[Federal Register Volume 61, Number 227 (Friday, November 22, 1996)]
[Rules and Regulations]
[Pages 59317-59319]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-29260]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-261-AD; Amendment 39-9818; AD 96-23-51]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This document publishes in the Federal Register an amendment 
adopting Airworthiness Directive (AD) T96-23-51 that was sent 
previously to all known U.S. owners and operators of Boeing Model 737 
series airplanes by individual telegrams. This AD requires repetitive 
tests to verify proper operation of the rudder power control unit 
(PCU), and replacement of the PCU, if necessary. This amendment is 
prompted by tests of the main rudder PCU, conducted by the 
manufacturer, which demonstrated a potential failure scenario that was 
previously unknown. The actions specified by this AD are intended to 
prevent rudder motion in the opposite direction of the rudder command.

DATES: Effective November 27, 1996, to all persons except those persons 
to whom it was made immediately effective by telegraphic AD T96-23-51, 
issued November 1, 1996, which contained the requirements of this 
amendment.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of November 27, 1996.
    Comments for inclusion in the Rules Docket must be received on or 
before January 21, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 96-NM-261-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056.
    The applicable service information 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; or at the 
Office of the Federal Register, 800 North Capitol Street, NW., suite 
700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Kenneth W. Frey, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane 
Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; 
telephone (206) 227-2673; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION: As part of its Continuing Operational Safety 
Program, the FAA has become aware of new information related to the 
safety of Boeing Model 737 series airplanes. Recent tests of the main 
rudder power control unit (PCU), conducted at Boeing, demonstrated a 
potential failure scenario that was previously unknown. These tests 
revealed that rudder pedal input can cause deformation in the linkage 
leading to the primary and secondary slides of the servo valve of the 
main rudder PCU, if the secondary slide of the PCU jams in certain 
positions; this situation could result in rudder motion in the opposite 
direction of the rudder command.
    The intent of the original design of the PCU dual servo valve, in 
compliance with certification requirements, is to allow either the 
primary or secondary slide to neutralize the effect of a jam of the 
other slide. If the secondary slide of the servo valve of the main 
rudder PCU jams and the primary slide does not neutralize the effects 
of the jam, under certain conditions, a rudder pedal command could 
result in rudder motion in the opposite direction of the rudder command 
and lead to reduced controllability of the airplane.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletin 
737-27A1202, dated November 1, 1996. The alert service bulletin 
describes procedures for performing a test to verify proper operation 
of the rudder PCU, and replacement of the rudder PCU with a new unit, 
if necessary. The

[[Page 59318]]

test procedure will ensure that the servo valve does not have a latent 
jam.

Explanation of Requirements of the Rule

    Since the unsafe condition described is likely to exist or develop 
on other airplanes of the same type design, the FAA issued Telegraphic 
AD T96-23-51 to prevent rudder motion in the opposite direction of the 
rudder command. The AD requires repetitive tests to verify proper 
operation of the rudder PCU, and replacement of the rudder PCU with a 
new unit, if necessary. The actions are required to be accomplished in 
accordance with the alert service bulletin described previously.
    The AD also requires that operators submit a report of the test 
results to the FAA.
    Since it was found that immediate corrective action was required, 
notice and opportunity for prior public comment thereon were 
impracticable and contrary to the public interest, and good cause 
existed to make the AD effective immediately by individual telegrams 
issued on November 1, 1996, to all known U.S. owners and operators of 
Model 737 series airplanes. These conditions still exist, and the AD is 
hereby published in the Federal Register as an amendment to section 
39.13 of the Federal Aviation Regulations (14 CFR 39.13) to make it 
effective to all persons.

Differences Between the AD and the Relevant Service Information

    Operators should note that the Boeing alert service bulletin 
specifies that it pertains only to airplanes that have certain serial 
numbers. However, this AD (as well as the previously-issued telegraphic 
version of it) is applicable to all Model 737 series airplanes. It is 
the FAA's intent that the entire fleet of Model 737's be inspected in 
accordance with the requirements of this AD. Where there are 
differences between the manufacturer's service information and the AD, 
it is the stipulations of the AD that prevail.

Interim Action

    This is considered to be interim action. The manufacturer has 
advised that it currently is developing a design modification that will 
eliminate the need for the repetitive test requirements of this AD. 
Once this modification is developed, approved, and available, the FAA 
may consider additional rulemaking.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the 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 that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 96-NM-261-AD.'' The postcard will be date stamped and 
returned to the commenter.

Regulatory Impact

    The regulations adopted herein will 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 final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket. 
A copy of it, if filed, may be obtained from the Rules Docket at the 
location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends 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:

96-23-51 Boeing: Amendment 39-9818. Docket 96-NM-261-AD.

    Applicability: All Model 737 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 
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.

    Note 2: The Boeing alert service bulletin that is referenced in 
this AD specifies that it pertains only to airplanes that have 
certain serial numbers. However, this AD is applicable to all Model 
737 series airplanes. Where there are differences between the 
manufacturer's service information and the AD, it is the 
stipulations of the AD that prevail.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent rudder motion in the opposite direction of the rudder 
command, accomplish the following:

[[Page 59319]]

    (a) Within 10 days after the effective date of this AD, perform 
a test to verify proper operation of the rudder power control unit 
(PCU), in accordance with Boeing Alert Service Bulletin 737-27A1202, 
dated November 1, 1996.
    (1) If the rudder PCU operates properly, repeat the test 
thereafter at intervals not to exceed 250 flight hours.
    (2) If the rudder PCU operates improperly, prior to further 
flight, replace the rudder PCU with a new rudder PCU, in accordance 
with the alert service bulletin. Repeat the test thereafter at 
intervals not to exceed 250 flight hours.
    (b) Within 24 hours after accomplishing any test required by 
paragraph (a) of this AD, submit a report of any finding(s) of 
discrepancies to the Manager, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone 
(206) 227-2673; fax (206) 227-1181. Information collection 
requirements contained in this regulation have been approved by the 
Office of Management and Budget (OMB) under the provisions of the 
Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and have 
been assigned OMB Control Number 2120-0056.
    (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 3: 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.
    (e) The actions shall be done in accordance with Boeing Alert 
Service Bulletin 737-27A1202, dated November 1, 1996. This 
incorporation by reference was approved by the Director of the 
Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 
51. Copies may be obtained from Boeing Commercial Airplane Group, 
P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be 
inspected at the FAA, Transport Airplane Directorate, 1601 Lind 
Avenue, SW., Renton, Washington; or at the Office of the Federal 
Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
    (f) This amendment becomes effective on November 27, 1996, to 
all persons except those persons to whom it was made immediately 
effective by telegraphic AD T96-23-51, issued on November 1, 1996, 
which contained the requirements of this amendment.

    Issued in Renton, Washington, on November 7, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-29260 Filed 11-21-96; 8:45 am]
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