AD Amdt-39-9790

[Federal Register Volume 61, Number 216 (Wednesday, November 6, 1996)]
[Rules and Regulations]
[Pages 57291-57295]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 96-26952]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

RIN 2120-AA64
[Docket No. 94-NM-226-AD; Amendment 39-9790; AD 96-22-01]


Airworthiness Directives; Boeing Model 747-200, -300, and -400 
Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain Boeing Model 747-200, -300, and -400 series 
airplanes, that requires modification of the left and right inboard 
elevator servo assemblies and the hydraulic routing of the right 
inboard elevator power control package (PCP). This amendment is 
prompted by a report of an uncommanded right elevator deflection after 
takeoff and reports of elevator/control column bumps during landing 
gear retraction on these airplanes. The actions specified by this AD 
are intended to prevent uncommanded elevator deflection, which could 
result in structural damage and reduced controllability of the 
airplane.

DATES: Effective December 6, 1996.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of December 6, 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; and Parker Hannifin Corporation, Customer 
Support Operations, 16666 Von Karman Avenue, Irvine, California 92714. 
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: Kristin Larson, 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 (206) 227-1760; fax (206) 
227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to certain Boeing Model 747 series 
airplanes was published as a supplemental Notice of Proposed Rulemaking 
(NPRM) in the Federal Register on December 11, 1995 (60 FR 63465). That 
action proposed to require modification of the left and right inboard 
elevator servo assemblies and the hydraulic routing of the right 
inboard elevator power control package (PCP).

Comments

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Requests To Extend the Compliance Time for Hydraulic Tubing 
Modification

    Two commenters request that the compliance time for accomplishing 
the proposed modification of the hydraulic tubing of the right inboard 
elevator PCP be extended from the proposed 1 year to 18 months. The 
commenters state that such an extension will allow the modification to 
be accomplished during a regularly scheduled ``C'' or ``D'' check, and 
thereby eliminate any additional expenses that would be associated with 
special scheduling.
    One of these commenters notes that it had submitted an identical 
request to the FAA during the comment period for the original NPRM, but 
the FAA denied this request, in part, because it ``determined that a 
heavy maintenance visit is not required to accomplish the 
modification.'' The commenter states that the proposed modification 
requires draining and purging of the stabilizer fuel tank, which is not 
an activity suited for a line or field maintenance environment. 
Additionally, access to remove the elevator actuator and modify the 
hydraulic tubing on the stabilizer aft spar would be difficult to 
accomplish during line maintenance or at a field maintenance facility.

[[Page 57292]]

    The FAA does not concur with the commenters' request to extend the 
compliance time. The FAA agrees that, due to the complexity of the 
modification, it should be performed at a facility where special 
equipment and trained maintenance personnel will be available, if 
necessary. However, the FAA points out that the compliance time of one 
year was developed in consideration of not only the degree of urgency 
associated with addressing the unsafe condition, but such factors as 
the manufacturer's recommendations, the availability of required parts, 
and the practical aspect of installing the required modification within 
an interval of time that parallels normal scheduled maintenance for the 
majority of affected operators. In consideration of all of these 
factors, and in consideration of the amount of time that has already 
elapsed since issuance of the original NPRM, the FAA has determined 
that further delay of this modification is not appropriate.
    However, under the provisions of paragraph (c) of the final rule, 
the FAA may approve requests for adjustments to the compliance time if 
sufficient data are submitted to substantiate that such an adjustment 
would provide an acceptable level of safety.

Requests To Extend the Compliance Time for Servo Assembly 
Modification

    Several commenters request that the compliance time for 
accomplishing the proposed modification of the left and right servo 
assemblies of the inboard elevator PCP be extended from the proposed 3 
years to 5 years or, preferably, to 7 years. Some of these commenters 
contend that, due to the complexity and proprietary technology used to 
manufacture the servo valve, Parker (the original equipment 
manufacturer/supplier of the assemblies) is the only facility that is 
qualified to perform the rework and retrofit that would be required by 
the proposed modification. These commenters state that Parker's current 
facility would be unable to support modification of the affected fleet 
within the proposed 3-year compliance time; therefore, additional time 
will be necessary for compliance. One commenter contends that, even if 
other maintenance facilities are available to accomplish the 
modification, a sufficient inventory of parts to support multiple 
repair facilities does not currently exist.
    The FAA does not concur. In developing an appropriate compliance 
time for this modification, the FAA specifically considered the 
availability of required parts as well as the process necessary for 
modifying the affected fleet in an orderly and timely manner. The FAA 
maintains that other facilities will be able to support maintenance of 
the PCP's, even if the spool valve units must be modified only by 
Parker. In consideration of all of these items (as well as the revision 
to the applicability of this requirement, as explained below), the FAA 
finds that a compliance time of 3 years for this modification is 
appropriate. However, under the provisions of paragraph (c) of the 
final rule, the FAA may approve requests for adjustment of the 
compliance time if sufficient data are submitted to substantiate that 
such an adjustment would provide an acceptable level of safety.

Requests To Reconsider Limiting the Applicability of Servo Assembly 
Modification

    Several commenters request that the applicability of proposed 
paragraph (b) (which would require the modification of the left and 
right servo assemblies of the inboard elevator PCP) be limited to only 
Model 747-200 and -300 series airplanes having cumulative line number 
(C/L) 696 and subsequent. These commenters request that airplanes 
having C/L 001 through 695 (which are commonly referred to as 
``classic'' models) and Model 747-400 series airplanes, be exempt from 
this requirement. These commenters bring up three reasons to justify 
this request.
    1. No history of service actuator assembly failures on ``classic'' 
models. Several commenters state that the servo assembly modification 
is unjustified for ``classic'' model airplanes because the entire Model 
747 fleet has accumulated over 87 million flight hours, during which 
time, there have been no reports of uncommanded elevator movement on 
the ``classic'' model airplanes. These commenters point out that they 
submitted an identical request to the FAA during the comment period for 
the original NPRM, but, again, the FAA denied the request. As part of 
the reason for its denial, the FAA indicated that only a small 
percentage of airplanes are equipped with a flight data recorder that 
records the position of the elevator; therefore, if an operator elects 
to record only the control column position and an uncommanded elevator 
motion occurred, the incident may not be recorded, due to the flight 
crew's inability to confirm the anomaly. However, several of the 
commenters point out the flight crew can quickly ascertain the cause of 
a sudden pitching moment, since the elevator position is indicated on 
the flight deck for the flightcrew to see. Another commenter states 
that, even if operators have elected not to record the control surface 
position, it still does not negate the fact that there have been over 
87 million flight hours of safe flight of the Model 747 fleet on which 
the proposed modification has not been installed. Therefore, the 
commenters request that, when determining whether the current servo 
configuration is safe, the FAA should also consider this long history 
of absence of reports of uncommanded elevator motion.
    2. Potential structural damage concerns on Model 747-100, -100B 
SUD, -200, -300, SR, and SP series airplanes up to and including C/L 
695. One commenter points out that it submitted a similar request, 
along with a justifying probability analysis, to the original NPRM. 
That analysis was conducted to demonstrate that the aft fuselage 
structural limit load cannot be exceeded for the ``classic'' model 
airplanes for any valve jam in any portion of the flight envelope. As a 
result of that analysis, the commenter states that the probability of 
exceeding the structural limit of the aft fuselage on these airplanes 
is less than 1 x 10<SUP>-9. The FAA did not concur with that request, 
and indicated that the analysis was based ``on a sampling that was much 
too small from which accurate statistical conclusions could be drawn 
that would be representative of the fleet.'' The commenter states that 
this FAA statement and others in the Discussion section of the preamble 
to the supplemental NPRM indicate that clarification is necessary. The 
commenter notes that the structural and systems configurations of 
``classic'' model airplanes are such that, the maximum capability of 
the hydraulic system cannot induce a valve pressure on that airplane 
that exceeds structural limit loading; this point does not rely on the 
statistical sampling presented for the net valve differential pressure. 
The commenter maintains that the key point of the analysis it submitted 
previously is that only Model 747-200 and -300 series airplanes having 
C/L 696 and subsequent require the retrofit for potential structural 
damage concerns.
    3. Hydraulic tube change eliminates the possibility of high 
pressure spike for Model 747-400 series airplanes. Several commenters 
request that Model 747-400 series airplanes be removed from the 
applicability of proposed paragraph (b) and not be subject to the servo 
modification requirement. One commenter states that a high pressure 
spike in hydraulic system 4 was identified as the source of the valve 
movement that caused the initial incident on which this AD action is 
based; the commenter maintains that the

[[Page 57293]]

hydraulic tubing modification required by proposed paragraph (a) of the 
AD will remove the possibility of such high pressure spikes. Therefore, 
the servo assembly modification would be unnecessary. Two commenters 
present test results and analyses defending this position.
    Certain commenters submitted a similar request, along with analysis 
of data, to the original NPRM, but note that the FAA denied it. As 
reason for its denial, the FAA concluded that the data submitted ``do 
not substantiate * * * that routing the hydraulic system 3 to the 
sensitive side of the servo valve would preclude uncommanded elevator 
deflection.'' One of the commenters believes that the FAA drew these 
conclusions based on hydraulic pressure data for only one Model 747-400 
airplane; the commenter contends that such data are too small for the 
FAA to draw accurate conclusions. In light of this, the commenters 
request that the proposed modification of the servo assembly be deleted 
until the FAA conducts further studies of hydraulic systems 3 and 4 
pressure fluctuations on affected airplanes.
    The FAA has reconsidered its previous position and partially 
concurs with the commenters' request. However, a clarification of 
certain points associated with the data that were submitted by these 
commenters in support of their initial request must first be addressed.
    As for Item 1, indicated above, the FAA has considered the absence 
of reports of uncommanded elevator motion, as brought up by these 
commenters. The FAA finds that an absence of reports may be due to the 
fact that a flight data recorder is not installed on all airplanes that 
records the elevator surface movement. However, the FAA agrees with the 
commenters that the recording of the elevator time history is not the 
sole determination in the reporting of an event. The FAA also agrees 
with the commenters that the occurrence of uncommanded elevator 
movement would most likely be quickly ascertained by the flight crew. 
However, the FAA still maintains that the ability to confirm the 
anomaly may not exist.
    As for Item 2, indicated above, the FAA has re-reviewed the 
probability analysis that Boeing submitted. Based on Boeing's 
clarification of the previously submitted data, the FAA has determined 
that the ``classic'' model airplanes should not be subject to the 
modification of the servo assembly. The FAA has determined that the 
``classic'' model airplanes have sufficient structural strength to 
sustain a potential valve jam in the elevator PCP. Based on the 
configuration and loading of the ``classic'' model airplanes, the limit 
load cannot be exceeded with this type of valve jam. While the 
possibility of degradation in the controllability of these airplanes 
still exists, it is extremely improbable.
    In addition, the FAA has determined that Model 747-200 and -300 
series airplanes having C/L 696 and subsequent, are subject to the 
requirements of paragraph (b) of the AD. The FAA bases this 
determination on the fact that the limit load capability of the Model 
747-200 and -300 series airplanes having C/L 696 and subsequent, 
commonly referred to as ``common tail classic'' model airplanes, is 
similar to that of the ``classic'' model airplanes, but have a similar 
control configuration as that of Model 747-400 series airplanes. Due to 
the changes made in the configuration of the ``common tail classic'' 
model airplanes, uncommanded elevator motion could cause structural 
loading on these airplanes, which could result in structural damage and 
reduced controllability of the airplane.
    As for Item 3, indicated above, Boeing has conducted further 
testing, since issuance of the supplemental NPRM. The FAA has reviewed 
the results of this testing. The FAA has determined that the data 
presented do not adequately support that the high pressure spike in the 
hydraulic system 4 is the only potential cause of a secondary slide 
jam; or a pressure fluctuation will not occur in the hydraulic system 
3, which could lead to a potential uncommanded valve movement.
    In addition, the FAA has re-reviewed the data submitted by the 
commenters and maintains that:
    <bullet> The analysis is based on a sampling size that is too small 
from which accurate statistical conclusions can be drawn that would be 
representative of the fleet.
    <bullet> The variability in the data and the tests for normality 
indicate that the data depart from the mean.
    <bullet> Due to the sampling size of the data, a strong argument 
supporting normality cannot be inferred.
    <bullet> The flow rate and differential pressures used by the 
commenters in the analysis were not substantiated to be the worst case 
scenario.
    <bullet> Uncommanded elevator motion may occur on all Model 747 
series airplanes if the servo valve secondary slide moves to the 
valve's internal stop, regardless of hydraulic system routing.
    Therefore, the FAA finds that accomplishment of the hydraulic 
tubing modification alone, as required by paragraph (a) of the AD, does 
not adequately eliminate the possibility of crossflow in the servo 
valve on Model 747-400 series airplanes. The FAA acknowledges the 
possibility that uncommanded valve motion may be reduced following the 
installation of the hydraulic tubing modification on Model 747-400 
series airplanes. However, the FAA finds that the data presented, as 
well as service history, do not adequately demonstrate that uncommanded 
motion is the only potential cause of a secondary slide jam, or that a 
pressure fluctuation will not occur in hydraulic system 3 and lead to 
uncommanded movement of the valves.
    In light of the all of factors discussed above and the review of 
all of the data submitted, the FAA has determined that the servo 
assembly modification is warranted only for:
    1. Model 747-200 and -300 series airplanes having C/L 696 and 
subsequent (the ``common tail classic'' model airplanes) and
    2. The Model 747-400 series airplanes.
    The applicability of the final rule and of paragraph (b) have been 
revised accordingly.
    In addition, the FAA has revised the cost impact information, 
below, to indicate that the number of airplanes affected by this final 
rule has been reduced.

Request To Require Only Certain Type of Testing

    One commenter requests that paragraph (b) of the proposed AD be 
revised to require that the servo valve be tested only for the 
crossflow neutralization improvement feature in accordance with Parker 
Service Bulletins 93600-27-173 and 327400-27-171. The commenter states 
that certain specific tests that are called out in the service 
bulletins, such as the PCU dielectric test and eight-hour duty cycle 
test, are unrelated to the subject of the crossflow neutralization 
improvement. The commenter considers that revising the proposal as 
requested will eliminate redundant and unnecessary testing when 
reworking the PCP. The commenter contends that accomplishment of many 
of the tests in accordance with the subject service bulletins will not 
appreciably affect the flightworthy status of the PCP, as related to 
the crossflow enhancement, but will appreciably increase the cost of 
performing maintenance on the PCP. The commenter also requests that FAA 
allow operators to test the main manifold and assembled PCP's in

[[Page 57294]]

accordance with existing approved procedures.
    The FAA does not concur with the commenter's requests. The FAA has 
reviewed and approved all of the procedures specified in the Parker 
service bulletins that are referenced in paragraph (b) of the AD as the 
appropriate source of service information. The FAA has determined that 
accomplishment of the modification, including the various follow-on 
testing, in accordance with these service bulletins will prevent 
blockage of the hydraulic balance passageway by the spring guide, which 
can contribute to the uncommanded motion of the PCP. The FAA points out 
that some of the tests identified in the subject service bulletins are 
optional.

Requests To Revise the Cost Impact Statement

    Several commenters question the FAA's cost estimate presented in 
the preamble to the supplemental NPRM. These commenters consider the 
cost estimate to be significantly understated. Some commenters point 
out that the cost of a serviceable elevator PCP will be far greater 
than the FAA's estimated cost of $5,910 per unit. One of these 
commenters states that a serviceable elevator PCP costs $23,633; 
another commenter states that the cost is closer to $45,500.
    Additionally, some of the commenters note that, since many of the 
affected inboard elevator PCP's are older units, they may need 
additional rework or overhaul if they do not pass their respective 
acceptance tests. However, the FAA's cost estimate did not take these 
costs into consideration. In addition, one of these commenters states 
that the FAA's estimates failed to address the cost to modify spare 
units.
    The FAA finds that clarification of the costs associated with the 
requirements of this AD is necessary. The FAA points out that the 
economic analysis of the AD is usually limited only to the cost of 
actions actually required by the rule. It does not consider the costs 
of ``on condition'' actions (e.g., ``repair if a unit fails the 
functional test''), since those actions would be required to be 
accomplished, regardless of AD direction, in order to correct an unsafe 
condition identified in an airplane, and to ensure operation of that 
airplane in an airworthy condition, as required by the Federal Aviation 
Regulations.
    The AD's cost estimate also does not consider the costs of ``spare 
parts,'' since part 39 (``Airworthiness Directives'') of the Federal 
Aviation Regulations (14 CFR part 39) does not permit AD's to address 
parts or components that are not installed on an airplane (``a 
product''). Therefore, the FAA cannot require via an AD that operators 
modify a ``spare part;'' an AD can only require that the part be 
modified before it is installed on an affected airplane.
    In addition, the FAA points out that many operators have their own 
shop facilities in which to disassemble the PCP and accomplish the PCP 
overhaul/modification; for these operators, the costs associated with 
those actions may be far less than estimated by the FAA.
    As for the exact cost of required parts, the FAA has verified with 
the manufacturer that the parts costs that was presented in the cost 
impact information in the preamble to the supplemental NPRM, and 
reiterated below, are valid.

FAA's Conclusions

    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 30 Model 747-200 and -300 series airplanes; 
and 332 Model 747-400 series airplanes; of the affected design in the 
worldwide fleet (362 airplanes total).
    There currently are no Boeing Model 747-200 and -300 series 
airplanes on the U.S. Register that are subject to the requirements of 
this AD. All of the affected airplanes of those models that are 
included in the applicability of this rule currently are operated by 
non-U.S. operators under foreign registry; therefore, they are not 
directly affected by this AD action. However, the FAA considers that 
inclusion of these airplanes in the rule is necessary to ensure that 
the unsafe condition is addressed in the event that any of these 
airplanes are imported and placed on the U.S. Register in the future.
    Should any affected Model 747-200 and -300 series airplanes be 
imported and placed on the U.S. Register in the future, it would take 
approximately 73 work hours per airplane to accomplish the required 
modification, at an average labor rate of $60 per work hour. Required 
parts will cost approximately $7,440 per airplane. Based on these 
figures, the cost impact of the modification required by this AD on 
U.S. operators is estimated to be $11,820 per airplane.
    The FAA estimates that 65 Model 747-400 series airplanes of U.S. 
registry will be affected by this AD, that it will take approximately 
111 work hours per airplane to accomplish the required actions, and 
that the average labor rate is $60 per work hour. Required parts will 
cost approximately $12,269 per airplane. Based on these figures, the 
cost impact of the AD on U.S. operators of Model 747-400 series 
airplanes is estimated to be $1,230,385, or $18,929 per airplane.
    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 
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:


[[Page 57295]]


    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:

96-22-01  Boeing: Amendment 39-9790. Docket 94-NM-226-AD.

    Applicability: Model 747-200, -300, and -400 series airplanes 
having cumulative line number (C/L) 696 through 1057, inclusive; 
equipped with Parker inboard elevator power control packages (PCP) 
having part numbers (P/N) 93600-5005 through -5051 inclusive, or P/
N's 327400-1001, -1003, -1005, and -1007; 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 uncommanded elevator deflection, which could result 
in structural damage and reduced controllability of the airplane, 
accomplish the following:
    (a) For Model 747-400 series airplanes, as listed in Boeing 
Alert Service Bulletin 747-27A2348, Revision 1, dated January 26, 
1995: Within 1 year after the effective date of this AD, modify the 
hydraulic tubing of the right inboard elevator PCP, in accordance 
with Boeing Alert Service Bulletin 747-27A2348, Revision 1, dated 
January 26, 1995.
    (b) For all airplanes: Within 3 years after the effective date 
of this AD, modify the left and right servo assemblies of the 
inboard elevator PCP, in accordance with Parker Service Bulletin 
327400-27-171, Revision 1, dated April 14, 1995, or Parker Service 
Bulletin 93600-27-173, dated May 17, 1995, as applicable.
    (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.
    (e) The modifications shall be done in accordance with Boeing 
Alert Service Bulletin 747-27A2348, Revision 1, dated January 26, 
1995; Parker Service Bulletin 327400-27-171, Revision 1, dated April 
14, 1995; and Parker Service Bulletin 93600-27-173, dated May 17, 
1995; as applicable. 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; and Parker Hannifin Corporation, Customer Support Operations, 
16666 Von Karman Avenue, Irvine, California 92714. 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 December 6, 1996.

    Issued in Renton, Washington, on October 15, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-26952 Filed 11-5-96; 8:45 am]
BILLING CODE 4910-13-U