E8-27163. Airworthiness Directives; Boeing Model 737-100, -200, -200C, -300, -400, and -500 Series Airplanes

AGENCY:

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

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. The existing AD currently requires repetitive inspections of the intercostal webs, attachment clips, and stringer splice channels for cracks; and corrective action if necessary. This proposed AD would reduce the repetitive inspection intervals from 25,000 flight cycles to 6,000 flight cycles, and expand the inspection area for Model 737-200C series airplanes to include the area aft of the forward entry door. This proposed AD results from additional reports of fatigue cracks. We are proposing this AD to detect and correct fatigue cracking of the intercostals on the forward and aft sides of the forward entry door, which could result in loss of the forward entry door and rapid decompression of the airplane.

DATES:

We must receive comments on this proposed AD by January 2, 2009.

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: [phone].
• 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 [phone]) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT:

Howard Hall, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone].

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-2008-1213; Directorate Identifier 2007-NM-092-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 September 16, 2005, we issued AD 2005-20-03, amendment 39-14296 (70 FR 56361, September 27, 2005) for certain Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. That AD requires repetitive inspections of the intercostal webs, attachment clips, and stringer splice channels for cracks; and corrective action if necessary. That AD resulted from reports of fatigue cracks on several Boeing Model 737-200 series airplanes. We issued that AD to detect and correct fatigue cracking of the intercostals on the forward and aft sides of the forward entry door, which could result in loss of the forward entry door and rapid decompression of the airplane.

Actions Since Existing AD Was Issued

Since we issued AD 2005-20-03, many operators have reported to Boeing over one hundred fatigue cracks at all doorstop and hinge support intercostals on both the forward and aft sides of the forward entry door. Operators have also reported cracks on several airplanes at multiple intercostal locations.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007. We referred to Boeing Special Attention Service Bulletin 737-53-1204, dated June 19, 2003, as the appropriate source of service information for accomplishing the actions required by AD 2005-20-03. Revision 1 reduces the repetitive inspection intervals from 25,000 flight cycles to 6,000 flight cycles for all areas.

Revision 1 also adds a new inspection for cracking in the intercostal area aft of the forward entry door for Boeing Model 737-200C series airplanes on which the intercostals on the aft side of the forward entry door were not inspected previously. (The original issue of the service bulletin specified inspections only of the forward area.)

The compliance thresholds aft of the door vary depending on whether actions have been previously accomplished in accordance with Part 1, Part 2, and Part 3 of Paragraph 3.B. of Boeing Special Attention Service Bulletin 737-53-1204, dated June 19, 2003.

• For airplanes on which the actions have been accomplished previously, the threshold specified in the service bulletin for the next corresponding action is 6,000 flight cycles after the date of the previous inspection, or 3,000 flight cycles after March 26, 2007 (the date of Revision 1 of the service bulletin), whichever occurs later.
• For airplanes on which the actions have not been accomplished previously, the threshold specified in the service bulletin for the initial inspection is 15,000 total flight cycles, or within 4,500 flight cycles from June 19, 2003 (the date of the initial release of the service bulletin), whichever occurs later.
• For all airplanes, the threshold for the initial inspection specified in Part 4 of Paragraph 3.B. of Revision 1 of the service bulletin is 15,000 total flight cycles, or within 4,500 flight cycles from March 26, 2007.

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 2005-20-03 and would retain the requirements of the existing AD. This proposed AD would also reduce the repetitive inspection intervals from 25,000 flight cycles to 6,000 flight cycles, and expand the inspection area for Boeing Model 737-200C series airplanes. This proposed AD would require accomplishing the actions specified in the service bulletin described previously, except as discussed under “Difference Between the Proposed AD and the Service Bulletin.”

Difference Between the Proposed AD and the Service Bulletin

The 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.

Costs of Compliance

There are about 3,132 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

Action	Work hours	Average labor rate per hour	Cost per airplane	Number of U.S.- registered airplanes	Fleet cost
Inspection of areas forward of the aft entry door (required by AD 2005-20-03)	2	$80	$160 per inspection cycle	876	$140,160 per inspection cycle.
Inspection of areas aft of the forward entry door for Model 737-200C series airplanes (new proposed action)	1	80	$80 per inspection cycle	19	$1,520 per 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
• Incorporation by reference
• 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.

§ 39.13

[Amended]

2. The Federal Aviation Administration (FAA) amends § 39.13 by removing amendment 39-14296 (70 FR 56361, September 27, 2005) and adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2008-1213; Directorate Identifier 2007-NM-092-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by January 2, 2009.

Affected ADs

(b) This AD supersedes AD 2005-20-03.

Applicability

(c) This AD applies to Model 737-100, -200, -200C, -300, -400, and -500 series airplanes, certificated in any category, as identified in Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007.

Unsafe Condition

(d) This AD results from reports of fatigue cracks. We are issuing this AD to detect and correct fatigue cracking of the intercostals on the forward and aft sides of the forward entry door, which could result in loss of the forward entry door and 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.

Initial Compliance Time

(f) For all Model 737-100, -200, -200C, -300, -400, and -500 series airplanes: Before the accumulation of 15,000 total flight cycles, or within 4,500 flight cycles after November 1, 2005 (the effective date of AD 2005-20-03), whichever occurs later: Do the inspections required by paragraphs (h) and (i) of this AD.

(g) For all Model 737-200C series airplanes: Before the accumulation of 15,000 total flight cycles, or within 4,500 flight cycles after the effective date of this AD, whichever occurs later: Do the inspection required by paragraph (j) of this AD.

Initial Inspection for Passenger Configuration Airplanes

(h) For Group 1 passenger airplanes identified in Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007: Perform a detailed inspection for cracking of the intercostal web, attachment clips, and stringer splice channels; and a high frequency eddy current inspection for cracking of the stringer splice channels located forward and aft of the forward entry door; and do all applicable corrective actions before further flight; in accordance with Parts 1 and 2 of the Work Instructions of Boeing Special Attention Service Bulletin 737-53-1204, dated June 19, 2003; or Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007. After the effective date of this AD, only Revision 1 may be used.

Initial Inspection for Cargo Configuration Airplanes (Forward of the Forward Entry Door)

(i) For Group 2 cargo airplanes identified in Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007: Perform a detailed inspection for cracking of the intercostal webs and attachment clips located forward of the forward entry door; and do all applicable corrective actions before further flight; in accordance with Part 3 of the Work Instructions of Boeing Special Attention Service Bulletin 737-53-1204, dated June 19, 2003, or Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007. After the effective date of this AD, only Revision 1 may be used.

Initial Inspection for Cargo Configuration Airplanes (Aft of the Forward Entry Door)

(j) For Group 2 cargo airplanes identified in Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007: Perform a detailed inspection for cracking of the intercostal webs and attachment clips located aft of the forward entry door; and do all applicable corrective actions before further flight; in accordance with Part 4 of the Work Instructions of Boeing Special Attention Service Bulletin 737-53-1204, dated June 19, 2003; or Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007. After the effective date of this AD, only Revision 1 may be used.

Repeat Inspections

(k) Repeat the inspections required by paragraphs (h), (i), and (j) of this AD thereafter at intervals not to exceed 6,000 flight cycles after the previous inspection, or within 3,000 flight cycles after the effective date of this AD, whichever occurs later.

Exceptions

(l) Do the actions required by this AD by accomplishing all the applicable actions specified in the Accomplishment Instructions of the Boeing Special Attention Service Bulletin 737-53-1204, dated June 19, 2003; or Boeing Alert Service Bulletin 737-53A1204, Revision 1, dated March 26, 2007; (“the service bulletins”) except as provided by paragraphs (l)(1) and (l)(2) of this AD. After the effective date of this AD, only Revision 1 may be used

(1) Where the service bulletins specify to contact Boeing for repair instructions: Before further flight, repair using a method approved in accordance with the procedures specified in paragraph (m) of this AD.

(2) Where the service bulletins specify a compliance time relative to the date of a service bulletin, this AD requires compliance relative to the effective date of this AD. Where the service bulletins specify a compliance time relative to the date of the initial release of the service bulletin, this AD requires compliance relative to the effective date of AD 2005-20-03 (November 1, 2005).

Alternative Methods of Compliance (AMOCs)

(m)(1) The Manager, Seattle Aircraft Certification Office (ACO), FAA, ATTN: Howard Hall, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle ACO, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone]; has the authority to approve AMOCs for this AD, if requested using 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) 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) AMOCs approved previously in accordance with AD 2005-20-03 are approved as AMOCs for the corresponding provisions of this AD, provided the repetitive inspection intervals (if any) do not exceed 6,000 flight cycles.

(5) AMOCs approved previously in accordance with AD 2005-20-03 are not approved as AMOCs for the provisions of paragraph (j) or (k) of this AD.

Issued in Renton, Washington, on November 6, 2008.

Stephen P. Boyd,

Assistant Manager, Transport Airplane Directorate, Aircraft Certification Service.