The Luftfahrt-Bundesamt (LBA), which is the airworthiness authority for the Federal Republic of Germany recently notified the FAA that an unsafe condition may exist on Eurocopter Deutschland Model BO-105A, BO-105C, BO-105S, BO-105LS A-1, and BO-105LS A-3 helicopters. The Federal Republic of Germany advises that a main rotor mast was found to have cracks of critical magnitude in the area of the flange. Additionally, Transport Canada, the airworthiness authority for Canada, recently notified the FAA that the same unsafe condition may exist on Eurocopter Canada Ltd. Model B0-105LS A-3 helicopters. The cause of the cracks is under investigation. Until the cause of the crack has been determined, the flange must be subjected to an immediate inspection and repetitive visual crack inspection at intervals not to exceed 100 hours time-in-service until further notice. \n\n\tEurocopter Deutschland has issued Eurocopter Deutschland GmbH Alert Service Bulletin No. ASB-BO 105-10-110, dated August 27, 1997, which specifies visually inspecting the area of the holes on the underside of the flange for cracks, especially in the ribbed area between the holes. The LBA classified this service bulletin as mandatory and issued AD 97-275, dated September 25, 1997, in order to assure the continued airworthiness of these helicopters in the Federal Republic of Germany. Eurocopter Canada Ltd. has issued Eurocopter Canada Ltd. Alert Service Bulletin No. ASB-BO 105 LS-10-9, dated September 11, 1997, for similar inspection. Transport Canada has classified this service bulletin mandatory and issued AD CF-97-18, dated September 30, 1997, in order to assure the continued airworthiness of these helicopters in Canada. \n\n\tThis helicopter model is manufactured in the Federal Republic of Germany and Canada and is 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 LBA and Transport Canada have kept the FAA informed of the situation described above. The FAA has examined the findings of the LBA and Transport Canada, 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. \n\n\tSince an unsafe condition has been identified that is likely to exist or develop on other Eurocopter Deutschland Model BO-105A, BO-105C, BO-105S, BO-105LS A-1, and BO-105LS A-3 helicopters and Eurocopter Canada Ltd. BO-105LS A-3 helicopters of the same type designs registered in the United States, this AD is being issued to detects cracks in the flange, which, if not detected, could result in failure of the flange and subsequent loss of control of the helicopter. The flange is a part of the main rotor mast assembly and therefore a critical component of the flight control system. Due to the criticality of the flange to the continued safe flight of the affected helicopters, and the required inspection before further flight, this rule must be issued immediately to correct an unsafe condition in the affected helicopters. This AD requires, before further flight, a visual inspection of the ribbed area of the flange for cracks using a 5-power or higher magnifying glass, and thereafter, repeated visual inspections at intervals not to exceed 100 hours time-in- service. The actions are required to be accomplished in accordance with the service bulletins described previously. \n\n\tSince 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. Comments Invited \n\n\tAlthough 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. \n\n\tComments 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. \n\n\tCommenters 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-44-AD." The postcard will be date stamped and returned to the commenter. \n\n\tThe 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. \n\n\tThe FAA has determined that this regulationis 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." \n\nList of Subjects in 14 CFR Part 39 \n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \n\tAccordingly, 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: \n\nPART 39 - AIRWORTHINESS DIRECTIVES \n\t1. The authority citation for part 39 continues to read as follows: \n\tAuthority: 49 USC 106(g), 40113, 44701. \n\n§ 39.13 - (Amended) \n\t2. Section 39.13 is amended by adding a new airworthiness directive to read as follows: