[Federal Register Volume 88, Number 29 (Monday, February 13, 2023)]
[Rules and Regulations]
[Pages 9170-9185]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-02986]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-1078; Project Identifier AD-2020-00716-A; 
Amendment 39-22324; AD 2023-02-17]
RIN 2120-AA64


Airworthiness Directives; Textron Aviation Inc. (Type Certificate 
Previously Held by Cessna Aircraft Company) Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for all 
Textron Aviation Inc. (type certificate previously held by Cessna 
Aircraft Company) (Textron) Model 210N, 210R, P210N, P210R, T210N, 
T210R, 177, 177A, 177B, 177RG, and F177RG airplanes. This AD was 
prompted by the in-flight break-up of a Model T210M airplane in 
Australia, due to fatigue cracking that initiated at a corrosion pit, 
and subsequent corrosion reports on other Model 210- and 177-series 
airplanes. This AD requires visual and eddy current inspections of the 
carry-thru spar lower cap for corrosion, cracking, and damage; 
corrective action if necessary; application of a protective coating and 
corrosion inhibiting compound (CIC); and reporting the inspection 
results to the FAA. The FAA is issuing this AD to address the unsafe 
condition on these products.

DATES: This AD is effective March 20, 2023.
    The Director of the Federal Register approved the incorporation by 
reference of certain publications listed in this AD as of March 20, 
2023.

ADDRESSES: 
    AD Docket: You may examine the AD docket at regulations.gov by 
searching for and locating Docket No. FAA-2020-1078; 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 service information identified in this final rule, 
contact Textron Aviation Inc., One Cessna Boulevard, Wichita, KS 67215; 
phone: (316) 517-6061; email: [email protected]; website: 
support.cessna.com.
     You may view this service information at the FAA, 
Airworthiness Products Section, Operational Safety Branch, 901 Locust, 
Kansas City, MO 64106. For information on the availability of this 
material at the FAA, call (817) 222-5110. It is also available at 
regulations.gov by searching for and locating Docket No. FAA-2020-1078.

FOR FURTHER INFORMATION CONTACT: Bobbie Kroetch, Aviation Safety 
Engineer, Wichita ACO Branch, FAA, 1801 Airport Road, Wichita, KS 
67209; phone: (316) 946-4155; email: [email protected] or [email protected].

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 all Textron Model 210N, 
210R, P210N, P210R, T210N, T210R, 177, 177A, 177B, 177RG, and F177RG 
airplanes. The NPRM published in the Federal Register on May 11, 2021 
(86 FR 25812).
    The NPRM was prompted by a report that, on May 26, 2019, a Textron 
Model T210M airplane experienced an in-flight breakup while performing 
low-altitude aerial survey operations in Australia. The carry-thru spar 
failed and resulted in wing separation and loss of control of the 
airplane. A visual examination of the fracture surface identified 
fatigue cracking that initiated at a corrosion pit. The FAA issued an 
airworthiness concern sheet (ACS) on June 27, 2019, advising owners and 
operators of the accident and requesting relevant information about the 
fleet.
    Following the ACS, the FAA received reports of widespread and 
severe corrosion of the carry-thru spar. Earlier Model 210G, T210G, 
210H, T210H, 210J, T210J, 210K, T210K, 210L, T210L, 210M, and T210M 
airplanes experienced the most widespread and severe corrosion, and the 
FAA issued AD 2020-03-16, Amendment 39-21029 (85 FR 10043, February 21, 
2020) (AD 2020-03-16) as an immediately adopted rule (Final Rule; 
Request for Comments) to address the unsafe condition on those 
airplanes.
    The FAA also received reports of corrosion on later Model 210N, 
P210N, T210N, 210R, P210R, and T210R airplanes and Model 177-series 
airplanes. On Model 210N, P210N, T210N, 210R, P210R, and T210R 
airplanes, the upper surface of the carry-thru spar is covered by 
fuselage skin and is not exposed to the environment. This removes the 
leak paths at the skin splices common to the earlier Model 210-series 
airplanes and reduces the potential for moisture intrusion. 
Additionally, the later Model 210-series airplanes were manufactured 
with zinc chromate primer applied to all carry-thru spars. However, the 
later Model 210-series airplanes were also delivered with foam 
installed along the carry-thru spar lower cap. The foam traps moisture 
against the lower surface of the carry-thru spar cap, which can aid in 
the development of corrosion.
    The Model 177-series airplanes share a similar carry-thru spar 
design with the earlier Model 210-series airplanes: The upper surface 
of the carry-thru spars are exposed, and the carry-thru spars might not 
have been delivered with zinc chromate primer applied. Although Model 
177-series airplanes were not delivered with foam padding installed on 
the lower surface of the carry-thru spar, corrosion has been reported 
on the carry-thru spar lower cap for these airplanes. Corrosion of the 
carry-thru spar lower cap can lead to fatigue cracking or reduced 
structural strength of the carry-thru spar, which, if not addressed, 
could result in wing separation and loss of control of the airplane.
    In the NPRM, the FAA proposed to require visual and eddy current 
inspections of the carry-thru spar lower cap for corrosion, cracking, 
and damage; corrective action if necessary; application of a protective 
coating and CIC; and reporting the inspection results to the FAA. 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 124 commenters. The majority of 
comments were from individuals. Organizations submitting comments 
included the Aircraft Owners and Pilots Association (AOPA), Aviation 
Plus LLC,

[[Page 9171]]

Cardinal Flyers Online, and Textron. In addition, the FAA has included 
in the docket a discussion with the European Union Aviation Safety 
Agency that clarifies the proposed NPRM. The following summarizes the 
comments received on the NPRM and provides the FAA's responses.

A. Requests To Withdraw the NPRM

    Comment summary: AOPA and numerous individual commenters requested 
that the NPRM be withdrawn.
1. There Is No Unsafe Condition: Crash Was Maintenance/Operation Issue
    Seven commenters stated that the NPRM was unnecessary because they 
diligently inspect their airplanes and have not detected any problems 
during their inspections. Three commenters explained that this crash 
was due to a maintenance issue. One commenter questioned how the 
accident airplane was maintained. Another commenter stated that an AD 
is not necessary because the Model T210M spar fracture was due to heavy 
use and lack of maintenance and that a service bulletin would be 
sufficient. Several individual commenters discussed how the accident 
airplane was operated, stating improper operation and operation outside 
the standard limit of the airframe caused the accident.
    Two commenters stated that there does not appear to be evidence 
that a problem exists. One commenter stated that voluntary visual 
inspections of the fleet have not exposed a widespread issue and noted 
that all airplane structures are exposed to the same aging issues of 
corrosion and fatigue and that the NPRM singles out Model 210- and 177-
series airplanes.
    FAA response: The FAA disagrees with the commenters' requests to 
withdraw the NPRM. Based on available data, including the corrosion and 
damage reports received, the FAA disagrees that an unsafe condition 
does not exist. While the in-flight break-up of a Model T210M airplane 
in Australia was the catalyst for this AD, the FAA determined that 
Model 210- and 177-series airplanes share a common single-load path 
design constructed from the same material. Also, the FAA issued an ACS, 
dated June 27, 2019, advising owners and operators of the accident and 
requesting relevant information about the fleet. The reports gathered 
in response to this ACS, combined with inspection reports received in 
response to AD 2020-03-16, issued to address widespread and severe 
corrosion of the carry-thru spars on Model 210G, T210G, 210H, T210H, 
210J, T210J, 210K, T210K, 210L, T210L, 210M, and T210M airplanes, 
revealed that carry-thru spars for Model 210- and 177-series airplanes 
are subject to corrosion. Corrosion can initiate cracking, resulting in 
a carry-thru spar being unable to carry the required load.
    Australian Transport Safety Bureau (ATSB) Report AO-2019-026, In-
flight break-up involving Cessna T210M, VH-SUX, dated May 26, 2019 
(ATSB AO-2019-026) does state, in part, that ``The cyclic loads induced 
by the low-level survey flight profile were significantly greater than 
those associated with the higher-level flight profile originally 
intended for the aircraft type. This probably increased the risk of 
fatigue-related structural failure.'' However, ATSB AO-2019-026 does 
not list inadequate operator maintenance or identify improper operation 
as contributing factors to the accident.
    The FAA acknowledges that the carry-thru spar on individual 
airplanes might not have findings of corrosion or damage. However, as 
of January 13, 2023, the FAA has received 226 inspection reports from 
operators of Model 210N, 210R, P210N, P210R, T210N, and T210R airplanes 
that include 21 reports of corrosion and damage, with two carry-thru 
spars removed from service. The FAA has also received 211 inspection 
reports from operators of Textron Model 177-series airplanes that 
include 120 reports of corrosion and at least 14 spars removed from 
service due to corrosion or damage.
2. NPRM Was Overreaching
    Three commenters stated that the NPRM was overreaching. One 
commenter stated that the NPRM could be interpreted as punitive and 
another commenter stated that it is overreaching because it cast a net 
to include all Model 177-series airplanes and most Model 210-series 
airplanes.
    FAA response: The FAA disagrees with the commenters' requests to 
withdraw the NPRM. Based on available data, including the corrosion and 
damage reports received, the FAA disagrees that the NPRM was 
overreaching by including all Model 210- and 177-series airplanes in 
the applicability. The FAA agrees that other types and models of 
airplanes have corrosion and fatigue issues, but this AD and its 
compliance time are based on data for these model airplanes and the 
nature of this unsafe condition. The applicability of this AD is all 
Model 210- and 177-series airplanes with carry-thru spars manufactured 
from 2014-T6 aluminum forging because this part is single-load path, 
critical structure manufactured from a material susceptible to severe 
corrosion.
3. NPRM Is Unnecessary: Use Existing Maintenance Directions, Service 
Documents, or Issue a Special Airworthiness Information Bulletin (SAIB)
    Six commenters requested the FAA withdraw the NPRM and allow 
operators to rely upon the existing maintenance directions or service 
documents. Another commenter stated that a Textron service letter 
approach would be sufficient. One commenter stated that the service 
information approach was the correct decision and that Textron should 
provide data behind the request for the NPRM. The FAA infers that the 
commenter is requesting that the NPRM be withdrawn in lieu of service 
information. One commenter suggested that the FAA issue an SAIB instead 
of an AD.
    FAA Response: The FAA disagrees with the commenters' requests to 
withdraw the NPRM. The procedures in Textron service letters are not 
legally enforceable requirements. Similarly, the FAA could issue an 
SAIB to draw attention to the inspections area, but an SAIB is 
informational only. Thus, an AD is the only way the FAA can mandate the 
procedures necessary to fix the unsafe condition.
    Textron does not have the authority to determine if the FAA will or 
will not issue an AD on a potential airworthiness issue. The FAA has 
the regulatory authority to issue an AD and, in compliance with 14 CFR 
39.5, issues an AD when it determines that an unsafe condition exists 
that is likely to exist or develop in other products of the same type 
design. For this AD, the FAA based its determination on data received 
in response to the ACS dated June 27, 2019, inspection reports 
completed on airplanes in the fleet, and data and analysis provided by 
Textron and evaluated by the FAA.
    Cessna previously identified the carry-thru spar as an area of 
concern through the Continued Airworthiness Program (CAP) inspections, 
introduced in 1992, as well as the later published supplemental 
inspection documents (SIDs). Specifically, CAP Inspection Number 57-10-
08 for the Cessna 210 identifies inspections for the carry-thru spar 
lower surface and additional inspection on the lower spar cap. 
Subsequent inspections completed after the Model T210M accident in 
Australia indicated that operators were not doing the voluntary 
inspections specified in the SIDs.

