Airworthiness Directives; Boeing Model 757 Series Airplanes

[Federal Register Volume 64, Number 18 (Thursday, January 28, 1999)]
[Proposed Rules]
[Pages 4367-4370]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-1979]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-225-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 757 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 Boeing Model 757 series 
airplanes. This proposal would require revising the Airworthiness 
Limitations Section of the Instructions for maintenance manual [757 
Airworthiness Limitations Instructions (ALI)]. The revision would 
incorporate certain inspections and compliance times to detect fatigue 
cracking of principal structural elements (PSE). This proposal is 
prompted by analysis of data that identified specific initial 
inspection thresholds and repetitive inspection intervals for certain 
PSE's to be added to the ALI. The actions specified by the proposed AD 
are

[[Page 4368]]

intended to ensure that fatigue cracking of various PSE's is detected 
and corrected; such fatigue cracking could adversely affect the 
structural integrity of these airplanes.

DATES: Comments must be received by March 15, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-225-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 Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

FOR FURTHER INFORMATION CONTACT: Patrick Safarian, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue SW., Renton, Washington; telephone (425) 227-2775; fax 
(425) 227-1181.

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 98-NM-225-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. 98-NM-225-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:
    •  Mandatory replacement times for structural components,
    •  Structural inspection intervals, and
    •  Related approved structural inspection procedures 
necessary to show compliance with the damage-tolerance requirements.
    Compliance with the terms specified in the Airworthiness 
Limitations Section 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 airworthiness directive (AD) process.

Actions Taken by the Manufacturer

    Boeing recently has completed extensive analyses and testing of 
fatigue cracking of principal structural elements (PSE) on certain 
Model 757 series airplanes, which included:
    •  Crack growth analysis,
    •  Service experience analysis,
    •  Crack growth testing,
    •  Fatigue testing, and
    •  Analysis of the effectiveness of applicable non-
destructive inspection
    •  Techniques to detect cracking and other anomalies.
    The results of the testing and analyses demonstrated the need to 
incorporate certain inspections into the current Airworthiness 
Limitations Instructions (ALI).

New Revision of ALI

    The FAA has reviewed and approved Boeing Document D622N001-9, 
Revision ``MAY 1997,'' titled ``757 Maintenance Planning Data Document 
(MPD) Section 9, Airworthiness Limitations and Certification 
Maintenance Requirements (CMRs).'' That document is the ALI of the 
maintenance manual to which this proposed AD refers. That document 
describes specific initial inspection thresholds and repetitive 
inspection intervals for certain PSE's [identified as structural 
significant items (SSI) in the ALI]. That document explicitly 
identifies, for the first time, all of the PSE's that are to be 
inspected in accordance with the requirements of the ALI.
    Although the Boeing document includes thresholds for all PSE's, in 
many cases the identified threshold is 50,000 total flight cycles for 
passenger airplanes. Because none of the affected airplanes is likely 
to reach this threshold for a number of years, Boeing has not yet 
developed the specific inspection procedures for these PSE's. However, 
these procedures will be developed well before any airplane reaches the 
threshold, and the FAA may consider further rulemaking when they become 
available.

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 757 ALI to 
incorporate Boeing Document D622N001-9, Revision ``MAY 1997'' of the 
ALI. However, nothing in this proposed AD is intended to affect any of 
the requirements related to the life limits or certification 
maintenance requirements that are contained elsewhere in the ALI. This 
proposed AD is intended to address only those PSE inspections that are 
referred to in Chapter B. (``Airworthiness Limitations--Structural 
Inspections'') of Boeing Document D622N001-9, Revision ``MAY 1997.''

[[Page 4369]]

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 FAR section 91.403(c), 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.

Determination of Grace Period

    This proposed AD allows operators up to three years after the 
effective date of this AD to accomplish the ALI revision required by 
this AD. This period provides operators of airplanes that are 
approaching or have already reached the 25,000-flight-cycle inspection 
threshold with a reasonable amount of time to plan and perform the 
inspections. The FAA notes that only one PSE in the ALI has an initial 
inspection threshold of 25,000 total flight cycles. The majority of 
PSE's in the ALI have an initial inspection threshold that corresponds 
to the design service objective of the affected airplane (i.e., 50,000 
total flight cycles). In addition, the Model 757 Structures Working 
Group, whose membership is composed of many of the major operators 
worldwide and almost all U.S. operators, has been aware of the specific 
contents and requirements of this ALI revision since August 1996. These 
facts have led the FAA to determine that three years is an appropriate 
and reasonable grace period for operators to perform the earliest PSE 
inspections.

Cost Impact

    There are approximately 764 Boeing Model 757 series airplanes of 
the affected design in the worldwide fleet. The FAA estimates that 300 
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 $18,000, 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.
    Although this proposed AD requires only a revision to the current 
ALI, the FAA recognizes that the inspections contained in the ALI would 
then be required by parts 43 and 91 of the FAR. The FAA estimates that 
it would take approximately 1,000 work hours to accomplish all of the 
ALI inspections. At an average labor rate of $60 per work hour, the 
cost to perform the ALI inspections (required by FAR parts 43 and 91, 
rather than by part 39) would be approximately $60,000 per airplane. 
The FAA notes that the majority of work hours needed to perform the 
inspections would be expended when an affected airplane reached the 
50,000-flight-cycle threshold. Based upon current airplane utilization, 
the FAA estimates that no airplane would reach this threshold for at 
least 10 years.

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:

Boeing: Docket 98-NM-225-AD.

    Applicability: Model 757 series airplanes having line numbers 1 
through 764 inclusive, 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 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 ensure continued structural integrity of these airplanes, 
accomplish the following:
    (a) Within 3 years after the effective date of this AD, revise 
Section 9 of the Model 757 Maintenance Planning Data (MPD) Document 
entitled ``Airworthiness Limitations and Certification Maintenance 
Requirements (CMRs)'' to incorporate Chapter B. of Boeing Document 
D622N001-9, Revision ``MAY 1997.''


[[Page 4370]]


    Note 2: The referenced Chapter B. contains a requirement that 
cracks found during the specified inspections be reported to the 
Seattle Aircraft Certification Office. Information collection 
requirements contained in this regulation have been approved by the 
Office of Management and Budget under the provisions of the 
Paperwork Reduction Act of 1980 (44 U.S.C. 3501, et seq.) and have 
been assigned OMB Control Number 2120-0056.

    (b) Except as provided in paragraph (c) of this AD: After the 
actions required by paragraph (a) of this AD have been accomplished, 
no alternative inspections or inspection intervals shall be approved 
for the PSE's contained in Boeing Document D622N001-9, Revision 
``MAY 1997.''
    (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, Seattle 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, Seattle ACO.

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

    (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 January 21, 1999.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-1979 Filed 1-27-99; 8:45 am]
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