[Federal Register Volume 61, Number 133 (Wednesday, July 10, 1996)]
[Proposed Rules]
[Pages 36307-36308]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-17537]


 ========================================================================
 Proposed Rules
                                                 Federal Register
 ________________________________________________________________________
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 This section of the FEDERAL REGISTER contains notices to the public of 
 the proposed issuance of rules and regulations. The purpose of these 
 notices is to give interested persons an opportunity to participate in 
 the rule making prior to the adoption of the final rules.
 
 ========================================================================
 

  Federal Register / Vol. 61, No. 133 / Wednesday, July 10, 1996 / 
Proposed Rules  

[[Page 36307]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-NM-91-AD]
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: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain McDonnell Douglas Model 
DC-9 series airplanes and C-9 (military) airplanes. This proposal would 
require either replacement or modification of the hydraulic damper 
assembly. This proposal 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 the proposed AD are intended to prevent such vibration, 
which can damage the MLG assembly and lead to its collapse.

DATES: Comments must be received by August 19, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 96-NM-91-AD, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056. Comments may be inspected at this location 
between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal 
holidays. -
    The service information referenced in the proposed rule 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 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.

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:

Comments Invited -

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received. -
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket. -
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 96-NM-91-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs -

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-103, Attention: Rules 
Docket No. 96-NM-91-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion -

    The FAA has received several reports of incidents in which 
components of the main landing gear (MLG) on McDonnell Douglas Model 
DC-9 series airplanes have been damaged. In one incident, the MLG 
torque link was broken; in another incident, the nut was stripped off 
of the torque link apex bolt. Investigation has revealed that, under 
maximum loading of the hydraulic damper assembly, which occurs during 
landing, the metal-to-metal seal between the cap and damper assembly 
housing can leak (hydraulic fluid) internally. Such leakage can reduce 
the effectiveness of the damper. -
    Insufficient damping of the MLG hydraulic shimmy damper allows 
torsional vibration to occur in the MLG. High torsional vibration can 
damage the MLG, which can result in collapse of the MLG and can cause 
additional damage to other parts of the airplane.

Explanation of Relevant Service Information -

    The FAA has reviewed and approved McDonnell Douglas Service 
Bulletin DC9-32-289, dated March 7, 1996, which describes procedures 
for either replacing or modifying the hydraulic damper assembly. The 
replacement entails replacing the current assembly with an improved 
assembly. The modification involves removing shims located between the 
cap and damper assembly housing, increasing the torque on damper 
housing assembly bolts, and incorporating changes to increase the 
volume of fluid passing between the two damper chambers. These actions 
will enhance the performance of the shimmy damper and reduce the 
potential for torsional vibration in the MLG.

Explanation of Requirements of Proposed Rule -

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require either replacing or modifying the hydraulic 
damper assembly. The actions would be required to be accomplished in 
accordance with the service bulletin described previously.

[[Page 36308]]

Other Relevant Rulemaking -

    The FAA previously issued AD 96-01-09, amendment 39-9485 (61 FR 
2407, January 26, 1996), which addresses a similar problem found on 
McDonnell Douglas Model DC-9-80 series airplanes and Model MD-88 
airplanes.

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 would be affected by 
this proposed AD. -
    To accomplish the proposed replacement would take approximately 5.9 
work hours per airplane, at an average labor rate of $60 per work hour. 
Required parts would cost approximately $11,139 per airplane (two 
assemblies at $5,569 each). Based on these figures, the cost impact of 
the proposed replacement action on U.S. operators is estimated to be 
$11,492 per airplane. -
    To accomplish the proposed modification would take approximately 
10.9 work hours per airplane, at an average labor rate of $60 per work 
hour. Required parts would cost approximately $2,907 per airplane. 
Based on these figures, the cost impact of the proposed 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 
proposed AD on the U.S. fleet would be 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 proposed 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 proposed herein would 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment. -
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, 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 copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting 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.

The Proposed Amendment -

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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:

McDonnell Douglas: 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 
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.

    Issued in Renton, Washington, on July 3, 1996.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.

[FR Doc. 96-17537 Filed 7-9-96; 8:45 am]

BILLING CODE 4910-13-U