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Federal Register / Vol. 86, No. 54 / Tuesday, March 23, 2021 / Proposed Rules
Confidential Business Information CBI is commercial or financial information that is both customarily and actually treated as private by its owner.
Under the Freedom of Information Act FOIA 5 U.S.C. 552, CBI is exempt from public disclosure. If your comments responsive to this NPRM
contain commercial or financial information that is customarily treated as private, that you actually treat as private, and that is relevant or responsive to this NPRM, it is important that you clearly designate the submitted comments as CBI. Please mark each page of your submission containing CBI
as PROPIN. The FAA will treat such marked submissions as confidential under the FOIA, and they will not be placed in the public docket of this NPRM. Submissions containing CBI
should be sent to Dan McCully, Aviation Safety Engineer, FAA, Atlanta ACO Branch, 1701 Columbia Avenue, College Park, GA 30337. Any commentary that the FAA receives which is not specifically designated as CBI will be placed in the public docket for this rulemaking.
Background The FAA issued AD 790103, Amendment 393383 44 FR 36, January 2, 1979, Docket No. 78EA69 AD 79
0103, for certain Piper Model PA36
285 airplanes. AD 790103 requires repetitive inspections of spar carry through assembly part number P/N
9737000, with repair as necessary, until the spar carry through assembly is replaced with P/N 7682402. AD 79
0103 was prompted by reports of cumulative damage to the wing spar carry through assembly, which resulted from fatigue testing and other field evidence of movement between the leg of the spar cap and the spar web. The FAA issued AD 790103 to prevent hazards in flight associated with damage of the wing spar carry through assembly.
The FAA also issued AD 832003, Amendment 394739 48 FR 45535, October 6, 1983, Docket No. 83CE23
AD AD 832003, for Piper Models PA36285, PA36300, and PA36
375 airplanes. AD 832003 establishes
life limits for certain wing structural components. AD 832003 was prompted by manufacturer laboratory fatigue tests of the wing structure that identified the need to establish a service life limit for the wing structural components. The FAA issued AD 83
2003 to prevent failure of the wing structural components because of fatigue damage.
Actions Since AD 790103 and AD 83
2003 Were Issued Since the FAA issued AD 790103
and AD 832003, the FAA identified inconsistencies between the two ADs and the airplanes type certificate. The FAA determined that the life limits for the spar carry through assembly, P/N
9737000 or 7682402, were inadvertently omitted from AD 8320
03 for certain airplanes. The FAA is issuing this NPRM to add the life limit for the spar carry through assembly for Models PA36285 and PA36300
airplanes, serial numbers 367660123
through 368160023, and Model PA
36375 airplanes, serial numbers 36
7802001 through 368302025. The FAA
also determined the repetitive inspections of the spar carry through assembly required by AD 790103
should apply to both Model PA36285
and Model PA36300 airplanes until the life limit replacement of the spar carry through assembly with P/N
7682402. After the initial life limit replacement of the wing spar carry through assembly required by AD 83
2003 P/N 9737000 with P/N 76824
02, the inspections required by AD 79
0103 are no longer be required. In this NPRM, the FAA proposes to supersede both of those ADs.
FAAs Determination The FAA is issuing this NPRM after determining that the unsafe condition described previously is likely to exist or develop on other products of the same type design.
Related Service Information Under 1
CFR Part 51
The FAA reviewed Piper Aircraft, Inc., Service Bulletin No. 552A, dated
August 3, 2018 Piper SB No. 552A;
Piper Aircraft PA36, Pawnee Brave Kit 764394, Right Wing Main Spar Caps Replacement, dated June 9, 2012 Piper Kit 764394; and Piper Aircraft PA36, Pawnee Brave Kit 764393, Left Wing Main Spar Caps Replacement, dated June 9, 2012 Piper Kit 764393. Piper SB No. 552A applies to Models PA36
285 and PA36300 airplanes and contains procedures for repetitively inspecting wing spar carry through assembly P/N 9737000. Piper Kit 764
394 identifies the applicable parts and specifies procedures for replacing the right wing main spar caps, which includes the attachment bolts and wing carry through spar fittings and assembly. Piper Kit 764393 identifies the applicable parts and specifies procedures for replacing the left wing main spar caps, which includes the attachment bolts and wing carry through spar fittings and assembly. 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 also reviewed Piper Aircraft Corporation Service Bulletin No. 552, dated February 3, 1978 Piper SB No.
552. Piper SB No. 552 contains the same procedures as Piper SB No. 552A, but Piper SB No. 552 only applies to Model PA36285 airplanes.
Proposed AD Requirements in This NPRM
This proposed AD would retain all of the requirements of AD 790103 and AD 832003 but would apply some of the requirements to additional serialnumbered airplanes.
Costs of Compliance The FAA estimates that this AD, if adopted as proposed, would affect 123
airplanes of U.S. registry.
The FAA estimates the following costs to comply with this proposed AD:

ESTIMATED COSTS
Cost per product
Cost on U.S.
operators
Action
Labor cost
Parts cost
Inspection of P/N 9737000 wing spar carry through assembly.
Replacement of the wing attachment upper bolt and lower bolt.
Replacement of wing carry through spar assembly.

8 work-hours $85 per hour =
$680.
10 work-hours $85 per hour =
$850.
30 work-hours $85 per hour =
$2,550.

Not applicable

$680

$83,640

$1,310 both bolts

2,160

265,680

$23,467

26,017

3,200,091

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