[Federal Register Volume 62, Number 138 (Friday, July 18, 1997)]
[Rules and Regulations]
[Pages 38447-38448]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-18932]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 97-SW-02-AD; Amendment 39-10081; AD 97-15-08]
RIN 2120-AA64
Airworthiness Directives; McDonnell Douglas Helicopter Systems
Model 369D, E, F, FF, 500N, AH-6, and MH-6 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 (MDHS) Model
369D, E, F, FF, 500N, AH-6, and MH-6 helicopters. This action requires
replacement of certain transmission output drive gears (gears). This
amendment is prompted by several reports of spalled or fractured gear
teeth, most of which occurred during high-power or external-lift
operations. The actions specified in this AD are intended to prevent
failure of the gear, which could result in loss of main rotor control
and subsequent loss of control of the helicopter.
DATES: August 4, 1997.
Comments for inclusion in the Rules Docket must be received on or
before September 16, 1997.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Office of the Assistant Chief Counsel, Attention:
Rules Docket No. 97-SW-02-AD, 2601 Meacham Blvd., Room 663, Fort Worth,
Texas 76137.
FOR FURTHER INFORMATION CONTACT: Mr. Bruce Conze, Aerospace Engineer,
FAA, Los Angeles Aircraft Certification Office, Propulsion Branch, 3960
Paramount Blvd., Lakewood, California 90712, telephone (562) 627-5261,
fax (562) 627-5210.
SUPPLEMENTARY INFORMATION: This amendment adopts a new AD that is
applicable to MDHS Model 369D, E, F, FF, 500N, AH-6, and MH-6
helicopters, equipped with main rotor transmission, part number (P/N)
369D25100, that contain a gear, P/N 369D25127-11, having the following
serial numbers: serial number (S/N) 005570-0646 through S/N 005570-
0765, and S/N 005570-0876 through S/N 005570-0998. This action requires
replacement of gears having the affected serial numbers within a
specified number of hours time-in-service (TIS). There have been
several occurrences of spalled or fractured gear teeth in the last
seven years. Five of the occurrences involved fractured gear teeth, and
two involved spalling of the gear tooth face. All seven failures
occurred on helicopters having less than 1,000 hours TIS, with the
lowest being 467 hours TIS. Most of the damage and subsequent failures
have occurred during high-power or external-lift operations conducted
on military aircraft. This amendment is prompted by several reports of
spalled or fractured gear teeth, most of which occurred during high-
power or external-lift operations. Until 1996, all failures had
occurred only in military operations in which it was thought to be due
to overtorquing during maximum effort exercises. Since there is no
reporting requirement for military use, those failures were handled
under military maintenance and not reported. In 1996, a similar failure
occurred in New Zealand with an external load operator. This was the
first commercial failure and the first reported to the FAA by MDHS.
MDHS was allowed time to examine the failure and determine the cause.
Once it was determined that the failure was due to a quality control
problem, the affected lots were identified and MDHS issued service
information. Warping of the ring gear during carburizing heat treatment
and subsequent grinding through the hardened case results in a lowering
of the contact stress and fatigue resistance of the gear teeth. This
could result in fracture or loss of a gear tooth, which could lead to
jamming or binding of the drive system. The actions specified in this
AD are intended to prevent failure of the gear, which could result in
loss of main rotor control and subsequent loss of control of the
helicopter.
The FAA has reviewed McDonnell Douglas Helicopter Systems Service
Information Notice DN-189/EN-82/FN-69/NN-009, dated January 10, 1997,
which describes procedures for determining, through an inspection of
records or physical inspection, if a gear, P/N 369D25127-11, with
serial number (S/N) S/N 005570-0646 through S/N 005570-0765, or S/N
005570-0876 through S/N 005570-0998 is installed.
Since an unsafe condition has been identified that is likely to
exist or develop on other MDHS Model 369D, E, F, FF, 500N, AH-6, and
MH-6 helicopters of the same type design, this AD is being issued to
prevent failure of the gear, which could result in loss of main rotor
control and subsequent loss of control of the helicopter. This AD
requires an inspection to determine if an affected gear (based on the
gear's serial number) is installed, and if an affected gear is
installed, replacement of the gear with an airworthy gear.
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
[[Page 38448]]
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. 97-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, 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. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding a new airworthiness directive
to read as follows:
AD 97-15-08 McDonnell Douglas Helicopter Systems: Amendment 39-
10081. Docket No. 97-SW-02-AD.
Applicability: Model 369D, E, F, FF, 500N, AH-6, and MH-6
helicopters, with main rotor transmission, part number (P/N)
369D25100, installed, 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 (d) 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 the transmission output drive gear (gear),
part number P/N 369D25127-11, which could result in loss of main
rotor control and subsequent loss of control of the helicopter,
accomplish the following:
(a) Within the next 10 hours time-in-service (TIS) after the
effective date of this AD, determine through an inspection of
records, contact with the manufacturer, or using a bright light and
viewing through the open liquid level plug port, if the installed
gear serial number (S/N) is S/N 005570-0646 through S/N 005570-0765,
or S/N 005570-0876 through S/N 005570-0998.
(b) If the gear has an affected S/N, remove the gear and replace
it with an airworthy gear, that has a S/N other than the S/N's
listed in paragraph (a) of this AD, as follows:
(1) For helicopters equipped with a cargo hook assembly, with a
separate, permanently-maintained log of actual hours time-in-service
(TIS) of external load operation, remove and replace the gear within
the next 25 hours TIS for external load operations, or within the
next 400 hours TIS for non-external load operation, whichever comes
first.
(2) For helicopters equipped with a cargo hook assembly, with no
separate, permanently-maintained log of actual external load
operation, remove and replace the gear within the next 25 hours TIS
after the effective date of this AD. Owners/operators may begin
maintaining a separate permanent log of external load operations and
comply with the requirements of paragraph (b)(1) of this AD.
(3) For helicopters without cargo hook assemblies, remove and
replace the gear within the next 400 hours TIS after the effective
date of this AD.
(c) Replacement of the affected gear with an airworthy gear
having a S/N other than those S/N's listed in paragraph (a) of this
AD is considered 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 if approved by the Manager, Los Angeles Aircraft Certification
Office. Operators shall submit their requests through a FAA
Principal Maintenance Inspector, who may concur or comment and then
send it to 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.
(e) 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.
(f) This amendment becomes effective on August 4, 1997.
Issued in Fort Worth, Texas, on July 10, 1997.
Eric Bries,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 97-18932 Filed 7-17-97; 8:45 am]
BILLING CODE 4910-13-U
