Discussion \n\n\n\tThe FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all Aerostar Model PA- 60-601P (Aerostar 601P), PA-60-602P (Aerostar 602P), and PA-60-700P (Aerostar 700P) airplanes. The NPRM published in the Federal Register on June 26, 2020 (85 FR 38338). The NPRM was prompted by reports of corrosion on the elevator and aileron balance tubes, which may be hidden by rubber boots. In the NPRM, the FAA proposed to require repetitively inspecting the elevator and aileron balance tubes for corrosion (pitting and flaking) and rust (discoloration) and replacing the tube. \n\tThe FAA is issuing this AD to detect corrosion on the elevator and aileron balance tubes. The unsafe condition, if not addressed, could result in failure of the aileron and elevator balance tubes, jamming of the aileron and/or elevator balance tubes, and loss of control of the airplane. \n\nComments \n\n\n\tThe FAA gave the public the opportunity to participate in developing this final rule. The FAA received comments from three commenters. The commenters were Yankee Aviation Services, Inc. and two individuals. The following presents the comments received on the NPRM and the FAA's response to each comment. \n\nRequest To Withdraw NPRM \n\n\n\tAn individual commenter requested that the NPRM be withdrawn. The commenter stated there is insufficient data supporting the unsafe condition and questioned the motive for the proposed AD, as Aerostar would benefit financially from the sale of parts needed to comply with the proposed requirements. The commenter observed that Aerostar's service information did not provide details concerning the number, source, or content of the reported events of corrosion and the degree to which the unsafe condition is present in the fleet of Aerostar airplanes. The commenter further stated that the service information and the traditional diligence of the Aerostar owner community are sufficient to address the unsafe condition. \n\tThe FAA disagrees. The FAA issues an AD after finding that an unsafe condition exists or is likely to develop in aircraft of a particular type design. For this AD, the FAA reviewed the reports received from Aerostar and the effects that failure of these tubes could have on an airplane. Aerostar initially discovered corrosion on the elevator and aileron balance tubes while conducting maintenance on an airplane. This discovery prompted Aerostar to inspect the other four airplanes in its facility, which resulted in the identification of three additional incidents of corrosion on elevator and aileron balance tubes. The FAA's analysis of this data determined an unsafe condition exists and warrants corrective action through an AD. To the extent Aerostar has issued service information on this issue, while an operator may incorporate into its maintenance program the inspections in the manufacturer's service bulletin, not all operators are required to do so. In order for these inspections to become mandatory, and to correct the unsafe condition identified in the NPRM, the FAA must issue an AD. \n\tThe FAA did not change this AD based on this comment. \n\nRequest To Remove Requirement To Replace All Tubes \n\n\n\tAll three commenters requested that the FAA remove the proposed requirement to replace the elevator and aileron balance tubes even if no corrosion and rust is found during the inspection. Two commenters noted that requiring the replacement of parts found to be airworthy does not promote safety and instead subjects owners to unnecessary expenses. Yankee Aviation Services, Inc., stated the new tubes are the same as those being replaced and do not have corrosion proofing. \n\tThe FAA disagrees. The FAA determined that the root cause of the rust and corrosion on the elevator and aileron balance tubes is likely a deficient corrosion protection specification in the initial design and manufacture of these tubes. The commenter is notcorrect that the new tubes are the same as those being replaced. The existing balance tubes are part number (P/N) 26003-003, Revision L or earlier, while the new replacement balance tubes are P/N 26003-003, Revision M or later, as specified in the service information. The Revision M and later balance tubes have been manufactured with corrosion protection (Zinc Chromate primer) that was not applied on the earlier versions of the tubes. The FAA did not change this AD based on these comments. \n\nRequest To Allow Part Repair Instead of Replacement \n\n\n\tYankee Aviation Services, Inc., requested the FAA revise the proposed AD to allow the repair of tubes with rust instead of replacement. The commenter stated that a tube with light rust and a wall thickness of 0.049 inch could be repaired by being wire brushed and painted with an epoxy paint. \n\tThe FAA disagrees. Repairing the tubes without replacement would not address the root cause of the rust and \n\n((Page 82309)) \n\ncorrosion, which the FAA determined is likely a deficient corrosion protection specification in the initial design and manufacture of these tubes. The Revision M or later balance tubes have been manufactured with corrosion protection (Zinc Chromate primer) that was not applied on the earlier versions of the tubes. The commenter's request would allow the tubes to remain installed on the airplane without this additional corrosion protection. The FAA did not change this AD based on this comment. \n\nConclusion \n\n\n\tThe FAA reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting this AD as proposed. Accordingly, the FAA is issuing this AD to address the unsafe condition on these products. \n\nRelated Service Information Under 1 CFR part 51 \n\n\n\tThe FAA reviewed Aerostar Service Bulletin SB600-138, dated August 30, 2018. The service bulletin contains procedures for repetitively inspecting the elevator and aileron balance tubes for corrosion (pitting and flaking) and rust (discoloration) and replacing the tubes at a specified time and repetitively if 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. \n\nDifferences Between This AD and the Service Information \n\n\n\tThis AD does not require completing the reply card and returning it to Aerostar as specified in Step 13 of Part II of the service information. \n\nCosts of Compliance \n\n\n\tThe FAA estimates that this AD affects 404 airplanes of U.S. registry. \n\tThe FAA estimates the following costs to comply with this AD: \n\n\n\tEstimated Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost on U.S. \n\tAction Labor cost Parts cost Cost per product operators ---------------------------------------------------------------------------------------------------------------- Inspect elevator and aileron 1 work-hour x $85 Not Applicable.... $85 per inspection $34,340 per \n\tbalance tubes. per hour = $85 cycle.. inspection cycle. \n\tper inspection \n\tcycle. Replace elevator and aileron 8 work-hours x $85 $1,187............ $1,867............ $754,268. \n\tbalance tubes. per hour = $680. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tThe FAA estimates the following costs to do any necessary replacements that are required based on the results of the repetitive inspections, assuming separate replacement intervals. The FAA has no way of determining the number of airplanes that might need these replacements: \n\n\n\tOn-Condition Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per \n\tAction Labor cost Parts cost product ---------------------------------------------------------------------------------------------------------------- Replace elevator balance tube................. 8 work-hours x $85 per hour = $594 $1,274 \n\t$680. Replace aileron balance tube.................. 8 work-hours x $85 per hour = 594 1,274 \n\t$680. ---------------------------------------------------------------------------------------------------------------- \n\nAuthority for This Rulemaking \n\n\n\tTitle 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. \n\tThe FAA is issuing this rulemaking under the authority described in Subtitle VII, Part A, SubpartIII, 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. \n\nRegulatory Findings \n\n\n\tThis 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. \n\tFor the reasons discussed above, I certify that this AD: \n\t(1) Is not a ''significant regulatory action'' under Executive Order 12866, \n\t(2) Will not affect intrastate aviation in Alaska, and \n\t(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. \n\nList of Subjects in 14 CFR Part 39 \n\n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.