AD 96-10-09

This amendment adopts a new airworthiness directive (AD) that is applicable to McDonnell Douglas Helicopter Systems (MDHS) Model 369, 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, and 500N helicopters. This action requires initial and repetitive inspections of each main rotor blade (blade) root for either cracks or paint and sealant cracking or separation between the lower surface root end fitting and the doubler. This amendment is prompted by one accident in which a blade separated from the helicopter, as well as eight other reports of cracked blades. The actions specified in this AD are intended to prevent failure of a blade resulting in separation of the blade and subsequent loss of control of the helicopter.

Final rule; request for comments

96-10-09 MCDONNELL DOUGLAS HELICOPTER SYSTEMS: Amendment 39-9615. Docket No. 96-SW-02-AD.

Applicability: Model 369, 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, and 500N 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 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 use the authority provided in paragraph (c) to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition, or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any helicopter from the applicability of this AD.

Compliance: Required as indicated, unless accomplished previously.

To prevent failure of a main rotor blade (blade) resulting in separation of the blade and subsequent loss of control of the helicopter, accomplish the following:

(a) Within 10 hours time-in-service (TIS) after the effective date of this AD, perform a visual inspection of each blade root end for cracking and paint or sealant cracking, paying particular attention to chordwise cracking, and for separation between the lower surface root end fitting and doubler, in accordance with Part I of the Accomplishment Instructions of McDonnell Douglas Helicopter Systems Service Information Notice (SIN) HN-239, DN-188, EN-81, FN-67, and NN-008, dated October 27, 1995. If any blade crack is noted, before further flight, remove the blade and replace it with an airworthy blade.If paint or sealant cracking or separation is noted, accomplish the inspection in paragraph 3E of Part II of the Accomplishment Instructions of SIN HN-239, DN-188, EN-81, FN-67, and NN-008, dated October 27, 1995, using a piece of Mylar/viewfoil that is no thicker than .004-inch and that is cut to a size between 0.9 inch and 1.1 inches wide and between 3.9 inches and 4.1 inches long. If any corner of the Mylar can be inserted between the lower surface root end fitting and doubler surface to a depth of 0.1 inch or greater, remove the blade from service and replace it with an airworthy blade.

(b) Thereafter, at intervals not to exceed 100 hours TIS, remove the blades and inspect for cracking, paying particular attention to chordwise cracking, and separation between the lower surface root end fitting and doubler in accordance with Part II of the Accomplishment Instructions of McDonnell Douglas Helicopter Systems SIN HN-239, DN-188, EN-81, FN-67, and NN-008, dated October 27, 1995.If missing or cracked adhesive or paint is detected at the lower surface root end fitting to doubler bonding line, accomplish the inspection in paragraph 3E of Part II of the Accomplishment Instructions of SIN HN-239, DN-188, EN-81, FN-67, and NN-008, dated October 27, 1995 using a piece of Mylar/viewfoil that is no thicker than .004-inch that is cut to a size between 0.9 inch and 1.1 inches wide and between 3.9 inches and 4.1 inches long. If any corner of the Mylar can be inserted between the lower surface root end fitting and doubler surface to a depth of 0.1 inch or greater, remove the blade from service and replace it with an airworthy blade.

(c) 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 itto the Manager, Los Angeles Aircraft Certification Office.

NOTE 2: 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.

(d) Special flight permits will not be issued.

(e) The inspections shall be done in accordance with McDonnell Douglas Helicopter Systems Service Information Notice (SIN) HN-239, DN-188, EN-81, FN-67, and NN-008, dated October 27, 1995. 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 McDonnell Douglas Helicopter Systems, Technical Publications, Bldg. 530/B111, 5000 E. McDowell Rd., Mesa, Arizona 85215-9797. Copies may be inspected at the FAA, Office of the Assistant Chief Counsel, 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.

(f) This amendment becomes effective May 29, 1996.

This amendment adopts a new AD that is applicable to MDHS Model 369, 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, and 500N helicopters. One accident occurred in August 1995 in which one blade separated from the rotor system while the helicopter was on the ground. Additionally, there were eight reports of blade cracking prior to the one accident, all of which were discovered during either routine inspections or inspections resulting from reported abnormal vibrations. Subsequent investigations revealed that bonding separation occurred between the lower surface root end fitting and the doubler. This condition, if not corrected, could result in failure of a blade resulting in separation of the blade and subsequent loss of control of the helicopter.

The FAA has reviewed McDonnell Douglas Helicopter Systems Service Information Notice No. HN-239, DN-188, EN-81, FN-67, and NN-008, dated October 27, 1995, which describes procedures for a one-time visual inspection of the blade root end for chordwise cracking and paint or sealant cracking between the lower surface root end fitting and the doubler, and then repetitive inspections at intervals of 100 hours time-in-service (TIS).

Since an unsafe condition has been identified that it is likely to exist or develop on other MDHS Model 369, 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, and 500N helicopters of the same type design, this AD is being issued to prevent failure of a blade at the root end due to fatigue cracking that initiates at the outboard bolt hole and usually travels in a chordwise direction. This AD requires, within 10 hours TIS after the effective date of this AD, a one-time visual inspection of each blade root end near the doubler paying particular attention to chordwise cracks and paint or sealant cracking or separation between the lower surface root end fitting and the doubler. Additionally, this AD requires repetitive visual inspections ofeach blade, at intervals not to exceed 100 hours TIS, for bond separation between the lower surface root end fitting and doubler paying particular attention to chordwise cracks. The actions are required to be accomplished in accordance with the service information notice described previously.

Due to the critical need to ensure the integrity of the main rotor system, and to comply with the requirements of this AD within 10 hours TIS, this rule must be issued immediately to correct an unsafe condition in the affected helicopters.

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 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. 96-SW-02-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 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 USC 106(g), 40113, 44701.

39.13 - [Amended]
2. Section 39.13 is amended by adding a new airworthiness directive to read as follows: