[Federal Register Volume 64, Number 234 (Tuesday, December 7, 1999)]
[Proposed Rules]
[Pages 68302-68303]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-31679]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-329-AD]
RIN 2120-AA64


Airworthiness Directives; McDonnell Douglas Model MD-90-30 Series 
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 
MD-90-30 series airplanes. This proposal would require replacement of 
certain ground block screws with new screws; and retermination of the 
circuit ground wires of the electrical power control unit (EPCU) to 
separate grounding points. This proposal is prompted by reports of 
complete loss of the primary electrical power on an airplane during 
flight. The actions specified by the proposed AD are intended to 
prevent a loose electrical ground block of the circuit ground wires of 
the EPCU, which could result in complete loss of the primary electrical 
power of an airplane during flight.

DATES: Comments must be received by January 21, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-329-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 Boeing Commercial Aircraft Group, Long Beach Division, 
3855 Lakewood Boulevard, Long Beach, California 90846, Attention: 
Technical Publications Business Administration, Dept. 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: George Mabuni, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130L, FAA, Transport Airplane 
Directorate, Los Angeles Aircraft Certification Office, 3960 Paramount 
Boulevard, Lakewood, California 90712-4137; telephone (562) 627-5341; 
fax (562) 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 99-NM-329-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-114, Attention: Rules 
Docket No. 99-NM-329-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received reports of complete loss of the primary 
electrical power [including auxiliary power unit (APU)] on a Model MD-
90-30 series airplane during flight. The APU was started, but the APU 
generator would not power the electrical busses. This airplane also had 
an intermittent primary electrical power loss during landing and taxi. 
Investigation revealed an intermittent open circuit of the ground wires 
of the electrical power control unit (EPCU) due to a loose electrical 
ground block. This condition, if not corrected, could result in 
complete loss of the primary electrical power of the airplane during 
flight.

Explanation of Relevant Service Information

    The FAA has reviewed and approved McDonnell Douglas Alert Service 
Bulletin MD90-24A060, Revision 01, dated September 2, 1999, which 
describes procedures for replacement of the electrical ground block 
screws with new screws. Accomplishment of the action specified in the 
service bulletin and the retermination described below

[[Page 68303]]

are intended to adequately address the identified unsafe condition.

Explanation of FAA's Determination

    The FAA has determined that, in addition to the replacement 
described above, it is necessary to reterminate the circuit ground 
wires of the EPCU to separate grounding points to ensure that a single 
point failure does not occur.

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 accomplishment of the actions specified in 
the service bulletin described previously. The proposed AD also would 
require retermination of the circuit ground wires of the EPCU to 
separate grounding points to ensure that a single point failure does 
not occur. The retermination would be required to be accomplished in 
accordance with a method approved by the FAA.

Cost Impact

    There are approximately 104 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 21 airplanes of U.S. registry 
would be affected by this proposed AD, that it would take approximately 
1 work hour per airplane to accomplish the proposed replacement, and 
that the average labor rate is $60 per work hour. Parts would be 
procured from the operator's stock. Based on these figures, the cost 
impact of the replacement proposed by this AD on U.S. operators is 
estimated to be $1,260, or $60 per airplane.
    The FAA also estimates that it would take approximately 10 work 
hours per airplane to accomplish the proposed retermination of the 
circuit ground wires of the EPCU, and that the average labor rate is 
$60 per work hour. Parts would be procured from the operator's stock. 
Based on these figures, the cost impact of the retermination proposed 
by this AD on U.S. operators is estimated to be $12,600, or $600 per 
airplane.
    The cost impact figures discussed above 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 99-NM-329-AD.

    Applicability: Model MD-90-30 series airplanes, as listed in 
McDonnell Douglas Alert Service Bulletin MD90-24A060, Revision 01, 
dated September 2, 1999; certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
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 (c) 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 a loose electrical ground block of the circuit ground 
wires of the electrical power control unit (EPCU), which could 
result in complete loss of the primary electrical power of an 
airplane during flight, accomplish the following:

Replacement

    (a) Within 30 days after the effective of this AD, replace the 
electrical ground block screws with new screws in accordance with 
McDonnell Douglas Alert Service Bulletin MD90-24A060, Revision 01, 
dated September 2, 1999.

    Note 2: Accomplishment of the replacement of electrical ground 
block screws prior to the effective date of this AD in accordance 
with McDonnell Douglas Alert Service Bulletin MD90-24A060, dated 
July 28, 1999, is acceptable for compliance with the requirements of 
paragraph (a) of this AD.

Modification of the Electrical Power Control Unit

    (b) Within 12 months after the effective date of this AD, 
reterminate the circuit ground wires of the EPCU to separate 
grounding points to ensure that a single point failure does not 
occur, in accordance with a method approved by the Manager, Los 
Angeles Aircraft Certification Office (ACO), FAA, Transport Airplane 
Directorate.

Alternative Methods of Compliance

    (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 ACO. 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 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Los Angeles ACO.

Special Flight Permits

    (d) 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 December 1, 1999.
D. L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-31679 Filed 12-6-99; 8:45 am]
BILLING CODE 4910-13-P