[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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