Proposed Rule2023-27099
Airworthiness Directives; The Boeing Company Airplanes
Primary source
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Published
December 12, 2023
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
The FAA proposes to adopt a new airworthiness directive (AD) for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This proposed AD was prompted by two engine fan blade-out (FBO) events that resulted in the separation of engine inlet cowl and fan cowl parts from the airplane. In one event, fan cowl parts damaged the fuselage, which caused loss of pressurization and subsequent emergency descent. This proposed AD would require replacing specified inlet cowl aft bulkhead fasteners for certain airplanes; for certain other airplanes, inspecting the inlet cowl aft bulkhead fastener and replacing the fasteners if rivets are found, and, for all airplanes, replacement of the crushable spacers used in the attachment of the inlet cowl to the engine fan case; or as an option, installing a serviceable inlet cowl. This proposed AD would also require revising the existing maintenance or inspection program, as applicable, to incorporate new airworthiness limitations. The FAA is proposing this AD to address the unsafe condition on these products.
Full Text
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<title>Federal Register, Volume 88 Issue 237 (Tuesday, December 12, 2023)</title>
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[Federal Register Volume 88, Number 237 (Tuesday, December 12, 2023)]
[Proposed Rules]
[Pages 86084-86088]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2023-27099]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2023-2236; Project Identifier AD-2023-00962-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 adopt a new airworthiness directive (AD)
for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and
-900ER series airplanes. This proposed AD was prompted by two engine
fan blade-out (FBO) events that resulted in the separation of engine
inlet cowl and fan cowl parts from the airplane. In one event, fan cowl
parts damaged the fuselage, which caused loss of pressurization and
subsequent emergency descent. This proposed AD would require replacing
specified inlet cowl aft bulkhead fasteners for certain airplanes; for
certain other airplanes, inspecting the inlet cowl aft bulkhead
fastener and replacing the fasteners if rivets are found, and, for all
airplanes, replacement of the crushable spacers used in the attachment
of the inlet cowl to the engine fan case; or as an option, installing a
serviceable inlet cowl. This proposed AD would also require revising
the existing maintenance or inspection program, as applicable, to
incorporate new airworthiness limitations. 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 January 26,
2024.
ADDRESSES: You may send comments, using the procedures found in 14 CFR
11.43 and 11.45, by any of the following methods:
<bullet> Federal eRulemaking Portal: Go to <a href="http://regulations.gov">regulations.gov</a>. Follow
the instructions for submitting comments.
<bullet> Fax: 202-493-2251.
<bullet> 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.
<bullet> Hand Delivery: Deliver to Mail address above between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
AD Docket: You may examine the AD docket at <a href="http://regulations.gov">regulations.gov</a> under
Docket No. FAA-2023-2236; 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.
Material Incorporated by Reference:
<bullet> For service information identified in this NPRM, 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 <a href="http://myboeingfleet.com">myboeingfleet.com</a>.
<bullet> 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
<a href="http://regulations.gov">regulations.gov</a> by searching for and locating Docket No. FAA-2023-2236.
FOR FURTHER INFORMATION CONTACT: Luis Cortez-Muniz, Aviation Safety
Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; telephone
206-231-3958; email: <a href="/cdn-cgi/l/email-protection#49253c203a6728672a263b3d2c3364243c272033092f2828672e263f"><span class="__cf_email__" data-cfemail="0b677e6278256a256864797f6e7126667e6562714b6d6a6a256c647d">[email protected]</span></a>.
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-2023-2236; Project Identifier
AD-2023-00962-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
this 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
<a href="http://regulations.gov">regulations.gov</a>, including any personal information you provide. The
agency will also post a report summarizing each substantive verbal
contact received about this NPRM.
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 Luis
Cortez-Muniz, Aviation Safety Engineer, FAA, 2200 South 216th St., Des
Moines, WA 98198; telephone 206-231-3958; email: <a href="/cdn-cgi/l/email-protection#7d1108140e531c531e120f0918075010081314073d1b1c1c531a120b"><span class="__cf_email__" data-cfemail="573b223e2479367934382523322d7a3a22393e2d1731363679303821">[email protected]</span></a>. Any commentary that the FAA receives that is not
specifically designated as CBI will be placed in the public docket for
this rulemaking.
Background
The FAA received two reports of engine events that resulted in the
separation of engine inlet cowl and fan cowl parts from the airplane.
One event occurred in August 2016 on a Boeing Model 737-700 series
airplane powered by a CFM56-7B engine. The left engine failed due to
the FBO but the airplane landed successfully. The second event occurred
on April 17, 2018, on a Boeing Model 737-700 series airplane powered by
a CFM56-7B engine. In that event, an FBO occurrence resulted in the
release of fan cowl parts and the engine cowling departing the
airplane. The fan cowl parts damaged the fuselage, which caused loss of
pressurization and subsequent emergency descent. Although the airplane
landed safely, there was one passenger fatality. In that event, the
suspected cause of the FBO occurrence was a low-cycle fatigue crack in
the dovetail of fan blade number 13 of engine number 1. The broken fan
blade hit the engine fan case at a critical location causing a
significant impulse, displacement, and
[[Page 86085]]
imbalance of the fan rotor effecting the structural integrity of the
engine cowling.
In response to these events, the FAA issued two AD actions for the
CFM International S.A. (CFM) Model CFM56-7B engines. The FAA issued
emergency AD 2018-09-51, Amendment 39-19287 (83 FR 23794, May 23, 2018)
(AD 2018-09-51), which requires a one-time ultrasonic inspection of the
concave and convex sides of the fan blade dovetail. The FAA also issued
AD 2018-26-01, Amendment 39-19531 (83 FR 66090, December 26, 2018) (AD
2018-26-01), which requires initial and repetitive inspections of the
concave and convex sides of the fan blade dovetail to detect cracking
and replacement of any blades found. The FAA issued AD 2018-09-51 to
address fan blade failure due to cracking, which could result in an
engine in-flight shutdown (IFSD), uncontained release of debris, damage
to the engine, damage to the airplane, and possible airplane
decompression. The FAA issued AD 2018-26-01 to address failure of the
fan blade, which could result in the engine inlet cowl disintegrating
and debris penetrating the fuselage, causing a loss of pressurization,
and prompting an emergency descent.
Since AD 2018-09-51 and AD 2018-26-01 were issued, the FAA has
determined further rulemaking is necessary to reduce the probability of
unsecured nacelle components, should an engine fan blade failure occur.
As evidenced by Exemption No. 19212, dated July 13, 2022 (Docket No.
FAA-2023-2236), Boeing developed modifications to the inlet cowl, fan
cowl, and exhaust nozzle that must be accomplished prior to July 31,
2028. Boeing petitioned and the FAA later agreed to amend Exemption No.
19212 to 19212A, which added a requirement that solutions to address
potential maintenance errors must be incorporated prior to December 31,
2029. However, to implement these design changes, the FAA must issue
rulemaking to address the unsafe condition.
This proposed AD would address inlet cowls that are not
strengthened, which could, in the event of an FBO occurrence, depart
the airplane potentially damaging the airframe structure, or the inlet
cowl could strike the fuselage and window. The unsafe condition, if not
addressed, could result in loss of control of the airplane, and hazard
to window-seated passengers aft of the wing. In addition, the unsafe
condition could result in significantly increased drag of the airplane,
which during an extended operations (ETOPS) flight, could lead to fuel
starvation and a forced off-airplane landing.
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.
Related Service Information Under 1 CFR Part 51
The FAA reviewed Boeing Special Attention Requirements Bulletin
737-71-1938 RB, dated July 27, 2023. This service information specifies
procedures to accomplish replacement of specified inlet cowl aft
bulkhead fasteners for certain airplanes; for certain other airplanes,
an inlet cowl aft bulkhead fastener inspection and fastener replacement
of the inlet cowl aft bulkhead fasteners if rivets are found, and, for
all airplanes, replacement of the crushable spacers used in the
attachment of the inlet cowl to the engine fan case for engine 1 and
engine 2; or as an option, installation of a serviceable inlet cowl
with new crushable spacers.
The service information also requires revision of the operator's
maintenance or inspection program, as applicable, by incorporating
certain airworthiness limitations (AWLs).
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 ADDRESSES.
Proposed AD Requirements in This NPRM
This proposed AD would require accomplishing the actions specified
in the service information already described, except as discussed under
``Differences Between this Proposed AD and the Service Information''
and except for any differences identified as exceptions in the
regulatory text of this proposed AD. For information on the procedures
and compliance times, see this service information at <a href="http://regulations.gov">regulations.gov</a>
under Docket No. FAA-2023-2236.
This proposed AD would require revisions to certain operator
maintenance documents to include new airworthiness limitations.
Compliance with these limitations is required by 14 CFR 91.403(c). For
airplanes that have been previously modified, altered, or repaired in
the areas addressed by this proposed AD, the operator may not be able
to accomplish the actions described in the revisions. In this
situation, to comply with 14 CFR 91.403(c), the operator must request
approval for an alternative method of compliance according to paragraph
(j) of this proposed AD.
Differences Between This Proposed AD and the Service Information
Boeing Special Attention Requirements Bulletin 737-71-1938 RB,
dated July 27, 2023, identifies ``System Airworthiness Limitation NO.
2--Fan Blade Out Conditions,'' and ``System Airworthiness Limitation
NO. 3--Fan Blade Out Conditions'' as the airworthiness limitations that
must be incorporated. In addition to those limitations, the FAA has
determined that ``System Airworthiness Limitation NO. 4--Engine Nacelle
Maintenance Errors'' must also be incorporated as specified in
paragraph (h) of this proposed AD. System Airworthiness Limitation NO.
4 specifically provides the limitation that mandates solutions to
maintenance errors that must be accomplished prior to December 31,
2029, as required by Exemption No. 19212A.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, would
affect 1,979 airplanes of U.S. registry. The FAA estimates the
following costs to comply with this proposed AD:
[[Page 86086]]
Estimated Costs
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Cost on U.S.
Action * Labor cost Parts cost Cost per product operators
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Inspection and fastener Up to 98 work-hours $922 Up to $9,252....... Up to $18,309,708.
replacement (for Config 1 x $85 per hour =
airplanes)/Fastener replacement $8,330.
(for Config 2 airplanes).
Crushable spacer replacement..... 16 work-hours x $85 14,878 $16,238............ $32,135,002.
per hour = $1,360.
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* The option to install a serviceable inlet cowl would cost up to $25,490 per product.
The FAA has determined that revising the existing maintenance or
inspection program takes an average of 90 work-hours per operator,
although the agency recognizes that this number may vary from operator
to operator. Since operators incorporate maintenance or inspection
program changes for their affected fleet(s), the FAA has determined
that a per-operator estimate is more accurate than a per-airplane
estimate. Therefore, the agency estimates the average total cost per
operator to be $7,650 (90 work-hours x $85 per work-hour).
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 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 this 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 adding the following new airworthiness
directive:
The Boeing Company: Docket No. FAA-2023-2236; Project Identifier AD-
2023-00962-T.
(a) Comments Due Date
The FAA must receive comments on this airworthiness directive
(AD) by January 26, 2024.
(b) Affected ADs
None.
(c) Applicability
This AD applies to all The Boeing Company Model 737-600, -700, -
700C, -800, -900, and -900ER series airplanes, certificated in any
category.
(d) Subject
Air Transport Association (ATA) of America Code 71, Powerplant.
(e) Unsafe Condition
This AD was prompted by two engine fan blade-out (FBO) events
that resulted in the separation of engine inlet cowl and fan cowl
parts from the airplane. In one event, fan cowl parts damaged the
fuselage, which caused loss of pressurization and subsequential
emergency descent. The FAA is issuing this AD to address inlet cowls
that are not strengthened, which, in the event of an FBO occurrence,
could depart the airplane potentially damaging the airframe
structure, or the inlet cowl could strike the fuselage and window.
The unsafe condition, if not addressed, could result in loss of
control of the airplane and hazard to window-seated passengers aft
of the wing. In addition, the unsafe condition could result in
significantly increased drag of the airplane, which during an
extended operations (ETOPS) flight, could lead to fuel starvation
and a forced off-airplane landing.
(f) Compliance
Comply with this AD within the compliance times specified,
unless already done.
(g) Required Actions
Except as specified by paragraph (h) of this AD: At the
applicable times specified in the ``Compliance'' paragraph of Boeing
Special Attention Requirements Bulletin 737-71-1938 RB, dated July
27, 2023, do all applicable actions identified in, and in accordance
with, the Accomplishment Instructions of Boeing Special Attention
Requirements Bulletin 737-71-1938 RB, dated July 27, 2023.
Note 1 to paragraph (g): Guidance for accomplishing the actions
required by this AD can be found in Boeing Special Attention Service
Bulletin 737-71-1938, dated July 27, 2023, which is referred to in
Boeing Special Attention Requirements Bulletin 737-71-1938 RB, dated
July 27, 2023.
(h) Exceptions to Service Information Specifications
Where Tables 1 through 4 of Boeing Special Attention
Requirements Bulletin 737-71-1938 RB, dated July 27, 2023, specify
incorporating 737-600/700/700C/800/900/900ER Airworthiness
Limitations (AWLs) document D626A001-9-01 ``System Airworthiness
Limitation NO. 2--Fan Blade Out Conditions'' and ``System
Airworthiness Limitation NO. 3--Fan Blade Out Conditions'' into the
operators maintenance program, this AD requires revising the
existing maintenance or inspection program, as applicable, by
incorporating the information specified in Figure 1 to the
introductory text of paragraph (h) of this AD into the airworthiness
limitations within 90 days after the effective date of this AD, or
within the applicable time specified in paragraph (h)(1) or (2) of
this AD, whichever occurs first.
[[Page 86087]]
Figure 1 to the Introductory Text of Paragraph (h)--System
Airworthiness Limitations
[GRAPHIC] [TIFF OMITTED] TP12DE23.001
(1) For Group 1 Configuration 1 airplanes identified in Boeing
Special Attention Requirements Bulletin 737-71-1938 RB, dated July
27, 2023: Before further flight after accomplishing the (Option 1)
or (Option 2) actions in Boeing Special Attention Requirements
Bulletin 737-71-1938 RB, dated July 27, 2023.
(2) For Group 1 Configuration 2 airplanes identified in Boeing
Special Attention Requirements Bulletin 737-71-1938 RB, dated July
27, 2023: Before further flight after accomplishing any of the
actions specified in paragraphs (h)(2)(i) and (ii) of this AD.
(i) The Condition 1 or Condition 2 actions specified in Boeing
Special Attention Requirements Bulletin 737-71-1938 RB, dated July
27, 2023.
(ii) The (Option 2) actions specified in Boeing Special
Attention Requirements Bulletin 737-71-1938 RB, dated July 27, 2023.
(i) No Alternative Actions
After the existing maintenance or inspection program has been
revised as required by paragraph (h) of this AD, no alternative
actions may be used unless the actions are approved as an
alternative method of compliance (AMOC) in accordance with the
procedures specified in paragraph (j) of this AD.
(j) Alternative Methods of Compliance (AMOCs)
(1) The Manager, AIR-520, Continued Operational Safety 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 (k)
of this AD. Information may be emailed to: <a href="/cdn-cgi/l/email-protection#794054383734542a1c180d0d151c54383a36543834363a542b1c080c1c0a0d0a391f1818571e160f"><span class="__cf_email__" data-cfemail="e5dcc8a4aba8c8b6808491918980c8a4a6aac8a4a8aaa6c8b780949080969196a5838484cb828a93">[email protected]</span></a>.
(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, AIR-
520, Continued Operational Safety 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.
(k) Related Information
For more information about this AD, contact Luis Cortez-Muniz,
Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA
98198; telephone 206-231-3958; email: <a href="/cdn-cgi/l/email-protection#d1bda4b8a2ffb0ffb2bea3a5b4abfcbca4bfb8ab91b7b0b0ffb6bea7"><span class="__cf_email__" data-cfemail="513d2438227f307f323e2325342b7c3c243f382b113730307f363e27">[email protected]</span></a>.
(l) Material Incorporated by Reference
(1) The Director of the Federal Register approved the
incorporation by reference (IBR) of the service information listed
in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.
(2) You must use this service information as applicable to do
the actions required by this AD, unless the AD specifies otherwise.
(i) Boeing Special Attention Requirements Bulletin 737-71-1938
RB, dated July 27, 2023.
(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; website <a href="http://myboeingfleet.com">myboeingfleet.com</a>.
(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 material at the National Archives and
Records Administration (NARA). For information on the availability
of this material at NARA, visit <a href="http://www.archives.gov/federal-register/cfr/ibr-locations">www.archives.gov/federal-register/cfr/ibr-locations</a> or email <a href="/cdn-cgi/l/email-protection#690f1b4700071a190c0a1d0006072907081b08470e061f"><span class="__cf_email__" data-cfemail="fe988cd097908d8e9b9d8a979190be909f8c9fd0999188">[email protected]</span></a>.
[[Page 86088]]
Issued on December 4, 2023.
Victor Wicklund,
Deputy Director, Compliance & Airworthiness Division, Aircraft
Certification Service.
[FR Doc. 2023-27099 Filed 12-11-23; 8:45 am]
BILLING CODE 4910-13-P
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