[Federal Register Volume 64, Number 168 (Tuesday, August 31, 1999)]
[Proposed Rules]
[Pages 47440-47442]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-22529]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 98-NM-339-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747-100, -200 and 747SP
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 747-100, -200
and 747SP series airplanes. This proposal would require repetitive
detailed visual and ultrasonic inspections to detect missing, damaged,
or broken taperlock bolts in the diagonal brace underwing fittings; and
corrective actions, if necessary. This proposal also would require
eventual replacement of the aft 10 taperlock bolts with new bolts,
which would constitute terminating action for the repetitive
inspections. This proposal is prompted by reports of damaged, broken,
and corroded taperlock bolts of the diagonal brace underwing fittings
on the outboard strut due to stress corrosion cracking. The actions
specified by the proposed AD are intended to prevent loss of the
underwing fitting load path due to missing, damaged, or broken
taperlock bolts, which could result in separation of the engine and
strut from the airplane.
DATES: Comments must be received by October 15, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 98-NM-339-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: Tamara L. Anderson, Aerospace
Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane
Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue,
SW., Renton, Washington 98055-4056; telephone (425) 227-2771; 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
[[Page 47441]]
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-339-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-339-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
The FAA has received reports indicating that damaged, broken, and
corroded taperlock bolts were found on Boeing Model 747-100 and -200
series airplanes. The cause of the broken taperlock bolts is stress
corrosion. The bolts are located on the diagonal brace underwing
fittings on the outboard strut at the Number 1 and Number 4 pylon
engine positions. This condition, if not corrected, could result in
separation of the engine and strut from the airplane.
The subject taperlock bolts on Boeing Model 747SP series airplanes
are identical to those on the affected Boeing Model 747-100 and -200
series airplanes. Therefore, all of these airplanes may be subjected to
the same unsafe condition.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Alert Service Bulletin
747-57A2308, dated August 6, 1998, which describes procedures for
repetitive detailed visual and ultrasonic inspections to detect
missing, damaged, or broken taperlock bolts; and corrective actions, if
necessary. The corrective actions involve performing an open hole high
frequency eddy current inspection to detect cracks at the bolt hole
locations; and replacing missing, damaged, or broken taperlock bolt
with a new bolt. This service bulletin also describes procedures for an
optional terminating action for the repetitive inspections.
Accomplishment of the actions specified in the service bulletin is
intended to adequately address the identified unsafe condition.
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, except as discussed below.
Differences Between Proposed Rule and Service Bulletin
Operators should note that, although incorporation of the
terminating action specified in the referenced service bulletin is
optional, this AD proposes to mandate, within 48 months after the
effective date of this AD, the open hole inspection and replacement of
the aft 10 taperlock bolts with new bolts specified in the referenced
service bulletin as terminating action for the repetitive inspections.
The FAA has determined that long-term continued operational safety
will be better assured by design changes to remove the source of the
problem, rather than by repetitive inspections. Long-term inspections
may not be providing the degree of safety assurance necessary for the
transport airplane fleet. This, coupled with a better understanding of
the human factors associated with numerous continued inspections, has
led the FAA to consider placing less emphasis on inspections and more
emphasis on design improvements. The proposed replacement requirement
is in consonance with these conditions.
In addition, operators should note that, although the service
bulletin specifies that the manufacturer must be contacted for
disposition of certain conditions, this proposal would require the
repair of those conditions to be accomplished in accordance with a
method approved by the FAA; or in accordance with data meeting the type
certification basis of the airplane approved by a Boeing Company
Designated Engineering Representative who has been authorized by the
FAA to make such findings. For a method to be approved, the approval
letter must specifically reference this AD.
Cost Impact
There are approximately 274 airplanes of the affected design in the
worldwide fleet. The FAA estimates that 122 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 inspection, at an
average labor rate of $60 per work hour. Based on these figures, the
cost impact of the proposed inspection on U.S. operators is estimated
to be $7,320, or $60 per airplane, per inspection cycle.
It would take approximately 8 work hours per airplane to accomplish
the proposed terminating action, at an average labor rate of $60 per
work hour. Required parts would cost approximately $8,008 per airplane.
Based on these figures, the cost impact of the proposed terminating
action on U.S. operators is estimated to be $1,035,536, or $8,488 per
airplane.
The cost impact figures discussed above are based on the assumption
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.
[[Page 47442]]
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-339-AD.
Applicability: Model 747-100, -200, and 747SP series airplanes,
line numbers 1 through 567 inclusive; equipped with aluminum
diagonal brace underwing fittings; 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 (f) 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 loss of the underwing fitting load path due to
missing, damaged, or broken taperlock bolts, which could result in
separation of the engine and strut from the airplane, accomplish the
following:
Repetitive Inspections
(a) Prior to the accumulation of 9,000 total flight cycles, or
within 18 months after the effective date of this AD, whichever
occurs later, accomplish the actions required by paragraphs (a)(1)
and (a)(2) of this AD in accordance with Boeing Alert Service
Bulletin 747-57A2308, dated August 6, 1998. Thereafter, repeat the
inspections at intervals not to exceed 18 months until
accomplishment of the actions specified in paragraph (d) of this AD.
(1) Perform a detailed visual inspection to detect missing
taperlock bolts in the diagonal brace underwing fitting at the
Number 1 and Number 4 pylons.
Note 2: For the purposes of this AD, a detailed visual
inspection is defined as: ``An intensive visual examination of a
specific structural area, system, installation, or assembly to
detect damage, failure, or irregularity. Available lighting is
normally supplemented with a direct source of good lighting at
intensity deemed appropriate by the inspector. Inspection aids such
as mirror, magnifying lenses, etc., may be used. Surface cleaning
and elaborate access procedures may be required.''
(2) Perform an ultrasonic inspection to detect damaged or broken
taperlock bolts in the diagonal brace underwing fitting at the
Number 1 and Number 4 pylons.
Corrective Actions
(b) If any missing, damaged, or broken taperlock bolt is
detected during any inspection required by paragraph (a) of this AD,
prior to further flight, perform the applicable corrective actions
(i.e., inspection, drill/ream, and replacement) in accordance with
Boeing Alert Service Bulletin 747-57A2308, dated August 6, 1998;
except as provided in paragraph (c) of this AD. Replacement of any
taperlock bolt with a new bolt in accordance with this paragraph
constitutes terminating action for the repetitive inspections
required by paragraph (a) of this AD for that bolt only.
(c) If any crack is detected during the inspection required by
paragraph (b) of this AD and the damage to a bolt hole exceeds first
oversize (for 0.5-inch bolts) or second oversize (for 0.4375-inch
bolts); and the service bulletin specifies to contact Boeing for
appropriate Action: Prior to further flight, repair in accordance
with a method approved by the Manager, Seattle Aircraft
Certification Office (ACO), FAA, Transport Airplane Directorate; or
in accordance with a Boeing Company Designated Engineering
Representative who has been authorized by the Manager, Seattle ACO,
to make such findings. For a repair method to be approved by the
Manager, Seattle ACO, as required by this paragraph, the Manager's
approval letter must specifically reference this AD.
Terminating Action
(d) Within 48 months after the effective date of this AD,
accomplish the actions required by paragraphs (d)(1) and (d)(2) of
this AD in accordance with Boeing Alert Service Bulletin 747-
57A2308, dated August 6, 1998. Accomplishment of the actions
specified in this paragraph constitutes terminating action for the
repetitive inspection requirements of this AD.
(1) Prior to accomplishing the replacement required by paragraph
(d)(2) of this AD, perform an open hole high frequency eddy current
inspection to detect cracks at the bolt hole locations of the aft 10
taperlock bolts. If any cracking is detected, prior to further
flight, perform applicable corrective actions in accordance with
paragraph (c) of this AD.
(2) Replace the aft 10 taperlock bolts with new bolts in the
diagonal brace underwing fitting at the Number 1 and Number 4
pylons.
Spares
(e) As of the effective date of this AD, no person shall install
a bolt, part number BACB30PE( ) * ( ), or any other bolt made of
4340, 8740, or PH13-8 Mo steel, in the locations specified in this
AD, on any airplane.
Alternate Method of Compliance
(f) 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 ACO. 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.
Special Flight Permits
(g) 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 August 24, 1999.
Vi L. Lipski,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 99-22529 Filed 8-30-99; 8:45 am]
BILLING CODE 4910-13-P
