
[Federal Register: April 28, 2008 (Volume 73, Number 82)]
[Proposed Rules]               
[Page 22845-22848]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr28ap08-18]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-0414; Directorate Identifier 2007-NM-095-AD]
RIN 2120-AA64

 
Airworthiness Directives; Boeing Model 747-100, 747-100B, 747-
100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 
747-400F, and 747SR Series Airplanes

AGENCY: Federal Aviation Administration (FAA), Department of 
Transportation (DOT).

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to supersede an existing airworthiness 
directive (AD) that applies to certain Boeing Model 747 series 
airplanes. The existing AD currently requires repetitive inspections 
for cracking and corrosion of all exposed surfaces of the carriage 
spindles (including the inner bore and aft links) of the trailing edge 
flaps, and additional inspection and corrective action if necessary. 
The existing AD also requires repetitive overhaul of the carriage 
spindle and aft link, which terminates the repetitive inspections. This 
proposed AD would add a repetitive inspection to detect broken parts, 
and revise the overhaul threshold and repetitive intervals. This 
proposed AD results from analysis that showed additional inspections 
should be done to prevent the loss of a flap, and that the flight-hour-
based interval should be revised to a flight-cycle-based interval, 
because the greatest loads on the spindles happen during takeoff and 
landing. We are proposing this AD to detect and correct failed carriage 
spindles or aft links for the inboard or outboard trailing edge flaps. 
Such failure could cause the flap to depart the airplane, reducing the 
flightcrew's ability to maintain the safe flight and landing of the 
airplane.

DATES: We must receive comments on this proposed AD by June 12, 2008.

ADDRESSES: You may send comments by any of the following methods:
     Federal eRulemaking Portal: Go to http://
www.regulations.gov. Follow the instructions for submitting comments.
     Fax: 202-493-2251.
     Mail: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue SE., Washington, DC 20590.
     Hand Delivery: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., 
Monday through Friday, except Federal holidays.
    For service information identified in this AD, contact Boeing 
Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207.

Examining the AD Docket

    You may examine the AD docket on the Internet at http://
www.regulations.gov; or in person at the Docket Management Facility 
between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays. The AD docket contains this proposed AD, the regulatory 
evaluation, any comments received, and other information. The street 
address for the Docket Office (telephone 800-647-5527) is in the 
ADDRESSES section. Comments will be available in the AD docket shortly 
after receipt.

FOR FURTHER INFORMATION CONTACT: Gary Oltman, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 
917-6443; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to send any written relevant data, views, or 
arguments about this proposed AD. Send your comments to an address 
listed under the ADDRESSES section. Include ``Docket No. FAA-2008-0414; 
Directorate Identifier 2007-NM-095-AD'' at the beginning of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of this proposed AD. We 
will consider all comments received by the closing date and may amend 
this proposed AD because of those comments.
    We will post all comments we receive, without change, to http://
www.regulations.gov, including any personal information you provide. We 
will also post a report summarizing each substantive verbal contact we 
receive about this proposed AD.

Discussion

    On August 6, 1990, we issued AD 90-17-19, amendment 39-6705 (55 FR 
33280, August 15, 1990), for all Boeing Model 747 series airplanes, 
except the Model 747SP. That AD requires repetitive inspections for 
cracking and corrosion of all exposed surfaces of the carriage spindles 
(including the inner bore and aft links) of the trailing edge flaps, 
and additional inspection and corrective action if necessary. The 
existing AD also requires repetitive overhaul of the carriage spindle 
and aft link, which terminates the repetitive inspections. That AD 
resulted from a report of failure of two aft links in the spindles on 
one flap, causing control problems during approach and landing. We 
issued that AD to prevent failure of the trailing edge flaps' carriage 
spindles, which could result in reduced controllability of the 
airplane.

Actions Since Existing AD Was Issued

    Since we issued AD 90-17-19, the manufacturer conducted a dynamic 
aerodynamic analysis, which showed that the airplane might not have

[[Page 22846]]

sufficient roll authority to overcome loss of lift caused by a 
departure of a single left- or right-hand inboard or outboard trailing 
edge flap. The manufacturer then conducted a structural analysis of the 
flap attach structure and fail-safe components, which showed that 
additional inspections should be done to prevent the loss of a flap, 
and that the flight-hour-based interval required by AD 90-17-19 should 
be revised to a flight-cycle-based interval because the greatest loads 
on the spindles happen during takeoff and landing and not during 
flight.

Relevant Service Information

    We have reviewed Boeing Service Bulletin 747-27-2280, Revision 6, 
dated February 14, 2008. We referred to Boeing Service Bulletin 747-27-
2280, Revision 3, dated November 30, 1989, as the appropriate source of 
service information for accomplishing the actions required by AD 90-17-
19. Revision 6 adds a repetitive inspection of all eight carriage 
spindles and aft links to detect a broken carriage spindle or aft link, 
and corrective action if necessary. The remaining procedures in 
Revision 6 of the service bulletin are unchanged from Revision 3 of the 
service bulletin. The corrective action is replacing the broken part 
before further flight.
    Revision 6 of the service bulletin also revises the overhaul 
threshold and the repetitive overhaul interval as follows (AD 90-17-19 
required the repetitive overhaul):
     The initial overhaul threshold is the earlier of 8 years 
or a specified number of flight cycles. The number of flight cycles is 
either 6,000 or 9,000, depending on the airplane group specified in the 
service bulletin and the type and location of carriage originally 
installed.
     The repetitive overhaul interval is also the earlier of 8 
years or the same specified number of flight cycles based on the same 
variables.
    We have also reviewed Boeing Service Bulletin 747-27-2371, dated 
December 20, 2000, which applies only to Group 1 and Group 3 airplanes 
identified in Boeing Service Bulletin 747-27-2280, Revision 6. Boeing 
Service Bulletin 747-27-2371 describes procedures for replacing the 
link assemblies with new link assemblies made from improved corrosion-
resistant steel (CRES) that has a bearing race that is machined into 
the link. Doing this replacement eliminates the need for the repetitive 
overhauls specified in Boeing Service Bulletin 747-27-2280, Revision 6, 
for that aft link only.
    Accomplishing the actions specified in the service information is 
intended to adequately address the unsafe condition.

FAA's Determination and Requirements of the Proposed AD

    We have evaluated all pertinent information and identified an 
unsafe condition that is likely to develop on other airplanes of the 
same type design. For this reason, we are proposing this AD, which 
would supersede AD 90-17-19 and would retain certain requirements of 
the existing AD at revised intervals. This proposed AD would also 
require a repetitive inspection to detect a broken carriage spindle or 
broken aft link, and corrective action if necessary. The proposed AD 
would also include, for certain airplanes, procedures for replacing the 
link assemblies with new link assemblies made from improved CRES that 
has a bearing race that is machined into the link, which would end the 
need for the repetitive overhauls specified in Boeing Service Bulletin 
747-27-2280, Revision 6, for that aft link only.

Changes to Existing AD

    This proposed AD would retain certain requirements of AD 90-17-19. 
Since AD 90-17-19 was issued, the AD format has been revised, and 
certain paragraphs have been rearranged. As a result, the corresponding 
paragraph identifiers have changed in this proposed AD, as listed in 
the following table:

                      Revised Paragraph Identifiers
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                                             Corresponding  requirement
        Requirement in AD 90-17-19              in this  proposed AD
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paragraph A...............................  paragraph (f).
paragraph A.1.............................  paragraph (f).
paragraph A.2.............................  paragraph (f)(1).
paragraph A.3.............................  paragraph (f)(2).
paragraph A.4.............................  paragraph (f)(3).
paragraph A.5.............................  paragraph (f)(4).
paragraph B...............................  paragraph (g).
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    We have revised paragraph A.5. of AD 90-17-19 (paragraph (f)(4) of 
this proposed AD) to allow any part of both carriage spindle/aft link 
assemblies to be repaired according to data that conform to the 
airplane's type certificate and that are approved by an Authorized 
Representative for the Boeing Commercial Airplanes Delegation Option 
Authorization Organization whom we have authorized to make such 
findings.
    In this proposed AD, the ``detailed visual inspection'' specified 
in AD 90-17-19 is referred to as a ``detailed inspection.'' We have 
included the definition for a detailed inspection in Note 1 of the 
proposed AD. We have also included the definition of a general visual 
inspection in Note 2 of this AD. That definition was not included in AD 
90-17-19.

Costs of Compliance

    There are about 925 airplanes of the affected design in the 
worldwide fleet, which includes 160 airplanes of U.S. registry. The 
following table provides the estimated costs for U.S. operators to 
comply with this proposed AD. The average labor rate is $80 per work 
hour.

                                                 Estimated Costs
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              Action                      Work hours         Parts      Cost per airplane        Fleet cost
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Inspection and overhaul (required   Between 120 and 140,          $0  Between $9,600 and    Between $1,536,000
 by AD 90-17-19).                    per flap per cycle.               $11,200, per flap     and $1,792,000, per
                                                                       per overhaul cycle.   flap per cycle.
Repetitive inspection for broken    2, per inspection              0  $160, per inspection  $25,600, per
 parts (new proposed action).        cycle.                            cycle.                inspection cycle.
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Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, Section 106, describes the 
authority of the FAA Administrator. Subtitle VII, Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    We are issuing this rulemaking under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701, ``General 
requirements.'' Under that section, Congress charges the FAA with

[[Page 22847]]

promoting safe flight of civil aircraft in air commerce by prescribing 
regulations for practices, methods, and procedures the Administrator 
finds necessary for safety in air commerce. This regulation is within 
the scope of that authority because it addresses an unsafe condition 
that is likely to exist or develop on products identified in this 
rulemaking action.

Regulatory Findings

    We have determined that this proposed AD would not have federalism 
implications under Executive Order 13132. This proposed AD would not 
have a substantial direct effect 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.
    For the reasons discussed above, I certify that the 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. 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.
    We prepared a regulatory evaluation of the estimated costs to 
comply with this proposed AD and placed it in the AD docket. See the 
ADDRESSES section for a location to examine the regulatory evaluation.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA proposes to amend 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. The Federal Aviation Administration (FAA) amends Sec.  39.13 by 
removing amendment 39-6705 (55 FR 33280, August 15, 1990) and adding 
the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2008-0414; Directorate Identifier 2007-NM-
095-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by June 12, 
2008.

Affected ADs

    (b) This AD supersedes AD 90-17-19.

Applicability

    (c) This AD applies to all Boeing Model 747-100, 747-100B, 747-
100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 
747-400F, and 747SR series airplanes, certificated in any category.

Unsafe Condition

    (d) This AD results from analysis that showed that additional 
inspections should be done to prevent the loss of a flap, and that 
the flight-hour-based interval should be revised to a flight-cycle-
based interval, because the greatest loads on the spindles happen 
during takeoff and landing. We are issuing this AD to detect and 
correct failed carriage spindles or aft links for the inboard or 
outboard trailing edge flaps. Such failure could cause the flap to 
depart the airplane, reducing the flightcrew's ability to maintain 
the safe flight and landing of the airplane.

Compliance

    (e) You are responsible for having the actions required by this 
AD performed within the compliance times specified, unless the 
actions have already been done.

Requirements of AD 90-17-19

Repetitive Inspections

    (f) For all airplanes except those airplanes on which the 
repetitive overhauls required by paragraph B. of AD 90-17-19 are 
being accomplished as of the effective date of this AD: Prior to the 
accumulation of 30,000 flight hours or 8 years on each new or 
previously overhauled flap carriage spindle, whichever occurs first, 
remove the aft link and thrust collars from the trailing edge flaps' 
carriage spindles and perform a detailed inspection of all exposed 
surfaces of the carriage spindles, including inner bore, and aft 
links to detect cracking and corrosion, in accordance with the 
Accomplishment Instructions of Boeing Service Bulletin 747-27-2280, 
Revision 3, dated November 30, 1989.

    Note 1: For the purposes of this AD, a detailed inspection is: 
``An intensive examination of a specific item, installation, or 
assembly to detect damage, failure, or irregularity. Available 
lighting is normally supplemented with a direct source of good 
lighting at an intensity deemed appropriate. Inspection aids such as 
mirror, magnifying lenses, etc., may be necessary. Surface cleaning 
and elaborate procedures may be required.''

    (1) If no cracking or corrosion is found, repeat the inspections 
required by paragraph (f) of this AD at intervals not to exceed 12 
months until the carriage spindles are overhauled in accordance with 
paragraph (g) of this AD.
    (2) If a cracked carriage spindle or aft link is found, prior to 
further flight, replace the part(s) in accordance with the service 
bulletin.
    (3) If corrosion is found on any part of the carriage spindle/
aft link assembly, but not on the other assembly on the same flap, 
perform a repetitive general visual inspection in accordance with 
the service bulletin at intervals not to exceed 2 months. Overhaul 
or replace corroded parts in accordance with the service bulletin 
within 36 months after detection of the corrosion.
    (4) If corrosion is found on any part of both carriage spindle/
aft link assemblies on the same flap, prior to further flight, 
overhaul or replace the part(s) in accordance with the service 
bulletin or repair in accordance with the procedures specified in 
paragraph (m) of this AD.

    Note 2: For the purposes of this AD, a general visual inspection 
is: ``A visual examination of an interior or exterior area, 
installation, or assembly to detect obvious damage, failure, or 
irregularity. This level of inspection is made from within touching 
distance unless otherwise specified. A mirror may be necessary to 
ensure visual access to all surfaces in the inspection area. This 
level of inspection is made under normally available lighting 
conditions such as daylight, hangar lighting, flashlight, or 
droplight and may require removal or opening of access panels or 
doors. Stands, ladders, or platforms may be required to gain 
proximity to the area being checked.''

Initial and Repetitive Overhauls

    (g) For all airplanes: Prior to the accumulation of 8 years or 
30,000 flight hours on any new or previously overhauled flap 
carriage spindle, whichever occurs later, remove the carriage 
spindle and aft link, and overhaul in accordance with the 
Accomplishment Instructions of Boeing Service Bulletin 747-27-2280, 
Revision 3, dated November 30, 1989. Repeat the overhaul thereafter 
at intervals not to exceed 8 years or 30,000 flight hours, whichever 
occurs earlier. Accomplishment of initial overhaul required by this 
paragraph terminates the requirements of paragraph (f) of this AD.

New Requirements of This AD

Terminating Requirements

    (h) The actions specified in paragraphs (i) and (j) of this AD 
must be accomplished in their entirety, at the specified compliance 
times, to terminate the requirements of paragraphs (f) and (g) of 
this AD. There is no terminating action for the requirements of 
paragraphs (i) and (j) of this AD.

Repetitive Inspection for Broken Parts

    (i) For all airplanes: Within 12 months or 400 flight cycles 
after the effective date of this AD, whichever occurs earlier, do a 
general visual inspection of all eight carriage spindles and aft 
links to detect a broken carriage spindle or broken aft link, and do 
all applicable corrective actions before further flight. Repeat the 
inspection thereafter at intervals not to exceed 400 flight cycles. 
Do all actions in accordance with the Accomplishment Instructions of 
Boeing Service Bulletin 747-27-2280, Revision 6, dated February 14, 
2008. For airplanes identified in Note (d) of Table 1 in paragraph 
1.E., ``Compliance,'' of Boeing Service Bulletin 747-27-2280, 
Revision 6, dated February 14, 2008, the initial compliance

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time and repetitive interval for a flap may be extended to 1,000 
flight cycles when new carriages are installed at both the inboard 
and outboard carriage locations on the flap.

Repetitive Overhauls

    (j) For all airplanes: At the later of the times specified in 
paragraph (j)(1) or (j)(2) of this AD, remove the carriage spindle 
and aft link, and overhaul in accordance with the Accomplishment 
Instructions of Boeing Service Bulletin 747-27-2280, Revision 6, 
dated February 14, 2008. Repeat the overhaul thereafter at the 
applicable repeat interval specified in paragraph 1.E., 
``Compliance,'' of Boeing Service Bulletin 747-27-2280, Revision 6, 
dated February 14, 2008.
    (1) The applicable threshold specified in paragraph 1.E. 
``Compliance,'' of Boeing Service Bulletin 747-27-2280, Revision 6, 
dated February 14, 2008.
    (2) Within 48 months after the effective date of this AD.

Optional Terminating Action

    (k) For Groups 1 and 3 airplanes identified in Boeing Service 
Bulletin 747-27-2280, Revision 6, dated February 14, 2008: Replacing 
the existing 4340M aft link with a new corrosion resistant steel 
(CRES) aft link in accordance with the Accomplishment Instructions 
of Boeing Service Bulletin 747-27-2371, dated December 20, 2000, 
terminates the repetitive inspection requirements of paragraph (f) 
of this AD, and the repetitive overhaul requirements of paragraphs 
(g) and (j) of this AD for that aft link only. The repetitive 
inspections for broken parts required by paragraph (i) of this AD 
cannot be terminated.

Credit for Previous Revision of Service Bulletin

    (l) Actions done before the effective date of this AD in 
accordance with Boeing Service Bulletin 747-27-2280, Revision 4, 
dated April 26, 2001, are acceptable for compliance with the 
corresponding requirements of paragraphs (f) and (g) of this AD. 
Actions done before the effective date of this AD in accordance with 
Boeing Service Bulletin 747-27-2280, Revision 5, dated April 5, 
2007, are acceptable for compliance with the corresponding 
requirements of paragraphs (i) and (j) of this AD.

Alternative Methods of Compliance (AMOCs)

    (m)(1) The Manager, Seattle Aircraft Certification Office (ACO), 
FAA, has the authority to approve AMOCs for this AD, if requested in 
accordance with the procedures found in 14 CFR 39.19.
    (2) To request a different method of compliance or a different 
compliance time for this AD, follow the procedures in 14 CFR 39.19. 
Before using any approved AMOC on any airplane to which the AMOC 
applies, notify your appropriate principal inspector (PI) in the FAA 
Flight Standards District Office (FSDO), or lacking a PI, your local 
FSDO.
    (3) AMOCs approved previously in accordance with AD 90-17-19 are 
approved as AMOCs for the corresponding provisions of this AD.
    (4) Adjustments to the compliance times approved previously in 
accordance with AD 90-17-19 are not approved for the corresponding 
provisions of this AD.
    (5) An AMOC that provides an acceptable level of safety may be 
used for any repair required by this AD, if it is approved by an 
Authorized Representative for the Boeing Commercial Airplanes 
Delegation Option Authorization Organization who has been authorized 
by the Manager, Seattle ACO, to make those findings. For a repair 
method to be approved, the repair must meet the certification basis 
of the airplane, and the approval must specifically refer to this 
AD.

    Issued in Renton, Washington, on April 18, 2008.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E8-9122 Filed 4-25-08; 8:45 am]

BILLING CODE 4910-13-P
