Discussion
On August 19, 2010, we issued Emergency AD (EAD) 2010-18-51. That EAD was prompted by two reports of cracks detected in the lower hub near the flex beam bolt hole location during maintenance. That EAD required, within 4 hours time-in-service (TIS), visually inspecting the lower hub for a crack and, if you find a crack, before further flight, replacing the lower hub with an airworthy lower hub and, within 10 days, reporting a cracked lower hub to the LAACO. We superseded EAD 2010-18-51 with EAD 2010-18-52, issued August 23, 2010, upon discovering a typographical error in the ``Applicability'' section of the EAD in the lower hub part number (P/N). EAD 2010-18-52 contained the same requirements as EAD 2010-18-51 but corrected the P/N for the lower hub.
Actions Since That AD Was Issued
Since we issued the AD, 5 additional lower hubs were found cracked. We determined that one manufacturer of lower hubs with serial numbers (S/Ns) beginning with 5009 (e.g., 5009-XXXX) had incorrectly inserted flanged bushings into the lower hub bore. This condition resulted in local corrosion leading to fatigue cracking. Examination of lower hubs from the other manufacturer shows correct bushing installation.
Relevant Service Information
We reviewed MDHI Service Bulletin SB900-117, dated January 14, 2011 (SB). The SB specifies an initial 100-hour and recurring 300-hour visual and eddy current inspections of the lower hub for a crack and, if there is a crack, replacing the lower hub with an airworthy lower hub. The inspections would be done at the stated intervals or at the next annual inspection, whichever occurs first. The SB also specifies replacing an affected lower hub within 3 years after the date of the SB.
FAA's Determination
We are issuing this AD because we evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other helicopters of this same type design.
AD Requirements
This AD requires a visual inspection, and if necessary, an eddy current inspection of the lower hub for a crack. If there is a crack, the AD requires replacing the lower hub with an airworthy lower hub. This AD requires accomplishing these actions by following specified portions of the service information described previously, except as discussed under ``Differences Between the AD and the Service Information.''
Change to Existing AD
This superseding AD changes the compliance time for the visual inspection and adds an eddy current inspection of the lower hub for a crack. This AD also removes the reporting requirement to the LAACO and the requirement for an OMB control number. This AD also reduces the applicability to only those helicopters with certain serial-numbered lower hubs installed.
Differences Between the AD and the Service Information
This AD does not require contacting the manufacturer or returning the lower hub assembly with a certain report. This AD also does not require the 300-hour inspection or replacing the lower hub within 3 years from the date of the SB because these actions do not fit our criteria for a Final rule, request for comments.
FAA's Justification and Determination of the Effective Date
An unsafe condition exists that requires the immediate adoption of this AD. The FAA has found that the risk to the flying public justifies waiving notice and comment prior to adoption of this rule because the previously described unsafe condition can adversely affect the structural integrity and controllability of the helicopter. The inspection is required within 100 hours TIS or during the annual inspection, whichever occurs first, unless done within the last 200 hours TIS. Since the affected helicopters could reach 100 hours TIS within 1 month, we find that notice and opportunity for prior public comment are impracticable and that good cause exists for making this amendment effective in less than 30 days.
Comments Invited
This AD is a final rule that involves requirements affecting flight safety, and we did not provide you with notice and an opportunity to provide your comments before it becomes effective. However, we invite you to send any written data, views, or arguments about this AD. Send your comments to an address listed under the ADDRESSES section. Include the docket number FAA-2011-0695 and directorate identifier 2011-SW-001- AD at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this AD. We will consider all comments received by the closing date and may amend this AD because of those comments.
We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive about this AD.
Costs of Compliance
We estimate that this AD affects 12 helicopters of U.S. registry. We estimate the following costs to comply with this AD:
Estimated Costs --------------------------------------------------------------------------------------------------------------------------------------------------------
Cost per
Action Labor cost Parts cost product Cost on U.S. operators -------------------------------------------------------------------------------------------------------------------------------------------------------- 1 work hour to visually inspect the 1 work-hour x $85 per N/A........................................ $85 $1,020.
hub. hour = $85.
[[Page 41664]]
1 work hour to eddy current inspect 1 work-hour x $85 per N/A........................................ $85 $1,020.
the lower hub [new action].hour = $85. Required parts and labor to replace a 11 work hours x 85 per $12,480 per hub............................ $13,415 $160,980.
lower hub. hour = $935.
-----------------------------------------------------------------------------------------------------------------
Total............................. $1,105................... $12,480.................................... $13,585 $163,020 assuming the
lower hubs are replaced
for the entire fleet. --------------------------------------------------------------------------------------------------------------------------------------------------------
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.We are 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) Is not a ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979),
(3) Will not affect intrastate aviation in Alaska, and
(4) 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.