[Federal Register Volume 59, Number 143 (Wednesday, July 27, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-18279]

[[Page Unknown]]

[Federal Register: July 27, 1994]


14 CFR Part 39

[Docket No. 94-NM-78-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 modification of the power transfer unit (PTU). This proposal is 
prompted by reports of fatigue cracks found in the drain port housings 
of the PTU's on several airplanes. The actions specified by the 
proposed AD are intended to prevent failure of the PTU housing due to 
fatigue cracking, which could result in the loss of both hydraulic 
systems (until the PTU is shut off).

DATES: Comments must be received by September 9, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 94-NM-78-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 
    The service information referenced in the proposed rule may be 
obtained from McDonnell Douglas Corporation, P.O. Box 1771, Long Beach, 
California 90801-1771, Attention: business Unit Manager, Technical 
Administrative support, Dept. L51, M.C. 2-98. This information may be 
examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, 
SW., Renton, Washington; or at the FAA, Los Angeles Aircraft 
Certification Office, Transport Airplane Directorate, 3229 East Spring 
Street, Long Beach, California.

FOR FURTHER INFORMATION CONTACT: Walter Eierman, Systems and Equipment 
Branch, ANM-131L, FAA, Transport Airplane Directorate, Los Angeles ACO, 
3229 East Spring Street, Long Beach, California 90806-2425; telephone 
(310) 988-5336; fax (310) 988-5210. 
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 94-NM-78-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. 94-NM-78-AD, 1601 Lind Avenue, SW., Renton, Washington 
    The FAA has received reports of cracked drain port housings found 
on the power transfer units (PTU) installed on five McDonnell Douglas 
Model DC-9-80 series airplanes. In one incident, failure of the housing 
resulted in the loss of both hydraulic systems, which caused the 
airplane to depart from the runway during taxi due to the loss of 
braking and nose landing gear steering.
    Investigation has revealed that the cause of the cracking is 
attributed to fatigue. Further analysis of the hardware has indicated 
that the center housing and drain port housing can crack before the 
design life of the PTU has been reached. This condition, if not 
corrected, could lead to the failure of the housings associated with 
the PTU, which in turn could result in the loss of both hydraulic 
systems (until the PTU is shut off).
    The FAA has reviewed and approved McDonnell Douglas Service 
Bulletin 29-53, Revision 1, dated April 21, 1994, that describes 
procedures for modification of the center housing and drain port 
housing of the PTU. This modification entails replacing the currently 
installed cast aluminum housings with wrought aluminum housings, and 
reidentifying the part number of the PTU. Such modification will ensure 
that the housings meet the PTU design life requirements.

    (Note: This service bulletin references Allied Signal Service 
Bulletin 4100310-29-0031, Revision 3, dated April 8, 1994, for 
detailed modification instructions.)

    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 modification of the center housing and drain 
port housing of the PTU. The actions would be required to be 
accomplished in accordance with the McDonnell Douglas service bulletin 
described previously.
    This proposed AD would not be applicable to airplanes that are 
equipped with Vickers PV3-160 engine driven pumps. The FAA finds that 
this type of pump provides a pressurized flow of 21 gallons per minute 
and, in the event of a PTU crack or failure, that rate of flow would be 
adequate to continue pressurizing the affected hydraulic system.
    There are approximately 1,074 Model DC-9-80 series airplanes and 
Model MD-88 airplanes of the affected design in the worldwide fleet. 
The FAA estimates that 578 airplanes of U.S. registry would be affected 
by this proposed AD, that it would take approximately 2 work hours per 
airplane to accomplish the proposed actions, and that the average labor 
rate is $55 per work hour. Required parts would cost approximately 
$2,912 per airplane. Based on these figures, the total cost impact of 
the proposed AD on U.S. operators is estimated to be $1,746,716, or 
$3,022 per airplane.
    The total cost impact figure discussed above 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 


    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.

Sec. 39.13  [Amended]

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

McDonnell Douglas: Docket 94-NM-78-AD.

    Applicability: Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 
(MD-83), DC-9-84 (MD-84), and DC-9-87 (MD-87) series airplanes, and 
Model MD-88 airplanes; as listed in McDonnell Douglas Service 
Bulletin 29-53, Revision 1, dated April 21, 1994; excluding 
airplanes equipped with Vickers PV3-160 Engine Driven Pumps; 
certificated in any category.
    Compliance: Required as indicated, unless accomplished 
    To prevent loss of both hydraulic systems due to the failure of 
the housings of the power transfer unit (PTU), accomplish the 
    (a) Prior to or upon the accumulation of 14,300 flight cycles on 
the PTU, or within 9 months after the effective date of this AD, 
whichever occurs later, modify the PTU assembly, part number 
4100310, in accordance with McDonnell Douglas Service Bulletin 29-
53, Revision 1, dated April 21, 1994.
    (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: 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 
Sec. Sec.  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 20, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
[FR Doc. 94-18279 Filed 7-26-94; 8:45 am]