[Federal Register Volume 64, Number 170 (Thursday, September 2, 1999)]
[Proposed Rules]
[Pages 48120-48123]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-22921]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-56-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.


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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 series 
airplanes. This proposal would require repetitive inspections or checks 
to detect broken H-11 steel bolts at the wing rear spar side-of-body on 
the lower chord splice plate and kick fitting; and corrective actions, 
if necessary. This proposal also would require eventual replacement of 
the existing bolts with new inconel bolts, which would constitute 
terminating action for the repetitive inspections. This proposal is 
prompted by a report of broken bolts at the wing rear spar side-of-body 
on the lower chord splice plate. The actions specified by the proposed 
AD are intended to prevent cracking of the bolts due to stress 
corrosion, which could result in reduced structural integrity of the 
wing-to-body joint structure.

DATES: Comments must be received by October 18, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-56-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. 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 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 99-NM-56-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. 99-NM-56-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received a report indicating that an operator found 
four broken high strength H-11 steel bolts on a Boeing Model 747 series 
airplane. The broken bolts were on one side of the wing rear spar side-
of-body on the lower chord splice plate. The broken bolts were 
attributed to stress corrosion cracking. This condition, if not 
detected, could result in reduced structural integrity of the wing-to-
body joint structure.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletin 
747-57A2309, dated February 25, 1999. The service bulletin describes 
procedures for repetitive detailed visual inspections, or 
alternatively, ultrasonic inspections or torque checks, to detect 
broken H-11 steel bolts common to the rear spar lower chord splice 
plate and H-11 steel bolts on the wing rear spar lower kick fitting; 
and corrective actions, if necessary. The corrective actions involve 
performing either an ultrasonic inspection or torque check for broken 
bolts, if necessary; an open hole high frequency eddy current (HFEC) 
inspection to detect cracks at the broken bolt hole location; and 
installing an inconel bolt, which would eliminate the need for the 
repetitive inspections at this bolt location, as applicable. The 
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 
specified in the referenced service bulletin as terminating action for 
the repetitive inspections.
    The FAA has determined that long-term continued operational safety 
would 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 continual 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 may be contacted for 
disposition of certain repair 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 repair method to be approved, the 
approval letter must specifically reference this AD.

Cost Impact

    There are approximately 523 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that

[[Page 48122]]

115 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 inspection of the wing 
rear spar side-of-body lower chord splice plate and kick fitting high 
strength H-11 steel bolts proposed by this AD on U.S. operators is 
estimated to be $6,900, or $60 per airplane, per inspection cycle.
    It would take approximately 13 (Groups 1, 3, 4, and 5 airplanes) 
and 10 (Group 2 airplanes) work hours per airplane to accomplish the 
proposed open hole HFEC inspection and replacement, at an average labor 
rate of $60 per work hour. Required parts would cost approximately 
$4,500 per airplane. Based on these figures, the cost impact of the 
open hole HFEC inspection and replacement proposed by this AD on U.S. 
operators is estimated to be $5,280 (Groups 1, 3, 4, and 5 airplanes) 
and $5,100 (Group 2 airplanes) per airplane.
    The cost impact figures discussed above are 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:

Boeing: Docket 99-NM-56-AD.

    Applicability: Model 747 series airplanes, as listed in Boeing 
Alert Service Bulletin 747-57A2309, dated February 25, 1999, 
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 (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 detect and prevent cracking of the high strength H-11 steel 
bolts on the wing rear spar side-of-body on the lower chord splice 
plate and kick fitting due to stress corrosion, which could result 
in reduced structural integrity of the wing-to-body joint structure, 
accomplish the following:

Repetitive Inspections

    (a) Within 12 months after the effective date of this AD, 
perform a detailed visual inspection, or alternatively, an 
ultrasonic inspection or torque check, to detect broken H-11 steel 
bolts common to the rear spar lower chord splice plate and the H-11 
steel bolts common to the wing rear spar lower chord kick fitting, 
in accordance with Boeing Alert Service Bulletin 747-57A2309, dated 
February 25, 1999. Thereafter, repeat the applicable inspection or 
torque check at intervals not to exceed 18 months, until 
accomplishment of the actions specified in paragraph (d) of this AD.

    Note 2: For the purposes of this AD, a detailed 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.''

Corrective Actions

    (b) If there is any detection or indication that any bolt is 
broken during the inspection required by paragraph (a) of this AD, 
prior to further flight, perform the applicable corrective action 
[i.e., ultrasonic inspection, torque check, high frequency eddy 
current (HFEC) inspection, repair, and replacement] in accordance 
with Boeing Alert Service Bulletin 747-57A2309, dated February 25, 
1999; except as provided in paragraph (c) of this AD. Replacement of 
a broken bolt with a new inconel bolt in accordance with the service 
bulletin constitutes terminating action for the repetitive 
inspection requirements of paragraph (a) of this AD for that bolt 
only.
    (c) If any crack is detected during any corrective action 
required by paragraph (b) of this AD; 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 data meeting the type 
certification basis of the airplane approved by 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-
57A2309, dated February 25, 1999. 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 HFEC inspection to detect 
cracks at the bolt hole location for the eight high strength H-11 
steel bolts common to the rear spar lower chord splice plate and the 
four high strength H-11 steel bolts common to the wing rear spar 
lower chord kick fitting. If any crack is detected, prior to further 
flight, perform applicable corrective actions in accordance with 
paragraph (c) of this AD.
    (2) Replace all eight high strength H-11 steel bolts common to 
the rear spar lower chord splice plate and all four high strength H-
11 steel bolts common to the wing rear spar lower chord kick fitting 
with new inconel bolts.

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Spares

    (e) As of the effective date of this AD, no person shall install 
an H-11 steel bolt having part number (P/N) BACB30MT ( ) * ( ) or 
BACB30TR ( ) * ( ), or any other H-11 steel bolt in the locations 
specified in this AD, on any airplane.

Alternative Methods 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 
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 August 27, 1999.
Vi L. Lipski,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-22921 Filed 9-1-99; 8:45 am]
BILLING CODE 4910-13-P