[Federal Register Volume 61, Number 168 (Wednesday, August 28, 1996)]
[Proposed Rules]
[Pages 44241-44242]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-21882]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-150-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100, -200, -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 all Boeing Model 737-100, -200, -
300, -400, and -500 series airplanes. This proposal would require an 
inspection of the aileron/elevator power control units (PCU's) and the 
rudder PCU to determine if reworked PCU manifold cylinder bores 
containing chrome plating are installed, and replacement of the 
cylinder bores with bores that have been reworked using the oversize 
method or the steel sleeve method, if necessary. 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 a reduced rate of movement of the elevator, 
aileron, or rudder due to contamination of hydraulic fluid from chrome 
plating chips; such reduced rate of movement, if not corrected, could 
result in reduced controllability of the airplane.

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-150-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: Don Kurle, Senior Engineer, Systems 
and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification 
Office, 1601 Lind Avenue, SW., Renton, Washington; 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-150-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-150-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.

Reports Received by FAA

    The FAA has received reports indicating that the chrome plating 
separated from reworked cylinder bores of the aileron/elevator power 
control units (PCU's). Investigation revealed that a number of aileron/
elevator and rudder PCU's were repaired using chrome plating on the 
aluminum cylinder bores. Separation of the chrome plating has occurred 
on several of these repaired units, which can result in contamination 
of hydraulic fluid from chrome plating chips. Such contamination could 
result in blocked or jammed valves in the rudder PCU, which could 
result in reduced movement capability of the rudder or partial or total 
deflection of the rudder. In addition, such contamination could result 
in scored piston seals or cylinder bores and consequent reduced 
performance of the aileron/elevator PCU's. A reduced rate of movement 
of the elevator, aileron, or rudder, if not corrected, could result in 
reduced controllability of the airplane.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Letter 737-SL-27-
30, dated April 1, 1985, which describes procedures for an inspection 
of the aileron/elevator PCU's and the rudder PCU to determine if 
reworked PCU manifold cylinder bores containing chrome plating are 
installed, and replacement of the cylinder bores with bores that have 
been reworked using the oversize method or the steel sleeve method, if 
necessary.

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 an inspection of the aileron/elevator PCU's 
and the rudder PCU to determine if reworked PCU manifold

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cylinder bores containing chrome plating are installed, and replacement 
of the cylinder bores with bores that have been reworked using the 
oversize method or the steel sleeve method, if necessary. The actions 
would be required to be accomplished in accordance with the service 
letter described previously.

Explanation of Proposed Compliance Time

    In developing an appropriate compliance time for the proposed 
actions, the FAA's intent is that they 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. In 
light of these considerations, the FAA has specified a compliance time 
of 18 months for accomplishment of the proposed inspection. 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 the proposed compliance time will provide an 
acceptable level of safety.

Cost Impact

    There are approximately 2,675 Model 737 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 1,091 
airplanes of U.S. registry would be affected by this proposed AD, that 
it would take approximately 5 work hours per airplane to accomplish the 
proposed inspection, and that the average labor rate is $60 per work 
hour. Based on these figures, the cost impact of the proposed AD on 
U.S. operators is estimated to be $327,300, or $300 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.
    Should an operator be required to accomplish the necessary 
replacement, it would take approximately 18 work hours per airplane to 
accomplish, at an average labor rate of $60 per work hour. Required 
parts will cost approximately $15,800 per airplane. Based on these 
figures, the cost impact of any necessary replacement action is 
estimated to be $16,880 per airplane.

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-150-AD.

    Applicability: All Model 737-100, -200, -300, -400, and -500 
series airplanes, 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 (d) 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 a reduced rate of movement of the elevator, aileron, 
or rudder, which, if not corrected, could result in reduced 
controllability of the airplane, accomplish the following:
    (a) Within 18 months after the effective date of this AD: 
Perform an inspection of the aileron and elevator PCU's, part number 
(P/N) 65-44761-( ), and the rudder PCU, P/N 65-44681-( ), to 
determine if reworked PCU manifold cylinder bores containing chrome 
plating are installed, in accordance with Boeing Service Letter 737-
SL-27-30, dated April 1, 1985.
    (b) If any reworked PCU manifold cylinder bores containing 
chrome plating are installed: Prior to further flight, replace the 
cylinder bores with bores that have been reworked using the oversize 
method or the steel sleeve method specified in Boeing Service Letter 
737-SL-27-30, dated April 1, 1985. Accomplish the replacement in 
accordance with the service letter.
    (c) As of the effective date of this AD, no person shall install 
a reworked PCU manifold cylinder bore containing chrome plating on 
an aileron or elevator PCU having P/N 65-44761-( ), or on a rudder 
PCU having P/N 65-44681-( ), of any airplane unless the cylinder 
bore has been reworked using the oversize method or the steel sleeve 
method specified in Boeing Service Letter 737-SL-27-30, dated April 
1, 1985.
    (d) 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.

    (e) 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. 96-21882 Filed 8-23-96; 9:02 am]
BILLING CODE 4910-13-U