[Federal Register: January 10, 2005 (Volume 70, Number 6)]
[Rules and Regulations]
[Page 1655-1659]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr10ja05-2]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 2003-NM-166-AD; Amendment 39-13936; AD 2005-01-12]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 757-200, -200PF, and -
200CB 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 757-200, -200PF, and -200CB series
airplanes, that requires an inspection of certain ballscrews of the
trailing edge flap system to find their part numbers, and replacement
of the ballscrews with new, serviceable, or modified ballscrews if
necessary. This action is necessary to prevent a flap skew due to
insufficient secondary load path of the ballscrew of the trailing edge
flaps in the event that the primary load path fails, which could result
in possible loss of a flap and reduced controllability of the airplane.
This action is intended to address the identified unsafe condition.
DATES: Effective February 14, 2005. The incorporation by reference of a
certain publication listed in the regulations is approved by the
Director of the Federal Register as of February 14, 2005.
ADDRESSES: The service information referenced in this AD may be
obtained from Boeing Commercial Airplanes, 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 National
Archives and Records Administration (NARA). For information on the
availability of this material at NARA, call (202) 741-6030, or go to:
http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html
.
FOR FURTHER INFORMATION CONTACT: Douglas Tsuji, Aerospace Engineer,
Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft
Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-
4056; telephone (425) 917-6487; fax (425) 917-6590.
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 757-200, -
200PF, and -200CB series airplanes was published in the Federal
Register on April 1, 2004 (69 FR 17105). That action proposed to
require an inspection of certain ballscrews of the trailing edge flap
system to find their part numbers, and replacement of the ballscrews
with new, serviceable, or modified ballscrews if necessary.
[[Page 1656]]
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.
Request To Delay Issuance of Final Rule
One commenter requests that the FAA delay the issuance of the final
rule until Boeing issues a service bulletin for relocating the rear
spar air dam of the trailing edge (TE) from wing station (WS) 399 to WS
357, if we are planning to mandate the modification in another
rulemaking action. The commenter states that this modification would
move the air dam and the associated hydraulic, flight controls, and
electrical systems inboard along the wing TE, which would mitigate
collateral system damage in the event of a powered flap skew. The
commenter also states that the Boeing service bulletin for this
modification is expected to be released in the third quarter of 2004.
We do not agree with the request. We have determined that the
modification described by the commenter addresses the result of a
powered flap skew (i.e., potential collateral damage). The requirements
of this AD address the potential cause of a flap skew (i.e.,
insufficient secondary load path of the ballscrew of the TE flaps in
the event that the primary load path fails). It is this skew, which
could adversely affect the controllability of the airplane, that needs
to be corrected. In addition, the airplane manufacturer has not issued
and we have not reviewed and approved the subject service bulletin. We
do not consider it appropriate to delay the issuance of this final rule
in light of the identified unsafe condition. When the service bulletin
is issued, we will review it and may consider future rulemaking action.
Therefore, no change to the final rule is necessary in this regard.
Requests To Revise Compliance Times
One commenter requests that, for operators having an overhaul
requirement for a TE flap ballscrew in their maintenance schedule, the
36-month compliance time in the notice of proposed rulemaking (NPRM)
for replacing any ballscrew having part number (P/N) S251N401-5
(Thomson Saginaw P/N 7820921) or S251N401-9 (Thomson Saginaw P/N
7821341) be revised to allow operators to either:
Continue operation until the next unscheduled removal or
scheduled overhaul, whichever occurs first; or
Do the replacement at a later time, allowing them to
continue operation until, for example, the next 4C-check.
The commenter states that its approved maintenance schedule
requires overhaul of the TE flap ballscrews at 18,200 flight hours.
In line with the previous request, the same commenter also requests
that we take into account recent installation of new or overhauled
units. The commenter states that airplanes having ballscrews that have
been installed recently (in a new or overhauled condition) will require
replacement again soon. Also, these airplanes are subject to the same
compliance time as airplanes having ballscrews that have been installed
for many years.
In addition, three commenters request that the compliance time for
the proposed inspection/replacement be extended for different reasons.
Two commenters suggest that a compliance time of 48 months would
coincide with the existing 24-month (or 6,000-flight hour/3,000 flight
cycles, whichever occurs first) heavy maintenance schedule for Model
757 airplanes operated in a freighter configuration. One of the two
commenters states that the 36-month compliance time would impose
unnecessary economic and operational burdens by requiring airplanes to
be routed as a ``special visit'' to a heavy maintenance facility to
comply with the NPRM. This commenter also notes that recorded findings
of a time-controlled functional check at 18,000 flight hours are well
within the manufacturer's required limits, and that no removal of the
ballscrews have occurred due to wear. Instead of a 48-month compliance
time, one of the two commenters also suggest either:
The later of: 36 months or (12,000 flight hours or 6,000
flight cycles, whichever occurs first); or
48 months or 12,000 flight hours or 6,000 flight cycles,
whichever occurs first.
The third commenter states that the proposed compliance time will
require as many as three full-ship sets of modified ballscrew
assemblies each month. The increased demand by all operators for
modified assemblies will make the ballscrew assembly modification turn-
around time a critical factor for compliance. This commenter also notes
that industry has not reported any occurrence of a flap skew condition
as a result of a failed ballscrew assembly. For these reasons, the
commenter suggests that the compliance time should be extended from 36
months to 48 months.
We partially agree with the requests. We do not agree that it is
necessary to revise the compliance time for the required replacement to
account for recent installation of new or overhauled units. The
requirements of this AD address a design deficiency (i.e., insufficient
secondary load path of the ballscrew of the TE flaps in the event that
the primary load path fails). This deficiency is not dependant upon
wear or usage of the ballscrew as suggested by a commenter. Therefore,
how recently a ballscrew has been replaced is irrelevant to correcting
the subject design deficiency, unless the ballscrew has the improved
secondary load path.
We agree that the compliance times for both the inspection and
replacement, if necessary, can be extended somewhat to coincide with
regularly scheduled maintenance visits. We intended to require those
actions at intervals that would coincide with regularly scheduled
maintenance visits for the majority of the affected fleet, when the
airplanes would be located at a base where special equipment and
trained personnel would be readily available, if necessary. However,
accomplishing the required actions at the next 4C-check may, for some
operators, significantly increase time and affect the probability of a
ballscrew failure. Therefore, we have determined that extending the
compliance times from the proposed 36 months to 48 months will provide
an acceptable level of safety. Paragraph (a) of the final rule has been
revised accordingly.
Requests To Revise Service Bulletins
One commenter requests that the wording of Boeing Alert Service
Bulletin 757-27A0139, dated June 16, 2003 (cited in the NPRM as the
appropriate source of service information for accomplishing the
proposed inspection and replacement if necessary) be consistent with
the NPRM. The commenter states that in several locations of the
Accomplishment Instructions of the service bulletin, including Figure
1, it states to examine the ballscrews for its P/N, and if the P/N is
either S251N401-5 or -9 (i.e., a pre-modified ballscrew), the ballscrew
must be replaced. The commenter notes that the NPRM requires inspection
and replacement, if necessary, within 36 months after the effective
date of the AD. The service bulletin recommends the replacement with no
allowance for time after the pre-modified unit has been found. The
commenter contends that the service bulletin is very restrictive and
difficult to adhere to. The commenter sent its request to Boeing too.
[[Page 1657]]
Boeing responded to the commenter by stating, ``The compliance
statement in the bulletin advises, `Boeing recommends that operators do
the inspection and possible replacement given in this service bulletin
in three years or less from the date on this service bulletin.' The
intent means that as long as both conditions (inspection AND
replacement) are satisfied with the three year window, operators are
compliant.''
Because paragraph 1.E., ``Compliance'' of Boeing Alert Service
Bulletin 757-27A0139 recommends a compliance time of 36 months for
accomplishing both the inspection and replacement, if necessary, we
infer that the commenter is requesting that we ask Boeing to
specifically revise the ``Accomplishment Instructions'' of that service
bulletin to include compliance times. We do not agree. Although the
recommended compliance times are not cited in the Accomplishment
Instructions of the referenced service bulletin, they are clearly cited
in paragraph 1.E, ``Compliance,'' as noted in Boeing's response
discussed earlier. The wording of paragraph (a) of this AD is also
clear that both the required inspection and the replacement, if
necessary, must be done within 36 months after the effective date of
this AD. When there are differences between an AD and the referenced
service bulletin, the AD prevails. Therefore, we do not find it
necessary to require Boeing to include compliance times in the
Accomplishment Instructions of the referenced service bulletin.
One commenter requests that Thomson Saginaw Ball Screw Component
Maintenance Manual (CMM) 27-51-20, dated November 15, 1998, be revised
before issuance of the final rule to reflect the full intent of the
part modification driven by Thomson Saginaw Service Bulletin 7900897,
Revision C, included by reference in Boeing Alert Service Bulletin 757-
27A0139. The commenter notes that, while the NPRM does not provide
direct reference to Thomson Saginaw Service Bulletin 7900897, nor the
CMM 27-51-20, it would require certain ballscrew assemblies to be
replaced with new, serviceable, or modified ballscrews in accordance
with Boeing Alert Service Bulletin 757-27A0139. The commenter further
notes that Boeing Alert Service Bulletin 757-27A0139 recommends that
the identified ballscrews be changed in accordance with the Thomson
Saginaw service bulletin, which is written for accomplishment in
conjunction with CMM 27-51-20.
The commenter states that, after initial modification, future
component maintenance in accordance with CMM 27-51-20 could result in
an old ball nut installation, thereby de-modifying the unit from the
intent of the Thomson Saginaw service bulletin. The commenter believes
that this de-modification could raise a question of compliance with the
intent of the NPRM if the CMM is not revised to reflect the intent of
the service bulletin changes.
We partially agree with the commenter's request. We agree that it
is possible to install an un-modified ball nut having P/N 7820679 into
a previously modified ballscrew, because CMM 27-51-20 does not
distinguish between a modified and unmodified ball nut. However, we
disagree with the commenter that it is necessary to delay issuance of
this final rule until CMM 27-51-20 is revised, or that a revision to
the CMM is necessary. All ball nuts have a nameplate that has the P/N
of the ballscrew on it. The nameplate of older, unmodified ball nuts
has either P/N S251N401-5 or -9 on it. As of the effective date of this
AD, paragraph (b) of the AD prohibits installation of any ballscrew
having P/N S251N401-5 or -9, on any airplane. We have determined that
the requirements of this AD adequately address the identified unsafe
condition. No change to the final rule is necessary in this regard.
Request To Deviate From Service Bulletin
One commenter requests that paragraph (a) of the NPRM be revised to
deviate from the referenced service bulletin (i.e., Boeing Alert
Service Bulletin 757-27A0139) by allowing the proposed inspection
without removal of the aft fairing from the flap track as is currently
specified in the service bulletin. The commenter notes that the service
bulletin recommends accomplishing the removal in accordance with Boeing
767 Airplane Maintenance Manual (AMM) 27-51-31/201. The commenter
states that the P/N on the subject ballscrews is located on a data
plate that is fastened to the ball nut in a predetermined location as
part of the component assembly. This location for the part
identification is readily visible with the ballscrew assembly installed
on the airplane without removal of the aft flap fairing. The commenter
believes its suggestion would prevent unnecessary access and subsequent
reinstallation and testing in the event the parts are not those that
require replacement according to the AD.
We agree with the commenter that paragraph (a) should be clarified.
Our intent was that the required inspection determine the P/Ns of the
ballscrews, not the manner in which the P/Ns are identified. Therefore,
the inspection required by paragraph (a) of this final rule does not
have to be done in accordance Boeing Alert Service Bulletin 757-
27A0139. We have revised paragraph (a) of the final rule accordingly.
Request To Clarify Terminating Action
To prevent any confusion about the terminating action, one
commenter requests that paragraph (a) of the NPRM be clarified to
indicate that accomplishing the actions specified in Boeing Alert
Service Bulletin 757-27A0139 terminates the NPRM.
We do not agree. The replacement in paragraph (a) of this AD is
only required if the P/N of the ballscrew is S251N401-5 (Thomson
Saginaw P/N 7820921) or S251N401-9 (Thomson Saginaw P/N 7821341).
Because some operators may not have to do the replacement, we find that
referring to the replacement as terminating action for this AD is
inappropriate. No change to the final rule is necessary in this regard.
Requests To Revise Cost Impact
One commenter requests that we consider reviewing the estimate in
the Cost Impact section of the NPRM for accomplishing the proposed
modification. The commenter states that the cost estimate does not
account for the additional cost associated with the removal of the ball
nut from the ballscrew or with new bearings, scraper/seals,
inspections, assembly, and testing of the ballscrew. Another commenter
states that the time estimated in the Cost Impact section of the NPRM
for modifying the subject ballscrew assemblies is underestimated. The
commenter believes it will take 8 work hours to modify one unit.
We do not agree that Cost Impact section of the NPRM needs to be
revised. The Cost Impact section below describes only the direct costs
of the specific actions required by this AD. Based on the best data
available, the airplane manufacturer's and ballscrew manufacturer's
service information specified the number of work hours (6 hours per
ballscrew) necessary to do the removal, modification, and
reinstallation of a ballscrew, if required. This number represents the
time necessary to perform only the actions actually required by this
AD. We recognize that, in doing the actions required by an AD,
operators may incur incidental costs in addition to the direct costs.
The cost analysis in AD rulemaking actions, however, typically does not
include incidental costs such as the time required to gain access and
[[Page 1658]]
close up, time necessary for planning, or time necessitated by other
administrative actions. Those incidental costs, which may vary
significantly among operators, are almost impossible to calculate. No
change to the final rule is necessary in this regard.
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 979 airplanes of the affected design in the
worldwide fleet. The FAA estimates that 644 airplanes of U.S. registry
will be affected by this AD.
It will take approximately 1 work hour per airplane to accomplish
the required inspection at an average labor rate of $65 per work hour.
Based on these figures, the cost impact of the AD on U.S. operators is
estimated to be $41,860, or $65 per airplane.
Replacement of a ballscrew with a new or serviceable ballscrew, if
required, will take about 3 work hours per ballscrew, at an average
labor rate of $65 per work hour. Required parts will cost about $8,400
per ballscrew. Based on these figures, we estimate the cost of a repair
to be $8,595 per ballscrew (there are two ballscrews per airplane).
Removal, modification, and reinstallation of a ballscrew, if
required, will take about 6 work hours per ballscrew, at an average
labor rate of $65 per work hour. Required parts will cost about $553
per ballscrew. Based on these figures, we estimate the cost of a repair
to be $943 per ballscrew (there are two ballscrews 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. The cost impact figures discussed
in AD rulemaking actions represent only the time necessary to perform
the specific actions actually required by the AD. These figures
typically do not include incidental costs, such as the time required to
gain access and close up, planning time, or time necessitated by other
administrative actions.
Authority for This Rulemaking
The FAA's authority to issue rules regarding aviation safety is
found in title 49 of the United States Code. Subtitle I, section 106
describes the authority of the FAA Administrator. Subtitle VII,
Aviation Programs, describes in more detail the scope of the agency's
authority.
This rulemaking is promulgated under the authority described in
subtitle VII, part A, subpart III, section 44701, ``General
requirements.'' Under that section, the FAA is charged with promoting
safe flight of civil aircraft in air commerce by prescribing
regulations for practices, methods, and procedures the Administrator
finds necessary for safety in air commerce. This regulation is within
the scope of that authority because it addresses an unsafe condition
that is likely to exist or develop on products identified in this AD.
Regulatory Impact
The regulations adopted herein will not have a substantial direct
effect 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, it
is determined that this final rule does not have federalism
implications under Executive Order 13132.
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
0
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
0
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]
0
2. Section 39.13 is amended by adding the following new airworthiness
directive:
2005-01-12 Boeing: Amendment 39-13936. Docket 2003-NM-166-AD
.Applicability: Model 757-200, -200PF, and -200CB series
airplanes, line numbers 1 through 979 inclusive; certificated in any
category.
Compliance: Required as indicated, unless accomplished
previously.
To prevent a flap skew due to insufficient secondary load path
of the ballscrew of the trailing edge flaps in the event that the
primary load path fails, which could result in possible loss of a
flap and reduced controllability of the airplane, accomplish the
following:
Inspection and Corrective Action
(a) Within 48 months after the effective date of this AD, do an
inspection of the ballscrews of the trailing edge flap system to
find their part numbers (P/N). If the P/N of the ballscrew is
S251N401-5 (Thomson Saginaw P/N 7820921) or S251N401-9 (Thomson
Saginaw P/N 7821341), within 48 months after the effective date of
this AD, replace the ballscrew with a new, serviceable, or modified
ballscrew, in accordance with the Accomplishment Instructions of
Boeing Alert Service Bulletin 757-27A0139, dated June 16, 2003.
Parts Installation
(b) As of the effective date of this AD, no person may install a
trailing edge flap ballscrew, P/N S251N401-5 (Thomson Saginaw P/N
7820921) or S251N401-9 (Thomson Saginaw P/N 7821341), on any
airplane.
Alternative Methods of Compliance
(c) In accordance with 14 CFR 39.19, the Manager, Seattle
Aircraft Certification Office, FAA, is authorized to approve
alternative methods of compliance for this AD.
Incorporation by Reference
(d) Unless otherwise specified in this AD, the actions shall be
done in accordance with Boeing Alert Service Bulletin 757-27A0139,
dated June 16, 2003. 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 Airplanes, 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 National
Archives and Records Administration (NARA). For information on the
availability of this material at NARA, call (202) 741-6030, or go
to: http://www.archives.gov/federal_register/
[[Page 1659]]
code--of--federal--regulations/ibr--locations.html.
Effective Date
(e) This amendment becomes effective on February 14, 2005.
Issued in Renton, Washington, on December 29, 2004.
Kevin M. Mullin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 05-281 Filed 1-7-05; 8:45 am]
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