AD 2000-04-18

[Federal Register Volume 65, Number 40 (Tuesday, February 29, 2000)]
[Rules and Regulations]
[Pages 10693-10695]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 00-4567]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-354-AD; Amendment 39-11601; AD 2000-04-18]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 757 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 series airplanes, that requires 
replacement of transmission assemblies for the trailing edge flaps with 
modified transmission assemblies. This amendment is prompted by reports 
of broken bolts that attach the transmission assemblies for the 
trailing edge flaps. The actions specified by this AD are intended to 
prevent damage to the flap system, adjacent system, or structural 
components; and excessive skew of the trailing edge flap; which could 
result in reduced controllability of the airplane.

DATES: Effective April 4, 2000.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of April 4, 2000.

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: Robert C. Jones, 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 (425) 227-1118; 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 757 series 
airplanes was published in the Federal Register on October 19, 1999 (64 
FR 56279). That action proposed to require replacement of transmission 
assemblies for the trailing edge flaps with modified transmission 
assemblies.

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.

Support for the Proposal

    One commenter supports the proposed rule.

Request To Allow Use of Other Service Information

    One commenter requests that paragraph (b) of the proposed rule be 
revised to allow installation of a transmission assembly modified in 
accordance with the original issue of Boeing Alert Service Bulletin 
757-27A0127, dated September 10, 1998. The commenter states that this 
would be consistent with ``NOTE 2'' of the proposed rule, which states, 
``Replacements accomplished in accordance with Boeing Alert Service 
Bulletin 757-27A0127, * * * are considered acceptable for compliance 
with paragraph (a) of this AD.''
    The FAA concurs with the commenter's request, and has revised 
paragraph (b) to read, `` * * * no person shall install on any 
airplane, a trailing edge flap transmission assembly, unless it has 
been modified in accordance with this AD.''

Request To Allow Installation of a New Transmission

    One commenter requests that paragraph (b) of the notice of proposed 
rulemaking (NPRM) be revised to allow installation of a new 
transmission that incorporates the upgraded torque limiter. The 
commenter states that some operators may choose to purchase a new 
transmission from the supplier, instead of modifying the existing unit.
    The FAA concurs with the commenter's request. The FAA's intent was 
to allow installation of a new flap transmission assembly equipped with 
the new torque limiter or a modified flap transmission assembly. 
Therefore, in accordance with the commenter's request, paragraph (b) of 
this final rule has been revised to specify that no person shall 
install a trailing edge flap assembly, unless it has been modified in 
accordance with this AD, or, in the case of new transmission 
assemblies, it incorporates the new torque limiter. In addition, 
paragraph (a) of this final rule has been revised to clarify that 
replacement of existing transmission assemblies with new transmission 
assemblies that incorporate new torque limiters is acceptable for 
compliance with this AD.

Request To Clarify Preamble of Proposed Rule

    One commenter requests that one sentence in the ``Explanation of 
Relevant Service Information'' section in the preamble of the proposed 
rule be revised. The proposed rule states that, ``The modified 
transmission assemblies include new torque limiters that can prevent 
damage to the airplane from high system loads at the transmission 
assemblies, and can prevent excessive skew of the trailing edge flap.'' 
The commenter requests that the last clause of the sentence be revised 
to read, ``* * * and can, in some conditions, prevent excessive skew of 
the trailing edge flap.'' The commenter states that, while a properly 
functioning torque

[[Page 10694]]

limiter is expected to prevent excessive skew of the flap under some 
skew conditions, it is not certain that a properly functioning torque 
limiter will lock out under all circumstances to prevent a skewing flap 
from being damaged by drive system loads.
    The FAA concurs with the intent of the commenter's request. While 
the new torque limiters represent a significant improvement over the 
existing torque limiters and are effective in preventing damage due to 
a jam, the FAA recognizes that the new torque limiters may not prevent 
excessive skew in all flight conditions. Also, because the new torque 
limiters may not prevent loss of controllability in all flight 
conditions, the FAA may consider further regulatory action in the 
future. However, despite the FAA's concurrence, no change to the final 
rule is necessary in this regard because the subject section is not 
restated in the final rule.

Request To Revise Cost Estimate

    One commenter requests that the FAA revise the cost estimate of the 
proposed AD from $43,512,000 ($87,024 per airplane), to $44,172,000 
($88,344 per airplane). The commenter states that the suggested change 
is consistent with the estimates in the service bulletin.
    The FAA does not concur with the commenter's request to revise the 
cost estimate. The estimate of 32 work hours specified in the NPRM 
represents the time necessary to perform only the actions actually 
required by this AD (i.e., replacement of transmission assemblies for 
the trailing edge flaps with modified transmission assemblies). The FAA 
recognizes that, in accomplishing the requirements of any 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 
close up; planning time; or time necessitated by other administrative 
actions. Because incidental costs may vary significantly from operator 
to operator, they are almost impossible to calculate. Thus, the FAA 
finds that the number of work hours estimated in the NPRM is consistent 
with the estimated number of work hours for accomplishing Part 1 of the 
service bulletin (excluding the work hours for ``incidental'' actions), 
and no change to the final rule is necessary in this regard.

Request To Extend Compliance Time

    One commenter requests that the compliance time for the actions 
specified in paragraph (a) of the proposed rule be extended from 36 
months to 48 months, to allow the proposed actions to be accomplished 
on all affected airplanes at a ``4C'' check. (The commenter considers 
the ``4C'' check interval to be 72 months.) Alternatively, the 
commenter suggests that the compliance time be revised to ``at the 
airplane's first scheduled `4C' check'', for airplanes that have not 
undergone a scheduled ``4C'' check since delivery, or within 36 months 
after the effective date of this AD, for airplanes that have undergone 
a scheduled ``4C'' check since delivery. The commenter states that most 
airplanes affected by this AD will have completed at least one ``4C'' 
check cycle by the end of the proposed 36-month compliance time. Thus, 
most operators would be able to accomplish the proposed AD on their 
airplanes during a ``4C'' check, which would allow accomplishment of 
this AD with only minimal schedule disruption. However, the commenter 
states that there are a few airplanes that will not complete a ``4C'' 
check cycle by the end of the proposed 36-month compliance time. 
According to the commenter, a 36-month compliance time would place an 
undue burden on operators that are not able to comply with the AD at a 
``4C'' check because it would necessitate accomplishment of the 
requirements of this AD at a shorter check, thus delaying the 
airplane's return to revenue service. The commenter contends that 
extension of the compliance time to 48 months would not adversely 
affect the safety of airplanes subject to this AD, especially since 
airplanes that will not complete a ``4C'' check cycle by the 36 month 
compliance time are the newest, lowest-time, airplanes.
    The FAA does not concur with the commenter's request to extend the 
compliance time for the actions specified in paragraph (a) of this AD. 
As stated in the preamble of the proposed rule, in developing an 
appropriate compliance time for this AD, the FAA considered not only 
the manufacturer's recommendation, but the degree of urgency associated 
with addressing the subject unsafe condition and the availability of 
required parts. With regard to the commenter's contention that an 
extension of the compliance time would not adversely affect safety, the 
FAA finds that the relative newness of the airplane or a low number of 
flight hours may have no effect on how the torque limiter operates in 
service. In light of all of these factors, the FAA finds a 36-month 
compliance time for initiating the required actions to be warranted, in 
that it represents an appropriate interval of time allowable for 
affected airplanes to continue to operate without compromising safety, 
and wherein an ample number of required parts will be available for the 
modification of the U.S. fleet. No change to the final rule is 
necessary in this regard.

Request To Allow Installation of Unmodified Transmissions

    One commenter requests that the FAA revise paragraph (b) of the 
proposed rule to allow installation of unmodified transmission 
assemblies for the trailing edge flaps for up to 18 months after the 
effective date of this AD. [Paragraph (b) of the proposal reads, ``As 
of the effective date of this AD, no person shall install on any 
airplane, a trailing edge flap transmission assembly, unless it has 
been modified in accordance with Boeing Service Bulletin 757-27A0127, 
Revision 1, dated September 2, 1999.''] The commenter states that the 
proposed paragraph (b) seems ``unnecessarily restrictive,'' and that 
allowing installation of unmodified transmission assemblies for up to 
18 months after the effective date of the AD would provide needed 
flexibility to operators until an ample supply of torque brake retrofit 
kits and seed units is available.
    The FAA does not concur with the commenter's request. The FAA does 
not consider it to be in the interest of safety to allow installation 
of deficient transmission assemblies after the effective date of this 
AD. The FAA finds that the manufacturer's coordination with operators 
during preparation of the service bulletin, coupled with the time 
required for the rulemaking process (including the comment period 
following issuance of the proposed rule), has provided adequate time 
for operators to be able to install only modified transmissions (or new 
transmissions that incorporate the new torque limiter) after the 
effective date of this AD. As noted above, the FAA has been assured by 
the manufacturer that an ample number of required parts will be 
available for modification of the U.S. fleet. Therefore, 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.

[[Page 10695]]

Cost Impact

    There are approximately 796 Model 757 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 500 
airplanes of U.S. registry will be affected by this AD, that it will 
take approximately 32 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 $85,104 per airplane. Based on 
these figures, the cost impact of the AD on U.S. operators is estimated 
to be $43,512,000, or $87,024 per airplane.
    The cost impact figure discussed above is 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 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

    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:

2000-04-18  Boeing: Amendment 39-11601. Docket 98-NM-354-AD.

    Applicability: Model 757 series airplanes, as listed in Boeing 
Service Bulletin 757-27A0127, Revision 1, dated September 2, 1999; 
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 damage to the flap system, adjacent system, or 
structural components; and excessive skew of the trailing edge flap; 
which could result in reduced controllability of the airplane; 
accomplish the following:

Replacement

    (a) Within 36 months after the effective date of this AD, 
replace the transmission assemblies for the trailing edge flaps with 
transmission assemblies modified in accordance with Boeing Service 
Bulletin 757-27A0127, Revision 1, dated September 2, 1999; or with 
new transmission assemblies that incorporate newly designed torque 
limiters; in accordance with the service bulletin.


    Note 2: Replacements accomplished in accordance with Boeing 
Alert Service Bulletin 757-27A0127, dated September 10, 1998, are 
considered acceptable for compliance with paragraph (a) of this AD.

Spares

    (b) As of the effective date of this AD, no person shall install 
on any airplane, a trailing edge flap transmission assembly, unless 
it has been modified in accordance with this AD, or, in the case of 
a new transmission assembly, unless it incorporates a newly designed 
torque limiter.

Alternative Methods of Compliance

    (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 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

Special Flight Permits

    (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.

Incorporation by Reference

    (e) The actions shall be done in accordance with Boeing Service 
Bulletin 757-27A0127, Revision 1, dated September 2, 1999. 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. 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 April 4, 2000.

    Issued in Renton, Washington, on February 22, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-4567 Filed 2-28-00; 8:45 am]
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