[Federal Register Volume 87, Number 245 (Thursday, December 22, 2022)]
[Rules and Regulations]
[Pages 78538-78542]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-27805]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2022-0588; Project Identifier AD-2022-00114-T; 
Amendment 39-22249; AD 2022-24-09]
RIN 2120-AA64


Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is superseding Airworthiness Directive (AD) 2021-14-
20, which applied to all The Boeing Company Model 737 airplanes. AD 
2021-14-20 required repetitive functional tests of the cabin altitude 
pressure switches, and on-condition actions, including replacement, if 
necessary. AD 2021-14-20 also required reporting test results. This AD 
was prompted by data collected from the reports required by AD 2021-14-
20, which revealed that the switches were subject to false test 
failures due to lack of clear instructions for setup of the test 
adapters during the functional tests. This AD retains the repetitive 
functional tests and on-condition actions, and specifies certain 
adapter requirements for the functional tests. The FAA is issuing this 
AD to address the unsafe condition on these products.

DATES: This AD is effective January 26, 2023.

ADDRESSES: 
    AD Docket: You may examine the AD docket at regulations.gov under 
Docket No. FAA-2022-0588; 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: Nicole Tsang, Aerospace Engineer, 
Cabin Safety and Environmental Systems Section, FAA, Seattle ACO 
Branch, 2200 South 216th St., Des Moines, WA 98198; phone: 206-231-
3959; email: [email protected].

SUPPLEMENTARY INFORMATION:

Background

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 to supersede AD 2021-14-20, Amendment 39-21647 (86 FR 
38214, July 20, 2021) (AD 2021-14-20). AD 2021-14-20 applied to all The 
Boeing Company Model 737 airplanes. The NPRM published in the Federal 
Register on July 7, 2022 (87 FR 40460). The NPRM was prompted by 
reports of latent failures of the cabin altitude pressure switches, and 
the determination that using certain adapters while performing a 
functional test may lead to false failures of the cabin altitude 
pressure switches. In the NPRM, the FAA proposed to retain the 
repetitive functional tests and on-condition actions, and specify 
certain adapter requirements for the functional tests. 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.

Discussion of Final Airworthiness Directive

Comments

    The FAA received a comment from the Air Line Pilots Association 
(ALPA), who supported the NPRM without change.
    The FAA received additional comments from four commenters, 
including United Airlines, Delta Air Lines, American Airlines, and 
Boeing. The following presents the comments received on the NPRM and 
the FAA's response to each comment.

Request To Revise Note 1 to Paragraph (g)

    Delta Air Lines (DAL) asked that the FAA revise note 1 to paragraph 
(g) of the proposed AD to call out equivalent applicable Boeing 737 
Aircraft Maintenance Manual (AMM) procedures, in addition to calling 
out the procedures in the 737 Task Card. DAL stated that the 737 Task 
Cards called out in Note 1 to paragraph (g) of the proposed AD are not 
easily accessible to the maintenance personnel performing the tasks on 
the aircraft. DAL added that the AMM procedure is more commonly used 
and easily accessed by the Aircraft Maintenance Technician, so the 
addition of the reference to the AMM procedure avoids potential 
confusion when the maintenance task is being performed.
    The FAA agrees with the commenter's request for the reasons 
provided. The FAA has revised Note 1 to paragraph (g) of this AD to 
include the equivalent

[[Page 78539]]

applicable Boeing 737 Aircraft Maintenance Manual procedures referenced 
in Delta's comment.

Request To Correct Typographical Error

    DAL noted that Boeing 737-600/700/800/900 Aircraft Maintenance 
Manual (AMM) is identified in note 1 to paragraph (g) of the proposed 
AD as ``Airplane Maintenance Manual'' instead of ``Aircraft Maintenance 
Manual.''
    The FAA has corrected the reference accordingly.

Request To Return to MRB Interval

    United Airlines (UAL) asked that the interval established in the 
Maintenance Review Board (MRB) be eventually re-established. UAL stated 
that tooling was determined to be a significant contributor to 
inconsistencies in the testing of the cabin altitude test switch. UAL 
added that AD 2021-14-20 would be superseded by the proposed AD to 
require improved AMM content defining appropriate tooling. In light of 
these published AMM improvements, UAL recommended a return to the 
interval established in the MRB.
    The FAA does not agree with the commenter's request. Boeing 
provided the fleet data collected from AD 2021-14-20 and the trend data 
after operators incorporated the improved AMM content. The FAA 
evaluated this data and determined through risk analysis that the 
interval established in the MRB was unacceptable. Therefore, the FAA 
has not changed this AD in this regard.

Request To Remove Hose Length Requirement

    American Airlines (AA) stated that the FAA should remove the hose 
length requirement of ``25 to 40 ft'' specified in figure 1 to 
paragraph (g) of the proposed AD. AA stated that the hose length 
requirement is an unnecessary restriction. AA added that a longer or 
shorter hose should not significantly affect the application of a 
controlled vacuum, and therefore should not affect the accuracy of the 
cabin altitude pressure switch functional test.
    The FAA does not agree with the commenter's request. There are 
instructions to use a Barfield Pitot Hose, or equivalent 25- to 40-foot 
hose, to standardize the equipment that operators use while performing 
the cabin altitude warning switch functional test and to prevent false 
test failures. There is potential concern that a hose longer than 40 
feet could have a kink in the hose that may be unnoticed by the 
operator, which could result in a false test failure. The FAA has not 
changed this AD in this regard.

