[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.
[[Page 48121]]
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.
[[Page 48123]]
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
