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Federal Register / Vol. 86, No. 177 / Thursday, September 16, 2021 / Proposed Rules Identifier 2019CE047AD at the beginning of your comments. The most helpful comments reference a specific portion of the proposal, explain the reason for any recommended change, and include supporting data. The FAA
will consider all comments received by the closing date and may amend the proposal because of those comments.
Except for Confidential Business Information CBI as described in the following paragraph, and other information as described in 14 CFR
11.35, the FAA will post all comments received, without change, to https
www.regulations.gov, including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this NPRM.
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 John Marshall, Aviation Safety Engineer, Atlanta ACO
Branch, FAA, 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 780203 Reg.
Docket No. 77EA81, Amendment 39
3128 43 FR 3079, January 23, 1978
AD 780203, for all Piper Model PA
23250 airplanes. AD 780203 was prompted by cracks found on the stabilator structure during routine inspections, including cracks in the tip balance weight, abnormal trim tab horn bushing wear, and skin and nose rib cracks. The FAA issued AD 780203 to
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prevent weakening of the stabilator structure and loss of the trim tab and counter balance weight, which could result in reduced airplane control.
For all Model PA23250 airplanes, AD 780203 requires repetitively inspecting both the stabilator tip tube and the weight assemblies for cracks, with follow-on alterations or replacements as necessary, in accordance with Piper Service Bulletin SB No. 540, dated January 4, 1977
Piper SB 540. For different groups of serial-numbered airplanes, AD 7802
03 requires a one-time inspection of the stabilator tip ribs for missing rivets and missing tube and weight assembly attachment screws with alteration as necessary, replacement of the right and left stabilator tab forward inboard rib/
horn assemblies, and/or reinforcement of the mounting of the stabilator tube and weight assemblies. The repetitive inspections in AD 780203 for all serial-numbered airplanes have no terminating action and are required regardless of any corrective actions performed.
Actions Since AD 780203 Was Issued Since the FAA issued AD 780203, Piper changed the design of the stabilator structure. Airplanes beginning with serial number 277954122 were manufactured with the stabilator design change and are not subject to the unsafe condition addressed by AD 780203.
The FAA determined the applicability of AD 780203 should be revised to exclude those later-manufactured airplanes.
In addition, Piper revised SB 540, the service bulletin required by AD 7802
03 for the repetitive inspections of the stabilator tip tube and the weight assemblies. Piper SB 540B, dated February 9, 2021 Piper SB 540B, reduces the applicability of the affected serial numbers and contains separate instructions for inspecting and repairing airplanes with a modified tube and weight assembly or with a stabilizer balance weight replacement kit part number P/N 763 987.
Related Service Information Under 1
CFR Part 51
The FAA reviewed the following service documents proposed for compliance with this NPRM:
Piper SB No. 547, dated March 1, 1977, which contains instructions for inspecting the stabilator tip rib;

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Piper SB No. 569, dated August 24, 1977, which contains information for replacing the stabilator tab horn;
Piper Service Letter No. 807A, dated September 8, 1977, which contains information for installing the stabilator outboard nose rib; and Piper SB No. 540B, February 9, 2021, which contains instructions for inspecting the stabilator tip tube and weight assembly and addressing any cracks found.
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.
Other Related Service Information The FAA reviewed the following documents for information related to this NPRM:
Piper SB 540, which contains instructions for inspecting and reinforcing the stabilator tip tube and weight assembly; and Piper Aztec Service Manual, Part Number 753564, dated January 1, 2009.
Paragraphs 465 through 467 of this manual contain procedures for checking control surface balance.
FAAs Determination The FAA is issuing this NPRM after determining the unsafe condition described previously is likely to exist or develop in other products of the same type design.
Proposed AD Requirements in This NPRM
This proposed AD would retain all of the requirements of AD 780203 but would reduce the applicability and update some of the service information that would be required for compliance.
Differences Between This Proposed AD
and the Service Information Piper SB 540B specifies contacting Piper for repair instructions. This proposed AD would require contacting the FAA for an approved repair method instead.
Costs of Compliance The FAA estimates that this AD, if adopted as proposed, would affect 625
airplanes of U.S. registry.
The FAA estimates the following costs to comply with this proposed AD:

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