DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2022-0891; Project Identifier AD-2022-00585-A,E,R;
Amendment 39-22432; AD 2023-09-09]
RIN 2120-AA64

Airworthiness Directives; Various Airplanes, Helicopters, and Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
turbocharged, reciprocating engine-powered airplanes and helicopters
and turbocharged, reciprocating engines with a certain v-band coupling
installed. This AD was prompted by multiple failures of spot-welded,
multi-segment v-band couplings at the tailpipe to the turbocharger
exhaust housing flange (also referred to as ``spot-welded, multi-
segment exhaust tailpipe v-band coupling''). This AD establishes a life
limit for the spot-welded, multi-segment exhaust tailpipe v-band
coupling and requires repetitively inspecting the spot-welded, multi-
segment exhaust tailpipe v-band coupling. The FAA is issuing this AD to
address the unsafe condition on these products.

DATES: This AD is effective July 17, 2023.

ADDRESSES: AD Docket: You may examine the AD docket at regulations.gov
by searching for and locating Docket No. FAA-2022-0891; 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: Thomas Teplik, Aviation Safety
Engineer, Central Certification Branch, FAA, 1801 S Airport Road,
Wichita, KS 67209; phone: (316) 946-4196; email: thomas.teplik@faa.gov
or Wichita-COS@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to turbocharged,
reciprocating engine-powered airplanes and helicopters and
turbocharged, reciprocating engines with a certain v-band coupling
installed. The NPRM published in the Federal Register on July 27, 2022
(87 FR 45036). The NPRM was prompted by multiple failures of spot-
welded, multi-segment v-band couplings at the tailpipe to the
turbocharger exhaust housing flange. In the NPRM, the FAA proposed to
establish a life limit for the spot-welded, multi-segment exhaust
tailpipe v-band coupling and require repetitively inspecting the spot-
welded, multi-segment exhaust tailpipe v-band coupling.
Since the mid-1970s, failures of v-band couplings that attach the
exhaust tailpipe to the turbocharger exhaust outlet have resulted in a
significant number of incidents and accidents (fatal and non-fatal) on
both airplanes and helicopters. Since 1974, National Transportation
Safety Board (NTSB) accident and incident investigations have led to
the issuance of 7 NTSB Safety Recommendations concerning exhaust
systems and/or exhaust v-band couplings; 20 FAA ADs to address the
unsafe condition with exhaust systems and/or exhaust v-band couplings;
and 10 FAA Special Airworthiness Information Bulletins (SAIBs).
Industry has also taken action to raise awareness of the concerns
associated with v-band coupling failures.

NTSB Safety Recommendations Affecting V-Band Couplings

You may examine these NTSB Safety Recommendations in the AD docket
at regulations.gov by searching for and locating Docket No. FAA-2022-
0891.

ADs on V-Band Couplings

These ADs require v-band coupling replacements (life limit) and/or
repetitive inspections, or changing the type design of the v-band
coupling. This AD does not apply to airplanes that have complied with
one of these ADs. You may examine these ADs in the AD docket at
regulations.gov by searching for and locating Docket No. FAA-2022-0891.

SAIBs on V-Band Couplings

You may examine these SAIBs in the AD docket at regulations.gov by
searching for and locating Docket No. FAA-2022-0891.
In spite of these efforts, failures continue to occur and the
number of significant safety events continues to increase. As a result,
the General Aviation Joint Steering Committee (GA-JSC), which is
comprised of both the FAA and industry, developed a working group to
study v-band coupling failures associated with turbocharged reciprocating
engine-powered aircraft and develop recommended corrective actions. This
v-band coupling working group was comprised of aviation industry manufacturers,
type/user groups, and government entities. The working group was tasked to
examine the turbocharger to tailpipe interface and develop
recommendations to enhance the safety of the fleet.
The working group recommended mandatory corrective actions that are
tailored to each specific coupling type (spot-welded, riveted, or
single piece), thereby minimizing the impact to owner/operators. The
working group recommended a mandatory coupling replacement time (life
limit) and annual inspection. The working group also recommended non-
mandatory actions to aid and educate maintenance personnel in
appropriate v-band coupling removal, installation, and inspection
practices. Finally, the working group recommended actions for new
designs, which incorporate lessons learned from review of the in-
service fleet. For new designs incorporating a v-band coupling
immediately downstream of the turbocharger exhaust discharge, the
working group recommended that a replacement interval (500 hours for
spot-welded and 2,000 hours for riveted and single-piece) be
incorporated in the Airworthiness Limitations sections of the
maintenance manual.
In January 2018, the working group published a final report titled
``Exhaust System Turbocharger to Tailpipe V-band Coupling/Clamp Working
Group Final Report'' (final report). Appendix B of the final report
contains the Best Practices Guide. The final report may be found in the
AD docket at regulations.gov by searching for and locating Docket No.
FAA-2022-0891.
The final report concluded that the common denominator in the
incidents and accidents reviewed is the spot-welded, multi-segment
exhaust tailpipe v-band coupling (see Figure A). These couplings come
in either two or three segment varieties. The segments are the number
of v-retainer segments, which are attached to the outer band via spot
welds. Although multi-segment exhaust tailpipe couplings can also be
riveted, the riveted couplings do not create an unsafe condition.

ILLUSTRATION (Figure A)

The majority of the events studied by the working group indicated
fatigue failure of spot-welded, multi-segment exhaust tailpipe v-band
couplings as a result of stress corrosion cracking that originated at
or near a spot weld. This is the same unsafe condition identified in
the other v-band coupling AD actions previously referenced. The data
studied by the working group contained evidence of pre-existing
cracking of the couplings, known embrittlement at the
spot weld locations simply due to that manufacturing method, and outer
band cupping on the multi-segment couplings (which is the result of
age, over-use, and potential over-torqueing). The working group also
found that many of the couplings had safety wire across the bolt end.
The safety wire could be helpful if there was a bolt or nut failure
(extremely rare events) or the nut was missing. However, the safety
wire was of no value when the failure was transverse band cracking and
total separation at the spot weld. The data studied by the working
group indicated many accidents were due to v-band couplings that were
of the multi-segment, spot-welded design, when used in a specific
location (the tailpipe to the turbocharger exhaust housing flange on
turbocharged reciprocating engine-powered aircraft).
After the working group published the final report, the FAA issued
SAIB CE-18-21, dated July 13, 2018. This SAIB announced the
availability of the Best Practices Guide from the final report and
recommended the public apply the best practices in the maintenance of
turbocharged reciprocating engine powered aircraft. The FAA also
assessed the recommendations contained in the final report and
determined an unsafe condition exists in turbocharged reciprocating
engine-powered aircraft with a spot-welded, multi-segment v-band
coupling installed. Because these v-band couplings are widely used by
many design approval holders on various models (engines and aircraft),
several Aircraft Certification Office Branches were involved in the
decision to propose a single AD. The FAA also determined that the
corrective actions recommended in the final report were appropriate to
address this unsafe condition.
This condition, if not addressed, could lead to failure of the
spot-welded, multi-segment exhaust tailpipe v-band coupling, leading to
detachment of the exhaust tailpipe from the turbocharger and allowing
high-temperature exhaust gases to enter the engine compartment. This
could result in smoke in the cockpit, in-flight fire, and loss of
control of the aircraft. The FAA is issuing this AD to address the
unsafe condition on these products.

Discussion of Final Airworthiness Directive

Comments

The FAA received comments from 32 commenters. The commenters were
Aerostar Aircraft Corporation (Aerostar), European Union Aviation
Safety Agency (EASA), NTSB, Vulcanair S.p.A, and 28 individuals. The
NTSB and four individual commenters supported the AD without change.
Aerostar, EASA, Vulcanair S.p.A., and 19 individual commenters do not
necessarily oppose the NPRM but recommended certain changes. Five
individual commenters oppose the proposal in its entirety. The
following presents the comments received on the NPRM and the FAA's
response to each comment.

A. Requests Regarding Withdrawing the NPRM

Three individual commenters stated that current inspections are
adequate and implied that they opposed the NPRM. Two other individual
commenters stated that they opposed the NPRM. One of the commentors
implied current inspections were sufficient and stated inspections of
the v-band clamp at each oil change and on-condition replacement would
be enough. One of the commenters who opposed the NPRM in its entirety
also requested that information regarding exhaust couplers be added to
FAA Advisory Circular (AC) 43.13-1B, Acceptable Methods, Techniques,
and Practices--Aircraft Inspection and Repair, dated September 8, 1998
(AC 43.13-1B). The FAA infers that these commenters are requesting that
the NPRM be withdrawn.
The FAA disagrees. This AD requires specific inspections that are
not included in current inspections. The accident and incident failure
data and existing ADs that are included in paragraphs (d) (1) through
(10) of this AD demonstrate that a 500-hour time-in-service (TIS) life
limit is appropriate for this type of multi-segment coupling. Regarding
the request to revise AC 43.13-1B, that change is outside the scope of
this AD and actions in an advisory circular provide guidance but are
not mandatory.
The FAA has not changed this AD as a result of these comments.

B. Requests Regarding Estimated Costs

1. Increase Work-Hour Rate
Three individual commenters requested that the FAA increase the
cost per work-hour specified in the NPRM. These commenters stated that
$85 per work-hour is too low and does not reflect the true rate charged
by their local maintenance facilities, which ranges from $100 to $140
per work-hour. One of these commenters also reported that the estimated
records review rate of $42.50 was not supported by industry practice
and should be increased.
The FAA disagrees. The FAA Office of Aviation Policy and Plans
provides the labor rate of $85 per work-hour used when estimating the
labor costs for complying with AD requirements. The estimate for the
records review rate was based on \1/2\ hour at $85 per work-hour.
The FAA has not changed this AD as a result of these comments.

2. Increase V-Band Coupling Removal and Replacement Costs

Two individual commenters requested changes regarding the estimated
costs in the NPRM for removal and replacement of v-band couplings. One
of those commenters stated that there could be a discrepancy in the
estimated costs per owner/operator. This commenter stated that the
estimated figures did not appear to be unduly expensive in the interest
of preventing a potential in-flight fire. The FAA infers that this
commenter is requesting a revision to the estimated costs for removal
and replacement of a v-band coupling based on the requested review of
the cost estimates.
The other individual commenter encouraged the FAA to increase the
estimated cost in the NPRM for replacement of a v-band coupling and
provided a cost of over $700 for the Piper Model PA-28R-201 airplane v-
band coupling. The FAA infers that the commenter is referring to the
estimated parts cost of $400 for a single-engine aircraft.
The FAA acknowledges that there may be discrepancies in the
estimated costs among owners/operators for removing and replacing a v-
band coupling. The FAA's estimated number of work-hours were based on
the actions required in AD 2018-06-11 and the parts costs were based on
current pricing. Additional labor and parts costs were added for twin-
engine aircraft. In the NPRM, the FAA estimated costs in single-engine
and twin-engine aircraft. The FAA disagrees that the cost of the v-band
coupling needs to be increased. The estimated v-band coupling cost of
$400 for a single-engine aircraft was based on a sampling of a range of
parts costs for different aircraft. The FAA determined that $400 was an
accurate parts cost for a single-engine aircraft.
The FAA has not changed this AD as a result of these comments.

