E8-25048. Airworthiness Directives; Boeing Model 737-100, -200, -200C, -300, -400, and -500 Series Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

We propose to adopt a new airworthiness directive (AD) for certain Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. For certain airplanes, this proposed AD would require deactivation or modification of the wiring to the outboard landing lights, until the wire bundles and electrical connectors have been replaced. For all airplanes, this proposed AD would also require an inspection for any broken, damaged, or missing fairleads, grommets, and wires in the four electrical junction boxes of the main wheel well, and corrective actions if necessary. For certain airplanes, this proposed AD would also require replacement of certain wire bundles for the landing lights and fuel shutoff valves, and related investigative, other specified, and corrective actions if necessary. For certain airplanes, this proposed AD would also require replacement of certain electrical connectors and backshell clamps. This proposed AD results from reports of uncommanded engine shutdowns and burned and damaged wire bundles associated with the outboard landing lights and engine fuel shutoff valves. This proposed AD also results from reports of damaged and missing grommets and broken and damaged fairleads in the electrical junction boxes of the main wheel well. We are proposing this AD to prevent a hot short between the outboard landing light and fuel shutoff valve circuits, which could result in an uncommanded engine shutdown. We are also proposing this AD to prevent corrosion of the electrical connectors of the wing rear spars, which could result in short circuits and consequent incorrect functioning of airplane systems needed for safe flight and landing.

DATES:

We must receive comments on this proposed AD by December 8, 2008.

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:

Stephen Oshiro, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, 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-2008-1116; Directorate Identifier 2007-NM-231-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

We have received reports of uncommanded engine shutdowns and burned and damaged wire bundles where the wire bundle exits the main wheel well in the area of the wing rear spar on Boeing Model 737-300, -400, and -500 series airplanes. Investigation revealed that the uncommanded engine shutdowns were caused by uncommanded closure of the engine fuel shutoff valves, which resulted from short circuits between the 115 volt alternating current (VAC) circuits of the outboard landing lights and the 28 volt direct current (VDC) circuits of the engine fuel shutoff valves. This short circuit causes the valve to move towards the closed position. Failure of the valve occurs shortly after reaching the closed position due to exposure of the 28-VDC valve to 115-VAC power from the outboard landing light circuit. The loss of ability to reopen the valve prevents restarting the engine due to the unavailability of fuel. Uncommanded closure of the fuel shutoff valve due to a hot short between the outboard landing light and the fuel shutoff valve circuits, if not corrected, could result in an uncommanded engine shutdown.

Subsequently, Boeing published Boeing Service Bulletin 737-28-1241, dated April 7, 2006, to provide instructions for replacing certain wire bundles with new, re-designed wire bundles to prevent short circuits between the outboard landing light and engine fuel shutoff valve circuits. After issuing that service bulletin, Boeing discovered that some of the replacement wire bundles were inadvertently assembled and delivered with electrical connectors and backshells having a cadmium-plated finish instead of an anodized aluminum finish. The electrical connectors and backshells are located on the rear spar of the left and right wings. The cadmium-plated connectors and backshells corrode quickly when exposed to potassium-based de-icing fluids. This corrosion leads to moisture ingress into the electrical connectors and subsequent corrosion of the electrical contacts within the electrical connectors. This condition, if not corrected, could result in short circuits and consequent incorrect functioning of airplane systems needed for safe flight and landing.

We have also received reports of damaged and missing grommets and broken and damaged fairleads in the electrical junction boxes of the main wheel well on Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. Although there is no evidence that these wiring discrepancies have contributed to uncommanded engine shutdowns, the wiring in this area includes the wire bundles for the engine fuel shutoff valves, as well as wiring for other systems needed for continued safe flight and landing of the airplane.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 737-33A1140, dated May 22, 2006, for Model 737-300, -400, and -500 series airplanes. The service bulletin specifies accomplishing the actions in either Part 1 or Part 2 of the Accomplishment Instructions. Part 1 describes procedures for deactivating the outboard landing lights. The deactivation includes installing collars and “do not close” tags on the circuit breakers for the outboard landing lights, and capping and stowing the wires from the circuit breakers. Part 2 describes procedures for modifying the wiring to the outboard landing lights. The modification includes capping and stowing the existing wires to the outboard landing lights, and routing new wires to the outboard landing lights.

We have also reviewed Boeing Service Bulletin 737-28-1241, Revision 1, dated August 31, 2007, for Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. Part 1 of the Accomplishment Instructions of the service bulletin applies to certain Model 737-300, -400, and -500 series airplanes. Part 1 describes procedures for replacing certain wire bundles for the landing lights and fuel shutoff valves with new, re-designed wire bundles, and doing related investigative, other specified, and corrective actions if necessary. The related investigative actions include (1) doing a detailed inspection for any broken, damaged, or missing grommet where the wire bundles go from the wheel well to the wing and (2) doing a detailed inspection for any broken, damaged, or missing fairleads, any damaged or missing grommets, and any chafed or damaged wires or wire bundles in the electrical junction boxes of the main wheel well. The other specified actions include (1) removing any additional outboard landing light wires from the wire bundles installed in accordance with Boeing Alert Service Bulletin 737-33A1140 and (2) terminating the outboard landing lights at the circuit breakers, as necessary. The corrective actions include (1) replacing any broken, damaged, or missing fairlead with a new fairlead, (2) replacing any damaged or missing grommet with a new grommet, and (3) repairing or replacing any chafed or damaged wires and wire bundles with new wires and wire bundles.

Part 2 of the Accomplishment Instructions of Boeing Service Bulletin 737-28-1241 describes procedures for doing a detailed inspection for any broken, damaged, or missing fairleads, any damaged or missing grommets, and any chafed or damaged wires or wire bundles in the four electrical junction boxes of the main wheel well, and doing the corrective actions as necessary.

Part 3 of the Accomplishment Instructions of Boeing Service Bulletin 737-28-1241 applies to certain Model 737-300, -400, and -500 series airplanes on which the wire bundle replacement was done in accordance with the original issue of the service bulletin, dated April 7, 2006. Part 3 describes procedures for replacing certain electrical connectors and backshell clamps with new, improved electrical connectors and backshell clamps.

Accomplishing the applicable actions specified in Boeing Service Bulletin 737-28-1241 would end the need for accomplishing the deactivation or modification specified in Boeing Alert Service Bulletin 737-33A1140.

Boeing Alert Service Bulletin 737-33A1140 and Boeing Service Bulletin 737-28-1241 specify prior or concurrent accomplishment of Boeing Special Attention Service Bulletin 737-28-1196, dated December 5, 2002; Revision 1, dated March 13, 2003; Revision 2, dated August 21, 2003; or Revision 3, dated April 1, 2004. Boeing Special Attention Service Bulletin 737-28-1196 describes procedures for changing the wire connections for the engine fuel shutoff valves and the outboard landing lights.

FAA's Determination and Requirements of This Proposed AD

We are proposing this AD because we evaluated all relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the(se) same type design(s). This proposed AD would require the following actions:

• For Model 737-300, -400, and -500 series airplanes, deactivation or modification of the wiring to the outboard landing lights, until the wire bundles and electrical connectors have been replaced.
• For all airplanes, a detailed inspection for any broken, damaged, or missing fairleads, any damaged or missing grommets, and any chafed or damaged wires or wire bundles in the four electrical junction boxes of the main wheel well, and corrective actions if necessary.
• For certain airplanes, replacement of certain wire bundles for the landing lights and fuel shutoff valves with new, re-designed wire bundles, and related investigative, other specified, and corrective actions if necessary.
• For certain airplanes, replacement of certain electrical connectors and backshell clamps with new, improved electrical connectors and backshell clamps.

Difference Between the Proposed AD and Service Bulletins

Although Boeing Service Bulletin 737-28-1241 and Boeing Alert Service Bulletin 737-33A1140 specify prior or concurrent accomplishment of Boeing Special Attention Service Bulletin 737-28-1196, this proposed AD would not require that action. The accomplishment of Boeing Special Attention Service Bulletin 737-28-1196 is already required by AD 2005-10-11, amendment 39-14088 (70 FR 28419, May 18, 2005).

Costs of Compliance

We estimate that the actions specified in Boeing Alert Service Bulletin 737-33A1140 would affect about 511 Model 737-300, -400, and -500 series airplanes of U.S. registry. Operators may accomplish either the deactivation or modification.

We estimate that the deactivation would take about 1 work-hour per product to comply with this proposed AD. The average labor rate is $80 per work-hour. Based on these figures, we estimate the cost of the deactivation to the U.S. operators to be $40,880, or $80 per product.

We estimate that the modification would take about 31 work-hours per product to comply with this proposed AD. The average labor rate is $80 per work-hour. Required parts for the modification would cost about $573 per product. Based on these figures, we estimate the cost of modification to the U.S. operators to be $1,560,083, or $3,053 per product.

We estimate that the actions specified in Boeing Alert Service Bulletin 737-28-1241 would affect up to 891 Model 737-100, -200, -200C, -300, -400, and -500 series airplanes of U.S. registry. The following table provides the estimated costs, at an average labor rate of $80 per work-hour, for U.S. operators to comply with the actions specified in that service bulletin.

Estimated Costs

Action	Work hours	Parts	Cost per airplane	Number of U.S.-registered airplanes	Fleet cost
Part 1—Replacement of wire bundles	Up to 91	Up to $18,439	$25,719	511	$13,142,409
Part 2—Inspection of junction boxes	1	0	80	891	71,280
Part 3—Replacement of electrical connectors	2	298	458	400	183,200

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 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 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. 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.

You can find our regulatory evaluation and the estimated costs of compliance in the AD Docket.

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 adding the following new AD:

Boeing: Docket No. FAA-2008-1116; Directorate Identifier 2007-NM-231-AD.

Comments Due Date

(a) We must receive comments by December 8, 2008.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes, certificated in any category; as identified in Boeing Service Bulletin 737-28-1241, Revision 1, dated August 31, 2007.

Unsafe Condition

(d) This AD results from reports of uncommanded engine shutdowns and burned and damaged wire bundles associated with the outboard landing lights and engine fuel shutoff valves. This AD also results from reports of damaged and missing grommets and broken and damaged fairleads in the electrical junction boxes of the main wheel well. We are issuing this AD to prevent a hot short between the outboard landing light and fuel shutoff valve circuits, which could result in an uncommanded engine shutdown. We are also issuing this AD to prevent corrosion of the electrical connectors of the wing rear spars, which could result in short circuits and consequent incorrect functioning of airplane systems needed for safe flight and landing.

Compliance

(e) Comply with this AD within the compliance times specified, unless already done.

Deactivation or Modification of the Outboard Landing Lights

(f) For Model 737-300, -400, and -500 series airplanes identified in Boeing Alert Service Bulletin 737-33A1140, dated May 22, 2006 (“the alert service bulletin”): Within 180 days after the effective date of this AD, accomplish the actions specified in either paragraph (f)(1) or (f)(2) of this AD. Accomplishing the applicable actions required by paragraph (g) of this AD terminates the requirements of this paragraph.

(1) Deactivate the outboard landing lights, by accomplishing all of the actions specified in Part 1 of the Accomplishment Instructions of the alert service bulletin.

Note 1:

The Master Minimum Equipment List (MMEL) prohibits dispatching an airplane for night operations with deactivated outboard landing lights in the event that either of the inboard landing lights fail. Operators should note that, if the outboard landing lights are deactivated in accordance with Part 1 of the service bulletin, there is no MMEL relief allowing for this configuration for night operations should any inboard landing light fail.

(2) Modify the wiring to the outboard landing lights, by accomplishing all of the actions specified in Part 2 of the Accomplishment Instructions of the alert service bulletin.

Inspection and Replacements

(g) For all airplanes: Within 60 months after the effective date of this AD, do the applicable actions specified in paragraphs (g)(1), (g)(2), and (g)(3) of this AD, by accomplishing all of the applicable actions specified in the Accomplishment Instructions of Boeing Service Bulletin 737-28-1241, Revision 1, dated August 31, 2007. For Model 737-300, -400, and -500 series airplanes identified in Boeing Alert Service Bulletin 737-33A1140, dated May 22, 2006, accomplishing the applicable actions required by this paragraph terminates the requirements of paragraph (f) of this AD.

(1) Replace the wire bundles for the landing lights and fuel shutoff valves with new, re-designed wire bundles, and do the related investigative, other specified, and corrective actions, as applicable. The related investigative, other specified, and corrective actions must be done before further flight after the replacement.

(2) Do a detailed inspection for any broken, damaged, or missing fairleads, any damaged or missing grommets, and any chafed or damaged wires or wire bundles in the four electrical junction boxes of the main wheel well, and do the applicable corrective actions. The corrective actions must be done before further flight after the inspection.

(3) Replace the electrical connectors and backshell clamps with new, improved electrical connectors and backshell clamps, as applicable.

Credit for Actions Done According to Previous Issue of Service Bulletin

(h) For airplanes identified as Groups 1 and 2 in Boeing Service Bulletin 737-28-1241, Revision 1, dated August 31, 2007: Actions done before the effective date of this AD in accordance with Boeing Service Bulletin 737-28-1241, dated April 7, 2006, are acceptable for compliance with the requirements of paragraph (g) of this AD.

(i) For all airplanes: Actions done before the effective date of this AD in accordance with Part 2 of the Accomplishment Instructions of Boeing Service Bulletin 737-28-1241, dated April 7, 2006, are acceptable for compliance with the requirements of paragraph (g)(2) of this AD.

Alternative Methods of Compliance (AMOCs)

(j)(1) The Manager, Seattle Aircraft Certification Office (ACO), FAA, ATTN: Stephen Oshiro, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, 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.

Issued in Renton, Washington, on October 10, 2008.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.