AD 2001-14-06

Effective August 16, 2001.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of August 16, 2001.

The service information referenced in this AD may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Stephen Oshiro, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2793; fax (425) 227-1181.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to all Boeing Model 737-300, -400, and -500 series airplanes was published in the Federal Register on August 28, 2000 (65 FR 52049). That action proposed to require repetitive inspections of certain connectors located in the main wheel wells to detect discrepancies; and corrective action, if necessary.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

One commenter states that it has done the initial inspection specified in the proposed rule, and is in agreement with the recommendation for continued repetitive inspections.

Two commenters note that there are two typographical errors in Boeing Service Letter 737-SL-24-138, dated May 24, 1999; which is specified in the proposed rule as the service information necessary to do the inspections and corrective action. The first error is on page 3 of the service letter. Action #4 identifies “connector D51641;” the correct number for the connector is D5164J. The FAA agrees that the identification of connector D51641 is in error and has revised paragraph (a) of the final rule to identify each affected connector. This action will eliminate any confusion as to which connectors require inspection, and will minimize the possibility of operators performing the inspections on the wrong connector.

The second error is in the “References,” section on page 1 of the service letter and identifies “Dt-54446, Standard Wiring Practice Manual, Subject 20-60-08;” the correct reference is D6-54446. The FAA agrees that this is an incorrect reference and has advised the manufacturer accordingly. As this change is minor and not part of any procedures specified for doing the actions in the final rule, no change to the final rule is necessary in this regard.

Two commenters request an extension of the compliance time for the inspections specified in paragraph (a) of the proposed rule.

One commenter asks that the compliance time for the initial inspection be extended from 12 months after the effective date of the AD, to the later of 12 months or 3,000 flight cycles after the effective date of the AD. The commenter also asks that the repetitive inspections be accomplished at the later of 18 months or 4,500 flight hours, instead of at intervals of 18 months. The commenter states that this extension is requested so it can do the inspections at a ‘C’-check. The commenter adds that this would provide the opportunity for operators to accomplish the work at a scheduled maintenance visit, instead of scheduling special visits.

The FAA does not concur to extend the compliance time for doing the initial inspection to the later of 12 months or 3,000 flight cycles. Such an extension may allow airplanes with low utilization rates to go without being inspected for several years. The present condition of the electrical connectors on each airplane is unknown, and contaminated electrical connectors are subject to corrosion regardless of whether or not the airplane is accumulating flight cycles. After doing the initial inspection, and, if necessary, correcting any discrepancies, the electrical connectors will be in a known condition for safe operation of the airplane. In this case, we concur that the repetitive inspection interval can be extended somewhat, but the interval of 4,500 flight hours will not provide an adequate level of safety for airplanes with low utilization rates, as stated above.

Another commenter asks that the compliance time for the repetitive inspections be extended from 12 months to 24 months. The commenter states that this would allow it to accomplish the required actions during regularly scheduled maintenance intervals.

We concur with the commenter and have extended the 18-month repetitive inspection interval specified in paragraph (a) of this final rule to 24 months.

One commenter asks that optional terminating action be included for the repetitive inspections specified in paragraph (a) of the proposed rule. The commenter suggests two possible terminating actions, as follows:

• Inspect the connectors in accordance with the service letter and replace the spare pins and filler plugs with pins that have spare wires installed. (This action would provide the same level of sealing capability as the existing wires terminated within the connector.) Or

• Replace the existing connectors with new connectors having no spare pin positions. (This action would completely remove any potential of contaminants entering through a spare pin location.)

The FAA does not concur. Missing filler rods or spare contacts could not be verified in two of the three incidents that were reported to us. As a result, we have not been able to determine the path of the contamination that entered the connectors. It is possible that contaminants could enter the connectors despite the presence of filler rods and contacts with wires. Without verification of the cause of the path of contamination, repetitive inspections are required to ensure that electrical arcing and uncommanded closure of the engine fuel shut-off valves do not occur. Termination of the repetitive inspections will necessitate design changes that will decrease the effects of connector contamination. Should the manufacturer develop such design changes, we may consider additional rulemaking in the future. No change to the final rule is necessary in this regard.

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

There are approximately 1,974 Model 737 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 755 airplanes of U.S. registry will be affected by this AD, that it will take approximately 1 work hour per airplane to accomplish the required inspection, and that the average labor rate is $60 per work hour. The cost of required parts will be negligible. Based on these figures, the cost impact of the inspection required by this AD on U.S. operators is estimated to be $45,300, or $60 per airplane, per inspection cycle.

The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this 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.

The regulations adopted herein will 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 final rule does not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that this action (1) is not a “significant regulatory action” under Executive Order 12866; (2) is not a “significant rule” under 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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption ADDRESSES.

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

1. The authority citation for part 39 continues to read as follows: