[Federal Register Volume 71, Number 27 (Thursday, February 9, 2006)]
[Proposed Rules]
[Pages 6687-6691]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-1767]


-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2006-23842; Directorate Identifier 2005-NM-145-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 777-200 and 777-300 Series 
Airplanes

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

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) 
for certain Boeing Model 777-200 and 777-300 series airplanes. This 
proposed AD would require repetitive inspections for discrepancies of 
the splined

[[Page 6688]]

components that support the inboard end of the inboard trailing edge 
flap, and related investigative, corrective, and other specified 
actions if necessary. This proposed AD would also require a one-time 
modification of the inboard support of the inboard trailing edge flap 
by installing a new isolation strap and attachment hardware. This 
proposed AD would also require repetitive replacement of the torque 
tube assembly. This proposed AD results from reports of corrosion on 
the torque tube and closeout rib fittings that support the inboard end 
of the inboard trailing edge flap, as well as a structural reassessment 
of the torque tube joint that revealed the potential for premature 
fatigue cracking of the torque tube that would not be detected using 
reasonable inspection methods. We are proposing this AD to detect and 
correct corrosion or cracking of the torque tube and closeout rib 
fittings that support the inboard end of the inboard trailing edge 
flap. Cracking in these components could lead to a fracture, which 
could result in loss of the inboard trailing edge flap and consequent 
reduced controllability of the airplane.

DATES: We must receive comments on this proposed AD by March 27, 2006.

ADDRESSES: Use one of the following addresses to submit comments on 
this proposed AD.
     DOT Docket Web site: Go to http://dms.dot.gov and follow 
the instructions for sending your comments electronically.
     Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your 
comments electronically.
     Mail: Docket Management Facility, U.S. Department of 
Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, 
Washington, DC 20590.
     Fax: (202) 493-2251.
     Hand Delivery: Room PL-401 on the plaza level of the 
Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, 
Washington 98124-2207, for the service information identified in this 
proposed AD.

FOR FURTHER INFORMATION CONTACT: Gary Oltman, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
917-6443; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to submit any relevant written data, views, or 
arguments regarding this proposed AD. Send your comments to an address 
listed in the ADDRESSES section. Include the docket number ``FAA-2006-
23842; Directorate Identifier 2005-NM-145-AD'' at the beginning of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of the proposed AD. We will 
consider all comments received by the closing date and may amend the 
proposed AD in light of those comments.
    We will post all comments we receive, without change, to http://dms.dot.gov, including any personal information you provide. We will 
also post a report summarizing each substantive verbal contact with FAA 
personnel concerning this proposed AD. Using the search function of 
that Web site, anyone can find and read the comments in any of our 
dockets, including the name of the individual who sent the comment (or 
signed the comment on behalf of an association, business, labor union, 
etc.). You may review DOT's complete Privacy Act Statement in the 
Federal Register published on April 11, 2000 (65 FR 19477-78), or you 
may visit http://dms.dot.gov.

Examining the Docket

    You may examine the AD docket on the Internet at http://dms.dot.gov, or in person at the Docket Management Facility office 
between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays. The Docket Management Facility office (telephone (800) 647-
5227) is located on the plaza level of the Nassif Building at the DOT 
street address stated in the ADDRESSES section. Comments will be 
available in the AD docket shortly after the Docket Management System 
receives them.

Discussion

    We have received reports that corrosion has been found on the 
torque tube and closeout rib fitting assembly that support the inboard 
end of the inboard trailing edge flap on certain Boeing Model 777-200 
and -300 series airplanes. Investigation has revealed contact between 
the splined areas of the torque tube and closeout rib fitting, causing 
wear to the titanium-cadmium plating of the components. When the grease 
on these components dries out, moisture may enter the area, and 
corrosion may form in areas where the plating has worn away. This 
corrosion may subsequently lead to corrosion pitting and cracking that 
can propagate by stress corrosion. Also, a structural reassessment of 
Boeing Model 777-200 and 777-300 series airplanes revealed the 
potential for premature fatigue cracking of the torque tube of the 
inboard trailing edge flap, whether or not the torque tube is corroded. 
This premature fatigue cracking would not be detected by traditional 
inspection methods such as visual or non-destructive inspection 
techniques. Cracking of the torque tube or closeout rib fitting, if not 
corrected, could lead to a fracture of the torque tube or a closeout 
rib fitting, which could result in loss of the inboard trailing edge 
flap and consequent reduced controllability of the airplane.

Relevant Service Information

    We have reviewed Boeing Service Bulletin 777-57A0048, Revision 1, 
dated June 9, 2005. The service bulletin describes procedures for 
performing repetitive detailed inspections for any discrepancy of the 
splined components (torque tube, closeout rib fitting, carrier beam 
pillow block fitting assembly (i.e., the matched set of two carrier 
beam pillow block fittings) and the drive crank support) that support 
the inboard end of the inboard trailing edge flap. Discrepancies of the 
torque tube and closeout rib fitting include light contact wear, 
corrosion pits, corrosion, cracking, and fracture. Discrepancies of the 
other splined components consist of damage to the cadmium plating. (The 
carrier beam pillow block fitting assembly and drive crank support are 
made from corrosion-resistant steel. The condition of the plating on 
these components must be inspected because the plating helps to protect 
these components from the steel torque tube, which is made of less 
corrosion-resistant 4330M steel.)
    If no discrepancy is found, the service bulletin describes 
procedures for other specified actions that include:
     Assembling the splined components with corrosion-
inhibiting compound.
     Modifying certain splined components by installing a new 
isolation strap and attachment hardware. (Installing the isolation 
strap is intended to prevent a washer installed between the drive crank 
support and the carrier beam pillow block fittings from coming into 
contact with the torque tube splines, which could damage the finish on 
the torque tube splines.)
     Refinishing the components as necessary.

[[Page 6689]]

    If a discrepancy is found, the service bulletin describes 
procedures for corrective actions that include:
     Determining the condition of the spline interface by doing 
an evaluation of the level of spline rework using the guidelines in 
Appendix A of the service bulletin.
     Blending out light contact wear (defined in the service 
bulletin as shallow surface irregularities or discrete pits, which can 
be blended out using unpowered hand tools).
     Reworking corroded or corrosion-pitted components 
according to the Spline Rework procedures in Part 3 of the service 
bulletin if the damage is within specified limits.
     Replacing corroded or corrosion-pitted components having 
damage that is outside the specified limits with new or serviceable 
components.
     Replacing cracked or fractured components with new or 
serviceable components. (The service bulletin notes that, if one of the 
two fittings that make up the closeout rib fitting assembly or the 
carrier beam pillow block fitting assembly is replaced, both fittings 
that make up the assembly must be replaced at the same time.)
     Refinishing components as necessary.
    If spline rework is accomplished, the service bulletin also 
describes procedures for performing additional investigative actions 
that include:
     Evaluating the interfaces between the splined components 
using the Spline Rework Evaluation or the Preliminary Spline Rework 
Evaluation procedure, as applicable.
     Doing a magnetic particle inspection of the splined area 
for cracking.
     Doing a detailed inspection for corrosion or corrosion 
pitting to ensure complete removal of corrosion or corrosion pitting.
     Doing a detailed inspection for discoloration due to 
overheating, or a local surface temper etch inspection for other 
damage, that may have resulted from performing the rework procedures.
    The service bulletin specifies a compliance time for the initial 
inspection of 48 months after the date of issuance of the original 
Airworthiness Certificate or the date of issuance of the original 
Export Certificate of Airworthiness, or within 24 months after the date 
of Revision 1 of the service bulletin, whichever is later. The service 
bulletin specifies repeating the detailed inspections for any 
discrepancy of the splined components that support the inboard end of 
the inboard trailing edge flap within 5 years or 10 years, depending on 
the condition of the splined components. (Subsequent inspections are 
required at intervals not to exceed 5 years or 10 years, depending on 
the condition found during the repeat inspection.) If the criteria for 
Condition D are met during the initial inspection (as determined by the 
spline evaluation), a repeat inspection is required within 24 months. 
If the criteria for Condition C or D are met in a subsequent repeat 
inspection, the affected splined component must be replaced before 
further flight.
    Note (c) of Table 7, under paragraph 1.E., ``Compliance,'' of the 
service bulletin also specifies repetitively replacing the torque tube 
assembly with a new torque tube assembly, regardless of condition. The 
service bulletin specifies an initial compliance time for this 
replacement of either 18,000 or 20,000 total flight cycles on the 
airplane (depending on airplane group), or 24 months after the date of 
Revision 1 of the service bulletin, whichever is later. The repetitive 
interval for the replacement is either 18,000 or 20,000 flight cycles, 
depending on airplane group.

