E7-17285. Airworthiness Directives; Boeing Model 737-600, -700, -700C, -800 and -900 Series Airplanes

AGENCY:

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

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 737-600, -700, -700C, -800 and -900 series airplanes. This proposed AD would require repetitive lubrication of the left and right main landing gear (MLG) forward trunnion pins. This proposed AD would also require an inspection for discrepancies of the transition radius of the MLG forward trunnion pins, and repair or replacement if necessary. This proposed AD would also require a one-time inspection for discrepancies of the lead-in chamfer and cross-bolt bore, and repair or replacement if necessary. Doing the applicable inspections and repairs/replacements, or overhauling the trunnion pins ends the repetitive lubrication requirements of this proposed AD. This proposed AD results from a report that the protective finishes on the forward trunnion pins for the left and right MLG might have been damaged during final assembly. We are proposing this AD to prevent cracking of the forward trunnion pin, which could result in fracture of the pin and consequent collapse of the MLG.

DATES:

We must receive comments on this proposed AD by October 15, 2007.

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: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.
• Fax: [phone].
• Hand Delivery: Room W12-140 on the ground floor of the West Building, 1200 New Jersey Avenue, SE., 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:

Nancy Marsh, 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 submit any relevant written data, views, or arguments regarding this proposed AD. Send your comments to an address listed in the ADDRESSES section. Include the docket number “FAA-2007-29087; Directorate Identifier 2007-NM-094-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 Operations office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Operations office (telephone [phone]) is located on the ground floor of the West Building at the 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 a report indicating that the protective finishes on the forward trunnion pins for the main landing gear (MLG) might have been damaged during final assembly of Boeing Model 737-600, -700, -700C, -800 and -900 series airplanes. The protective coating could be damaged at two locations because of the use of an unauthorized process, and damaged at one location because the pin was not handled correctly. Therefore, it is possible that these trunnion pins have been delivered to operators with compromised corrosion protection in these critical areas:

• The cross-bolt bore and outer diameter surface.
• The lead-in chamfer and outer diameter surface.
• The transition radius between the chrome-plated outer diameter and the spherical ball bearing surface.

Damage to the protective finish puts the base metal of the trunnion pin at risk from corrosion pitting. This condition, if not corrected, could lead to cracking of the forward trunnion pin, which could result in fracture of the pin and consequent collapse of the MLG.

Relevant Service Information

We have reviewed Boeing Service Bulletin 737-32-1376, Revision 1, dated March 19, 2007. The service bulletin describes procedures for repetitive lubrication of the MLG forward trunnion pins. The service bulletin states that accomplishing the inspections and applicable repairs/replacements described below, or overhauling the trunnion pins in accordance with Boeing 737 Component Maintenance Manual 57-15-01, eliminates the need for the repetitive lubrication.

The service bulletin also describes procedures for an inspection for discrepancies (corrosion, finish damage, surface deformation, or scratches) of the transition radius. If any discrepancy is found, the service bulletin specifies repairing or replacing the trunnion pin, as applicable, depending on the type of discrepancy found. The repair includes blending and restoring the protective finish. If the trunnion pin is not replaced, the service bulletin specifies an additional inspection for discrepancies of the lead-in chamfer and the cross-bolt bore. If any discrepancy is found, the service bulletin specifies repairing or replacing the trunnion pin, as applicable, depending on the type of discrepancy found.

Accomplishing the actions specified in the service information is intended to 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. 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 “Difference Between the Proposed AD and the Service Bulletin.”

Difference Between the Proposed AD and the Service Bulletin

Although Boeing Service Bulletin 737-32-1376, Revision 1, dated March 19, 2007, specifies to send inspection reports to the manufacturer, this proposed AD would not require that action.

Costs of Compliance

There are about 890 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. The average labor rate is $80 per work hour.

Estimated Costs

Action	Work hours	Parts	Cost per airplane	Number of U.S.-registered airplanes	Fleet cost
Repetitive lubrication	1	$0	$80, per lubrication cycle	300	$24,000, per lubrication cycle.
Inspections	4	0	320	300	$96,000.

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.

§ 39.13

[Amended]

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

Boeing: Docket No. FAA-2007-29087; Directorate Identifier 2007-NM-094-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by October 15, 2007.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 737-600, -700, -700C, -800 and -900 series airplanes, certificated in any category, as identified in Boeing Service Bulletin 737-32-1376, Revision 1, dated March 19, 2007.

Unsafe Condition

(d) This AD results from a report that the protective finishes on the forward trunnion pins for the left and right main landing gear (MLG) might have been damaged during final assembly. We are issuing this AD to prevent cracking of the forward trunnion pin, which could result in fracture of the pin and consequent 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.

Lubrication or Overhaul

(f) Within 30 days after the effective date of this AD: Lubricate the left and right MLG forward trunnion pins in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-32-1376, Revision 1, dated March 19, 2007. Repeat the lubrication at intervals not to exceed 30 days until all applicable requirements of paragraphs (g) and (h) of this AD have been accomplished. Overhauling the trunnion pin as given in the Accomplishment Instructions of Boeing Service Bulletin 737-32-1376, Revision 1, ends the repetitive lubrication requirements of this paragraph for that pin.

Inspection and Corrective Actions

(g) Within 60 months after the date of issuance of the original standard airworthiness certificate or date of issuance of the original standard export certificate of airworthiness, or within 6 months after the effective date of this AD, whichever occurs later: Do a detailed inspection for discrepancies (corrosion, finish damage, surface deformation, or scratches) of the transition radius of the left and right MLG trunnion pin; and if any discrepancy is found, repair or replace the trunnion pin before further flight. Do all actions in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-32-1376, Revision 1, dated March 19, 2007.

(h) For any airplane on which a trunnion pin is not replaced in accordance with paragraph (g) of this AD, within 96 months after the date of issuance of the original standard airworthiness certificate or date of issuance of the original standard export certificate of airworthiness, or within 12 months after the effective date of this AD, whichever occurs later: Do a detailed inspection for discrepancies of the lead-in chamfer and cross-bolt bore; and if any discrepancy is found, repair or replace the trunnion pin before further flight. Do all actions in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-32-1376, Revision 1, dated March 19, 2007.

No Report Required

(i) Although Boeing Service Bulletin 737-32-1376, Revision 1, dated March 19, 2007, specifies to send inspection reports to the manufacturer, this AD does not include that requirement.

Credit for Actions Done Using Previous Issue of Service Information

(j) Actions done before the effective date of this AD in accordance with Boeing Service Bulletin 737-32-1376, dated May 12, 2005, are acceptable for compliance with the corresponding actions of this AD.

Alternative Methods of Compliance (AMOCs)

(k)(1) The Manager, Seattle Aircraft Certification Office (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) 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.

Issued in Renton, Washington, on August 17, 2007.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.