C. Requests Regarding Life Limit

1. Clarification of Mitigation for Installation of a V-Band Coupling
That Exceeds 500-Hours TIS
EASA suggested that there should be a mitigation of risk in place
if a v-band coupling having 500 or more hours TIS
as of the effective date of the final rule is installed on an aircraft.
EASA noted that paragraph (l)(1) of the proposed AD would allow the
installation of a used v-band coupling of any age (i.e., more than 500
hours TIS) within the first two years after the effective date of the
final rule. EASA asked if requiring the repetitive inspections
specified in paragraph (i)(2) of the proposed AD would mitigate this
risk or, alternatively, if there should be a prohibition of the
installation of a v-band coupling that has accumulated 500 or more
hours TIS as of the effective date of the final rule.
The FAA does not agree. The FAA provides mitigation for the risk
associated with installing a v-band coupling having 500 or more hours
TIS by requiring inspections every 6 months or every 100 hours TIS,
whichever occurs first, for two years after the effective date of this
AD. The inspections and inspection criteria are the same for the v-band
couplings regardless of the inspection time interval. Paragraph (i)(2)
of this AD was provided to allow compliance with the requirements of
this AD with regards to hardware availability.
2. Justification for 500-Hour TIS Life Limit
An anonymous commenter requested justification for the v-band
coupling 500-hour TIS life limit specified in the NPRM and stated that
the 500-hour TIS life limit seemed low. In regards to the study of
accident rates where failure of the v-band coupling was determined to
be at fault, the commenter asked how many hours the v-band coupling had
accumulated since its initial installation. The commenter also inquired
about the failure rate of higher grade material v-band couplings and
asked if higher grade v-band coupling material would have an effect on
the failure rate.
The FAA determined the 500-hour TIS v-band coupling replacement
time is necessary to correct the unsafe condition. The FAA based this
determination on past precedence of some of the existing ADs that are
included in paragraphs (d)(1) through (10) of this AD. The v-band
couplings addressed in this AD are of similar steel material. The FAA
has an obligation to issue an AD to address an unsafe condition. This
AD addresses the unsafe condition through repetitive inspections and
replacements. The FAA would consider any future design improvements as
an AMOC following the procedures outlined in paragraph (n) of this AD.
The FAA has not changed this AD in regard to this comment.
3. Replacement of V-Band Coupling Solely Based on Hours TIS
Two commenters did not agree with the replacement of the v-band
coupling based solely on flight hours (v-band coupling hours TIS). One
commenter asserted the inspections specified in the proposed AD were
adequate to uncover defects that would require replacing a v-band
coupling and stated if a v-band clamp continuously passes inspection,
there is no reason to discard it based on TIS. The other commenter
stated that v-band couplings on its helicopters are already inspected
for cracking, and the surrounding area is inspected for signs of
cracking or soot, as part of pre-flight inspections. This commenter
also stated that Enstrom Helicopter Corporation issued Service
Directive Bulletin 0122 (Enstrom SDB 0122) that addresses inspections
for cracks.
The FAA disagrees with removing the requirement in paragraph (i) of
this AD to replace a v-band coupling before it accumulates 500 hours
TIS and instead allowing on-condition replacement based upon inspection
results. The accident/incident failure rate and existing ADs that are
included in paragraphs (d)(1) through (10) of this AD demonstrate that
a 500-hour TIS life limit is appropriate for this type of multi-segment
v-band coupling. Regarding Enstrom SDB 0122, the FAA has not issued an
AD that mandates using that service information.
The FAA has not changed this AD in regard to these comments.

D. Requests Regarding V-Band Coupling Serialization

Two individual commenters recommended serialization of the v-band
coupling.
One of those commenters stated it would be difficult to determine
the total hours TIS unless these parts are serialized. The other
commenter recommended serialization by vibro-etching the tailpipe v-
band coupling to differentiate it from v-band couplings in other
locations of an aircraft.
The FAA disagrees that determination of a v-band coupling's hours
TIS cannot be done without serialization either by vibro-etching or
other means. Existing ADs that are included in paragraphs (d)(1)
through (10) of this AD, regarding a v-band coupling with life limits
have not required serialization. Once the hours TIS of a v-band
coupling is established, subsequent maintenance actions will be based
on hours TIS.
The FAA has not changed this AD in regard to these comments.

E. Requests Regarding V-Band Coupling: Type Design and Manufacturing

One individual commenter stated that instead of being spot-welded,
the rings (v-band couplings) should be solid state welded. This
commenter researched spot-welded couplings that revealed if the heat
and pressure on the metal prior to the spot-weld is not consistent, the
spot-weld will fail. Another individual commenter stated that spot-
welds are good in tension and not in shear. The commenter further
explained that as the v-band coupling is tightened, the spot-weld is in
shear, and that adding dynamic loads reduces the spot-weld's life even
further. This commenter suggested that a different type of attachment
be used such as a braze joint or a laser weld.
Regarding the type design changes, an individual commenter asked if
the installation of a riveted clamp would terminate the 500-hour TIS
replacement schedule. Another individual commenter recommended using
the v-band coupling information in Navair Technical Manual 1-1A-8,
``Engineering Manual Series Aircraft and Missile Repair, Structural
Hardware,'' which is used by the military, and adding this information
to AC 43.13-1B. Another individual commenter stated that additional
information on v-band couplings can be found in military specifications
MS27116C, ``Coupling, Clamp, Grooved, V Band 1.750 To 14.250 Flange OD
(Minus 320 Deg. To Plus 1500 Deg. F),'' and MIL-DTL-27536C, ``Coupling,
Clamp, Grooved, V-Band.'' A different individual commenter suggested
that by allowing a small [tungsten inert gas] TIG weld on the edges of
the clamp, the concern regarding the spot welds holding would be
addressed. An additional individual commenter referenced an unspecified
photo linked to the NPRM and said it was not representative of current
v-band coupling design.
An individual commenter stated that during manufacturing, the
single spot-welds might be placed too close to the trunnions, thereby
causing failure points. This commenter suggested using a total of four
spot-welds instead of two spot-welds. The FAA infers that the commenter
is requesting a change to the manufacturing of the v-band coupling.
The FAA has determined that inspections, in combination with life
limits, are sufficient to mitigate the risk. The FAA would consider any
future design improvements as an AMOC request following the procedures
outlined in paragraph (n) of this AD. Regarding the proposed revision
to AC 43.13-1B, that change is outside the scope of this AD and actions in an
advisory circular are recommendations, not mandatory.
The FAA has not changed this AD in regard to these comments.

F. Request for Clarification Regarding the Number/Percentage of In-
Flight Smoke and/or Fire Events

An individual commenter requested clarification regarding the
number or percentage of in-flight smoke and/or fire events related to
the NPRM.
The FAA does not have data indicating the specific number or
percentage of incidents/accidents in which the v-band coupling failure
caused a smoke event or an in-flight fire. At least one fatal accident
and two non-fatal accidents involving a v-band coupling failure had
occurrences of a fire. Smoke or fire could occur due to a separation of
the v-band coupling or loss of the tailpipe because of the hot exhaust
gases impinging on surrounding surfaces. This information was included
in the FAA's determination that an unsafe condition existed to justify
issuing this AD.
The FAA has not changed this AD as a result of this comment.

G. Requests Regarding Applicability

1. Remove Airplanes With STC SA4976NM Installed
Aerostar explained that airplanes with STC SA4976NM installed have
eliminated the v-band coupling at the tailpipe to turbocharger
connections and are not affected by the unsafe condition described in
the proposed AD. Aerostar stated that STC SA4976NM was approved as an
AMOC for the repetitive inspections required by AD 90-01-02, Amendment
39-6517, January 5, 1990 (issued as a priority letter), that required
repetitive dismantling inspections of the exhaust tailpipe assembly at
intervals not to exceed 50-hours TIS. The FAA infers that Aerostar
requested a change to the Applicability in the proposed AD to remove
airplanes with STC SA4976NM installed.
The FAA agrees. The installation of STC SA4976NM on Aerostar Model
PA-600, -601, -601P, -602P and -700P airplanes eliminates the v-band
coupling at the tailpipe to turbocharger connection. Paragraph (d),
Applicability, of this AD was revised to add STC SA4976NM to the list
of airplanes excepted from the applicability.
2. Remove Vulcanair S.p.A Model P.68B From the Applicability
Vulcanair requested that Vulcanair S.p.A Model P.68B airplanes be
removed from the Applicability Table in paragraph (d) of the proposed
AD. The commenter stated Vulcanair S.p.A Model P.68B airplanes are
equipped with two normally aspirated reciprocating engines.
The FAA agrees and revised Table 1 to paragraph (d) of this AD to
remove Vulcanair S.p.A Model P.68B airplanes. FAA Type Certificate Data
Sheet A31EU lists the Model P.68B airplane as equipped with two
Lycoming IO-360-A1B or Lycoming IO-360-A1B6 engines, which are normally
aspirated. If the airplane is modified after certification by an STC,
parts manufacturer approval, or field approval, with a turbocharged
reciprocating engine with a spot-welded, multi-segment v-band coupling
installed at the tailpipe to turbocharger exhaust housing flange, this
AD is applicable.
3. Add Textron Aviation Inc. Model T182 and TR182 Airplanes Equipped
With Lycoming O-540-L3C5D Engines
An individual commenter asked why Model T182 and TR182 airplanes
equipped with Lycoming O-540-L3C5D engines were not included in the
applicability of the proposed AD. The FAA infers that this commenter is
requesting that these airplane and engine combinations be added to the
applicability of the proposed AD.
The FAA agrees that these airplane models are affected by the
requirements of this AD but a change to this AD is not necessary
because Table 1 to paragraph (d) of this AD already includes Model T182
and TR182 airplanes.
The FAA has not changed this AD in regard to this comment.
4. Add Mooney Model M20F Airplanes With Aftermarket Installation
An individual commenter asked if Model M20F airplanes with an
aftermarket RayJay normalizing turbocharger are included in the
applicability of the proposed AD. The FAA infers that this commenter is
requesting that the applicability of the proposed AD be revised to
include these airplane models.
The FAA disagrees with adding the Mooney Model M20F airplanes
equipped with an aftermarket RayJay normalizing turbocharger to the
applicability of this AD because the FAA could not determine the STC
that was being referred to. However, based on the way the final rule is
written with language of ``as installed, but not limited to the
following aircraft'', this AD would still apply to all turbocharged,
reciprocating engine-powered airplanes and helicopters and
turbocharged, reciprocating engines with a spot-welded, multi-segment
v-band coupling installed at the tailpipe to turbocharger exhaust
housing flange, except for airplanes that are in compliance with an AD
listed in paragraphs (d)(1) through (10) of this AD or have STC
SA4976NM installed. These ADs are available in the AD docket at
regulations.gov by searching for and locating Docket No. FAA-2022-0891.
These v-band couplings are installed on, but not limited to, the
products listed in Table 1 to paragraph (d) of this AD. This AD would
apply regardless of whether the turbocharger is installed as part of
the type certificate, or under an STC, parts manufacture approval, or
field approval. Outside of type certification, it is the responsibility
of the owner working with a licensed mechanic to determine if the
configuration of the aircraft includes the spot-welded multi segment v-
band coupling installed at the tailpipe to the turbocharger exhaust
housing.
The FAA has not changed this AD in regard to this comment.
5. Add Turbine Helicopters With V-Band Clamps
An individual commenter asked if the NPRM needed to address v-band
couplings installed on turbine helicopters. The FAA infers that the
commenter requested to add turbine helicopters to the applicability of
the proposed AD.
The FAA disagrees. The use of the v-band couplings on turbine
helicopters is not addressed in this AD. This AD addresses the unsafe
condition for spot-welded, multi-segment v-band coupling installed at
the tailpipe to turbocharger exhaust housing flange for turbocharged,
reciprocating engine-powered airplanes and helicopters and
turbocharged, reciprocating engines. The vibratory environment for
turbine engines on helicopters is different and as such is not part of
the identified unsafe condition.
The FAA has not changed this AD in regard to this comment.
6. No Justification for Mooney Model M20K Airplanes
An individual commenter stated that there is not enough information
to justify an AD for a Mooney Model M20K airplane. The commenter cited
FAA SAIB CE-18-07, ``Exhaust Turbocharger; V-band Couplings Used in
Exhaust Systems on Turbocharged Reciprocating Engine Powered
Aircraft,'' dated December 14, 2017 (SAIB CE-18-07), which states the
``concern [was] not considered an unsafe condition that would warrant
AD action.'' The commenter also stated that a review of the FAA's Aviation
Safety Information Analysis and Sharing System and the NTSB's Accident
Database could not find any serious incidents involving defective v-
band couplings on Mooney Model M20K airplanes. The commenter supported
an inspection regime and includes it in the pre-flight check and does
an unspecified inspection of the v-band coupling at each oil change
when the turbo is easily accessible. The commenter explained that there
is a difference between ``big block'' 520-550 cubic-inch engines and
smaller 360 turbocharged engines, and that the NTSB safety
recommendations referred to in the NPRM refer to the ``big block''
engines. The commenter also pointed out that all of the ADs specified
in the proposed AD apply to larger displacement turbocharged
reciprocating engines.
The FAA disagrees that there is not enough justification to include
Mooney Model M20K airplanes in the applicability of this AD. When SAIB
CE-18-07 was issued, the FAA was still evaluating this issue and had
not determined that there was an unsafe condition warranting AD action.
The v-band couplings that are the subject of this AD are used on both
larger and smaller engines, and the inspections proposed in the NPRM
are not part of current inspection criteria. The accident/incident
failure data and existing AD actions demonstrate that a 500-hour TIS
life limit is appropriate for this type of multi-segment coupling and
that an unsafe condition exists.
The FAA has not changed this AD in regard to this comment.

H. Requests Regarding Inspections

1. Revise Paragraph (j) of the Proposed AD To Separate Compliance Times
From Inspection Procedures
EASA requested that paragraph (j) of the proposed AD, ``Inspections
Without Removal of the V-Band Coupling,'' be separated into two
paragraphs with one paragraph containing the requirement for an annual
inspection with references to both an inspection with the v-band
coupling removed and an inspection with the v-band coupling installed,
and the other paragraph containing the inspection procedure. The
commenter stated that having the inspection timeline and the inspection
procedures in the same paragraph may cause confusion.
The FAA agrees that having the inspection compliance times and
inspection procedures in the same paragraph could cause confusion. The
FAA added paragraph (j), ``V-band Coupling Inspections,'' in this AD to
specify only the inspection compliance times and re-designated the
subsequent paragraphs accordingly. Paragraph (i)(2) of this AD still
provides an alternative to initially removing the v-band coupling from
service by doing the inspections required by paragraphs (k)(1) through
(7) or (l) of this AD.

2. Remove Paragraph (j) of the Proposed AD

EASA requested that paragraph (j) of the proposed AD, ``Inspections
Without Removal of the V-Band Coupling,'' be removed because it is not
possible to do a thorough inspection with the v-band coupling
installed.
The FAA disagrees. The procedures that the FAA included for the
inspection of an installed v-band coupling were tested and it was
determined that these procedures are adequate to verify the condition
of the v-band coupling. If any of the inspection criteria for an
installed v-band coupling are not met, the v-band coupling is required
to either be replaced or undergo additional inspections with the v-band
coupling removed. These procedures have been used with success in
existing ADs that are included in paragraphs (d)(1) through (10) of
this AD.
The FAA has not changed this AD in regard to this comment.

