[Federal Register Volume 87, Number 129 (Thursday, July 7, 2022)]
[Proposed Rules]
[Pages 40460-40464]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-13980]


 ========================================================================
 Proposed Rules
                                                 Federal Register
 ________________________________________________________________________
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 This section of the FEDERAL REGISTER contains notices to the public of 
 the proposed issuance of rules and regulations. The purpose of these 
 notices is to give interested persons an opportunity to participate in 
 the rule making prior to the adoption of the final rules.
 
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 

  Federal Register / Vol. 87, No. 129 / Thursday, July 7, 2022 / 
Proposed Rules  

[[Page 40460]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2022-0588; Project Identifier AD-2022-00114-T]
RIN 2120-AA64


Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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

SUMMARY: The FAA proposes to supersede Airworthiness Directive (AD) 
2021-14-20, which applies to all The Boeing Company Model 737 
airplanes. AD 2021-14-20 requires repetitive functional tests of the 
cabin altitude pressure switches, and on-condition actions, including 
replacement, if necessary. AD 2021-14-20 also requires reporting test 
results. Since the FAA issued AD 2021-14-20, data collected from the 
reports required by AD 2021-14-20 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 proposed 
AD would retain the repetitive functional tests and on-condition 
actions, and specify certain adapter requirements for the functional 
tests. The FAA is proposing this AD to address the unsafe condition on 
these products.

DATES: The FAA must receive comments on this proposed AD by August 22, 
2022.

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.

Examining the AD Docket

    You may examine the AD docket at https://www.regulations.gov by 
searching for and locating 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 NPRM, 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: 

Comments Invited

    The FAA invites you to send any written relevant data, views, or 
arguments about this proposal. Send your comments to an address listed 
under ADDRESSES. Include ``Docket No. FAA-2022-0588; Project Identifier 
AD-2022-00114-T'' at the beginning of your comments. The most helpful 
comments reference a specific portion of the proposal, explain the 
reason for any recommended change, and include supporting data. The FAA 
will consider all comments received by the closing date and may amend 
the proposal because of those comments.
    Except for Confidential Business Information (CBI) as described in 
the following paragraph, and other information as described in 14 CFR 
11.35, the FAA will post all comments received, without change, to 
https://www.regulations.gov, including any personal information you 
provide. The agency will also post a report summarizing each 
substantive verbal contact received about this proposed AD.

Confidential Business Information

    CBI is commercial or financial information that is both customarily 
and actually treated as private by its owner. Under the Freedom of 
Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public 
disclosure. If your comments responsive to this NPRM contain commercial 
or financial information that is customarily treated as private, that 
you actually treat as private, and that is relevant or responsive to 
this NPRM, it is important that you clearly designate the submitted 
comments as CBI. Please mark each page of your submission containing 
CBI as ``PROPIN.'' The FAA will treat such marked submissions as 
confidential under the FOIA, and they will not be placed in the public 
docket of this NPRM. Submissions containing CBI should be sent to 
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 which is 
not specifically designated as CBI will be placed in the public docket 
for this rulemaking.

Background

    The FAA issued AD 2021-14-20, Amendment 39-21647 (86 FR 38214, July 
20, 2021) (AD 2021-14-20), for all The Boeing Company Model 737 
airplanes. AD 2021-14-20 was prompted by reports of latent failures of 
the cabin altitude pressure switches. AD 2021-14-20 requires repetitive 
functional tests of the pressure switches, and on-condition actions, 
including replacement, if necessary. The agency issued AD 2021-14-20 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.

Actions Since AD 2021-14-20 Was Issued

    Since the FAA issued AD 2021-14-20, Boeing, Eaton Aerospace (the 
cabin altitude warning switch supplier) and the FAA analyzed data 
collected from the reports required by AD 2021-14-20. That data 
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.

[[Page 40461]]

For most of the switches that were tested by the supplier after failing 
a functional test, no fault was found in the switches. Instead, it was 
determined that if a test adapter not meeting certain criteria (threads 
having a full thread depth of no greater than 0.438 inches (1.113 cm) 
and an overall length less than 0.500 inches (1.270 cm)) is connected 
to the cabin altitude warning switch, false failures may occur during 
the functional test. Based on this analysis, Boeing revised its 
airplane maintenance manual (AMM) procedures, which provide guidance 
for performing the functional test, to specify criteria for the 
adapters and matching hoses (those that are 25 feet to 40 feet (7.62 to 
12.19 meters) long, with #4 AN fitting to the adapter and quick 
disconnect (if applicable) to the air data test set). The matching hose 
criteria ensures there is a connection between the pressure switch and 
the air data test set. The FAA determined that AD 2021-14-20 should be 
superseded to ensure the functional tests are performed using the 
correct adapters to avoid false failure results. In addition, the FAA 
determined that sufficient data has been received regarding the cause 
of the failures of the cabin altitude pressure switches. Therefore, the 
reporting required by AD 2021-14-20 is no longer needed. This proposed 
AD would therefore retain the repetitive functional tests and on-
condition actions, and specify certain adapter requirements for the 
functional tests.

