AD 2000-10-06

This amendment adopts a new airworthiness directive (AD) for MD Helicopters Inc. (MDHI) Model MD900 helicopters. This action requires visually inspecting the drive shaft to determine the assembly part number (P/N) and marking the drive shaft assembly P/N and serial number (S/N) on any unmarked drive shaft. This AD also requires creating a component history card or equivalent record for certain drive shaft assemblies and replacing any drive shaft assembly that has reached its life limit. This amendment is prompted by the discovery of several drive shafts with no assembly P/N marked on the part, which could result in a drive shaft remaining in service past its life limit. The actions specified in this AD are intended to prevent failure of the drive shaft due to fatigue, which could result in total loss of drive to the main rotor hub and subsequent loss of control of the helicopter.

Final rule; request for comments

2000-10-06 MD HELICOPTERS INC.: Amendment 39-11730. Docket No. 2000-SW-04-AD.
Applicability: Model MD900 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 (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 failure of the drive shaft due to fatigue, which could result in total loss of drive to the main rotor hub and subsequent loss of control of the helicopter; accomplish the following:

(a) Before accumulating 1,450 hours time-in-service (TIS), visually inspect the drive shaft assembly to determine which part number (P/N) is installed. If necessary, remove the drive plate cover to access the P/N located on the top edge of the drive shaft assembly. If the number of hours TIS on the drive shaft assembly is unknown, use the total hours TIS on the helicopter.

NOTE 2: Do not confuse the P/N of the drive shaft subassembly, P/N 900D2436028-101, 900D2436026-101, or 900D2436030-101 as the P/N of the drive shaft assembly.

(1) If a drive shaft assembly, P/N 900D2436530-101, is installed, no further action is required by this AD.

(2) If a drive shaft assembly other than P/N 900D2436530-101 is installed and is not marked with a P/N, before further flight, use an indelible ink finetip marking pen to mark the following information on the edge of the drive shaft assembly in line with the engraved subassembly number:

(i) P/N 900D2436528-101 and the serial number (S/N) of the drive shaft subassembly if the subassembly is P/N 900D2436028-101. When the ink dries, apply a clear coat over the P/N and S/N, or

(ii) P/N 900D6400004-101 and the S/N of the drive shaft subassembly if the subassembly is P/N 900D2436026-101. When the ink drives, apply a clear coat over the P/N and S/N.

(b) For a drive shaft assembly with 1,450 or more hours TIS, before further flight, accomplish paragraph (a) of this AD.

NOTE 3: MD Helicopters Inc. Service Bulletin SB900-062 R1, dated December 16, 1999, applies to the subject of this AD.

(c) After accomplishing the requirements of paragraph (a) of this AD, before further flight, determine the hours TIS of the drive shaft assembly. Record the hours TIS on a current or newly created component history card or equivalent record. If the drive shaft assembly has reached or exceeded its life limit, replace the drive shaft assembly with an airworthy drive shaft assembly before further flight.

NOTE 4: The Airworthiness Limitations Section, section 04, of the MD-900 Rotorcraft Maintenance Manual (CSP-900RMM-2), Revision 6, dated December 23, 1999, pertains to the subject of this AD.

(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, Los Angeles Aircraft Certification Office, FAA. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Los Angeles Aircraft Certification Office.

NOTE 5: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Los Angeles 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 helicopter to a location where the requirements of this AD can be accomplished.

(f) This amendment becomes effective on June 1, 2000.

This amendment adopts a new AD for MDHI Model MD900 helicopters. On February 19, 1999, the FAA issued AD 99-05-08, Amendment 39-11056 (64 FR 10209, March 3, 1999), for MDHI Model MD900 helicopters to establish or reduce life limits for various parts, including the drive shaft assembly. That AD was prompted by analysis that indicated a need for establishing or reducing life limits to avoid fatigue failure of certain parts. Since issuance of that AD, several drive shaft assemblies were found without a P/N marked on the drive shafts. This could result in the drive shaft remaining in service past its life limit since operators may mistakenly use the subassembly P/N for determining whether the life limit listed in AD 99-05-08 applies. A drive shaft in operation past its life limit could fail due to fatigue. This condition, if not corrected, could result in total loss of drive to the main rotor hub and subsequent loss of control of the helicopter.

The FAA has reviewed MDHI Service Bulletin (SB) SB900-062 R1, dated December 16, 1999, which describes procedures for visually inspecting the drive shaft to determine the assembly P/N and marking the drive shaft assembly P/N and serial number (S/N) on any unmarked drive shaft. The SB also specifies creating component history cards for certain drive shaft assemblies, verifying the life limit, and replacing the drive shaft assembly, if necessary.

Since an unsafe condition has been identified that is likely to exist or develop on other MDHI Model MD900 helicopters of the same type design, this AD is being issued to prevent failure of the drive shaft. This AD requires visually inspecting the drive shaft to determine the assembly P/N and marking the drive shaft assembly P/N and S/N on any unmarked drive shaft. This AD also requires creating component history cards for certain drive shaft assemblies and replacing the drive shaft assembly if the drive shaft assembly has reached its life limit. The short compliance time involved is required because the previously described critical unsafe condition can adversely affect controllability of the helicopter. Therefore, the actions of this AD are required prior to accumulating 1,450 hours time-in-service (TIS) on the drive shaft or before further flight if TIS equals or exceeds 1,450 hours, 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 this AD will affect 28 helicopters, that it will take approximately 2 work hours to accomplish the required actions, and that the average labor rate is $60 per work hour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $3,360.

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 mailed 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. 2000-SW-04-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, 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: