2010-23841. Airworthiness Directives; The Boeing Company Model 737-300, -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 all Model 737-300, -400, and -500 series airplanes. The existing AD currently requires repetitive inspections for discrepancies of the fuse pins of the inboard and outboard midspar fittings of the nacelle strut, and corrective actions if necessary. This proposed AD would add replacing the midspar fuse pins with new, improved fuse pins, which would terminate the repetitive inspections. This proposed AD results from a report of corrosion damage of the chrome runout on the head side found on all four midspar fuse pins of the nacelle strut. Additionally, a large portion of the chrome plate was missing from the corroded area of the shank. We are proposing this AD to prevent damage of the fuse pins of the inboard and outboard midspar fittings of the nacelle strut, which could result in reduced structural integrity of the fuse pins, and consequent loss of the strut and separation of the engine from the airplane.

DATES:

We must receive comments on this proposed AD by November 8, 2010.

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 proposed AD, contact Boeing Commercial Airplanes, Attention: Data & Services Management, P.O. Box 3707, MC 2H-65, Seattle, Washington 98124-2207; telephone [phone], extension 1; fax [phone]; e-mail [e-mail]; Internet https://www.myboeingfleet.com. You may review copies of the referenced service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. For information on the availability of this material at the FAA, call 425-227-1221.

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:

Alan Pohl, 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-2010-0855; Directorate Identifier 2010-NM-066-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 29, 2008, we issued AD 2008-21-03, amendment 39-15687 (73 FR 59493, October 9, 2008), for all Model 737-300, -400, and -500 series airplanes. That AD requires repetitive inspections for discrepancies of the fuse pins of the inboard and outboard midspar fittings of the nacelle strut, and corrective actions if necessary. That AD resulted from a report of corrosion damage of the chrome runout on the head side found on all four midspar fuse pins of the nacelle strut. Additionally, a large portion of the chrome plate was missing from the corroded area of the shank. We issued that AD to detect and correct discrepancies of the fuse pins of the inboard and outboard midspar fittings of the nacelle strut, which could result in reduced structural integrity of the fuse pins, and consequent loss of the strut and separation of the engine from the airplane.

Actions Since Existing AD Was Issued

In the preamble to the NPRM of AD 2008-21-03, the FAA specified that the actions required by that AD were considered “interim action” and that the manufacturer was developing a modification to address the unsafe condition. The FAA indicated that it may consider further rulemaking action once the modification was developed, approved, and available. The manufacturer now has developed such a modification, and the FAA has determined that further rulemaking action is indeed necessary; this proposed AD follows from that determination.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 737-54A1044, Revision 2, dated January 20, 2010. The repetitive detailed inspections and corrective actions are similar to those described in Boeing Special Attention Service Bulletin 737-54-1044, dated December 10, 2007 (referenced in AD 2008-21-03 as the appropriate source of service information). Revision 2 of the service bulletin adds procedures for replacing the midspar fuse pins with new, improved fuse pins. Replacement with the new, improved fuse pin eliminates the need for repetitive detailed inspections.

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 2008-21-03 and would retain the requirements of the existing AD. This proposed AD would also require replacing the midspar fuse pins with new, improved fuse pins, which would terminate the requirement for repetitive detailed inspections.

Change to Existing AD

This proposed AD would retain all requirements of AD 2008-21-03. Since AD 2008-21-03 was issued, the AD format has been revised, and certain paragraphs have been rearranged. As a result, paragraph (f) of the existing AD has been re-identified as paragraph (g) in this NPRM.

Costs of Compliance

There are about 1,961 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	Parts	Cost per airplane	Number of U.S.- registered airplanes	Fleet cost
Repetitive detailed inspections (required by AD 2008-21-03)	4	$85	None	$340, per inspection cycle	616	$209,440, per inspection cycle.
Midspar fuse pin replacement (new proposed action)	1 per pin (up to 4 pins per airplane)	85	$843 per pin	Up to $3,712	616	Up to $2,286,592.

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 FAA amends § 39.13 by removing amendment 39-15687 (73 FR 59493, October 9, 2008) and adding the following new AD:

The Boeing Company: Docket No. FAA-2010-0855; Directorate Identifier 2010-NM-066-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by November 8, 2010.

Affected ADs

(b) This AD supersedes AD 2008-21-03, Amendment 39-15687.

Applicability

(c) This AD applies to all The Boeing Company Model 737-300, -400, and -500 series airplanes, certificated in any category.

Subject

(d) Air Transport Association (ATA) of America Code 54: Nacelles/Pylons.

Unsafe Condition

(e) This AD results from a report of corrosion damage of the chrome runout on the head side found on all four midspar fuse pins of the nacelle strut. Additionally, a large portion of the chrome plate was missing from the corroded area of the shank. The Federal Aviation Administration is issuing this AD to prevent damage of the fuse pins of the inboard and outboard midspar fittings of the nacelle strut, which could result in reduced structural integrity of the fuse pins, and consequent loss of the strut and separation of the engine from the airplane.

Compliance

(f) 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 Requirements of AD 2008-21-03

Repetitive Inspections/Corrective Actions, With Revised Service Information

(g) At the applicable time specified in paragraph 1.E., “Compliance” of Boeing Special Attention Service Bulletin 737-54-1044, dated December 10, 2007; except, where the service bulletin specifies a compliance time after the date on the service bulletin, this AD requires compliance within the specified compliance time after November 13, 2008 (the effective date of AD 2008-21-03): Do a detailed inspection for discrepancies of the fuse pins of the inboard and outboard midspar fittings of the nacelle strut by doing all the actions, including all applicable corrective actions, in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-54-1044, dated December 10, 2007; or Boeing Alert Service Bulletin 737-54A1044, Revision 2, dated January 20, 2010. Do all applicable corrective actions before further flight. Repeat the inspection at the time specified in paragraph 1.E. of Boeing Special Attention Service Bulletin 737-54-1044, dated December 10, 2007. Accomplishing the actions of paragraph (h) of this AD terminates the requirements of this paragraph.

New Requirements of This AD

Replacement

(h) Within 120 months after the effective date of this AD, replace all midspar fuse pins having part number (P/N) 311A1092-2 with a midspar fuse pin having P/N 311A1092-3, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-54A1044, Revision 2, dated January 20, 2010. Accomplishing the requirements of this paragraph terminates the requirements of paragraph (g) of this AD for that fuse pin.

Actions Accomplished According to Previous Revision of Service Information

(i) Actions done before the effective date of this AD in accordance with Boeing Special Attention Service Bulletin 737-54-1044, Revision 1, dated November 26, 2008, are acceptable for compliance with the corresponding requirements of this AD.

Alternative Methods of Compliance (AMOCs)

(j)(1) The Manager, Seattle Aircraft Certification Office (ACO), FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. Send information to ATTN: Alan Pohl, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone]. Information may be e-mailed to: [e-mail].

(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 principal maintenance inspector (PMI) or principal avionics inspector (PAI), as appropriate, or lacking a principal inspector, your local Flight Standards District Office. The AMOC approval letter must specifically reference this AD.

(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 the Boeing Commercial Airplanes Organization Designation Authorization (ODA) that 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 in accordance with the requirements of AD 2008-21-03 are acceptable for the corresponding requirements of this AD.

Issued in Renton, Washington, on September 15, 2010.

Robert D. Breneman,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.