E7-41. Airworthiness Directives; MD Helicopters, Inc. Model 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HS, 369HM, 500N, and OH-6A Helicopters

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Supplemental notice of proposed rulemaking; reopening of comment period.

SUMMARY:

This document revises an earlier proposed airworthiness directive (AD) for MD Helicopters, Inc. (MDHI) Model 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HS, 369HM, 500N, and OH-6A helicopters that would have required replacing or reworking certain forward (fwd) and aft landing gear assemblies. That proposal was prompted by five reports of landing gear strut (strut) failures. This action revises that action by proposing to mandate both the creation of an access hole to facilitate inspections and a recurring inspection. The proposed AD also would exclude from the applicability certain helicopters modified with a certain Supplemental Type Certificate (STC) and would provide a terminating action for the proposed requirements. This proposal also includes clarifying changes. The actions specified by this proposed AD are intended to detect a crack that could result in the failure of a strut and subsequent loss of control of the helicopter during landing.

DATES:

Comments must be received on or before March 9, 2007.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Office of the Regional Counsel, Southwest Region, Attention: Rules Docket No. 2003-SW-37-AD, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137. You may also send comments electronically to the Rules Docket at the following address: [e-mail]. Comments may be inspected at the Office of the Regional Counsel between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays.

The service information referenced in the proposed rule may be obtained from MD Helicopters Inc., Attn: Customer Support Division, 4555 E. McDowell Rd., Mail Stop M615, Mesa, Arizona 85215-9734, telephone [phone], fax [phone], or on the web at http://www.mdhelicopters.com. This information may be examined at the FAA, Office of the Regional Counsel, Southwest Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas.

FOR FURTHER INFORMATION CONTACT:

John Cecil, Aviation Safety Engineer, FAA, Los Angeles Aircraft Certification Office, Airframe Branch, 3960 Paramount Blvd., Lakewood, California 90712-4137, telephone [phone], fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the proposed 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 above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this document may be changed in light of the comments received.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their mailed comments submitted in response to this proposal must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket No. 2003-SW-37-AD.” The postcard will be date stamped and returned to the commenter.

Discussion

A proposal to amend 14 CFR part 39 to add an AD for the specified MDHI model helicopters was published in the Federal Register on August 4, 2004 (69 FR 47040). That proposal would have required removing all landing gear fairings; determining the number and location of rivets that attach the landing gear fairing support assembly to the landing gear strut; and if three rivets (fwd, aft and inboard) are present, replacing or reworking the landing gear assembly. If only the fwd and aft rivets are present, no rework would be required by the proposed AD. That proposal was prompted by five reports of strut failures. Operators of the helicopters with failed struts do not fall into any clear category of service. For example, one was a tour operator in Niagara Falls, New York and another was a police department operator in Calgary, Canada. In its original design, the fairing support was attached to the strut with three rivets (forward, aft, and outboard). In 1994, the manufacturer released a design change to attach the fairing support assembly with only forward and aft rivets because of the possibility of reduced service life of the strut if the third rivet was located on the inboard side of the strut. Some landing gear struts entered service with an additional rivet hole drilled on the inboard side of the strut. This additional rivet hole results in decreased fatigue strength of the strut and subsequent cracking. That condition, if not corrected, could result in cracking of the fwd and aft struts, failure of a strut, and subsequent loss of control of the helicopter during landing.

Since issuing that proposal, we received several comments from 2 commenters and agree that we should make some changes to our proposed AD. We have determined that it is necessary to reopen the comment period to provide additional opportunity for public comment since we are making changes that expand the scope of the originally proposed rule. Due consideration was given to all of the comments received.

One commenter, the manufacturer, states that we need to mandate the installation of the landing gear fairing inspection hole rather than specifically excluding it from the proposed requirements as we did in the notice of proposed rulemaking (NPRM). The commenter also states that we should have the operators commence the periodic crack inspection per the maintenance manual. The commenter states that without these two critical additions the likelihood of a strut failure due to fatigue still exists.

After further consideration, we agree that having an inspection hole in the fairing would be preferable to removing the fairings every 100 hours time-in-service (TIS) or annually in order to do the inspection of the inboard rivet hole. We have also determined that our decision not to propose to mandate the repetitive crack inspection in the NPRM was an error. Therefore, we are now proposing to mandate the drilling of the access hole as well as the repetitive crack inspections of the inboard rivet. We have also added Notes in this proposal that include information for doing the inspections.

The same commenter provided us with a marked-up proposal that contains suggested word changes or additional information, but did not provide justification for those changes. We have made only those changes that clarify or correct the proposal.

