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

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 notice may be changed in light of the comments received. 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 notice must submit a self-addressed, stamped postcard on which the following statement is made: ``Comments to Docket Number 98-NM-318-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. 98-NM-318-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On September 23, 1998, the FAA issued AD 98-19-09, amendment 39- 10751 (63 FR 52152, September 30, 1998), applicable to all Boeing Model 737-100, -200, -300, -400, and -500 series airplanes, to require removal of the fuel boost pump wiring in the conduits of the wing and center fuel tanks; an inspection to detect damage of the wiring, and corrective action, if necessary; and eventual installation of Teflon sleeving over the electrical cable. The actions of that AD were required for airplanes that had accumulated 20,000 or more total flight hours. That AD was prompted by reports of severe wear of the fuel boost pump wiring due to chafing between the wiring and the surrounding conduit inside the fuel tank; pin-hole-sized holes in the conduit that appear to be the result of arc-through of the conduit; and exposure of the main tank boost pump wire conductor inside a conduit and signs of arcing to the wall of the conduit. The requirements of that AD are intended to detect and correct chafing and electrical arcing between the fuel boost pump wiring and the surrounding conduit, which, if not corrected, could result in arc-through of the conduit, and consequent fire or explosion of the fuel tank.

Actions Since Issuance of Previous Rule

In the preamble to AD 98-19-09, the FAA indicated it was considering further rulemaking action to require inspection of Model 737 series airplanes that have accumulated less than 20,000 total flight hours. The FAA now has determined that further rulemaking action is indeed necessary, and this proposed AD follows from that determination. The FAA has determined that it is necessary to expand the inspection requirement to ensure that excessive wire chafing does not occur on those airplanes. The FAA has examined wire bundles that were removed and inspected for chafing in accordance with telegraphic AD's T98-10-51 (issued on May 7, 1998) and T98-11-51 (issued on May 10, 1998) and AD 98-11-52 (63 FR 34271, June 24, 1998). Based on the findings, the FAA tabulated levels of wire chafing as a function of airplane flight hours. Based on the tabulated data, the FAA has determined that it is necessary to define long-term repetitive inspection intervals to address the identified unsafe condition for the entire fleet of 737-100 through - 500 series airplanes. In consideration of these data and the additional layer of Teflon sleeving installed for further protection of the wire bundles, the FAA proposes a repetitive inspection interval of 30,000 flight hours. In light of the new proposed repetitive inspections, the installation of Teflon sleeving required by AD 98-19-09, which terminates the requirements of that AD, would not terminate the requirements of this proposed AD.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Service Bulletin 737- 28A1120, Revision 2, dated November 26, 1998. The procedures described in Revision 2 of this service bulletin are essentially identical to those described in Boeing Alert Service Bulletin 737-28A1120, Revision 1, dated May 28, 1998 (which was referenced as an appropriate source of service information in AD 98-19-09). Revision 2 removes certain airplanes from the effectivity listing and specifies different parts to be provided in the parts kit by the manufacturer. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition.

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 supersede AD 98-19-09 to continue to require removal of the fuel boost pump wiring in the conduits of the wing and center fuel tanks; an inspection to detect damage of the wiring, and corrective action, if necessary; and eventual installation of Teflon sleeving over the electrical cable. This action would additionally require that the inspection be conducted at repetitive intervals and that the inspection be accomplished on airplanes that have accumulated less than 20,000 total flight hours. The actions would be required to be accomplished in accordance with the service bulletin described previously, except as discussed below. The proposed AD also would require that operators report results of the initial inspection to the FAA.

Difference Between the Proposed AD and the Service Bulletin

Operators should note that, while Boeing Service Bulletin 737- 28A1120, Revision 2, limits its effectivity to airplanes having line numbers 1 through 3072 inclusive, this proposed AD would be applicable to all Model 737-100 through -500 series airplanes.

Cost Impact

There are approximately 2,866 airplanes of the affected design in the worldwide fleet. The FAA estimates that 1,131 airplanes of U.S. registry would be affected by this proposed AD. The inspection that is currently required by AD 98-19-09, and retained in this AD, takes approximately 30 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. This new AD action would require repetitive performance of that inspection. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $2,035,800, or $1,800 per airplane, per inspection cycle. The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the current or proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted.

Regulatory Impact

The regulations proposed herein would not have substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this proposal would not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. 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.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by removing amendment 39-10751 (63 FR 52152, September 30, 1998), and by adding a new airworthiness directive (AD), to read as follows: Boeing: Docket 98-NM-318-AD. Supersedes AD 98-19-09, Amendment 39- 10751.

Applicability: All Model 737-100, -200, -300, -400, and -500 series airplanes; certificated in any category.

Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (n)(1) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously. To detect and correct chafing and prevent electrical arcing between the fuel boost pump wiring and the surrounding conduit, which could result in arc-through of the conduit, and consequent fire or explosion of the fuel tank, accomplish the following:

Inspections Required by AD 98-11-52

(a) For all airplanes that have accumulated 50,000 or more total flight hours as of June 29, 1998 (the effective date of AD 98-11-52, amendment 39-10611): Prior to further flight, remove the fuel boost pump wiring from the in-tank conduit for the aft boost pumps in main tanks numbers 1 and 2, and perform a detailed visual inspection to detect damage of the wiring, in accordance with the procedures specified in Boeing Alert Service Bulletin 737-28A1120, dated April 24, 1998, as revised by Notices of Status Change NSC 01, dated May 7, 1998, NSC 02, dated May 8, 1998, and NSC 03, dated May 9, 1998; Boeing Alert Service Bulletin 737-28A1120, Revision 1, dated May 28, 1998; or Boeing Service Bulletin 737-28A1120, Revision 2, dated November 26, 1998. (b) For all airplanes that have accumulated less than 50,000 total flight hours as of receipt of telegraphic AD T98-11-51: Prior to the accumulation of 40,000 total flight hours, or within 14 days after June 29, 1998, whichever occurs later, remove the fuel boost pump wiring from the in-tank conduit for the aft boost pumps in main tanks numbers 1 and 2, and perform a detailed visual inspection to detect damage of the wiring, in accordance with the procedures specified in Boeing Alert Service Bulletin 737-28A1120, dated April 24, 1998, as revised by Notices of Status Change NSC 01, dated May 7, 1998, NSC 02, dated May 8, 1998, and NSC 03, dated May 9, 1998; Revision 1, dated May 28, 1998; or Revision 2, dated November 26, 1998. (c) For all airplanes: Remove the fuel boost pump wiring from the in-tank conduit for the center tank left and right boost pumps, and perform a detailed visual inspection to detect damage of the wiring, in accordance with the procedures specified in Boeing Alert Service Bulletin 737-28A1120, dated April 24, 1998, as revised by Notices of Status Change NSC 01, dated May 7, 1998, NSC 02, dated May 8, 1998, and NSC 03, dated May 9, 1998; Revision 1, dated May 28, 1998; or Revision 2, dated November 26, 1998. Accomplish the inspection at the earliest of the times specified in paragraphs (c)(1), (c)(2), and (c)(3). (1) For Model 737-300, -400, and -500 series airplanes: Inspect prior to the accumulation of 40,000 total flight hours, or within 14 days after June 29, 1998, whichever occurs later. (2) For Model 737-100 and -200 series airplanes: Inspect prior to the accumulation of 40,000 total flight hours, or within 10 days after June 29, 1998, whichever occurs later. (3) For all airplanes: Inspect prior to the accumulation of 50,000 total flight hours, or within 5 days after June 29, 1998, whichever occurs later. (d) For all airplanes: Prior to the accumulation of 30,000 total flight hours or within 45 days after June 29, 1998, whichever occurs later, remove the fuel boost pump wiring from the in-tank conduit for the aft boost pumps in main tanks numbers 1 and 2, and the center tank left and right boost pumps, and perform a detailed visual inspection to detect damage of the wiring, in accordance with the procedures specified in Boeing Alert Service Bulletin 737- 28A1120, dated April 24, 1998, as revised by Notices of Status Change NSC 01, dated May 7, 1998, NSC 02, dated May 8, 1998, and NSC 03, dated May 9, 1998; Revision 1, dated May 28, 1998; or Revision 2, dated November 26, 1998.

Inspection Required by AD 98-19-09

(e) For airplanes that have accumulated 20,000 or more total flight hours and less than 30,000 total flight hours as of October 15, 1998 (the effective date of AD 98-19-09, amendment 39-10751): Within 60 days after October 15, 1998, remove the fuel boost pump wiring from the in-tank conduit for the aft boost pumps in main tanks numbers 1 and 2, and the center tank left and right boost pumps, and perform a detailed visual inspection to detect damage of the wiring; in accordance with the procedures specified in Boeing Alert Service Bulletin 737-28A1120, dated April 24, 1998, as revised by Notices of Status Change NSC 01, dated May 7, 1998, NSC 02, dated May 8, 1998, and NSC 03, dated May 9, 1998; Revision 1, dated May 28, 1998; or Revision 2, dated November 26, 1998.

New Inspection Requirements

(f) For airplanes that have accumulated less than 20,000 total flight hours as of October

15, 1998: Remove the fuel boost pump wiring from the in-tank conduit for the aft boost pumps in main tanks numbers 1 and 2, and the center tank left and right boost pumps, and perform a detailed visual inspection to detect damage of the wiring; at the earlier of the times specified in paragraphs (f)(1) and (f)(2) of this AD; in accordance with the procedures specified in Boeing Alert Service Bulletin 737-28A1120, dated April 24, 1998, as revised by Notices of Status Change NSC 01, dated May 7, 1998, NSC 02, dated May 8, 1998, and NSC 03, dated May 9, 1998; Boeing Alert Service Bulletin 737- 28A1120, Revision 1, dated May 28, 1998; or Boeing Service Bulletin 737-28A1120, Revision 2, dated November 26, 1998. (1) Prior to the accumulation of 20,000 total flight hours, or within 60 days after the effective date of this AD, whichever occurs later. (2) Within 24 months after the effective date of this AD. (g) For all airplanes: Repeat the inspection required by paragraph (d), (e), or (f) of this AD, as applicable, at intervals not to exceed 30,000 flight hours after initial accomplishment of the applicable inspection.

Corrective Actions

(h) If red, yellow, blue, or green wire insulation cannot be seen through the outer jacket of the electrical cable during any inspection required by this AD: Prior to further flight, accomplish paragraph (h)(1), (h)(2), or (h)(3) of this AD in accordance with procedures specified in Boeing Alert Service Bulletin 737-28A1120, dated April 24, 1998, as revised by Notices of Status Change NSC 01, dated May 7, 1998, NSC 02, dated May 8, 1998, and NSC 03, dated May 9, 1998; Revision 1, dated May 28, 1998; or Revision 2, dated November 26, 1998. (1) Install Teflon sleeving over the electrical cable, and reinstall the cable. Or (2) Reinstall the electrical cable without Teflon sleeving over the cable. Within 500 flight hours after accomplishment of the reinstallation, repeat the inspection described in paragraph (d), (e), or (f) of this AD, as applicable, and install Teflon sleeving over the cable. Or (3) Replace the electrical cable with new cable without Teflon sleeving. Within 18 months or 6,000 flight hours, whichever occurs first, repeat the inspection specified in paragraph (d), (e), or (f) of this AD, as applicable, and install Teflon sleeving over the cable. (i) If red, yellow, blue, or green wire insulation can be seen through the outer jacket of the electrical cable during any inspection required by this AD, but no evidence of electrical arcing is found: Prior to further flight, accomplish either paragraph (i)(1) or (i)(2) of this AD in accordance with the procedures specified in Boeing Alert Service Bulletin 737-28A1120, dated April 24, 1998, as revised by Notices of Status Change NSC 01, dated May 7, 1998, NSC 02, dated May 8, 1998, and NSC 03, dated May 9, 1998; Boeing Alert Service Bulletin 737-28A1120, Revision 1, dated May 28, 1998; or Boeing Service Bulletin 737-28A1120, Revision 2, dated November 26, 1998. (1) Replace the damaged electrical cable with a new cable, install Teflon sleeving over the cable, and reinstall the cable. Or (2) Replace the electrical cable with a new cable without Teflon sleeving. Within 18 months or 6,000 flight hours, whichever occurs first, repeat the inspection described in paragraph (d), (e), or (f) of this AD, as applicable, and install Teflon sleeving over the cable. (j) If any evidence of electrical arcing but no evidence of fuel leakage is found on the removed electrical cable during any inspection required by this AD: Prior to further flight, accomplish paragraphs (j)(1) and (j)(2) of this AD in accordance with the procedures specified in Boeing Alert Service Bulletin 737-28A1120, dated April 24, 1998, as revised by Notices of Status Change NSC 01, dated May 7, 1998, NSC 02, dated May 8, 1998, and NSC 03, dated May 9, 1998; Boeing Alert Service Bulletin 737-28A1120, Revision 1, dated May 28, 1998; or Boeing Service Bulletin 737-28A1120, Revision 2, dated November 26, 1998. (1) Verify the integrity of the conduit in accordance with the instructions contained in NSC 03, Revision 1, or Revision 2 of the alert service bulletin. And (2) Accomplish either paragraph (j)(2)(i) or (j)(2)(ii) of this AD in accordance with the alert service bulletin. (i) Replace the damaged electrical cable with a new cable, install Teflon sleeving over the cable, and reinstall the cable. Or (ii) Replace the electrical cable with a new cable without Teflon sleeving. Within 18 months or 6,000 flight hours, whichever occurs first, repeat the inspection described in paragraph (d), (e), or (f) of this AD, as applicable, and install Teflon sleeving over the cable. (k) If any evidence of fuel is found on the removed electrical cable during any inspection required by this AD: Prior to further flight, accomplish paragraphs (k)(1) and (k)(2) of this AD in accordance with the procedures specified in Boeing Alert Service Bulletin 737-28A1120, dated April 24, 1998, as revised by Notices of Status Change NSC 01, dated May 7, 1998, NSC 02, dated May 8, 1998, and NSC 03, dated May 9, 1998; Boeing Alert Service Bulletin 737- 28A1120, Revision 1, dated May 28, 1998; or Boeing Service Bulletin 737-28A1120, Revision 2, dated November 26, 1998. (1) Replace the conduit section where electrical arcing was found. And (2) Accomplish either paragraph (k)(2)(i) or (k)(2)(ii) of this AD. (i) Replace the damaged electrical cable with a new cable, install Teflon sleeving over the cable, and reinstall the cable. Or (ii) Replace the electrical cable with a new cable without Teflon sleeving. Within 18 months or 6,000 flight hours, whichever occurs first, repeat the inspection described in paragraph (d), (e), or (f) of this AD, as applicable, and install Teflon sleeving over the cable. (l) For Groups 1 and 2 airplanes, as identified in Boeing Alert Service Bulletin 737-28A1120, dated April 24, 1998: Concurrent with the first accomplishment of corrective action in accordance with paragraph (h), (i), (j), or (k) of this AD, as applicable, replace the case ground wire with a new wire in accordance with Boeing Alert Service Bulletin 737-28A1120, dated April 24, 1998, as revised by Notices of Status Change NSC 01, dated May 7, 1998, NSC 02, dated May 8, 1998, and NSC 03, dated May 9, 1998; Boeing Alert Service Bulletin 737-28A1120, Revision 1, dated May 28, 1998; or Boeing Service Bulletin 737-28A1120, Revision 2, dated November 26, 1998. (m) If any damage specified in paragraph (h), (i), or (j) of this AD is found during the initial inspection required by paragraph (a), (b), (c), (d), (e), or (f) of this AD, as applicable: Within 10 days after accomplishing that initial inspection, accomplish paragraphs (m)(1) and (m)(2) of this AD. Information collection requirements contained in this regulation have been approved by the Office of Management and Budget (OMB) under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and have been assigned OMB Control Number 2120-0056. (1) Submit any damaged electrical cables and conduits to Boeing, in accordance with Boeing Alert Service Bulletin 737-28A1120, dated April 24, 1998, as revised by Notices of Status Change NSC 01, dated May 7, 1998, NSC 02, dated May 8, 1998, and NSC 03, dated May 9, 1998; Boeing Alert Service Bulletin 737-28A1120, Revision 1, dated May 28, 1998; or Boeing Service Bulletin 737-28A1120, Revision 2, dated November 26, 1998. Include the serial number of the airplane, the number of total flight hours and flight cycles accumulated on the airplane, and the location of the electrical cable on the airplane. (2) For airplanes that are inspected after June 29, 1998, submit the serial number of the airplane, the number of total flight hours and flight cycles accumulated on the airplane, and the location of the electrical cable on the airplane to the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; fax (425) 227-1181. (n)(1) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO. (n)(2) Alternative methods of compliance, approved previously in accordance with AD 98-11-52 and AD 98-19-09, are approved as alternative methods of compliance with this AD.

Note 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

(o) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

Issued in Renton, Washington, on December 31, 1998. Darrell M. Pederson, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 99-482 Filed 1-8-99; 8:45 am] BILLING CODE 4910-13-U