[Federal Register Volume 61, Number 168 (Wednesday, August 28, 1996)]
[Proposed Rules]
[Pages 44230-44232]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-21877]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-NM-145-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100 and -200 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 737-100 and -
200 series airplanes. This proposal would require replacing the aileron 
(lateral) control transfer mechanism with a new modified mechanism, or 
reworking the existing mechanism. 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 unexpected, significant control wheel forces and reduced travel 
of a control wheel due to mechanical interference within the lateral 
control system transfer mechanism during a jam override condition.

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-145-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9 a.m. and 3 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-145-AD.'' The postcard will be date stamped and 
returned to the commenter.

[[Page 44231]]

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-145-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

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 mechanical 
interference can occur within the aileron control transfer mechanism on 
Model 737 series airplanes. The aileron control transfer mechanism 
(lateral control system transfer mechanism) enables lateral (roll) 
control of the airplane to be retained through either the captain's 
control wheel or the first officer's control wheel in the event that a 
malfunction restricts motion of the other control wheel or its cable 
system. When control motion is restricted, the captain's control wheel 
independently controls the aileron system; the first officer's control 
wheel independently controls the spoiler system. The aileron or spoiler 
system can be operated when sufficient force to overcome the resistance 
of a preloaded torsion spring in the aileron transfer mechanism is 
applied to the control wheel.
    If mechanical interference occurs within the lateral control system 
transfer mechanism and one of the control wheels jams, the travel of 
the operable (non-jammed) control wheel may be limited to 
100 degrees about the jam position, instead of the intended 
minimum available travel of 138 degrees. Additionally, the 
control wheel forces that are required to override a jam may be above 
normal. If the airplane is already banked or at a low altitude, or if 
the flightcrew does not respond rapidly enough to override the jam, 
such conditions, if not corrected, could result in an unexpected, 
significant control upset.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 27-1033, 
dated February 13, 1970, which describes procedures for either 
replacing the aileron (lateral) control transfer mechanism with a new 
modified mechanism (specified in the service bulletin as Procedure I), 
or reworking the existing mechanism (specified in the service bulletin 
as Procedure II). Accomplishment of the replacement or rework will 
enable the flightcrew to correct reduced travel of the control wheel or 
cable system due to a mechanical interference, and will allow increased 
travel of the operable control wheel in such cases.

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 either replacing the aileron control transfer 
system, transfer mechanism with a new modified mechanism, or reworking 
the existing mechanism. 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 
actions, 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 necessary parts. 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 236 Model 737-100 and -200 series airplanes 
of the affected design in the worldwide fleet. The FAA estimates that 
157 airplanes of U.S. registry would be affected by this proposed AD.
    For operators that elect to accomplish the proposed replacement, it 
would take approximately 20 work hours per airplane to accomplish it, 
at an average labor rate of $60 per work hour. Required parts would 
cost approximately $15,343 per airplane. Based on these figures, the 
cost impact of the proposed replacement on U.S. operators is estimated 
to be $16,543 per airplane.
    For operators that elect to accomplish the proposed rework by using 
new components, it would take approximately 40 work hours to accomplish 
it, at an average labor rate of $60 per work hour. Required parts would 
cost approximately $6,500. Based on these figures, the cost impact of 
the proposed rework (by using new components) on U.S. operators is 
estimated to be $8,900 per airplane.
    For operators that elect to accomplish the proposed rework by 
machine shop rework of the components, it would take approximately 70 
work hours to accomplish it, at an average labor rate of $60 per work 
hour. Required parts would cost approximately $1,450. Based on these 
figures, the cost impact of the proposed rework (by machine shop rework 
of the components) on U.S. operators is estimated to be $5,650 per 
airplane.
    The cost impact figures discussed above are 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)

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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-145-AD.

    Applicability: Model 737-100 and -200 series airplanes; as 
listed in Boeing Service Bulletin 27-1033, dated February 13, 1970; 
certificated 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 (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 an unexpected, significant control upset due to 
mechanical interference within the lateral control system transfer 
mechanism, which could result in reduced travel of a control wheel 
and above normal control wheel forces during a jam override, 
accomplish the following:
    (a) Within 18 months after the effective date of this AD: 
Accomplish the requirements of either paragraph (a)(1) or (a)(2) of 
this AD, in accordance with Boeing Service Bulletin 27-1033, dated 
February 13, 1970.
    (1) Replace the aileron control transfer mechanism, part number 
(P/N) 65-54200-4 or -5, with a new modified mechanism in accordance 
with Procedure I of the Accomplishment Instructions of the service 
bulletin. Or
    (2) Rework the existing aileron control transfer mechanism, P/N 
65-54200-4 or -5, in accordance with Procedure II of the 
Accomplishment Instructions of the service bulletin.
    (b) As of the effective date of this AD, no person shall install 
an aileron control transfer mechanism having P/N 65-54200-4 or -5 
unless it has been reworked in accordance with the requirements of 
paragraph (a)(2) of this AD.
    (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. 96-21877 Filed 8-23-96; 9:01 am]
BILLING CODE 4910-13-U