[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]
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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).
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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-9-80 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
