On July 18, 1997, the FAA issued priority letter AD 97-15-15, applicable to Eurocopter France Model SA-365N, SA-365N1, and SA-366G1 helicopters, which requires an inspection of the magnetic plug and the oil filter for ferrous chips; vibration measurements, if necessary; and replacement of the main gearbox if a specified quantity of ferrous chips are discovered, or if abnormal vibrations are identified at a certain frequency. That action was prompted by two recent reports of cracks found in gear shafts in main gearboxes, part number (P/N) 365A32-6000-00, 365A32-6000-02, 365A32-6001-00, or 366A32-0001-00, that have not been modified in accordance with MOD 077244. Upon inspection, the manufacturer discovered that 13 main gearbox epicyclic modules were assembled at the factory with mismatched planetary gear tooth to ring gear radii. This produces higher than normal gear tooth loading stresses which substantially reduce the fatigue life of the gear shaft. This condition, if not corrected, could result in cracks in the gear shaft, failure of the transmission, and subsequent loss of control of the helicopter.
Eurocopter France has issued Telex Service No. 0035/00188/97, dated July 7, 1997, and Telex Service No. 00037/00190/97, dated July 9, 1997, which specify checks of the oil filter after the last flight of each day for cracks; and also specify performing vibration measurements if metal chips are found on the magnetic plug or in the oil filter, or if abnormal vibrations are reported by the crew. The DGAC classified these service telexes as mandatory, and issued AD 97-145-042(AB), dated July 10, 1997, and AD 97-164-020(AB), dated July 16, 1997.
These helicopter models are manufactured in France and are type certificated for operation 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 Direction Generale de L'Aviation Civile (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 the unsafe condition described is likely to exist or develop on other Eurocopter France Model SA-365N, SA-365N1, and SA-366G1 helicopters of the same type design, the FAA issued priority letter AD 97-15-15 to detect cracks in the gear shaft which could lead to failure of the gear shaft, failure of the transmission, and subsequent loss of control of the helicopter. The AD requires an inspection of the magnetic plug for ferrous chips after each flight when the main rotor is stopped, and an inspection of the oil filter for ferrous chips after the last flight of each day or at intervals not to exceed 12 hours time-in-service, whichever occurs first. If ferrous chips are discovered as a result of either inspection, or if abnormal vibrations are reported by the flight crew, then vibration measurements must be performed on the ground. If vibration levels above the helicopter's basic data are identified at a frequency of 26.07 HZ, or if an accumulation of ferrous chips found on the magnetic plug and in the oil filter is equal to or greater than an area of 0.08 in2 (50 mm2), removal of the main gearbox before further flight and replacement with an airworthy main gearbox is required.
Since it was found that immediate corrective action was required, notice and opportunity for prior public comment thereon were impracticable and contrary to the public interest, and good cause existed to make the AD effective immediately by individual letters issued on July 18, 1997 to all known U.S. owners and operators of Eurocopter France Model SA-365N, SA-365N1, and SA-366G1 helicopters. These conditions still exist, and the AD is hereby published in the Federal Register as an amendment to section 39.13 of the Federal Aviation Regulations (14 CFR 39.13) to make it effective to all persons. 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. 97-SW-23-AD." The postcard will be date 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 39Air transportation, Aircraft, Aviation safety, 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: