[Federal Register Volume 70, Number 193 (Thursday, October 6, 2005)]
[Proposed Rules]
[Pages 58358-58361]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 05-20077]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2005-22629; Directorate Identifier 2005-NM-089-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-200, -300, -400, and -
500 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 adopt a new airworthiness directive (AD) 
for certain Boeing Model 737-200, -300, -400, and -500 series 
airplanes. This proposed AD would require a one-time inspection of 
frames between station 360 and station 907 to determine if a subject 
support bracket for the air conditioning outlet extrusion is installed, 
and related repetitive investigative actions and repair if necessary. 
This proposed AD also provides an optional preventive modification that 
would end the repetitive investigative actions. This proposed AD would 
also require a one-time post-modification/repair inspection for 
cracking of each repaired/modified frame. This proposed AD results from 
numerous reports indicating that frame cracks have been found at the 
attachment holes for support brackets for the air conditioning outlet 
extrusion. We are proposing this AD to detect and correct such 
cracking, which, if the cracking were to continue to grow, could result 
in a severed frame. A severed frame, combined with existing multi-site 
damage at the stringer 10 lap splice, could result in rapid 
decompression of the airplane.

DATES: We must receive comments on this proposed AD by November 21, 
2005.

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: Sue Lucier, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
917-6438; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to submit any relevant written data, views, or 
arguments regarding this proposed AD. Include the docket number ``FAA-
2005-22629; Directorate Identifier 2005-NM-089-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 numerous reports indicating that frame cracks have 
been found at the attachment holes for support brackets for the air 
conditioning outlet extrusion on Boeing Model 737-200, -300, -400, and 
-500 series airplanes. The subject support brackets have a certain part 
number and are attached to the frame with two rivets. Subject support 
brackets may be installed on frames between station 360 and station 
907. Investigation has revealed that the frame cracks occur due to 
fatigue and grow in a circumferential direction. The circumferential 
growth of the cracks is not likely to lead to a severed frame; however, 
with continued fatigue cycling, a crack could potentially turn in a 
direction that would lead to a severed frame. Also, frame cracks have 
been found on multiple adjacent frames, and at the lower row of 
fasteners of the stringer 10 lap joint, which is susceptible to multi-
site damage. Therefore, frame cracks at the attachment holes for the 
support bracket of the air conditioning outlet extrusion, if not 
corrected, could eventually lead to a severed frame, which, combined 
with existing multi-site damage at the stringer 10 lap splice, could 
result in rapid decompression of the airplane.

Relevant Service Information

    We have reviewed Boeing Special Attention Service Bulletin 737-53-
1216, dated January 27, 2005. Part I of the service bulletin describes 
procedures for a general visual inspection to identify where subject 
support brackets (defined previously) may be installed on frames 
between station 360 and station 907. Part I of the

[[Page 58359]]

service bulletin also describes procedures for related investigative 
actions following identification of subject support brackets. The 
related investigative actions consist of a medium-frequency eddy 
current (MFEC) inspection for cracking of the frame around the 
attachment rivets of the support bracket, and a high-frequency eddy 
current (HFEC) inspection for cracking of the frame adjacent to the 
inboard fastener hole.
    For any subject support bracket on which no cracking is found, the 
service bulletin specifies to perform these inspections repetitively, 
or to do a preventive modification. Part II of the service bulletin 
describes procedures for the preventive modification, which involves 
performing an open-hole HFEC inspection of the frame holes for the 
support bracket, and repairing any cracks in accordance with the repair 
procedures (in Part III of the service bulletin). If no crack is found 
during the inspection of the frame holes, the modification procedures 
involve installing a doubler and cold-working fastener holes, as 
applicable.
    For any subject frame on which cracking is found, Part III of the 
service bulletin specifies procedures for repair. The repair involves 
cutting out the frame web, doing a dye penetrant or HFEC inspection of 
the cutout to ensure it is free from cracks, installing repair angles, 
and cold working fastener holes as applicable.
    Part IV of the service bulletin describes procedures for performing 
a one-time post-repair/modification inspection of any modified or 
repaired frame, which involves the following:
     Performing a detailed inspection for cracking of the 
modification doubler or repair angle, as applicable.
     Performing a detailed inspection for cracking of the 
frame, two stringers above and two stringers below the support bracket.
     Performing a detailed inspection for cracking of the air 
conditioning attach brackets.
     Performing a detailed inspection for cracking of the frame 
at the stringer clips.
     Reporting any cracking to Boeing.
    Accomplishing the general visual inspection, repetitive MFEC and 
HFEC inspections, and any necessary corrective actions specified in the 
service information is intended to adequately address the unsafe 
condition.
    Section 1.E., Compliance, of the service bulletin specifies 
compliance times for the actions in the service bulletin. The service 
bulletin specifies that the initial general visual, MFEC, and HFEC 
inspections, as applicable, are required prior to the accumulation of 
30,000 total flight cycles, or within 5,000 flight cycles after the 
date of the service bulletin (or after a frame repair was made), 
whichever occurs later. The service bulletin specifies a repetitive 
interval (for all subject frames) of 6,000 flight cycles.

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 Service Information.'' If no 
cracking is found, this proposed AD would also provide for optional 
accomplishment of the preventive modification, which would end the 
repetitive inspections for each modified frame.
    Consistent with the service information, the proposed AD would 
allow repetitive inspections to continue in lieu of the preventive 
modification for any frame on which no cracking is found. In making 
this determination, we considered that long-term continued operational 
safety in this case will be adequately ensured by repetitive 
inspections to detect cracking before it represents a hazard to the 
airplane.

Differences Between the Proposed AD and Service Information

    Part IV of the Accomplishment Instructions of the referenced 
service bulletin does not specify what corrective action is necessary 
if cracking is found during a post-modification/repair inspection. We 
find that any cracking found during a post-modification/repair 
inspection must be repaired 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.
    Also, Part IV of the Accomplishment Instructions of the referenced 
service bulletin specifies reporting to Boeing any damage found during 
the post-modification/repair inspections. This proposed AD would not 
require that action. We do not need this information from operators.
    The service bulletin specifies a compliance time relative to the 
date of the service bulletin; however, this proposed AD would require 
compliance before the specified compliance time after the effective 
date of this AD.

Costs of Compliance

    There are about 2,131 airplanes of the affected design in the 
worldwide fleet. This proposed AD would affect about 938 airplanes of 
U.S. registry. The proposed inspection to identify subject support 
brackets, and subsequent MFEC and HFEC inspections would take about 2 
work hours per frame, with approximately 32 to 45 frames to be 
inspected per airplane, at an average labor rate of $65 per work hour. 
Based on these figures, the estimated cost of the proposed AD for U.S. 
operators is between $3,902,080 and $5,487,300, or between $4,160 and 
$5,850 per airplane.
    The following table provides the estimated costs for U.S. operators 
to comply with the inspections of each frame for cracking, the 
preventive modification, and the repair specified in this proposed AD, 
at an average labor rate of $65 per work hour. Note that the estimated 
cost specified in the table is per frame, not per airplane, as it is 
unknown how many frames on each airplane will have a subject bracket 
installed.

                                          Estimated On-Condition Costs
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                                                                                                       Cost per
                  Action                    Work  hours                     Parts                       frame
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Preventive modification...................            4  Operator-provided.........................         $260
Repair....................................            6  $608......................................          998
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[[Page 58360]]

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-2005-22629; Directorate Identifier 2005-NM-
089-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by November 
21, 2005.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 737-200, -300, -400, and -
500 series airplanes; certificated in any category; as identified in 
Boeing Special Attention Service Bulletin 737-53-1216, dated January 
27, 2005.

Unsafe Condition

    (d) This AD results from numerous reports indicating that frame 
cracks have been found at the attachment holes for support brackets 
for the air conditioning outlet extrusion. We are issuing this AD to 
detect and correct such cracking, which, if the cracking were to 
continue to grow, could result in a severed frame. A severed frame, 
combined with existing multi-site damage at the stringer 10 lap 
splice, could result in rapid decompression 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.

Inspection To Determine Subject Support Brackets

    (f) Perform a one-time general visual inspection to identify 
subject support brackets for the air conditioning outlet extrusion 
installed on frames between station 360 and station 907, in 
accordance with Part I of the Accomplishment Instructions of Boeing 
Special Attention Service Bulletin 737-53-1216, dated January 27, 
2005. Subject support brackets have part number 65C27021-() and are 
attached to the frame with two rivets. Do this inspection at the 
applicable time specified in paragraph 1.E., ``Compliance,'' of the 
service bulletin, except, 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.

Repetitive Inspections for Cracking

    (g) For each frame with a subject support bracket identified 
during the inspection in accordance with paragraph (f) of this AD: 
Perform a medium-frequency eddy current inspection for cracking of 
the frame around the attachment rivets of the support bracket, and a 
high-frequency eddy current (HFEC) inspection for cracking of the 
frame adjacent to the inboard fastener hole, by doing all the 
actions specified in and in accordance with Part I of the 
Accomplishment Instructions of Boeing Special Attention Service 
Bulletin 737-53-1216, dated January 27, 2005, except for paragraph 
3.B.2. of Part I (which was already done in accordance with 
paragraph (f) of this AD). Do the initial inspections at the 
applicable time specified in paragraph 1.E., ``Compliance,'' of the 
service bulletin, except, 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. If no cracking is found, repeat the 
inspections thereafter at intervals not to exceed the repeat 
interval specified in paragraph 1.E., ``Compliance,'' of the service 
bulletin, until paragraph (h) or (i) of this AD is done.

Repair

    (h) For any frame in which cracking is found during any 
inspection required by paragraph (g) of this AD: Before further 
flight, repair the cracking by doing all applicable actions in 
accordance with Part III of the Accomplishment Instructions of 
Boeing Special Attention Service Bulletin 737-53-1216, dated January 
27, 2005. Then, do paragraph (j) of this AD, at the time specified 
in that paragraph. Doing this repair ends the repetitive inspections 
required by paragraph (g) of this AD for each modified frame.

Optional Preventive Modification

    (i) For any frame on which a subject bracket is installed: Doing 
all actions associated with the preventive modification in 
accordance with Part II of the Accomplishment Instructions of Boeing 
Special Attention Service Bulletin 737-53-1216, dated January 27, 
2005, ends the repetitive inspections required by paragraph (g) of 
this AD for each modified frame. Do the requirements of paragraph 
(j) of this AD on each modified frame at the time specified in that 
paragraph.

Post-Modification/Repair Inspection

    (j) For each frame repaired or modified in accordance with 
paragraph (h) or (i) of this AD, as applicable: Within 24,000 flight 
cycles after doing the modification/repair, but after a minimum of 
18,000 flight cycles after doing the modification/repair, do one-
time detailed inspections for cracking of the repaired/modified 
frame, air conditioning attach brackets, and stringer clips, by 
doing all actions in accordance with Part IV of the Accomplishment 
Instructions of Boeing Special Attention Service Bulletin 737-53-
1216, dated January 27, 2005. If any cracking is found during the 
post-modification/repair inspection, before further flight, repair 
the cracking using a method approved in accordance with paragraph 
(k) of this AD.

Alternative Methods of Compliance (AMOCs)

    (k)(1) The Manager, Seattle ACO, has the authority to approve 
AMOCs for this AD, if requested in accordance with the procedures 
found in 14 CFR 39.19.
    (2) 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

[[Page 58361]]

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.
    (3) Before using any AMOC approved in accordance with 14 CFR 
39.19 on any airplane to which the AMOC applies, notify the 
appropriate principal inspector in the FAA Flight Standards 
Certificate Holding District Office.

    Issued in Renton, Washington, on September 28, 2005.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 05-20077 Filed 10-5-05; 8:45 am]
BILLING CODE 4910-13-P