AD 99-14-06

This amendment adopts a new airworthiness directive (AD) that is applicable to MT-Propeller Entwicklung GMBH Models MTV-9-B-C and MTV-3-B-C propellers. This action requires initial and repetitive inspections of Torx head blade root lag screws for torque values and breakage, and, if any screws are found broken or with insufficient torque, replacement of all screws with new lag screws. In addition, this AD requires replacement of certain model Torx head blade root lag screws with improved, hexagonal head blade root lag screws. This amendment is prompted by reports of broken Torx head blade root lag screws. The actions specified in this AD are intended to prevent blade root lag screw breakage, which could result in propeller blade separation and loss of control of the airplane.

Final rule; request for comments.

99-14-06 MT-Propeller Entwicklung GMBH: Amendment 39-11216. Docket 99-NE-35-AD.
Applicability: MT-Propeller Entwicklung GMBH Model MTV-9-B-C propellers with serial numbers (S/Ns) starting with 98 or less, equipped with CL250-27 or CL260-27 blades with S/Ns starting with letter "A" through "P", equipped with Torx head blade root lag screws, P/N A-549-85 (3mm thread pitch), or P/N A-550-85 (4mm thread pitch); and Model MTV-3-B-C propellers with S/Ns starting with 98 or less, equipped with L250-21 blades with S/Ns starting with letter "A" through "P", equipped with Torx head blade root lag screws, P/N A-549-85 (3mm thread pitch), or A-550-85 (4mm thread pitch). These propellers are installed on but not limited to Sukhoi SU-26, SU-29, SU-31; Yakovlev YAK-52, YAK-54, YAK-55, and Technoavia SM-92 airplanes.

Note 1: This airworthiness directive (AD) applies to each propeller identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For propellers 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 (d) 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 blade root lag screw breakage, which could result in propeller blade separation and loss of control of the airplane, accomplish the following:

(a) For propellers with Torx head blade root lag screws, P/N A-549-85 (3mm thread pitch), perform initial and repetitive inspections of Torx head blade root lag screws for torque values and breakage, and, if necessary, replace with new lag screws, in accordance with MT-Propeller Entwicklung GMBH Service Bulletin (SB) No. 17-A, dated March 5,1999, as follows:

(1) Initially inspect within 50 hours time-in-service (TIS), or within 2 months after the effective date of this AD, whichever occurs first.

(2) Thereafter, inspect at intervals not to exceed 100 hours TIS, or within 12 months, whichever occurs first.

(3) Prior to further flight, if any Torx head blade root lag screws are found broken or with torque less than 64 foot-pounds, replace all Torx head blade root lag screws with new lag screws.

(b) For propellers with Torx head blade root lag screws, P/N A-550-85 (4mm thread pitch), perform a one-time inspection of Torx head blade root lag screws for torque values and breakage, and, if necessary, replace with lag screws, in accordance with MT-Propeller Entwicklung GMBH SB No. 17-A, dated March 5,1999, as follows:

(1) Inspect within 50 hours TIS, or within 2 months after the effective date of this AD, whichever occurs first.

(2) Prior to further flight, if any Torx head blade root lag screws are found broken or with torque less than 64 foot-pounds, replace all Torx head blade root lag screws with improved, hexagonal head blade root lag screws, P/N A-983-85.

(c) For propellers with Torx head blade root lag screws, P/N A-550-85 (4mm thread pitch), within 100 hours TIS, or within 12 months after the effective date of this AD, replace all Torx head blade root lag screws, P/N A-550-85, with improved, hexagonal head blade root lag screws, P/N A-983-85, in accordance with MT-Propeller Entwicklung GMBH SB No. 17-A, dated March 5,1999.

(d) 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, Boston Aircraft Certification Office. Operators shall submit their requests through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Boston Aircraft Certification Office.

Note 2: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Boston Aircraft Certification Office.

(e) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the inspection requirements of this AD can be accomplished.

(f) The actions required by this AD shall be performed in accordance with the following MT-Propeller Entwicklung GMBH SB:

Document No.
Pages
Date
17-A
1-3
March 5, 1999
Total pages: 3.

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 MT-Propeller Entwicklung GMBH, Airport Straubing-Wallmuhle, D-94348 Atting, Germany; telephone (0 94 29) 84 33, fax (0 94 29) 84 32, Internet: "propeller@aol.com". Copies may be inspected at the FAA, New England Region, Office of the Regional Counsel, 12 New England Executive Park, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street, NW, suite 700, Washington, DC.

(g) This amendment becomes effective on July 23, 1999.

he Luftfahrt-Bundesamt (LBA), which is the airworthiness authority for Germany, recently notified the Federal Aviation Administration (FAA) that an unsafe condition may exist on MT-Propeller Entwicklung GMBH Models MTV-9-B-C and MTV-3-B-C propellers. The LBA advises that they have received reports of broken Torx head blade root lag screws found during routine teardowns. The investigation revealed that the screws broke due to insufficient torque. This condition, if not corrected, could result in blade root lag screw breakage, which could result in propeller blade separation and loss of control of the airplane.

MT-Propeller Entwicklung GMBH has issued Service Bulletin (SB) No. 17-A, dated March 5, 1999, that specifies procedures for inspections for Torx head blade root lag screws for torque values and breakage, and replacement of Torx head blade root lag screws, part number (P/N) A-550-85 (4mm thread pitch), with improved, hexagonal head blade root lag screws, P/N A-983-85. The LBA classified this SB as mandatory and issued airworthiness directives (ADs) 1999-081/2 and 1999-082/2 in order to assure the airworthiness of these propellers in Germany.

This propeller model is manufactured in Germany 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 has kept the FAA informed of the situation described above. The FAA has examined the findings of the LBA, 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 propellers of the same type design registered in the United States, the AD requires initial and repetitive inspections of Torx head blade root lag screws for torque values and breakage, and, if any screws are found with insufficient torque or are broken, replacement of all screws with new lag screws. In addition, this AD requires replacement of Torx head blade root lag screws, P/N A-550-85 (4mm thread pitch), with improved, hexagonal head blade root lag screws, P/N A-983-85. The actions would be required to be accomplished in accordance with the SB described previously.

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.

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 withthe 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 notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 99-NE-35-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 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 the following new airworthiness directive: