

(f) Compliance

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

(g) Repetitive Functional Tests

    Except as specified in paragraph (j) of this AD: At the latest 
of the times specified in paragraphs (g)(1) through (3) of this AD, 
perform the initial functional test of the cabin altitude pressure 
switches, and before further flight, do all applicable on-condition 
actions, in accordance with the ``Functional Test Requirements'' 
section of Boeing Multi Operator Message MOM-MOM-21-0292-01B, dated 
June 23, 2021. Repeat the functional test thereafter at intervals 
not to exceed 2,000 flight hours and do all applicable on condition 
actions before further flight.
    (1) Within 2,000 flight hours since the last functional test of 
the cabin altitude pressure switches.
    (2) Prior to the accumulation of 2,000 total flight hours on the 
airplane.
    (3) Within 90 days after the effective date of this AD.
    Note 1 to paragraph (g): Additional guidance for performing the 
functional test required by paragraph (g) of this AD can be found in 
737-200 Airplane Maintenance Manual (AMM) 21-33-11/501, 737CL AMM 
TASK CARD 31-026-01-01, 737CL AMM TASK CARD 31-010-01-01, 737NG AMM 
TASK CARD 31-020-00-01, and 737MAX AMM TASK CARD 31-020-00-01, and 
other approved maintenance procedures.

(h) Reporting for Switch Failure

    If any switch fails the initial functional test required by 
paragraph (g) of this AD: At the applicable time specified in 
paragraph (h)(1) or (2) of this AD, report the results of that 
functional test, in accordance with Boeing Multi Operator Message 
MOM-MOM-21-0292-01B, dated June 23, 2021.
    (1) If the functional test was done on or after the effective 
date of this AD: Submit the report within 10 days after the 
functional test.
    (2) If the functional test was done before the effective date of 
this AD: Submit the report within 10 days after the effective date 
of this AD.

(i) Repetitive Reporting of Tested Fleet

    Within 40 days, but no earlier than 30 days, after the effective 
date of this AD: Send a report to Boeing listing the total number of 
airplanes, including tail numbers, in the operator's fleet that have 
been tested since the effective date of this AD, in accordance with 
Boeing Multi Operator Message MOM-MOM-21-0292-01B, dated June 23, 
2021. Thereafter, send a report for the number of airplanes tested, 
at intervals of 30 days for a total period of 12 months. A report is 
not required for any 30-day interval in which no airplanes were 
tested.

(j) Exceptions to Service Information Specifications

    (1) Where Boeing Multi Operator Message MOM-MOM-21-0292-01B, 
dated June 23, 2021, refers to certain task cards for the functional 
test, that service information is not required by this AD, and any 
approved maintenance procedures are acceptable for the functional 
test.
    (2) Where Boeing Multi Operator Message MOM-MOM-21-0292-01B, 
dated June 23, 2021, specifies replacing failed switches with ``new 
or serviceable'' switches, this AD requires replacement with 
``serviceable'' switches, which include any switches that are 
eligible for installation.
    (3) Where Boeing Multi Operator Message MOM-MOM-21-0292-01B, 
dated June 23, 2021, specifies the on-condition additional step of 
increasing the altitude to 20,000 feet if the cabin altitude warning 
does not activate by 11,000 feet, this AD requires that additional 
step only during the initial functional test.

(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 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 Related Information. Information may be emailed to [email protected].
    (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.

(l) Related Information

    For more information about this AD, contact Nicole Tsang, 
Aerospace Engineer, Cabin Safety and Environmental Systems Section, 
FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA 98198; 
phone and fax: 206-231-3959; email: [email protected].

(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 Multi Operator Message MOM-MOM-21-0292-01B, dated 
June 23, 2021.
    (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 [email protected], or go to: https://www.archives.gov/federal-register/cfr/ibr-locations.html.


[[Page 38218]]


    Issued on July 2, 2021.
Gaetano A. Sciortino,
Deputy Director for Strategic Initiatives, Compliance & Airworthiness 
Division, Aircraft Certification Service.
[FR Doc. 2021-15391 Filed 7-15-21; 4:15 pm]
BILLING CODE 4910-13-P