[Federal Register Volume 61, Number 198 (Thursday, October 10, 1996)]
[Rules and Regulations]
[Pages 53042-53044]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-25576]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-91-AD; Amendment 39-9777; AD 96-21-01]
RIN 2120-AA64


Airworthiness Directives; McDonnell Douglas Model DC-9-10, -20, -
30, -40, and -50 Series Airplanes and C-9 (Military) Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain McDonnell Douglas Model DC-9 series airplanes, 
that requires either replacement or modification of the hydraulic 
damper assembly. This amendment is prompted by reports indicating that 
insufficient damping of the hydraulic shimmy damper in the main landing 
gear (MLG) can allow high torsional vibration to occur. The actions 
specified by this AD are intended to prevent such vibration, which can 
damage the MLG assembly and lead to its collapse.

DATES: Effective November 14, 1996.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director

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of the Federal Register as of November 14, 1996.

ADDRESSES: The service information referenced in this AD may be 
obtained from McDonnell Douglas Corporation, 3855 Lakewood Boulevard, 
Long Beach, California 90846, Attention: Technical Publications 
Business Administration, Department C1-L51 (2-60). This information may 
be examined at the Federal Aviation Administration (FAA), Transport 
Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, 
Washington; or at the FAA, Transport Airplane Directorate, Los Angeles 
Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood, 
California; or at the Office of the Federal Register, 800 North Capitol 
Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Walter Eierman, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130L, FAA, Los Angeles Aircraft 
Certification Office, 3960 Paramount Boulevard, Lakewood, California 
90712; telephone (310) 627-5336; fax (310) 627-5210.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to certain McDonnell Douglas Model 
DC-9 series airplanes and C-9 (military) airplanes was published in the 
Federal Register on July 10, 1996 (61 FR 36307). That action proposed 
to require either replacing or modifying the hydraulic damper assembly.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Support for the Proposal

    Four commenters support the proposal.

Request to Withdraw Proposal

    One commenter contends that all reports of torsional vibration that 
resulted in torque link separations and/or breakage of the apex bolt 
occurred on Model DC-9-80 series airplanes. Given the number of Model 
DC-9 series airplanes in service and the number of landings logged on 
them without reports of torsional vibration caused by insufficient 
damping, the commenter considers the AD to be unwarranted. Further, 
this commenter states that the modification should not be mandated; 
operators should be allowed to accomplish it at their own discretion 
during a regularly scheduled maintenance visit.
    From these comments submitted, the FAA infers that the commenter 
requests that the proposed rule be withdrawn; in which case, the FAA 
does not concur. The commenter is incorrect in stating that the 
problems associated with torsional vibration have occurred only on 
Model DC-9-80 series airplanes. Such incidents and consequent damage 
have occurred on several Model DC-9 series airplanes as well. As 
detailed in the preamble to the notice, the MLG torque link broke on 
one airplane and, on another airplane, the nut was stripped off of the 
torque link apex bolt; both of these discrepancies were the result of 
insufficient damping of the MLG hydraulic shimmy damper. This fact 
alone affirms the need for this AD action.
    As for mandating the modification, the FAA points out that this AD 
provides operators with the option of either modifying the damper 
assembly or replacing it with an improved assembly. The compliance time 
of 24 months assures that operators will be able to schedule the 
accomplishment of either of these actions during a normal maintenance 
interval.

Conclusion

    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule as proposed.

Cost Impact

    There are approximately 878 Model DC-9 series airplanes and C-9 
(military) airplanes of the affected design in the worldwide fleet. The 
FAA estimates that 590 airplanes of U.S. registry will be affected by 
this AD.
    To accomplish the replacement will take approximately 5.9 work 
hours per airplane, at an average labor rate of $60 per work hour. 
Required parts will cost approximately $11,139 per airplane (two 
assemblies at $5,569 each). Based on these figures, the cost impact of 
the replacement action on U.S. operators is estimated to be $11,492 per 
airplane.
    To accomplish the required modification will take approximately 
10.9 work hours per airplane, at an average labor rate of $60 per work 
hour. Required parts will cost approximately $2,907 per airplane. Based 
on these figures, the cost impact of the modification action on U.S. 
operators is estimated to be $3,561 per airplane.
    Based on the figures discussed above, the cost impact of this AD on 
the U.S. fleet is between $2,100,990 and $6,780,280. These cost impact 
figures are based on assumptions that no operator has yet accomplished 
any of the requirements of this AD action, and that no operator would 
accomplish those actions in the future if this AD were not adopted.

Regulatory Impact

    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.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and (3) will not have a 
significant economic impact, positive or negative, on a substantial 
number of small entities under the criteria of the Regulatory 
Flexibility Act. A final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it 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. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

96-21-01 McDonnell Douglas: Amendment 39-9777. Docket 96-NM-91-AD.
    Applicability: Model DC-9-10, -20, -30, -40, and -50 series 
airplanes, and C-9 (military) airplanes; as listed in McDonnell 
Douglas Service Bulletin DC9-32-289, dated March 7, 1996; 
certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been

[[Page 53044]]

otherwise modified, altered, or repaired in the area subject to the 
requirements of this AD. For airplanes that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (b) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent high torsional vibration from occurring, which can 
damage the main landing gear (MLG) assembly and lead to its 
collapse, accomplish the following:
    (a) Within 24 months after the effective date of this AD, either 
replace or modify the MLG hydraulic damper assembly, in accordance 
with the procedures specified as either ``Option 1'' or ``Option 
2,'' respectively, in McDonnell Douglas Service Bulletin DC9-32-289, 
dated March 7, 1996.
    (b) 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 (ACO), FAA, Transport Airplane Directorate. Operators shall 
submit their requests through an appropriate FAA Principal 
Maintenance Inspector, who may add comments and then send it to the 
Manager, Los Angeles ACO.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Los Angeles ACO.

    (c) 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 airplane to a location where 
the requirements of this AD can be accomplished.
    (d) The actions shall be done in accordance with McDonnell 
Douglas Service Bulletin DC9-32-289, dated March 7, 1996. 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 Corporation, 3855 
Lakewood Boulevard, Long Beach, California 90846, Attention: 
Technical Publications Business Administration, Department C1-L51 
(2-60). Copies may be inspected at the FAA, Transport Airplane 
Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the 
FAA, Transport Airplane Directorate, Los Angeles Aircraft 
Certification Office, 3960 Paramount Boulevard, Lakewood, 
California; or at the Office of the Federal Register, 800 North 
Capitol Street, NW., suite 700, Washington, DC.
    (e) This amendment becomes effective on November 11, 1996.

    Issued in Renton, Washington, on September 30, 1996.
James V. Devany,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-25576 Filed 10-9-96; 8:45 am]
BILLING CODE 4910-13-U