AD 94-18-08

This amendment supersedes an existing airworthiness directive (AD), applicable to McDonnell Douglas Helicopter Company and Hughes Helicopters, Inc. Model 369, 369A (OH-6A), 369D, E, F, FF, H, HE, HS, and HM series helicopters, that requires daily preflight checks and 100 hours time-in-service (TIS) inspections for tail rotor blade abrasion strip (abrasion strip) debonding until abrasion strip rivets (rivets) are installed. This amendment also supersedes a Priority Letter AD that currently requires installation of rivets, corrects tail rotor blade part numbers listed in the previous AD, and retains the daily preflight checks of the previous AD until rivets are installed to secure the abrasion strip. This AD provides a terminating action for the abrasion strip debonding and also seeks to clear up any confusion among operators caused by having a published AD and a Priority Letter that are applicable to the same helicopter part. This AD replaces both of those documents. Thisamendment is prompted by an accident resulting from the separation of an abrasion strip from a tail rotor blade and subsequent tail rotor separation. The actions specified by this AD are intended to prevent loss of the abrasion strip, separation of the tail rotor, and subsequent loss of control of the helicopter.

Final rule; request for comments

94-18-08 MCDONNELL DOUGLAS HELICOPTER COMPANY (MDHC) and HUGHES HELICOPTERS, INC.: Amendment 39-9021. Docket Number 93-SW-03-AD. Supersedes Priority Letter AD 92-22-14, issued October 16, 1992, and AD 92-02-15, Amendment 39-8151.

Applicability: Model 369, 369A (OH-6A), 369D, E, F, FF, H, HE, HS, and HM series helicopters, equipped with the following tail rotor blades with bonded tail rotor abrasion strips (abrasion strips) installed, but without abrasion strip rivets (rivets) installed as described in paragraph (c) of this AD: part numbers (P/N) 421-088; 369A1613-7, -503, -505; 369D21606; 369D21613-11, -31, -41, -51; 369D21615, -21; or 369A1613-3M; and any of these P/N with a suffix (such as the letters "M" or "M-STC") added to the dash numbers, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent the loss of abrasion strips, separation of the tail rotor, and subsequent loss of control of the helicopter, accomplish the following:

(a) Before the first flight of each day, until two rivets are installed as required by paragraph (c) of this AD, visually check each abrasion strip for any evidence of debonding along the entire abrasion strip bond line. This visual check may be performed by the owner/operator holding at least a private pilot certificate and must be entered into the aircraft records showing compliance with this AD in accordance with sections 43.11 and 91.417 (a)(2)(v) of the Federal Aviation Regulations.

(b) If performance of the visual check required by paragraph (a) results in evidence of debonding, conduct the following inspections before further flight:

(1) Remove the tail rotor blade from the helicopter, and perform a dye-penetrant and a tap-test inspection in accordance with the applicable helicopter maintenance manual to ensure that the abrasion strip is secure.

NOTE: MDHC Service Information Notice HN-197.2, DN-130.2, EN-19.2, and FN-17.1, dated March 23, 1987, contains additional information on the inspections required by paragraph (b).

(2) If debonding is confirmed, remove the tail rotor blade from service and replace it with an airworthy blade, which has been modified by the installation of rivets.

(c) Within 25 hours time-in-service or on or before 7 calendar days after the effective date of this AD, whichever comes first:

(1) Inspect the tail rotor blades in accordance with paragraph (b)(1) of this AD, and if no evidence of debonding exists, install rivets in accordance with Part II of MDHC Service Information Notice (SIN) HN-232, DN-179, EN-70 and FN-57, dated September 27, 1991.

(2) If evidence of debonding exists, remove the blade from service and replace it with an airworthy blade, which has been modified by the installation of rivets, prior to further flight.

(d) Installation of the abrasion strip rivets in accordance with MDHC SIN HN-232, DN-179, EN-70, and FN-57, dated September 27, 1991, constitutes a terminating action for the requirements of this AD.

(e) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used when approved by the Manager, Los Angeles Aircraft Certification Office, FAA, Northwest Mountain Region, 3229 E. Spring Street, Long Beach, California 90806-2425. 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: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Manager, Los Angeles Aircraft Certification Office.

(f) 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, provided there is no evidence of debonding of the abrasion strip at any point along the entire abrasion strip bond line of the tail rotor blades.

(g) The inspection, removal, modification, and replacement, if necessary, shall be done in accordance with McDonnell Douglas Helicopter Corporation (MDHC) SIN HN-232, DN-179, EN-70, and FN-57, dated September 27, 1991. 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 MDHC Technical Publications, Bldg. 530/B111, 5000 E. McDowell Road, Mesa, Arizona 85205-9797. Copies may be inspected at the FAA, Office the Assistant Chief Counsel, 2601 Meacham Boulevard, Room 663, Fort Worth, Texas; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(h) This amendment becomes effective on September 27, 1994.

On December 31, 1991, the FAA issued AD 92-02-15, Amendment 39-8151 (57 FR 5379, February 14, 1992), to require daily preflight checks and 100 hours TIS repetitive inspections for abrasion strip debonding until rivets are installed. That AD requires installation of the rivets within 300 hours TIS.

As a result of a more recent helicopter accident involving the separation of an abrasion strip, on October 16, 1992, the FAA issued Priority Letter (PL) AD 92-22-14 that superseded the existing AD 92-02-15. The PL AD corrects certain tail rotor blade part numbers as listed in AD 92-02-15 and retains the daily preflight checks of the previous AD 92-02-15 until rivets are installed. The PL AD further requires installation of the rivets within 25 hours TIS or within 7 days, whichever comes first.

Both AD 92-02-15, issued December 31, 1991 and the PL AD 92-22-14, issued October 16, 1992, require a visual check for evidence of debonding before the first flight of each day. However, AD 92-02-15 requires installation of rivets within 300 hours TIS while PL AD 92-22-14 requires installation of the rivets within 25 hours TIS or on or before 7 days after the effective date of that AD. Both of these ADs require the same corrective action but have different compliance times. Additionally, the PL AD did not specify whether the 7-day compliance time was in terms of "work" days or "calendar" days. As a result of having two ADs that require the same corrective action with only differing compliance times, and additionally failing to specifically describe the type of compliance day as that term was used in the PL AD, operators may be confused about when compliance is required. Such confusion may lead an operator to inadvertently fail to comply with the necessary safety requirements for these rotorcraft and result in an unsafe condition. Therefore, due to the criticality of the abrasion strip, the short compliance times, and the possible confusion as a result of having two effective ADs that require the same corrective action with one containing a potentially confusing compliance time, this rule must be issued immediately to correct an unsafe condition.

In addition to correcting the unsafe conditions described, this AD also provides that installation of the rivets to secure the abrasion strip constitutes terminating action for the requirements of this AD.

The checks required by this AD before the first flight of each day may be performed by an owner/operator (pilot) but must be entered into the aircraft records showing compliance with this AD in accordance with sections 43.11 and 91.417 (a)(2)(v) of the Federal Aviation Regulations. This AD allows a pilot to perform this check because it involves only a visual check for debonding of the abrasion strip from the tail rotor blade and is required only until rivets are installed. This check can be performed equally well by a pilot or a mechanic. It involves checking items similar to those items that a pilot checks during a preflight. Safety does not require that this check be performed by a mechanic before the first flight of each day. The AD does require that a mechanic inspect the tail rotor blades within 25 hours TIS or within 7 calendar days, whichever occurs first.

Since an unsafe condition has been identified that is likely to exist or develop on other helicopters of the same type design, this AD supersedes the PL, AD 92-22-14, and AD 92-02-15 to require more prompt installation of rivets, to specify that the 7 days compliance time refers to calendar days, and to correct tail rotor blade part numbers as listed in AD 92-02-15. The daily preflight checks required by paragraph (a) of AD 92-02-15 are retained until rivets are installed. The actions are required to be accomplished in accordance with Part II of McDonnell Douglas Helicopter Company Service Information Notice HN-232, DN-179, EN-70 and FN-57, dated September 27, 1991.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 isextremely 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 Number 93-SW-03-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 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.

39.13 - [AMENDED]
2. Section 39.13 is amended by removing Amendment 39-8151 (57 FR 5379, February 14, 1992), and by adding a new airworthiness directive (AD), Amendment 39-9021, to read as follows: