04-18744. Airworthiness Directives; Boeing Model 737-100, -200, -200C, and -300 Series Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 737-100, -200, -200C, and -300 series airplanes. This proposed AD would require repetitive detailed inspections to detect discrepancies of the retaining pin lugs on the support fitting of the main landing gear (MLG) beam, and rework of the support fitting, or replacement of the fitting if necessary. This proposed AD is prompted by reports of discrepancies of the lugs. We are proposing this AD to prevent separation of the support beam of the MLG from the rear spar, which could cause cracking of the MLG support fitting and a consequent leak in the wing fuel tank or collapse of the MLG.

DATES:

We must receive comments on this proposed AD by October 1, 2004.

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.
• By fax: [phone].
• 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.

You can get the service information identified in this proposed AD from Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207.

You may examine the contents of this AD docket on the Internet at http://dms.dot.gov,, or at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street, SW., Room PL-401, on the plaza level of the Nassif Building, Washington, DC.

FOR FURTHER INFORMATION CONTACT:

Technical Information: Robert C. Hardwick, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

Plain Language Information: Marcia Walters, [e-mail].

SUPPLEMENTARY INFORMATION:

Docket Management System (DMS)

The FAA has implemented new procedures for maintaining AD dockets electronically. As of May 17, 2004, new AD actions are posted on DMS and assigned a docket number. We track each action and assign a corresponding directorate identifier. The DMS AD docket number is in the form “Docket No. FAA-2004-99999.” The Transport Airplane Directorate identifier is in the form “Directorate Identifier 2004-NM-999-AD.” Each DMS AD docket also lists the directorate identifier (“Old Docket Number”) as a cross-reference for searching purposes.

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 under ADDRESSES. Include “Docket No. FAA-2004-18877; Directorate Identifier 2002-NM-340-AD” in the subject line 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 submitted 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 website, 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 can 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.

We are reviewing the writing style we currently use in regulatory documents. We are interested in your comments on whether the style of this document is clear, and your suggestions to improve the clarity of our communications that affect you. You can get more information about plain language at http://www.faa.gov/​language and http://www.plainlanguage.gov.

Examining the Docket

You can examine the AD docket 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 [phone]) is 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 DMS receives them.

Discussion

We have received a report indicating that broken or cracked retaining pin lugs have occurred on the support fitting of the main landing gear (MLG) beam, on certain Boeing Model 737-100 and -200 series airplanes. There was also a report of an elongated bolt hole in the lug. There were no reports of the fuse pin migrating out of the fitting. Cracked lugs can result from excessive clamp-up of the lugs, excessive grease pressure during routine lubrication of the fuse pin, migration of the fuse pin, or a combination of those factors. Fracture of the lugs, if not corrected, could result in the loss of the retaining pin and migration of the fuse pin, and consequent leak in the wing fuel tank or collapse of the MLG.

Relevant Service Information

We have reviewed Boeing Special Attention Service Bulletin 737-57-1267, dated August 8, 2002. The service bulletin describes procedures for repetitive detailed inspections of the retaining pin lugs on the support fitting of the MLG beam for discrepancies, and rework of the support fitting if necessary. The rework includes performing a penetrant inspection of the fitting, and cutting off the support beam fitting lugs and installing a new fitting that replaces the removed lugs. Reworking the fitting would eliminate the need for the repetitive inspections.

Boeing has also issued Service Bulletin 737-57-1216, Revision 2, dated May 6, 1999, which, among other things, describes procedures for replacing the support fitting of the MLG beam with a new fitting. For certain airplanes, the service bulletin describes procedures for installing a special bushing to prevent damage to the retainer bolt under certain circumstances. Replacing the support fitting would eliminate the need for the repetitive inspections.

We have determined that accomplishment of the actions specified in the service bulletins will 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. Therefore, we are proposing this AD, which would require repetitive detailed inspections to detect discrepancies of the retaining pin lugs on the support fitting of the MLG beam, and rework of the support fitting, or replacement of the fitting if necessary. The proposed AD would require you to use the service information described previously to perform these actions, except as discussed under “Differences Between the Proposed AD and the Service Bulletin.”

Differences Between the Proposed AD and the Service Bulletin

Boeing Service Bulletin 737-57-1216, Revision 2, specifies that you may contact the manufacturer for instructions on how to repair certain conditions, but this proposed AD would require you to repair those conditions in one of the following ways:

• Using a method that we approve; or
• Using data that meet the type certification basis of the airplane, and that have been approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings.

Costs of Compliance

This proposed AD would affect about 1,670 airplanes worldwide and 668 airplanes of U.S. registry. The proposed actions would take about 2 work hours 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 $86,840, or $130 per airplane.

The rework, if accomplished, would take approximately 24 work hours per airplane to accomplish at an average labor rate of $65 per work hour. Required parts would cost approximately $1,006 per airplane. Based on these figures, the cost impact of the rework provided by this AD is estimated to be $2,566 per airplane.

The replacement of the support fitting of the MLG beam, if accomplished, would take approximately 128 work hours per airplane to accomplish at an average labor rate of $65 per work hour. Required parts would cost approximately between $4,540 and $5,271 per airplane. Based on these figures, the cost impact of the replacement provided by this AD is estimated to be between $12,860 and $13,591 per airplane.

The replacement of the support fitting and installation of a special bushing of the MLG beam (for Group 9 and Group 10 airplanes), if accomplished, would take approximately 144 work hours per airplane to accomplish at an average labor rate of $65 per work hour. Required parts would cost approximately $5,081 per airplane. Based on these figures, the cost impact of this action is estimated to be $14,441 per airplane.

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. 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.

§ 39.13

[Amended]

2. The FAA amends § 39.13 by adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2004-18877; Directorate Identifier 2002-NM-340-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this AD action by October 1, 2004.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 737-100, -200, -200C, and -300 series airplanes, certificated in any category; line numbers 1 through 1670 inclusive.

Unsafe Condition

(d) This AD was prompted by reports of discrepancies of the lugs on the support fitting of the main landing gear (MLG) beam. We are issuing this AD to prevent separation of the support beam of the MLG from the rear spar, which could cause cracking of the MLG support fitting and a consequent leak in the wing fuel tank or collapse of the MLG.

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

(f) Prior to the accumulation of 15,000 total flight cycles, or within 3,000 flight cycles after the effective date of this AD, whichever occurs later: Perform a detailed inspection to detect cracking of the retaining pin lugs of the support fitting of the MLG beam, or elongation of a bolt hole in a lug, per the Accomplishment Instructions, Part I: Inspection, of Boeing Special Attention Service Bulletin 737-57-1267, dated August 8, 2002. If no cracked lug or elongated bolt hole is found, repeat the inspection at intervals not to exceed 12,000 flight cycles, until the actions specified in paragraph (h) of this AD are accomplished.

Note 1:

For the purposes of this AD, a detailed inspection is “an intensive examination of a specific item, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at an intensity deemed appropriate. Inspection aids such as mirrors magnifying lenses, etc. may be necessary. Surface cleaning and elaborate procedures may be required.”

Corrective Action

(g) If any cracked lug or elongated bolt hole is found during any inspection required by paragraph (f) of this AD, before further flight, do paragraph (g)(1) or (g)(2) of this AD.

(1) Rework the fitting per the Accomplishment Instructions, Part II: Rework, of Boeing Special Attention Service Bulletin 737-57-1267, dated August 8, 2002.

(2) Replace the fitting per the Accomplishment Instructions, Part III—Fitting Replacement, of Boeing Service Bulletin 737-57-1216, Revision 2, dated May 6, 1999.

Optional Terminating Action

(h) Reworking or replacing the fitting per paragraph (g)(1) or (g)(2) of this AD constitutes terminating action for the inspections required by paragraph (f) of this AD.

Repair

(i) If any cracking 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 (DER) 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.

Parts Installation

(j) As of the effective date of this AD: With the exception of a new lug, all lugs must be inspected or reworked, as applicable, in accordance with this AD before being installed on any airplane.

Alternative Methods of Compliance (AMOCs)

(k)(1) The Manager, Seattle 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) An AMOC that provides an acceptable level of safety may be used for any repair required by this AD, if it is approved by a Boeing Company DER who has been authorized by the Manager, Seattle ACO, to make such findings.

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

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.