Discussion
We recently received a report of abnormal main rotor blade vibration on a Eurocopter Model EC135 helicopter. This main rotor blade vibration occurred after initial aircraft start, while operating at flat pitch, between 8.5 and 25 percent torque and 98.6 percent NR/N2 speed, and dissipated once the FADEC switches were advanced to FLIGHT. The main rotor transmission chip light also illuminated with minimal debris found on the chip detectors. During troubleshooting, six of the eight main transmission lower hub-shaft bearing support bolts were found lying in the bottom of the main transmission case, atop of the lower transmission access panel. Only two of the eight bolts remained installed, loose in their positions, and the outer race of the roller bearing was rotated out of position (cocked). Approximately three weeks after that first incident, we received a report that loose bolts were discovered on two additional newer helicopters that hadnot been inspected at the time the loose bolts were discovered on the first helicopter. Subsequent investigations revealed that screws were not properly torqued and vibrations had caused the screws to back-out. Loosened screws in the bearing support, if not detected and corrected, could result in abnormal main rotor blade vibrations and subsequent damage to the main transmission.
EASA has issued EASA Emergency AD 2008-0175-E, dated September 16, 2008, to correct an unsafe condition for the Eurocopter Model EC135 helicopters. The MCAI explains that "The lower hub-shaft bearing consists of a ball bearing and a roller bearing. The outer race of the roller bearing is fixed to the housing with screws. Should all attachment screws become loose, the outer race of the roller bearing might separate, which would constitute an unsafe condition. In such case, however, the axial guidance of the rotor hub-shaft would still be ensured.'' The MCAI requires inspecting the main transmission attachment hardware and installing locking washers. You may obtain further information by examining the MCAI and any related service information in the AD docket.
Related Service Information
Eurocopter has issued Alert Service Bulletin EC135-63A-013, Revision 2, dated September 12, 2008 (ASB). The ASB specifies checking the screws at the lower hub-shaft bearing for correct attachment and securing attachment hardware by means of locking washers. The actions described in the MCAI are intended to correct the same unsafe condition as that identified in the service information.
FAA's Evaluation and Unsafe Condition Determination
This product has been approved by the aviation authority of Germany, and is approved for operation in the United States. Pursuant to our bilateral agreement with Germany, EASA, their Technical Agent, has notified us of the unsafe condition described in the MCAI. We are issuing this AD because we evaluated all information provided by EASA and determined the unsafe condition exists and is likely to exist or develop on other helicopters of the same type design.
Differences Between This AD and the MCAI AD
This AD does not require sending the main transmission to the manufacturer and does not refer to the transmission part numbers. Also, this AD uses the term "hours time-in-service'', the MCAI AD uses the term "flight cycles''.
Costs of Compliance
We estimate that this AD will affect about 189 helicopters of U.S. registry. We also estimate that it will take about 8 work-hours to inspect and install lock washers, at an average labor rate of $80 per work-hour. Required parts will cost about $574 per helicopter ($86 for the lock washers and $488 for the required oil). Based on these figures, we estimate the cost of this AD on U.S. operators will be $229,446 ($1,214 per helicopter).
FAA's Determination of the Effective Date
An unsafe condition exists that requires the immediate adoption of this AD. We find that the risk to the flying public justifies waiving notice and comment prior to adoption of this rule because loosened screws in the bearing support, if not detected and corrected quickly, could result in abnormal main rotor blade vibrations and subsequent damage to the main transmission. Therefore, we have determined that notice and opportunity for public comment before issuing this AD are impracticable and that good cause exists for making this amendment effective in fewer than 30 days.
Comments Invited
This AD is a final rule that involves requirements affecting flight safety, and we did not precede it by notice and opportunity for public comment. However, we invite you to send us any written data, views, or arguments concerning this AD. Send your comments to an address listed under the ADDRESSES section of this AD. Include "Docket No. FAA-2009- 0482; Directorate Identifier 2008-SW-54-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.
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 product(s) identified in this rulemaking action.
Regulatory Findings
We determined that 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.
Therefore, I certify this AD:
1. Is not a "significant regulatory action'' under Executive Order 12866;
2. Is not a "significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and
3. Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of theRegulatory Flexibility Act.
We prepared an economic evaluation of the estimated costs to comply with this AD and placed it in the AD docket.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of 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 AD: