[Federal Register Volume 61, Number 193 (Thursday, October 3, 1996)]
[Proposed Rules]
[Pages 51624-51625]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-25307]
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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39
[Docket No. 96-NM-67-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 737-300, -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 737-300, -
400, and -500 series airplanes. This proposal would require replacing
certain aileron/rudder trim control modules with a new module that
contains an improved rudder trim switch to reduce internal friction.
This proposal is prompted by reports of sticking conditions in the
rudder trim switch. The actions specified by the proposed AD are
intended to prevent such sticking, which could result in uncommanded
movement of the rudder and consequent deviation of the airplane from
its set course.
DATES: Comments must be received by November 12, 1996.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 96-NM-67-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: Hania Younis, Aerospace Engineer,
Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft
Certification Office, 1601 Lind Avenue, SW., Renton, Washington;
telephone (206) 227-2764; 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-67-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-67-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
The FAA has received reports of sticking conditions in the rudder
trim switch on electric aileron/rudder trim control module P8-43 on
certain Model 737 series airplanes. One such report involved an
airplane that was climbing, under manual control, through an altitude
of 6,700 feet. The airplane began to yaw slightly to the left and the
flight crew felt some force on the rudder pedals; although the rudder
trim switch knob was centered, the rudder trim indicator showed that
the rudder was set at an angle of 16 degrees left of where it was
supposed to be.
If the trim switch sticks, it may be prevented from returning to
the center position. If this happens, the rudder trim actuator may
continue to move the rudder at a slow rate, up to the trim limit. This
rate of movement is very slow, however, at approximately 1/2 deg. per
second, which should provide ample time for the flight crew to detect
and correct the movement before it creates a situation of concern. In
most cases, these types of incidents can be stopped if the pilot merely
puts the switch into the center position
[[Page 51625]]
manually. In all incidents of this type, the rudder movement can by
stopped by use of the rudder pedals within the normal limits for yaw
control.
Sticking conditions in the rudder trim switch if not corrected,
however, could result in uncommanded movement of the rudder, and
consequent deviation of the airplane from its set course.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Alert Service Bulletin
737-27A1198, dated June 6, 1996, which describes procedures for
replacing aileron/rudder trim control module P8-43 with a new module
that contains an improved switch. This improved module minimizes
internal friction that has caused the sticking conditions.
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 replacing the aileron/rudder trim control
module P8-43 with a new improved module. The actions would be required
to be accomplished in accordance with the alert service bulletin
described previously.
Cost Impact
There are approximately 1,159 Boeing Model 737-300, -400, and -500
series airplanes of the affected design in the worldwide fleet. The FAA
estimates that 537 airplanes of U.S. registry would be affected by this
proposed AD. Replacement of the module would take approximately 3 work
hours per airplane to accomplish, at an average labor rate of $60 per
work hour. Required parts would cost approximately $1,063 per airplane.
Based on these figures, the cost impact of the proposed AD on U.S.
operators is estimated to be $667,491, or $1,243 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 96-NM-67-AD.
Applicability: Model 737-300, -400, and -500 series airplanes;
as listed in Boeing Alert Service Bulletin 737-27A1198, dated June
6, 1996; certified in any category.
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 (b) 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 sticking conditions in the rudder trim switch, which
could result in uncommanded movement of the rudder and consequent
deviation of the airplane from its set course, accomplish the
following:
(a) Within 2 years after the effective date of this AD, replace
the aileron/rudder trim control module P8-43 having part number (P/
N) 69-73703-5 or 69-73703-6 with a new aileron/rudder trim control
module having P/N 69-73703-8, in accordance with Boeing Alert
Service Bulletin 737-27A1198, dated June 6, 1996.
(b) 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.
(c) 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 September 26, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 96-25307 Filed 10-2-96; 8:45 am]
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