[Federal Register Volume 61, Number 168 (Wednesday, August 28, 1996)]
[Proposed Rules]
[Pages 44237-44239]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-21880]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-148-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-300 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 737-300 
series airplanes. This proposal would require an inspection to detect 
fatigue cracking, base trim, and upper flange over-trim of the pulley 
brackets of the aileron control cables. It also would require, if 
necessary, replacement of the pulley brackets with new pulley brackets, 
and replacement of the two button-head rivets with flush-head rivets. 
This proposal is prompted by a review of the design of the flight 
control systems on Model 737 series airplanes. The actions specified by 
the proposed AD are intended to prevent fatigue cracking or fracturing 
of the pulley brackets, which could result in slack in the cables and 
consequent reduced ability of the flightcrew to control the aileron.

DATES: Comments must be received by October 24, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 96-NM-148-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: Don Kurle, Senior Engineer, Systems 
and Equipment Branch, ANM-130S, FAA, Transport Airplane Directorate, 
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (206) 227-2798; fax (206) 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 96-NM-148-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-103, Attention: Rules 
Docket No. 96-NM-148-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

[[Page 44238]]

Discussion

    In October 1994, the FAA organized a team to conduct a Critical 
Design Review (CDR) of the flight control systems installed on Boeing 
Model 737 series airplanes in an effort to confirm the continued 
operational safety of these airplanes. The formation of the CDR team 
was prompted by questions that arose following an accident involving a 
Model 737-200 series airplane that occurred near Colorado Springs, 
Colorado, and one involving a Model 737-300 series airplane that 
occurred near Pittsburgh, Pennsylvania. The CDR team's analysis of the 
flight control systems was performed independent of the investigations 
of these accidents, which are conducted by the National Transportation 
Safety Board (NTSB). The cause of the accidents has not yet been 
determined.
    The CDR team was composed of representatives from the FAA, the 
NTSB, other U.S. government organizations, and foreign airworthiness 
authorities. The team reviewed the service history and the design of 
the flight control systems of Model 737 series airplanes. The team 
completed its review in May 1995. The recommendations of the team 
include various changes to the design of the flight control systems of 
these airplanes, as well as correction of certain design deficiencies. 
This proposed AD is one of nine rulemaking actions being issued by the 
FAA to address the recommendations of the CDR team.

Report Received by FAA

    The FAA has received a report indicating that some pulley brackets 
of the aileron control cables were trimmed to clear adjacent structure 
when the brackets were installed on the airplane during manufacture. In 
this case, the fatigue life of the pulley brackets can be compromised 
and the pulley brackets could crack or fracture. Fatigue cracking or 
fracturing of the pulley brackets, if not detected and corrected in a 
timely manner, could result in slack in the cables and consequent 
reduced ability of the flightcrew to control the aileron.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 737-27-
1154, dated August 25, 1988, which describes procedures for a visual 
inspection to detect fatigue cracking, base trim, and upper flange 
over-trim of the pulley brackets of the aileron control cables. It also 
describes procedures for replacing the pulley brackets with new pulley 
brackets, and replacing the two button-head rivets with flush-head 
rivets, if necessary. Installation of flush-head rivets will prevent 
interference between the pulley brackets and the adjacent structure.

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 a visual inspection to detect fatigue 
cracking, base trim, and upper flange over-trim of the pulley brackets 
of the aileron control cables. It also would require, if necessary, 
replacement of the pulley brackets with new pulley brackets, and 
replacement of the two button-head rivets with flush-head rivets. The 
actions would be required to be accomplished in accordance with the 
service bulletin described previously.

Explanation of Proposed Compliance Time

    In developing an appropriate compliance time for the proposed 
inspection, the FAA's intent is that it be performed during a regularly 
scheduled maintenance visit for the majority of the affected fleet, 
when the airplanes would be located at a base where special equipment 
and trained personnel would be readily available, if necessary. In 
addition, the FAA considered the availability of replacement pulley 
brackets and rivets that may be needed if fatigue cracking, base trim, 
or upper flange over-trim is detected. The FAA finds that 18 months 
corresponds closely to the interval representative of most of the 
affected operators' normal maintenance schedules. The FAA considers 
that this interval will provide an acceptable level of safety.

Cost Impact

    There are approximately 262 Model 737-300 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 169 
airplanes of U.S. registry would be affected by this proposed AD, that 
it would take approximately 1 work hour per airplane to accomplish the 
proposed inspection, and that the average labor rate is $60 per work 
hour. Based on these figures, the cost impact of the proposed AD on 
U.S. operators is estimated to be $10,140, or $60 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.
    Should an operator be required to accomplish the necessary 
replacement of pulley brackets and rivets, it would take approximately 
15 work hours per airplane to accomplish those actions, at an average 
labor rate of $60 per work hour. Required parts would cost 
approximately $713 per airplane. Based on these figures, the cost 
impact of any necessary replacement action is estimated to be $1,613 
per airplane.

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 96-NM-148-AD.

    Applicability: Model 737-300 series airplanes; as listed in 
Boeing Service Bulletin 737-27-1154, dated August 25, 1988; 
certificated in any category.


[[Page 44239]]


    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
otherwise 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 fatigue cracking or fracturing of the pulley 
brackets, which could result in slack in the cables and consequent 
reduced ability of the flightcrew to control the aileron, accomplish 
the following:
    (a) Within 18 months after the effective date of this AD: 
Perform a visual inspection to detect fatigue cracking, base trim, 
or upper flange over-trim of the pulley brackets, part number (P/N) 
65C25555-3, 65C25555-501, or 69-73479-1, of the aileron control 
cables, in accordance with Boeing Service Bulletin 737-27-1154, 
dated August 25, 1988.
    (b) If any cracking or over-trim of the pulley brackets is 
detected: Prior to further flight, replace the pulley brackets with 
new pulley brackets; and replace the two existing button-head rivets 
with flush-head rivets; in accordance with Boeing Service Bulletin 
737-27-1154, dated August 25, 1988.
    (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 August 21, 1996.
Ronald T. Wojnar,


Manager, Transport Airplane Directorate, Aircraft Certification 
Service.

[FR Doc. 96-21880 Filed 8-23-96; 9:01 am]
BILLING CODE 4910-13-U