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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]
RIN 2120-AA64
Airworthiness Directives; The Boeing Company Airplanes
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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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: Nicole.S.Tsang@faa.gov.
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:
Nicole.S.Tsang@faa.gov. 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.
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
|
Action
|
Labor cost
|
Parts cost
|
Cost per
product
|
Cost on
U.S. operators
|
| Functional test |
1 work-hour x $85 per hour =
$85 per test |
* $ |
$85 per test |
$228,905 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
|
Action
|
Labor cost
|
Parts cost
|
Cost per
product
|
| Switch replacement |
1 work-hour x $85 per hour =
$85 |
$1,278
|
$1,363
|
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.
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
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]
2. The FAA amends Sec. 39.13 by:
a. Removing Airworthiness Directive (AD) AD 2021-14-20, Amendment 39-
21647 (86 FR 38214, July 20, 2021), and
b. Adding the following new AD:
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