[Federal Register Volume 64, Number 8 (Wednesday, January 13, 1999)]
[Proposed Rules]
[Pages 2161-2164]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-682]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-383-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737 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 series 
airplanes. This proposal would require repetitive displacement tests of 
the secondary slide in the dual concentric servo valve of the power 
control unit (PCU) for the rudder, and replacement of the valve 
assembly with a modified valve assembly, if necessary. This proposal is 
prompted by reports of cracking found in PCU secondary servo valve 
slides. The actions specified by the proposed AD are intended to 
prevent failure of the secondary slide and consequent rudder hardover 
and reduced controllability of the airplane.

DATES: Comments must be received by February 12, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-383-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: R.C. Jones, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane 
Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, 
SW., Renton, Washington 98055-4056; telephone (425) 227-1118; fax (425) 
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.

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    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 98-NM-383-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-114, Attention: Rules 
Docket No. 98-NM-383-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received reports of cracking found on Boeing Model 737 
series airplanes on one of the two legs of the clevis of the secondary 
slide, which is a component of the dual servo valve in the power 
control unit (PCU) of the rudder. Most of the cracks were found during 
the manufacturing process by the PCU supplier. However, some of the 
cracks were found on servo valve assemblies by operators; those 
assemblies had not yet been installed in PCU's. Test results have 
indicated that a crack in one leg of the secondary slide is not in 
itself an unsafe condition. However, a crack in the other leg of that 
same slide could cause the slide to break apart and allow a loose part 
to jam both the primary and secondary slides within the valve assembly. 
This condition, if not corrected, could result in rudder hardover and 
reduced controllability of the airplane.

Other Relevant Rulemaking

    Related AD 97-14-04, amendment 39-10061 (62 FR 35068, June 30, 
1997), applicable to all Boeing Model 737-100, -200, -300, -400, and -
500 series airplanes, requires the following actions:
     Tests of the main rudder PCU to detect excessive internal 
leakage of hydraulic fluid, stalling, or reversal, and to verify proper 
operation of the PCU;
     Replacement of the PCU with a unit having a different part 
number, if necessary (the new PCU incorporates a redesigned valve 
assembly);
     Replacement of the PCU and the vernier control rod bolts 
with newly designed units; and
     Leak tests of the PCU, and replacement of the PCU with a 
serviceable or newly designed unit, if necessary.

Explanation of Relevant Service Information

    The FAA has reviewed and approved a draft of Boeing Alert Service 
Bulletin 737-27A1221, dated January 14, 1999 (for Boeing Model 737-100, 
-200, -300, -400, and -500 series airplanes); and a draft of Boeing 
Alert Service Bulletin 737-27A1222, dated January 14, 1999 (for Boeing 
Model 737-600, -700, and -800 series airplanes). [Although these alert 
service bulletins will not be published until after this proposed AD 
has been issued, they are not expected to be substantively different 
from the drafts that have been approved. Copies of these drafts have 
been placed in the rulemaking docket.] These draft alert service 
bulletins describe procedures for a displacement test of the secondary 
slide in the dual concentric servo valve of the rudder PCU, criteria 
for passing the test, and procedures for replacement of any discrepant 
valve assembly with one having a slide that passes the displacement 
test. Accomplishment of the actions specified in the draft alert 
service bulletins is intended to adequately address the identified 
unsafe condition.
    Boeing Alert Service Bulletin 737-27A1222 refers to Parker Service 
Bulletin 381500-27-01, dated December 22, 1998, as an additional source 
of service information for accomplishment of the displacement test for 
Model 737-600, -700, -800, and -900 series airplanes.

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 accomplishment of the actions specified in 
the draft alert service bulletins described previously, except as 
discussed in the ``Differences Between Proposed Rule and Draft Alert 
Service Bulletins'' section of this proposed AD. The proposed AD also 
would require that operators report results of inspection findings to 
the FAA and submit failed valve assemblies to Parker Hannifin 
Corporation (the PCU manufacturer).

Interim Action

    This is considered to be interim action until final action is 
identified, at which time the FAA may consider further rulemaking.

Differences Between Proposed Rule and Draft Alert Service Bulletins

    Operators should note that, while the draft alert service bulletins 
do not recommend that the displacement test be repeated, the FAA has 
determined that the proposed AD should be considered interim action 
until the root cause of the cracking can be determined or a final 
action identified. As a result, the proposed AD would require 
accomplishment of the displacement test at regular intervals.
    In addition, while this proposed AD is applicable to all Boeing 
Model 737 series airplanes, the effectivity of the alert service 
bulletins is limited to airplanes with certain line numbers. Because 
this proposed AD is interim action and a final action has not yet been 
identified to adequately address the identified unsafe condition, it 
will be necessary to repeat the displacement test on all Model 737 
series airplanes, including airplanes that are produced subsequent to 
those with line numbers specified in the draft alert service bulletins.
    Further, although draft Boeing Alert Service Bulletin 737-27A1221 
specifies that the manufacturer may be contacted for disposition of 
certain corrective actions, this proposal would require those 
corrective actions to be accomplished in accordance with a method 
approved by the FAA.

Cost Impact

    There are approximately 3,059 airplanes of the affected design in 
the worldwide fleet. The FAA estimates that 1,334 airplanes of U.S. 
registry would be affected by this proposed AD, that it would take 
approximately 1 work hour per airplane to accomplish the proposed 
displacement test, 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 $80,040, or $60 per airplane, per 
test cycle.
    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.
    The proposed test requires that the PCU be removed from the 
airplane. It would take approximately 9 work hours to remove and 
reinstall or replace the PCU. For Model 737-100, -200, -300, -400, and 
-500 series airplanes, concurrent accomplishment of this proposed AD 
and AD 97-14-04 would preclude the necessity to accomplish this 
replacement action twice, thereby offsetting the cost impact on 
operators.

Regulatory Impact

    The regulations proposed herein would not have substantial direct 
effects on the States, on the relationship

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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 98-NM-383-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 (e) 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 failure of the secondary servo valve slide in the 
rudder power control unit (PCU) due to cracking of the slide, and 
consequent rudder hardover and reduced controllability of the 
airplane, accomplish the following:
    (a) Perform a displacement test of the secondary slide in the 
dual servo valve in the rudder PCU, in accordance with Boeing Alert 
Service Bulletin 737-27A1221, dated January 14, 1999 (for Model 737-
100, -200, -300, -400, and -500 series airplanes); or 737-27A1222, 
dated January 14, 1999 (for Model 737-600, -700, -800, and -900 
series airplanes); at the applicable time specified by paragraph 
(a)(1), (a)(2), (a)(3), (a)(4), or (a)(5) of this AD. Repeat the 
displacement test on that PCU thereafter at intervals not to exceed 
12,000 flight hours.
    (1) For Model 737-100, -200, -300, -400, and -500 series 
airplanes on which the PCU replacement required by paragraph (d)(1) 
of AD 97-14-04, amendment 39-10061 (62 FR 35068, June 30, 1997), has 
been accomplished prior to the effective date of this AD: Conduct 
the displacement test within 4 months after the effective date of 
this AD.
    (2) For Model 737-100, -200, -300, -400, and -500 series 
airplanes on which the PCU installation required by paragraph (d)(1) 
of AD 97-14-04 has not been accomplished prior to the effective date 
of this AD: Prior to installing the PCU required by AD 97-14-04, 
conduct the displacement test on that PCU as required by this 
paragraph of this AD.
    (3) For airplanes equipped with a PCU having part number 65-
44861-12 and having serial number (S/N) 3509A or lower: Conduct the 
displacement test within 4 months after the effective date of this 
AD.
    (4) For Model 737-600, -700, and -800 series airplanes having 
line numbers 1 through 222 inclusive: Conduct the displacement test 
within 4 months after the effective date of this AD.
    (5) For all other airplanes: Conduct the displacement test prior 
to the accumulation of 12,000 flight hours on the PCU, or within 30 
days after the effective date of this AD, whichever occurs later.
    (b) If the results of the displacement test required by 
paragraph (a) of this AD are outside the limits specified by Boeing 
Alert Service Bulletin 737-27A1221, dated January 14, 1999 (for 
Model 737-100, -200, -300, -400, and -500 series airplanes), or 737-
27A1222, dated January 14, 1999 (for Model 737-600, -700, -800, and 
-900 series airplanes): Prior to further flight, accomplish the 
actions specified in paragraphs (b)(1) and (b)(2) of this AD.
    (1) Replace the valve assembly, in accordance with the 
applicable alert service bulletin, with a serviceable valve 
assembly. And
    (2) Following installation of the replacement valve assembly in 
accordance with paragraph (b)(1) of this AD, perform the 
displacement test required by paragraph (a) of this AD on that 
assembly, in accordance with the applicable alert service bulletin. 
If the test results are outside the limits specified by the 
applicable alert service bulletin, prior to further flight, perform 
corrective action in accordance with a method approved by the 
Manager, Seattle Aircraft Certification Office, FAA, Transport 
Airplane Directorate.

    Note 2: Boeing Alert Service Bulletin 737-27A1222 refers to 
Parker Service Bulletin 381500-27-01, dated December 22, 1998, as an 
additional source of service information for accomplishment of the 
displacement test for Model 737-600, -700, -800, and -900 series 
airplanes.

    (c) As of the effective date of this AD, no person shall install 
on any airplane a main rudder PCU having serial number (S/N) 3509A 
or lower (for Model 737-100, -200, -300, -400, and -500 series 
airplanes) or S/N 0299 or lower (for Model 737-600, -700, -800, and 
-900 series airplanes) unless that PCU's nameplate has been vibro-
engraved with the letter ``C'' following the serial number.
    (d)(1) Within 10 days after accomplishing the displacement test 
required by paragraph (a) of this AD: Submit a report of inspection 
findings to the Manager, Seattle Aircraft Certification Office 
(ACO), FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056; fax (425) 227-1181. The report must 
include the inspection results (both positive and negative 
findings), test data for any failed actuators, a description of any 
discrepancies found, the part number and serial number of each 
actuator tested, and the airplane serial number.
    (2) Within 10 days after accomplishing the displacement test 
required by paragraph (a) of this AD: Submit failed valve assemblies 
for analysis to Parker Hannifin Corporation, Chief Engineer, 
Customer Support Operations, 16666 Von Karman Avenue, Irvine, 
California 92606.
    (3) 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.
    (e) 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 ACO. 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.

    (f) 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.


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    Issued in Renton, Washington, on January 6, 1999.
John J. Hickey,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-682 Filed 1-12-99; 8:45 am]
BILLING CODE 4910-13-U