[Federal Register Volume 86, Number 10 (Friday, January 15, 2021)]
[Rules and Regulations]
[Pages 3769-3780]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-00044]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2018-1046; Product Identifier 2018-CE-049-AD; Amendment 
39-21371; AD 2020-26-16]
RIN 2120-AA64


Airworthiness Directives; Piper Aircraft, Inc. 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 
certain Piper Aircraft, Inc. (Piper) Models PA-28-151, PA-28-161, PA-
28-181, PA-28-235, PA-28R-180, PA-28R-200, PA-28R-201, PA-28R-201T, PA-
28RT-201, PA-28RT-201T, PA-32-260, PA-32-300, PA-32R-300, PA-32RT-300, 
and PA-32RT-300T airplanes. This AD was prompted by a report of a wing 
separation caused by fatigue cracking in a visually inaccessible area 
of the lower main wing spar cap. This AD requires calculating the 
factored service hours for each main wing spar to determine when an 
inspection is required, inspecting the lower main wing spar bolt holes 
for cracks, and replacing any cracked main wing spar. The FAA is 
issuing this AD to address the unsafe condition on these products.

DATES: This AD is effective February 16, 2021.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of February 16, 
2021.

ADDRESSES: For service information identified in this final rule, 
contact Piper Aircraft, Inc., 2926 Piper Drive, Vero Beach, Florida 
32960; phone: (772) 567-4361; website: https://www.piper.com. You may 
view this service information at the FAA, Airworthiness Products 
Section, Operational Safety Branch, 901 Locust, Kansas City, Missouri 
64106. For information on the availability of this material at the FAA, 
call (816) 329-4148. It is also available at https://www.regulations.gov by searching for and locating Docket No. FAA-2018-
1046.

Examining the AD Docket

    You may examine the AD docket at https://www.regulations.gov by 
searching for and locating Docket No. FAA-2018-1046; or in person at 
Docket Operations between 9 a.m. and 5 p.m., Monday through Friday, 
except Federal holidays. The AD docket contains this final rule, any 
comments received, and other information. The address for Docket 
Operations is U.S. Department of Transportation, Docket Operations, M-
30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue 
SE, Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Dan McCully, Aviation Safety Engineer, 
Atlanta ACO Branch, FAA, 1701 Columbia Avenue, College Park, Georgia 
30337; phone: (404) 474-5548; fax: (404) 474-5605; email: 
william.mccully@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 by adding an AD that would apply to certain Piper Models 
PA-28-140, PA-28-150, PA-28-151, PA-28-160, PA-28-161, PA-28-180, PA-
28-181, PA-28-235, PA-28R-180, PA-28R-200, PA-28R-201, PA-28R-201T, PA-
28RT-201, PA-28RT-201T, PA-32-260, and PA-32-300 airplanes. The NPRM 
published in the Federal Register on December 21, 2018 (83 FR 65592). 
The NPRM was prompted by a fatal accident involving wing separation on 
a Piper Model PA-28R-201 airplane. An investigation revealed a fatigue 
crack in a visually inaccessible area of the lower main wing spar cap. 
The NPRM included other model airplanes with similar wing spar 
structures as the Model PA-28R-201. Based on airplane usage history, 
the FAA determined that only those airplanes with higher risk for 
fatigue cracks (airplanes with a significant history of operation in 
flight training or other high-load environments) should be subject to 
the inspection requirements proposed in the NPRM.
    Because airplanes used in training and other high-load environments 
are typically operated for hire and have inspection programs that 
require 100-hour inspections, the FAA determined the number of 100-hour 
inspections an airplane has undergone would be the best indicator of 
the airplane's usage history. Accordingly, the FAA developed a factored 
service hours formula based on the number of 100-hour inspections 
completed on the airplane.
    In the NPRM, the FAA proposed to require a review of the airplane 
maintenance records to determine the number of 100-hour inspections and 
the application of the factored service hours formula to identify when 
an airplane meets the criteria for the proposed eddy current inspection 
of the lower main wing spar bolt holes. The FAA also proposed to 
require inspecting the lower main wing spar bolt holes for cracks once 
a main wing spar exceeds the specified factored service hours and

[[Page 3770]]

replacing any main wing spar when a crack is indicated. The maintenance 
records review to determine the factored service hours proposed in the 
NPRM would only apply when an airplane has either accumulated 5,000 or 
more hours time-in-service (TIS); has had either main wing spar 
replaced with a serviceable (more than zero hours TIS) main wing spar; 
or has missing and/or incomplete maintenance records.
    The FAA issued a supplemental notice of proposed rulemaking (SNPRM) 
to amend 14 CFR part 39 by adding an AD that would apply to certain 
Piper Models PA-28-151, PA-28-181, PA-28-235, PA-28R-180, PA-28R-200, 
PA-28R-201, PA-28R-201T, PA-28RT-201, PA-28RT-201T, PA-32-260, PA-32-
300, PA-32R-300, PA-32RT-300, and PA-32RT-300T airplanes. The SNPRM 
published in the Federal Register on June 3, 2020 (85 FR 34121). The 
SNPRM was prompted by comments received on the NPRM and further 
analysis by the FAA. The FAA determined that some additional airplane 
models are likely affected by the unsafe condition and should be 
included in the applicability, while other models that are not affected 
should be removed from the applicability. Consequently, in the SNPRM, 
the FAA proposed to revise the applicability and the estimated cost 
associated with the proposed AD actions. The SNPRM also clarified the 
language in the applicability and some of the proposed actions. In 
addition, the SNPRM no longer allowed replacement of the wing spar with 
a used part. The FAA determined replacement of the wing spar with a 
part of unknown operational history would not ensure an acceptable 
level of safety. After the NPRM was published, Piper issued a service 
bulletin that contains procedures for the eddy current inspection. The 
SNPRM proposed to require using the eddy current inspection contained 
in that service bulletin instead of the inspection procedure in the 
appendix to the NPRM.
    The FAA developed a flow chart that may assist operators in 
complying with this AD. The flow chart may be found at https://www.regulations.gov by searching for and locating Docket No. FAA-2018-
1046.
    The FAA is issuing this AD to address the unsafe condition on these 
products.

Discussion of Final AD

Comments

    The FAA received comments on the SNPRM from 42 commenters. The 
majority of the commenters were individuals. The remaining commenters 
included Piper, governmental agencies such as the National 
Transportation Safety Board (NTSB) and the Civil Aviation Safety 
Authority of Australia (CASA), and organizations such as the Aircraft 
Owners and Pilots Association (AOPA), the General Aviation and 
Manufacturer's Association (GAMA), the Experimental Aircraft 
Association (EAA), and the Piper Flying Association. The following 
presents the comments received on the SNPRM and the FAA's response to 
each comment.

A. Supportive Comments

    The NTSB and two individual commenters supported the AD without any 
recommended changes. Three other individual commenters supported the AD 
but requested changes discussed below.

B. Requests for Additional Information

    CASA requested information on whether a bolt hole eddy current 
inspection would have detected the crack in the 1993 accident airplane.
    The FAA agrees to provide the requested information. Because it was 
located slightly beyond the detectable range of a bolt hole eddy 
current inspection, the crack in the 1993 accident airplane would not 
have been detected by an eddy current inspection of the bolt holes. 
Although the airplane had previously undergone dye penetrant inspection 
of the bolt holes, the crack would not have been detectable under that 
method either due to its location beyond the bolt hole perimeter and 
beneath the web doubler.\1\ The 1993 accident disclosed evidence of a 
fatigue crack initiation in a wing spar similar to that of the 2018 
accident aircraft, N106ER (the accident that prompted this AD). In 
addition to having high hours TIS, the fatigue crack was very near the 
inspection location addressed by this AD. As such, the FAA included the 
1993 accident in the risk analysis process for this AD.
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    \1\ The supporting materials for NTSB accident NYC93FA140 are 
available in the NTSB Docket at https://dms.ntsb.gov/pubdms/search/hitlist.cfm?docketID=4323&CFID=1643539&CFTOKEN=74133c21c3cf3d72-C9941D08-5056-942C-92883A7C17DB9FF3.
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    CASA and an individual commenter requested information comparing 
the failures in the 1987 and 1993 accidents with the failure of N106ER 
(the accident that prompted this AD). CASA specifically asked whether 
these wing spars failed at the same outer bolt hole location.
    The FAA agrees to provide additional information. Both airplanes in 
question (N8191V, the 1987 accident; and N2093A, the 1993 accident) 
experienced wing separations at the outboard bolt holes of the lower 
spar cap. The NTSB Metallurgist's Factual Report in the 1987 accident, 
Materials Laboratory Report No. 87-89, dated August 17, 1987, found 
that fatigue had initiated at two locations on the lower surface of the 
left wing spar cap near the forward most outboard, spar to carry 
through, bolt hole. The report further found the fatigue had propagated 
completely through the forward flange and partially into the aft flange 
and spar web.\2\ The Metallurgist's Factual Report in the 1993 
accident, Report No. 93-34, dated December 15, 1993, found that the 
lower cap was fractured through the most outboard pair of bolts 
connecting the spar and carry-through.\3\ The FAA notes that the NTSB 
Final Report for the 1993 accident states the investigation could not 
determine whether an uncracked wing would have failed.\4\
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    \2\ Report No. 87-89 is available in the NTSB Docket for NTSB 
accident FTW87FA088 at https://dms.ntsb.gov/pubdms/search/document.cfm?docID=475398&docketID=62694&mkey=96975.
    \3\ Report No. 93-34 is available in the NTSB Docket for NTSB 
accident NYC93FA140 at https://dms.ntsb.gov/pubdms/search/document.cfm?docID=487590&docketID=4323&mkey=38586.
    \4\ The NTSB Aviation Accident Final Report for NTSB accident 
NYC93FA140 is available on the NTSB's website at https://app.ntsb.gov/pdfgenerator/ReportGeneratorFile.ashx?EventID=20001211X13212&AKey=1&RType=Final&IType=FA.
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    CASA and an individual commenter requested information on the 
inspection method used to detect cracks on aircraft N104ER. CASA asked 
whether the inspection method described in Piper Service Bulletin No. 
1345, dated March 27, 2020 (Piper SB No. 1345), was used. The 
individual commenter asked whether bolt hole eddy current is the most 
suitable method if it was used on N104ER and did not reveal the cracks 
that caused the wing failure.
    The FAA agrees to provide the requested information. Aircraft 
N104ER was used in the investigation of the 2018 accident due to the 
similarities in structure and operational use to the accident aircraft. 
The initial high frequency eddy current inspection of N104ER was 
conducted by a local FAA-approved repair station contracted by the 
owner. The FAA could not determine why the inspection conducted by the 
FAA-approved repair station did not detect cracks because this 
inspection did not involve the investigative team. Also, the inspection 
occurred prior to the development of the inspection procedures required 
by this AD. The investigative team conducted a second high frequency 
eddy current inspection, in the development of the

[[Page 3771]]

inspection procedures required by the AD, with the wings removed, which 
detected a crack. The team conducted an additional high frequency eddy 
current inspection after reinstalling the wings to validate the 
inspection process, which confirmed the presence of a crack.\5\
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    \5\ The supporting materials for NTSB accident ERA18FA120 are 
available in the NTSB Docket at https://dms.ntsb.gov/pubdms/search/hitlist.cfm?docketID=62694&CFID=95094&CFTOKEN=b616b3892cb482f1-5B544A63-5056-942C-92C71C2E6BFF1D97.
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    Another commenter requested information on the methodology used by 
the FAA for identifying specific wing loads, the applied stress 
locations, and their influence on fatigue life, and the rationale for 
selecting those aircraft within 95 percent of the baseline load case 
for the applicability.
    The FAA agrees to provide the requested information. The 
methodology used by the FAA for identifying specific wing loads for 
gust, maneuvering, and landing loads comes from 14 CFR part 23 (Amdt 
63) Subpart C-Structure and Advisory Circular 23-13A Fatigue, Fail-
Safe, and Damage Tolerance Evaluation of Metallic Structure for Normal, 
Utility, Acrobatic, and Commuter Category Airplanes.
    A subsequent analysis calculated damage factors using variables for 
each of the various PA-28/32 models. The variables include maximum 
design weight (Wmax), maximum design cruising speed 
(Vcmax), spar cross section properties, and spanwise center 
of pressure location for each loading category mentioned above. The 
results for each model/load category are divided by the PA-28R-201 
(accident aircraft model) results. Any model with a damage factor ratio 
greater than 0.94 is included in the effectivity of this AD.
    The 0.94 factor cutoff was arrived at by observing a natural break 
in the resulting damage factor numbers and the Palmgren-Miner linear 
damage hypothesis or Miner's Rule. This theory shows that a linear 
decrease in stress (damage factor in this case) results in an 
exponential increase in fatigue life. The FAA believes this level of 
risk is appropriate for the purpose of this one-time inspection. The 
applied stress location is at the lower spar cap attachment to the 
fuselage carry through channel, outboard row of fasteners. This is the 
location of the fatigue failure on the accident airplane.

C. Comments Regarding the FAA's Justification of the Unsafe Condition

    Piper and GAMA requested the AD be withdrawn because the completed 
NTSB investigation invalidates the FAA's basis for issuing an AD. These 
commenters asserted that, based on the NTSB's findings, the operator's 
failure to follow existing maintenance requirements was responsible for 
the accident involving N106ER.
    The FAA disagrees that the NTSB's investigation invalidates the 
FAA's basis for issuing this AD. The spar surface is not visually 
accessible during routine inspections required by existing maintenance 
requirements, because the lower spar cap is obscured by the 
installation of the web doubler on the upper surface and the wing skin 
on the lower surface. Therefore, a well-developed crack may only be 
visually detected after the spar crack progresses into the doubler. The 
claim that an operator may fail to detect a crack that had progressed 
to an extent that caused cracking in the overlying web doubler only 
serves to reinforce the need for detecting fatigue cracks in the spar 
before they reach a critical nature.

D. Comments Regarding Applicability

    Piper, AOPA, EAA, and several individual commenters requested the 
FAA revise the applicability of the AD because it is still too broad 
and includes models not representative of the accident airplane.
    EAA requested the FAA ensure that only the appropriate aircraft, in 
general, are subject to the AD. Piper and AOPA asserted that the AD 
should not include Models PA-28-151, PA-28-181, PA-32R-300, and PA-
32RT-300T airplanes. In support, Piper stated that the PA-28-151, PA-
28-181, and PA-32R-300 models have ``stress per g'' measurements that 
do not meet the 95 percent threshold established by the FAA for 
comparison to the accident airplane. CASA and eight individual 
commenters questioned why the proposed AD applies to the Model PA-28-
151 when that model is structurally similar to the Model PA-28-161, 
which the FAA proposed to remove from the applicability in the SNPRM. 
Two individual commenters requested the AD apply to the Model PA-28-
161, because of the longer wing structure. Piper and three individual 
commenters stated the PA-32R-300 and certain PA-32-300 models do not 
share the same wing construction and installation details as the 
accident airplane model.
    The FAA disagrees with removing Models PA-28-151, PA-28-181, and 
PA-32R-300 from the applicability of the AD. The FAA used the following 
load cases, provided by Piper, for comparison to the accident airplane: 
Gust damage factor, maneuver damage factor, and landing damage factor. 
The included models each had one or more load cases that exceed 94 
percent of the baseline Model PA-28R-201. Several models had individual 
load cases exceeding 100 percent of the baseline value.
    The FAA partially agrees with the comments regarding the similarity 
between the Model PA-28-151 and the Model PA-28-161. In determining 
pertinent load cases, the FAA used factors such as maximum gross 
takeoff weight and maximum cruise speed in combination with structural 
considerations. In the SNPRM, the FAA proposed to remove Model PA-28-
161 from the applicability based on initial load calculations based on 
a maximum gross takeoff weight of 2,240 lbs. Additional analysis 
indicated that the maximum gross takeoff weight is not uniform among 
all Model PA-28-161 variants, and that some variants are certificated 
to a maximum gross takeoff weight that brings the gust damage factor 
load case to above 94 percent of the baseline. Accordingly, this AD 
applies to the Model PA-28-161.
    The FAA disagrees with removing the Model PA-32R-300 and certain 
Model PA-32-300 airplanes from the applicability based on wing 
construction.
    Although the FAA acknowledges the differing wing structures among 
some models, that structure was taken into consideration during loads 
analysis in terms of inertia calculations for the each cross section.

E. Comments Regarding the Compliance Time

    An individual commenter expressed concern that the FAA's factored 
service hours did not align with the compliance time in Piper SB No. 
1345. The commenter stated that Piper's compliance time of 5,000 hours 
TIS is simpler and a more conservative approach to safety.
    The FAA partially agrees. While using hours TIS is a simpler 
approach, it would create the possibility of requiring an unnecessary 
inspection long before any fatigue crack might be expected to form. The 
FAA established 5,000 factored service hours as a method of delaying or 
eliminating inspection requirements for many personal use, lower risk 
airplanes. This AD will require an inspection within 100 hours TIS 
after reaching 5,000 factored service hours.
    Another commenter requested the FAA determine the compliance time 
based on an estimate of the number of airplanes that will need to be 
inspected and the number of qualified eddy current inspectors, to allow 
sufficient time for all airplanes in the fleet to be

[[Page 3772]]

inspected. The commenter stated it is unacceptable for airplanes to be 
grounded for a significant amount of time because of an insufficient 
number of eddy current inspectors or equipment.
    The FAA disagrees that a change to the compliance time is 
necessary. The FAA anticipates that less than 50 percent of applicable 
airplanes will have accumulated the 5,000 TIS necessary for the logbook 
review. The FAA also anticipates that the majority of those airplanes 
will not need an inspection after the logbook review. Calculating the 
number of qualified and available eddy current inspectors would be too 
speculative, as it is largely based on current demand.
    One commenter requested that the FAA convert the AD into an 
emergency AD so that data from the inspections can be collected as soon 
as possible.
    Considering the number of known failures, the severity of the 
outcome, and number of cracks detected during the investigation, the 
FAA determined that an emergency AD was not necessary. The FAA did not 
change this AD based on these comments.

F. Comments Regarding the Requirements Proposed in the SNPRM Request To 
Allow Replacement of the Spar With a Used Spar

    The Piper Flying Association and four individual commenters 
requested the FAA change the proposed requirement to install a new 
(zero hours TIS) spar if cracks were detected. These commenters stated 
that any spar that has passed the eddy current inspection is an 
airworthy spar and should be allowed as a replacement spar. Two of the 
commenters noted that the unavailability of new spars would effectively 
ground aircraft that fail the eddy current inspection.
    The FAA agrees and has revised this AD to allow the installation of 
a used (more than zero hours TIS) wing spar that has passed the eddy 
current inspection.
    An individual commenter requested the FAA compel Piper to restore 
availability of replacement parts.
    The FAA disagrees. As a federal agency, the FAA is responsible for 
all directives, policies, and mandates issued under its authority. The 
FAA does not have the authority to require a manufacturer to produce 
new parts.
Requests for Information About the Service Bulletin
    An individual commenter asked how operators can record compliance 
with the AD when the required service bulletin does not apply to all of 
the models in the AD. Another individual commenter asked why the AD 
only incorporates part of the instructions in Piper SB No. 1345.
    The FAA's regulations specify that when there is a conflict between 
an AD and a service document incorporated by reference in the AD, 
operators must follow the requirements of the AD. See 14 CFR 39.27. 
Since this AD differs from Piper SB No. 1345, as described in the 
Differences Between this AD and the Service Information section, the AD 
only requires the inspection method portion of Piper SB No. 1345.
Requests for Different Inspection Methods
    An individual commenter suggested guided wave technology as a 
better, less intrusive, and less expensive inspection method. Another 
individual commenter suggested using dye penetrant inspection without 
bolt removal as a less aggressive method for early detection, even if 
it meant more frequent inspections.
    The FAA disagrees. The FAA, Piper, and the NTSB considered several 
inspection options. Guided wave is not a preferred method for this AD 
due to accessibility issues and the need to detect longitudinal, as 
opposed to circumferential, cracks. To be detectable using a dye 
penetrant or fluorescent penetrant method, a crack that initiated at a 
wing spar attach bolt hole would have had to propagate through the web 
doubler and beyond the perimeter of the washer(s). A crack of that size 
would have already dangerously compromised the strength of the spar 
cap.
    The FAA did not change this AD based on these comments.
Requests for Different Repair Options
    An individual commenter observed that if one wing indicates fatigue 
cracks, then replacing both wings may be warranted, since the opposite 
wing would have experienced the same usage history.
    The FAA partially agrees. Fatigue cracking in one wing would 
warrant an increased level of concern for the opposite wing. However, 
the FAA determined that replacement of both wings is not required when 
only one wing has failed the inspection. Certain factors that can 
accelerate the initiation of a fatigue crack on one wing may not be 
present on the opposite wing (for example, prior damage from operations 
or maintenance).
    Another individual commenter requested the FAA consider a cold 
working process (split sleeve cold expansion) on the bolt holes to 
minimize future fatigue cracking.
    The FAA partially agrees. Piper provided the FAA with cold working 
data in support of a proposed repair and fatigue mitigation process for 
the wing spars. Cold working has been considered and may be 
investigated further should the inspection reports received as a result 
of this AD indicate that such action is required.
    One individual commenter suggested using different washers, 
adjusting the bolt torque to the lowest value of the acceptable range, 
and installing a doubler plate to alleviate stress concentrations.
    The FAA disagrees. Load transfer into the spar cap does not rely on 
a washer to help evenly transfer the load. A larger washer would not 
lower the stress concentration as the critical geometry is the fastener 
diameter and the edge distance associated with the diameter, not the 
washer size. Staying within the torque values for the bolt will not 
alleviate the loading in the bolt enough to decrease the stress 
concentration and could lead to further issues such as the bolt being 
under torqued, which would worsen the fatigue life. A doubler repair 
has been considered and may be investigated further should the 
inspection reports received as a result of this AD indicate that such 
action is required.
    An additional individual commenter asked if changing the outer 
holes to the next smaller size would result in a more favorable stress 
distribution.
    The FAA disagrees. While a smaller hole may decrease the load in 
the fastener, the gain is offset by the increase in stress 
concentration.
    The FAA has not changed the AD based on these comments.
Request for Safe Life
    An individual commenter suggested establishing a life limit as a 
solution based on a comparison of any safe life analysis conducted by 
Piper with the known fatigue failures.
    The FAA partially agrees. Fatigue safe life has been considered and 
may be pursued as an option should the inspection reports received as a 
result of this AD indicate that further action is required. Because 
this AD is interim in nature and intended to gather fleet condition 
data based on these comparisons, this AD does not contain repetitive or 
terminating actions.
    The FAA did not make any changes to this AD based on this comment.
Request To Revise the Reporting Information
    Piper requested the FAA revise the inspection results form to 
include Piper's mailing address.

[[Page 3773]]

    The FAA agrees and has added Piper's mailing address to the 
inspection results form.

G. Comments Previously Addressed in the SNPRM

    AOPA, EAA, and several individuals submitted comments that were 
substantially the same as comments the FAA received on the NPRM. These 
comments pertain to issues such as the FAA's decision to issue the AD 
as interim action, whether the FAA should issue a special airworthiness 
information bulletin or airworthiness concern sheet instead of an AD, 
how the FAA determined the AD applicability, whether the FAA should 
issue this AD considering the cost and risk associated with the removal 
and reinstallation of the airplane wings/bolts, alternatives for 
instances where maintenance records were missing or incomplete, how to 
count 100-hour inspections, the FAA's hourly labor rate, the estimated 
number of hours for the eddy current inspection, and indirect costs. 
The FAA previously addressed each of these comments in the SNPRM.

H. Out of Scope Comments

    The FAA also received and reviewed a few comments that stated the 
commenter's viewpoint without a suggestion specific to the AD or 
otherwise did not make a request the FAA can act on. These comments are 
outside the scope of this AD.

Other Changes to the Final AD

    The FAA removed two serial-numbered airplanes from the 
applicability that were included in the SNPRM because those airplanes 
were previously inspected using the current procedures and witnessed by 
the FAA. The FAA determined those airplanes are not subject to the 
unsafe condition addressed by this AD. The FAA also added language to 
clarify the procedures for when a wing is not installed on the airplane 
and clarified some of the language in the examples and figures.

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 minor editorial changes and the 
changes described previously, this AD is adopted as proposed in the 
SNPRM. None of the changes will increase the economic burden on any 
operator.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed Piper Service Bulletin No. 1345, dated March 27, 
2020 (Piper SB No. 1345). This service bulletin specifies procedures 
for doing an eddy current inspection and instructions to report the 
results of the inspection to Piper and to replace the wing, wing spar, 
or spar section as necessary. 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 Piper Service Bulletin No. 886, dated June 8, 
1988; and Piper Service Bulletin SB 978A, dated August 6, 1999. These 
service bulletins contain procedures for determining initial and 
repetitive inspection times based on the aircraft's usage and visually 
inspecting the wing lower spar caps and the upper wing skin adjacent to 
the fuselage and forward of each main spar for cracks. The FAA also 
reviewed Piper Service Letter No. 997, dated May 14, 1987, which 
contains procedures for replacing airplane wings.

Differences Between This AD and the Service Information

    Piper SB No. 1345 specifies doing the eddy current inspection upon 
reaching 5,000 hours TIS; however, this AD requires using the factored 
service hours to identify the airplanes at the highest risk of 
developing fatigue cracks. Piper SB No. 1345 also specifies using its 
feedback form to report the eddy current inspection results, but this 
AD requires the use of a different form attached as appendix 1.

Interim Action

    The FAA considers this AD to be an interim action. The inspection 
reports will provide the FAA additional data for determining the number 
of cracks present in the fleet. After analyzing the data, the FAA may 
take further rulemaking action.

Costs of Compliance

    The FAA estimates that this AD affects 5,440 airplanes of U.S. 
registry. There are 10,881 airplanes of U.S. registry with a model and 
serial number shown in table 1 to paragraph (c) of this AD. Based on a 
sample survey, the FAA estimates that 50 percent of those U.S.-
registered airplanes will have reached the qualifying 5,000 hours TIS 
necessary to do the required logbook review.
    The FAA estimates the following costs to comply with this AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                    Cost per       Cost on U.S.
              Action                     Labor cost            Parts cost           product         operators
----------------------------------------------------------------------------------------------------------------
Review airplane maintenance         3 work-hours x $85    Not applicable......            $255       $1,387,200
 records and calculate factored      per hour = $255.
 service hours.
----------------------------------------------------------------------------------------------------------------

    The FAA estimates the following costs to do the eddy current 
inspection. Because some airplanes are only used non-commercially and 
will not accumulate the specified factored service hours in the life of 
the airplane, the FAA has no way of determining the number of airplanes 
that might need this inspection:

                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                   Action                                 Labor cost                Parts cost        product
----------------------------------------------------------------------------------------------------------------
Gain access to the left-hand (LH) and right- 2 work-hours x $85 per hour = $170.             $20             190
 hand (RH) inspection areas.
Do eddy current inspections of the LH and    1 work-hour contracted service x                N/A             600
 RH lower main wing spar.                     $600 = $600.
Restore aircraft...........................  2 work-hours x $85 per hour = $170.             N/A             170

[[Page 3774]]

 
Report inspection results to the FAA and     1 work-hour x $85 per hour = $85...             N/A              85
 Piper Aircraft, Inc.
----------------------------------------------------------------------------------------------------------------

    The FAA estimates the following costs to do any necessary 
replacements that would be required based on the results of the 
inspection. The agency has no way of determining the number of aircraft 
that might need this replacement:

                                         On-Condition Replacement Costs
----------------------------------------------------------------------------------------------------------------
             Action                      Labor cost            Parts cost              Cost per product
----------------------------------------------------------------------------------------------------------------
Replace main wing spar..........  80 work-hours x $85 per           $5,540   $12,340 per wing spar.
                                   hour = $6,800 per wing
                                   spar.
----------------------------------------------------------------------------------------------------------------

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,
    (2) Will not affect intrastate aviation in Alaska to the extent 
that it justifies making a regulatory distinction, 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:

2020-26-16 Piper Aircraft, Inc.: Amendment 39-21371; Docket No. FAA-
2018-1046; Product Identifier 2018-CE-049-AD.

(a) Effective Date

    This airworthiness directive (AD) is effective February 16, 
2021.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to Piper Aircraft, Inc. (Piper) airplanes, 
certificated in any category, with a model and serial number shown 
in table 1 to paragraph (c) of this AD, and that meet at least one 
of the criteria in paragraphs (c)(1), (2), or (3) of this AD.
    Note 1 to the introductory text of paragraph (c): An owner/
operator with at least a private pilot certificate may do the 
aircraft maintenance records review to determine the applicability 
as specified in paragraph (c) of this AD.
    (1) Has accumulated 5,000 or more hours time-in-service (TIS); 
or
    (2) Has had either main wing spar replaced with a serviceable 
(more than zero hours TIS) main wing spar; or
    (3) Has missing and/or incomplete maintenance records.
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(d) Subject

    Joint Aircraft System Component (JASC) Code 5711, Wing Spar.

(e) Unsafe Condition

    This AD was prompted by a report of a wing separation caused by 
fatigue cracking in a visually inaccessible area of the main wing 
lower spar cap. The FAA is issuing this AD to detect and correct 
fatigue cracks in the lower main wing spar cap bolt holes. The 
unsafe condition, if not addressed, could result in the wing 
separating from the fuselage in flight.

(f) Compliance

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

(g) Definitions

    (1) ``TIS'' has the same meaning as the definition of ``time in 
service'' in 14 CFR
    1.1.
    (2) For purposes of this AD, ``factored service hours'' refers 
to the calculated quantity of hours using the formula in paragraph 
(h)(2) of this AD, which accounts for the usage history of the 
airplane.

(h) Review Airplane Maintenance Records and Calculate Factored Service 
Hours for Each Main Wing Spar

    (1) Within 30 days after the effective date of this AD, review 
the airplane maintenance records and determine the number of 100-
hour inspections completed on the airplane since new and any record 
of wing spar replacement(s).
    (i) For purposes of this review, count any inspection conducted 
to comply with the 100-hour requirement of 14 CFR 91.409(b) 
pertaining to carrying persons for hire, such as in-flight training 
environments, even if the inspection was entered in the maintenance 
records as an ``annual'' inspection or as an ``annual/100-hour'' 
inspection. If the purpose of an inspection was to comply with Sec.  
91.409(b), then it must be counted. To determine the purpose of an 
inspection, note the repeating intervals between inspections, i.e., 
less than 10 months between, and typically 90-110 flight hours. An 
inspection entered as a ``100-hour'' inspection but done solely for 
the purpose of meeting the requirement to complete an annual 
inspection, or those otherwise not required by Sec.  91.409(b), need 
not be counted. For operators utilizing a progressive inspection 
program, count the completion of each Sec.  91.409(b) 100-hour 
interval as one inspection.
    (ii) If a main wing spar has been replaced with a new (zero 
hours TIS) main wing spar, count the number of 100-hour inspections 
from the time of installation of the new main wing spar.

[[Page 3776]]

    (iii) If a main wing spar has been replaced with a serviceable 
main wing spar (more than zero hours TIS) or the airplane 
maintenance records are missing or incomplete, the wing history 
cannot be determined. Perform the eddy current inspection as 
specified in paragraph (i) of this AD.
    (iv) The actions required by paragraph (h)(1) of this AD may be 
performed by the owner/operator (pilot) holding at least a private 
pilot certificate and must be entered into the aircraft records 
showing compliance with this AD in accordance with 14 CFR 43.9(a)(1) 
through (4), and 14 CFR 91.417(a)(2)(v). The record must be 
maintained as required by 14 CFR 91.417, 121.380, or 135.439.
    (2) Before further flight after completing the action in 
paragraph (h)(1) of this AD, calculate the factored service hours 
for each main wing spar using the formula in figure 1 to paragraph 
(h)(2) of this AD. Thereafter, after each annual inspection and 100-
hour inspection, recalculate/update the factored service hours for 
each main wing spar until the main wing spar has accumulated 5,000 
or more factored service hours.
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[GRAPHIC] [TIFF OMITTED] TR15JA21.015

    (3) An example of determining factored service hours for an 
airplane with no 100-hour inspections is as follows: The airplane 
maintenance records show that the airplane has a total of 12,100 
hours TIS, and only annual inspections have been done. None of the 
annual inspections were done for purposes of compliance with Sec.  
91.409(b). Both main wing spars are original factory installed. In 
this case, N = 0 and T = 12,100. Use those values in the formula as 
shown in figure 2 to paragraph (h)(3) of this AD. In the example in 
figure 2 to paragraph (h)(3) of this AD), the eddy current 
inspection would not be required because the factored service hours 
are less than 5,000 hours.
[GRAPHIC] [TIFF OMITTED] TR15JA21.016

BILLING CODE 4910-13-C
    (4) An example of determining factored service hours for an 
airplane with both 100-hour and annual inspections is as follows: 
The airplane was originally flown for personal use, then for 
training for a period of time, then returned to personal use. The 
airplane maintenance records show that the airplane has a total of 
10,600 hours TIS, and fifty-five 100-hour inspections for purposes 
of compliance with Sec.  91.409(b) have been done. Both main wing 
spars are original factory installed. In this case, N = 55 and T = 
10,600. Use those values in the formula shown in figure 3 to 
paragraph (h)(4) of this AD. First, calculate commercial use time by 
multiplying (N x 100). Next, subtract that time from the total time, 
and divide that quantity by 17. Add the two quantities to determine 
total factored service hours. In the example in figure 3 to 
paragraph (h)(4) of this AD), the eddy current inspection would be 
required because the factored service hours are more than 5,000 
hours.

[[Page 3777]]

[GRAPHIC] [TIFF OMITTED] TR15JA21.017

(i) Eddy Current Inspect

    Within the compliance time specified in either paragraph (i)(1) 
or (2) of this AD, as applicable, eddy current inspect the inner 
surface of the two lower outboard bolt holes on the lower main wing 
spar cap for cracks. If the wing is installed, use steps 1 through 3 
or, if the wing is not installed, use step 3 in the Instructions of 
Piper Aircraft, Inc. Service Bulletin No. 1345, dated March 27, 2020 
(Piper SB No. 1345). Although Piper SB No. 1345 specifies NAS 410 
Level II or Level III certification to perform the inspection, this 
AD allows Level II or Level III qualification standards for 
inspection personnel using any inspector criteria approved by the 
FAA.
    Note 2 to the introductory text of paragraph (i): Advisory 
Circular 65-31B contains FAA-approved Level II and Level III 
qualification standards criteria for inspection personnel doing 
nondestructive test (NDT) inspections.
    (1) Within 100 hours TIS after complying with paragraph (h) of 
this AD or within 100 hours TIS after a main wing spar accumulates 
5,000 factored service hours, whichever occurs later; or
    (2) For airplanes with an unknown number of factored service 
hours on a main wing spar, within the next 100 hours TIS after the 
effective date of this AD or within 60 days after the effective date 
of this AD, whichever occurs later.

(j) Replace the Main Wing Spar

    If a crack is found during an inspection required by paragraph 
(i) of this AD, before further flight, replace the main wing spar 
with a new (zero hours TIS) main wing spar or with a serviceable 
(more than zero hours TIS) main wing spar that has passed the eddy 
current inspection required by paragraph (i) of this AD.

(k) Install New Bolts

    Before further flight after completing the actions required by 
paragraph (i) or (j) of this AD, install new bolts by following step 
6 of Piper Aircraft, Inc. Service Bulletin No. 1345, dated March 27, 
2020.

(l) Report Inspection Results

    Within 30 days after completing an inspection required by 
paragraph (i) of this AD, using Appendix 1, ``Inspection Results 
Form,'' of this AD, report the inspection results to the FAA at the 
Atlanta ACO Branch and to Piper Aircraft. Submit the report to the 
FAA and Piper using the contact information found on the form in 
appendix 1 of this AD.

(m) Special Flight Permit

    A special flight permit may only be issued to operate the 
airplane to a location where the inspection requirement of paragraph 
(i) of this AD can be performed. This AD prohibits a special flight 
permit if the inspection reveals a crack in a main wing spar.

(n) Paperwork Reduction Act Burden Statement

    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 be approximately 1 hour per response, including the 
time for reviewing instructions, searching existing data sources, 
gathering and maintaining the data needed, 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.

(o) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Atlanta 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 (p) 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.

(p) Related Information

    For more information about this AD, contact Dan McCully, 
Aviation Safety Engineer, Atlanta ACO Branch, FAA, 1701 Columbia 
Avenue, College Park, Georgia 30337; phone: (404) 474-5548; fax: 
(404) 474-5605; email: william.mccully@faa.gov.

(q) 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) Piper Service Bulletin No. 1345, dated March 27, 2020.
    (ii) [Reserved]
    (3) For Piper Aircraft, Inc. service information identified in 
this AD, contact Piper Aircraft, Inc., 2926 Piper Drive, Vero

[[Page 3778]]

Beach, Florida 32960; phone: (772) 567-4361; website: https://www.piper.com.
    (4) You may view this service information at FAA, Airworthiness 
Products Section, Operational Safety Branch, 901 Locust, Kansas 
City, Missouri 64106. For information on the availability of this 
material at the FAA, call (816) 329-4148.
    (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: fedreg.legal@nara.gov, or go to: https://www.archives.gov/federal-register/cfr/ibr-locations.html.
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[[Page 3780]]


    Issued on December 30, 2020.
Gaetano A. Sciortino,
Deputy Director for Strategic Initiatives, Compliance & Airworthiness 
Division, Aircraft Certification Service.
[FR Doc. 2021-00044 Filed 1-14-21; 8:45 am]
BILLING CODE 4910-13-C


