[Federal Register Volume 63, Number 63 (Thursday, April 2, 1998)]
[Rules and Regulations]
[Pages 16091-16094]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-8352]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 95-NM-207-AD; Amendment 39-10436; AD 98-07-16]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 737-300, -400, and -500
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 737-300, -400, and -500 series
airplanes, that requires interchanging the location of the hydraulic
fuse and the flow limiter of the standby hydraulic system of the
leading edge. This amendment also requires replacing the existing
hydraulic fuses in the standby hydraulic system with new fuses. This
amendment is prompted by reports of a performance test of the hydraulic
fuses, which revealed that the positioning of the flow limiter in the
existing configuration, and excessive fusing volumes of some of the
fuses in extreme cold environment, can adversely affect the operation
of the fuse. The actions specified by this AD are intended to
[[Page 16092]]
prevent such adversely affected operation of the fuse, which could
result in the loss of all standby hydraulic system pressure and
consequent severely reduced controllability of the airplane during
certain flight phases.
DATES: Effective May 7, 1998.
The incorporation by reference of certain publications, as listed
in the regulations, is approved by the Director of the Federal Register
as of May 7, 1998.
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 98055-
4056; 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) to include an airworthiness
directive (AD) that is applicable to certain Boeing Model 737-300, -
400, and -500 series airplanes was published in the Federal Register on
January 7, 1997 (62 FR 947). That action proposed to require
interchanging the location of the hydraulic fuse and the flow limiter
of the standby hydraulic system of the leading edge so that the
hydraulic fuse is positioned upstream of the flow limiter. That action
also proposed to require replacing the existing hydraulic fuses in the
standby hydraulic system with new fuses that are not affected by low
temperature operation.
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.
Requests to Revise the Compliance Times of the Proposed Interchange
and Replacement Actions
The Air Transport Association (ATA) of America states that one
commenter generally supports the proposed action; however, this
commenter requests an amended compliance time of 18 months in lieu of
4,000 flight hours specified in paragraph (b) of the proposed AD. The
commenter states that such an extension is needed because of an
expected large demand for these fuses. A second commenter requests
changing the compliance time to 6,000 flight hours or 2 years,
whichever occurs first, because the hydraulic fuse manufacturer is
unable to support a compliance time of 4,000 flight hours. Another
commenter also requests a change in the compliance time to 6,000 flight
hours.
The FAA concurs partially with these requests and acknowledges that
parts availability and scheduling may present problems. The FAA does
not concur with the request to extend the compliance time from 4,000
flight hours to 6,000 flight hours, or the request to change it to
6,000 flight hours or 2 years, whichever occurs first. However, the FAA
has considered the need to allow additional time to obtain the number
of fuses required for the fleet and to avoid scheduling problems for
the replacement of discrepant fuses. Therefore, the FAA has revised
paragraph (b) of the final rule to read: ``Within 18 months or 4,000
flight hours after the effective date of this AD, whichever occurs
later. . . .'' In addition, for the same reasons, the FAA has revised
the compliance time of paragraph (a) of the final rule, which is
identical to paragraph (b). The FAA has determined that extending these
compliance times will not adversely affect safety.
Requests to Clarify the Summary Section of the Preamble
Two commenters request a number of revisions and additions to
clarify the technical content of the ``Summary'' Section of the NPRM.
In that section, one commenter requests that the third sentence be
changed from ``* * * and excessive fusing volumes of some of the fuses,
can adversely affect * * * '' to ``* * * and excessive fusing volumes
of some of the fuses in extreme cold environment, can adversely affect
* * *.'' The FAA concurs with this request and has changed the final
rule accordingly.
Two commenters request that the statement of unsafe condition be
changed from ``* * * in the loss of all hydraulic system pressure and
consequent severely reduced controllability of the airplane'' to ``* *
* in the loss of all standby hydraulic system pressure and may reduce
the controllability of the airplane during certain flight phases.'' The
FAA concurs partially with these changes. The FAA has determined that
the word ``standby'' and the phrase ``during certain flight phases''
add clarity and has revised the final rule accordingly. However, the
FAA does not concur with the proposed addition of ``may reduce the
controllability'' to the sentence, because the FAA considers that
``could result in'' is more accurate.
Requests to Clarify Additional Sections of the Preamble
1. ``Discussion'' Section. In the first paragraph of this section,
one commenter requests that the second sentence be changed from
``Results of that performance test * * *'' to ``In the existing
configuration, the standby leading edge flow limiter is upstream of the
standby leading edge fuse. The results of the performance test revealed
that this configuration of the flow limiter and fuse assembly adversely
affects the operation of the fuse.''
In the second paragraph of this section, one commenter requests
deleting the second sentence and changing the third sentence from ``* *
* are not affected by this condition * * *'' to ``* * * are not
affected by this condition because steady state temperatures keep the
fluid warm.''
In the third paragraph of this section, two commenters request
changing the second sentence from ``The hydraulic fuse is designed to
prevent total loss of the hydraulics systems after a certain volume of
fluid passes through the fuse within a specified time following the
development of a leak downstream of the fuse * * *'' to ``Hydraulic
fuses are designed to prevent total loss of the hydraulics system after
a certain volume of fluid (continually/continuously) passes through the
fuse following the development of a leak downstream of the fuse.''
2. Explanation of Relevant Service Information. In the second
paragraph of this section, two commenters request changing the first
sentence from ``* * * new fuses that are not affected by low
temperature operation'' to ``* * * new fuses that function in low
temperatures.'' These commenters also request changing the second
sentence from ``* * * as a result of fluid depletion if a leak occurs
downstream of the fuses'' to ``* * * as a result of a fuse failing to
set following a leak downstream of the fuses.''
3. Explanation of Requirements of Proposed Rule. In the first
paragraph of this section, two commenters request changing the second
sentence from ``* * * new fuses that are not affected by low
temperature operation'' to ``* * * new fuses that function at/in low
temperatures.''
[[Page 16093]]
Although the FAA acknowledges that the commenters' suggested
wording in these sections of the preamble adds technical clarity, the
FAA has determined that these changes are not relevant because these
sections do not appear in the final rule.
Requests to Clarify the Body of the AD
One commenter requests changing paragraph (b) to read: ``For
airplanes listed in Boeing Service Bulletin 737-29-1071 (line numbers
2001 through 2791). * * *'' The FAA does not concur with this request
for two reasons. First, the line number ``2001'' is incorrect, and the
correct number (1001) is shown in the applicability of the proposed AD.
Second, because the line numbers are included in the applicability of
the AD, it is unnecessary to include them elsewhere in the AD.
Two commenters request changing paragraph (b) to read ``* * * with
new fuses that are not adversely affected during low temperature
operation. * * *'' The FAA has determined that this change adds clarity
and has changed the wording of the final rule accordingly.
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 1,791 Boeing Model 737-300, -400, and -500
series airplanes of the affected design in the worldwide fleet. The FAA
estimates that 596 airplanes of U.S. registry will be affected by this
AD.
The FAA estimates that it will take approximately 2 work hours per
airplane to accomplish the required interchange of the hydraulic fuse
and the flow limiter, and that the average labor rate is $60 per work
hour. The cost for required parts will be minimal. Based on these
figures, the cost impact of the required interchange on U.S. operators
is estimated to be $71,520, or $120 per airplane.
The FAA also estimates that it will take approximately 4 work hours
per airplane to accomplish the required replacement, at an average
labor rate of $60 per work hour. Required parts will be provided by the
manufacturer at no cost to operators. Based on these figures, the cost
impact of the required replacement on U.S. operators is estimated to be
$143,040, or $240 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:
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:
98-07-16 Boeing: Amendment 39-10436. Docket 95-NM-207-AD.
Applicability: Model 737-300, -400, and -500 series airplanes
having line numbers 1001 through 2791 inclusive; 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.
Compliance: Required as indicated, unless accomplished
previously.
To prevent adversely affected operation of the fuse, which could
result in the loss of all standby hydraulic system pressure and
consequent severely reduced controllability of the airplane during
certain flight phases, accomplish the following:
(a) For airplanes listed in Boeing Service Bulletin 737-29-1070,
dated June 8, 1995: Within 18 months or 4,000 flight hours after the
effective date of this AD, whichever occurs later, interchange the
location of the hydraulic fuse and the flow limiter of the standby
hydraulic system of the leading edge so that the hydraulic fuse is
positioned upstream of the flow limiter, in accordance with Boeing
Service Bulletin 737-29-1070, dated June 8, 1995.
(b) For airplanes listed in Boeing Service Bulletin 737-29-1071,
dated May 16, 1996: Within 18 months or 4,000 flight hours after the
effective date of this AD, whichever occurs later, replace the
existing hydraulic fuses in the standby hydraulic system with new
fuses that are not adversely affected during low temperature
operation, in accordance with Boeing Service Bulletin 737-29-1071,
dated May 16, 1996.
(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 actions shall be done in accordance with Boeing Service
Bulletin 737-29-1070, dated June 8, 1995, and Boeing Service
Bulletin 737-29-1071, dated May 16, 1996. This incorporation by
reference was approved by the Director of the Federal Register in
accordance with 5 U.S.C. 552(a)
[[Page 16094]]
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 May 7, 1998.
Issued in Renton, Washington, on March 25, 1998.
Darrell M. Pederson,
Acting Manager,
Transport Airplane Directorate,
Aircraft Certification Service.
[FR Doc. 98-8352 Filed 4-1-98; 8:45 am]
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