Airworthiness Directives; Boeing Model 727-100 and -200; 737-100, -200, -200C, -300, -400 and -500; and 747 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 727-100 and −200; 737-100, −200, −200C, −300, −400 and −500; and 747 series airplanes. This proposal would require, among other things, preparation of the electrical bonding faying surfaces on the forward and aft surfaces of the rear spars of the fuel tanks of the left and right wings, a one-time measurement of the electrical bonding resistances, and follow-on actions. This action is necessary to ensure adequate electrical bonding between the penetration fittings of the hydraulic heat exchanger and the rear spars of the fuel tanks. Inadequate electrical bonding, in the event of a lightning strike, could cause electrical arcing and ignition of fuel vapor in the wing fuel tank, which could result in a fuel tank explosion. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by September 4, 2003.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2001-NM-297-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays. Comments may be submitted via fax to (425) 227-1232. Comments may also be sent via the Internet using the following address: 9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must contain “Docket No. 2001-NM-297-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 for Windows or ASCII text.

The service information referenced in the proposed rule may be obtained from Boeing Commercial Airplane Group, PO Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Sulmo Mariano, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6501; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the proposed rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this action may be changed in light of the comments received. Submit comments using the following format:

• Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
• For each issue, state what specific change to the proposed AD is being requested.
• Include justification (e.g., reasons or data) for each request.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2001-NM-297-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2001-NM-297-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received data from the manufacturer indicating that, during an electrical bonding and grounding test of wing fuel tank penetrations on certain Boeing Model 747 series airplanes, it was found that the penetration fittings of the hydraulic heat exchanger were not electrically bonded to the rear spars. Inadequate electrical bonding, in the event of a lightning strike, could cause electrical arcing and ignition of fuel vapor in the wing fuel tank, which could result in a fuel tank explosion.

The electrical bonding condition of the penetration fittings of the hydraulic heat exchanger on certain Model 727 and 737 series airplanes may be the same as those on the affected Model 747 series airplanes. Therefore, these models may be subject to this same unsafe condition.

Explanation of Relevant Service Information

The FAA has reviewed and approved the following Boeing alert service bulletins:

These service bulletins describe procedures for preparation of the electrical bonding faying surfaces on the forward and aft surfaces of the rear spars of the fuel tanks of the left and right wings, a one-time measurement of the electrical bonding resistances between the penetration fittings of the hydraulic heat exchanger and the surfaces of the rear spars and between the heat exchanger tube and the lower wing stringer surfaces, and follow-on actions. The procedures to follow before preparation of the faying surfaces include depressurizing the hydraulic systems, draining the fuel from the fuel tanks of the left and right wings, disconnecting the inlet and outlet tubes of the heat exchangers, and removing the heat exchangers. The preparation of the faying surfaces is done by sanding the surface areas down to bare metal and applying alodine protective coating on the surfaces and re-installing the heat exchangers. The follow-on actions involve applying fillet sealant and protective finishes around the penetration fittings, servicing and pressurizing the hydraulic systems and examining for signs of hydraulic fluid leakage, and servicing the fuel tank and examining for signs of fuel leakage. Accomplishment of the actions specified in the service bulletins is intended to adequately address the identified unsafe condition.

The service bulletins reference Boeing 727, 737, and 747 Airplane Maintenance Manuals, Standard Wiring Practices Manuals, and Standard Overhaul Practices Manuals for the leak check and repair instructions if any discrepancy is found.

Explanation of Requirements of Proposed Rule

Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would require accomplishment of the actions specified in the service bulletins described previously, except as discussed below.

Difference Between the Service Bulletins and This Proposed AD

Although the service bulletins recommend accomplishing the specified actions at the earliest opportunity when manpower, materials, and facilities are available, we have determined that such an imprecise compliance time would not address the identified unsafe condition in a timely manner. In developing an appropriate compliance time for this AD, we considered not only the manufacturer's recommendation, but the degree of urgency associated with addressing the subject unsafe condition, the average utilization of the affected fleet, and the time necessary to perform the required actions (between 44 and 68 work hours). In light of all of these factors, we find a 5-year compliance time for completing the required actions to be warranted, in that it represents an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety.

Cost Impact

There are approximately 5,085 airplanes of the affected design in the worldwide fleet. We estimate that 2,251 airplanes of U.S. registry would be affected by this proposed AD. The following table shows the estimated cost impact to do the proposed actions for airplanes affected by this proposed AD. The average labor rate is $60 per work hour. The estimated maximum total cost for all airplanes affected by this proposed AD is $6,302,640.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this proposed 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 planning time, or time necessitated by other administrative actions.

Regulatory Impact

The regulations proposed herein 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. Therefore, it is determined that this proposal would not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that 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) if promulgated, 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 copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend part 39 of the Federal Aviation Regulations (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.