[Federal Register Volume 59, Number 224 (Tuesday, November 22, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-28745]
[[Page Unknown]]
[Federal Register: November 22, 1994]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-NM-198-AD]
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 replacement
of the horizontal stabilizer trim electric actuator. This proposal is
prompted by reports of a binding condition in the clutch disk in the
horizontal stabilizer trim electric actuator. The actions specified by
the proposed AD are intended to prevent reduced controllability of the
airplane due to binding of a clutch disk in the horizontal stabilizer
trim electric actuator.
DATES: Comments must be received by January 19, 1995.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 94-NM-198-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: Kenneth W. Frey, Aerospace Engineer,
Systems and Equipment Branch, ANM-132S, FAA, Transport Airplane
Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue,
SW., Renton, Washington 98055-4056; telephone (206) 227-2673; 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 94-NM-198-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. 94-NM-198-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
Recently, the FAA has received reports from operators of Boeing
Model 737-300, -400, and -500 series airplanes that the stabilizer trim
wheel continued to turn after the switches for the stabilizer trim had
been operated and released. Investigation revealed that the clutch disk
in the horizontal stabilizer trim electric actuator may have caused the
clutch to bind intermittently.
Normally, when the switches for the stabilizer trim are operated,
the horizontal stabilizer trim electric actuator turns and engages
either the ``nose up'' or the ``nose down'' clutch, which causes the
stabilizer to move. When the switches for the stabilizer trim are
released, the clutch disengages, and the actuator continues to turn
until it stops (coasts) through deceleration. Under normal operating
conditions, the stabilizer movement stops immediately after the clutch
disengages.
However, a binding clutch may cause the stabilizer to continue to
move while the electric actuator coasts. The stabilizer may move in the
direction it was last commanded or it may reverse and move in the
opposite direction. The direction depends on which clutch disk is
binding. This condition, if not corrected, could result in reduced
controllability of the airplane.
The FAA has reviewed and approved Boeing Alert Service Bulletin
737-27A1191, Revision 1, dated November 3, 1994, which describes
procedures for replacement of horizontal stabilizer trim electric
actuators, having part number (P/N) 10-62033-3, with a different model
(P/N 10-62033-4) that eliminates the problems associated with binding
of the clutch disk.
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 replacement of the electric actuator of the
stabilizer trim with a different model. The actions would be required
to be accomplished in accordance with the alert service bulletin
described previously.
[Note: As a result of recent communications with the Air Transport
Association (ATA) of America, the FAA has learned that, in general,
some operators may misunderstand the legal effect of AD's on
airplanes that are identified in the applicability provision of the
AD, but that have been altered or repaired in the area addressed by
the AD. Under these circumstances, at least one operator appears to
have incorrectly assumed that its airplane was not subject to an AD.
On the contrary, all airplanes identified in the applicability
provision of an AD are legally subject to the AD. If an airplane has
been altered or repaired in the affected area in such a way as to
affect compliance with the AD, the owner or operator is required to
obtain FAA approval for an alternative method of compliance with the
AD, in accordance with the paragraph of each AD that provides for
such approvals. A note has been included in this notice to clarify
this requirement.]
There are approximately 1,448 Model 737-300, -400, and -500 series
airplanes of the affected design in the worldwide fleet. The FAA
estimates that 590 airplanes of U.S. registry would be affected by this
proposed AD, that it would take approximately 4 work hours per airplane
to accomplish the proposed actions, and that the average labor rate is
$60 per work hour. The cost of required parts would be approximately
$600 per airplane. Based on these figures, the total cost impact of the
proposed AD on U.S. operators is estimated to be $495,600, or $840 per
airplane.
The total 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.
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. App. 1354(a), 1421 and 1423; 49 U.S.C.
106(g); and 14 CFR 11.89.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
Boeing: Docket 94-NM-198-AD.
Applicability: Model 737-300, -400, and -500 series airplanes;
as listed in Boeing Alert Service Bulletin 737-27A1191, Revision 1,
dated November 3, 1994; 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 use the authority
provided in paragraph (c) to request approval from the FAA. This
approval may address either no action, if the current configuration
eliminates the unsafe condition; or different actions necessary to
address the unsafe condition described in this AD. Such a request
should include an assessment of the effect of the changed
configuration on the unsafe condition addressed by this AD. In no
case does the presence of any modification, alteration, or repair
remove any airplane from the applicability of this AD.
Compliance: Required as indicated, unless accomplished
previously.
To prevent reduced controllability of the airplane, accomplish
the following:
(a) Within 12 months after the effective date of this AD,
replace the horizontal stabilizer trim electric actuator having part
number 10-62033-3 with one that has been modified and re-identified
as P/N 10-62033-4, in accordance with Boeing Alert Service Bulletin
737-27A1191, Revision 1, dated November 3, 1994.
(b) As of the effective date of this AD, no person shall install
a horizontal stabilizer trim electric actuator having part number
10-62033-3 on any airplane.
(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
Secs. 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 November 16, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 94-28745 Filed 11-21-94; 8:45 am]
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