FAA's Determination

    The FAA is issuing this NPRM after determining that the unsafe 
condition described previously is likely to exist or develop on other 
products of the same type design.

Proposed AD Requirements in This NPRM

    This proposed AD would retain certain requirements of AD 2021-14-
20. This proposed AD would continue to require repetitive functional 
tests of the pressure switches having part number 214C50-2, and on-
condition actions, including replacement, if necessary. This proposed 
AD would require using adapters and matching hoses meeting certain 
criteria when performing the functional tests, as specified in figure 1 
to paragraph (g) of this AD. This proposed AD would also eliminate the 
reporting required by AD 2021-14-20.

Effect of Certain Installation Procedures on Accomplishment of AD 
Requirements

    The FAA issued AD 2015-21-11, Amendment 39-18304 (80 FR 65927, 
October 28, 2015) (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 the task cards specified in 
Note 1 to paragraph (g) of this AD, is acceptable for the functional 
test, provided the adapter meets the criteria specified in paragraph 
(g) of this AD. Therefore, those other procedures do not require 
approval of an alternative method of compliance (AMOC).

Costs of Compliance

    The FAA estimates that this AD, if adopted as proposed, would 
affect 2,693 airplanes of U.S. registry. The FAA estimates the 
following costs to comply with this proposed AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                 Cost on U.S.
              Action                    Labor cost       Parts cost     Cost per product          operators
----------------------------------------------------------------------------------------------------------------
Functional test..................  1 work-hour x $85            * $  $85 per test..........  $228,905 per test.
                                    per hour = $85 per
                                    test.
----------------------------------------------------------------------------------------------------------------
* 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 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
----------------------------------------------------------------------------------------------------------------
Switch replacement...........................  1 work-hour x $85 per hour =             $1,278           $1,363
                                                $85.
----------------------------------------------------------------------------------------------------------------

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, Section 106, describes the 
authority of the FAA Administrator. Subtitle VII, Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    The FAA is issuing this rulemaking under the authority described in 
Subtitle VII, part A, subpart III, Section 44701, General requirements. 
Under that section, Congress charges the FAA with promoting safe flight 
of civil aircraft in air commerce by prescribing regulations for 
practices, methods, and procedures the Administrator finds necessary 
for safety in air commerce. This regulation is within the scope of that 
authority because it addresses an unsafe condition that is likely to 
exist or develop on products identified in this rulemaking action.

Regulatory Findings

    The FAA has determined that this proposed AD would not have 
federalism implications under Executive Order 13132. This proposed AD 
would not have a substantial direct effect on the States, on the 
relationship between the national Government and the States, or on the 
distribution of power and responsibilities among the various levels of 
government.

[[Page 40462]]

    For the reasons discussed above, I certify that the proposed 
regulation:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866,
    (2) Would not affect intrastate aviation in Alaska, and
    (3) Would not have a significant economic impact, positive or 
negative, on a substantial number of small entities under the criteria 
of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

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

The Proposed Amendment

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

PART 39--AIRWORTHINESS DIRECTIVES

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

The Boeing Company: Docket No. FAA-2022-0588; Project Identifier AD-
2022-00114-T.

(a) Comments Due Date

    The FAA must receive comments on this airworthiness directive 
(AD) action by August 22, 2022.

(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 inches (0.673 cm) X 7/16-20-
UNJF-3A and less than or equal to 0.438 inches (1.113 cm) X 7/16-20-
UNJF-3A for the flareless end; or
    (ii) Less than or equal to 0.5 inches (1.27 cm) total with 
greater than or equal to 0.265 inches (0.673 cm) X 7/16-20-UNJF-3A 
thread for AN4 flared end.
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[[Page 40463]]

[GRAPHIC] [TIFF OMITTED] TP07JY22.000


[[Page 40464]]


[GRAPHIC] [TIFF OMITTED] TP07JY22.001

    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) Minimum Equipment List 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 and fax: 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; internet https://www.myboeingfleet.com.

    Issued on May 16, 2022.
Gaetano A. Sciortino,
Deputy Director for Strategic Initiatives, Compliance & Airworthiness 
Division, Aircraft Certification Service.
[FR Doc. 2022-13980 Filed 7-6-22; 8:45 am]
BILLING CODE 4910-13-C


