[Federal Register Volume 71, Number 71 (Thursday, April 13, 2006)]
[Proposed Rules]
[Pages 19144-19148]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-5469]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2006-24432; Directorate Identifier 2005-NM-227-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100, -200, and -200C 
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 737 series 
airplanes. The existing AD currently requires inspection of the 
elevator tab inboard hinge support structure to detect fatigue cracking 
and corrective action if necessary. That AD also provides an optional 
terminating action. This proposed AD would add airplanes to the 
applicability and would require new repetitive inspections. For 
airplanes having elevators with laminated rear spars, this proposed AD 
would require repetitive inspections for interlaminar corrosion, 
delamination, or disbonding in the rear spar, repetitive inspections 
for cracking in the spar web, and repair including related 
investigative/corrective actions if necessary. For airplanes having 
elevators with solid rear spars, this proposed AD would require 
repetitive inspections for cracking in the spar web and repair 
including related investigative/corrective actions if necessary. This 
proposed AD results from reports of cracks in the elevator rear spar 
web at the tab hinge bracket locations. We are proposing this AD to 
detect and correct cracking, corrosion, interlaminar corrosion, 
delamination, and disbonding in the elevator rear spar, which may 
reduce elevator stiffness and lead to in-flight vibration. In-flight 
vibration may lead to elevator and horizontal stabilizer damage and 
reduced controllability of the airplane.

DATES: We must receive comments on this proposed AD by May 30, 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 service information identified in this 
proposed AD.

FOR FURTHER INFORMATION CONTACT: Nancy Marsh, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
917-6440; 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 ``Docket No. 
FAA-2006-24432; Directorate Identifier 2005-NM-227-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 the DOT's complete Privacy Act Statement in the 
Federal Register published on April 11, 2000 (65 FR 19477-78), or can 
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

[[Page 19145]]

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

    On June 7, 1989, we issued AD 76-11-05 R1, amendment 39-6234 (54 FR 
25709, June 19, 1989), for certain Boeing Model 737 series airplanes. 
That AD requires repetitive inspections of the elevator tab inboard 
hinge support structure to detect fatigue cracking and corrective 
action if necessary. That AD also provides an optional terminating 
action. That AD resulted from the determination that additional 
airplanes were manufactured to the same design as airplanes identified 
in AD 76-11-05 and are subject to the same failure. We issued that AD 
to detect fatigue cracking, which could result in vibration and 
possible flutter.

Other Relevant Rulemaking

    On January 16, 1990, we issued AD 90-06-02, amendment 39-6489 (55 
FR 8372, March 7, 1990), applicable to certain Boeing Model 737 series 
airplanes, which would require incorporation of certain structural 
modifications. That AD refers to Boeing Document D6-38505, Revision C, 
dated December 11, 1989, ``Aging Airplane Service Bulletin Structural 
Modification Program--Model 737-100/-200/-200C,'' which references 
Boeing Service Bulletins 737-55A1020 and 737-55-1022 for certain 
modifications. We issued that AD to prevent structural failure.

Actions Since Existing AD Was Issued

    Since we issued AD 76-11-05 R1, we have received reports of cracks 
in the elevator rear spar web at the tab hinge bracket locations, on 
Model 737-100, -200, and -200C series airplanes. These airplanes had 
6,100 to 56,000 total flight hours and 2,400 to 66,000 total flight 
cycles. Some airplanes had modifications and repairs done in accordance 
with Boeing Service Bulletins 737-55A1020 and 737-55-1022. 
Accomplishing the actions specified in Section III, Part II, including 
installation of the bolt retainer clips, of Boeing Alert Service 
Bulletin 737-55A1020, Revision 1, dated August 20, 1976; Revision 2, 
dated February 11, 1977; or Revision 3, dated December 22, 1988; or the 
preventive modification specified in Section III, Part II of Boeing 
Service Bulletin 737-55-1022, dated April 15, 1977; are terminating 
action for AD 76-11-05 R1 and required modifications for AD 90-06-02, 
amendment 39-6489. Because cracking has continued to occur, the actions 
described in Boeing Service Bulletins 737-55A1020 and 737-55-1022 do 
not eliminate the need for repetitive inspections for cracking.
    Analysis shows that the cracks in the elevator rear spar web are 
caused by deflection stresses. Excessive web cracking at multiple 
locations will reduce the elevator support stiffness. The reduced 
stiffness will lead to in-flight vibrations and consequent damage to 
the elevator and horizontal stabilizer. This condition, if not 
corrected, could result in reduced controllability of the airplane.

Relevant Service Information

    We have reviewed Boeing Alert Service Bulletin 737-55A1078, dated 
October 27, 2005, which replaces Boeing Service Bulletins 737-55A1020 
and 737-55-1022. Boeing Alert Service Bulletin 737-55A1078 is 
referenced as the appropriate source of service information for doing 
the actions in this proposed AD.
    Appendix A of Boeing Alert Service Bulletin 737-55A1078 describes 
procedures for determining the elevator configuration number or 
elevator group number of the rear spar. The number indicates if 
elevators have laminated rear spars or solid rear spars, as well as 
other configuration differences.
    For airplanes having elevators with laminated rear spars, the alert 
service bulletin describes procedures for repetitive detailed 
inspections for cracking at hinge bracket locations and for 
interlaminar corrosion of the rear spar as specified in Part I of the 
Accomplishment Instructions. For airplanes having elevators with 
laminated rear spars, the alert service bulletin also describes 
procedures for repetitive detailed and special detailed inspections for 
interlaminar corrosion, delamination, and disbonding of the rear spar 
as specified in Part III of the Accomplishment Instructions.
    For airplanes having elevators with solid rear spars, the alert 
service bulletin describes procedures to do repetitive detailed 
inspections for cracking at the hinge bracket locations in the spar web 
as specified in Part II of the Accomplishment Instructions.
    For all airplanes, if no cracking or interlaminar corrosion is 
found during any inspection, the alert service bulletin specifies to 
install a hinge bolt retainer clip if necessary.
    For all airplanes, if any interlaminar corrosion or cracking is 
found during any inspection, the alert service bulletin specifies to do 
applicable repairs including related investigative actions and 
corrective actions as specified in Parts IV through VIII (Interim 
Repair Options A through D) and Part IX (Time-limited Repair) of the 
Accomplishment Instructions. Appendix C of the alert service bulletin 
describes how to determine which interim repair option and time-limited 
repair can be used. The service bulletin describes the repairs, 
including related investigative and corrective actions, as follows:
     Part IV--Option A Interim Repair--Spar Splice: The spar 
splice repair consists of removal of a cracked segment or segments of 
the elevator rear spar and installation of a new replacement spar 
segment or segments. The repair includes inspecting holes for signs of 
loose or damaged fasteners, repair if necessary, and contacting the 
manufacturer for certain repair instructions. The repair also includes 
making sure balancing requirements are met for the elevator and the tab 
after the corrective actions are done.
     Parts V and VI--Option B or D Interim Repair--Spar 
Replacement Without Replacement of Thin Tee Clips with Thick Tee Clips 
(for certain elevator configurations): The Option B or D spar 
replacements consist of removal of the hinge brackets and rear spar 
ribs from the spar, removal of the existing spar, installation of a new 
replacement spar, and reinstallation of the hinge brackets and rear 
spar ribs to the new spar. These spar replacement options include 
inspecting holes for signs of loose or damaged fasteners, repair if 
necessary, and contacting the manufacturer for certain repair 
instructions. These spar replacement options also include making sure 
balancing requirements are met for the elevator and the tab after the 
corrective actions are done.
     Parts VII and VIII--Option C Interim Repair--Spar 
Replacement With Replacement of Thin Tee Clips with Thick Tee Clips 
(for certain elevator configurations): The Option C spar replacement 
consists of removal of the hinge brackets, rear spar ribs, and thin tee 
clips from the spar, removal of the existing spar, installation of a 
new replacement spar and thick tee clips, and reinstallation of the 
hinge brackets and rear spar ribs to the new spar. This replacement 
option includes inspecting holes for signs of loose or damaged 
fasteners, repairing if necessary, and contacting the manufacturer for 
certain repair instructions. This replacement

[[Page 19146]]

option also includes making sure balancing requirements are met for the 
elevator and tab after the corrective actions are done.
     Part IX--Time-limited Repair: The repair consists of 
installation of repair components and an eddy current inspection for 
crack containment at the stop-drilled hole. The repair instructions 
include contacting the manufacturer if any crack is outside the limit 
specified in the alert service bulletin. The repair also includes 
making sure balancing requirements are met for the elevator and tab 
after the corrective actions are done. If the time-limited repair is 
done, the alert service bulletin specifies that the Option A or D 
interim repair must done within 24 months, 2,000 flight hours, or 1,500 
flight cycles, whichever occurs first, after the time-limited repair is 
done.
    The alert service bulletin specifies the following compliance times 
for doing the inspections in paragraph 1.E. Compliance and Appendix B 
of the alert service bulletin:
     Part I Initial Inspection: Within 1,000 flight hours or 
750 flight cycles after the release date of the alert service bulletin, 
whichever occurs first; or within 2,000 flight hours or 1,500 flight 
cycles after the release date of the alert service bulletin, whichever 
occurs first; depending on elevator group number/configuration number.
     Part I Repetitive Inspections: At intervals not to exceed 
1,000 flight hours or 750 flight cycles, whichever occurs first; or at 
intervals not to exceed 2,000 flight hours or 1,500 flight cycles, 
whichever occurs first; depending on elevator group number/
configuration number.
     Part II Initial Inspection: Within 1,000 flight hours or 
750 flight cycles after the release date of the alert service bulletin, 
whichever occurs first; or 2,000 flight hours or 1,500 flight cycles 
after the release date of the alert service bulletin, whichever occurs 
first; or 24,000 flight hours or 18,000 flight cycles, whichever occurs 
first, on the elevator since new or since the modification specified in 
Boeing Service Bulletin 737-55-1022 has been done, provided it can be 
positively determined from the operator's records; depending on 
elevator group number/configuration number.
     Part II Repetitive Inspections: At intervals not to exceed 
6,000 flight hours or 4,500 flight cycles, whichever occurs first; or 
at intervals not to exceed 1,000 flight hours or 750 flight cycles, 
whichever occurs first; depending on elevator group number/
configuration number. For certain elevators, accomplishing any Option C 
or Option D interim repairs defers the accomplishment of the next Part 
II inspection to within 24,000 flight hours or 18,000 flight cycles 
since the repair.
     Part III Initial Inspection: Within 1,000 flight hours or 
750 flight cycles, whichever occurs first; or within 2,000 flight hours 
or 1,500 flight cycles, whichever occurs first; depending on elevator 
group number/configuration number.
     Part III Repetitive Inspections: At intervals not to 
exceed 8,000 flight hours or 6,000 flight cycles, whichever occurs 
first.
    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 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 under 
``Differences Between the Proposed AD and the Alert Service Bulletin.''

Differences Between the Proposed AD and the Alert Service Bulletin

    The alert service bulletin specifies to contact the manufacturer 
for instructions on how to repair certain conditions, but this proposed 
AD would require repairing those conditions in one of the following 
ways:
     Using a method that we approve; or
     Using data that meet the certification basis of the 
airplane, and that have been approved by an Authorized Representative 
for the Boeing Commercial Airplanes Delegation Option Authorization 
Organization whom we have authorized to make those findings.
    Where Table B.4 in Appendix B of the alert service bulletin 
specifies a compliance time in flight hours or flight cycles, this 
proposed AD would require the actions specified in Table B.4 be done at 
the earlier of the compliance times in flight hours or flight cycles.

Clarification of Inspection and Corrective Action

    Operators should note that step 3. of Part III of the alert service 
bulletin specifies to do a special detailed inspection for spar 
interlaminar corrosion as given in Figure 3. Figure 3 specifies to do a 
detailed inspection for corrosion and disbonding and a special detailed 
inspection for interlaminar corrosion and delamination. Thus, in Part 
III of the alert service bulletin, operators must inspect for 
interlaminar corrosion, delamination, and disbonding.
    Operators should note that Figure 3 of the alert service bulletin 
also specifies that a spar should be rejected if interlaminar 
corrosion, delamination, or disbonding is found. However, step 3.a. of 
Part III of the alert service bulletin only specifies that if 
interlaminar corrosion is found, spar replacement is required in 
accordance with Appendix C; step 3.C. of Appendix C of the alert 
service bulletin specifies that for laminated spars that have 
interlaminar corrosion, only repair options B, C, and D are permitted. 
Step 3.a. of Part III of the alert service bulletin and step 3.C. of 
Appendix C of the alert service bulletin do not specify what to do if 
delamination or disbonding is found.
    Step 3.a. of Part III of the alert service bulletin should have 
specified that spar replacement is required if interlaminar corrosion, 
delamination, or disbonding is found. Step 3.C. of Appendix C of the 
alert service bulletin should have specified that for laminated spars 
that have interlaminar corrosion, delamination, or disbonding, only 
repair options B, C, and D are permitted. We have included this 
clarification in paragraph (o) of this proposed AD.

Explanation of Change to Applicability

    We have revised the applicability of the existing AD to identify 
model designations as published in the most recent type certificate 
data sheet for the affected models.

Correction of Typographical Error for Service Bulletin Date

    AD 76-11-05 R1 referred to Boeing Service Bulletin 737-55-1022, 
Section III, Part II, dated April 15, 1987. However, the service 
bulletin is dated April 15, 1977. We have fixed this typographical in 
the service bulletin reference in this proposed AD.

Change to Existing AD

    This proposed AD would retain certain requirements of AD 76-11-05 
R1. Since AD 76-11-05 R1 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:

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                      Revised Paragraph Identifiers
------------------------------------------------------------------------
                                            Corresponding requirement in
       Requirement in AD 76-11-05 R1              this proposed AD
------------------------------------------------------------------------
Paragraph B...............................  paragraph (f).
Paragraph C...............................  paragraph (g).
Paragraph D...............................  paragraph (h).
------------------------------------------------------------------------

Costs of Compliance

    There are about 1,355 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.

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                 Number of U.S.-
            Action               Work hours     Average labor      Cost per        registered       Fleet cost
                                                rate per hour      airplane         airplanes
----------------------------------------------------------------------------------------------------------------
Inspection, per inspection             10-100             $80  $800-$8,000, per             230  $184,000-$1,840
 cycle.                                                         inspection                        ,000, per
                                                                cycle.                            inspection
                                                                                                  cycle.
----------------------------------------------------------------------------------------------------------------

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 
removing amendment 39-6234 (54 FR 25709, June 19, 1989) and adding the 
following new airworthiness directive (AD):

Boeing: Docket No. FAA-2006-24432; Directorate Identifier 2005-NM-
227-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by May 30, 
2006.

Affected ADs

    (b) This AD supersedes AD 76-11-05 R1.

Applicability

    (c) This AD applies to Boeing Model 737-100, -200, and -200C 
series airplanes, certificated in any category; as identified in 
Boeing Alert Service Bulletin 737-55A1078, dated October 27, 2005.

Unsafe Condition

    (d) This AD results from reports of cracks in the elevator rear 
spar web at the tab hinge bracket locations. We are issuing this AD 
to detect and correct cracking, corrosion, interlaminar corrosion, 
delamination, and disbonding in the elevator rear spar, which may 
reduce elevator stiffness and lead to in-flight vibration. In-flight 
vibration may lead to elevator and horizontal stabilizer damage and 
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.

Restatement of Certain Requirements of AD 76-11-05 R1

    (f) For Model 737-100, -200, and -200C series airplanes, line 
number 001 through 491 inclusive: Within the next 300 hours time-in-
service after July 24, 1989 (the effective date of AD 76-11-05 R1), 
unless accomplished within the last 700 hours time-in-service, and 
at intervals thereafter not to exceed 1,000 hours time-in-service, 
conduct the inspection required by paragraph (g) of this AD. 
Accomplishing the initial inspections specified in paragraph (j) of 
this AD terminates the requirements of this paragraph.
    (g) For Model 737-100, -200, and -200C series airplanes, line 
number 001 through 491 inclusive: At the times specified in 
paragraph (f) of this AD, inspect for excessive deflection of the 
elevator tab, right and left hand, in accordance with the inspection 
procedures specified in Section III, Part I, paragraphs C. and D., 
of Boeing Alert Service Bulletin 737-55A1020, Revision 1, dated 
August 20, 1976; Revision 2, dated February 11, 1977; or Revision 3, 
dated December 22, 1988. If the elevator tab-to-elevator relative 
deflection exceeds 1/10 inch, prior to further flight, modify the 
elevator in accordance with paragraph (h) of this AD. Accomplishing 
the initial inspections specified in paragraph (j) of this AD 
terminates the requirements of this paragraph.
    (h) For Model 737-100, -200, and -200C series airplanes, line 
number 001 through 491 inclusive: Installation of one of the 
modifications specified in Boeing Alert Service Bulletin 737-
55A1020, Revision 1, dated August 20, 1976; Revision 2, dated 
February 11, 1977; or Revision 3, dated December 22, 1988; Section 
III, Part II, including installation of the bolt retainer clips or 
the preventive modification specified in Boeing Service Bulletin 
737-55-1022, Section III, Part II, dated April 15, 1977; is 
considered terminating action for the

[[Page 19148]]

inspection requirements of paragraph (g) of this AD.

New Requirements of This AD

Determine Elevator Group Number or Elevator Configuration Number

    (i) Within 1,000 flight hours or 750 flight cycles after the 
effective date of this AD, whichever occurs first, determine the 
elevator group number or the elevator configuration number in 
accordance with Appendix A of Boeing Alert Service Bulletin 737-
55A1078, dated October 27, 2005.

Initial and Repetitive Inspections

    (j) At the applicable time specified in Tables 2 and 3 of 
paragraph 1.E. ``Compliance'' of Boeing Alert Service Bulletin 737-
55A1078, dated October 27, 2005, except where the alert service 
bulletin specifies a compliance time from the release date of the 
alert service bulletin, this AD requires the compliance time after 
the effective date of this AD: Do the applicable initial detailed 
and special detailed inspections for interlaminar corrosion, 
cracking, delamination, or disbonding in the rear spar by doing all 
the applicable actions specified in Parts I, II, and III of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
55A1078, dated October 27, 2005; except where step 3. of Part III of 
the alert service bulletin specifies to do a special detailed 
inspection for spar interlaminar corrosion as given in Figure 3, 
this AD requires all actions specified in Figure 3 to be done (a 
detailed inspection for interlaminar corrosion and disbonding and a 
special detailed inspection for interlaminar corrosion and 
delamination). Doing the initial inspections terminates the 
requirements of paragraphs (f) and (g) of this AD.
    (k) Repeat the inspections specified in paragraph (j) of this AD 
at the applicable time specified in Tables 4 and 5 of paragraph 1.E. 
``Compliance'' of Boeing Alert Service Bulletin 737-55A1078, dated 
October 27, 2005; except where Table B.4 in Appendix B of the alert 
service bulletin specifies compliance times in flight hours or 
flight cycles, this AD requires the actions specified in Table B.4 
be done at the earlier of the compliance times in flight hours or 
flight cycles.

Corrective Actions

    (l) If any interlaminar corrosion, cracking, delamination, or 
disbonding is found during any inspection required by this AD: 
Before further flight, use Appendix C of Boeing Alert Service 
Bulletin 737-55A1078, dated October 27, 2005, to determine the 
permitted repairs, and do the applicable repair, including related 
investigative and corrective actions, by doing all the applicable 
actions specified in Parts IV through VIII (Interim Repairs) and 
Part IX (Time-limited Repair) of the Accomplishment Instructions of 
the alert service bulletin, except as provided by paragraphs (n) and 
(o) of this AD.
    (m) If the time-limited repair specified in Part IX of the alert 
service bulletin is done: At the time specified in Table 6 of 
paragraph 1.E. ``Compliance'' of Boeing Alert Service Bulletin 737-
55A1078, dated October 27, 2005, do the applicable repair, including 
related investigative and corrective actions, by doing all the 
applicable actions specified in Parts IV through VI (Interim 
Repairs). Thereafter, do the repetitive inspections specified in 
paragraph (k) of this AD.
    (n) Where Boeing Alert Service Bulletin 737-55A1078, dated 
October 27, 2005, specifies to contact the manufacturer for 
appropriate action for the inspar rib replacement or for more 
instructions if any crack is outside the limit specified in the 
service bulletin: Before further flight, repair in accordance with a 
method approved by the Manager, Seattle Aircraft Certification 
Office (ACO), FAA; or using a method approved in accordance with 
paragraph (p) of this AD.
    (o) Where step 3.a. of Part III of the alert service bulletin 
specifies that if interlaminar corrosion is found, spar replacement 
is required, this AD requires spar replacement if interlaminar 
corrosion, delamination, or disbonding is found. Where step 3.C. of 
Appendix C of the alert service bulletin specifies that for 
laminated spars that have interlaminar corrosion, only repair 
options B, C, and D are permitted, this AD specifies that for 
laminated spars that have interlaminar corrosion, delamination, or 
disbonding, only repair options B, C, and D are permitted.

Alternative Methods of Compliance (AMOCs)

    (p)(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, and the approval must specifically refer to this 
AD.
    (4) Accomplishing the Interim Repair Option C or D specified in 
the Accomplishment Instructions of Boeing Alert Service Bulletin 
737-55A1078, dated October 27, 2005, is an AMOC for the structural 
modification requirements specified in paragraph A of AD 90-06-02, 
amendment 39-6489, that are done in accordance with Boeing Service 
Bulletins 737-55A1020 or 737-55-1022 only. All provisions of AD 90-
06-02 that do not specifically reference these service bulletins 
remain fully applicable and must be complied with.
    (5) AMOCs approved previously in accordance with AD 76-11-05 R1, 
are approved as AMOCs for the corresponding provisions of paragraphs 
(f) through (h) of this AD.

    Issued in Renton, Washington, on April 3, 2006.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E6-5469 Filed 4-12-06; 8:45 am]
BILLING CODE 4910-13-P