[Federal Register Volume 60, Number 186 (Tuesday, September 26, 1995)]
[Proposed Rules]
[Pages 49523-49525]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-23808]



=======================================================================
-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95-NM-91-AD]


Airworthiness Directives; McDonnell Douglas Model DC-9-80 Series 
Airplanes and Model MD-88 Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain McDonnell Douglas Model 
DC-9-80 series airplanes and Model MD-88 airplanes. This proposal would 
require installation of hydraulic line restrictors in the main landing 
gear (MLG), and modification of the hydraulic damper assembly of the 
MLG. This proposal is prompted by reports of vibration occurring in the 
MLG during landing; in some cases, such vibration has led to the 
collapse of the MLG. The actions specified by the proposed AD are 
intended to prevent incidents of vibration in the MLG, which can 
adversely affect the integrity of the MLG.

DATES: Comments must be received by November 21, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 95-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.

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 95-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. 

[[Page 49524]]
95-NM-91-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

    The FAA has received several reports from operators of McDonnell 
Douglas Model DC-9-80 series airplanes who have experienced incidents 
of severe vibration of the main landing gear (MLG) when brakes are 
applied during landing. The vibration resulted in separation of the 
torque link and breakage at the apex joint. In three of these 
incidents, the MLG collapsed. Investigation revealed that the collapse 
resulted from torsional vibration in the MLG, which was induced by 
interaction between the landing gear and the brake antiskid system.
    The FAA also has received a report indicating that a MLG failed due 
to fatigue failure of the MLG shock strut cylinder. Investigation 
revealed that a fore and aft vibration of the MLG can occur when brakes 
are applied. As in the other incidents, this vibration is caused by the 
interaction of the landing gear and the brake antiskid system. Such 
vibration causes higher than expected stress levels in the MLG shock 
strut cylinder, and can lead to the subsequent fatigue failure of the 
cylinder.
    These conditions, if not corrected, can adversely affect the 
integrity of the MLG.
    The FAA has reviewed and approved the following McDonnell Douglas 
Service Bulletins:
    1. Service Bulletin MD80-32-276, dated March 31, 1995: This 
document describes procedures for the installation of brake line 
restrictors on airplanes not currently equipped with them. This 
installation will minimize the possibility of both the torsional and 
the fore and aft vibration that results from the interaction of the 
landing gear and the antiskid system.
    2. Service Bulletin MD80-32-278, dated March 31, 1995: This 
document describes procedures to replace and modify the hydraulic 
damper assembly. The replacement or modification entails removing the 
shims located between the cap and damper assembly housing; increasing 
the torque on the damper housing assembly bolts; and replacing or 
modifying the damper assembly components to increase the volume of 
fluid passing between the two damper chambers. This modification 
significantly increases the damping capability of this unit and 
consequently reduces the possibility of torsional vibration in the MLG 
assembly.
    Accomplishing the actions described in these two service bulletins 
will have a combined effect to:
    1. substantially reduce the amount of vibration in the MLG,
    2. improve the effectiveness of the high energy damper, and
    3. minimize the possibility of incidents of extreme vibration on 
these airplanes, which can lead to damage to the MLG and the airframe.
    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 installation of MLG brake system hydraulic 
line restrictors, and modification or replacement of the MLG hydraulic 
damper assembly. The actions would be required to be accomplished in 
accordance with the two service bulletins described previously.
    There are approximately 1,100 Model DC-9-80 series airplanes and 
Model MD-88 airplanes of the affected design in the worldwide fleet. 
The FAA estimates that 600 airplanes of U.S. registry would be affected 
by this proposed AD.
    Accomplishment of the installation of the brake line restrictor, as 
described in McDonnell Douglas Service Bulletin MD80-32-276, would take 
approximately 4 work hours per airplane to accomplish the proposed 
actions, and that the average labor rate is $60 per work hour. Required 
parts would cost approximately $928 per airplane. Based on these 
figures, the total cost impact of this proposed installation action on 
U.S. operators is estimated to be $700,800, or $1,168 per airplane.
    Accomplishment of the modification of the hydraulic damper 
assembly, as described in McDonnell Douglas Service Bulletin A32-278, 
would take approximately 6 work hours per airplane to accomplish the 
proposed actions, and that the average labor rate is $60 per work hour. 
Required parts would cost approximately $4,000 per airplane. Based on 
these figures, the total cost impact of this modification action on 
U.S. operators is estimated to be $2,616,000, or $4,360 per airplane.
    Based on the figures discussed above, the FAA estimates that the 
total cost impact of this proposed AD on U.S. operators would be 
$3,316,800, or $5,528 per airplane. This total cost impact figure is 
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.
    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 USC 106(g), 40101, 40113, 44701.


Sec. 39.13  [Amended]

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

McDonnell Douglas: Docket 95-NM-91-AD.

    Applicability: Model DC-9-81 (MD-81), -82 (MD-82), -83 (MD-83), 
and -87 (MD-87) series airplanes, and Model MD-88 airplanes; 
certificated in any category; and listed in the following McDonnell 
Douglas Service Bulletins:

McDonnell Douglas MD-80 Service Bulletin MD80-32-276, dated March 
31, 1995; and
McDonnell Douglas MD-80 Service Bulletin MD80-32-278, dated March 
31, 1995.

    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 use the authority 

[[Page 49525]]
provided in paragraph (c) of this AD 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 airplane from the applicability of this AD.

    Compliance: Required as indicated, unless accomplished 
previously.
    To reduce the possibility of vibration in the main landing gear 
(MLG) that can adversely affect its integrity, accomplish the 
following:
    (a) For airplanes listed in McDonnell Douglas MD-80 Service 
Bulletin MD80-32-276, dated March 31, 1995, that have not been 
previously modified (installation of brake line restrictors) in 
accordance with McDonnell Douglas MD-80 Service Bulletin 32-246: 
Within 9 months after the effective date of this AD, install 
filtered restrictors in the MLG hydraulic brake system in accordance 
with McDonnell Douglas MD-80 Service Bulletin MD80-32-276, dated 
March 31, 1995.
    (b) For airplanes listed in McDonnell Douglas MD-80 Service 
Bulletin MD80-32-278, dated March 31, 1995: Within 36 months after 
the effective date of this AD, modify the hydraulic damper assembly 
(by removing shims, increasing bolt torque, and incorporating 
changes to increase the volume of fluid passing between the two 
damper chambers) in accordance with McDonnell Douglas MD-80 Service 
Bulletin MD80-32-278, dated March 31, 1995 .
    (c) 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.

    (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 airplane to a location where 
the requirements of this AD can be accomplished.

    Issued in Renton, Washington, on September 20, 1995.
S.R. Miller,


Acting Manager, Transport Airplane Directorate, Aircraft 
Certification Service.

[FR Doc. 95-23808 Filed 9-25-95; 8:45 am]
BILLING CODE 4910-13-U