FAA's Determination and Requirements of the Proposed AD

    We have evaluated all pertinent information and identified an 
unsafe condition that is likely to exist or develop on other airplanes 
of this same type design. For this reason, we are proposing this AD, 
which would require accomplishing the actions specified in the service 
information described previously, except as discussed below under 
``Difference Between Proposed AD and Service Information.''

Difference Between Proposed AD and Service Information

    The service bulletin specifies compliance times relative to the 
date of issuance of the service bulletin; however, this proposed AD 
would require compliance before the specified compliance time after the 
effective date of this AD.

Clarification of Requirement To Replace Torque Tube Assembly

    As explained previously, Note (c) of Table 7, under paragraph 1.E., 
``Compliance,'' of the service bulletin specifies repetitively 
replacing the torque tube assembly with a new torque tube assembly, 
regardless of condition. However, this replacement of a torque tube 
assembly with no discrepancy is not specified in the Accomplishment 
Instructions of the service bulletin. Paragraph (k) of this proposed AD 
would require the repetitive replacement of the torque tube assembly at 
the schedule indicated in the Compliance section of the service 
bulletin.

Interim Action

    We consider this proposed AD interim action. The manufacturer is 
currently developing a new, improved torque tube that will be made from 
corrosion-resistant steel and have thicker walls. Installing this new, 
improved torque tube is expected to address the unsafe condition 
identified in this proposed AD and eliminate the need for the 
repetitive inspections and torque tube assembly replacements that would 
be required by this proposed AD. Once the improved torque tube is 
developed, approved, and available, we may consider additional 
rulemaking to require installing it.

Costs of Compliance

    There are about 353 airplanes of the affected design in the 
worldwide fleet. The following table provides the estimated costs for 
U.S. operators to comply with this proposed AD, at an average labor 
rate of $65 per work hour.

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                 Number of U.S.-
            Action                Work hours         Parts          Cost per       registered       Fleet cost
                                                                    airplane        airplanes
----------------------------------------------------------------------------------------------------------------
Detailed inspection for        20..............  None.........  $1,300, per                 132  $171,600, per
 discrepancies of the splined                                    inspection                       inspection
 components.                                                     cycle.                           cycle.
Modification (Installing       Negligible......  $17,156......  $17,156........             132  $2,264,592.
 isolation strap and
 hardware).

[[Page 6690]]

 
Replacement of torque tube     Negligible \1\..  $24,230......  $24,230........             132  $3,198,360, per
 assembly.                                                                                        replacement
                                                                                                  cycle.
----------------------------------------------------------------------------------------------------------------
\1\ Provided that the replacement is performed at the same time as a scheduled inspection.

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 
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 
adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2006-23842; Directorate Identifier 2005-NM-
145-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by March 27, 
2006.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 777-200 and -300 series 
airplanes, certificated in any category, as identified in Boeing 
Service Bulletin 777-57A0048, Revision 1, dated June 9, 2005.

Unsafe Condition

    (d) This AD results from reports of corrosion on the torque tube 
and closeout rib fittings that support the inboard end of the 
inboard trailing edge flap, as well as a structural reassessment of 
the torque tube joint that revealed the potential for premature 
fatigue cracking of the torque tube that would not be detected using 
reasonable inspection methods. We are issuing this AD to detect and 
correct corrosion or cracking of the torque tube and closeout rib 
fittings that support the inboard end of the inboard trailing edge 
flap. Cracking in these components could lead to a fracture, which 
could result in loss of the inboard trailing edge flap and 
consequent reduced controllability 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.

Service Bulletin Reference

    (f) The term ``service bulletin,'' as used in this AD, means 
Boeing Service Bulletin 777-57A0048, Revision 1, dated June 9, 2005.
    (g) Where the service bulletin specifies a compliance time after 
the issuance of the service bulletin, this AD requires compliance 
within the specified compliance time after the effective date of 
this AD.

Initial Inspection

    (h) Do a detailed inspection for any discrepancy of the splined 
components of the inboard trailing edge flap, in accordance with the 
Accomplishment Instructions of the service bulletin. The splined 
components of the inboard trailing edge flap include the torque 
tube, closeout rib fitting assembly, carrier beam pillow block 
fitting assembly, and drive crank support. Discrepancies of the 
torque tube and closeout rib fitting include light contact wear, 
corrosion pits, corrosion, cracking, or fracture. Discrepancies of 
the carrier beam pillow block fitting assembly and drive crank 
support consist of light contact wear and damage to the cadmium 
plating. Do the initial inspection at the applicable time specified 
in Table 7 under paragraph 1.E., ``Compliance,'' of the service 
bulletin, except as provided by paragraph (g) of this AD.

No Discrepancy/Other Specified Actions

    (i) If no discrepancy is found, perform all applicable specified 
actions, including the modification to install a new isolation strap 
and attachment hardware, in accordance with the Accomplishment 
Instructions of the service bulletin. Then, repeat the inspection at 
the applicable time specified in Table 7 under paragraph 1.E., 
``Compliance,'' of the service bulletin.

Related Investigative/Corrective/Other Specified Actions and Repetitive 
Inspections

    (j) For any discrepancy found during any inspection required by 
this AD: Before further flight, accomplish all applicable 
investigative, corrective, and other specified actions, including 
the modification to install a new isolation strap and attachment 
hardware, in accordance with the Accomplishment Instructions of the 
service bulletin. Then, evaluate the spline rework to determine the 
appropriate repetitive interval, in accordance with the 
Accomplishment Instructions of the service bulletin. Thereafter, 
repeat the inspection at the applicable interval specified in Table 
7 under paragraph 1.E., ``Compliance,'' of the service bulletin.

Replacement of Torque Tube Assembly

    (k) Replace the torque tube assembly with a new torque tube 
assembly, in accordance

[[Page 6691]]

with the Accomplishment Instructions of the service bulletin. Do the 
initial replacement at the applicable compliance time specified in 
Notes (c) and (d), as applicable, of Table 7 in paragraph 1.E., 
``Compliance,'' of the service bulletin, except as provided by 
paragraph (g) of this AD. Repeat the replacement thereafter at the 
applicable interval specified in Notes (c) and (d), as applicable, 
of Table 7 under paragraph 1.E., ``Compliance,'' of the service 
bulletin.

Alternative Methods of Compliance (AMOCs)

    (l)(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) Before using any AMOC approved in accordance with Sec.  
39.19 on any airplane to which the AMOC applies, notify the 
appropriate principal inspector in the FAA Flight Standards 
Certificate Holding District Office.
    (3) 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.

    Issued in Renton, Washington, on January 31, 2006.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E6-1767 Filed 2-8-06; 8:45 am]
BILLING CODE 4910-13-P