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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.

                           TABLE 1 TO PARAGRAPH (C)                       
    ______________________________________________________________________
    MODEL             SERIAL NUMBERS
    ______________________________________________________________________
    PA-28-151         All serial numbers

    PA-28-161         All serial numbers except 2842006

    PA-28-181         All serial numbers

    PA-28-235         All serial numbers

    PA-28R-180        All serial numbers

    PA-28R-200        All serial numbers except 28R-7235151

    PA-28R-201        All serial numbers except 2844029, 2844030, 2844081,
                      2844125, 2844136, 2844147 through 2844151,
                      28R-7737078, 28R-7737142, 28R-7837108, 28R-7837125,
                      and 28R-7837257

    PA-28R-201T       All serial numbers

    PA-28RT-201       All serial numbers

    PA-28RT-201T      All serial numbers

    PA-32-260         All serial numbers

    PA-32-300         All serial numbers

    PA-32R-300        All serial numbers

    PA-32RT-300       All serial numbers except 32R-7985004

    PA-32RT-300T      All serial numbers
    ______________________________________________________________________

(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 al-
    ready 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 calcu-
    lated 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 air-
    plane maintenance records and determine the number of 100-hour inspec-
    tions 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 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 91.409(b), need not be counted. For operators utilizing a
    progressive inspection program count the completion of each 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.

(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 cer-
     tificate  and  must be entered into the aircraft records showing com-
     pliance 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.

                        FIGURE 1 TO PARAGRAPH (H)(2)                     
    ______________________________________________________________________
    N is the number of 100 - hour inspections and T is the total hours TIS
    of the airplane.

                          [T-(N X 100)]
              (N X 100) + ------------- = Factored Service Hours
                               17
    ______________________________________________________________________

(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  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 para-
    graph (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 be-
    cause the factored service hours are less than 5,000 hours.

                        FIGURE 2 TO PARAGRAPH (H)(3)                      
    ______________________________________________________________________
    If the number of 100- hour inspections is 0 and the total hours TIS of
    the airplane is 12,100 hours, then your formula would be:

                     [12,100 - (0 X 100)]
         (0 X 100) + -------------------- = 711 Factored Service Hours
                              17
    ______________________________________________________________________

(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  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.

                        FIGURE 3 TO PARAGRAPH (H)(4)                      
    ______________________________________________________________________
    If the number of 100-hour inspections is 55 and the total hours TIS of
    the airplane is 10,600 hours, then your formula would be:

                                 [10,600 - (55 X 100)]
                    (55 X 100) + --------------------- =
                                         17


                                   [10,600 - (5,500)]
                       (5,500) + -------------------- =
                                            17


                 (5,500) + 300 = 5,800 Factored Service Hours
    ______________________________________________________________________

(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) inspec-
tions.

(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 para-
    graph (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 re-
    quired 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 in-
    spector,  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 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 refer-
    ence 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.

                         APPENDIX 1 TO AD 2020-26-16
__________________________________________________________________________
                           INSPECTION RESULTS FORM

Email completed form to:       Or mail to: Federal Aviation Administration
9-ASO-ATLCOS-Reporting@faa.gov             Atlanta ACO Branch, AIR-7A1
and                                        1701 Columbia Avenue
customer.service@piper.com                 College Park, GA 30337
                                           and
SUBJECT line: Docket No.                   Piper Certification Office
              FAA-2018-1046                2926 Piper Drive
                                           Vero Beach, FL 32960

                        Include photos if applicable

Aircraft Model No.: PA-                    Serial Number:

Aircraft Total Hours
Time-In-Service (TIS):                     Registration Number:

Factored Service Hours
Left-Hand (LH) Wing:                       Right-Hand (RH) Wing:

(If both wings are factory installed original, these numbers should be the
same)

Inspection Results

LH Wing Spar Fwd                           RH Wing Spar Fwd
Accepted __ Rejected __                    Accepted __ Rejected __

LH Wing Spar Aft                           RH Wing Spar Aft
Accepted __ Rejected __                    Accepted __ Rejected __

Inspector Comments (observed damage, condition of hole, etc)
__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

Inspector Information

Name (print): _______________________Signature: __________________________

Certificate No.: _________________________Date: __________________________

__________________________________________________________________________

Issued  on  December 30, 2020.  Gaetano A. Sciortino,  Deputy Director for
Strategic Initiatives,  Compliance & Airworthiness Division, Aircraft Cer-
tification Service.

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
PREAMBLE 

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.

-----------------------------------------------------------------------

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
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.
---------------------------------------------------------------------------

\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.
---------------------------------------------------------------------------

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\
---------------------------------------------------------------------------

\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.
---------------------------------------------------------------------------

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
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\
---------------------------------------------------------------------------

\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.
---------------------------------------------------------------------------

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
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.

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

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

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

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

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 hour = $6,800 per wing spar $5,540 $12,340 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


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

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

Sec. 39.13 [Amended]

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