[Federal Register Volume 62, Number 45 (Friday, March 7, 1997)]
[Proposed Rules]
[Pages 10490-10492]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-5573]


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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-NM-201-AD]
RIN 2120-AA64


Airworthiness Directives; McDonnell Douglas Model MD-90-30 
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 all McDonnell Douglas Model MD-90-
30 airplanes. This proposal would require revising the Airworthiness 
Limitations Section of the Instructions for Continued Airworthiness 
[MD-90-30 Airworthiness Limitations Instructions (ALI)]. The revision 
would incorporate certain compliance times for inspections to detect 
fatigue cracking of principal structural elements (PSE) and to add 
PSE's to the ALI. This proposal is prompted by analysis of data that 
identified reduced initial inspection thresholds, reduced repetitive 
inspection intervals for PSE's, and other PSE's to be added to the ALI. 
The actions specified by the proposed AD are intended to ensure that 
fatigue cracking of various PSE's are detected and corrected; such 
fatigue cracking could adversely affect the structural integrity of 
these airplanes.

DATES: Comments must be received by April 16, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 96-NM-201-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: Brent Bandley, Aerospace Engineer, 
Airframe Branch, ANM-120L, FAA, Los Angeles Aircraft Certification 
Office, 3960 Paramount Boulevard, Lakewood, California 90712; telephone 
(310) 627-5237; 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-201-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-201-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    In accordance with airworthiness standards requiring ``damage 
tolerance assessments'' [reference current section 1529 of parts 23, 
25, 27, and 29 of the Federal Aviation Regulations (FAR); section 4 of 
parts 33 and 35 of the FAR; section 82 of part 31 of the FAR; and the 
Appendices referenced in those sections], all products certificated to 
comply with those sections must have Instructions for Continued 
Airworthiness (or, for some products, maintenance manuals), that 
include an Airworthiness Limitations Section. That section must set 
forth:
    <bullet> mandatory replacement times for structural components,
    <bullet> structural inspection intervals, and

[[Page 10491]]

    <bullet> related approved structural inspection procedures 
necessary to show compliance with the damage-tolerance requirements.
    Compliance with the terms specified in the Airworthiness 
Limitations Sections is required by FAR sections 43.16 (for persons 
maintaining products) and 91.403 (for operators).
    As airplanes gain service experience, or as the result of post-
certification testing and evaluation, it may become necessary to add 
additional life limits or structural inspections in order to ensure the 
continued structural integrity of the airplane. The manufacturer may 
revise the Airworthiness Limitations Section to include new or more 
restrictive life limits and inspections. However, in order to require 
compliance with those revised life limits and/or inspection intervals, 
the FAA must engage in rulemaking.
    Because loss of structural integrity would result in an unsafe 
condition, it is appropriate to impose these requirements through the 
AD process.

Actions Taken by the Manufacturer

    McDonnell Douglas recently has completed extensive analyses and 
testing of fatigue cracking of Principal Structural Elements (PSE) on 
Model MD-90-30 airplanes, which included:
    <bullet> crack growth analysis,
    <bullet> service experience analysis,
    <bullet> crack growth testing,
    <bullet> fatigue testing, and
    <bullet> analysis of the effectiveness of applicable non-
destructive inspection techniques to detect cracking and other 
anomalies.
    The analyses and testing were similar to methods used to develop 
the initial MD-90 Airworthiness Limitations Instructions (ALI), 
Document No. MDC-94K9000, dated November 1994.
    The results of the testing and analyses demonstrated the need to 
revise certain inspections contained in the current ALI.

New Revisions of Airworthiness Limitations Instructions (ALI)

    The FAA has reviewed and approved MD-90 ALI, Revision 1, dated 
January 1995, and Revision 2, dated July 1996. These revisions describe 
specific reduced initial inspection thresholds and reduced repetitive 
inspection intervals for certain PSE's. They also include additional 
PSE's to be inspected.

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 operators to revise the MD-90 ALI to 
incorporate Revision 1, dated January 1995, and Revision 2, dated July 
1996.

Explanation of Action Taken by the FAA

    As stated previously, in order to require compliance with these 
inspection intervals and life limits, the FAA must engage in 
rulemaking, namely the issuance of an AD. For products certificated to 
comply with the referenced part 25 requirements, it is within the 
authority of the FAA to issue an AD requiring a revision to the 
Airworthiness Limitations Section that includes reduced life limits, or 
new or different structural inspection requirements. These revisions 
then are mandatory for operators under section 91.403(c) of the FAR, 
which prohibits operation of an airplane for which Airworthiness 
Limitations have been issued unless the inspection intervals specified 
in those limitations have been complied with.
    Once that document is revised, as required, and the AD has been 
fully complied with, the life limit or structural inspection change 
remains enforceable as a part of the Airworthiness Limitations. (This 
is analogous to AD's that require changes to the Limitations Section of 
the Airplane Flight Manual.)
    Requiring a revision of the Airworthiness Limitations, rather than 
requiring individual inspections, is advantageous for operators because 
it allows them to record AD compliance status only once--at the time 
they make the revision--rather than after every inspection. It also has 
the advantage of keeping all Airworthiness Limitations, whether imposed 
by original certification or by AD, in one place within the operator's 
maintenance program, thereby reducing the risk of non-compliance 
because of oversight or confusion.

Cost Impact

    There are approximately 15 Model MD-90 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 11 
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 actions, and that the average labor rate is $60 per work hour. 
Based on these figures, the cost impact of the proposed AD on U.S. 
operators is estimated to be $660, or $60 per airplane.
    The 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.

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-201-AD.

    Applicability: All Model MD-90-30 series airplanes, 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

[[Page 10492]]

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 (d) 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 ensure continued structural integrity of these airplanes, 
accomplish the following:
    (a) Within 180 days after the effective date of this AD, revise 
the Airworthiness Limitations Section of the Instructions for 
Continued Airworthiness [Airworthiness Limitations Instructions 
(ALI), McDonnell Douglas Report No. MDC-94K9000, dated November 
1994] to incorporate the Item, Location, and Inspection Interval of 
the following principal structural elements: This may be 
accomplished by inserting a copy of Revision 1 of the ALI, dated 
January 1995, or a copy of this AD into the ALI.

------------------------------------------------------------------------
                                                 Inspection interval (in
                                                        landings)       
          Item                  Location       -------------------------
                                                  Initial       Repeat  
------------------------------------------------------------------------
Item 53.30.02.3.........  Skin Panels, STA 237       60,000       11,000
                           to 1395 Fuselage                             
                           Skin in Constant                             
                           Section from                                 
                           Longeron 3 Left to                           
                           Longeron 3 Right.                            
Item 53.30.02.4.........  Skin Panels, STA 237       60,000       30,000
                           to 1395 Fuselage                             
                           Hoop Skin Splice in                          
                           Constant Section                             
                           from Longeron 5                              
                           Left to Longeron 5                           
                           Right.                                       
Item 54.10.04.1.........  Thrust Bulkhead,           15,000        4,500
                           Pylon--STA Yn                                
                           170.5--Rear Spar                             
                           and Engine Thrust                            
                           Support Fitting                              
                           (Upper and Lower).                           
------------------------------------------------------------------------

    (b) Within 180 days after the effective date of this AD, revise the 
Airworthiness Limitations Section of the Instructions for Continued 
Airworthiness [Airworthiness Limitations Instructions (ALI), McDonnell 
Douglas Report No. MDC-94K9000, dated November 1994] to incorporate the 
Item, Location, and Inspection Interval of the following principal 
structural elements: This may be accomplished by inserting a copy of 
Revision 2 to the ALI, dated July 1996, or a copy of this AD into the 
ALI.

                                                                        
------------------------------------------------------------------------
                                                 Inspection interval (in
                                                        landings)       
          Item                  Location       -------------------------
                                                  Initial       Repeat  
------------------------------------------------------------------------
Item 55.13.01.1.........  Plates/Skin--Upper         60,000        8,100
                           STA Xh 27.2 Left to                          
                           Xh 27.2 Right--                              
                           Upper Aft Skin                               
                           Plank with Integral                          
                           Stringers from Xh                            
                           7.234 to Xh 26.859.                          
------------------------------------------------------------------------

    (c) Except as provided in paragraph (d) of this AD: After the 
actions specified in paragraphs (a) and (b) of this AD have been 
accomplished, no alternative inspections or inspection intervals may be 
approved for the parts specified in paragraphs (a) and (b) of this AD.
    (d) 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 
Secs. 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 February 28, 1997.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-5573 Filed 3-6-97; 8:45 am]
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