One of those suggested changes was a request to change the wording we use to describe the intent of the proposed actions. The commenter writes that the intent of the proposed AD is to detect cracks of the fwd and aft struts, remove cracked struts from service prior to failure, and preclude subsequent extensive damage to the helicopter during landing. Although we agree that the proposal is intended primarily to detect cracks, we maintain that such cracking could lead to fatigue failure of the strut and loss of control of the helicopter during landing; therefore we have not made any changes to the proposal.

Another requested change is that we change the number of work hours to determine the number of rivets from 7 to 2, that we include the fairing as a part that may need to be reworked, and that we reduce the cost impact of the proposed AD from $438,800 to $227,225. In the NPRM, we erroneously estimated that it would take 7 work hours to determine the number of rivets; we agree with the commenter's suggestion that 2 hours is more appropriate and have revised the proposal accordingly. Also, since we are now proposing to mandate these actions, we have added the work hours and costs associated with both drilling the inspection hole in the fairing and accomplishing the repetitive inspections.

The commenter also requests that we add the address for obtaining service information. It is not appropriate to include the manufacturer's address within the regulatory text of the AD and we have not done so; however, we have included that address in the ADDRESSES section of this proposal and will add the address in the Incorporation by Reference paragraph of the Final Rule when it is issued.

Also requested is that we more specifically identify the “three rivets” in the Discussion of the proposal and that part of the intent of the AD is to “clean up the inboard rivet hole (de-burr). We agree only to more specifically identify the “three rivets” and have modified the proposal accordingly.

Finally, the commenter requests that we change the proposal to mandate only the recording of the initial inspection in the logbook but not any subsequent periodic landing gear inspections. We do not agree with this comment; all required inspections must be recorded. For the subsequent landing gear inspections proposed by this action, a Part 91 operator, for example, would be required by 39.7 to comply with the requirements of the AD, would be required by 43.11 to make entries in the maintenance records after any required inspection is performed, and would be required by 91.417 to keep maintenance records of required inspections. Therefore, we have not made the requested change.

Another commenter, a manufacturer, suggests that operators who can verify that their helicopters have an Aerometals strut (P/N 369XH6001-41, -42, -51, -52) that was “installed” under STC No. SR00981LA should not have to take any further actions at the strut locations because those struts are only approved to have fairing supports attached with two rivets (forward and aft) and they have never been approved for a third, inboard rivet. The commenter states that excluding the struts that they manufactured will result in a substantial savings to operators because their landing gear fairings will not have to be removed from a strut to verify the number of rivets attaching the fairing support since their installation should be annotated in the maintenance records. We agree with the commenter and have excluded those struts from the applicability of this proposal.

Because some of these changes expand the scope of the originally proposed rule, we have determined that it is necessary to reopen the comment period to provide additional opportunity for public comment.

The FAA estimates that this proposed AD would affect 651 helicopters of U.S. registry. Determining the number of rivets and initially inspecting each affected “3-hole” strut and fairing would take approximately 2 work hours, installing a new strut would take approximately 1.5 work hours, and reworking a strut would take 1 work hour. Each repetitive inspection would take 1/4 work hour per strut (1 hour per helicopter for each of 4 struts). The average labor rate is $80 per work hour. Required parts (new struts) would cost approximately $2,838 for each forward strut, $2,574 for each aft strut, and $97 for a modification kit to install an inspection hole. Assuming that each helicopter would get the initial inspection, that all 651 helicopters would be modified, that 325 helicopters would need two struts reworked, that 5 helicopters would require 2 new forward struts, and that 2 repetitive inspections would be required per year, the total estimated cost of the proposed AD on U.S. operators would be about $353,047 ($248,887 for the initial inspections, modification, and parts, and $104,160 for the repetitive inspections).

Regulatory Findings

The regulations proposed herein would 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 proposal would not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that this proposed regulation (1) is not a “significant regulatory action” under Executive Order 12866; (2) is not a “significant rule” under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) if promulgated, will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, Section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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:

MD Helicopters, Inc.: Docket No. 2003-SW-37-AD.

Applicability: Model 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HS, 369HM, 500N, and OH-6A helicopters, with any of the components listed in the Applicability Table installed, excluding any model with Aerometals strut (part number (P/N) 369XH6001-41, -42, -51, or -52) installed in accordance with Supplemental Type Certificate (STC) No. SR00981LA, certificated in any category:

Applicability Table

Component name	Component part number (P/N)
Mid Aft Fairing Assembly	369H6200-61, -62, standard gear.
Aft Support Assembly	369H6200-23, -24 (-23 to be reinstalled on the right-hand side and -24 to be reinstalled on the left-hand side, all configurations).
Aft Fairing Assembly	369H92113-91, -92, extended gear.
Aft Filler Assembly	369H92113-131, -132, extended gear.
Aft Fillet Assembly	369A6200-45, -46, standard gear.
Aft Fillet Assembly	369H92113-111, -112, extended gear.
Mid Fwd Fairing Assembly	369H6200-41, -42, standard gear.
Fwd Fairing Assembly	369H92113-81, -82, extended gear.
Fwd Support Assembly	369H6200-23, -24 (-23 becomes right-hand side and -24 becomes left-hand side).
Fwd Filler Assembly	369H92113-121, -122, extended gear.
Fwd Fillet Assembly	369A6200-57, -58, standard gear.
Fwd Fillet Assembly	369H92113-101, -102, extended gear.

Compliance: Required as indicated.

To detect a crack that could result in the failure of a strut and subsequent loss of control of the helicopter during landing, accomplish the following:

(a) Within 4 months, unless accomplished previously, remove all landing gear fairings (fairings) and inspect each landing gear fairing support assembly (support assembly) to determine the number and location of the rivets attaching the support assembly to the landing gear strut assembly (strut assembly).

(1) If three rivets (forward, aft and inboard) are used to attach the support assembly to the strut assembly,

(i) For each FORWARD landing gear assembly, remove the landing gear fillet assembly (fillet assembly), the three rivets, and the support assembly, and clean and dye-penetrant inspect the area in and around the 0.125 (3.18mm) diameter hole in the inboard surface of the strut assembly.

(A) If the strut assembly is cracked, replace the cracked strut assembly with an airworthy strut assembly and install the other landing gear components in accordance with steps (6) through (11) of paragraph C of the Accomplishment Instructions of MD Helicopters Service Bulletin SB369H-244, SB369E-094, SB500N-022, SB369D-200, and SB369F-078, dated April 7, 2000 (SB).

(B) If the strut assembly is not cracked, rework the landing gear assembly and install the other landing gear components in accordance with steps (5) through (11) of paragraph C of the Accomplishment Instructions of the SB.

(ii) For each AFT landing gear assembly, remove the fillet assembly, the three rivets, and the support assembly, and clean and dye-penetrant inspect the area in and around the 0.125 (3.18mm) diameter hole in the inboard surface of the strut assembly.

(A) If the strut assembly is cracked, replace the cracked strut assembly with an airworthy strut assembly and install the other landing gear components in accordance with steps (6) through (13) of paragraph B of the Accomplishment Instructions of the SB.

(B) If the strut assembly is not cracked, rework the landing gear assembly and install the other landing gear components in accordance with steps (5) through (13) of Paragraph B of the Accomplishment Instructions of the SB.

(2) If only two rivets (forward and aft) are used to attach the support assembly to the strut assembly and a third rivet hole has not been drilled in the strut, neither the inspection of the strut assembly nor the rework of those landing gear assemblies is required by this AD.

(b) At intervals not to exceed 100 hours TIS or during each annual inspection, whichever occurs first, for any strut assembly that has a third rivet hole, remove the fairing inspection button plug and clean and inspect the area in and around the rivet hole for cracks using a bright light and 1 10x or higher magnifying glass.

(1) If any FORWARD strut assembly is cracked, replace the cracked strut with an airworthy strut assembly.

(2) If any AFT strut assembly is cracked, replace the cracked strut with an airworthy strut assembly.

(c) Installing a strut assembly that has only 2 rivet holes is terminating action for the requirements of this AD.

Note 1:

For the Model 369D, 369E, 369F, 369FF, and 500N helicopters, the Handbook of Maintenance Instruction, Servicing and Maintenance, HMI, CSP-HMI-2, Chapter 32, Section 32-10-00, “Landing Gear Strut Inspection” pertains to the subject of this AD.

Note 2:

For the Model 369(A) (OH-6A), 369H, 369HE, 369HS, and 369HM helicopters, the Basic Handbook of Maintenance Instructions CSP-H-2, Section 6, “Landing Gear” pertains to the subject of this AD.

(d) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Contact the Los Angeles Aircraft Certification Office, Transport Airplane Directorate, FAA, for information about previously approved alternative methods of compliance.

Issued in Fort Worth, Texas, on December 26, 2006.

David A. Downey,

Manager, Rotorcraft Directorate, Aircraft Certification Service.