Airworthiness directives: Boeing,

[Federal Register: March 5, 1999 (Volume 64, Number 43)]

[Proposed Rules]

[Page 10578-10579]

From the Federal Register Online via GPO Access [wais.access.gpo.gov]

[DOCID:fr05mr99-15]

Proposed Rules Federal Register

This section of the FEDERAL REGISTER contains notices to the public of the proposed issuance of rules and regulations. The purpose of these notices is to give interested persons an opportunity to participate in the rule making prior to the adoption of the final rules.

[[Page 10578]]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-353-AD]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 737-100, -200, -300, -400, and -500 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 737-100, - 200, -300, -400, and -500 series airplanes. This proposal would require modification of certain filter module assemblies of the generator control units (GCU). This proposal is prompted by reports of smoke and occassional fire in the flight compartment as a direct result of a GCU failure. The actions specified by the proposed AD are intended to prevent failure of the filter module assemblies of the GCU's due to overcurrent conditions, which could result in an increased risk of smoke, and/or fire in the flight compartment.

DATES: Comments must be received by April 19, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 98-NM-353-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal holidays.

The service information referenced in the proposed rule may be obtained from Boeing Commercial Airplane Group, P.O. 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: Forrest Keller, Senior Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2790; fax (425) 227-1181.

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 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 filedin 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-353-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-353-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

Over the past several years, the FAA has received numerous reports of smoke and occasional fire in the flight compartment of certain Boeing Model 737 series airplanes. Many of these incidents are attributed to an overcurrent condition in the generator control units (GCU), during in-flight operation of the airplane, which resulted from transformer and/or diode failure in the GCU's power supply and exiter field power supply circuits. Failure of these components causes a localized overheat condition in a GCU. Such overcurrent and overheat conditions, if not detected and corrected could result in an increased risk of smoke and/or fire in the flight compartment.

Related Rulemaking

On March 10, 1989, the FAA issued AD 89-07-13, amendment 39-6165 (54 FR 11366, April 28, 1989), applicable to all Boeing Model 737 series airplanes, that requires replacement or modification of certain GCU filter modules. However, this proposed AD would not affect the requirements of that AD.

Explanation of Relevant Service Information

The FAA has reviewed and approved Sundstrand Corporation Service Bulletin SB92-101, Revision 1, dated December 10, 1996, which describes procedures for modification of the filter module assemblies of the GCU's. The modification involves installation of a terminal board with additional fuses and a protection cap. This modification will allow certain fuses to open when an overcurrent condition occurs. 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 require accomplishment of the actions specified in the service bulletin described previously, except as discussed below.

Differences Between Proposed Rule and Service Bulletin

Operators should note that, although the service bulletin specifies modification of the GCU's as interim action, pending determination of the

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root cause of a GCU failure. The FAA has determined that, for this proposed AD, the modification adequately addresses the identified unsafe condition. Therefore, this proposal is not considered to be interim action.

Cost Impact

There are approximately 2,675 airplanes of the affected design in the worldwide fleet. The FAA estimates that 1,091 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 3 work hours per airplane to accomplish the proposed modification, at an average labor rate of $60 per work hour. Required parts would cost approximately $450 per airplane. Based on these figures, the cost impact of the modification proposed by this AD on U.S. operators is estimated to be $687,330, or $630 per airplane.

The cost impact figure discussed above is 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 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 adding the following new airworthiness directive:

   Boeing: Docket 98-NM-353-AD.

   Applicability: Model 737-100, -200, -300, -400, and -500 series airplanes equipped with generator control units (GCU) having part numbers as listed in Sundstrand Corporation Service Bulletin SB92- 101, Revision 1, dated December 10, 1996; 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 (c) 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 prevent failure of the filter module assemblies of the generator control units (GCU) due to overcurrent conditions, which could result in an increased risk of smoke, and/or fire in the flight compartment, accomplish the following:

   (a) Within 2 years after the effective date of this AD, modify the filter module assemblies of the GCU's identified in Sundstrand Corporation Service Bulletin SB92-101, Revision 1, in accordance with paragraph 2.A or 2.B of the Accomplishment Instructions of the service bulletin, as applicable.

   (b) Within 2 years after the effective date of this AD, no person shall install on any airplane a GCU type AVZ122 having part number (P/N) 948F458-1 (Boeing P/N 10-61224-11), and type AVZ22C/D having P/N 915F212-4/-5 (Boeing P/N 10-61224-3), unless modified in accordance with this AD.

   (c) 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.

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

   (d) 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 February 26, 1999. Darrell M. Pederson, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

   [FR Doc. 99-5431Filed3-4-99; 8:45 am]

   BILLING CODE 4910-13-P