[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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