[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