[Federal Register Volume 64, Number 43 (Friday, March 5, 1999)]
[Proposed Rules]
[Pages 10578-10579]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-5431]


 ========================================================================
 Proposed Rules
                                                 Federal Register
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 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.
 
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 

  Federal Register / Vol. 64, No. 43 / Friday, March 5, 1999 / Proposed 
Rules  

[[Page 10578]]


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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).

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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 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-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

[[Page 10579]]

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. 99-5431 Filed 3-4-99; 8:45 am]
BILLING CODE 4910-13-P