3. Request To Revise Paragraph (j)(3) of the Proposed AD

An individual commenter requested that paragraph (j)(3) of the
proposed AD be moved to paragraph (k) of the proposed AD. The commenter
stated that it could not be determined if the v-segments are loose with
respect to the outer band with the outer band T-bolt torqued to
specification. The commenter requested this inspection be moved to
paragraph (j) after the v-band coupling is removed.
The FAA disagrees with moving this inspection from paragraph (j)(3)
of the proposed AD to paragraph (k) of this AD. Looseness of the v-band
coupling may occur if the coupling is not properly installed. Looseness
of the outer band may occur if the outer band has separated from the v-
band retainer segment or if the spot weld attachment is in the process
of failing or has failed. Therefore, this inspection must be done
without removing the v-band coupling.
The FAA has not changed this AD in regard to this comment.
4. Include a Non-Destructive Inspection
An individual commenter requested the FAA consider adding a
requirement for a non-destructive inspection (NDI). The commenter
stated the clamps are constantly stressed even in the absence of heat
cycling.
The FAA disagrees with adding a requirement for an NDI to this AD.
Due to the various v-band couplings, an NDI would have to be determined
by the v-band coupling manufacturer and the FAA has determined that the
visual inspections along with replacements will mitigate the unsafe
condition. However, additional inspections are acceptable as long as
they do not conflict with the visual inspection requirements,
replacement, and life limit requirements of this AD.
The FAA has not changed this AD in regard to this comment.

5. Insufficient Justification for Paragraph (j) of the Proposed AD

An individual commenter believed that there is not enough data to
justify an AD, specifically for paragraph (j) of the proposed AD
regarding repetitive inspections of v-band couplings. The commenter
cited multiple examples where root cause analysis was determined in
other AD actions. The commenter stated that the FAA has not made a
determination of what the root cause is for the proposed AD.
The FAA disagrees that there is no root cause for this AD. The FAA
issues an AD when an unsafe condition is found. The unsafe condition
addressed by this AD is fatigue failure of spot-welded, multi-segment
exhaust tailpipe v-band couplings as a result of stress corrosion
cracking that originated at or near a spot weld. As stated in the
Background, the data studied by the working group contained evidence of
pre-existing cracking of the couplings, known embrittlement at the spot
weld locations simply due to that manufacturing method, and outer band
cupping on the multi-segment couplings (which is the result of age,
over-use, and potential over-torqueing). These are the root causes of
the unsafe condition. Current inspection procedures are inadequate to
detect these cracks in a timely manner. Accordingly, the FAA is
mandating inspection procedures and a life limit to protect the fleet.
The life limit and inspections directly address the unsafe condition,
have been used in previous ADs, and therefore are appropriate for this
type of multi-segment coupling.
The FAA has not changed this AD in regard to this comment.

I. Request To Use Generic Terms in Paragraph (k) of the Proposed AD

EASA suggested that generic terms be used in paragraph (k)(1)(i) of
the proposed AD, such as ``fine abrasive cloth and mineral spirits'' instead
of ``crocus cloth and mineral spirits or Stoddard solvent'' because the current
terminology in the proposed AD might not be recognized outside of the United States.
The FAA partially agrees. The term ``crocus cloth'' is a general
term and not specific. The term ``Stoddard solvent'' refers to the
original developer of the solvent. This AD already includes the term
``mineral spirts.'' The FAA revised paragraph (l)(1)(i) of this AD to
include ``crocus cloth or fine abrasive cloth and mineral spirits or
Stoddard solvent.''

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 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 up to 41,058 airplanes,
helicopters, and engines (products of U.S. registry). The FAA has no
way of determining the number of these products that could have an
affected spot-welded, multi-segment v-band coupling installed. The
FAA's estimated cost on U.S. operators reflects the maximum possible
cost based on the 41,058 products of U.S. registry. Based on this, the
FAA estimates the following costs to comply with this AD:
The FAA estimates the following costs to comply with this AD:

Estimated Costs

On-Condition Costs

This AD provides operators the option of performing an inspection
with the coupling removed from the aircraft instead of an inspection of
the coupling without removing it from the aircraft. In some cases, an
inspection with the coupling removed may be required.
A coupling may need to be removed from service before it reaches
its 500-hour TIS life limit if it does not meet all of the inspection
criteria at each inspection. The FAA has no way of determining the
number of products that may need to remove the coupling from service
before reaching its 500-hour TIS life limit.

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,
(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

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 adding the following new airworthiness
directive: