[Federal Register Volume 70, Number 6 (Monday, January 10, 2005)]
[Rules and Regulations]
[Pages 1655-1659]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 05-281]


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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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