[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