Request To Use Specific Adapters for Functional Test

    Boeing asked that the proposed AD not specify particular adapters 
for use during performance of the pressure switch functional test. 
Boeing stated that the proposed AD should instead direct operators to 
use only those adapters listed in the current Boeing AMM revision or 
subsequent revisions. Boeing added that if new or improved adapters 
become available and/or the AMM adapter list is modified, an 
alternative method of compliance (AMOC) will have to be approved to add 
them as approved adapters for the AD, which is not an efficient 
resolution.
    The FAA does not agree to require operators to use only those 
adapters listed in the existing Boeing AMM revision or subsequent 
revisions. Figure 1 to paragraph (g) of this AD shows the same list of 
adapters identified in the current Boeing AMM. Approval of an AMOC to 
use new or improved adapters would not be necessary if the adapters 
meet the specifications in either paragraph (g)(2)(i) or (ii) of this 
AD. Therefore, the FAA has not changed this AD in this regard.

Conclusion

    The FAA reviewed the relevant data, considered any comments 
received, and determined that air safety requires adopting this AD as 
proposed. Accordingly, the FAA is issuing this AD to address the unsafe 
condition on these products. Except for minor editorial changes, and 
any other changes described previously, this AD is adopted as proposed 
in the NPRM. None of the changes will increase the economic burden on 
any operator.

Costs of Compliance

    The FAA estimates that this AD affects 2,693 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 per test.........  $228,905 per test.
                                $85 per hour =
                                $85 per test.
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* If the operator needs to buy an adapter, the FAA estimates the adapter could cost up to $3,644. The FAA has no
  way of determining the number of operators that might need to purchase an adapter.

    The FAA estimates the following costs to do any necessary on-
condition actions 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
----------------------------------------------------------------------------------------------------------------
Switch replacement...........................  1 work-hour x $85 per hour =             $1,278           $1,363
                                                $85.
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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

[[Page 78540]]

necessary for safety in air commerce. This regulation is within the 
scope of that authority because it addresses an unsafe condition that 
is likely to exist or develop on products identified in this rulemaking 
action.

Regulatory Findings

    This AD will not have federalism implications under Executive Order 
13132. This AD will not have a substantial direct effect on the States, 
on the relationship between the national government and the States, or 
on the distribution of power and responsibilities among the various 
levels of government.
    For the reasons discussed above, I certify that this AD:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866,
    (2) Will not affect intrastate aviation in Alaska, and
    (3) Will not have a significant economic impact, positive or 
negative, on a substantial number of small entities under the criteria 
of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

The Amendment

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

PART 39--AIRWORTHINESS DIRECTIVES

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:
0
a. Removing Airworthiness (AD) 2021-14-20, Amendment 39-21647 (86 FR 
38214, July 20, 2021); and
0
b. Adding the following new AD:

2022-24-09 The Boeing Company: Amendment 39-22249; Docket No. FAA-
2022-0588; Project Identifier AD-2022-00114-T.

(a) Effective Date

    This airworthiness directive (AD) is effective January 26, 2023.

(b) Affected ADs

    This AD replaces AD 2021-14-20, Amendment 39-21647 (86 FR 38214, 
July 20, 2021) (AD 2021-14-20).

(c) Applicability

    This AD applies to all The Boeing Company Model 737-100, -200, -
200C, -300, -400, -500, -600, -700, -700C, -800, -900, and -900ER 
series airplanes, and Model 737-8, 737-9, and 737-8200 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, and the determination that using certain 
adapters while performing a functional test may lead to false 
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

    (1) At the latest of the times specified in paragraphs (g)(1)(i) 
through (iii) of this AD, perform a functional test of the cabin 
altitude pressure switches having part number 214C50-2, using an 
adapter as specified in figure 1 to paragraph (g) of this AD, or an 
equivalent adapter, and matching hose to connect to the cabin 
altitude warning switch. Repeat the functional test thereafter at 
intervals not to exceed 2,000 flight hours. If, during any 
functional test, any cabin altitude pressure switch fails to 
activate at an altitude of between 9,000 and 11,000 feet, replace 
the switch before further flight.
    (i) Within 2,000 flight hours since the last functional test of 
the cabin altitude pressure switches.
    (ii) Prior to the accumulation of 2,000 total flight hours on 
the airplane.
    (iii) Within 90 days after the effective date of this AD.
    (2) Adapters are considered to be equivalent as long as the 
mating side with the switch meets the specifications in either 
paragraph (g)(2)(i) or (ii) of this AD:
    (i) Greater than or equal to 0.265 inch (0.673 cm) X 7/16-20-
UNJF-3A and less than or equal to 0.438 inch (1.113 cm) X 7/16-20-
UNJF-3A for the flareless end; or
    (ii) Less than or equal to 0.5 inch (1.27 cm) total with greater 
than or equal to 0.265 inch (0.673 cm) X 7/16-20-UNJF-3A thread for 
AN4 flared end.
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    Note 1 to paragraph (g): Additional guidance for performing the 
functional test required by paragraph (g) of this AD can be found in 
Boeing 737-200 Aircraft Maintenance Manual (AMM) 21-33-11/501, 
Boeing 737-300/400/500/600/700/800/900/7/8/8200/9 AMM 21-33-00/501, 
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) Minimum Equipment List (MEL) Provisions

    If any cabin altitude warning switch fails any functional test 
as required by this AD, the airplane may be operated as specified in 
the operator's existing FAA-approved MEL, provided provisions that 
specify operating the airplane at a flight altitude at or below 
10,000 feet mean sea level (MSL) with the cabin altitude warning 
system inoperative are included in the operator's existing FAA-
approved MEL.

(i) Alternative Methods of Compliance (AMOCs)

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

(j) Related Information

    (1) 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: 206-231-3959; email: [email protected].
    (2) For service information identified in this AD that is not 
incorporated by reference, 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; website myboeingfleet.com.

(k) Material Incorporated by Reference

    None.

    Issued on December 2, 2022.
Christina Underwood,
Acting Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2022-27805 Filed 12-21-22; 8:45 am]
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