[Federal Register Volume 60, Number 30 (Tuesday, February 14, 1995)]
[Rules and Regulations]
[Pages 8284-8286]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-3512]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 94-SW-21-AD; Amendment 39-9147; AD 95-03-11]


Airworthiness Directives; McDonnell Douglas Helicopter Systems 
and Hughes Helicopters, Inc. Model 369, OH-6A, and YOH-6A Series 
Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to McDonnell Douglas Helicopter Systems and Hughes 
Helicopters, Inc. Model 369, OH-6A, and YOH-6A series helicopters. This 
action requires initial and repetitive inspections of the tail rotor 
blade abrasion strip (abrasion strip), installation of stainless steel 
abrasion tape over the inboard end of the abrasion strip, and as a 
terminating action, installation of a tail rotor blade with a new-
design abrasion strip. This amendment is prompted by several incidents 
of riveted abrasion strips debonding and separating during flight, 
resulting in severe out-of-balance conditions and subsequent separation 
of [[Page 8285]] the tail rotor gearbox from the helicopter. The 
actions specified in this AD are intended to prevent loss of the 
abrasion strip, separation of a tail rotor blade, separation of the 
tail rotor gearbox, and subsequent loss of control of the helicopter.

DATES: Effective March 1, 1995.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 1, 1995.
    Comments for inclusion in the Rules Docket must be received on or 
before April 17, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Office of the Assistant Chief Counsel, Attention: 
Rules Docket No. 94-SW-21-AD, 2601 Meacham Blvd., Room 663, Fort Worth, 
Texas 76137.
    The service information referenced in this AD may be obtained from 
McDonnell Douglas Helicopter Systems, Technical Publications, Bldg. 
530/B111, 5000 E. McDowell Road, Mesa, Arizona 85205-9797. This 
information may be examined 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.

FOR FURTHER INFORMATION CONTACT: Mr. Brent Bandley, Aerospace Engineer, 
Los Angeles Aircraft Certification Office, FAA, Transport Airplane 
Directorate, 3960 Paramount Blvd., Lakewood, California 90712, 
telephone (310) 627-5237, fax (310) 627-5210.

SUPPLEMENTARY INFORMATION: On August 30, 1994, the FAA issued AD 94-18-
08, Amendment 39-9021 (59 FR 46163, September 7, 1994) to require 
installation of abrasion strip rivets (rivets) within 25 hours time-in-
service or 7 calendar days, whichever occurs first, on certain tail 
rotor blades. Also required are owner/operator checks of the abrasion 
strips for evidence of debonding along the abrasion strip bond line 
before the first flight of each day; a dye-penetrant and tap-test 
inspection to ensure the abrasion strip is secure if the owner/operator 
checks reveal evidence of debonding; and, if debonding is confirmed, 
replacement of the tail rotor blade with an airworthy blade that has 
been modified with the installation of rivets. Since the issuance of 
that AD, there have been several incidents of riveted tail rotor blade 
abrasion strips debonding and separating during flight, resulting in 
severe out-of-balance conditions, and subsequent separation of the tail 
rotor gearbox from the helicopter. Based on these incidents, the FAA 
has determined that riveting the abrasion strips alone does not create 
a fail-safe design. An analysis has shown that the debonding starts at 
the inboard end of the abrasion strip. This condition, if not 
corrected, could result in loss of the abrasion strip, separation of a 
tail rotor blade, separation of the tail rotor gearbox, and subsequent 
loss of control of the helicopter. Therefore, installation of stainless 
steel abrasion tape over the inboard end of the abrasion strips within 
25 hours time-in-service (TIS) or 90 calendar days, whichever occurs 
first, and thereafter, at intervals not to exceed 100 hours TIS, is 
necessary to prevent debonding of the abrasion strip from the tail 
rotor and to ensure the integrity of the helicopter. However, owners 
and operators must install abrasion strip rivets as required by AD 94-
18-08 prior to installing the stainless steel abrasion tape. 
Additionally, within 1,000 hours TIS, installation of a tail rotor 
blade with a new-design abrasion strip is required.
    The FAA has reviewed McDonnell Douglas Helicopter Systems Service 
Information Notice HN-238, DN-187, EN-80, FN-66, dated October 26, 
1994, which describes procedures for inspection of the abrasion strips 
for separation or voids and replacement if separation or voids are 
evident; installation of 304 stainless steel abrasion tape (.0027-inch 
thick) over the inboard end of the abrasion strips; and replacement of 
existing tail rotor blades with tail rotor blades equipped with new-
design abrasion strips.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other McDonnell Douglas Helicopter Systems and 
Hughes Helicopters, Inc. Model 369, OH-6A, and YOH-6A series 
helicopters of the same type design, this AD is being issued to prevent 
loss of the abrasion strip, separation of a tail rotor blade, 
separation of the tail rotor gearbox, and subsequent loss of control of 
the helicopter. This AD requires initial and repetitive inspections of 
the abrasion strip, installation of stainless steel abrasion tape over 
the inboard end of the abrasion strip, and as a terminating action, 
installation of a tail rotor blade with a new-design abrasion strip. 
Due to the criticality of the abrasion strip and maintaining a balanced 
tail rotor system, and the short compliance time for installation of 
the stainless steel abrasion tape, this rule must be issued immediately 
to correct an unsafe condition. The actions are required to be 
accomplished in accordance with the service bulletin 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 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. 94-SW-21-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 [[Page 8286]] 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.


Sec. 39.13  [Amended]

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

95-03-11  McDonnell Douglas Helicopter Systems and Hughes 
Helicopters, Inc.: Amendment 39-9147. Docket No. 94-SW-21-AD.
    Applicability: Model 369, OH-6A, and YOH-6A series helicopters, 
with tail rotor blade assemblies, part number (P/N) 369A1613-7, 
369A1613-503, 369A1613-505, 369A1613-509, 369D21606, 369D21606-509, 
369D21613-11, 369D21613-31, 369D21613-41, 369D21613-51, 369D21613-
71, 369D21615, 369D21615-21, 369D21615-41, or 421-088, installed, 
certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent loss of the abrasion strip, separation of a tail 
rotor blade, separation of the tail rotor gearbox, and subsequent 
loss of control of the helicopter, accomplish the following:
    (a) Within 25 hours time-in-service (TIS) or 90 calendar days, 
whichever occurs first, and thereafter, at intervals not to exceed 
100 hours TIS, inspect the tail rotor blade abrasion strip for 
debonding from the tail rotor blade. Prior to conducting the 
repetitive inspections, remove any abrasion tape from the tail rotor 
blade.
    (1) If the inspection reveals debonding, replace the tail rotor 
blade with an airworthy blade that has been modified by an 
installation of rivets, and install 304 stainless steel abrasion 
tape (.0027-inch thick) over the inboard end of the abrasion strip 
in accordance with steps B through H of Part I of the Accomplishment 
Instructions of McDonnell Douglas Helicopter Systems Service 
Information Notice (SIN) HN-238, DN-187, EN-80, FN-66, dated October 
26, 1994.
    (2) If the inspection reveals no debonding, install 304 
stainless steel abrasion tape (.0027-inch thick) over the inboard 
end of the abrasion strip in accordance with steps B through H of 
Part I of the Accomplishment Instructions of McDonnell Douglas 
Helicopter Systems SIN HN-238, DN-187, EN-80, FN-66, dated October 
26, 1994.
    (b) Within 1,000 hours TIS after the effective date of this AD, 
replace the affected tail rotor blades in shipsets with tail rotor 
blades that contain the new-design abrasion strips in accordance 
with Part II of the Accomplishment Instructions of SIN HN-238, DN-
187, EN-80, FN-66, dated October 26, 1994. Once the new-design 
abrasion strips are installed on the tail rotor blades, the tail 
rotor assembly P/N changes as follows:

------------------------------------------------------------------------
                                                        New tail rotor  
             Old tail rotor assembly No.                 assembly No.   
------------------------------------------------------------------------
369A1613-7..........................................        369A1613-11 
369A1613-503........................................       369A1613-507 
369A1613-505........................................       369A1613-507 
369A1613-509........................................       369A1613-507 
369D21606...........................................      369D21606-511 
369D21606-509.......................................      369D21606-511 
369D21613-11........................................      369D21613-11N 
369D21613-31........................................      369D21613-31N 
369D21613-41........................................       369D21613-61 
369D21613-51........................................       369D21613-61 
369D21613-71........................................       369D21613-61 
369D21615...........................................        369D21615-N 
369D21615-21........................................       369D21615-31 
369D21615-41........................................       369D21615-31 
 421-088............................................         421-088-11 
------------------------------------------------------------------------

    (c) Installation of tail rotor blades with new-design abrasion 
strips installed in accordance with Part II of the Accomplishment 
Instructions of SIN HN-238, DN-187, EN-80, FN-66, dated October 26, 
1994, constitutes a terminating action for the requirements 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 when 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: 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 
Secs. 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.
    (f) The modification and replacement shall be done in accordance 
with McDonnell Douglas Helicopter Systems Service Information Notice 
HN-238, DN-187, EN-80, FN-66, dated October 26, 1994. 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 
Road, Mesa, Arizona 85205-9797. 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.
    (g) This amendment becomes effective on March 1, 1995.

    Issued in Fort Worth, Texas, on February 6, 1995.
Eric Bries,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 95-3512 Filed 2-13-95; 8:45 am]
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