The FAA issued Priority Letter AD 97-15-15 on July 18, 1997, prompted by two occurrences of MGB planetary gear shaft cracks, AD 97-15-15 was published in the Federal Register on February 6, 1998 (63 FR 6069). It requires that the magnetic chip plug on any MGB that was not modified in accordance with MOD 077244 be inspected after every flight and the MGB oil filter be inspected after the last flight of each day or at intervals not to exceed 12 hours time-in-service (TIS). The presence of any ferrous chips or any reports of abnormal vibrations by the flight crew requires a MGB ground vibration evaluation before further flight. Eurocopter France has recently advised the FAA that the potential for planetary gear shaft cracks exists for all MGB variants, regardless of modification level, currently authorized for installation on FAA-certified Model SA-365/366 helicopters. The temporary installation of the VLMU enables the flight crew to more easily and accurately assess the vibration level of the MGB prior to each flight. The manufacturer is pursuing a redesign of the affected MGB that will probably result in a mandatory modification of the MGB and constitute a terminating action for the requirements of this AD. It is anticipated that after the modification is accomplished, the VLMU will no longer be required.
The Direction Generale de L'Aviation Civile (DGAC), which is the airworthiness authority for France, has notified the FAA that an unsafe condition may exist on Eurocopter France Model SA-365N, N1, N2, and N3, and SA-366G1 helicopters. The DGAC advises that, based on two reports of cracks detected on the gear shaft, an AD is necessary to mandate the installation and the utilization of an MGB vibration level unit that detects vibrations at the shaft rotation frequency and indicates the potential for a crack in the gear shaft.
Eurocopter France has issued Eurocopter AS 365 Service Bulletin No. 31.00.03, applicable to ModelSA-365N, N1, N2, and N3, helicopters; and Eurocopter SA 366 Service Bulletin No. 31.01, applicable to Model SA-366G1 helicopters, both dated June 23, 1998. These service bulletins provide for the installation of a VLMU that enables a ground check for vibrations amplitude at the shaft rotational frequency and provides an indication to the pilot when the amplitude of vibration reaches a level that could indicate the existence of a crack in the gear shaft. The service bulletins also provide for checks of the MGB chip plug and oil filter, and measurements of on-ground vibration levels if the VLMU becomes inoperative. The DGAC classified these service bulletins as mandatory and issued AD 98-324-045(A), applicable to Model 365N helicopters, and AD 98-323-023(A), applicable to Model 366 helicopters, both dated August 12, 1998, in order to assure the continued airworthiness of these helicopters in France.
These helicopter models are manufactured in France and are type certificated foroperation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, the DGAC has kept the FAA informed of the situation described above. The FAA has examined the findings of the DGAC, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States.
Since an unsafe condition has been identified that is likely to exist or develop on other Eurocopter France SA-365N, N1, N2, and N3, and SA-366G1 helicopters of the same type design registered in the United States, this AD is being issued to detect cracks in the MGB planetary gear shaft, which could lead to failure of the MGB and subsequent loss of control of the helicopter. This AD requires installing a MGB VLMU to enable a preflight MGB vibration check, revising the RFM normal, emergency and limitations sections, and if the VLMU becomes inoperative, inspecting the MGB magnetic plug after every flight and the oil filter each day in which flights are conducted (not to exceed 12 hours time-in-service between inspections). The actions are required to be accomplished in accordance with the applicable service bulletins described previously. If metallic particles are found on the magnetic plug or oil filter, drive system ground vibration measurements must be conducted. The short compliance time involved is required because the previously described critical unsafe condition can adversely affect the structural integrity of the helicopter. Therefore, the actions are required within 25 hours time-in-service and this AD must be issued immediately.
Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.
The FAA estimates that 26 helicopters will be affected by this AD, that it will take approximately 10 work hours to install the VLMU, and that the average labor rate is $60 per work hour. The manufacturer has stated that required parts are available at no cost. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $15,600.
Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications should identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.
Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket No. 98-SW-47-AD." The postcard will bedate stamped and returned to the commenter.
The regulations adopted herein will not have substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.
The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (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.
39.13 [Amended]
2. Section 39.13 is amended by adding a new airworthiness directive to read as follows: