AD 2000-01-11

This amendment supersedes an existing emergency priority letter airworthiness directive (AD), applicable to Eurocopter Deutschland GMBH (ECD) Model MBB-BK 117 helicopters, that currently requires, before further flight, creating a component log card or equivalent record and determining the age and number of flights on the tension-torsion (TT) strap. The AD also requires inspecting and removing, as necessary, certain unairworthy TT straps. This amendment requires the same actions as the emergency priority letter AD but clarifies the compliance requirements specified in the emergency priority letter AD. This amendment is prompted by an accident in which a main rotor blade (blade) separated from a helicopter due to fatigue failure of a TT strap. The actions specified by this AD are intended to prevent failure of a TT strap, loss of a blade, and subsequent loss of control of the helicopter.

Final rule; request for comments

2000-01-11 EUROCOPTER DEUTSCHLAND GMBH: Amendment 39-11509. Docket No. 99-SW-60-AD. Supersedes Emergency Priority Letter AD 99-17-07, Docket No. 99-SW-49-AD.
Applicability: Model MBB-BK 117 A-1, A-3, A-4, B-1, B-2, and C-1 helicopters, certificated in any category.

NOTE 1: This AD applies to each helicopter identified in the preceding applicability provision, regardless of whether it has been otherwise modified, altered, or repaired in the area subject to the requirements of this AD. For helicopters that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (f) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To prevent main rotor blade (blade) separation due to failure of a tension-torsion (TT) strap, accomplish the following:

(a) Before further flight,

(1) Create a component log card or equivalent record for each TT strap.

(2) Review the history of the helicopter and each TT strap. Determine the age since initial installation on any helicopter (age) and the number of flights on each TT strap. Enter both the age and the number of flights for each TT strap on the component log card or equivalent record. Where the number of flights is unknown, multiply the number of hours time-in-service (TIS) by 5 to determine the number of flights.

(3) If the number of flights and age cannot be determined, remove the TT strap from service.

(4) Remove any TT strap from service that has either accumulated 25,000 or more flights or is equal to or greater than 180 months ofage.

(b) When a TT strap age is equal to or greater than 120 months and less than 180 months and the number of flights on the TT straps are less than 25,000, inspect the TT strap in accordance with paragraph 2.B.2 of the "Accomplishment Instructions," Eurocopter Deutschland GMBH Alert Service Bulletin MBB-BK 117 No. ASB-MBB-BK 117-10-120 (ASB), Revision 1, dated August 31, 1999, according to the following:

(1) If the age is greater than or equal to 120 months but less than 132 months and has less than 22,000 flights, inspect the TT strap within the next 6 weeks. If the number of flights equals or exceeds 22,000, inspect the TT strap before further flight.

(2) If the age is greater than or equal to 132 months but less than 144 months and has less than 19,000 flights, inspect the TT strap within the next 5 weeks. If the number of flights equals or exceeds 19,000, inspect the TT strap before further flight.

(3) If the age is greater than or equal to 144 months butless than 156 months and has less than 16,000 flights, inspect the TT strap within the next 4 weeks. If the number of flights equals or exceeds 16,000, inspect the TT strap before further flight.

(4) If the age is greater than or equal to 156 months but less than 168 months and has less than 13,000 flights, inspect the TT strap within the next 3 weeks. If the number of flights equals or exceeds 13,000, inspect the TT strap before further flight.

(5) If the age is greater than or equal to 168 months but less than 180 months and has less than 10,000 flights, inspect the TT strap within the next 2 weeks. If the number of flights equals or exceeds 10,000, inspect the TT strap before further flight.

Remove any TT strap from service before exceeding the allowable number of flights or 180 months, whichever occurs first.

(c) If a defect is found as a result of the inspection, remove the TT strap from service prior to further flight.

(d) If no defect is found as aresult of the inspection in paragraph (b), a maximum of 500 flights is permitted on a one-time basis before the TT strap must be replaced, provided the limits of paragraphs (a)(4) and (b) are not exceeded.

(e) TT straps, part number (P/N) 2604067 or J17322-1, are not eligible for installation. Prior to installation, P/N 2604067 or J17322-1 must be re-identified according to paragraph 2.B.1 of the "Accomplishment Instructions" of the ASB, Revision 1, dated August 31, 1999.

(f) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Regulations Group, FAA. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Regulations Group.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Regulations Group.

(g) Special flight permits may be issued for up to five flights in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the helicopter to a location where the requirements of this AD can be accomplished.

(h) The inspections and re-identification of TT straps shall be done in accordance with the "Accomplishment Instructions," paragraph 2.B.1 and 2.B.2, of Eurocopter Deutschland GMBH Alert Service Bulletin MBB BK 117 No. ASB-MBB-BK 117-10-120, Revision 1, dated August 31, 1999. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from American Eurocopter Corporation, 2701 Forum Drive, Grand Prairie, Texas 75053-4005, telephone (972) 641-3460, fax (972) 641-3527. Copies may be inspected at the FAA, Office of the Regional Counsel, Southwest Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

NOTE 3: The subject of this AD is addressed in Luftfahrt-Bundesamt (LBA), Federal Republic of Germany, AD 1999-284, dated August 6, 1999.

(i) This amendment becomes effective on January 28, 2000.

FOR FURTHER INFORMATION CONTACT: Charles Harrison, Aerospace Engineer, FAA, Rotorcraft Directorate, Rotorcraft Standards Staff, 2601 Meacham Blvd., Fort Worth, Texas 76137, telephone (817) 222-5128, fax (817) 222-5961.

On August 6, 1999, the FAA issued Emergency Priority Letter AD 99-17-07, applicable to ECD Model MBB-BK 117 helicopters, which requires, before further flight, creating a component log card or equivalent record and determining the calendar age and number of flights on the TT strap. The AD also requires inspecting and removing, as necessary, certain unairworthy TT straps. Certain TT straps are not eligible for installation until they are re-identified. That action was prompted by an accident in which a blade separated from an ECD Model MBB-BK-117 helicopter resulting in three fatalities. The cause of the blade separation was a TT strap rupture within the main rotor head. The cause of the TT strap rupture remains under investigation. That condition, if not corrected, could result in failure of a TT strap, loss of a blade, and subsequent loss of control of the helicopter.

Since the issuance of that emergency priority letter AD, the FAA has receivedseveral requests for clarification of the terms "calendar year" and "calendar age." To clarify the required compliance times, the FAA has converted years to months and has removed the terms "calendar year" and "calendar age" from the AD.

The FAA has reviewed ECD Alert Service Bulletin MBB-BK 117 No. ASB-MBB-BK 117-10-120, Revision 1, dated August 31, 1999 (ASB). The ASB describes procedures for determining the total accumulated installation time and number of flights on the TT strap. The ASB specifies inspecting each TT strap and replacing any unairworthy TT strap with an airworthy TT strap. The Luftfahrt-Bundesamt (LBA), which is the airworthiness authority for the Federal Republic of Germany, classified that ASB as mandatory and issued AD 1999-284, dated August 6, 1999, applicable to all ECD Model MBB-BK 117 helicopters.

Since an unsafe condition has been identified that is likely to exist or develop on other ECD Model MBB-BK 117 helicopters of the same type design, this AD supersedes Emergency Priority Letter AD 99-17-07 to require, before further flight, creating a component log card or equivalent record and determining the age and number of flights on each TT strap. The AD also requires inspecting and removing, as necessary, any unairworthy TT straps. Certain TT straps are not eligible for installation until they are reidentified. The actions must be accomplished in accordance with the ASB described previously. The short compliance time involved is required because the previously described critical unsafe condition can adversely affect the structural integrity of the helicopter. Therefore, creating a component log card or equivalent record, determining the age and number of flights on each TT strap, and inspecting and removing, as necessary, any unairworthy TT straps are required prior to further flight, and this AD must be issued immediately.

Since a situation exists that requires the immediate adoption of this regulation, it is foundthat 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 127 helicopters of U.S. registry will be affected by this AD, that it will take approximately 1 work hour per helicopter to inspect the 4 TT straps on each helicopter, 15 work hours per helicopter to remove and replace the 4 TT straps, if necessary, and the average labor rate is $60 per work hour. Required parts will cost approximately $2,600 per TT strap ($10,400 per helicopter). Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $1,442,720; $7,620 to inspect each helicopter once and $1,435,100 to remove and replace the 4 TT straps on all helicopters.

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. 99-SW-60-AD." The postcard will be date stamped and returned to the commenter.

The regulations adopted herein 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, it is determined that this final rule does not have federalism implications under Executive Order 13132.

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 (AD) to read as follows: