[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)
[[Page 44232]]
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
