[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:
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New tail rotor
Old tail rotor assembly No. assembly No.
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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
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(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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