[Federal Register Volume 64, Number 201 (Tuesday, October 19, 1999)]
[Proposed Rules]
[Pages 56279-56281]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-27274]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-354-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 757 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Boeing Model 757 series 
airplanes. This proposal would require replacement of transmission 
assemblies for the trailing edge flaps with modified transmission 
assemblies. This proposal is prompted by reports of broken bolts that 
attach the transmission assemblies for the trailing edge flaps. The 
actions specified by the proposed 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: Comments must be received by December 3, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-354-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays.
    The service information referenced in the proposed rule may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

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:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by

[[Page 56280]]

interested persons. A report summarizing each FAA-public contact 
concerned with the substance of this proposal will be filed in the 
Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 98-NM-354-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
Docket No. 98-NM-354-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received reports indicating that certain bolts that 
attach the transmission assemblies for the trailing edge flaps have 
broken in service. Analysis has shown that the bolts broke because the 
torque limiters on the subject trailing edge flap transmissions did not 
``lock out'' at their designated load limits. Tests have shown that the 
torque limiter may ``lock out'' at loads higher than the designed 
maximum limits. If the torque limiter fails to ``lock out'' at the 
designated maximum limits, damage to the flap system, adjacent system, 
or structural components can occur. Additionally, if the torque limiter 
fails to ``lock out,'' a skewed flap condition may not be limited to 
safe levels. This condition, if not corrected, could result in reduced 
controllability of the airplane.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 757-
27A0127, Revision 1, dated September 2, 1999, which describes 
procedures for replacement of transmission assemblies for the trailing 
edge flaps with modified transmission assemblies. 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. 
Accomplishment of the actions specified in the service bulletin is 
intended to adequately address the identified unsafe condition.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require accomplishment of the actions specified in 
the service bulletin described previously, except as discussed below.

Differences Between Proposed Rule and Service Bulletin

    Operators should note that this proposed AD would require 
replacement of the existing transmission assemblies with modified parts 
within 36 months after the effective date of this AD. The service 
bulletin recommends that this action should be accomplished, ``during 
the next scheduled flap transmission overhaul when materials are 
available.'' In developing an appropriate compliance time for this 
proposed action, the FAA considered not only the degree of urgency 
associated with addressing the subject unsafe condition, but the 
availability of required parts. The FAA has determined that 36 months 
represents an appropriate interval of time allowable wherein an ample 
number of required parts will be available for modification of the U.S. 
fleet within the proposed compliance period. The FAA also finds that 
such a compliance time will not adversely affect the safety of the 
affected airplanes.

Cost Impact

    There are approximately 796 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 500 airplanes of U.S. registry 
would be affected by this proposed AD, that it would take approximately 
32 work hours per airplane to accomplish the proposed replacement, and 
that the average labor rate is $60 per work hour. Required parts would 
cost approximately $85,104 per airplane. Based on these figures, the 
cost impact of the proposed 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 proposed 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 proposed herein would 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, 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 copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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:

Boeing: 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;

[[Page 56281]]

and excessive skew of the trailing edge flap; which could result in 
reduced controllability of the airplane; accomplish the following:
    (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.

    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.

    (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 Boeing Service Bulletin 757-
27A0127, Revision 1, dated September 2, 1999.

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.

    Issued in Renton, Washington, on October 13, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-27274 Filed 10-18-99; 8:45 am]
BILLING CODE 4910-13-P