[Federal Register Volume 62, Number 125 (Monday, June 30, 1997)]
[Rules and Regulations]
[Pages 35068-35072]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-16852]



[[Page 35068]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-29-AD; Amendment 39-10061; AD 97-14-04]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100, -200, -300, -400, 
and -500 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment supersedes two existing airworthiness 
directives (AD), applicable to certain Boeing Model 737 series 
airplanes, that currently require tests of the main rudder power 
control unit (PCU) to detect excessive internal leakage of hydraulic 
fluid, stalling, or reversal, and to verify proper operation of the 
PCU; and replacement of the PCU with a unit having a different part 
number, if necessary. This amendment adds requirements for replacement 
of the PCU and the vernier control rod bolts with newly designed units. 
This amendment also adds a requirement for leak tests of the PCU, and 
replacement of the PCU with a serviceable or newly designed unit, if 
necessary. This amendment is prompted by reports of fracturing of the 
vernier control rod bolts as a result of the shank of the bolt running 
into the threads on the nutplate during installation of the rod. The 
actions specified by this AD are intended to prevent such fracturing, 
which could result in uncommanded movements of the rudder, and 
consequent reduced controllability of the airplane.

DATES: Effective August 4, 1997.
    The incorporation by reference of Boeing Alert Service Bulletin 
737-27A1202, evision 1, dated December 6, 1996, as listed in the 
regulations, is approved by the Director of the Federal Register as of 
August 4, 1997.
    The incorporation by reference of Boeing Service Letter 737-SL-27-
8-B, dated July 13, 1993, as listed in the regulations, was approved 
previously by the Director of the Federal Register as of March 3, 1994 
(59 FR 4570, February 1, 1994).
    The incorporation by reference of Boeing Alert Service Bulletin 
737-27A1202, dated November 1, 1996, as listed in the regulations, was 
approved previously by the Director of the Federal Register as of 
November 27, 1996 (61 FR 59317, November 22, 1996).

ADDRESSES: The service information referenced in this AD may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the Federal 
Aviation Administration (FAA), transport Airplane Directorate, Rules 
Docket, 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, Seattle Aircraft 
Certification Office, 1601 Lind Avenue, SW., Renton, Washington; 
telephone (425) 227-2673; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) by superseding both AD 94-01-07, 
amendment 39-8789 (59 FR 4570, February 1, 1994), and AD 96-23-51, 
amendment 39-9818 (61 FR 59317, November 22, 1996), was published in 
the Federal Register on March 14, 1997 (62 FR 12126). Both of the 
existing AD's are applicable to various Boeing Model 737 series 
airplanes.
    The NPRM proposed to continue to require tests of the main rudder 
power control unit (PCU) to detect excessive internal leakage of 
hydraulic fluid, stalling, or reversal, and to verify proper operation 
of the PCU; and replacement of the PCU with a unit having a different 
part number, if necessary. The NPRM also proposed to require 
replacement of the PCU and vernier control rod bolts with newly 
designed units; epetitive leak tests of the PCU; and replacement of the 
PCU with a serviceable or newly designed unit, if necessary.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Support for the Proposal

    One commenter supports the proposed rule.

Request to Extend the Comment Period of the Proposal

    Several commenters request an extension of the public comment 
period for the proposed AD. These commenters state that such an 
extension will enable operators to better understand the issues 
surrounding the proposed actions and to review recent material 
presented by Boeing and comments submitted by the National 
Transportation Safety Board (NTSB) in response to Rules Docket No. 96-
NM-266-AD.
    The FAA does not concur. The FAA has considered the degree of 
urgency associated with addressing the identified unsafe condition of 
the rudder PCU, and the amount of time that has already elapsed since 
issuance of the original proposed rule. In light of these items, the 
FAA has determined that further delay of this final rule is not 
appropriate.

Request to Delay Issuance of Final Rule

    One commenter requests that the FAA delay issuance of the final 
rule until Boeing can release the service bulletins containing 
procedures for replacement of the main rudder PCU and vernier control 
rod bolts with newly designed units. The commenter states that neither 
Boeing nor its suppliers have completed engineering the proposed design 
changes; therefore, the commenter is unable to provide meaningful or 
technically relevant comments regarding the actions specified in the 
proposed AD.
    The FAA does not concur with the commenter's request. In light of 
the critical nature of the addressed unsafe condition, the FAA does not 
consider that delaying this action until after release of Boeing's 
planned service bulletins is warranted. Furthermore, the FAA disagrees 
with the commenter's assertion that it is unable to submit meaningful 
comments on this AD until Boeing's design changes are completed. On the 
contrary, the proposed AD provided extensive information on the nature 
of the unsafe condition, the proposed corrective actions, and the 
proposed compliance times for those actions. The only information not 
provided (because it was not available) was reference to a specific 
service document providing details on specific methods for 
accomplishing the proposed actions.
    The FAA considers that this proposed AD has complied fully with the 
requirements of the Administrative Procedure Act to provide the public 
with a reasonable opportunity to comment by including in the proposal 
``either the terms or substance of the proposed rule or a description 
of the subjects and issues involved.''

Request to Reference Latest Boeing Service Bulletin

    One commenter requests that paragraph (c) of the proposed rule be 
revised to reference Revision 1 of Boeing Alert Service Bulletin 737-
27A1020, dated December 6, 1996, and Revision 2 of that alert service 
bulletin (which has not been released yet). The commenter states that 
the terminating action for the requirements of paragraph

[[Page 35069]]

(c) of the proposed AD will be included in Revision 2 of the alert 
service bulletin.
    The FAA concurs partially. Regarding Revision 2 of the service 
bulletin, the FAA does not reference service bulletins that have not 
yet been released in an AD. Office of the Federal Register (OFR) 
regulations require that either the service document contents be 
published as part of the actual AD language; or that the service 
document be submitted for approval by the OFR as ``referenced'' 
material, in which case it may be only referred to in the text of an 
AD. An AD may only refer to a service document that was submitted and 
approved by the OFR for ``incorporation by reference.'' In order for 
operators to use later revisions of a referenced document (issued after 
the publication of an AD), either the AD must be revised to reference 
the specific later revisions, or operators must request the approval of 
the use of them as an alternative method of compliance under the 
provisions of paragraph (i) of this AD.
    Since issuance of the NPRM, the FAA has reviewed and approved 
Boeing Alert Service Bulletin 737-27A1202, Revision 1, dated December 
6, 1996, as an alternative method of compliance for the requirements of 
paragraph (c) of the AD. The FAA has revised paragraph (c) of this 
final rule to include Revision 1 of the alert service bulletin as an 
additional source of service information.

Requests to Revise the Compliance Time for New Requirements

    Several commenters request a revision to the proposed compliance 
time of 2 years for accomplishment of the new requirements of this 
proposed AD:
    One commenter requests that the new requirements proposed by the AD 
be accomplished by December 31, 1997. The commenter states that the 
NTSB and FAA have known about the problems with the rudder PCU since 
1986 or earlier. The commenter asserts that further delays will only 
increase the possibility of another catastrophic accident.
    Two commenters request that the compliance time for accomplishing 
the proposed replacement of the main rudder PCU and the vernier control 
rod bolts be extended from the proposed 2 years. One of these 
commenters requests a compliance time of 3 years. The other commenter 
requests a compliance time of 5 years. One of these commenters states 
that if the functional test of the main rudder PCU [as required by 
paragraph (e) of the proposed AD] requires the phase lag test of the 
yaw damper system to be performed, it will be forced to send all PCU's 
to Parker Hannifin for modification and testing. The same commenter 
suggests that Parker Hannifin does not have the capability to 
manufacture the replacement parts within the proposed compliance time. 
The other commenter points out that Parker Hannifin will be especially 
hard pressed to manufacture the required parts within the proposed 
compliance time.
    One commenter questions, due to past difficulties with vendors and 
parts availability, whether the 2-year compliance time of the subject 
replacement of the proposed AD is feasible.
    The FAA does not concur with any of the commenters' requests. In 
response to the commenter that states the FAA has known about the 
problems associated with the main rudder PCU since 1986 or earlier, the 
FAA finds this statement to be incorrect. The FAA learned of the design 
deficiencies in the main rudder PCU servo valve and control rod bolts 
in the last quarter of 1996. The FAA has determined that Parker 
Hannifin has the capability to manufacture the replacement parts for 
all affected airplanes within the proposed compliance time. In 
addition, the FAA finds that a compliance time of less than 2 years 
would significantly increase the possibility of new design or 
manufacturing errors. Further, the FAA points out that once Boeing has 
developed the design changes for the main rudder PCU servo valve and 
control rod bolts, time will be necessary to test the new design 
changes to ensure those changes meet certification requirements for FAA 
approval.
    In developing an appropriate compliance time for the required 
replacements, the FAA considered not only the degree of urgency 
associated with addressing the unsafe condition, but the availability 
of required parts and the practical aspect of accomplishing the 
replacements within an interval of time that parallels normal scheduled 
maintenance for the majority of affected operators. In consideration of 
all of these factors, the FAA has determined that 2 years represents an 
appropriate interval of time allowable wherein the replacements can be 
accomplished during scheduled maintenance intervals for the majority of 
affected operators, and an acceptable level of safety can be 
maintained.

Request to Revise Part Numbers of PCU's

    One commenter requests that part numbers (P/N) 65-44861-( ) and 
65C37052-( ) of the PCU identified in paragraph (d)(1) of the proposal 
be revised to include P/N's 65-44861-10 and 65C36052-10, respectively. 
The commenter states that -10 P/N's were addressed in Notice of Status 
Change 737-27-1185 NSC1, dated May 27, 1993, which was incorporated 
into Boeing Service Bulletin 737-27-1185, Revision 1, dated April 14, 
1994.
    The FAA does not concur. The symbol ``( )'' at the end of the 
subject P/N's indicates any dash number. Therefore, P/N's 65-44861-10 
and 65C36052-10 are affected by the requirements of paragraph (d)(1) of 
the final rule.

Request to Add a New Requirement

    One commenter states that the vernier control rod must be replaced 
or reworked at the same time the bolts are replaced in order to replace 
the two nutplates. The commenter notes that this action is not included 
in the proposed AD. From this comment, the FAA infers that the 
commenter is requesting that paragraph (d)(2) of the proposed AD be 
revised to include a requirement to replace or rework the vernier 
control rod.
    The FAA does not concur. The FAA acknowledges that replacing the 
two nutplates could correct the bolt design deficiency; however, such a 
design change has not been submitted to the FAA for approval. However, 
under the provisions of paragraph (i) of the final rule, the FAA may 
consider requests for approval of an alternative method of compliance 
if sufficient data are submitted to substantiate that such a design 
change would provide an acceptable level of safety.

Request to Revise Reference to Vernier Control Rod Bolt

    One commenter requests that reference to a vernier control rod 
``bolt'' (singular) be changed to ``bolts'' (plural) throughout the 
proposal. The commenter states that there are two bolts--one on each 
end of the rod. The FAA concurs with this suggestion and has revised 
the final rule accordingly.

Request to Incorporate the Leak Test Into the Maintenance Program

    One commenter requests that the leak test required by paragraph (e) 
of the proposed AD be incorporated into each operator's FAA-approved 
maintenance program as terminating action for the requirements of that 
paragraph.
    The FAA concurs. The FAA finds that revising the FAA-approved 
maintenance program to require an FAA-approved leak test may be 
accomplished as an optional terminating action for the repetitive leak 
test requirements of paragraph (e) of the final rule. Therefore, the 
FAA has added a new

[[Page 35070]]

paragraph (f) to this final rule to provide for this option.

Request to Extend Repetitive Interval for Leak Test

    One commenter requests that the repetitive intervals for the leak 
test [specified in paragraphs (e)(1) and (e)(2) of the proposed AD] be 
extended from the proposed 6,000 flight hours to 6,400 flight hours. 
The commenter states that such an extension will coincide with the 
interval of the ``2C'' maintenance check for Boeing Model 737-300, -
400, and -500 series airplanes.
    The FAA concurs. The FAA's intent was that the specified intervals 
coincide with the ``2C'' maintenance check. Accordingly, the FAA has 
revised paragraphs (e)(1) and (e)(2) of the final rule to specify this 
revised repetitive interval.

Request To Accept Previously Approved Alternative Methods of 
Compliance

    One commenter states that the leak test specified in Boeing Service 
Letter 737-SL-27-91 was considered acceptable as an alternative method 
of compliance (AMOC) in accordance with AD 94-01-07. The commenter 
questions whether the FAA will continue to accept that AMOC, or whether 
it will be necessary to apply for approval of a new AMOC.
    The FAA has not approved a leak test as an AMOC for the 
requirements of this AD. However, the FAA may consider requests for 
approval of the subject leak test as an AMOC if sufficient data are 
submitted to substantiate that such a test would provide an acceptable 
level of safety.

Request to Add a Requirement for the Control Rod and Its Bolts

    One commenter requests that an identical requirement to that of 
paragraph (f) of the proposed AD [designated as paragraph (g) in the 
final rule] be included in the final rule for the control rod and its 
bolts.
    The FAA concurs. The FAA inadvertently omitted such a requirement 
for the control rod and its bolts from the proposal. The FAA's intent 
was to include a requirement that states, ``Once a newly designed 
vernier control rod bolt specified in paragraph (d)(2) of this AD is 
installed on an airplane, no operator shall install on that airplane 
any bolt other than such a newly designed bolt.'' Therefore, the FAA 
has added a new paragraph (h) to the final rule to include such a 
requirement.
    This new paragraph (h) simply states the effect of Section 39.3 of 
part 39 of the Federal Aviation Regulations (14 CFR 39.3), which 
provides, ``No person may operate a product to which an airworthiness 
directive applies except in accordance with the requirements of that 
airworthiness directive.'' Thus, once an operator has complied with 
paragraph (d)(2) of this AD, it is required to continue to operate in 
compliance with that paragraph. As a result, this new paragraph (h) 
does not impose an additional burden on any operator.

FAA's Conclusion

    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the changes previously 
described. The FAA has determined that these changes will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.

Cost Impact

    There are approximately 2,900 Boeing Model 737 series airplanes of 
the affected design in the worldwide fleet. The FAA estimates that 
1,350 airplanes of U.S. registry will be affected by this AD.
    The tests that are currently required by AD 94-01-07 take 
approximately 8 work hours per airplane to accomplish, at an average 
labor rate of $60 per work hour. Based on these figures, the cost 
impact of the currently required tests on U.S. operators is estimated 
to be $648,000, or $480 per airplane, per test.
    The replacement that is currently required by AD 94-01-07 takes 
approximately 20 work hours per airplane to accomplish, at an average 
labor rate of $60 per work hour. Required parts will be supplied by the 
manufacturer at no cost to operators. Based on these figures, the cost 
impact of the currently required replacement on U.S. operators is 
estimated to be $1,620,000, or $1,200 per airplane.
    The tests that are currently required by AD 96-23-51 take 
approximately 2 work hours per airplane to accomplish, at an average 
labor rate of $60 per work hour. Based on these figures, the cost 
impact of the currently required tests on U.S. operators is estimated 
to be $162,000, or $120 per airplane, per test.
    The replacement of the PCU that is required by this AD action takes 
approximately 9 work hours per airplane to accomplish, at an average 
labor rate of $60 per work hour. Required parts will be supplied by the 
manufacturer at no cost to operators. Based on these figures, the cost 
impact of the required replacement of the PCU on U.S. operators is 
estimated to be $729,000, or $540 per airplane.
    The replacement of the vernier control rod bolts that is required 
by this AD action takes approximately 1 work hour per airplane to 
accomplish, at an average labor rate of $60 per work hour. Required 
parts will be supplied by the manufacturer at no cost to operators. 
Based on these figures, the cost impact of the required replacement of 
the vernier control rod bolts on U.S. operators is estimated to be 
$81,000, or $60 per airplane.
    The leak tests that are required in this AD action take 
approximately 8 work hours per airplane to accomplish, at an average 
labor rate of $60 per work hour. Based on these figures, the cost 
impact of the required leak test on U.S. operators is estimated to be 
$648,000, or $480 per airplane, per leak test.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the 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 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.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it 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

[[Page 35071]]

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 removing amendments 39-8789 (59 FR 
4570, February 1, 1994) and 39-9818 (61 FR 59317, November 22, 1996), 
and by adding a new airworthiness directive (AD), amendment 39-10061, 
to read as follows:

97-14-04  Boeing: Amendment 39-10061. Docket 97-NM-29-AD. Supersedes 
AD 94-01-07, Amendment 39-8789, and AD 96-23-51, Amendment 39-9818.

    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 (i) 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 uncommanded movements of the rudder, and consequent 
reduced controllability of the airplane, accomplish the following:

Restatement of Requirements of AD 94-01-07

    (a) Within 750 flight hours after March 3, 1994 (the effective 
date of AD 94-01-07, amendment 39-8789), perform a test of the main 
rudder PCU, part number 65-44861-2/-3/-4/-5/-6/-7/-8/-9, to detect 
internal leakage of hydraulic fluid, in accordance with Boeing 
Service Letter 737-SL-27-82-B, dated July 13, 1993.
    (1) If no discrepancy, as described in paragraph 3.B. of the 
Service Letter, is detected, repeat the test at intervals not to 
exceed 750 flight hours.
    (2) If any discrepancy, as described in paragraph 3.B. of the 
Service Letter, is detected during any check, prior to further 
flight, accomplish either paragraph (a)(2)(i) or (a)(2)(ii) of this 
AD:
    (i) Replace the main rudder PCU with a serviceable PCU in 
accordance with the Model 737 Overhaul Manual. After such 
replacement, repeat the test at intervals not to exceed 750 flight 
hours.
    (ii) Replace the main rudder PCU with a new main rudder PCU 
having part number 65-44861-11 or 65C37052-2/-3/-4/-5/-6/-7/-8/-9, 
in accordance with Boeing Service Bulletin 737-27-1185, dated April 
15, 1993. Such replacement constitutes terminating action for the 
tests required by paragraph (a) of this AD.
    (b) Replacement of the main rudder PCU, part number 65-44861-( 
), with a new main rudder PCU having part number 65-44861-11 or 
65C37052-2/-3/-4/-5/-6/-7/-8/-9, in accordance with Boeing Service 
Bulletin 737-27-1185, dated April 15, 1993, constitutes terminating 
action for the tests required by paragraph (a) of this AD.

Restatement of Requirements of AD 96-23-51

    (c) Within 10 days after November 27, 1996 (the effective date 
of AD 96-23-51, amendment 39-9818), perform a test to verify proper 
operation of the rudder PCU, in accordance with Boeing Alert Service 
Bulletin 737-27A1202, dated November 1, 1996, or Revision 1, dated 
December 6, 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.

New Requirements of This AD

    (d) Within 2 years after the effective date of this AD, 
accomplish paragraphs (d)(1) and (d)(2) of this AD in accordance 
with a method approved by the Manager, Seattle Aircraft 
Certification Office (ACO), FAA, Transport Airplane Directorate. 
Accomplishment of these actions terminates the requirements of 
paragraphs (a), (b), and (c) of this AD.
    (1) Replace any main rudder PCU having Boeing part number (P/N) 
65-44861-() or P/N 65C37052-() with a new main rudder PCU that has 
been approved by the Manager, Seattle ACO.
    (2) Replace the vernier control rod bolts having Boeing P/N 69-
27229-() with new bolts that have been approved by the Manager, 
Seattle ACO.
    (e) Perform a leak test of the main rudder PCU in accordance 
with a method approved by the Manager, Seattle ACO, at the 
applicable times specified in paragraph (e)(1) or (e)(2) of this AD. 
If any discrepancy is found, prior to further flight, replace the 
PCU with a serviceable or newly designed unit in accordance with a 
method approved by the Manager, Seattle ACO.

    Note 2: If the PCU is replaced in accordance with the 
requirements of paragraph (e) prior to accomplishing the replacement 
required by paragraph (d) of this AD, ``serviceable'' includes the 
newly designed PCU referenced in paragraph (d)(1) of this AD and 
PCU's having part number 65-44861-11 and 65C37052-2, -3, -4, -5, -6, 
-7, -8, and -9. However, after the PCU has been replaced in 
accordance with paragraph (d)(1) of this AD, ``serviceable'' is 
limited to the newly designed PCU's referenced in that paragraph.

    (1) For airplanes on which the replacement specified in 
paragraph (a)(2)(ii), (b), or (c)(2) of this AD has been 
accomplished prior to the effective date of this AD: Within 4,000 
flight hours after the effective date of this AD, and thereafter at 
intervals not to exceed 6,400 flight hours.
    (2) For airplanes other than those identified in paragraph 
(e)(1) of this AD: Within 6,400 flight hours after accomplishment of 
the replacement required by paragraph (d)(1) of this AD, and 
thereafter at intervals not to exceed 6,400 flight hours.
    (f) Revision of the FAA-approved maintenance program to require 
an FAA-approved leak test constitutes terminating action for the 
repetitive leak test requirements of paragraph (e) of this AD.
    (g) Once a newly designed PCU specified in paragraph (d)(1) of 
this AD is installed on an airplane, no operator shall install on 
that airplane any PCU other than such a newly designed unit.
    (h) Once a newly designed vernier control rod bolt specified in 
paragraph (d)(2) of this AD is installed on an airplane, no operator 
shall install on that airplane any bolt other than such a newly 
designed bolt.
    (i) 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.

    (j) 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.
    (k) The actions shall be done in accordance with Boeing Service 
Letter 737-SL-27-82-B, dated July 13, 1993; Boeing Alert Service 
Bulletin 737-27A1202, dated November 1, 1996; and Boeing Alert 
Service Bulletin 737-27A1202, Revision 1, dated December 6, 1996. 
The incorporation by reference of Boeing Service Letter 737-SL-27-
82-B, dated July 13, 1993, as listed in the regulations, was 
approved previously by the Director of the Federal Register as of 
March 3, 1994 (59 FR 4570, February 1, 1994). The incorporation by 
reference of Boeing Alert Service 737-27A1202, dated November 1, 
1996, as listed in the regulations, was approved previously by the 
Director of the Federal Register as of November 27, 1996 (61 FR 
59317, November 22, 1996). The incorporation by reference of Boeing 
Alert Service Bulletin 737-27A1202, Revision 1, dated December 6, 
1996, is 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

[[Page 35072]]

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.
    (l) This amendment becomes effective on August 4, 1997.

    Issued in Renton, Washington, on June 23, 1997.
S.R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-16852 Filed 6-27-97; 8:45 am]
BILLING CODE 4910-13-U