[Federal Register Volume 66, Number 93 (Monday, May 14, 2001)]
[Proposed Rules]
[Pages 24304-24306]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-12008]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-350-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747 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 747 series 
airplanes. This proposal would require an inspection of the flap drive 
transmission of the trailing edge flaps at positions 2 and 7 to 
determine if a wound-spring torque brake is installed, and corrective 
action, if necessary. This action is necessary to prevent damage to the 
flap system, adjacent systems, or structural components; or excessive 
skew of the trailing edge flap, which could result in flap asymmetry 
and consequent reduced controllability of the airplane. This action is 
intended to address the identified unsafe condition.

DATES: Comments must be received by June 28, 2001.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2000-NM-350-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. Comments may be submitted via fax to (425) 227-1232. 
Comments may also be sent via the Internet using the following address: 
<a href="/cdn-cgi/l/email-protection#0e37236f606323607e7c636d6163636b607a4e686f6f20696178"><span class="__cf_email__" data-cfemail="724b5f131c1f5f1c02001f111d1f1f171c06321413135c151d04">[email protected]</span></a>. Comments sent via fax or the Internet must 
contain ``Docket No. 2000-NM-350-AD'' in the subject line and need not 
be submitted in triplicate. Comments sent via the Internet as attached 
electronic files must be formatted in Microsoft Word 97 for Windows or 
ASCII text.
    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: Barbara Mudrovich, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft 
Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-
4056; telephone (425) 227-2983; 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 action may be changed in 
light of the comments received.
    Submit comments using the following format:
    <bullet> Organize comments issue-by-issue. For example, discuss a 
request to change the compliance time and a request to change the 
service bulletin reference as two separate issues.
    <bullet> For each issue, state what specific change to the proposed 
AD is being requested.
    <bullet> Include justification (e.g., reasons or data) for each 
request.
    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 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 action must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 2000-NM-350-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. 2000-NM-350-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received a report that, during overhaul of certain 
torque brakes of the trailing edge flap transmissions on certain Boeing 
Model 747 series airplanes, the brakes did not lock out at the intended 
torque levels. This has been attributed to the actual lock-out torque 
being higher than the design levels. If the torque brake fails to limit 
torque out of the transmission during a flap jam condition, the 
resulting force could cause the transmission mounts to fail. Such 
failure of a transmission mount on a transmission with a no-back brake 
could push the flap into the wing, which could result in a full flap 
asymmetry. These conditions could cause damage to the flap system, 
adjacent systems, or structural components; or excessive skew of the 
trailing edge flap, and which could result in flap asymmetry and 
consequent reduced controllability of the airplane.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 747-27-
2374, dated November 18, 1999, which describes procedures for 
inspection of certain flap drive transmissions of the trailing edge 
flaps at positions 2 and 7 to determine if a wound-spring torque brake 
is installed, and corrective action, if necessary. The corrective 
action includes, but is not limited to, replacement of the flap drive 
transmission with a new, improved transmission; and rework or 
replacement of the torque brake assembly with a new, improved assembly, 
if a wound-spring torque brake is installed.
    The service bulletin references MOOG Service Bulletin 544666-27-16, 
dated November 1, 1999, as the source of service information for 
accomplishment of rework of the torque brake. 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 This Proposed AD and the Service Bulletin

    Although the service bulletin recommends doing the inspection at 
the earliest convenient maintenance opportunity, the FAA has determined 
that this compliance time may not

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ensure that the identified unsafe condition is addressed in a timely 
manner. In developing an appropriate compliance time for this proposed 
AD, the FAA considered not only the manufacturer's recommendation, but 
the degree of urgency associated with addressing the subject unsafe 
condition, the average utilization of the affected fleet, and the time 
necessary to perform the proposed AD. In light of all of these factors, 
the FAA finds a compliance time of 6,000 flight hours after the 
effective date of this AD to be warranted, in that it represents an 
appropriate interval of time allowable for affected airplanes to 
continue to operate without compromising safety.
    The service bulletin also recommends replacement of the flap drive 
transmission and/or torque brake of the trailing edge flap transmission 
at positions 2, 4, 5, and 7. The FAA has determined that an unsafe 
condition exists at positions 2 and 7 only. This determination was made 
from a probability assessment indicating that positions 4 and 5 do not 
warrant mandatory action because the likelihood of failure of a torque 
brake to limit torque out of the transmission during a flap jam 
condition at these positions is extremely remote. Additionally, full 
flap asymmetry is not likely to occur at positions 4 and 5. Therefore, 
this proposed AD is applicable to positions 2 and 7 only.

Cost Impact

    There are approximately 1,181 airplanes of the affected design in 
the worldwide fleet. The FAA estimates that 263 airplanes of U.S. 
registry would be affected by this proposed AD.
    It would take approximately 1 work hour per airplane to accomplish 
the inspection, at an average labor rate of $60 per work hour. Based on 
these figures, the cost impact of the inspection proposed by this AD on 
U.S. operators is estimated to be $15,780, or $60 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 proposed 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.

Regulatory Impact

    The regulations proposed herein would 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 proposal would not have federalism implications 
under Executive Order 13132.
    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 2000-NM-350-AD.

    Applicability: Model 747 series airplanes, as listed in Boeing 
Service Bulletin 747-27-2374, dated November 18, 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 systems, or 
structural components; or excessive skew of the trailing edge flap; 
which could result in flap asymmetry and consequent reduced 
controllability of the airplane, accomplish the following:

Part Verification/Replacement/Modification

    (a) Within 6,000 flight hours after the effective date of this 
AD: Inspect the flap drive transmission of the trailing edge flaps 
at positions 2 and 7 to determine if a wound-spring torque brake is 
installed in the transmission, by verifying the transmission part 
number, per Boeing Service Bulletin 747-27-2374, dated November 18, 
1999. Then do the actions specified in paragraphs (a)(1), (a)(2), 
(a)(3), and (a)(4) of this AD, as applicable.
    (1) If the part number of the flap drive transmission shows that 
no wound-spring torque brake is installed, no further action is 
required by this AD.
    (2) If the part number of the flap drive transmission shows that 
a wound-spring torque brake may be installed, before further flight, 
inspect the part number of the torque brake to verify whether it is 
a wound-spring torque brake, per the Accomplishment Instructions of 
the service bulletin.
    (i) If the part number of the torque brake shows that it is not 
a wound-spring torque brake, no further action is required by this 
AD.
    (ii) If the part number of the torque brake shows that it is a 
wound-spring torque brake, before further flight, rework the torque 
brake or replace the torque brake with a new, improved brake, as 
applicable; per the Accomplishment Instructions of the service 
bulletin.

Spares

    (b) As of the effective date of this AD, no person shall install 
on any airplane any transmission or torque brake assembly identified 
in the ``Existing Part Number'' column of Paragraph 2.E. of Boeing 
Service Bulletin 747-27-2374, dated November 18, 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. 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.

Special Flight Permit

    (d) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199

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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 May 8, 2001.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 01-12008 Filed 5-11-01; 8:45 am]
BILLING CODE 4910-13-U


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