[[Page 9172]]

B. Requests Regarding Data Justifying AD Action

    Comment summary: Eleven commenters requested that the FAA provide 
the data used to justify the NPRM. One commenter stated that pilots and 
owners need access to the underlying data being used to make critical 
decisions. Another commenter stated that neither the FAA nor Textron 
presented any evidence of the corrosion issue existing in Model 210-
series airplanes that came from the factory with corrosion proofing 
coating already applied, specifically the 1979 N-model and newer 
airplanes, and suggested the FAA investigate the issue before taking 
widespread steps to correct what may be a theoretical issue. An 
additional commenter stated that no description is found specifying 
what constitutes severe corrosion compared to non-severe corrosion and 
requested to know how likely a carry-thru spar is to fail with 
corrosion versus severe corrosion. Another commenter requested that the 
FAA provide data to show there is a real threat to warrant immediate 
intervention.
    FAA response: The FAA agrees with the commenters' requests to 
provide additional information regarding the data used to justify 
issuing this AD. Prior to issuing AD 2020-03-16 and the NPRM for this 
final rule, the FAA issued the ACS, dated June 27, 2019, advising 
owners and operators of the accident involving the Model T210M airplane 
in Australia and requesting relevant information about the fleet. The 
FAA evaluated data obtained in response to the ACS and from inspection 
reports completed in response to Textron Aviation Mandatory Single 
Engine Service Letter, SEL-57-06, dated June 24, 2019 (Textron SEL-57-
06); Textron Aviation Single Engine Service Letter SEL-57-07, dated 
June 24, 2019 (Textron SEL-57-07); and subsequent Textron service 
letters that are identified in the Other Related Information paragraph. 
The data demonstrated that the risk was higher in earlier Model 210 
airplanes (Model 210G, T210G, 210H, T210H, 210J, T210J, 210K, T210K, 
210L, T210L, 210M, and T210M airplanes), which supported issuing AD 
2020-03-16 as an immediately adopted rule (Final Rule; Request for 
Comments).
    The data received for later Model 210- and 177-series airplanes 
supported issuing the NPRM for this final rule. As of January 13, 2023, 
the FAA has received inspections results for 226 Model 210N, 210R, 
P210N, P210R, T210N, and T210R airplanes, including 21 reports of 
corrosion and damage and 2 spars removed from service. None of these 
later model airplanes reported cracking in the carry-thru spar. For 
Model 177-series airplanes, the FAA has received inspections results 
for 211 airplanes, including 120 reports of corrosion and at least 14 
spars removed from service due to corrosion or damage. There have not 
been any reports of cracking in the lower flange of the carry-thru 
spars on Model 177-series airplanes.
    Model 210- and 177-series airplanes share a similar carry-thru spar 
design with similar geometry. The carry-thru spars are single-load 
path, critical structure manufactured from 2014-T6 aluminum forging, 
which is susceptible to intergranular corrosion. A description of 
intergranular corrosion can be found in Chapter 2, Section 2.5.5, of 
FAA Advisory Circular AC 43-4B, Corrosion Control for Aircraft, dated 
September 11, 2018. Analysis completed by Textron demonstrated that the 
carry-thru spars on Model 210- and 177-series airplanes experience 
similar stress levels in operation. As of January 13, 2023, at least 
six spars were reported to have suspected cracking associated with 
corrosion in the lower flange of the carry-thru spar on early Model 
210-series airplanes. For the carry-thru spar, severe corrosion is 
demonstrated by blistering, scaling, flaking, or measuring in excess of 
0.010-inch deep. Any corrosion that results in cracking also qualifies 
as severe corrosion. Due to a large number of variables, the FAA cannot 
predict how spars with varying degrees of theoretical corrosion could 
fail in comparison to one another. However, the FAA's inability to 
predict the precise moment of failure does not eliminate or invalidate 
the unsafe condition.
    The FAA determined that a longer compliance time than what is 
required by AD 2020-03-16 was acceptable for addressing the identified 
unsafe condition for later Model 210-series airplanes (Models 210N, 
P210N, T210N, 210R, P210R, and T210R airplanes) and Model 177-series 
airplanes, which is why those airplane models were not included in AD 
2020-03-16 but are included in the applicability for this AD.

C. Requests Regarding Applicability

    Numerous individual commenters requested changes to the 
applicability of the proposed AD for a variety of reasons.
1. Accounting for Differences Between Model 210- and 177-Series 
Airplanes
    Comment summary: Thirteen commenters requested that the proposed AD 
account for differences between Model 210- and 177-series airplanes, 
including weight, operational usage, flight characteristics, wing 
loading, and application of corrosion protection. Four commenters 
stated that the FAA should account for the lack of interior foam 
padding installed on the lower carry-thru spar cap lower surface on 
Model 177-series airplanes as compared to Model 210-series airplanes. 
Two commenters identified that Model 177-series airplanes lack an 
interior bracket that is installed on Model 210-series airplanes, with 
one commenter noting the straps are dissimilar metal. Another commenter 
stated that corrosion on Model 177-series airplanes was found on the 
spar web, lower cap to web radius, and upper surface of the lower cap, 
as opposed to the Model 210-series airplanes where corrosion was found 
on the lower surface of the lower cap.
    FAA response: The FAA acknowledges that there are differences in 
the carry-thru spars between Model 210- and 177-series airplanes. The 
FAA agrees that any subsequent rulemaking for the carry-thru spars on 
Model 210- and 177-series airplanes might not be the same. However, 
this is an interim AD requiring a visual inspection, eddy current 
inspection of the critical location, and corrosion treatment of the 
spars, and the FAA has determined that this action is necessary to 
address the unsafe condition for all affected airplanes.
    Although the carry-thru spars for both Model 210- and 177-series 
airplanes are constructed from the same 2014-T6 aluminum forgings, the 
thicknesses of the caps are thinner on Model 177-series airplanes 
compared to Model 210-series airplanes. While the carry-thru spars on 
Model 177-series airplanes do not have interior foam adhered to the 
lower carry-thru spar cap, the installation orientation of the carry-
thru spar in the airplane can result in moisture collecting on the 
upper surface of the forward flange of the carry-thru spar lower cap, 
and corrosion has been found on the tension-carrying lower cap. This AD 
only requires inspecting the lower cap and not the upper cap, web, or 
web to lower cap radius. Of the 120 reports of corrosion for Model 177-
series airplanes, 27 include findings of corrosion on the upper surface 
of the lower carry-thru spar cap, an area included in the inspections 
required by this AD. Many of the 120 reports included insufficient 
information to identify the specific location of the corrosion.
    Like the carry-thru spars on Model 210-series airplanes, some 
carry-thru spars on Model 177-series airplanes

[[Page 9173]]

were treated with primer in the factory prior to delivery, though not 
all spars were treated. This AD does account for the differences in 
these carry-thru spars in the required corrosion protection 
application. However, the existence of primer itself may not eliminate 
the possibility that corrosion exists and the spars still must be 
inspected. The FAA reviewed reports gathered in response to the ACS, 
dated June 27, 2019, and in response to AD 2020-03-16, which 
demonstrated that the carry-thru spars on both Model 210- and 177-
series airplanes are subject to corrosion. Corrosion can initiate a 
crack, resulting in the carry-thru spar being unable to carry the 
required load. Analysis demonstrates crack growth can happen on an 
airplane under typical operation and in the original configuration. The 
carry-thru spars installed on Model 210- and 177-series airplanes share 
a similar single-load path design and geometry, are critical structure, 
and are constructed of 2014-T6 aluminum forging, which is susceptible 
to intergranular corrosion. Analysis completed by Textron demonstrated 
that the carry-thru spars experience similar stress levels in typical 
operation.
    Although Model 177-series airplanes lack interior brackets that are 
installed on Model 210-series airplanes, corrosion on Model 210-series 
airplanes is not limited to the area surrounding the interior brackets 
and has been reported in a variety of locations on the carry-thru spar 
lower cap. The interior brackets installed on a limited number of Model 
210-series airplanes are manufactured from 2024-T42 aluminum, which 
would not cause dissimilar metal corrosion with the carry-thru spar 
2014-T6 aluminum forging. Corrosion has also been reported on Model 
210-series airplanes that do not have the interior brackets installed.
2. Removing Model 177-Series Airplanes
    Comment summary: One commenter stated that Model 177-series 
airplanes should not be included in the applicability of the proposed 
AD because the Model T210M airplane involved in the Australia accident 
was highly modified and flown in an aggressive manner that exceeded its 
design parameters. Eight commenters stated that there is a lack of 
service difficulty reports and failures associated with Model 177-
series airplanes to justify including them in the applicability of the 
proposed AD. Three commenters stated that they did not find any issues 
during their airplane inspections. One commenter requested that Model 
F177RG airplanes be excluded from the applicability of the proposed AD 
because they were delivered from the factory with an interior coating 
of zinc chromate for corrosion protection.
    Two commenters stated that the Cessna Model 177 community is 
proactive regarding maintenance and has a strong type club. The FAA 
infers that these commenters are requesting changes to the proposed AD 
based on the proactive nature of the Cessna Model 177 community.
    FAA response: The FAA does not agree with the commenters' requests 
to remove Model 177-series airplanes from the applicability of this AD. 
The justification for issuing this AD is not based solely on the 
accident of the Model T210M airplane in Australia. Although that 
accident was a catalyst, as mentioned previously, the carry-thru spars 
on Model 210- and 177-series airplanes share a similar single-load path 
design, are critical structure, and are constructed of 2014-T6 aluminum 
forging, which is susceptible to intergranular corrosion. The FAA does 
not dispute that carry-thru spars on individual airplanes may not be 
affected by corrosion or damage; however, the reported inspection 
results demonstrate that Model 177-series airplanes do have a high rate 
of corrosion and damage.
    The FAA agrees that the Cessna 177 community has a very strong type 
club and many proactive owners and operators. However, the FAA 
disagrees that Model 177-series airplanes should not be subject to the 
actions defined in the proposed AD. Not all operators are proactive and 
diligent in voluntarily inspecting for corrosion, so the inspections 
must be mandated. Out of the 211 Model 177-series reports received by 
the FAA as of January 13, 2023, 120 have reported corrosion. Of those, 
at least 14 were removed from service due to corrosion or damage.
    The FAA acknowledges that some Model 177-series carry-thru spars, 
including those on Model F177RG airplanes, were treated with primer in 
the factory prior to delivery. This AD does account for the differences 
in these spars in the requirement to apply corrosion protection. 
However, the FAA disagrees that airplanes delivered from the factory 
with corrosion protection applied should be excluded from the AD, as 
corrosion has been reported on airplanes with factory-applied corrosion 
protection.
3. Removing Certain Model 210-Series Airplanes
    Comment summary: Two commenters requested that later Model 210-
series airplanes (Models 210N, 210R, P210N, P210R, T210N, and T210R) be 
removed from the applicability of the proposed AD because the cabin 
roof skin is one piece and completely covers the carry-thru spars, 
which prevents water entry. The commenters stated that these airplane 
models were factory-primed prior to installation, which improves the 
corrosion protection, and that none of the Model 210N and Model 210R 
airplanes that they are responsible for have evidence of corrosion 
related problems. One of the commenters stated that Model 210N 
airplanes, especially Model P210N airplanes, should not be included in 
the proposed AD because these airplanes have continuous fuselage skin 
and have factory-applied zinc chromate coating and sealant applied on 
the pressurized fuselage.
    FAA response: The FAA acknowledges that later Model 210-series 
airplanes, including Model 210N, 210R, P210N, P210R, T210N, and T210R 
airplanes, are less susceptible to corrosion than the earlier Model 
210-series airplanes. As of January 13, 2023, the FAA has received 
inspection reports on 226 later Model 210-series airplanes, including 
15 (7%) reporting corrosion. No later Model 210-series airplanes were 
removed from service due to corrosion. Two carry-thru spars were 
removed from service due to damage. This is compared to 47% of the 
earlier Model 210-series airplanes reporting corrosion and 57% of the 
Model 177-series airplane fleet reporting corrosion.
    The combined features of factory primer, continuous skin, and 
sealing, specifically associated with the pressurized airplanes, likely 
contributed to the lower corrosion rate; however, carry-thru spars on 
all Model 210-series airplanes have a similar carry-thru spar design 
and the actions identified in this AD are appropriate for all Model 
210-series airplanes. As previously discussed, the carry-thru spars 
have a single-load path critical structure, and the spar is constructed 
of 2014-T6 aluminum forging, which is susceptible to intergranular 
corrosion. Additionally, analysis completed by Textron revealed that 
later Model 210-series airplanes, due to their weight and 
configuration, demonstrate higher stress levels in operation when 
compared to earlier Model 210-series airplanes. Therefore, the critical 
crack length--the length at which the crack reduces the capability of 
the structure below that provided in the certification basis--is 
smaller in the later Model 210-series airplanes. This AD is interim 
action and the FAA will continue to evaluate the inspection reports 
when determining final action for mitigating the identified unsafe

[[Page 9174]]

condition on Model 210-series airplanes.
4. Airplane Operation
    Comment summary: Several commenters requested that the 
applicability of the proposed AD take into account the type of airplane 
operation. The commenters noted that the Model T210M airplane that 
experienced the in-flight break-up was operated in a more severe manner 
than the typical fleet. One commenter noted that Textron SEL-57-07 
included similar visual and eddy current inspections as those in the 
proposed AD but the effectivity was limited to airplanes flown with 
severe usage, as defined by service and maintenance manual information. 
Another commenter suggested that an evaluation be used similar to one 
that was used for the Piper wing spar AD 2020-26-16, Amendment 39-21371 
(86 FR 3769, January 15, 2021).
    FAA response: The FAA reviewed inspection reports provided by 
operators of the current fleet of Model 210- and 177-series airplanes, 
which includes corrosion reports for airplanes operated in various 
environments, ranging from mild to severe corrosion environments, and 
under different types of operation. In addition, enforcement of an AD 
based on airplane operation would be difficult because FAA regulations 
do not require all operators to maintain records of operations based on 
usage and many airplanes are utilized in different kinds of operations.
    The FAA determined that an evaluation similar to the one used for 
Piper wing spar AD 2020-26-16 is not appropriate for this AD. AD 2020-
26-16 requires calculating ``factored service hours'' for each main 
wing spar to determine when an inspection is required. The application 
of the ``factored service hours'' formula will identify when an 
airplane meets the criteria for the eddy current inspection of the 
lower main wing spar bolt holes and replacement of the wing spar on 
affected Piper airplanes.
    The unsafe condition on the Model 210-and 177-series airplanes 
addressed by this AD involves both corrosion and cracking. The FAA 
cannot use an evaluation similar to the one used for the Piper 
airplanes to draw the same conclusions or correlations to the unsafe 
condition addressed by this AD, as the unsafe condition associated with 
AD 2020-26-16 is primarily associated with fatigue cracking concerns.
5. Primed and Unprimed Airplanes
    Comment summary: One commenter requested that the FAA account for 
the differences in primed and unprimed carry-thru spars on Model 177-
series airplanes in the proposed AD. The commenter explained that early 
Model 177-series airplanes did not have protective coating (primer) 
applied from the factory but mid and later year airplanes did.
    FAA response: The FAA acknowledges that carry-thru spars on some 
Model 177-series airplanes were treated with primer in the factory 
prior to delivery and this AD does account for the differences between 
primed and unprimed airplanes regarding the requirement to apply 
corrosion protection. However, the FAA disagrees that airplanes 
delivered with factory-applied corrosion protection should be excluded 
from the applicability of this AD. Corrosion has been reported on 
airplanes with factory-applied corrosion protection and the carry-thru 
spars on those airplanes must be inspected.

D. Requests Regarding Special Flight Permits

    Comment summary: AOPA, Cardinal Flyers Online, and several 
individual commenters requested that the FAA allow special flight 
permits. The commenters explained that not all owners and operators 
have local repair and maintenance facilities and that many repair and 
maintenance facilities cannot perform all of the actions necessary to 
comply with the requirements specified in the proposed AD. The 
commenters noted that paragraph (m) of the proposed AD prohibited 
special flight permits, which would prohibit any flight to complete the 
visual and eddy current inspections specified in the proposed AD; 
therefore, all visual inspections and on-condition blending must either 
be completed at a facility with eddy current capability or would 
require an inspector with such capability to travel to the airplane. 
The commenters stated that allowing special flight permits would allow 
more facilities to complete individual portions of the inspection, 
increasing capacity and alleviating backlog at aircraft maintenance 
facilities. The commenters stated that allowing special flight permits 
could increase repair quality, improve scheduling, reduce costs, and 
encourage more owners to complete the inspections, increasing the 
safety of the fleet. Prohibiting special flight permits, however, could 
result in the inability to repair the affected airplanes. In addition, 
four commenters stated that the lack of documented failures for the 
Model 177 does not justify the prohibition of special flight permits.
    FAA response: The FAA partially agrees with the commenters' 
requests and revised paragraph (m) of this AD to allow special flight 
permits in limited situations because it would grant owners and 
operators more flexibility when complying with the required actions in 
this AD and reduce the burden on inspection facilities and mechanics.
    The FAA revised paragraph (g)(4) of this AD to allow airplanes 
without detected corrosion, cracking, or other damage, or evidence of 
previous corrosion removal to continue to operate and complete the eddy 
current inspection required by paragraph (h) of this AD within 200 
hours TIS after the effective date of the AD or within 12 months after 
the effective date of this AD, whichever occurs first.
    The FAA agrees with allowing an airplane with evidence of corrosion 
to be relocated if the process for obtaining a special flight permit is 
completed in accordance with FAA regulations, policy, and guidance. 
Furthermore, the FAA agrees with allowing an airplane with damage other 
than corrosion or evidence of previous blending to be relocated, 
provided the Wichita ACO Branch is contacted and provides concurrence.
    The FAA disagrees with granting special flight permits if either 
the visual inspection or the eddy current inspection detects cracking 
in the carry-thru spar lower cap.

E. Requests Regarding Compliance Time

1. Extend the Compliance Time for the Required Inspections
    Comment summary: AOPA, Aviation Plus LLC, Cardinal Flyers Online, 
and numerous individual commenters requested that the compliance time 
be extended for the visual inspection specified in paragraph (g) of the 
proposed AD (within 200 hours time-in-service (TIS) or within 12 months 
after the effective date, whichever occurs first). Four commenters 
suggested the compliance time be 200 hours TIS or within 12 months 
after the effective date of the AD, whichever occurs later. Two 
commenters suggested requiring the visual inspection within 12 months 
after the effective date of the AD, but not requiring the eddy current 
inspection required by paragraph (h) of the proposed AD within that 
timeframe. Several commenters remarked that TIS is more critical than 
calendar time and requested the FAA remove the 12 month time 
requirement to complete the visual inspection. One commenter suggested 
the compliance time be changed to 200 hours TIS or the next annual 
inspection

[[Page 9175]]

after the issuance of the AD, whichever occurs first. Two commenters 
provided additional compliance times, ranging from 36 months or 500 
hours TIS to 5 years and 200 hours TIS. Eleven commenters noted that 
the 12-month calendar limit would make compliance difficult due to 
limited availability of maintenance facilities and personnel, 
potentially grounding airplanes. Several commenters raised concerns 
that there are not enough qualified maintenance facilities to handle 
the workload of the inspection within a 12-month period, especially 
given the prohibition on special flight permits and the requirements of 
an AD for the Piper wing spar.
    One commenter mentioned that most Textron Model 177-series 
airplanes are flown less than 200 hours per year and three commenters 
identified that no carry-thru spars have failed on the Textron Model 
177-series airplanes. The FAA infers that these commenters are thus 
requesting an increase in the compliance time for the inspections 
required by this AD.
    FAA response: Based on the inspection reports received, the FAA 
disagrees with extending the compliance times specified in paragraph 
(g) of this AD. The compliance times specified in this AD correspond 
with the compliance times published in Textron Aviation Mandatory 
Single Engine Service Letter, SEL-57-08, Revision 2, dated August 3, 
2020 (Textron SEL-57-08R2) and Textron Aviation Single Engine Service 
Letter SEL-57-09R1, dated August 3, 2020 (Textron SEL-57-09R1). Textron 
superseded Textron Aviation Mandatory Single Engine Service Letter, 
SEL-57-07, Revision 1, dated November 19, 2019 (Textron SEL-57-07R1), 
with Textron SEL-57-09R1, which identifies a compliance time of 200 
flight hours or the next annual inspection from date of receipt, of 
that service letter, whichever occurs first.
    The FAA does not agree with a compliance time based solely on usage 
TIS or on calendar time, nor does the FAA agree that the compliance 
time should be ``200 hours TIS or 12 months, whichever occurs later'' 
after the effective date of this AD. The carry-thru spar is a critical 
single-load path structure, and if a crack initiates, there could be a 
catastrophic failure. Corrosion is a function of calendar time and 
crack growth is a function of hours TIS. The FAA has received reports 
of severe corrosion on carry-thru spars with less than 4,000 hours TIS 
and corrosion could initiate cracking in structure with low hours TIS.
    The FAA does not agree with revising the compliance time to ``200 
hours TIS or next annual inspection after the issuance of this AD, 
whichever occurs first'' because if the next annual inspection is due 
before 12 months after the effective date of this AD that would be more 
restrictive than the language in the proposed AD, and could occur 
almost immediately. Operators can always accomplish the actions 
required by an AD prior to the compliance time specified in an AD.
    The FAA has revised paragraph (g)(4) of this AD to allow airplanes 
without detected corrosion, cracking, or other damage, or evidence of 
previous corrosion removal to do the eddy current inspection required 
by paragraph (h) of this AD within 200 hours TIS after the effective 
date of this AD or within 12 calendar months after the effective date 
of this AD, whichever occurs first.
    The FAA acknowledges both the limitations on the availability of 
maintenance facilities and personnel capable of completing the 
inspections required in this AD and the difficulty in meeting the 
compliance time in paragraph (g) of this AD without the ability to 
relocate the airplane. The FAA would entertain alternative methods of 
compliance (AMOCs) to extend the compliance time on a case-by-case 
basis provided the work was scheduled. If scheduling an eddy current 
inspection is difficult, an owner, operator, or any interested party 
can apply for an AMOC using the procedures in paragraph (n) of this AD. 
The AMOC request must include substantiating data showing that the 
proposed AMOC provides an acceptable level of safety for a different 
method or adjustment of the compliance time to address the unsafe 
condition, other than the one specified in the AD. Also, the FAA has 
revised paragraph (g)(4) in this AD to allow airplanes without detected 
corrosion, cracking, or other damage, or evidence of previous corrosion 
removal to complete the actions required by paragraph (h) of this AD 
within 200 hours TIS after the effective date of this AD or within 12 
months after the effective date of this AD, whichever occurs first. As 
discussed above in section D., Requests Regarding Special Flight 
Permits, the FAA has revised paragraph (m) of this AD to allow special 
flight permits in limited situations.
2. Correspond Compliance Time for Eddy Current Inspection With Service 
Letter
    Comment summary: One commenter requested the FAA explain the 
differences between the proposed AD requiring an eddy current 
inspection within one year and the Textron service letter (Textron SEL-
57-07) that specified an eddy current inspection for most Model 177-
series airplanes at or after 15,000 hours TIS. The FAA infers that the 
commenter is requesting the compliance time specified in the proposed 
AD match what is in the Textron SEL-57-07.
    FAA response: The FAA agrees that there are differences between the 
compliance time in the proposed AD and Textron SEL-57-07. Textron 
Aviation superseded Textron SEL-57-07 with Textron SEL-57-09R1, which 
specifies a compliance time of 200 flight hours or the next annual 
inspection from date of receipt, whichever occurs first. Textron SEL-
57-09R1 applies to all Model 177-series airplanes identified in this 
service letter regardless of the total flight hours on the airframe. 
The compliance time specified in this AD aligns with the compliance 
time in Textron SEL-57-09R1 and there is no justification for aligning 
the compliance time with what is specified in the superseded Textron 
SEL-57-07.
3. Account for TIS
    Comment summary: Nine commenters requested that the proposed AD 
account for an airplane's TIS and one of those commenters noted that 
the accident airplane had a high number of hours TIS. Three of those 
commenters suggested a compliance time ranging from 2,500 hours TIS to 
12,000 hours TIS. Several commenters cited high costs as justification 
for only requiring airplanes with a high number of hours TIS to do the 
actions specified in the proposed AD.
    FAA response: The FAA disagrees with limiting the inspections 
required by this AD to airplanes with a high number of hours TIS. This 
AD is not based solely on the fatal 2019 accident in Australia 
involving a Model T210M airplane. As of January 13, 2023, there have 
been reports of corrosion on 120 Model 177-series airplanes, with at 
least 14 spars removed from service due to corrosion and damage of the 
lower cap, including a spar removed from service with less than 2,000 
hours TIS. Additionally, 460 Model 210-series airplanes have reported 
corrosion, with 64 spars removed from service due to corrosion and 
damage, including five removed from service with less than 3,000 hours 
TIS. Inspections based on TIS alone are not sufficient to identify and 
address corrosion, as corrosion is a function of calendar time. 
Corrosion can serve as a crack initiator, resulting in the spar being 
unable to carry the required load. Analysis completed by Textron

[[Page 9176]]

demonstrates this crack growth can happen under typical operation.
4. Align Compliance Time With Maintenance Schedules
    Comment summary: One commenter requested that the FAA allow the 
inspections to be completed when the inspection area is exposed for 
other maintenance. The FAA infers that the commenter is making this 
request to reduce costs and airplane down time.
    FAA response: The FAA acknowledges the commenter's request to limit 
maintenance access to reduce the time and money spent to comply with 
the requirements of this AD. However, the FAA considers this AD to be 
interim action and is still evaluating what actions must be required 
when issuing future rulemaking that will be considered final action to 
address the identified unsafe condition. During this evaluation, the 
FAA will consider if, for any future rulemaking, compliance times can 
be developed that correspond with scheduled maintenance; however, for 
this AD, the FAA does not agree with extending the compliance time for 
the entire fleet. The compliance time of this AD is within 200 hours 
TIS or 12 months after the effective date of this AD, whichever occurs 
first. This compliance time may allow the actions to be accomplished at 
the same time as regular maintenance, as the requirements of this AD 
can always be completed early. An owner, operator, or any interested 
party can apply for an AMOC to propose an adjustment of the compliance 
time using the procedures in paragraph (n) of this AD. The AMOC request 
must include substantiating data showing that the proposed AMOC 
provides an acceptable level of safety for a different method or 
adjustment of the compliance time to address the unsafe condition, 
other than the one specified in the AD.

F. Requests Regarding Requiring Actions To Align With Service 
Information

    Comment summary: Sixteen commenters requested that the FAA only 
require the actions specified in the Textron service information. One 
commenter stated that general aviation is struggling, and due to costs 
an AD should not require pilots to do any actions beyond those 
specified in the Textron service information. Two additional commenters 
mentioned the additional costs of repeating portions of the inspections 
in areas that differed between the Textron service information and the 
proposed AD. One commenter stated that the FAA should require the 
airplane manufacturer to create service information that will preserve 
the airworthiness of the carry-thru spar so compliance with the service 
information will count if the service information is included in an AD. 
Another commenter stated when the FAA overrides manufacturers' service 
information with ADs airplane owners would become less willing to use 
the information in future service bulletins because of concern that the 
FAA would require duplication of the actions in the service bulletins 
in an AD. One commenter stated that paragraph (g)(2) of the proposed AD 
negates the directions in paragraph (B)(2) of Textron SEL-57-09R1 
because the service letter states to ``Make sure to only remove the 
minimum material necessary to blend the corroded surface with the 
surrounding surface.''
    FAA response: The FAA disagrees that this AD should only require 
the actions specified in the Textron service information. After 
reviewing the procedures specified in that service information, the FAA 
determined that the unsafe condition could not be mitigated using only 
those procedures. Prior to the publication of the NPRM, the FAA 
received reports indicating that the visual inspection might not detect 
corrosion similar to that observed on the accident airplane. The 
fatigue crack on the accident airplane that caused the catastrophic 
failure of the carry-thru spar initiated at a corrosion pit 
approximately 0.011-inch deep. Cracking may be difficult to detect 
through visual inspection alone since the lower spar cap is in 
compression during the inspection. The eddy current inspection, 
however, could detect cracking from undetected corrosion or damage.
    The FAA disagrees that paragraph (g)(2) of this AD negates the 
directions in step 6.B.(2) of the Accomplishment Instruction in Textron 
SEL-57-09R1. Paragraph (g)(2) of this AD addresses removal or repair of 
the carry-thru spar due to evidence of previous blending. The FAA 
agrees with granting credit for blending previously completed using 
Textron service letters and the FAA acknowledges that owners, 
operators, and maintenance personnel could have proactively completed 
the actions described in the Textron service letters. The FAA has 
revised paragraph (l) of this AD to clarify credit for previous 
blending completed using the procedures in older revisions of the 
Textron service letters. Paragraph (f) of this AD already provides 
credit for blending action completed prior to the effective date of 
this AD using Textron SEL-57-08R2 or Textron SEL-57-09R1.
    The FAA agrees that alignment of a manufacturer's service documents 
and the requirements of an AD is ideal; however, the FAA cannot mandate 
a company to issue specific service information. Per 14 CFR 39.27, if 
an AD conflicts with the service document on which it is based, then 
the operator must follow the requirements of the AD. Additionally, the 
Textron service information clearly indicates that the compliance time 
presented might not apply to modified airplanes, including 
modifications that alter the airplane's design, gross weight, or 
airplane performance, including, but not limited to, installation of 
vortex generators, wing cuffs, short take-off and landing (STOL) kits, 
wing tips, and add-on wing fuel tanks. The FAA is responsible for 
considering the effects of these modifications on the airplanes 
included in the applicability of this AD.
    While the FAA cannot mandate that the service information be 
revised, nor can the agency wait on such information to address the 
unsafe condition, the FAA may allow an AMOC if the service information 
is revised and the FAA finds it acceptable to address the unsafe 
condition. If Textron revises its service information and the FAA 
determines that the revisions mitigate the unsafe condition, an owner, 
operator, or any interested party can apply for an AMOC using the 
procedures in paragraph (n) of this AD. The AMOC request must include 
substantiating data showing that the proposed AMOC provides an 
acceptable level of safety for a different method to address the unsafe 
condition, other than the one specified in the AD.
    The FAA has not changed this AD in regard to this issue.

G. Requests Regarding Limiting the AD to the Lower Carry-Thru Spar Cap

    Comment summary: Two individual commenters requested the 
requirements of the proposed AD be limited to inspections on the lower 
carry-thru spar cap. Another commenter supported the focus on the lower 
spar flange but noted that, in the proposed AD, mechanics could miss 
the statement that limits the scope of the inspection. One commenter 
acknowledged that the NPRM specified a mechanic is not required to 
inspect the lower cap to web radius, spar web, upper cap, or lugs, but 
that nothing excludes a mechanic from taking a spar out of service if 
any evidence of previous blending in those areas is found.
    FAA response: The FAA agrees with the commenter's requests to limit 
the requirements of this AD to inspections of the lower carry-thru spar 
cap and finds that, as written, the requirements of this AD are limited 
to inspections of the carry-thru spar lower cap including the lower 
surface, upper surface, and

[[Page 9177]]

edge. As detailed in paragraph (g) of this AD, inspecting the lower cap 
to web radius, spar web, upper cap, or lugs is not required. The 
preamble of this AD mentions that actions related to the web, upper 
caps, and lugs are not included as part of this AD. A mechanic may take 
a spar out of service during any inspection or maintenance event if the 
airplane is determined to not be airworthy to return to service.
    The FAA has not changed this AD in regard to this issue.

H. Requests Regarding Eddy Current Inspection

1. On-Condition Eddy Current Inspection
    Comment summary: Thirty-five commenters requested that the eddy 
current inspection of the carry-thru spar specified in paragraph (h) of 
the proposed AD only be required as an on-condition action when there 
is visual evidence of corrosion or damage. Three commenters stated that 
corrosion or cracking on the lower surface of the spar should be 
readily observable through a detailed visual inspection. Three 
commenters requested data justifying the eddy current inspection on 
airplanes that did not exhibit corrosion pitting on the carry-thru 
spar. One commenter asked why an airplane would need an eddy current 
inspection if the spar was delivered with a factory-applied protective 
coating, is clean and dry, and is not operated in an environment 
subject to moisture or other corrosion causing elements. Another 
commenter noted that over 300 visual inspections were completed on 
Model 177-series airplanes since the FAA identified this as a potential 
concern and none of the reports indicated that cracking was found. A 
different commenter requested that the FAA explain why it proposed 
expanding Textron's inspection requirements, which only specified eddy 
current inspections of the carry-thru spars if there were visual signs 
of corrosion, and asked if the FAA had significant evidence or 
engineering information indicating there could be internal corrosion or 
cracking even though it's not visible on the surface. One commenter 
stated that interpretation of the eddy current inspection results can 
be subjective. Two commenters requested requiring repetitive visual 
inspections instead of the eddy current inspection.
    FAA's response: The FAA disagrees with the commenters' requests to 
make the eddy current inspection an on-condition action in this AD or 
to only require repetitive visual inspections. Prior to the publication 
of the NPRM, the FAA reviewed inspection reports and determined that 
the visual inspection might not detect corrosion. On the Model T210M 
airplane involved in the accident that prompted the NPRM, the fatigue 
crack initiated at a corrosion pit approximately 0.011-inch deep. 
Cracking could be difficult to detect by only a visual inspection since 
the lower spar cap is in compression during that inspection, and the 
eddy current inspection could detect cracking from undetected corrosion 
or damage. The FAA acknowledges that it has not received any reports of 
cracking in the carry-thru spar lower cap on Model 177-series 
airplanes; however, out of the 211 inspection reports received by the 
FAA as of January 13, 2023, there have been 120 reports of corrosion 
and at least 14 carry-thru spars have been removed from service due to 
corrosion or damage.
    This AD requires that the technician completing the eddy current 
inspection be appropriately qualified as detailed in Textron Aviation 
Mandatory Service Letters SEL-57-08, Revision 2; and SEL-57-09, 
Revision 1.
    The FAA has not changed this AD in regard to this issue.
2. Limited Availability of Inspectors
    Comment summary: Several individual commenters expressed concern 
regarding the limited number of inspectors qualified and available of 
performing the eddy current inspection specified in the proposed AD. 
The commenters explained that it is difficult to locate qualified eddy 
current inspectors and for many airplane owners the inspectors are not 
local. One commenter requested that the FAA research how many 
facilities are willing to do the actions specified in the proposed AD 
and identify the lead time for scheduling the work.
    FAA response: The FAA acknowledges that finding a person or 
facility qualified to do an eddy current inspection could be difficult 
in some geographic regions. While the FAA does not maintain a 
comprehensive listing of all repair stations capable of completing the 
specific eddy current inspections required by this AD, you may search 
for a repair station by location and rating on the FAA website: av-info.faa.gov/repairstation.asp. The FAA has no way to accurately 
determine any specific facility's willingness and scheduling 
availability to complete work at a given time.
    As discussed above in section D., Requests Regarding Special Flight 
Permits, the FAA revised paragraph (m) of this AD to allow special 
flight permits with limitations. If scheduling an eddy current 
inspection is difficult, an owner, operator, or any interested party 
can apply for an AMOC using the procedures in paragraph (n) of this AD. 
The AMOC request must include substantiating data showing that the 
proposed AMOC provides an acceptable level of safety for a different 
method or adjustment of the compliance time to address the unsafe 
condition, other than the one specified in the AD. Also, the FAA has 
revised paragraph (g)(4) in this AD to allow airplanes without detected 
corrosion, cracking, or other damage, or evidence of previous corrosion 
removal to complete the actions required by paragraph (h) of this AD 
within 200 hours TIS after the effective date of this AD or within 12 
months after the effective date of this AD, whichever occurs first.

I. Requests Regarding Including a New Repetitive Inspection Requirement

    Comment summary: Three individual commenters requested that the 
proposed AD include repetitive inspections. One of the commenters 
requested requiring repetitive inspections instead of replacing carry-
thru spars that fail the inspection but do not have evidence of 
cracking. One of the commenters agreed that spars with cracking should 
be removed from service but a questionable spar with no cracking should 
be repetitively inspected instead of removed.
    FAA response: The FAA agrees that repetitive inspections might be 
appropriate for future rulemaking. The FAA considers this AD to be 
interim action and is still evaluating what actions must be required if 
future rulemaking is issued that will be considered final action. If 
the FAA determines that repetitive inspections are necessary, then they 
could be included as a requirement. Adding new requirements to this AD 
would require public comment before adopting a final rule, and would 
require publishing a supplemental NPRM. Because of the identified 
unsafe condition, the FAA does not agree to delay this AD.
    The FAA does not have data to support allowing carry-thru spars 
with excessive material removed to remain in service, even if they are 
repetitively inspected; however, the FAA would consider permitting 
individual carry-thru spars to remain in service and be repetitively 
inspected if an owner, operator, or any interested party applies for an 
AMOC using the procedures in paragraph (n) of this AD and includes 
substantiating data showing that the proposed AMOC provides an 
acceptable level of safety.

[[Page 9178]]

    The FAA has not changed this AD in regard to this issue.

J. Requests Regarding Removing Certain Requirements

1. Corrective Action Requirements
    Comment summary: Textron requested that paragraphs (h)(3) and (4) 
of the proposed AD, which address corrective actions for spars with 
damage or corrosion, be removed. Textron stated that these paragraphs 
are redundant because the inspection and rework specified in paragraph 
(g) of the proposed AD would have already addressed these actions.
    FAA response: The FAA does not agree because paragraphs (h)(3) and 
(4) of this AD provide directions for what to do if damage or corrosion 
are detected during the eddy current inspection required by paragraph 
(h) of this AD. Paragraph (g) of this AD requires a visual inspection 
with a 10X magnification lens looking for corrosion, cracking, and 
damage and provides directions for what to do if damage or corrosion 
are found during the visual inspection.
    The FAA has not changed this AD in regard to this issue.
2. Corrosion Protection Requirement
    Comment summary: An individual commenter stated that applying 
corrosion coating would be costly and disruptive for parts that do not 
need corrosion prevention. The FAA infers that the commenter is 
requesting that the requirement to apply corrosion coatings specified 
in the proposed AD be removed.
    FAA response: The FAA disagrees that the requirement in paragraph 
(i) of this AD to apply primer and CIC should be removed. Applying 
primer and CIC prevents corrosion and reduces the potential for crack 
initiation from corrosion. The carry-thru spar is a critical single 
load path structure with a demonstrated corrosion issue. Failure to 
sufficiently protect the structure from repeated corrosion increases 
the likelihood of additional cracking.
    The FAA has not changed this AD in regard to this issue.

K. Requests Regarding Credit for Previous Actions

1. Credit for Previous Blending
    Comment summary: AOPA, Cardinal Flyers Online, and several 
individual commenters requested that the proposed AD be revised to 
either give credit for previous blending done before the effective date 
of the final rule or to clarify what previous blending is acceptable. 
Three commenters requested that the proposed AD be revised to provide 
credit for carry-thru spars that were blended using the procedures 
specified in the Textron service letters instead of the requirement to 
replace a carry-thru spar or repair it using an AMOC. Ten commenters 
requested that the proposed AD be revised to allow previous blending of 
a carry-thru spar that is within the limits specified in the Textron 
service letters, even if the blending was not done using the procedures 
in the service letters. One commenter stated that it is unreasonable to 
require removal from service of a carry-thru spar with evidence of 
factory cleanup. The FAA infers that this commenter is requesting that 
carry-thru spars that have evidence of prior blending be permitted to 
remain in service.
    Three commenters stated that, in the proposed AD, the language was 
unclear regarding corrosion removed prior to the effective date of the 
AD using the procedures in the Textron service letters. Paragraph 
(g)(2) of the proposed AD would require that carry-thru spars with 
evidence of previous blending either be removed from service or 
repaired using an AMOC. The commenters noted that paragraph (l) of the 
proposed AD does grant credit for the visual inspection required by 
paragraph (g) of the proposed AD, but does not clearly identify if 
credit is allowed for any previous corrosion removal completed as a 
result of the visual inspection required by paragraph (g) of the 
proposed AD.
    Multiple commenters requested that the FAA provide credit for 
previous corrosion removal, even if logbook records are used. 
Commenters also raised the concern that owners who have made an effort 
to maintain a carry-thru spar in good condition would be penalized if 
the final rule fails to give credit for previous blending accomplished 
using the procedures in Textron SEL-57-08R2, or Textron SEL-57-09R1, as 
specified in paragraph (g) of the proposed AD. Ten commenters stated 
that previous blending should be covered by paragraph (g)(3) of the 
proposed AD and that all previous corrosion removal that does not 
exceed the blend limits specified in Textron SEL-57-08R2 and Textron 
SEL-57-09R1 should be permitted. Several commenters stated that the 
language in paragraph (l) of the proposed AD was as ambiguous and may 
penalize those parties who took action prior to publication of the 
final rule. Several commenters stated that most carry-thru spars were 
blended to some extent at the factory and that other carry-thru spars 
were blended using guidance from Textron.
    To justify allowing the blended carry-thru spars to remain in 
service, one commenter provided information from an industry forum and 
from experience working with cast aluminum to support the view that 
Cessna blended carry-thru spars prior to delivery. This same commenter 
also cited concerns regarding the time needed to obtain an AMOC.
    FAA response: The FAA partially agrees with the commenters' 
requests. The FAA agrees with granting credit for the blending of 
carry-thru spars completed prior to the effective date of this AD using 
Textron SEL-57-08R2 and Textron SEL-57-09R1, and the FAA acknowledges 
that some owners, operators, and maintenance personnel proactively 
complied with the procedures in that service information; however, 
compliance with previous actions is already addressed and no change is 
needed to this AD because paragraph (f) of this AD states ``Comply with 
this AD within the compliance times specified, unless already done.''
    The FAA also agrees to revise paragraphs (l)(1) and (2) of this AD 
to clarify that owners and operators may take credit for corrosion 
removal (blending) completed before the effective date of this AD using 
the procedures in Textron Aviation Mandatory Single Engine Service 
Letter SEL-57-08, dated November 1, 2019 (Textron SEL-57-08); Textron 
Aviation Mandatory Single Engine Service Letter SEL-57-08, Revision 1, 
dated November 19, 2019 (Textron SEL-57-08R1); Textron Aviation 
Mandatory Single Service Letter SEL-57-09, dated November 19, 2019 
(Textron SEL-57-09); Textron SEL-57-06; Textron Aviation Mandatory 
Single Engine Service Letter SEL-57-06, Revision 1, dated November 19, 
2019 (Textron SEL-57-06R1); Textron SEL-57-07; or Textron SEL-57-07R1.
    The FAA disagrees allowing credit for blending completed prior to 
the release of Textron SEL-57-06 and Textron SEL-57-07 without an 
evaluation and a repair approved as an AMOC. While the FAA does not 
have data supporting that Cessna blended the forged carry-thru spars 
prior to delivery, the FAA does recognize that some carry-thru spars 
were blended prior to publication of the NPRM. Blend limits, blend 
ratios, and surface finish must be addressed in the AMOC request. 
Locations previously blended that are included in the AMOC request will 
still be required to complete the eddy current inspection or provide 
evidence of previous completion.

[[Page 9179]]

2. Clarifying Credit for Previous Actions
    Comment summary: Ten individual commenters requested clarification 
regarding credit for previous actions. Four commenters stated that 
paragraph (l) in the proposed AD was unclear. Seven commenters 
requested the FAA give credit for previous actions and not require that 
the actions be duplicated. One commenter stated that the proposed AD 
should provide full credit for any previous corrosion remediation 
performed using accepted maintenance procedures, so owners who 
previously addressed corrosion on their airplane are not punished.
    FAA response: The FAA agrees that credit should be granted for work 
previously accomplished using the procedures in the Textron service 
letters and, as stated previously, the FAA has revised paragraph (l) of 
this AD to clarify that owners and operators may take credit for 
previously accomplished visual inspections and corrosion removal if 
completed in accordance with Textron service letters. The FAA finds 
that owners and operators are not being required to duplicate actions 
because paragraph (f) of this AD states ``Comply with this AD within 
the compliance times specified, unless already done;'' therefore, 
compliance for previous actions is granted to those who completed the 
required actions prior to the effective date of this AD in accordance 
with the applicable steps of the Accomplishment Instructions in Textron 
SEL-57-08R2 and Textron SEL-57-09R1.
    Operators that performed repairs using accepted maintenance 
practices other than the Textron service letters must apply for an 
AMOC.

L. Requests Regarding AMOCs

1. Repair
    Comment summary: One commenter requested clarification regarding 
what kinds of carry-thru spar repairs the FAA would approve through the 
AMOC process. The commenter stated that paragraph (o) of the proposed 
AD did not identify what kind of repairs might be acceptable and that 
the proposed AD left the decision for acceptable AMOCs to Textron, even 
though the FAA says Textron's corrective action identified in Textron 
SEL-57-09R1 is not adequate. The commenter explained that the lack of 
definition in paragraph (o) of the proposed AD regarding acceptable 
repairs makes it difficult for owners to estimate the condition of 
their carry-thru spars.
    FAA response: The FAA disagrees that paragraph (n) of this AD 
(paragraph (o) in the proposed AD), requires clarification. The FAA has 
defined an acceptable repair based on available data. If the FAA knew 
of additional standard repairs, then those repairs would have been 
reviewed and, if found acceptable, included in this AD.
    This AD specifies the same material removal limits as those 
identified in Textron SEL-57-09R1. It is possible that spars with 
damage that cannot be removed within the limits identified in Table 1 
of Textron SEL-57-09R1 could still be found acceptable based on further 
evaluation. A repair on a carry-thru spar for which the material 
removed exceeds that identified in Table 1 of Textron SEL-57-09 would 
require an AMOC. Generally, the FAA, not Textron, must approve AMOCs; 
however, in this AD the FAA has delegated to Textron's Organization 
Designation Authorization the authority to evaluate carry-thru spars 
with material removal beyond that identified in Textron SEL-57-09R1 to 
salvage as many spars as possible. Textron might choose not to evaluate 
modified airplanes, as detailed in Textron SEL-57-09R1 and Textron SEL-
57-08R2. Additionally, there is no requirement for an operator to have 
its spar evaluated by Textron. The owner or operator may develop its 
own AMOC request to present to the FAA for evaluation of any repair for 
which there is substantiating data.
    The FAA would not limit AMOC options by defining those that are 
acceptable, as it is unrealistic for the FAA to preemptively identify 
and evaluate any potential AMOC option that may or may not be 
applicable to an airplane.
    The FAA has not changed this AD in regard to this issue.
2. Alternative Inspection Method
    Comment summary: Cardinal Flyers Online and four individual 
commenters requested that instead of the eddy current inspection a 
visual inspection be allowed with the airplane on jacks. The commenters 
explained that putting the wings on jacks would place the lower spar 
cap in tension, allowing cracking to be seen more readily during the 
visual inspection. One commenter proposed using a dye penetrant 
inspection in addition to supporting the wings with jacks.
    FAA response: The FAA acknowledges that other inspection methods 
could be used for the carry-thru spar inspection; however, the FAA does 
not have data to support including these alternative inspection methods 
in this AD. An owner, operator, or any interested party may develop 
inspection procedures and submit an AMOC request to the FAA along with 
substantiating data showing that the proposed AMOC addresses the unsafe 
condition with an acceptable level of safety.
    The FAA has not changed this AD in regard to this issue.
3. Alternative Corrosion Protection Options
    Comment summary: Three commenters requested that the proposed AD 
allow for alternative corrosion protection options in addition to those 
specified in the proposed AD. Two of those commenters stated that the 
corrosion coatings specified in the proposed AD need to be expanded to 
include other products typically used in aviation and not just those 
identified by Textron. One commenter stated that a carry-thru spar that 
has been fully anodized and inspected should be equivalent to or better 
than a carry-thru spar with coating applied.
    FAA response: The FAA agrees that alternative coating options could 
be acceptable. Using the procedures in paragraph (n) of this AD an 
owner, operator, or any interested party is welcome to identify an 
alternative coating and submit an AMOC request to the FAA along with 
substantiating data showing that the proposed AMOC addresses the unsafe 
condition with an acceptable level of safety.

M. Requests Regarding Cost Estimates

1. Labor Rate Is Unrealistic
    Comment summary: Eight commenters requested the FAA increase the 
cost per hour estimates for the labor rate because $85 per work-hour is 
too low, does not reflect the true rate of labor, and is not 
attainable. One commenter requested that the FAA publish the method 
used to derive the hourly rate charged by maintenance shops.
    FAA response: The FAA partially agrees with the commenters' 
requests. The FAA Office of Aviation Policy and Plans provides the 
labor rate of $85 per work-hour to use when estimating the labor costs 
of complying with the AD requirements. The FAA does agree to alter the 
estimated cost of the eddy current inspection from $85 per work-hour to 
a flat rate of $600 for one work-hour of contracted service to more 
accurately reflect the cost of eddy current inspection. The FAA revised 
the estimated costs and on-conditions costs tables in this AD to 
account for the $600 per work-hour contracted service associated with 
the eddy current inspection.

[[Page 9180]]

2. Estimated Work-Hours
    Comment summary: Aviation Plus LLC and several individual 
commenters requested that the FAA increase the estimated number of 
work-hours for doing the carry-thru spar inspections because the 
estimated work-hours specified in the NPRM are too low and do not 
include on-condition costs for removing the oxygen systems and air 
conditioning systems for access to the inspection area. Two commenters 
stated that the costs to remove the airplane interior for access to do 
the inspections are not accurate. One commenter wanted to know the 
source of the estimated work-hours.
    Eleven commenters requested that the proposed estimated cost for 
the eddy current inspection be increased and noted that the cost should 
include travel time to the grounded airplane or the cost to bring the 
eddy current inspector to the airplane.
    One of these commenters stated that a flat rate is usually charged 
for an eddy current inspection, and four of these commenters stated 
that the cost range is usually between $400 and $1,000. The commenters 
provided various reasons for their requests.
    FAA response: The FAA agrees that some of the estimated costs in 
this AD should be revised.
    Textron provided the original estimated work-hours for preparing, 
inspecting, and reassembling an airplane. The FAA observed inspections 
completed by maintenance facilities and verified the personnel were 
able to complete the work within the estimates provided by Textron 
Aviation. The FAA acknowledges there is variability in the time 
necessary to complete the work, depending on a number of factors 
including airplane configuration and condition and the experience and 
capabilities of the individual(s) performing the work. The cost 
estimates provided in the NPRM did not include travel time to the 
grounded airplane or the cost to bring the eddy current inspector to 
the airplane.
    The FAA partially agrees with the commenters' requests and has 
increased the estimated work-hours from 12 hours to 20 hours for 
removing and reinstalling the interior, removing the foam as 
applicable, and preparing the spar for visual and eddy current 
inspections. Additionally, in the Estimated costs table in this final 
rule the FAA has separated the eddy current inspection of the cap kick 
area into a separate line item with an estimate of $600 for contracted 
service work-hours and in the On-condition costs table included a line 
item for the on-condition eddy current inspection required due to 
corrosion or damage with an estimate of $600 for contracted service 
work-hours. Furthermore, the FAA added an additional line item that 
includes 5 work-hours for airplanes equipped with oxygen bottles and an 
additional line item that includes 3 work-hours for airplanes equipped 
with air conditioning.
2. Costs of Replacement Parts
    Comment summary: Four commenters discussed the availability and 
cost of replacement carry-thru spars. The commenters wanted to know how 
the FAA determined the estimate of $30,000 for a replacement carry-thru 
spar. Another commenter stated that replacement carry-thru spars are 
not available from the manufacturer and the cost estimate for a 
replacement spar is low. The FAA infers that these commenters are 
requesting that the cost estimate for a replacement carry-thru spar be 
increased.
    FAA's response: Textron provided the $30,000 cost estimate for a 
replacement carry-thru spar and has informed the FAA of its intention 
to start producing replacement carry-thru spars for Model 177-series 
airplanes. Textron is currently producing replacement carry-thru spars 
for Model 210-series airplanes, with a current cost of $21,367 for part 
number (P/N) 1210721-1 and $19,999 for P/N 2110020-1. The FAA revised 
the cost for a replacement carry-thru spar for Model 210-series 
airplanes to reflect these actual part costs.
3. Textron Share the Costs
    Comment summary: One commenter requested that Textron share the 
costs of the inspections. The commenter explained that the corrosion 
issue exists because of Textron's carry-thru spar design, which permits 
leaking and condensation, and because Textron did not apply anti-
corrosion coatings during manufacture.
    FAA response: The FAA has no authority to enforce business 
contracts (actual or implied) between parties. The primary concern the 
FAA has when issuing an AD is addressing unsafe conditions on various 
aircraft flying in the United States. The FAA provides estimated costs 
information for complying with the requirements of an AD but does not 
control warranty coverage and cannot mandate that a manufacturer cover 
all associated costs.
    The FAA has not changed the AD in regard to this issue.

N. Requests Regarding Primer and CIC Removal

    Comment summary: Ten individual commenters requested that the 
proposed AD not require the removal of previously applied primer and 
CIC. The commenters stated that removing the previously applied primer 
and CIC could damage the carry-thru spar and would result in 
duplication of effort, increase in cost, and lack of credit granted for 
previous actions.
    FAA response: The FAA agrees with the commenters' requests and this 
AD does not require removing properly applied primer and CIC that is in 
good condition. Paragraph (l) of this AD provides credit for previous 
actions, including the application of primer and CIC.
    The FAA has not changed this AD in regard to this issue.

O. Request Regarding Spar Structural Capability

    Comment summary: One commenter asked how much force is needed to 
break a carry-thru spar that does not pass an eddy current inspection.
    FAA response: The FAA has no way of knowing precisely how much 
force would be required to break a carry-thru spar for which an eddy 
current inspection identified a response as detailed in Textron 
Aviation Mandatory Service Letters SEL-57-08R2 or SEL-57-09R1. The 
residual strength capability of the carry-thru spar is dependent on the 
type and amount of damage located on the part, as well as the specific 
geometry of the part.
    The FAA has not changed this AD in regard to this issue.

P. Requests Regarding Limiting Spar Replacement

    Comment summary: Two commenters requested that the FAA only require 
carry-thru spar replacement if absolutely necessary. The commenters 
explained that replacing a carry-thru spar could introduce additional 
safety issues because this action requires disassembling and 
reassembling major components, including the airframe, partial fuel and 
electrical systems, control systems, and structural repairs. One of the 
commenters mentioned that replacement carry-thru spars are difficult to 
find.
    FAA response: The FAA acknowledges that replacing a carry-thru spar 
is a significant and costly effort and could be difficult to find. The 
FAA encourages owners, operators, and any interested party to pursue 
repair options prior to replacing an affected carry-thru spar and has 
provided a

[[Page 9181]]

means to apply for an AMOC using the procedures provided in paragraph 
(n) of this AD. The FAA has not changed this AD in regard to this 
issue.

Q. Requests Regarding Clarifying Minimum Part Thickness

    Comment summary: Two individual commenters requested that the 
proposed AD specify the minimum acceptable part thickness after a 
carry-thru spar is reworked instead of setting a limit on the maximum 
amount of material that can be removed during rework. One commenter 
stated that the carry-thru spars were not manufactured with tight 
tolerances and could be thicker than the specification, allowing for 
more material to be removed. The other commenter stated that measuring 
the amount of material removed could be difficult if blending was done 
over a large area and suggested using data previously released by 
Textron that specified thickness limits for various stations along the 
spar.
    FAA response: The FAA agrees that for Model 210- and 177-series 
airplanes, the forged 2014-T6 aluminum carry-thru spars have a wide 
range of manufacturing tolerances, both above and below the dimensions 
identified in the design data. The FAA also agrees that additional 
material, beyond that identified in Table 1 of Textron SEL-57-08R2 and 
Textron SEL-57-09R1, may be removed on some spars. However, the amount 
of additional material that can be removed varies from one spar to 
another and must be evaluated on an individual basis.
    The FAA determined that applying the thickness limits identified in 
data previously released by Textron for various stations along the spar 
must be evaluated on an individual airplane basis, as that information 
was not originally developed to address the unsafe condition identified 
in this AD. The FAA encourages an owner, operator, or interested party 
with a corroded or damaged carry-thru spar that exceed the limits 
identified in Table 1 of Textron SEL-57-08R2 and Textron SEL-57-09R1 to 
apply for an AMOC using the procedures in paragraph (n) of this AD. The 
AMOC request must include substantiating data showing that the proposed 
AMOC addresses the unsafe condition with an acceptable level of safety.
    The FAA agrees that measuring the amount of material removed may be 
challenging and Textron provided suggestions for measuring the amount 
of material removed in step 6.B.(8) of the Accomplishment Instructions 
in Textron SEL-57-08R2 and Textron SEL-57-09R1. Additional guidance may 
be obtained by contacting Textron as detailed in paragraph (n)(3) of 
this AD.
    The FAA has not changed this AD in regard to this issue.

R. Comment Regarding Reliability Centered Maintenance

    Comment summary: One commenter suggested that the FAA find a 
solution to address the unsafe condition identified in the NPRM that 
promotes reliability centered maintenance (RCM). The commenter 
explained that RCM is a concept of maintenance planning to ensure that 
systems continue to do what their users require in their present 
operating context. Successful implementation of RCM will lead to 
increase in cost effectiveness, reliability, machine uptime, and a 
greater understanding of the level of risk that the organization is 
managing. The commenter stated that blanket ADs cost the general 
aviation community millions of dollars but do not increase safety, 
instead they increase risk by requiring unnecessary and invasive 
maintenance.
    FAA response: The FAA lacks sufficient substantiating data to allow 
RCM for this AD. An owner, operator, or interested party can request to 
use RCM by applying for an AMOC using the procedures in paragraph (n) 
of this AD. The AMOC request must include substantiating data showing 
that the proposed AMOC addresses the unsafe condition with an 
acceptable level of safety.
    The FAA has not changed this AD in regard to this issue.

S. Comment Regarding Tubing Corrosion

    Comment summary: One commenter stated that the tubing corrosion 
issue only applies to a few airplanes rather than the entire fleet. The 
commenter did not request a change to the NPRM.
    FAA response: Corrosion associated with tubing usually occurs in 
the web of the carry-thru spar, and this AD only requires inspecting 
the carry-thru spar lower cap. Although this AD does not specifically 
apply to corrosion associated with tubing, any corrosion found on the 
carry-thru spar lower cap, regardless of origin, is required to be 
addressed.
    The FAA has not changed this AD in regard to this issue.

Additional Changes to This AD

    The FAA did not carry over paragraph (l)(4) from the Credit for 
Previous Actions paragraph in the proposed AD into this AD. The FAA did 
not take away credit but removed a restriction. In the proposed AD, 
paragraph (l)(4) specified that, to receive credit, the protective 
coating and CIC had to have been applied to the airplane within 24 
months after the date of completing the visual and eddy current 
inspection or within 12 months after the effective date of the AD, 
whichever occurs first. By the effective date of this final rule many 
airplanes will have completed the visual and eddy current inspections 
longer than 24 months ago. The airplanes in the applicability of this 
AD are not as likely to develop corrosion as the Model 210G through 
Model 210M airplanes that were included in the applicability of AD 
2020-03-16 (the immediately adopted rule discussed previously), so the 
FAA determined that the requirement of corrosion application within 24 
months after the visual and eddy current inspections was not necessary. 
The FAA did not want to penalize operators who had already completed 
the eddy current inspection by requiring they do the inspection again 
because they were outside of the 24-month limit. However, the 
requirement in paragraph (i) of this AD that CIC must be applied within 
12 months after the effective date of this AD is unchanged.
    Paragraph (h) of the proposed AD did not have explicit compliance 
times for completing the eddy current inspections, relying on paragraph 
(g) for the applicable compliance times for the eddy current 
inspections. For clarity, paragraph (h) now points to paragraph (g) for 
compliance times.

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 the changes discussed 
previously, omitting the Paperwork Reduction Act Burden Statement, 
paragraph (n) in the proposed AD, and reidentifying the subsequent 
paragraphs, this AD is adopted as proposed in the NPRM. None of the 
changes will increase the economic burden on any operator.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed the following service documents:
     Textron Aviation Mandatory Single Engine Service Letter, 
SEL-57-08, Revision 2, dated August 3, 2020 (Textron SEL-57-08R2); and
     Textron Aviation Mandatory Single Engine Service Letter, 
SEL-57-09, Revision 1, dated August 3, 2020 (Textron SEL-57-09R1).

[[Page 9182]]

    For the applicable airplanes specified, these service letters 
contain instructions for visually inspecting the carry-thru spar for 
corrosion, damage, and cracking and for completing an eddy current 
inspection. This service information also specifies applying protective 
coating and CIC.
    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 the ADDRESSES section.

Other Related Service Information

    The FAA reviewed the following service letters related to this AD 
which, for the applicable airplanes specified, contain instructions for 
visually inspecting the carry-thru spar for corrosion and doing an eddy 
current inspection of the carry-thru spar regardless of whether 
corrosion was found and removed. This service information also contains 
instructions for applying CIC, but does not specify applying protective 
coating.
     Textron Aviation Mandatory Single Engine Service Letter, 
SEL-57-06, dated June 24, 2019 (Textron SEL-57-06);
     Textron Aviation Mandatory Single Engine Service Letter, 
SEL-57-06, Revision 1, dated November 19, 2019;
     Textron Aviation Mandatory Single Engine Service Letter, 
SEL-57-07, dated June 24, 2019 (Textron SEL-57-07); and
     Textron Aviation Mandatory Single Engine Service Letter, 
SEL-57-07, Revision 1, dated November 19, 2019.
    The FAA also reviewed the service letters listed below related to 
this AD, which, for the applicable airplanes specified, contain the 
same instructions and repair criteria as Textron SEL-57-08R2 and 
Textron SEL-57-09R1.
     Textron Aviation Mandatory Single Engine Service Letter, 
SEL-57-08, dated November 1, 2019;
     Textron Aviation Mandatory Single Engine Service Letter, 
SEL-57-08, Revision 1, dated November 19, 2019; and
     Textron Aviation Mandatory Single Engine Service Letter, 
SEL-57-09, dated November 19, 2019.

Differences Between This AD and the Service Information

     Although Textron SEL-57-08R2 also applies to Models 210G, 
T210G, 210H, T210H, 210J, T210J, 210K, T210K, 210L, T210L, 210M, and 
T210M airplanes, this AD does not. The FAA issued AD 2020-03-16 to 
address the immediate safety of flight for those airplanes.
     Textron SEL-57-08R2 and Textron SEL-57-09R1 specify 
inspecting all interior surfaces of the carry-thru spar; additionally, 
Textron SEL-57-09R1 specifies inspecting the lower surface of the 
outboard spar to wing attach lugs. This AD only requires inspecting the 
carry-thru spar lower cap, including the lower surface, edge, and upper 
surface of the lower cap. While the web, upper cap, and lugs of the 
carry-thru spar may be susceptible to corrosion, evidence does not 
support including inspection of these areas as part of this AD. The FAA 
will continue to monitor reports of corrosion on all areas of the 
carry-thru spar for potential future action.
     Textron SEL-57-08R2 and Textron SEL-57-09R1 do not specify 
an eddy current inspection on the carry-thru spar unless the amount of 
material removed in the blended area exceeds 0.010-inch deep but is 
within limits. This AD requires an eddy current inspection of all 
locations on the carry-thru spar lower cap where corrosion was removed. 
The fatigue crack on the Model T210M airplane that suffered the fatal 
in-flight break-up initiated from a corrosion pit approximately 0.011-
inch deep in the lower cap kick area. The visual and less restrictive 
eddy current inspection requirements specified in Textron SEL-57-08R2 
and Textron SEL-57-09R1 could miss similar fatigue cracking on 
airplanes currently operating in the field.
     Textron SEL-57-08R2 and Textron SEL-57-09R1 only specify 
an eddy current inspection of the lower cap kick of the carry-thru spar 
if corrosion is identified on the carry-thru spar cap. This AD requires 
a one-time eddy current inspection of the lower cap kick area of all 
affected airplanes, regardless of the results of the visual inspection. 
The fatigue crack on the Model T210M airplane that suffered the fatal 
in-flight break-up initiated in the lower cap kick area. Cracking and 
corrosion damage may be difficult to identify through visual inspection 
alone. The FAA will use the results of the one-time eddy current 
inspection of the lower cap kick area, in part, to determine the 
necessity of future rulemaking action.
     Textron SEL-57-08R2 and Textron SEL-57-09R1 specify 
contacting Textron for evaluation and disposition of certain damage. 
Instead, this AD requires removing the carry-thru spar from service or 
repairing it (if possible) in accordance with the AMOC procedures 
identified in paragraph (n) of this AD. Operators should work with 
Textron to develop a repair in support of an AMOC request.
     Textron SEL-57-08 R2 and Textron SEL-57-09R1 provide 
instruction allowing airplanes that have complied with Textron SEL-57-
06 or Textron SEL-57-07 to complete the application of the protective 
coating and CIC within 200 flight hours or at the next annual 
inspection, whichever occurs first. This AD permits applying protective 
coating and CIC within 12 months after the effective date of this AD.

Interim Action

    The FAA considers this AD to be an interim action. This AD requires 
one-time visual and eddy current inspections of the carry-thru spar 
lower cap for corrosion, cracking, and damage, corrective action if 
necessary, applying a protective coating and CIC, and reporting the 
inspection results to the FAA. The FAA will analyze the inspection 
results received to determine further rulemaking action.

Costs of Compliance

    The FAA estimates that this AD affects 3,421 airplanes of U.S. 
registry.
    The FAA estimates the following costs to comply with this AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                  Cost per        Cost on U.S.
             Action                  Labor cost             Parts cost            airplane         operators
----------------------------------------------------------------------------------------------------------------
Inspection (includes part        20 work-hours x     Not applicable..........          $1,700  $5,815,700.
 removal for access, removal of   $85 per hour =
 foam, if required, visual        $1,700.
 inspection, and reassembly).
Eddy current inspection of the   1 work-hour         Not applicable..........             600  $2,052,600.
 cap kick area.                   contracted
                                  service x $600 =
                                  $600.
Spar treatment (primer and       3.50 work-hours x   $340....................          637.50  $2,180,887.50.
 corrosion inhibitor) *.          $85 per hour =
                                  $297.50.

[[Page 9183]]

 
Removal and reinstallation of    5 work-hours x $85  Not applicable..........             425  Up to $1,453,925
 oxygen bottles **.               per hour = $425.                                              (not all
                                                                                                airplanes have
                                                                                                oxygen bottles
                                                                                                installed).
Removal and reinstallation of    3 work-hours x $85  Not applicable..........             255  Up to $872,355
 air conditioning components **.  per hour = $255.                                              (not all
                                                                                                airplanes have
                                                                                                air conditioning
                                                                                                installed).
Reporting requirement..........  2 work-hours x $85  Not applicable..........             170  $581,570.
                                  per hour = $170.
----------------------------------------------------------------------------------------------------------------
* Model 210-series airplanes may only require application of corrosion inhibitor, depending on the condition of
  the zinc chromate primer. Model 177-series airplanes may or may not require application of the primer,
  depending on the production year and the quality of any existing zinc chromate primer.
** Some Model 210-series airplanes are equipped with oxygen bottles in the area of the carry-thru spar. Some
  Model 210- and 177-series airplanes are equipped with air conditioning systems. Additional work-hours were
  included in the estimated costs to account for the additional time required to complete the AD requirements on
  these airplanes.

    The FAA estimates the following costs to do any necessary repairs 
or replacements that would be required based on the results of the 
proposed inspection. The agency 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
----------------------------------------------------------------------------------------------------------------
Corrosion removal....................  2 work-hours x $85 per    Not applicable.................            $170
                                        hour = $170.
On-condition eddy current inspection.  1 work-hour contracted    Not applicable.................             600
                                        service x $600 = $600.
Spar replacement--Model 210/T210-      160 work-hours x $85 per  $21,367........................          34,967
 airplanes (P/N 1210721-1).             hour = $13,600.
Spar replacement--Model 210/T210-      160 work-hours x $85 per  $19,999........................          33,599
 airplanes (P/N 2110020-1).             hour = $13,600.
Spar replacement--Model P210 airplane  220 work-hours x $85 per  $19,999........................          38,699
                                        hour = $18,700.
Spar replacement--Model 177-series     120 work-hours x $85 per  $30,000........................          40,200
 airplane.                              hour = $10,200.
----------------------------------------------------------------------------------------------------------------

    The amount of work-hours necessary to complete the eddy current 
inspection and corrosion removal will depend on the extent of the 
corrosion on the carry-thru spar. The FAA has no way of estimating the 
work-hours that may be required for those procedures. The FAA's cost 
estimate assumes a minimum of one hour contracted service for the eddy 
current inspection and two hours for the corrosion removal. If the 
operator needs an AMOC for repair, the FAA has no way of estimating the 
extent of damage or follow-on eddy current inspection that may be 
required. The FAA has no way of estimating the potential cost of those 
actions.
    Replacement carry-thru spars are not currently available from 
Textron for Model 177-series airplanes. Textron no longer produces the 
current carry-thru spar design and is developing a new design. The FAA 
does not have data to determine the availability of replacement carry-
thru spars from other sources.

Paperwork Reduction Act

    A federal agency may not conduct or sponsor, and a person is not 
required to respond to, nor shall a person be subject to a penalty for 
failure to comply with a collection of information subject to the 
requirements of the Paperwork Reduction Act unless that collection of 
information displays a currently valid OMB Control Number. The OMB 
Control Number for this information collection is 2120-0056. Public 
reporting for this collection of information is estimated to take 
approximately 1 hour per response, including the time for reviewing 
instructions, searching existing data sources, gathering and 
maintaining the data needed, and completing and reviewing the 
collection of information. All responses to this collection of 
information are mandatory. Send comments regarding this burden estimate 
or any other aspect of this collection of information, including 
suggestions for reducing this burden to: Information Collection 
Clearance Officer, Federal Aviation Administration, 10101 Hillwood 
Parkway, Fort Worth, TX 76177-1524.

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,

[[Page 9184]]

    (2) Will not affect intrastate aviation in Alaska, and
    (3) Will not have a significant economic impact, positive or 
negative, on a substantial number of small entities under the criteria 
of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

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

The Amendment

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

PART 39--AIRWORTHINESS DIRECTIVES

0
1. The authority citation for part 39 continues to read as follows:

    Authority:  49 U.S.C. 106(g), 40113, 44701.


Sec.  39.13   [Amended]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive:

2023-02-17 Textron Aviation Inc. (Type Certificate previously held 
by Cessna Aircraft Company): Amendment 39-22324; Docket No. FAA-
2020-1078; Project Identifier AD-2020-00716-A.

(a) Effective Date

    This airworthiness directive (AD) is effective March 20, 2023.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to Textron Aviation Inc. (Type Certificate 
previously held by Cessna Aircraft Company) Model 210N, 210R, P210N, 
P210R, T210N, T210R, 177, 177A, 177B, 177RG, and F177RG airplanes, 
all serial numbers, certificated in any category.

(d) Subject

    Joint Aircraft System Component (JASC) Code 5310, Fuselage Main, 
Structure.

(e) Unsafe Condition

    This AD was prompted by the in-flight break-up of a Model T210M 
airplane, due to fatigue cracking of the carry-thru spar that 
initiated at a corrosion pit and subsequent corrosion reports on 
other Model 210-series and Model 177-series airplanes. The FAA is 
issuing this AD to detect and correct cracking, corrosion, and other 
damage of the carry-thru spar lower cap, which, if not corrected, 
could lead to the carry-thru spar being unable to support the 
required structural loads and could result in separation of the wing 
and loss of airplane control.

(f) Compliance

    Comply with this AD within the compliance times specified, 
unless already done.

(g) Visual Inspection

    Within 200 hours time-in-service (TIS) after the effective date 
of this AD or within 12 calendar months after the effective date of 
this AD, whichever occurs first, prepare the carry-thru spar lower 
cap for inspection by following steps 4 and 5 of the Accomplishment 
Instructions in Textron Aviation Mandatory Single Engine Service 
Letter, SEL-57-08, Revision 2, dated August 3, 2020 (Textron SEL-57-
08R2); or Textron Aviation Mandatory Single Engine Service Letter, 
SEL-57-09, Revision 1, dated August 3, 2020 (Textron SEL-57-09R1), 
as applicable to your airplane model. Visually inspect the carry-
thru spar lower cap (including the lower surface, upper surface, and 
edge) with a 10X magnification lens looking for corrosion, cracking, 
and damage. You are not required to inspect the lower cap to web 
radius, spar web, upper cap, or lugs. Refer to the `Spar Dimensions' 
and the `Spar Detail' figures on page 7 of Textron SEL-57-08R2 or 
Textron SEL-57-09R1, as applicable to your airplane model, for the 
location of the specific spar features.
    (1) If there is any cracking, before further flight, remove the 
carry-thru spar from service.
    (2) If there is damage or evidence of previous removal of 
corrosion (blending), before further flight, either remove the 
carry-thru spar from service or repair the area using a method 
approved as specified in paragraph (n) of this AD. Comply with the 
requirements in paragraph (h) of this AD before further flight.
    (3) If there is any corrosion, before further flight, remove the 
corrosion in the affected area by following steps 6.B.(1) through 
(7) of the Accomplishment Instructions in Textron SEL-57-08R2 or 
Textron SEL-57-09R1, as applicable to your airplane model, and then 
mechanically measure the depth of the blended area using a straight 
edge and feeler gauge or a depth gauge micrometer.
    (i) If the material removed in the blended area exceeds the 
allowable blend limits specified in table 1 (including the notes) of 
Textron SEL-57-08R2 or Textron SEL-57-09R1, as applicable to your 
airplane model, before further flight, either remove the carry-thru 
spar from service or repair the area using a method approved as 
specified in paragraph (n) of this AD. Comply with the requirements 
in paragraph (h) of this AD before further flight.
    (ii) If the material removed in the blended area does not exceed 
the allowable blend limits specified in table 1 (including the 
notes) of Textron SEL-57-08R2 or Textron SEL-57-09R1, as applicable 
to your airplane model, comply with the requirements in paragraph 
(h) of this AD before further flight.
    (4) If the visual inspection did not detect corrosion, cracking, 
or damage and there is no evidence of previous removal of corrosion, 
comply with the requirements in paragraph (h) of this AD within 200 
hours TIS after the effective date of the AD or within 12 calendar 
months after the effective date of the AD, whichever occurs first.

(h) Eddy Current Inspection

    (1) At the applicable compliance time required by paragraph (g) 
of this AD, complete an eddy current inspection of the carry-thru 
spar lower cap for cracking, corrosion, and damage in the following 
areas in accordance with step 7 of the Accomplishment Instructions 
in Textron SEL-57-08R2 or Textron SEL-57-09R1, as applicable to your 
airplane model.
    (i) The kick area as depicted in the `Spar Dimensions' figure on 
page 7 of Textron SEL-57-08R2 or Textron SEL-57-09R1, as applicable 
to your airplane. You must complete an eddy current inspection of 
the lower cap kick area of your airplane regardless of whether 
corrosion was found and removed as a result of the visual inspection 
in paragraph (g) of this AD.
    (ii) All areas where corrosion was found and removed as a result 
of the inspection in paragraph (g) of this AD.
    (2) If there is any cracking, before further flight, remove the 
carry-thru spar from service.
    (3) If there is any damage, before further flight, either remove 
the carry-thru spar from service or repair the area using a method 
approved as specified in paragraph (n) of this AD. After completing 
the repair, repeat the eddy current inspection of the repaired area 
before further flight.
    (4) If there is any corrosion, before further flight, remove the 
corrosion by following the requirements in paragraph (g)(3) of this 
AD. You must repeat the eddy current inspection and comply with 
paragraph (h) of this AD for the area where the additional material 
was removed, but you do not have to repeat the eddy current 
inspection of the kick area.

(i) Corrosion Protection

    Within 12 calendar months after the effective date of this AD, 
apply protective coating and corrosion inhibiting compound (CIC) by 
following steps 9 and 10 of the Accomplishment Instructions in 
Textron SEL-57-08R2 or Textron SEL-57-09R1, as applicable to your 
airplane model.

(j) Installation Prohibition

    As of the effective date of this AD, do not install on any 
airplane a carry-thru spar unless it has been inspected as required 
by paragraphs (g) and (h) of this AD and corrosion protection 
applied as required by paragraph (i) of this AD.

(k) Reporting Requirement

    Within 30 days after completing the inspections required by this 
AD or within 30 days after the effective date of this AD, whichever 
occurs later, report to the FAA by email ([email protected]) all 
information requested in the Carry-Thru Spar Inspection Report 
Attachment to Textron SEL-57-08R2 or Textron SEL-57-09R1, as 
applicable to your airplane model.

(l) Credit for Previous Actions

    (1) You may take credit for the visual inspection and corrosion 
removal required by paragraph (g) of this AD if you performed the 
visual inspection and corrosion removal before the effective date of 
this AD using Textron Aviation Mandatory Single Engine

[[Page 9185]]

Service Letter SEL-57-08, dated November 1, 2019 (Textron SEL-57-
08); Textron Aviation Mandatory Single Engine Service Letter SEL-57-
08, Revision 1, dated November 19, 2019 (Textron SEL-57-08R1); 
Textron Aviation Mandatory Single Service Letter SEL-57-09, dated 
November 19, 2019 (Textron SEL-57-09); Textron Aviation Mandatory 
Single Engine Service Letter SEL-57-06, dated June 24, 2019 (Textron 
SEL-57-06); Textron Aviation Mandatory Single Engine Service Letter 
SEL-57-06, Revision 1, dated November 19, 2019 (Textron SEL-57-
06R1); Textron Aviation Mandatory Single Engine Service Letter, SEL-
57-07, dated June 24, 2019 (Textron SEL-57-07); or Textron Aviation 
Mandatory Single Engine Service Letter, SEL-57-07, Revision 1, dated 
November 19, 2019 (Textron SEL-57-07R1).
    (2) You may take credit for the eddy current inspection of the 
lower cap kick area and all locations where corrosion was removed on 
the carry-thru spar lower cap and the corrosion removal as specified 
in paragraph (h) of this AD if you performed the eddy current 
inspection and corrosion removal required before the effective date 
of this AD using Textron SEL-57-08, Textron SEL-57-08R1, Textron 
SEL-57-06, Textron SEL-57-06R1, Textron SEL-57-07, Textron SEL-57-
07R1, or Textron SEL-57-09.
    (3) You may take credit for the corrosion protection required by 
paragraph (i) of this AD if you performed those actions before the 
effective date of this AD using Textron SEL-57-08, Textron SEL-57-
08R1, or Textron SEL-57-09.
    (4) To take credit for any previous action, you must have 
provided a completed Carry-Thru Spar Inspection Report, an 
attachment to Textron SEL-57-06, Textron SEL-57-06 R1, Textron SEL-
57-07, Textron SEL-57-07R1, Textron SEL-57-08, Textron SEL-57-08R1, 
or Textron SEL-57-09 to Textron Aviation Inc. before the effective 
date of this AD, or you must comply with paragraph (k) of this AD 
within 30 days after the effective date of this AD.

(m) Special Flight Permit

    (1) This AD prohibits a special flight permit if the inspection 
identifies cracking in the carry-thru spar.
    (2) Special flight permits, as described in 14 CFR 21.197 and 
21.199, may be issued for airplanes on which corrosion was 
identified to operate to a location where the requirements of this 
AD can be accomplished.
    (3) Special flight permits, as described in 14 CFR 21.197 and 
21.199, may be issued for an airplane demonstrating evidence of 
previous blending for which credit for previous actions, as defined 
in paragraph (l), cannot be granted or for an airplane demonstrating 
any damage other than corrosion or cracking, but concurrence by the 
Manager, Wichita ACO Branch, FAA is required before issuance of the 
special flight permit. Send requests for a special flight permit to 
your local Flight Standards District Office.

(n) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Wichita 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 local Flight Standards District 
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 (o) of this AD.
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the local flight standards district office/certificate holding 
district 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 a Textron Aviation, Inc. Unit Member (UM) of 
the Textron Organization Designation Authorization (ODA), that has 
been authorized by the Manager, Wichita ACO Branch, to make those 
findings. To be approved, the repair, modification deviation, or 
alteration deviation must meet the certification basis of the 
airplane, and the approval must specifically refer to this AD.

(o) Related Information

    For more information about this AD, contact Bobbie Kroetch, 
Aviation Safety Engineer, Wichita ACO Branch, FAA, 1801 Airport 
Road, Wichita, KS 67209; phone: (316) 946-4155; email: 
[email protected] or [email protected].

(p) Material Incorporated by Reference

    (1) The Director of the Federal Register approved the 
incorporation by reference 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) Textron Aviation Mandatory Single Engine Service Letter, 
SEL-57-08, Revision 2, dated August 3, 2020.
    (ii) Textron Aviation Mandatory Single Engine Service Letter, 
SEL-57-09, Revision 1, dated August 3, 2020.
    (3) For service information identified in this AD, contact 
Textron Aviation Inc., One Cessna Boulevard, Wichita, KS 67215; 
phone: (316) 517-6061; email: [email protected]; website: 
support.cessna.com.
    (4) You may view this service information at FAA, Airworthiness 
Products Section, Operational Safety Branch, 901 Locust, Kansas 
City, MO 64106. For information on the availability of this material 
at the FAA, call (817) 222-5110.
    (5) You may view this service information that is incorporated 
by reference at the National Archives and Records Administration 
(NARA). For information on the availability of this material at 
NARA, email: [email protected], or go to: www.archives.gov/federal-register/cfr/ibr-locations.html.

    Issued on February 1, 2023.
Christina Underwood,
Acting Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2023-02986 Filed 2-10-23; 8:45 am]
BILLING CODE 4910-13-P