04-3493. Airworthiness Directives; Boeing Model 737-200C Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Boeing Model 737-200C series airplanes. This proposal would require repetitive inspections of the Station 348.2 frame to detect cracking under the stop fittings and intercostal flanges at Stringers 14L, 15L, and 16L; and corrective action if necessary. This action is necessary to prevent rapid decompression of the airplane, and possible separation of the forward entry door from the airplane. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by April 5, 2004.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2003-NM-208-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays. Comments may be submitted via fax to [phone]. Comments may also be sent via the Internet using the following address: [e-mail]. Comments sent via fax or the Internet must contain “Docket No. 2003-NM-208-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 or 2000 or ASCII text.

The service information referenced in the proposed rule may be obtained from Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Howard Hall, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the proposed rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this action may be changed in light of the comments received.

Submit comments using the following format:

• Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
• For each issue, state what specific change to the proposed AD is being requested.
• Include justification (e.g., reasons or data) for each request.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2003-NM-208-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2003-NM-208-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received a report of cracks in the Station 348.2 frame on a Boeing Model 737-200C series airplane. The Station 348.2 frame is located immediately aft of the forward entry door cutout. The cracks were located under the door stop fittings at Stringers 15L and 16L. Undetected fatigue cracks in the frame could propagate due to normal cyclic cabin pressure loading. If these fatigue cracks continue to propagate, the stop fittings can become ineffective. This condition, if not corrected, could result in a rapid decompression of the airplane, and possible separation of the forward entry door from the airplane.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin 737-53A1240, dated April 10, 2003, which describes procedures for performing repetitive detailed and eddy current inspections of the Station 348.2 frame for cracks under the stop fittings and intercostal flanges at Stringers 14L, 15L, and 16L. (Stringer 14L is similar to Stringers 15L and 16L.) The inspection procedures at these locations consist of: A detailed inspection of the entire area; an eddy current inspection of the forward surface of the Station 348.2 frame inner chord over a 4.0-inch length centered on the removed stop fittings at Stringers 15L and 16L; an eddy current rotary probe inspection of the frame at the fastener holes for the removed stop fittings at Stringers 14L, 15L, and 16L; an eddy current inspection of the intercostal forward flanges common to the aft side of the Station 348.2 frame at Stringers 14L, 15L, and 16L; and an eddy current inspection of the intercostal aft flange common to the forward side of the Station 360 frame at Stringer 15L. The alert service bulletin also specifies contacting Boeing for repair instructions if cracks are found.

Explanation of Requirements of Proposed Rule

Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would require accomplishment of the actions specified in the alert service bulletin described previously, except as discussed below.

Differences Between Proposed Rule and Alert Service Bulletin

Although the alert service bulletin specifies that operators may contact the manufacturer for disposition of certain cracking conditions, this proposed AD would require operators to repair those conditions per a method approved by the FAA, or per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings.

Cost Impact

There are approximately 78 airplanes of the affected design in the worldwide fleet. The FAA estimates that 15 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 18 work hours per airplane to accomplish the proposed inspections, and that the average labor rate is $65 per work hour. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $17,550, or $1,170 per airplane, per inspection cycle.

The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this proposed AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions.

Regulatory Impact

The regulations proposed herein 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. Therefore, it is determined that this proposal would not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that this 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) if promulgated, 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. A copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend part 39 of the Federal Aviation Regulations (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. Section 39.13 is amended by adding the following new airworthiness directive:

Boeing: Docket 2003-NM-208-AD.

Applicability: All Model 737-200C series airplanes; certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent rapid decompression of the airplane, and possible separation of the forward entry door from the airplane, accomplish the following:

Initial and Repetitive Inspections

(a) Except as provided by paragraph (b) of this AD: Prior to the accumulation 46,000 total flight cycles, or within 2,250 flight cycles after the effective date of this AD, whichever occurs later, do detailed and eddy current inspections of the Station 348.2 frame for cracking under the stop fittings and intercostal flanges at Stringers 14L, 15L, and 16L by accomplishing paragraphs 3.A. and 3.B.1. through 3.B.7. of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1240, dated April 10, 2003. Do the actions per the service bulletin. Any applicable repair must be accomplished prior to further flight. Repeat the inspections thereafter at intervals not to exceed 4,500 flight cycles.

Note 1:

For the purposes of this AD, a detailed inspection is defined as: “An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.”

Corrective Action

(b) If any crack is found during any inspection required by this AD, and the bulletin specifies to contact Boeing for appropriate action: Before further flight, repair per a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved, the approval must specifically reference this AD.

Alternative Methods of Compliance

(c) In accordance with 14 CFR 39.19, the Manager, Seattle ACO, FAA, is authorized to approve alternative methods of compliance (AMOCs) for this AD.

Issued in Renton, Washington, on February 9, 2004.

Ali Bahrami,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.